At the End of the River: The Coorong and Lower Lakes 1921511664, 9781921511660

Citation preview

At the End of the River The Coorong and Lower Lakes

At the End of the River The Coorong and Lower Lakes

David Cleland Paton

Copyright © 2010 with David Paton for the main text and with the individual authors for the vignettes. Copyright © - photographs held by individual photographers for all photos in this volume. All rights reserved. Except for any fair dealing permitted under the Copyright Act, no part of this book may be reproduced by any means without prior permission. Inquiries should be made to the publisher.

National Library of Australia Cataloguing-in-Publication entry   Author: Paton, D. C.   Title: At the end of the river : the Coorong and lower lakes / David Cleland. Paton   ISBN: 9781921511660   Subjects: Ecology--South Australia--Coorong, The. Lagoons--South Australia--Coorong, The. Wetlands--Murray River (N.S.W.-S. Aust.) Nature conservation--South Australia--Coorong, The. Coorong, The (S. Aust.)   Dewey Number:     333.780994233

Published by ATF Press

An imprint of the Australasian Theological Forum Ltd PO BOX 504 Hindmarsh SA 5007 ABN 90 116 359 963 www.atfpress.com

Cover Photograph: Stavros Pippos, www.stavrospippos.com Design consultant: Graeme Cogdell, Cogdell Design & Fine Art Layout: Fiona Paton, Lydia Paton, Astrid Sengkey

Contents Vignettes

vii

Figures

viii

Tables

ix

Foreword

xi

CHAPteR 1

An Ecologist’s Perspective

CHAPteR 2

The Coorong Ocean Beach: A high energy coastline

CHAPteR 3

Younghusband Peninsula: From discovery and exploitation to reservation

CHAPteR 4

The Ecology of Younghusband Peninsula

CHAPteR 5

The Coorong Lagoons: Dynamic but hydrologically challenged

CHAPteR 6

The Coorong Lagoons: Early natural history and use of natural resources

CHAPteR 7

The Coorong Lagoons: Biotic responses to a changed hydrology

CHAPteR 8

The Coorong Lagoons: A critical refuge for waterbirds

CHAPteR 9

The Lower Lakes: Wetlands that complement the Coorong

CHAPteR 10

The Future of the Coorong and Lower Lakes

Appendix Abbreviations

Common and scientific names

13 31

51 79 109

127

147 185

213

232

234

Acknowledgements About the Author Cover Photographer Index

1

235 238 239

240

COntents

v

Banded Stilt flock

vi

Paul Wainwright

Vignettes Colin Thiele and the legacy of Mr Percival

Fiona Paton

Mulloway

Greg Ferguson

14

Fishing the Coorong beach

Alastair Wood

15

Goolwa Cockles

Coby Mathews

17

Chinamans Well

Penny Paton

40

Cantara Homestead

David Paton

42

The unique Malleefowl

Fiona Paton

45

A tale of orchids, rabbits and RHD

Peter Bird, Greg Mutze & David Peacock

Coorong wombats

Greg Mutze

The song of Rufous Bristlebirds

Daniel Rogers

What are Ramsar wetlands?

Penny Paton

80

Pelicans in the Coorong

Penny Paton

114

The breeding biology of pelicans

Penny Paton

119

Polychaete worms in the Coorong

Alec Rolston

128

Chironomids in the southern Coorong

Mike Kokkinn

134

Brine Shrimp in the Coorong

Mike Geddes

East Asian-Australasian Flyway

David Andrew, DEWHA

Recollections of living at Yalkuri

Richard Harvey

Water quality in the Lower Lakes

Kane Aldridge & Justin Brookes



2

66

67 73

144 159

189

Freshwater mussels in the Lower Lakes

Keith Walker

Threatened fishes on the brink of local extinction

Scotte Wedderburn

Musk Ducks

Kevin McCracken

What are acid sulfate soils?

Russell Seaman

The tubeworm of the Lower Lakes

Alec Rolston

Managing acid sulfate soils in the Lower Lakes

Russell Seaman

Going against the flow

Keith Walker

The Coorong and sea level rise

Andrew Short

191

193 194 196 200 202 209 226 227

vignettes

vii

Figures CHAPteR 1

1.1 The Murray-Darling Basin

CHAPteR 2

2.1 Vehicle tracks across the ocean beach

CHAPteR 4

4.1 Silvereye movements, south-eastern South Australia

1 20 62 72

4.2 Sonogram of the call of a pair of Rufous Bristlebirds

CHAPteR 5

82

5.1 Map of the Coorong and Lower Lakes 5.2 Map of the Lower Lakes

83 86

5.3 Seasonal changes in salinity along the Coorong from Dec 1999 - Sep 2000 5.4 Predicted River flows reaching the Murray Mouth since 1901 5.5 Map of the Barrages

90

91 92

5.6 Predicted River flows reaching the Murray Mouth over the last 20 years

93

5.7 Changes in salinity along the Coorong for January from 2001 to 2009 95

5.8 Seasonal patterns of River flows reaching the Murray Mouth

CHAPteR 7

130

7.1 Salinity tolerances of selected aquatic organisms in the Coorong 7.2 Number of macro-invertebrate taxa found along the Coorong 7.3 Changes in the number of fish species along the Coorong 7.4 Loss of Ruppia tuberosa from the South Lagoon 7.5 Winter salinities in the southern Coorong

132

133

138

139

7.6 Changes in abundances of seeds and turions for Ruppia tuberosa in the South Lagoon 140 7.7 Changes in the abundances of chironomids in the South Lagoon 7.8 Changes in the abundances of hardyhead fish in the South Lagoon

CHAPteR 8

8.1a Foraging depths of small waders in the Coorong

149

8.1b Foraging depths of large waders in the Coorong

150

142 142

8.2 Seasonal changes to the abundances of different groups of birds in the South Lagoon during 1984-85

158

8.3 Map showing seven Coorong regions

164

8.4 Distribution of waterbird species in the seven Coorong regions

165

8.5 Numbers of waterbirds counted along the Coorong in January 2000-2009

viii

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d Lo w e R L A k e s

166



8.6 Distribution of birds along the Coorong in January 2000-2009



169



b Cormorants



c Waterfowl



d Resident waders



e Migratory waders



168

a Fish-eating species

169 170 171

8.7 Changes in abundances of birds in the South Lagoon for Jan 1985 and Jan 2000-2009 172



a Fish-eating birds



b Waterfowl



c Small waders

174



d Large waders

176



174

8.8 Changes in abundances of small waders using different regions of the Coorong in 1987 and over 2000-2009

179

C H A P TE R 9

9.1 Map of the Lower Lakes

C H A P TE R 1 0

10.1 Elevated salinities in the South Lagoon since 2007 now exclude key biota



10.2 Predicted changes in salinity following different management actions

199 219

222

Tables C H A P TE R 4

4.1 Prominent plants of Younghusband Peninsula



4.2 Abundance of terrestrial birds and foraging niches in the Coorong



4.3 Seeds found in scats of frugivorous birds and in seed traps



4.4 Frost damage to fleshy-fruited plants

C H A P TE R 8

8.1 Waterbird species of the Coorong



8.2 Prominent shorebirds recorded in the Coorong in the 1980s



8.3 Seasonal abundances of bird species in the South Lagoon for 1984-85



8.4 Changes in abundances of selected waterbirds between 2000-2006 and 2007-2009



8.5 Bird species with more than 1% of their flyway population using the Coorong



8.6 Numbers of waterbirds in the Coorong during 2000-2006 and 2007-2009

C H A P TE R 9

9.1 Waterbirds counted in the Lower Lakes, summer 2009

56 57

58

69 148 156 157 178

180 181

204

ta b l e s a n d f i g u r e s

ix

Coorong and Lower Lakes x

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d Lo w e r L a k e s

Foreword

E

uroPean settleMent has brought

many benefits to Australia but few for the Coorong. During the first half of last century, the South East was drained and the Barrages were built. With the Barrages in place, irrigation communities and cities like Adelaide, Whyalla, Port Augusta and Port Pirie could expand and they did. Late in October 2002, this era of expansion came to a screeching halt. Dredges were brought in to keep the Mouth of the River Murray open. Seven years later, these dredges are still there. The Coorong that served Australia for millennia is changing – changing rapidly. Australia’s mightiest river system has run out of water. When a river stops flowing, it is clear that it is over-allocated and over-used. All Australians need to know that the end of the River Murray was in strife before this current long dry emerged. For millennia water has flowed into the Coorong from the great Southern Ocean, the South East and the River Murray. Collectively, these three sources have kept her landscape vibrant. The Coorong is one of Australia’s special places. To remain special, she needs water. More than anything else, the Coorong needs a secure water entitlement–one that is as secure as that given to irrigators throughout the MurrayDarling system. Is this too much to ask? I don’t think it is. David Paton is of the same view. How large an entitlement does the Coorong need? To answer this question, one needs first to understand how the Coorong functions and how much water is needed to raise the level of the Lower Lakes to a height that is above sea level. When the level of water in the Lower Lakes is below the sea, the Coorong cannot function–at

Coorong landscape

greg bourne

least not function in the way that we have come to know and love. The Coorong, more than ever before, needs a drink. In the process of gaining this knowledge and planning her future, one also needs to understand the beauty of the Coorong as a place to be nurtured. Beautifully illustrated and written by one of the Coorong’s most knowledgeable ecologists, ‘At the End of the River’ is a must read for any person interested in the future of the Coorong. It is an essential read for those responsible for making the decisions that will determine her future.

P�������� M��� Y���� D�������, T�� E���������� I��������, T�� U��������� �� A�������

fOReWORD

xi

Looking south-east down the Coorong, March 1987 Department for Environment and Heritage

12

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

ChApteR 1

An Ecologist’s Perspective

A

river murray is a wetland, a wetland of international significance. We know this area as the Coorong and Lower Lakes, the last bodies of water that the Murray traverses before reaching the Southern Ocean. Our connection to this place varies. For those who live around its shores, work with it and depend on it, there is a love of place, a sense of belonging. For some, the connection is all embracing, a setting for stories about traditions and place; even modern European culture connects to the place through a boy, Storm-Boy1 and a pelican, Mr Percival. t tHe enD of tHe

Sadly for most Australians there is no connection – at best it is simply a distant place out of sight, out of mind. This may seem harsh but how else could one describe a nation that is unable to provide an environmental flow, let alone an adequate environmental flow, to the wetlands of the Murray-Darling Basin, instead allocating the River’s water for human uses and then some. This allocation may have been done without malice or greed, but the inability of the governments of Australia to solve this fundamental flaw of over-allocation in a timely manner is indictable. The Coorong and Lower Lakes, the terminal wetlands of the Murray-Darling Basin, will be the first casualties. However, it is not too late to make a difference – but as every year passes without delivery of environmental flows then the opportunities to secure these wetlands diminish. As such, these wetlands are the barometer for how well Australia and Australians learn to live sustainably in a landscape with a harsh climate and poor soils. The future of these wetlands will tell the story.

Although the two are intricately linked, this book is primarily about the Coorong and not the Lower Lakes. The Coorong is unique amongst the wetlands of the Murray-Darling Basin (Fig. 1.1), being the only wetland where the salinity of the water naturally exceeds that of sea water. All of the other wetlands within the basin (including the Lakes) are fresh, at worst brackish at times, so ecologically the Coorong is very different. The name Coorong is derived from the aboriginal name for the region Kurangh, meaning long

F

1.1 The Murray-Darling Basin

-

An eCoLogist’s peRspeCtive

1

Colin Thiele and the legacy of Mr Percival

F

irst published in 1963 and made into a film in 1976, Storm-Boy is a much loved Australian children’s story by Colin Thiele.1 It is the tale of a ten year old boy who lives with his father in the Coorong, spending his time roaming the ocean beach and exploring the wetlands. One day he comes across three baby pelicans abandoned when their parents were shot and their nest destroyed by duck-shooters. StormBoy saves the pelicans and forms a strong bond with one of them in particular, which he names Mr Percival. Even when the pelicans grow up and are released, Mr Percival returns to become Storm-Boy’s ever faithful companion, ‘If Storm-Boy went fishing or rowing on the Coorong, Mr Percival cruised joyously round him with his neck bent back and his chest thrust forward like a dragonship sailing calmly in a sea of air.’ Mr Percival learns to help Storm-Boy’s father to fish, plays a part in rescuing the crew of a shipwrecked boat and warns the ducks when the duck-shooters are approaching. Unfortunately, the duck-shooters become frustrated with Mr Percival warning the ducks and the story takes a tragic turn. Colin Thiele’s descriptions of the Coorong landscape and the birds are a fitting frame for the remarkable storyline, ‘In the early morning the tall birds stood up and clapped and cheered the rising sun. Everywhere there was the sound of bathing – a happy splashing and sousing and swishing. It sounded as if the water had been turned into a bathroom 5 miles long, with thousands of busy fellows gargling and blowing bubbles together.’ With the death of Colin Thiele - author, conservationist and educator - the Coorong lost one of its greatest advocates and publicists. In his inimitable way he passed on his love for the area, its wildness and uniqueness. In an interview shortly before his death in 2006, he said: ‘For God’s sake we need to realise what a treasure we have here…Don’t damage it. Let us hand it on to our children, and our children’s children’s children, down the centuries.’2

By Fiona Paton 1. Colin Thiele, Storm-Boy (Adelaide: Rigby Publishers, 1963). 2. Keith Conlon, ‘Colin Thiele’s Storm-Boy’ Accessed 5 September 2009.

2

Australian Pelican

Arthur Grosset

narrow neck, presumably referring to the long and relatively narrow lagoon that stretches like an appendix off the Murray for 110 kilometres to the south-east. Salinities gradually increase along the Coorong with distance from the Murray Mouth — a reverse estuary. For a typical river system, the opposite occurs — salinities are highest at the mouth where river water meets the sea and then decrease upstream. Prior to the building of the Barrages, a large and typical estuary existed between the Murray Mouth and Lower Lakes. However, for the last seventy years it has been restricted to just that area between the Barrages and the Murray Mouth (in the northern Coorong). In the 1930s, some eighty percent of the water entering the River Murray went out to sea, by the 1990s this was reduced to twenty-seven percent, while for the first eight years of the twenty-first century, only a meagre four percent reached the sea. In addition the drainage of most of the swamps in the South East of South Australia has led to both increases and decreases in the quantities of freshwater flows into the southern Coorong at Salt Creek, and also the loss of countless freshwater swamps. These are just some of the changes that have taken place in the region since European colonisation. So what were the wetlands of the Coorong and Lower Lakes like, what should they be like, and what will they look like in the future? One

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Students monitoring the salinity and turbidity of water of the great difficulties in understanding these wetlands and managing them into the future is having an adequate historical perspective against which changes can be judged. The recent concerns about the Coorong dying echo nearly fifty years of concern about high salinities and ecological decline in the South Lagoon. However, measurements going as far back as the early 1960s show that, although salinities varied from one year to the next in the South Lagoon, they have not changed substantially during the last forty years of the twentieth century at least. In fact early descriptions of the Coorong region, dating back to the 1880s, suggest that these salinities were probably within the typical range for this wetland. However, salinities have increased dramatically in the first eight years of the twenty-first century, and particularly over the last 4-5 years, with significant ecological consequences.

David Paton

Various solutions have been proposed to counter the extremely high salinities of the southern Coorong including: pumping sea water from the Southern Ocean over Younghusband Peninsula and into the South Lagoon to dilute the Coorong’s salty water; cutting a channel through Younghusband Peninsula to produce a connection to the sea at the bottom end of the South Lagoon to flush the salt out; pumping the highly saline water out of the South Lagoon over Younghusband Peninsula and into the Southern Ocean; dredging the narrow channels between the North and South Lagoons to increase longitudinal mixing of water within the Coorong; and increasing freshwater flows from the South East into the South Lagoon via Salt Creek. However, none of these provides the same outcome as re-instating River flows to the Murray Mouth.

aN Ec o l o g i s t ’ s p e r s p e c t i v e

3

An old fence-line jutting out into the Coorong For all of the above proposals there is a sense of déjà vu. For example, Noye raised concerns about apparent rising salinities in the South Lagoon during the late 1960s and early 1970s, and outlined and discussed a number of engineering and management solutions.2 These included the building of various barrages or regulators across different parts of the northern Coorong to increase the influx of fresh water to the Coorong and to reduce the flow of water out of the southern Coorong during late spring and summer.3 These and other suggestions, such as digging a channel across Younghusband Peninsula to connect the southern Coorong to the sea,4 and McCourt’s suggestion of digging a channel between Lake Albert and the Coorong,5 were largely dismissed because of other unwanted

Lydia Paton

ecological consequences. Noye’s preference, however, was to restore freshwater flows from the South East to the southern Coorong. Noye’s view of the deterioration of the southern Coorong was largely based on the stench of rotting weed along the eastern shores of the South Lagoon in late summer, attributed to higher salinities (no more than three times the salinity of sea water at the time) killing the aquatic plants (Ruppia tuberosa)* in the South Lagoon. These were subsequently washed ashore or left out of water to rot and smell, a sufficient stench to deter any passing traveller on the nearby Princes Highway from stopping and exploring the region. But this almost certainly occurred in the 1850s as Cadell, who attempted

* Common names of plants and animals are used in the text unless there is no accepted common name. For a full list of common and scientific names see Appendix.

4

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

to navigate the Coorong in the steamer Albury in 1856, noted: ‘In emerging from the Needles passage you come upon a mud flat of two miles long, and nauseous from the effluvia of putrid matter.’6 Other reports and books about the Coorong record similar occurrences since the 1850s and into the 1990s, so perhaps the process of plant material rotting around the shores of the southern Coorong is not atypical. This may reflect the productive nature of the wetland rather than its demise. Securing an accurate historical perspective is often difficult because we have a tendency to remember the exceptional periods, the times of plenty and not the average or usual conditions. Thus, many people recall the Coorong during periods when the waters teemed with fish and the sky was black with birds but not the leaner times. As individuals, we have only our own benchmarks with which to measure change, and trying to compare across generations is hard.

View from Parnka Point headland

Tom Bradley

“the waters teemed with fish and the sky was black with birds...” This book is my attempt to describe the ecology of the Coorong, to document its changing ecological character, so that future generations will have a sense of what the place was like at the end of the twentieth century and moving into the twenty-first century. My connection to the Coorong comes from monitoring the birds and their food resources in the region and so my views are biased towards birds, and to the changes of the last decade or so. This book will reflect this, but I have been visiting the Coorong with ecological intent since 1981, particularly the southern Coorong, not just documenting components of the aquatic systems but also the terrestrial systems. With that experience, I would like to think I have an intimate knowledge of

Low water levels near Parnka Point, January 2007 David Mariuz

aN Ec o l o g i s t ’ s p e r s p e c t i v e

5

6

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Sandpipers in flight this system, but my views will differ from others and I will try to put these in context and in some historical perspective. The book has other purposes than just setting a late twentieth century benchmark for the Coorong’s ecological condition. Importantly, I want to dismiss any notion that this is a dying wetland and thus one not worth preserving and managing for its natural assets. The Coorong and the Lower Lakes have changed dramatically in the last few years, but even in their current degraded state they remain the standout wetland system of the MurrayDarling Basin, still comfortably meeting the criteria of a Wetland of International Importance under the Ramsar Convention, doubly so in droughts. They are neither dead nor dying, but they are changing and deteriorating. Painting pictures that these

niCHoLas BirKs

systems are dying and will soon be dead may capture a media headline but such headlines sensationalise the situation and misrepresent the case, and they do nothing to help protect and restore the Basin’s premier wetland system. Why would those living hundreds, if not thousands, of kilometres away in the states of Victoria, New South Wales and Queensland see any value in ‘gifting’ water for a dying, and soon to be dead, Coorong? The messages and headlines need to change. In reality, the Coorong and the Lower Lakes are relatively robust and resilient and their former ecological character is still recoverable. We should not lose sight of this. The issues facing the Coorong and Lower Lakes today have been constantly in the media for nearly two years now and there are numerous opinions about who to blame, as the politicians make promises and point fingers, and as different community groups lobby for their preferred solutions. These adversarial approaches do little

An eCoLogist’s peRspeCtive

7

View of bay north of Parnka Point, early summer to suggest a commitment to changing how we perceive, exploit and manage the River. Instead of talking about what needs to be done, we need to do it.

“fixing the ecology of the River commences with the last wetland...” Ultimately, the disconnection of the River Murray from its wetlands, and the degradation of the latter, are due primarily to a failure, decades ago, to provide them with an adequate allocation of water. Hindsight is golden, but we should not dwell on the past other than to learn

8

Lydia Paton

from our mistakes. The issue now is how to reconfigure the River, its wetlands and the water resources, after we have all become accustomed to exploiting the River beyond its capacity. We should be focusing on this task, and the future management of the River and the Basin. The local communities at the end of the River have already endured significant changes to their businesses, livelihoods and life-styles at short notice, as the lower reaches of the River Murray have collapsed. However, fixing the ecology of the River commences with the last wetland — the Coorong and Lower Lakes. The water that is provided to meet the needs of these final wetlands can also provide ecological benefits en route along the River, helping to sustain other wetlands upstream, with only small additional allocations. The water that remains after these environmental allocations, taking into account

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

transmission and evaporative losses, becomes the quantity of water available for human use. For me the Coorong is a lot more than its waterways. The dynamic coastal dune systems of Younghusband Peninsula, that separate the Coorong waters from the Southern Ocean, provide an equally compelling case of overexploitation by early European endeavours, followed by abandonment and partial recovery. The original mallee, sheoak and native grassland systems along the mainland side of the Coorong lagoon have not fared as well and have all but vanished, most of it cleared and developed for agriculture. The Coorong region also featured prominently in the early development and settlement of the State, particularly in early interstate communication and transport through the nineteenth century. In the twentieth century, the area chronicled changing attitudes to the management of wildlife and natural assets, from early legislative protection

Australian Pelican

for waterbirds, through a history of commercial to recreational hunting of waterfowl, from no protection to bag limits, from specially gazetted game reserves to no hunting; seasonal beach closures to protect Hooded Plovers; and setting aside land for restoration to prevent soil erosion or to protect wildlife. Much of that history, of development, followed by concern and subsequent protection for the natural system, shows that previous generations cared about the place. There are many people I need to thank and acknowledge for this book. My sincere thanks to my immediate family — Penny, Lydia and Fiona— for editing and massaging the text into shape, to the colleagues who have influenced my views and understanding of the region, to the many who have contributed sections to the book, adding their detail or perspective, and to those who have provided images to bring the book alive. The book consists of a series of chapters that roughly follow a transect that commences on the

Paul Wainwright

aN Ec o l o g i s t ’ s p e r s p e c t i v e

9

ocean beach and traverses the sand-dunes and coastal vegetation of Younghusband Peninsula before exploring the ecology of the Coorong lagoons and Lower Lakes. In addition to being an introduction to the ecology of the area, to making some of the science more readily accessible and to illustrating how science can influence management actions, the book is also an invitation to explore the system. Ultimately, the book is about growing the awareness that there are significant impacts of failing to live sustainably. If environmental flows are not re-instated, one of the casualties could be the Coorong and Lower Lakes.

in harmony with the land and waters of this region in a sustainable way. Our concept of sustainability is more about sustaining economic growth, irrespective of the damage done to the environment that ultimately supports us. We are a nation that plunders the environment for our own benefit and passes the environmental cost of that exploitation on to future generations. We could learn a lot from the traditional owners of this land and water. That they remain largely silent speaks volumes for their discontent. I am, however, eternally grateful that they have allowed me to trespass on both their place and culture – a privilege that I and others have taken for granted and regretfully will never repay.

I have not dwelled on the cultural connections of the traditional owners, the Ngarrindjeri, in this book, largely from respect. They need to tell their stories in their words and I would encourage them to do so. For thousands of years they lived

Waders in flight, Coorong

10

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Paul Wainwright

Australian Pelicans 1.

Colin Thiele, Storm-Boy (Adelaide: Rigby Publishers, 1963).

2.

BJ Noye, ‘Waters of the Coorong lagoons’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 59–79.

3.

John Noye, editor, The Coorong, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975).

4.

HBS Womersley, ‘Plant life in the Coorong lagoons’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 81–8.

5.

Tom McCourt and Hans Mincham, The Coorong and lakes of the Lower Murray (Adelaide: Beachport Branch of the National Trust, 1987).

6.

The Register, 7 June 1856, quoted in John Noye, ‘Water of the Coorong lagoons’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 73–4.

DaviD BLair

An eCoLogist’s peRspeCtive

11

42 Mile Crossing

12

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

David Blair

ChAPteR 2

The Coorong Ocean Beach: A high energy coastline

T

He firsT DesCripTions of THe CoasTline

along the Coorong were provided by Captain Nicolas Baudin, the French explorer who sailed north-west along this section of coastline in the Geographe on 8 April 1802. Baudin’s description translated into English reads: The stretch of coast that we had been following since yesterday consisted entirely of sand dunes which inspired nothing but sadness and regrets. Quite apart from the wretched and unpleasant appearance of this shore, the sea breaks all the way along it with extraordinary force, and the two or three swells that appear before the waves reach the shore indicate that there is a bar which must extend half a mile out to sea.

Lines of breakers along Younghusband Peninsula

The look-out men at the mast-heads and the interested observers who wished to join them reported that in the hinterland, as far as the eye could see, there was nothing but arid sand with no vegetation.1 Later on the same day, Baudin encountered British explorer Matthew Flinders sailing from the west in the Investigator. Both men had commissions from their respective countries to explore and chart the remaining unknown coastline of southern Australia. Younghusband Peninsula’s ocean beach bears the brunt of the prevailing southerly and westerly winds and associated storm events and is a high energy coastline. Continuous lines of waves break off-shore and wash over the intertidal areas

niCHolas Birks

the CooRong oCeAn beACh: A high eneRgy CoAstLine

13

The remains of a car on the ocean beach

Bryan Haywood

of the beach. Waves break along this shore-line throughout the year because of a persistent yearround swell generated by storms in the Southern Ocean, south of the continent.2 The waves are typically about 2m in height, but are higher during storms and windy conditions and lower during calmer periods. During stormy weather the greater wave activity can scour away much of the beach, at times etching into the fore-dunes. In summer, with lower sea levels and less frequent severe conditions, the beach holds more sand and is a little wider. Even in summer, the intertidal areas are likely to experience a high turnover of sand. Although I have never tested this, I am told that if a bucket of coloured beads was buried half a metre below the surface within the intertidal area, by the next day only a few beads (if any)

Mulloway

M

ulloway occur in the Indian and Pacific Oceans between latitudes of 40oS and 40oN including Australia and South Africa. In Australia it occurs around the southern coasts including New South Wales, Victoria, South Australia and Western Australia, but not Tasmania where the water may be too cold. They can live for up to 40 years and can grow to 160cm and 40kg, making them a prized sportfish. Mulloway from the Coorong region are sexually mature at 6-7 years of age, not spawning until at least 81cm in length.

Size, bag and boat limits apply to Mulloway fishing in South Australia. These limits are designed to ensure the longterm sustainability of the fish stocks. Within the Coorong lagoons, fish smaller than 46cm cannot be taken, and there is a maximum daily bag limit of ten fish, of which no more than two can be greater than 75cm. Elsewhere in South Australia, including the ocean beach of Younghusband Peninsula, the fish must be at least 75cm in length, with a personal bag limit of two per person and six per boat with more than three anglers.

The life history of Mulloway is not well known. Mature Mulloway aggregate from November to February to feed and spawn. These aggregations are a feature of this family of fishes, known in the Northern Hemisphere as ‘croakers’, because of the noises they make to communicate with each other. Aggregations are known to occur in two places in South Australia: inside reefs on the far West Coast and adjacent to the Mouth of the Murray River. It is thought that they spawn near the surf zone and that larvae quickly settle to the bottom and seek protected habitat. In the coastal waters off the Murray Mouth, within a few months of being spawned, juveniles less than 5cm swim into nursery habitat such as the Coorong lagoons. Protection of juveniles in good quality nursery habitat is particularly important for Mulloway because they take so many years to mature.

By Greg Ferguson

14

Fisherman, ocean beach

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Tim Thorpe

Fishing the Coorong beach

I

fished at the Murray Mouth for twenty-seven years: such a brief interlude; not even the blink of an eye in the infinite passing of time. But during that tiny moment I saw many changes occur throughout the entire estuary. Were these changes all part of a natural cycle, or were they brought about by the intrusions of man? One wintry afternoon I drove along Goolwa Beach all the way to the Murray Mouth. Heavy surf rolled ashore and made the beach soft. When I arrived, the car was boiling and ragged men at the water’s edge were pulling seaweed and the biggest fish I’d ever seen from a flimsy looking net. It was the late ‘60s; the fish were Mulloway and I was hooked. In a flurry of excitement I bought gear, slung a net together and spent the next few months attempting to learn a strange new art, floundering around in the shorebreak, freezing. Weeks went by with nothing more than the odd tiddler being caught. Frustrated with the net’s sluggishness and its reluctance to draw off into the far breakers and irritated by beach traffic, I’d drive to the edge of the Mouth and gaze across at the other side. Shrouded in surf mist, the Coorong beach and sandhills of Younghusband Peninsula stretched as far as the eye could see; a sombre sight with the dunes looking mysterious in their remoteness and desolation. The beach was deserted, not a beach buggy nor four wheel drive in sight. I went to the pub and listened to the locals tell stories of the far side, the Coorong beach. How old men had rowed down the Coorong to the Treadlight landing where they walked across the Peninsula with rods over their shoulders and fished in deep holes. With the sun hot and the wind blowing over the sandhills, they baited heavy hooks with stale mullet and caught giant Mulloway a few yards offshore. Impatient for success, I decided to make the move. I converted an old sedan, borrowed a dinghy from a friend and went fishing alone along the ninety miles of Coorong beach. In the early days there were plenty of Mulloway in the surf around the Murray Mouth and I could make good catches for eight months of the year. On humid, thundery nights, I could drag my net into the surf and walk backward until it was fully stretched out. I’d stand around in chest deep water holding the leading end and it wouldn’t be long before I felt the thump and tug in the net as fish hit. Other nights, I’d launch the net on one side of a deep hole and stand waist deep as it circled. Each time it came past I’d pull out half a dozen fish, race up the beach and throw them into an esky.

Alastair with his catch

Alastair Wood Collection

Regular freshwater flows kept the estuary healthy. After flowing through the Barrages and the Mouth, they were absorbed by the colder Southern Ocean, fanning out into a myriad of subtle gradients of salinities and temperatures. Mulloway loved these layers of contrast. They would gather in schools to gorge themselves on small fish flushed from the Murray. As the eighties arrived, the freshwater outflows through the Barrages had started to diminish. Year in, year out, too much was being extracted upstream. The Mouth grew shallower and while tidal inflows continued to deliver more sand from the beach, the outflows were not strong enough to remove it. In 1981, the Murray Mouth dried up and I was able to drive from Victor Harbor to the Coorong beach without leaving my vehicle. Later that year the Mouth was revived. A big winter rainfall and a trench dug by machines across the sand spit reopened it. But the revival was only temporary. The River continued to suffer from greatly reduced flows and the Mouth choked with sand. Bird Island grew across the channel. The Coorong suffocated from lack of tidal water from the sea as well as fresh water from the River. Mulloway were no longer plentiful in the surf. There were no more easy hauls and the barren months, when fishing was not commercially attractive, increased.

By Alastair Wood

TTh hee C Co oo orro on ng g o oc ceeaan n bbeeac ach h :– AA hhi g i ghh eenneer rggyy ccooaasst tL i n e

15

Harvesting cockles

Goolwa Cockles

Coby Mathews



Coby Mathews

would still be present. Perhaps more striking examples of the power of this wave-generated energy are the rare events where high tides have engulfed vehicles inadvertently parked on the ocean beach. After being rolled around in waves, the vehicles are then ceremoniously dumped back on the beach and partially buried in sand, by the time low tide and calmer conditions have returned.

16

Substantial quantities of sand are moved along the shore-line of Younghusband Peninsula, with estimates suggesting a net movement of sand of around 180,000-260,000 cubic metres per annum.3 This sand movement is effected by longshore currents. When waves break and come to shore, they suspend sand and that sand is carried on to the shore. If the waves approach the shore-line at an angle then, as they run ashore, they transport the suspended sediments, mainly sand, up the beach at the same angle. The backwash of that wave also carries suspended material. However, the backwash retreats from the beach at right angles. Subsequent waves pick up some of this material and shift it along the beach a little further. As a consequence the sand is moved in a zigzag fashion along the shore. Other currents and eddies establish and operate in the littoral zone and aid in the formation of submerged sandbars and troughs, perhaps 100m or more off the coast within the broad surf zone. The troughs and channels that form are often favoured places for fish, like Mulloway, and are consequently targeted by fishermen. Like most of the coastal processes, these sandbars and troughs are dynamic, changing with the directions and strengths of winds and waves, and even tidal heights.

Fishing and cockling on the ocean beach The ocean beach is a popular surf-fishing beach. Access to the beach is provided by a number of four wheel drive tracks that meander across the dunes of Younghusband Peninsula. All of these access tracks are south of the Coorong lagoons, except for Tea Tree Crossing, seven kilometres south of Salt Creek. Tea Tree Crossing is only open during the summer months, when water levels in the Coorong’s southern lagoon are sufficiently low to allow safe passage, while the other tracks are open throughout the year. Although vehicular access to the ocean beach is limited to four wheel drives, there are a couple of

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Goolwa Cockles

T Cockle fragments, ocean beach

Tom Bradley

two wheel drive alternatives. First, one can park on the eastern side of the dunes and then walk over to the beach. Alternatively at the Granites, twenty kilometres north of Kingston SE, two wheel drive tracks take you almost to the ocean beach. Amateur fishers drive along the ocean beach in four wheel drives until they find a suitable place to fish, often fishing overnight. Most amateurs fish for large Mulloway, which are often caught, and the opportunity of catching these large fish provides a strong stimulus to return. An annual fishing competition, run by the Kingston Lions Club, is held in January and has been running for the past thirty years, providing an added incentive to fish along the ocean beach. The ocean beach is also promoted as a destination for four wheel drive enthusiasts, with the beach drive being more challenging north of Tea Tree Crossing than further south. The only other regular users of the ocean beach are commercial cocklers, who harvest Goolwa Cockles (otherwise known as Pipis) from the wave swash zone at various points along the ocean beach when they are in season. The cockle industry is regulated with respect to harvest quantities and methods, and forms part of the region’s sustainable fishing industry, which includes fishermen taking fish from the Coorong and Lakes. Cockle harvesting involves the disturbance of the sand in the wave swash zone. A cockler uses his feet to dislodge the cockles that are buried just below the sand’s surface and then, as waves

he Goolwa Cockle or Pipi, as it is commonly called in the eastern states, is found largely from Goolwa in South Australia to Fraser Island in Queensland, with a few additional areas outside this range (including Eyre Peninsula, South Australia). A large percentage of the Australian biomass of Goolwa Cockles is found within the Coorong region of South Australia, on the ocean beaches of the two peninsulas split by the mouth of the River Murray, the Sir Richard and Younghusband Peninsulas. The Goolwa Cockle can be found within the ‘swash-zone’ of high energy surf beaches, which is the area of beach that is intermittently wet with surf. As the tide moves, this species migrates in and out with each incoming and outgoing tide, remaining within the ‘swash-zone’ environment. Small size classes of cockles are generally found higher up the beach in the shallow swash, compared to the larger cockles, which may find it easier to hold position in the slightly more turbulent deeper water. It is thought that some percentage of the stock remains in deeper water, especially in the cooler months when the tides and weather patterns tend to be more extreme. The Goolwa Cockle uses its muscular foot to bury into the wet sediment, using a series of contractions to rapidly conceal itself. Once holding position in the substrate, the cockle can extend its relatively long inhalant and exhalant siphons to the water-sediment interface, where it is able to feed on small surf diatoms. Goolwa Cockles have separate sexes, with reproduction undertaken by males and females releasing their gametes into the water column for external fertilisation. Reproduction occurs throughout the year, with some peaks in activity possibly occurring in spring. Juvenile cockles are fast growing, achieving harvestable size in approximately thirteen months. In South Australia, there is a large recreational and commercial fishery for Goolwa Cockles. There are a number of restrictions placed on the fishery overall, including a closed season between 1 June and 31 October, a minimum size of 35mm, bag limits and quota for recreational and commercial fishermen respectively, and a number of other commercial restrictions.

By Coby Mathews

Goolwa Cockles with extended siphons

Coby Mathews

T h e C o o r o n g o c e a n b e ac h : A h i g h e n e r g y c o a s t L i n e

17

retreat, the dislodged cockles are washed out to sea and collected in a mesh net. The mesh net is held in the water by the cockler and the mesh is large enough to let small cockles pass through. Once full, the mesh net is emptied into buckets and run to shore, where the cockles are sorted and bagged. Until recently, the harvested cockles were sold largely as bait for catching fish, but the industry now prepares about half of their catch for human consumption, which obtains a premium price.

Hooded Plovers attending nest



Nicholas Birks

Cockles were also a staple food source for the Indigenous Ngarrindjeri. During the summer months, the Ngarrindjeri lived in the sand-dunes of Younghusband Peninsula, harvesting cockles from the ocean beach, and waterfowl and fish from the Coorong lagoons. Extensive middens, consisting of millions of discarded cockle shells, are dotted along the dunes of Younghusband Peninsula from near Barkers Knoll (close to the Murray Mouth) to at least as far as Cantara in the south.4 These middens can be hundreds of metres across and 1-2 metres deep, with some of the shells being dated at around 5,000 years old. That the cockles still exist in economically exploitable numbers reflects the productivity of the cockles themselves, but also is a testament to the sustainable living of the Indigenous communities.

Cryptic eggs of the Hooded Plover



David Paton

Birds of the Coorong ocean beach The ocean beach of Younghusband Peninsula is also home for several bird species, the most notable being the Pied Oystercatcher and Hooded Plover. During summer, typically around 300-400 Pied Oystercatchers and 2030 Hooded Plovers are counted along the ocean beach that lines Younghusband Peninsula opposite the Coorong lagoons.5,6 Both species also use the nearby Coorong lagoons, which provide more sheltered areas for foraging during stormy conditions. Several hundred Sanderlings,

18

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Pied Oystercatcher

Paul Wainwright

a small migratory sandpiper from the Northern Hemisphere, and small numbers of Red-capped Plovers may also be present on the ocean beach in summer, particularly the northern stretches near the Murray Mouth. On the ocean beach, both Hooded Plovers and Pied Oystercatchers forage extensively in the wave swash zone but the foods harvested by these birds are poorly documented. Hooded Plovers are likely to take a range of intertidal invertebrates, including polychaetes, gastropods, bivalves and various crustaceans, such as amphipods.7 Along the Coorong beach they also take terrestrial

insects, including those that have been washed ashore by waves.8 Pied Oystercatchers are likely to consume a similar range of invertebrates, but as they are known to harvest cockles from the wave swash zones on other ocean beaches,9 it is quite likely that cockles are also an important resource for them along the Coorong ocean beach. Both Pied Oystercatchers and Hooded Plovers also nest on open beaches. However, along the Coorong ocean beach, Hooded Plovers are more frequently detected breeding while Pied Oystercatchers usually nest on the islands within the Coorong lagoons.

T h e C o o r o n g o c e a n b e ac h : A h i g h e n e r g y c o a s t L i n e

19

F

2.1 Vehicle tracks across the ocean beach

Percentage of beach runover by vehicles across the ocean beach in the Coorong region, South Australia, in late January to early February 1986 for 43 transects at three locations; (1) beach from 7km north to 7km south of Tea Tree Crossing (25 transects); (2) beach from 5km south to 13km south of 42 Mile Crossing (13 transects); (3) beach at Guichen Bay (5 transects).

“The major impact occurs from vehicles running over nests and sometimes chicks...”

Vehicle tracks across beach

20

DaviD paTon

hooded Plover nesting and oFF-road vehicles There are considerable risks for birds that nest on the ground. Hooded Plovers usually choose a nest site that affords them good views of the surrounding area while sitting on the nest. Along the Coorong beach, nests are placed on the upper beach above the high water mark and usually within a few metres of the base of the fore-dune.10 The higher up the beach that the nest is placed, the less likely that the nest will be washed away during storms. Such a position also allows nesting birds to detect an approaching predator and to quietly leave the nest well before the predator has detected them and their nest. However, the birds respond differently to different types of predators. Birds incubating eggs remain on the nest if potential aerial predators, like ravens, fly over. If a terrestrial predator like a fox approaches, the incubating bird is likely

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

to leave the nest well before the approaching predator is within 100 metres and will not return until the predator is once again 100 metres away. Often the birds will shift away from the nest and wait near the shore. On other occasions, they will distract the predator, feigning injury to draw it away from the nest. The nests themselves consist of little more than a scrape in the sand, and the typical clutch of two or three crypticallycoloured eggs is difficult to detect. Hooded Plovers commence incubating once the clutch is complete and both male and female take turns sitting on the nest. For most (87%) of the time, one or other bird is sitting on the eggs during the day, allowing the other bird to feed. About a month later (28-29 days) the eggs hatch. Although small and only weighing nine grams (about 10% of their parents’ weight), the newlyhatched chicks are capable of running away from the nest within a few hours. The dense cover of dappled and mottled down provides camouflage and insulation. During the first two weeks, the chicks grow at an average rate of about 1.5 grams per day and then, presumably, at an increasingly higher rate as they age.11 They are at least five weeks old before they can fly and, until then, are often referred to as ‘runners’. Although they stay close to their parents during this time, without the ability to fly, they are vulnerable to predation. The chicks normally respond to the presence of a predator by freezing and flattening themselves against the sand. Often this is in or near a piece of seaweed or vegetation, so that their dappled plumage can help them blend into the natural surroundings. While the chicks are motionless, the parents distract the potential predator and draw them away from their young. Hooded Plovers nesting on the ocean beach of Younghusband Peninsula must also contend with increased human presence during spring and summer when they are breeding. The major impact occurs from vehicles running over nests and sometimes chicks, which could be termed ‘mechanical predation’. At times, the density of tracks across the beach can be so high in

Hooded Plover chicks resting in 4WD wheel-rut

Hooded Plover chick

David Paton

Chris Tzaros

places that forty percent of the beach can been run over.12 This is easily measured by running a tape measure across the beach from the base of the fore-dune to the high water mark, and recording for every 10 centimetres whether that 10-centimetre area has been run over recently (Fig. 2.1). Since some of the tracks are quickly covered by wind-blown sand, the amount of the beach that is run over at the time of measurement is an underestimate of the potential impact on nesting birds.

T h e C o o r o n g o c e a n b e ac h : A h i g h e n e r g y c o a s t L i n e

21

Hooded Plovers on the beach

Measuring the actual losses of Hooded Plover nests to vehicles is difficult, because Hooded Plover pairs are widely spaced along the ocean beach, often at five or more kilometre intervals. Therefore, finding enough nests at the time when the birds start laying to determine rates of actual nest losses is challenging. A more effective way of measuring potential predation rates due to vehicle activity on beaches is to deploy dummy nests. Grids of dummy nests, consisting of two pigeon eggs painted cryptically and placed in each scrape, showed that a nest on the Coorong ocean beach during summer had a 6% chance of being run over during a 24 hour period.13 This is equivalent to losing six nests out of one hundred per day. Given that the eggs of Hooded Plovers must be incubated for 28-29 days before hatching, a 6% daily rate for being run over suggests that most of the nests will be lost to vehicles along the ocean beach. Although

22

Nicholas Birks

the prospect of the birds successfully raising a brood of chicks seems remote under that vehicle pressure, the probability of a nest surviving the period of incubation is its probability of surviving for 28 days straight. The probability of surviving one day is 0.94 (94% chance a nest will be unscathed next day), for two days 0.94 x 0.94 (or 0.942), while for 28 days, the probability is equal to 0.9428, resulting in an estimated 17% chance that a nest would survive unscathed from a vehicle (that is, just seventeen out of one hundred nests would remain). Chicks may also be run over by vehicles, adding further to the human impact on the birds. This risk is exacerbated by the chicks’ behaviour of often resting in wheel-ruts where they can keep out of the wind. Since the tyres of vehicles driving along the beach often sit in the deeper tracks left by a previous vehicle, the chicks’ behaviour of sheltering in wheel-ruts increases their risk of being run over.

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Similar impacts are likely on other ocean beaches around Australia where vehicles and people have access. Even the presence of people walking along beaches near nests may disrupt nesting birds. Interestingly, the birds distinguish between vehicles and people. Incubating birds generally move off a nest when people approach to within 100 metres, but a similar response is usually not elicited from a vehicle until it is within about 20 metres.14

some legislative Protection For hooded Plovers nesting on the coorong ocean beach High levels of vehicle activity on the ocean beach threaten the long-term presence of Hooded Plovers in the Coorong region. In 1995, the South Australian government declared a seasonal closure of a section of the ocean beach between Tea Tree Crossing and the Murray Mouth from 24 October to 24 December. During this closed period, only a few vehicles (professional fishermen and emergency vehicles) have access. This has the potential to reduce nest losses for the birds and covers the period of the year when most birds are assumed to lay eggs. The closure of the beach was not welcomed by users or local communities, so the period of closure and the length of the beach that was closed was ultimately a compromise. A significant length of ocean beach occupied by Hooded Plovers remains open south of the closure and Hooded Plovers using those sections of beach receive no respite. Within the seasonally-closed section of beach only those nesting within the period of closure receive a benefit. Since Hooded Plovers can lay eggs any time between August and March, only some breeding attempts are protected from vehicles during the closure. Given that the birds take at least twenty-eight days to lay and incubate their eggs, and the chicks take at least another thirty days before they can fly, most breeding birds will still be exposed to some additional traffic, unless they lay their eggs on the day of initial closure.

Other actions, including driving below the high water mark when the tide is out and sticking to a single track above the high water mark when the tide is in, can reduce vehicle impact for nesting birds. However, although there may be good compliance to this by regular users, there will always be some drivers that take the opportunity to drive ‘off track’, a behaviour mirrored and promoted in commercials advertising four wheel drive vehicles. Any advertising company producing a campaign around responsible use of a four wheel drive vehicle would probably fail to secure a second contract.Yet, from an environmental perspective, such changes are needed. Although the seasonal beach closure has been in force for more than a decade, there has been limited monitoring of the birds to determine if there has been any significant improvement in their breeding success. Annual counts are conducted along sections of the Coorong beach in summer and these show no increase in the abundance of Hooded Plovers along the ocean beach.

Aerial photo of the Coorong coastline

niCHolas Birks

the CooRong oCeAn beACh: A high eneRgy CoAstLine

23

Cars on the beach



So should the seasonal closure be extended to a greater length of the coastline and span a greater part of the breeding season? The arguments for not closing the beach to vehicle traffic are centred on providing access for local people to enjoy their local environment, and economic benefit to local businesses from non-local people using the beach. A less tangible benefit from allowing beach access is a tendency for people to want to protect the places that they enjoy using or have become accustomed to use. Some use of the ocean beach by people is important for establishing that connection. Since the ocean beach along Younghusband Peninsula is difficult to access except by vehicle, vehicular access is likely to continue to be permitted for much of the year. Some people even argue that the current seasonal closure should be discontinued.

24

Tim Thorpe

“...continued use of the ocean

beach as a place for recreation and fishing threatens the existence of Hooded Plovers...” The actual economic value of beach use in the Coorong region is not well-quantified. However, many beaches around Australia have been closed to vehicles and there has been no reported economic hardship as a consequence. Similarly, when the Game Reserve within the South Lagoon of the Coorong was de-gazetted in 1993, there was no obvious broad economic impact on local businesses, despite suggestions that fewer people would be attracted to the region because of the loss of opportunities to hunt native ducks.

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

This is an example of a recurring theme in this book, in that environments continue to be exploited for human use, regardless of the potential detrimental impact on natural assets. Here, continued use of the ocean beach as a place for recreation and fishing threatens the existence of Hooded Plovers within the region. At present, there is no commitment to change how we use this environment to reduce our impact on the birds, for which the ocean beach is their home.

Sand movement off the ocean beach People and vehicles on ocean beaches have other impacts beyond those on birds. The Coorong is a windy place and, even on calm days, an onshore sea breeze often develops, particularly during summer. Onshore breezes, especially on warm days, push the salt spray formed by breaking waves on to the upper beach. Once settled, this spray rapidly dries and forms a thin salt crust over the upper beach above the high tide mark. On undisturbed beaches, this salt crust remains in place and consequently reduces the ability of winds to blow sand off the beach on to the dunes. However, on beaches visited by many people or vehicles, the salt crust is often broken and the sand is potentially more easily blown inland.

selected points across the fore-dune and then at intervals inland. The sets of stainless steel rods were pushed into the sand, such that a specific length of the rod protruded out of the sand. A washer with an internal diameter larger than the rod was then placed over the rod and nestled on to the surface of the sand. If sand was blown away from the surface, the washer would drop down the rod. If sand was deposited at the site then the length of the rod exposed above the sand would be reduced and the additional depth of sand could be determined. By regularly revisiting the rods and taking three measurements – (1) length of rod above the sand, (2) distance from the top of the rod to the washer and (3) depth of sand above the washer - the net change in sand depth at the rod could be determined. Over a one year period (January 1990-January 1991) the faces and crests of the fore-dunes near 42 Mile Crossing had changed by a few (3–9) centimetres, with some losing sand and others gaining. However, inland of the fore-dunes there was a consistent net loss of sand of 2–3 centimetres during this period.

Considerable quantities of sand are blown off the ocean beach on to the fore-dunes of Younghusband Peninsula. Estimates suggest that around 600 tonnes net of sand per kilometre of beach can be blown on to the dunes annually, indicating a dynamic sand-dune system. This estimate was based on capturing the quantities of sand that were blown in different directions across the crest of the first dune or fore-dune. Two techniques have been used to demonstrate the mobility of sand in the dunes adjacent to the ocean beach.15 One method used a series of stainless steel rods and washers to measure changes in the height or depths of sand at

Tyre tracks on the beach

T h e C o o r o n g o c e a n b e ac h : A h i g h e n e r g y c o a s t L i n e

Tim Thorpe

25

The second method involved trapping windblown sand on the top of the fore-dunes using specially-designed traps. The traps were made from drink cans (55mm diameter) with their ends cut out and embedded at right angles into the sides of two-litre plastic drink bottles. These twolitre bottles were turned upside down (with their screw top lids at the bottom) and held vertically upright on a garden stake. Each two-litre bottle had holes cut in their actual bottoms, so that once upturned, air could leave through the top of the trap. Air entering midway up the two-litre bottle (through the drink can) is then decelerated before leaving. However, any sand being carried in the wind drops to the bottom and into the neck of the upturned bottle. This trapped sand can then be removed by unscrewing the lid and draining the accumulated sand into a plastic bag. Once collected, the sand can be dried, weighed and grains sorted into different sizes. The cut-out bottoms of a larger plastic bottle were mounted and glued over the top of the upturned twolitre bottles, leaving good clearance, so as not to interfere with the air leaving the two-litre bottle. These tops prevented material entering the trap from above.

sanD Trap

Vehicle tracks on ocean beach

26

DaviD paTon

The traps were arranged in groups of four with entrances at right angles to each other. Thus the flux of sand from each of four ninety degree directions could be sampled at the same time. A set of four traps was then deployed on the top of the fore-dune, with the entrance of one trap pointing directly to the ocean, another pointing directly inland and the other two parallel to the dune and pointing in opposite directions. Three sets of these traps were then positioned, such that for one set, the bottom lips of the drink cans were 10 centimetres above the current sand surface, and the other two sets were set at heights of 20 and 30 centimetres respectively. The traps were then left in situ and the trapped sand collected at regular intervals (2-4 months) over the next year. The traps facing the ocean beach caught more sand than the other three traps, while the traps facing inland caught the least amount of sand. More sand was trapped during the summer months when the sand was drier. Of the two traps with entrances pointing parallel to the dune, those facing south-east caught more sand than those facing north-west. These patterns of sand movement would be expected given the prevailing winds, particularly during summer. In the area just north of the 42 Mile Crossing access track, the net quantity of sand leaving the beach and moving inland through an area the diameter of a drink can (24cm2) set 10 centimetres above the ground was 8.5 kilograms over the year. The net amount of sand collected is the difference in the sand caught in traps pointing in opposite directions. Smaller amounts of sand were trapped at the slightly higher elevations of 20 and 30 centimetres but the net amounts at these elevations were similar. At these higher elevations, about 3.1 kilograms per 24 cm2 per annum were estimated to be moving inland. Assuming that these traps provide a measure of the quantity of sand that is blown inland, then over a 1-metre wide by 30-centimetre high area, around 600 kilograms (0.6 tonnes) is blown inland annually at this site. Since there

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Tyre tracks on the beach at the Murray Mouth

was no net increase in the quantities of sand on the dunes immediately inland of the fore-dune, much of this sand is likely to have been blown further inland, until it reaches dunes with denser vegetation that may help retain the sand. The net annual movement of sand along the dunes of Younghusband Peninsula in a northerly direction through a drink can set 10cm above the ground was 1.2 kilograms. For the cans set at 20cm and 30cm above the ground, 0.9 kilograms of sand per annum net were recorded as moving northwards. Combining these data, the net movement northwards of sand along the crest of the fore-dune at this site was 129 kilograms per annum for a 1-metre wide by 30-centimetre high area. These traps do not consider sand that is

Tim Thorpe

moved by creep along the surface and therefore should not be used as a measure of the actual volumes of sand leaving the beach. However, they do illustrate that there is considerable flux of sand over the fore-dunes, as well as regular changes to the quantity of sand and fine-scale topography of the fore-dunes. Whether recreational driving of vehicles along the Coorong ocean beach adds to the quantity of sand blown inland is not known. However, if the salt crust that forms on the surfaces of beaches and fore-dunes is important for holding the sand in situ, then any increased activity that breaks that salt crust is likely to increase the quantities of sand being lost. Following some simple rules for driving along the ocean beach would help to

T h e C o o r o n g o c e a n b e ac h : A h i g h e n e r g y c o a s t L i n e

27

minimise this impact, such as driving below the high water mark when the tide is low, driving on a single track above the high water mark when the tide is in, and avoiding driving over foredunes. Vehicle activity, if spread across the beach, may also disrupt other processes as well. For example, seaweed that has been deposited on the beach during spring and summer will slowly decay by terrestrial processes (for example, bacterial breakdown), making nutrients re-available when the winter storms pull this material back into the nearby ocean. If vehicles break the salt crust and break up the decaying seaweed, then winds may blow these smaller fragments and nutrients inland as well, robbing the near-shore areas of some of their nutrients.

The use of ocean beaches for recreation needs to be balanced against a suite of potential impacts on biological assets, like nesting birds, and ecological processes such as sand and nutrient movements. However, there is also a need to develop a connection between modern users and environmental assets so that communities have a commitment to protect them. Finding that balance is challenging but it starts with the current users being aware of impacts and treating their access as a privilege rather than a right. The coastal processes in this region are inherently dynamic, irrespective of any human influence. Sand is constantly moving on and off the beach, constantly moving within the littoral zone, either along the shore or forming or reforming sandbars, and moving on to and over the dunes of the Peninsula.

Cockle shell, ocean beach

28

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Lydia Paton

GF Angas’s illustration of the Murray Mouth

Image courtesy of State Library of South Australia B15276/043

1. Jean Fornasiero, Peter Monteath and John West-Sooby, Encountering Terra Australis: the Australian voyages of Nicolas Baudin and Matthew Flinders (Kent Town: Wakefield Press, 2004). 2. Andrew Short, Beaches of the South Australian Coast and Kangaroo Island (Sydney: University of Sydney Press, 2004). 3. Murray Townsend and Doug Fotheringham, ‘Coastal processes’, in The Murray Mouth. Exploring implications of closure or restricted flow (Canberra: Murray Darling Basin Commission, 2002), 81–3. 4. Nick Harvey, Robert Bourman and Kris James, ‘Evolution of Younghusband Peninsula, South Australia: new evidence from the northern tip’, in South Australian Geographical Journal, 105 (2006): 37–50.

7. S Marchant and PJ Higgins, editors, Handbook of Australian, New Zealand and Antarctic Birds. Volume 2. Raptors to lapwings (Melbourne: Oxford University Press, 1993), 902-12. 8. Andrew Buick, The behavioural ecology of the Hooded Plover (Charadrius rubricollis) on the Coorong during the nonbreeding season. BSc (Hons) thesis (Adelaide: University of Adelaide, 1985). 9.

Marchant and Higgins, 1993, 902-12.

10. Andrew Buick and David Paton, ‘Impact of off-road vehicles on the nesting success of Hooded Plovers Charadrius rubricollis in the Coorong Region of South Australia’, in Emu, 89 (1989): 159–172. 11. Marchant and Higgins, 1993, 902–12.

5. John Bransbury, The status and distribution of the Hooded Plover in South Australia (Adelaide: Report for the SA Department of Environment and Planning, 1988).

12. Buick and Paton, 1989, 159–72.

6. Paul Wainwright and Maureen Christie, ‘Wader surveys at the Coorong and SE coastal lakes, South Australia’, in The Stilt, 54 (2008): 31–47.

14. Buick and Paton, 1989, 159–72.

13. Buick and Paton, 1989, 159–72.

15. David Paton, Movement of sand in the Coorong region, South Australia. Final report for Wildlife Conservation Fund (Adelaide: Department for Environment and Heritage, 2000).

T h e C o o r o n g o c e a n b e ac h : A h i g h e n e r g y c o a s t L i n e

29

Sunrise, Younghusband Peninsula

30

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

David Blair

Chapter 3

Younghusband Peninsula: From discovery and exploitation to reservation

S

itting between the ocean beach and the

sheltered waters of the Coorong are the dunes of Younghusband Peninsula, named after William Younghusband, a member of the Legislative Council of South Australia from 1851 to 1861. These dunes are typically 1-2 kilometres wide and stretch from the Murray Mouth to Kingston SE. From a distance, they provide little vertical relief, as they are rarely higher than 30 metres. Early morning light provides some definition to the sculpture of the tallest peaks and helps contrast bare dunes against darker vegetation at lower elevations. However, such descriptions do these dunes little justice, since at close quarters they are very varied and dynamic– a photographer’s paradise.

on the beach. With onshore winds, this sand can be blown inland to produce coastal dunes. Importantly, a period of relatively stable sea levels is required for sand to accumulate at one location. Thus, barrier systems, such as Younghusband Peninsula, have all formed primarily during the last 7,000 years, when sea levels have been stable following a period of rapid sea rise.1 Various mechanisms have been proposed for the formation of barrier islands and barrier peninsulas. One mechanism involves sea levels rising and flooding the area immediately inland of an already established dune system, with the dunes potentially breached in several places to form islands. Another suggests that barrier islands and peninsulas develop by sand slowly

The dunes protect the Coorong lagoons from the worst of the storms and winds that are generated in the Southern Ocean. The sounds of distant breaking waves on the ocean side of the Peninsula, although dampened by the dunes, remain audible on the mainland side of the Coorong on calm days, and are a constant reminder of the coastal setting.

Formation of Younghusband Peninsula Barrier islands and peninsulas, like Younghusband Peninsula, that protect a coastal lagoon from the full force of waves and storms, only form in areas where there is a very gentle sloping continental shelf and an adequate supply of sand and other unconsolidated materials on the ocean floor. When these two characteristics co-exist, sand can be swept landward by wave action and dumped

Sand-dune,Younghusband Peninsula

y o u n g h u s b a n d p e n i n s u la : f r o m d i s c o v e r y a n d e x p l o i t a t i o n t o r e s e r va t i o n

Tom Bradley

31

accumulating on a submerged ridge running parallel to the coast but out to sea. Eventually this submerged ridge may accumulate sufficient sand and other debris, which is exposed at low tide. With the addition of more sand, a bar or string of islands may form and gradually fuse, forming a barrier that protects the coastal waters on the landward side from the buffeting of waves. In some cases, the submerged ridge may be a previous dune system, consolidated during a period of much lower sea levels, and then submerged when sea levels subsequently rose. The present day Coorong and associated Younghusband Peninsula are the result of fluctuations in sea levels that have taken place over the last 120,000 years, even though the sand-dunes of Younghusband Peninsula have only formed over the last 7,000 years.2 Around 120,000 years ago, the sea level was slightly higher than at present and the coastline ran approximately along the eastern shore of the Coorong or just inland of this. During this period, loose sands would have been dumped by waves on the beach and then blown into a coastal dune system by prevailing south to southwesterly winds. A period of glaciation followed. The sea retreated and the dunes were stranded. Those sand-dunes then gradually consolidated and eventually formed the calcareous ridges that line the eastern shore of the present Coorong lagoons. About 100,000 years ago, and again about 80,000 years ago, brief interglacial periods saw the sea level rise again, but not quite to the same level. Another calcareous ridge was eventually produced, this time about 4km seawards of the previous ridge. Although the sea level fluctuated over the next 60,000 years, the sea did not reach these heights again until recently. Younghusband Peninsula began to form about 6,500 years ago, when an extended period of post-glacial sea level rise stabilised at sea levels similar to those of today. At this time, the shoreline was probably close to the 120,000 year-old dune system, while the 80,000 year-old dune

32

system was partially submerged. Unconsolidated sands were then swept on to the remnant calcareous ridge that had formed previously around 80,000 years earlier. Gradually, islands were produced along this ridge, some of those islands then fused, widened landwards, and increased in height as waves and wind moved sand onshore. Sources of unconsolidated sediments for the construction of dunes include sediments washed out to sea from a major river and from the breakdown of various calcium carbonate products of marine organisms (for example, shells). In the case of Younghusband Peninsula most of the sands are of marine origin.3 So, about 6,000 years ago, the Coorong lagoon was a sheltered body of sea water protected by barrier islands with broad openings to the sea at the northern and southern ends and probably several places in between. This is reflected in the

Younghusband Peninsula

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

David Blair

presence of oyster shells dating back almost 6,000 years in some of the middens of the Ngarrindjeri mid-way along the Coorong, indicative of a protected coastal system that was still being flushed with sea water.4

interdunal flats. They were formed during periods when sea levels were much higher through the Pleistocene epoch, dating back over the last million years.5

Eventually, all but the northern opening near the Murray Mouth closed and Younghusband Peninsula was formed. The character of the Coorong then changed from an entirely marine system to a rather unique lagoon. The northern areas near the Murray Mouth were estuarine and fluctuated from fresh to marine depending on river flows, while the southern reaches, with less water circulation, had the potential to experience higher salinities.

Early European descriptions of Younghusband Peninsula

This modern barrier system, with Younghusband Peninsula protecting the waters of the Coorong, is mirrored inland by a series of ranges that run north-west and parallel to the coast. These inland ranges, once coastal dune barriers, have broad

Large sand-dune,Younghusband Peninsula

The sound of breakers along the ocean beach and the bare sand-dunes of Younghusband Peninsula stand out in early descriptions of the area. Tolmer, who accompanied Major O’Halloran on a punitive expedition to investigate the deaths of passengers and crew following the wreck of the Maria, wrote after crossing the Murray Mouth on 18 August 1840: ‘we ascended the high sandhill known as Barker Knoll, looking north and south. The sight was impressive, nothing could be seen but repeated lines of rollers six or eight feet high’.6

John Cornish

y o u n g h u s b a n d p e n i n s u la : f r o m d i s c o v e r y a n d e x p l o i t a t i o n t o r e s e r va t i o n

33

George French Angas also provided a description based on his experiences in 1844 of crossing Younghusband Peninsula about 10 miles south of Salt Creek. Some of these sand-hills or dunes are of immense height presenting the appearance of barren mountains . . . After toiling for nearly a mile over these sandy mountains, the roar of surf grew nearer and more distinct; and as we gained the summit of the final ridge, the first sight of the ocean burst upon our view. It was a grand and solemn scene: a dull haze shut out the horizon, and the utter and almost awful solitude was unbroken by any living thing.7

However, these early descriptions failed to provide a clear image of the extent of vegetation on Younghusband Peninsula at the time of European settlement and, judging from reports throughout most of the twentieth century, the Peninsula was rapidly transformed from a wellvegetated dune system with some bare dunes, to one where bare shifting dunes dominated. Fortunately, in recent years, the vegetative cover has increased markedly over the Peninsula, suggesting the vegetation has considerable elasticity and resilience. A brief history of European occupation and exploitation of the Peninsula is warranted to put these landscape changes in perspective.

Early European exploration along the Coorong and Younghusband Peninsula

Shacks at Nine Mile Point, 1939 Image courtesy of State Library of South Australia prg 1258/2/168

In 1840, Frome made a quick survey of the Coorong as far south as Salt Creek. He reported abundant feed and water along the shore of the Coorong and suggested it as a good stock route.8 The Coorong repaid his belief, with fresh water readily found by digging shallow wells along its eastern shore. Initially, stock had to be swum across the Murray, but a ferry service was established at Wellington by 1841. In 1846, the route along the Coorong was proclaimed as a travelling stock route, which continued to operate until after World War II.9 George French Angas accompanied Governor Grey and sixteen others on a trip to the South East of South Australia to explore the settlement capabilities in April 1844. He subsequently described the vegetation and scenery along different sections of the eastern side of the Coorong:

Same view, 1966 showing recovery of vegetation Image courtesy of State Library of South Australia prg

34

. . . barren limestone hills, covered with low scrub and stunted vegetation, extend to the east and south-east for a distance of at least seventy miles. In all this district there is not a blade of grass nor a drop of water during the

1258/2/178

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

dry season. To avoid so dreary a region, which is appropriately termed the ‘great desert’, the party followed down the inner shores of the Coorong; where, by digging in the sand, water was always obtained, and the grassy flats bordering upon the scrub afforded pasture for the horses and bullocks at night.10 On 20 April 1844 Governor Grey, Angas and party travelled south-east along the Coorong to Magrath Flat. Angas subsequently wrote that: This day’s route lay along the shores of the Coorong. From the limestone hills of the scrub, into which we occasionally made a detour, the scenery that presented itself was singular and often very picturesque: little bays and miniature harbours were formed by the waters of the Coorong, into which jutted out headlands and peninsulas, often crowned with rocky eminences, or descending in limestone cliffs abruptly to the water. Beneath, on the circling silvery sand that lined these smooth little bays, red-legged gulls, plovers and sandpipers were for ever busy in search of marine insects, or paddling in the gentle ripple of the mimic waves, in undisturbed enjoyment; numerous limestone rocks and small islands, the resort of pelicans and shags, were scattered here and there over the blue surface, and when the sun shone upon them in the evening, and threw a rosy tinge over the opposite sand-hills, it seemed a fairy scene of birds and solitude. Further on, many of these islands are sprinkled with she-oak trees, and look extremely picturesque; but the cheerless hills of the desert, covered with inhospitable scrub, tell of a dreary region, as they rise away towards the blue distance, where the eye sees nothing but one vast rocky wilderness.11 Angas’s description strengthened the view that the best route for travelling stock was along the Coorong. He also noted scrubby flats with salsolaceous bushes (no doubt referring to areas of samphire and various saltbushes) and a belt of sheoak bordering the scrub.

Sand-dunes,Younghusband Peninsula

Lydia Paton

Islands and bays in the Coorong

Tim Thorpe

At M’Grath’s wells [=Magrath Flat] tents were pitched . . . [on] a green and flowery lawn, backed by groves of casuarina and banksia. Hundreds of black swans were swimming on the surface of the Coorong, that there looked like a very broad river, glittering in the calm sunshine of evening.12

y o u n g h u s b a n d p e n i n s u la : f r o m d i s c o v e r y a n d e x p l o i t a t i o n t o r e s e r va t i o n

35

The next day (21 April), Angas and Mason visited that part of the Coorong known as The Narrows and from a high promontory had: an extensive view of the Coorong with its numerous islands and its indented shores . . . Myriads of ducks, swans, pelicans and every variety of seafowl, darkened the water beneath us . . . Humming-bees wandered over the odiferous plants in the scrub, and bustards, ground-parroquets, bronze-winged pigeons, robins, and a variety of birds of brilliant plumage, constantly appeared, as we re-crossed the country towards the appointed

“The limestone reefs which run out into the water are fretted away by the action of the sea-air, that they resemble castles and ruins covered with rich tracery.”

camping-place for the night. We waded our horses half-way across the Coorong; but a strong tide and a deep channel flowing in the centre of the stream, between ‘the narrows’, stopped our further progress. The bed of the Coorong is here a soft white clay, and many lagoons of salt water, which occur along its margin, are connected with it at high tide, and are surrounded by tea-trees, which impart a gloomy character to the scenery. The limestone reefs which run out into the water are fretted away by the action of the sea-air, that they resemble castles and ruins covered with rich tracery. The entire country, from the water’s edge, is covered with surface limestone, in small rugged pieces, amongst which grow the dwarf eucalyptus and the xanthoraea. The natives here construct elevated seats or platforms in bushy she-oak trees, for the purpose of watching and spearing the emu and kangaroo as they pass towards the water to drink.13

Cape Barren Geese

36

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Arthur Grosset

GF Angas’s representation of a Toolache Wallaby near Lake Albert image courtesy of state library of south australia b15276/9

On 22 April, Governor Grey, Angas and party arrived at Salt Creek, a river of salt water flowing out of the Coorong, and running through the desert to the eastward. Open green flats, skirted with she-oaks and a few gum-trees, occur along its margin, and tolerable feed for the cattle was found about our camping-place. Luxuriant tea-trees embower this sluggish stream, the vile waters of which are covered with a green scum. About a quarter of a mile up the creek we found a well of clear fresh water . . . it was surrounded by moss and flowers.14 A further description was provided by Watts Newland who, with AJ Brown, was the first to take sheep across the Murray Mouth to Younghusband Peninsula en route to the South

East of South Australia. The sheep were crossed in a whale boat, while the horses and bullocks were crossed one by one behind the boat. They found the sandhills heavy-going, which necessitated taking the boat up the Coorong to carry the provisions. Brown’s sheep were on one side of the Coorong, while Newland’s, which were obtained from McFarlane’s run (on Narrung Peninsula), were on the other. ‘There was luxuriant feed for stock on both sides as well as plenty of water, and we found an abundance of wild fowl. There were swarms of ducks on the water and plenty of fat turkeys [Australian Bustards] in the sandhills.’15 In addition to the wildlife listed above, Cape Barren Geese, Toolache Wallabies, Dingoes and Common Wombats were also noted during the 1840s.

y o u n g h u s b A n d p e n i n s u L A : f R o m d i s C o v e R y A n d e x p L o i tAt i o n t o R e s e R vAt i o n

37

A samphire flat with Swamp Paperbark in distance, near Tea Tree Crossing

Charles Todd’s descriptions of the Coorong along the route of the first intercolonial telegraph line In the 1850s Charles Todd provided further descriptions of the vegetation and landforms along the Coorong. Todd surveyed the Coorong region from the south going northwards to select a route for the Goolwa to Mt Gambier telegraph line in September 1857. He provided similar descriptions to those of Angas and Newland, with dunes well-covered with grass on Younghusband Peninsula and a succession of sandy flats and hard limestone ridges well-timbered with sheoak along the eastern shore of the Coorong to Magrath Flat. From Maria Creek to Tilley’s crossing-place, on the Coorong, a line of parallel grassy sand ridges and hummocks extend for about half a mile inland, well-covered with shea oaks; between these and a large lagoon, or rather a series of lagoons, dry in summer, is an extensive flat, in some places a little under water, but without trees, and therefore well-adapted for the line. From Tilley’s

38

Bryan Haywood

crossing place, keeping on the sea side of the Coorong, it is mostly a grassy plain, with a few rather high and steep sand hills running across at right angles from the hummocks on the coast to the Coorong, evidently old sand drifts, but with one exception, which is still actively drifting, they are now wellcovered with grass. On the other side of the Coorong the limestone appeared to come to the water’s edge. On the 24th I crossed the Coorong two miles below Bradford’s Cantara at a place called the Chinamen’s Wells, and thence along that side of the Coorong to McGrath’s Flats. For the first eight or nine miles after crossing, the tract is level, and the soil sandy, free, apparently, from rock, and requiring no clearing; from there to McGrath’s Flat, thirty miles, it is a succession of sandy flats, and hard limestone ridges, the latter generally well-timbered with shea oaks, and extending to the edge of the water. This part of the Coorong is extremely picturesque from the number of bays and inlets, and its varied banks, here low and sandy, and there precipitous limestone cliffs, with high

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

promontories stretching out into the middle of the stream. From McGrath’s Flat to Pelican Point, thirtytwo miles, surveyed during the two following days, the line would have to keep, mostly, on a limestone ridge, with shea oaks somewhat thickly congregated. Near to Pelican Point is a thick salt water tea-tree swamp, about 200 yards wide, stretching across from the Coorong to Loveday Bay. All round the Point is quite clear; and from it a fine view of the lake and the hills on the opposite side is obtained. As seen from the Point, the islands between it and Hindmarsh Island appeared low and flat, without trees; probably mere grassy swamps.16 The telegraph line subsequently followed this route: the line running from Goolwa to Pelican Point to Magrath Flat and then southwards along the Coorong, crossing it just south of Chinamans Well and then onto Cantara, Coolatoo etcetera. The sections across the Goolwa Channel to Hindmarsh Island, and to Pelican Point across Lake Alexandrina, were laid underwater. On 1 July 1858, the first inter-colonial telegraph line was open for service, running from Adelaide to Melbourne along the Coorong.17

Early pastoral activity along the Coorong During the late 1840s and 1850s, the land was gradually settled, with pastoral leases issued for areas around the Coorong and also the South East of South Australia. With settlement came an increase in the number of people travelling along the Coorong, with many travelling to the Victorian goldfields and others to the South East. Inns and hotels then established along the transport and mail route and, by 1867, there was a regular coach service between Meningie and Kingston SE. Amongst the earliest settlers were James and

Telegraph pole near Lake Cantara

y o u n g h u s b a n d p e n i n s u la : f r o m d i s c o v e r y a n d e x p l o i t a t i o n t o r e s e r va t i o n

David Blair

39

Chinamans Well

C

hinamans Well, 16 kilometres south of Salt Creek, is both a locality and an actual well. The well is lined with curved limestone blocks to give it a bottle shape, enabling it to be readily covered. Both the limestone and sandstone capping were obtained from nearby quarries.1 Although widely believed to have been built by the Chinese as they travelled from Adelaide to the goldfields in Victoria, Chinamans Well was probably built before this. The Department for Environment and Heritage suggests a date of construction of about 1854, two years before the Chinese arrived in Adelaide en route to the Victorian goldfields.2 Another story from a long-term resident, Laurie (Sam) Mincham (1885-1980), proposes that the well was excavated years before the Chinese walked the Coorong route and that it was the site of a Chinese camp when a party was stricken with sickness from which several died.3

It is likely that the few thousand Chinese who walked from Adelaide to the goldfields camped at this spot or at least used the site as a watering and resting point. The influx of Chinese into South Australia began in 1856 due to the 1855 Victorian Act of Parliament that placed a 10 pound poll tax on all Chinese immigrants arriving in Victoria. To avoid the tax, ship captains landed their passengers at various points in South Australia, to begin with at Port Adelaide.4 For example, at the beginning of June 1856, fifteen hundred Chinese gold seekers landed at Port Adelaide in five ships.5 In 1856, people living around the ill-defined highways leading southward from Adelaide were astounded to see long lines of impassive-faced Celestials clad in traditional Chinese dress, quietly jogging along the tracks; each with a bamboopole laden with his worldly possessions across his shoulder.6 After a short time, those organising the landings worked out that there was a much closer port and between January 1857 and August 1863, 16,261 Chinese men and one woman disembarked at Port Robe.7 Most appear to have walked overland to the Victorian goldfields, led by local men who offered their services for a fee – some took the immigrants most of the way while others led them only a short distance before leaving the unfortunate Chinese to their own devices.8 Others are believed to have walked from Robe north-west along the Coorong to try their luck at the copper mines at Burra Burra, with sometimes fatal results. Lack of water and presumably lack of familiarity with the countryside and routes are rumoured to have led to deaths among the immigrants.9 Chinamans Well and other wells along the Coorong were used as watering points by other travellers between Adelaide and the eastern states, and usage increased with the establishment of the coach service in 1867. There were seven staging posts over the ninety miles of unmade road between Meningie and Kingston SE, with the four northern stages being serviced by Mr Kruse and his sailing ship from Milang.10 The three southern stages, namely Chinamans Well, Coolatoo and White Hut, were supplied by Thomas Smith’s wagon from Kingston.

Chinamans Well

40

David Blair

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

About 100 horses were required for the coach service, with four horses in harness at one time and changes made by hostlers at each of the staging posts. On the completion of the railway line between Adelaide and Melbourne in 1887, the coach service came to an end and many of the buildings fell into ruin, including those at Chinamans Well. The rerouting of the Princes Highway away from the Coorong edge reduced the number of visitors to Chinamans Well. However, with the declaration of the Coorong National Park in 1966 and the increased mobility of the population through the more general use of motor vehicles, visitation rates have risen again.

By P�nny Paton

1.

Department for Environment and Heritage, ‘The Tattler, Edition 12’ . Accessed 5 October 2009.

2.

. Accessed 5 October 2009.

3.

Tom McCourt and Hans Mincham, The Coorong and lakes of the Lower Murray (Adelaide: Beachport Branch of the National Trust, 1987), 7.

4.

Margaret Rendell, ‘The Chinese in South Australia’, in Proceedings of the Royal Geographic Society, 54 (1953): 23–33.

5.

Rendell, ‘The Chinese in South Australia’.

6.

Alex Barrowman, Souvenir of historic Robe (1979).

7.

Wilf Sprengel, Robe’s Chinese invasion (Naracoorte: Hansen Print, 1986), 4.

8.

Rendell, ‘The Chinese in South Australia’.

9.

Sprengel, Robe’s Chinese invasion, 17.

Thomas Dodd. From 1851, they held an occupation licence for 22 square miles of Younghusband Peninsula, stretching from the Murray Mouth to as far south as Rabbit Island, opposite Magrath Flat.18 They originally kept sheep and cattle but these suffered from coast disease (a deficiency of cobalt not understood until the late 1930s), so they switched to breeding horses some time before the 1870s. Initially, cattle were swum across the Murray Mouth to Barkers Knoll, but subsequently the Dodds would swim horses across the Coorong at Gnurlung Point or at Immigrants Landing (near Long Point). Dodd Landing Point, on the mainland side of the Coorong and south of Long Point, was also probably connected with their pastoral operations. Barley, rye and oats were subsequently sown on the flats to provide extra feed for the horses, a practice that continued until about the 1930s, when this part of the Peninsula was largely abandoned.19 Other early settlers on the Peninsula included John Barton Hack, who ran a dairy from 1858 to 1862 on the Peninsula opposite Parnka Point. He built a hut, mainly from drift wood, and made excellent cheese.20 The lease was then taken over by John Baker, who ran sheep and cattle on the Peninsula until his death, at which time the lease was purchased by Barr-Smith.

10. McCourt and Mincham, The Coorong and lakes of the Lower Murray, 112.

The Narrows at Parnka Point

piers brissenden

y o u n g h u s b A n d p e n i n s u L A : f R o m d i s C o v e R y A n d e x p L o i tAt i o n t o R e s e R vAt i o n

41

Cantara Homestead

F

acing transportation from Scotland for a second minor offence, John Gall was sent to South Australia in 1847 by his father. He and his wife Anna purchased Cantara in 1863, sold it, moved away and then bought it again. Subsequently, in 1881-82, they contracted J.J. Jarman to replace the existing house and build Cantara Homestead, a mid-late Victorian style house costing 3,000 pounds. In 1883, they moved in with 11 of their eventual 14 children. The walls of Cantara Homestead were built from local limestone, but most of the other construction materials were imported–the heavy gauge roofing came from Scotland, the cedar from South America, while the fireplaces were of Italian Carrara marble. There were numerous wells, two underground concrete water tanks and many outbuildings. A causeway, most likely constructed around 1850, crosses the salt pans to the homestead. Remnants of magnetic telegraph line poles along the causeway are evidence of the inter-colonial telegraph line route that once ran past Cantara, connecting Adelaide to Melbourne. However, by the early 1900s, the main road and telegraph poles near Cantara were relocated

inland due to sand drifts and a telephone-operated telegraph was then installed, creating the telephone exchange at the homestead. Gall also ran the mail service from Meningie to Kingston SE from 1882 but the service was discontinued in 1889 when the South East railway was completed. Gall continued a mail run from Kingston SE to Cantara, servicing local properties, and opened the Cantara Post Office in 1889, which continued until 1929. In 1938, the Gall family left Cantara, selling it a few years later in 1942. The Department for Environment and Heritage (formerly the South Australian National Parks and Wildlife Service) purchased the property in 1972 and is slowly repairing the homestead. Cantara Homestead has European heritage value due to its association with transport and mail routes and the inter-colonial telegraph between Adelaide and Melbourne. It is also the only example of early European development on Younghusband Peninsula. The above account is based on a Proposal to establish a Research and Education Centre at Cantara (D Paton unpubl. 1994).

By David Paton

Cantara Homestead

42

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

David Blair

Subsequently, a number of farmers farmed the flats on Younghusband Peninsula near Parnka Point, living in basic huts. By the end of the nineteenth century, the flats had been ploughed and sown with lucerne and dairy cows were once again being kept.21 One of the major limitations to farming on Younghusband Peninsula was the lack of easy access across the Coorong, a significant handicap in getting produce to market. A small punt across ‘The Narrows’ at Parnka Point provided a winter crossing of the Coorong but was only big enough for a small cart and horse and still left about 40 miles of sandy uneven track to traverse to Meningie. In summer, when the water levels were much lower, farmers could use one of two tracks near Parnka Point to cross the Coorong with horse and cart–one north and one south of Parnka Point.22 The northern crossing ran from south of The Needles on the Younghusband Peninsula side of the Coorong across to Rabbit Island and then to Magrath Flat, while the southern crossing was near Hack Point. The only alternative was to take the bush track that ran south along the eastern side of Younghusband Peninsula to south of Salt Creek and cross there. By the 1870s, there were significant pastoral activities on the eastern side of the Coorong and to the south as well.23 Thomas McCallum held one of the larger mainland holdings, namely Magrath Flat, which included Parnka Point and Hack Point on the mainland side of the Coorong and all the islands from The Needles to Jack Point. In the 1840s and 1850s, other occupation licences were taken up at Salt Creek and further south.24 They were used mainly for sheep grazing, although wheat was also cultivated near Salt Creek and a few hundred head of cattle were run around Bul Bul Soak on Younghusband Peninsula. Properties to the south of Salt Creek changed hands several times, but from the 1860s, John Gall held significant property from Salt Creek southwards including Cantara Station, Tilleys

Cantara Homestead

David Blair

Swamp Station and Marcollat Station. By the late 1880s, Gall held under lease or freehold nearly all the area south of Salt Creek on both sides of the Coorong, although he relinquished the lease of Marcollat in 1888. These holdings supported 35,000 sheep, 1,500 horses and 1,000 cattle.25 Tilleys Swamp was mainly used for sheep while Cantara carried horses and cattle. Some

y o u n g h u s b a n d p e n i n s u la : f r o m d i s c o v e r y a n d e x p l o i t a t i o n t o r e s e r va t i o n

43

of the gentle dunes and flats near Cantara were cultivated to provide horse fodder. John Gall and family lived initially at Tilleys Swamp but moved to Cantara in the early 1880s, close to the Meningie-Kingston road and the telegraph line. Gall built a new homestead of fourteen rooms, which was located a few hundred metres south of the original homestead, stables and yards, and which he occupied after 1883.26 Cantara was one of the stopovers for changing horses for the mail and passenger coach services during this period and Gall eventually purchased the mail run from Meningie to Kingston in the late 1880s. Cantara also continued to play an important role in inter-colonial communication into the early twentieth century as a telephone exchange. By then, the number of horses run on Cantara was greatly reduced, primarily because of

44

the devastating impacts of rabbits on the coastal vegetation, reducing pastures and contributing to sand drifts. Salt-harvesting was another industry to develop along the Coorong in the early twentieth century, if not a little earlier, with salt being scraped from a large ephemeral salt lagoon on Younghusband Peninsula opposite Stony Well Island, and from an ephemeral salt lake a few kilometres south of Salt Creek along the Old Melbourne Road. The latter site continued to operate until 1967 and the remains of a retaining wall across this lake are still visible today.27 Rabbits first became a serious problem along the Coorong in 188228 and the first fox was reported in 1888.29 Some hardy individuals took advantage of this situation by trapping and shooting rabbits,

A t t h e E of n dsalt-harvesting o f t h e R i v ewall, r – Tsalt h e lake C o osouth rong n d Creek Lower Remains of aSalt

Lakes

Peter Bird

The unique Malleefowl

T

he Malleefowl is a large distinctive ground-dwelling bird, weighing a couple of kilograms.1 Malleefowl are predominantly found in semi-arid mallee areas in southern parts of Australia, across Western Australia, South Australia, Victoria and New South Wales.1 A distinctive feature of Malleefowl is their beautifully camouflaged plumage, which enables them to blend into the dappled light and shade of their mallee habitat. They also have a short bill, feeding primarily on grains and seeds, although at certain times of the year, herbs and invertebrates are important food resources.1

Malleefowl are particularly noted and remembered for their unusual mound-breeding method. The large mounds, measuring up to three metres across, are built from soil and organic litter predominantly by the male birds.1 The female starts to lay in about September or October, in an egg-chamber in the mound.1 She generally lays about one egg a week and between 15 and 24 eggs in total.1 The eggchamber is subsequently incubated by the heat released from the rotting organic litter of the mound until about December or January, at which point solar heat is used until the chicks hatch. The male monitors the temperature of the egg-chamber by thrusting his partly open bill into a hole in its wall and subsequently adjusts the temperature accordingly, by either scraping away sand or covering it with more.2

Malleefowl

lynn pedler

1. S Marchant and PJ Higgins, editors, Handbook of Australian, New Zealand and Antarctic Birds. Volume 2. Raptors to lapwings (Melbourne: Oxford University Press, 1993). 2. Department of Environment, Water, Heritage and Arts, 2009, Leipoa ocellata in Species Profile and Threats Database, Department of the Environment, Water, Heritage and the Arts, Canberra. . Accessed 26 October 2009. 3. J Benshemesh, National Recovery Plan for Malleefowl . Accessed 26 October 2009.

The Malleefowl is listed as vulnerable under the federal Environment Protection and Biodiversity Conservation Act 19992 due to its extensive reduction in range mainly through habitat clearance. The National Recovery Plan for Malleefowl details actions to reverse this decline, such as removing goats and sheep to alleviate grazing pressure and increased fox control.3

By Fiona Paton

yo Y yO uo n U uN gnG hg u Hh sUb uS A sB n bA AN dnDpdePn Ep eN in nI N si n uS LsUAuL :AL Af–:R o fF Rmo Od Mi sd m DCiI s SoCvo O e Rv Vye E RAy YnAdn Ned Dx pe ELxXopP iL to OAiIttTiAotT n iI o O tn No tT Ro Oe sR ee E Rs Sve EARtv ViAotT n iI o On N

45

Concerns for the vegetation of Younghusband Peninsula

Coast Daisy-bush stabilising a dune

Lydia Paton

eking out or supplementing their incomes. It was not until the 1950s, with the arrival of myxamotosis, that the rabbit population was checked, albeit temporarily. Only then did the native vegetation have any chance to recover.30 The last person residing in the make-shift hut opposite Parnka Point was a rabbit-trapper, who vacated the site in the 1950s.

African Boxthorn berries

46

Fiona Paton

By the 1920s, there were concerns about the state of the vegetation on Younghusband Peninsula. Cleland spent three days exploring the northern sections of the Peninsula with Sutton, Ashby, Johnston and Parsons (all notable South Australian naturalists), commenting that more than half of the scrub-covered part had been replaced by shifting sands and that it was likely that most of the plants would be destroyed.31 Many shrubs, especially of Coast Daisy-bush, were seen with just their summits appearing above the sand. Sand also accumulated under the shrubs in the depressions and valleys between the dunes. Few grasses were seen and the cattle that they saw were mainly feeding on sedges. He attributed the loss of vegetative cover to grazing by cattle but was told that a contributing factor was the practice of repeatedly burning the scrub to encourage young shoots on the grasses for grazing stock. However, Tom McCourt was adamant that the major damage to the dune vegetation was the result of rabbits rather than overstocking because the Peninsula never carried large numbers of stock. He also noted that there was unbelievable regrowth of shrubs and grasses when myxamotosis temporarily decimated the rabbit population in the 1950s.32 By the 1970s, rabbits, overgrazing by stock and increasing use of off-road vehicles were all implicated in the destabilisation of the dune systems of Younghusband Peninsula,33 but these concerns date back to the 1920s, when several sections in the northern parts of Younghusband Peninsula were set aside as public reserves.34 All stock was to be excluded from these areas to permit the spread of grasses and so help reduce the sand drifts. In 1948, Sir James Gosse, a keen conservationist and Chairman of the state’s Fauna and Flora Board, gave 1,214 hectares of freehold land on Younghusband Peninsula to the government, asking that, as part of the fight against soil erosion, vegetation be re-instated

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Sparse vegetation on Younghusband Peninsula, 1983

Recovering vegetation,Younghusband Peninsula, 2008

Department for Environment and Heritage

Image by Michael Bell used with the permission of the MDBA

y o u n g h u s b a n d p e n i n s u la : f r o m d i s c o v e r y a n d e x p l o i t a t i o n t o r e s e r va t i o n

47

on the bare dunes to the condition depicted by Angas in his pictures of early South Australia.35 By the 1960s, most of Younghusband Peninsula (at least as far south as Cantara) was no longer viable for grazing, and pastoral activities ceased. However, pastoral activities have had a lasting influence on the vegetation of the Peninsula, not only contributing to the loss of native vegetation through grazing and trampling, but also introducing a wide range of serious environmental weeds from Europe and Africa. Among these are Horehound, African Boxthorn, Onion Weed, Bridal Creeper and introduced grasses such as Perennial Veldt Grass.36

Malleefowl

Daniel Rogers

On the eastern side of the Coorong, extensive areas of mallee and heaths have been cleared, much of it after World War II. In the southern Coorong, a narrow strip of coastal shrubland, which is barely a hundred metres wide, remains along the eastern shore of the South Lagoon between the lagoon and the Princes Highway, at times bordered by a strip of coastal mallee to the east of the highway. Against the shores of the North Lagoon, there are just three patches of coastal vegetation, a few kilometres in length. The stands of Drooping Sheoak and native grasses that Angas, Todd and others described in the 1840s and 1850s have all but gone. Of the native animals recorded during the nineteenth century, some no longer remain, including Australian

48

Bustards, Bush Stone-curlews, Dingoes, Toolache Wallabies and Tammar Wallabies. The Toolache Wallaby, extinct as a species, was last recorded in the Coorong region in the 1940s, when an individual was killed by dogs.37 Other species such as the Common Wombat and Malleefowl, once widespread, are now limited to the southern Coorong and to the more extensive areas of coastal shrubland and coastal mallee, respectively. Farming continues along the eastern side of the Coorong with the majority of the cleared land being devoted to sheep and cattle grazing. The productivity of these areas was improved by planting various pastures, particularly lucerne. In areas near Lake Albert, where pastures could be irrigated, productivity was further improved, allowing substantial dairy herds to establish, at least until recently. Since the destocking of Younghusband Peninsula and the release of the rabbit calicivirus, which has reduced rabbit numbers over the last decade, vegetation is reclaiming some of the denuded areas of Younghusband Peninsula. These changes in vegetative cover are conspicuous in aerial photographs. Recovery of vegetation is also seen in some historical photographs of the same location over time. So although there was a flourish of European activity (predominantly grazing) along the Younghusband Peninsula during the latter half of the nineteenth century, those exploits proved to be unsustainable. The arrival of rabbits undoubtedly hastened this. In hindsight, one has admiration and awe for the earlier settlers but also bewilderment. None of us looking at the Younghusband Peninsula now can see the grazing potential that they saw when they arrived and we would question why the Peninsula was ever settled. There are signs of recovery of the vegetative cover, suggesting that these coastal dune systems have the resilience and capacity to recover. In the following chapter the current dynamics of the vegetation of Younghusband Peninsula and associated fauna are explored.

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

1.

CC von der Borch, ‘Geological history of the Coorong lagoon’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 29–36.

18. McCourt and Mincham, 1987, 53. 19. Department of Environment and Planning, 1984, 69. 20. McCourt and Mincham, 1987, 68.

2.

Von der Borch, ‘Geological history of the Coorong lagoon.’

3.

Mike Hilton, Nick Harvey, Andrew Hart, Kris James and Chris Arbunkle, ‘The impact of exotic dune grass species on foredune development in Australia and New Zealand: a case study of Ammophila arenaria and Thinopyrum juncreiforme’ in Australian Geographer, 37 (2006): 313–34.

21. Department of Environment and Planning, 1984, 69. 22. McCourt and Mincham, 1987, 21. 23. Department of Environment and Planning, 1984, 69. 24. Department of Environment and Planning, 1984, 69. 4.

Hilton, Harvey, Hart, James and Arbunkle, 2006.

5.

RP Bourman, CV Murray-Wallace, AP Belperio and N Harvey, ‘Rapid coastal geomorphic change in the River Murray Estuary of Australia’, in Marine Geology, 170 (2000): 141–68.

25 Department of Environment and Planning, 1984, 69. 26. Department of Environment and Planning, 1984, 69. 27. Department of Environment and Planning, 1984, 70. 6.

AE Tolmer, Reminiscences of an adventurous and chequered career at home and at the antipodes. Volume 1 (London: Sampson, Low, Marston, Searle and Rivington, 1882), 184.

28. Department of Environment and Planning, 1984, 73. 29. McCourt and Mincham, 1987, 155.

7.

8.

9.

George French Angas, Savage Life and Scenes in Australia and New Zealand Volume 1 (London: Smith, Elder and Co, 1847), 145–6. Tom McCourt and Hans Mincham, The Coorong and lakes of the Lower Murray (Adelaide: Beachport Branch of the National Trust, 1987), 5. Department of Environment and Planning, Draft Management Plan: Coorong National Park and Game Reserve (Adelaide: Department of Environment and Planning, 1984), 65.

10 Angas, 1847, 132–3.

30. McCourt and Mincham, 1987, 19. 31. John Sutton, ‘A trip to the Coorong’, in South Australian Ornithologist, 8(3) (1925):75–95. 32. McCourt and Mincham, 1987, 19. 33. DD Gilbertson and MR Foale, editors, The Southern Coorong and Lower Younghusband Peninsula of South Australia (Adelaide: Nature Conservation Society of South Australia, 1977). 34. Department of Environment and Planning, 1984, 70.

11 Angas, 1847, 134–5.

35. Department of Environment and Planning, 1984, 70.

12. Angas, 1847, 136–7.

36. CR Alcock and DE Symon, ‘The Flora’, in The Southern Coorong and Lower Younghusband Peninsula of South Australia, edited by DD Gilbertson and MR Foale (Adelaide: Nature Conservation Society of South Australia, 1977), C25–38.

13. Angas, 1847, 138–9. 14. Angas, 1847, 41. 15. Watts Newland, ‘The Coorong and the Victorian diggings’, in The Coorong and lakes of the Lower Murray, Tom McCourt and Hans Mincham (Adelaide: Beachport Branch of the National Trust, 1987), 74.

37. Department of Environment and Planning, 1984, 40.

16. Extract from Charles Todd’s official report, reproduced in The Coorong and lakes of the Lower Murray, Tom McCourt and Hans Mincham (Adelaide: Beachport Branch of the National Trust, 1987), 108–9. 17. Department of Environment and Planning, 1984, 65.

y o u n g h u s b A n d p e n i n s u L A : f R o m d i s C o v e R y A n d e x p L o i tAt i o n t o R e s e R vAt i o n

49

Younghusband Peninsula 50

Lydia Paton

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

ChAPteR 4

The Ecology of Younghusband Peninsula

T

he CoasTaL vegeTaTion ThaT has

established on Younghusband Peninsula depends on just a few plants that have a remarkable ability to colonise the fore-dunes and other areas with mobile sands. These plants thus reduce the extent of inland sand movement, in turn allowing other plants to establish and flourish. This chapter begins with a brief description of the abilities of colonising plants, followed by an exploration of the composition and dynamics of the coastal scrubs that typically clothe the more sheltered inland dunes and swales, and support terrestrial fauna. In discussing the terrestrial fauna, there is a bias towards birds, reflecting not only their importance in dispersing some of the plants but also the general absence of native mammals. Most native mammals have been eliminated from Younghusband Peninsula, with only Western Grey Kangaroos remaining prominent, and Common Wombats becoming increasingly so in southern areas. However, native Silky Mice, and Western and Little Pygmypossums, still abound in Coastal Mallee, banksia heathlands and Pink Gum scrubs inland of the southern Coorong. As is often the case with areas set aside for conservation, the emphasis on managing flora and fauna is focussed on rare or endangered species and not on managing key components. Of the terrestrial birds, Malleefowl, Orange-bellied Parrots and Rufous Bristlebirds are often singled out.1 Of these species, only Rufous Bristlebirds are prominent in the coastal vegetation of the Coorong. Western Pygmy-possum

the eCoLogY of YoUnghUsBAnd PeninsULA

david PaTon

51

Orange-bellied Parrots are semi-regular winter visitors to coastal areas around the Coorong, with up to ten birds being detected in some years, feeding on a variety of plants including Biddybiddy, Beaded Samphire and the introduced Common Heliotrope.2 Orange-bellied Parrots breed in south-western coastal Tasmania and migrate to coastal areas of Victoria and South Australia for winter. Because of their small and declining population size, they are critically endangered and so contribute to the Ramsar status of the Coorong,3 even though there is little that can be done in the Coorong to enhance their prospects. A pragmatic view would be to manage and enhance the coastal vegetation.

The vegetation of the foredunes The most important native plant in stabilising the fore-dunes and the other mobile dunes of Younghusband Peninsula is Rolling Spinifex. This plant has long rhizomes that grow just below the surface with tussocks arising along the rhizomes at short intervals. As the plant establishes its network of rhizomes, the quantities of sand being blown off the dunes diminish and the presence of the plants reduces the surface speeds of the winds. The plants also trap sand and other material blown in from elsewhere and, if the original plants are buried, then the rhizomes

Orange-bellied Parrot

52

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Chris Tzaros

Rolling Spinifex simply grow up through the sand and produce new tussocks. The seed heads of spinifex are well designed for dispersal, with the seeds aggregated into spherical balls, with a long stiff spinelike protection protruding outwards from each seed. These seed heads, once separated from the plant, are bundled along the beach or over the dunes in the wind, often travelling at considerable speeds. As they are blown along, individual seeds are knocked from the revolving spheres and lodge in the sand. Plants on or near the fore-dune not only contend with the wind and the risk of burial by shifting sands, but also with salt spray that is continually blown inland by on-shore sea breezes. Only a few plants, in addition to Rolling Spinifex, are capable of coping with the salt. Amongst them are the introduced Sea Rocket and the introduced Sea Spurge, both of which were probably brought to Australia in the ballast waters of ships. These plants establish on the gentler slopes of fore-dunes and upper beaches and help to reduce sand movement.

Lydia Paton

Where Rolling Spinifex has begun to stabilise the dunes and the salt spray has somewhat dissipated, other plants can establish. These secondary colonisers include rushes like the Knobby Club-rush, creeping succulents such as Native Pigface and scattered shrubs of Coast

Aerial view of Rolling Spinifex colonising dunes

THE E C O L OG Y OF Y O U NGH U S B A ND P ENINS U L A

Tim Thorpe

53

Daisy-bush and Coastal Wattle, the latter often stunted by sea spray. In places where there are shallow fore-dunes, there are broad expanses of largely bare sand known as ‘blow-outs’, stretching inland for hundreds of metres. Many of these are gradually being re-colonised by Rolling Spinifex. Marram Grass and Sea-wheat Grass, two other introduced plants with similar rhizomatous growth to spinifex, are now prominent in parts of Younghusband Peninsula. Marram Grass was deliberately introduced and planted extensively on Younghusband Peninsula to help reduce sand erosion early in the twentieth century. However, Sea-wheat Grass was probably originally

dispersed to Australia in the ballast of ships, with the species subsequently colonising and spreading along the Coorong ocean beach by natural means from the mid 1980s. The species establishes lower down on the fore-dune and can displace Rolling Spinifex from the front of fore-dunes, often forming a denser sward and a more continuous vegetatively covered fore-dune, and perhaps altering the pattern of sand movement off the beach.4 Unlike Rolling Spinifex, Sea-wheat Grass does not set large quantities of seed and is more likely dispersed when storms erode the fore-dune, dislodging and fragmenting the mats of rhizomes, which are then dispersed via the sea along the coast.

Coastal habitat,Younghusband Peninsula

54

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Lydia Paton

The coasTal scrubs of The younghusband peninsula On the protected slopes of the dunes is a moderately dense coastal scrub, 2-3m tall. Prominent plants in these areas include Coast Daisy-bush, Coastal Wattle, Coast Beard-heath, Common Boobialla, Seaberry Saltbush, Coast Cherry, Coast Bitter-bush and the introduced African Boxthorn. In a few places there are small stands of Coastal Mallee. These coastal scrubs also extend on to the swales between the dunes, where the soils are more consolidated. In the lowest-lying areas of many of the swales, there are dense patches of sedgeland, consisting of Coast Sword-sedge, which are often interspersed with creeping carpets of Muntries. In some places the coastal vegetation abuts the lagoon. However, on the broader flats there is often a band of Smooth Cutting-grass with tussocks of Coast Spear-grass that are displaced by halophytic plants, predominantly samphires, next to the lagoon. In areas south of about Policeman Point, stands of Swamp Paperbark also establish on both sides of the Coorong and around some of the ephemeral saline lakes, often with an understorey of samphires. Thus the vegetation that clothes Younghushand Peninsula is a complex mosaic of different vegetation types.

Purple-gaped Honeyeater

John Cornish

Kangaroo Apple, Nitre-bush, Ruby Saltbush, Sea Box and the introduced Bridal Creeper, can be locally abundant in other coastal areas along the Coorong. The fleshy fruits of Muntries were also taken by Ngarrindjeri and early Europeans, as well as birds.

One striking feature of the coastal scrubs that cover the dune slopes of Younghusband Peninsula is the dominance of fleshy-fruited plant species. In the dunes near 42 Mile Crossing, four plant species were sufficiently prominent to each account for at least 5% of the overall cover of vegetation: Bower Spinach, Coast Beard-heath, Coastal Wattle and Seaberry Saltbush (Table 4.1). All of these plants produce fleshy fruits that are consumed and dispersed by birds. The sixth most prominent plant at this site was Common Boobialla (3.4% overall cover), which also produces fleshy fruits. Bower Spinach is a creeper that often grows under and over other plants and dead timber, as does Climbing Lignum. In addition to the fleshy-fruited plants listed in Table 4.1, other fleshy-fruited plant species such as

the eCoLogY of YoUnghUsBAnd PeninsULA

55

fleshy-fruiTed planTs, frugivorous birds and seed dispersal The majority of the fleshy-fruited plant species in the Coorong produce their fruits over the summer months. Fruits are consumed by a range of frugivorous birds from Silvereyes to Emus to various honeyeaters, like the Singing and Spiny-

T

4.1 Prominent plants of

cheeked Honeyeaters. In fact, during summer, the bird community is dominated by species that consume fruit. Of the thirteen most abundant bird species, which each accounted for at least 2% of the avifauna, six feed predominantly on fruit during the summer in the Coorong. Collectively, these six species accounted for just over 50% of the birds counted, with Silvereyes, Singing Honeyeaters and Spiny-cheeked

Younghusband Peninsula

Frequency of occurrence and average percent cover for each plant species, as well as bare ground and dead plant material in five 100m x 4m wide belt transects in dunes at 42 Mile Crossing,Younghusband Peninsula.The table lists the frequency (number of 250 quadrats (2m x4m; 50 per transect) in which the species occurred, and the average and maximum percent cover recorded in these quadrats.Those plants shown in bold produce fleshy fruits. Only plant species detected in at least 10 quadrats or accounting for more than 10% cover in any one quadrat are shown. Data collected by D Patkin (unpubl.).

56

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Honeyeaters being the most prominent (Table 4.2). As illustrated in Table 4.2, a suite of small insectivorous wrens and thornbills, which largely glean food from shrubs or the ground, also accounted for a significant proportion (25%) of the avifauna. A third group of larger insectivorous birds that mainly forage on or

T

close to the ground and either near or under shrubs - the Rufous Bristlebird, White-browed Babbler and Southern Scrub-robin - accounted for around 9% of the birds (Table 4.2). Some of these insectivorous species will occasionally take fruit too. A fourth group of predominantly granivorous species (seed-eaters) accounted for

4.2 Abundance of terrestrial birds and foraging niches in the Coorong

Species

Foraging niche

Percentage of birds

Frugivore

25.5

Small Insectivore

10.5

Singing Honeyeater

Frugivore

8.4

Spiny‐cheeked Honeyeater

Frugivore

7.6

Superb Fairy‐wren

Small insectivore

6.4

Brown Thornbill

Small insectivore

4.9

Nectarivore

4.1

Frugivore

3.9

Rufous Bristlebird

Medium insectivore

3.3

White‐browed Babbler

Medium insectivore

3.2

Purple‐gaped Honeyeater

Frugivore

3.1

Elegant Parrot

Granivore

2.2

Australian Ringneck

Frugivore

2.1

Southern Emu‐wren

Small insectivore

1.3

Granivore

1.2

Small insectivore

1.2

European Goldfinch*

Granivore

1.2

Southern Scrub‐robin

Medium insectivore

1.1

Variegated Fairy‐wren

Small insectivore

0.9

Medium insectivore

0.9

Beautiful Firetail

Granivore

0.7

Little Raven

Omnivore

0.7

Medium insectivore

0.6

Silvereye White‐browed Scrubwren

New Holland Honeyeater Red Wattlebird

Brush Bronzewing Yellow‐rumped Thornbill

Common Blackbird*

Grey Shrike‐thrush 24 other species

5

List of bird species and their relative abundances counted in coastal scrubs in the Coorong in January from 2004-2008. Counts are based on duplicate area searches of four separate 6-10ha areas of coastal vegetation in each year.The predominant foraging niche during the summer period is given for each species based on records of foraging documented during the counts. * Introduced species.

the eCoLogY of YoUnghUsBAnd PeninsULA

57

T

4.3 Seeds found in scats of frugivorous birds and in seed traps

Source

No. of  scats  sampled

Mean number                       Range                                  Mean number                    Range                                 of seeds per                        of seeds                                  of species per                 of species                                   scat (±s.e.) per scat scat (±s.e.) per scat

Emu

284

1622 ± 77

54‐9833

4.1 ± 0.1

1‐8

Silvereye

735

3.1 ± 0.2

1‐18

1.3 ± 0.0

1‐4

Singing Honeyeater

40

4.8 ± 0.7

1‐23

1.4 ± 0.1

1‐4

Spiny‐cheeked Honeyeater

21

7.9 ± 1.5

1‐29

1.6 ± 0.2

1‐4

269

2.8 ± 0.4

1‐16

1.1 ± 0.0

1‐3

Seed trap

Average number of seeds per scat and number of species of plant per scat for Emus, Silvereyes, Singing and Spinycheeked Honeyeaters and scats collected from seed traps.The scats for Emus were collected by searching broadly across the study area, while those of Silvereyes and honeyeaters were collected from birds retained for short periods of time after being caught in mist-nets. Data collected by D. Patkin (unpubl.). around 5% of the birds and included the Brush Bronzewing, Elegant Parrot and Beautiful Firetail. Emus are also present in these coastal scrubs but are present in such low numbers that they were unlikely to be counted.

Brush Bronzewing

58

Lynn PedLer

Frugivorous birds play an important role in dispersing the seeds of fleshy-fruited plants in the Coorong, and so assist in allowing these plants to colonise areas. In the Coorong region, there are two major dispersers, namely the perching birds, such as Silvereyes and honeyeaters, and Emus. Emus consume exactly the same species of fruit as the perching birds, despite a dramatic difference in size, the Emu weighing more than 30kg when adult, and the Silvereyes and honeyeaters, small 11-100g passerines. However, they do differ in the manner in which they disperse seeds. Emus produce large faeces that frequently contain more than a thousand seeds and are dropped in open areas, while Silvereyes and honeyeaters produce faeces that contain a few seeds and are typically deposited under a tree or shrub. Drusilla Patkin documented some of these differences and explored some of the consequences, for the plants, of being dispersed by these two quite different consumers.5

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Silvereye First of all, there were marked differences in the quantities of seeds voided in the scats of the different bird species. A typical Emu scat contained more than 1,600 seeds from as many as eight plant species, while those of Silvereyes and honeyeaters typically contained 3-8 seeds depending on the bird species, with seeds generally from one or two plant species, and occasionally up to four species (Table 4.3). Second, the two different dispersers differed in the quantities of seeds that were dispersed in an area. To determine how many seeds Emus dispersed, Patkin collected every Emu scat that was deposited in a 1 hectare area over three consecutive years, and found that Emus deposited an average of 95 per year. This equates to Emus dispersing around 154,000 seeds per hectare per annum. The numbers of seeds deposited by perching birds can be estimated by using seed traps placed under shrubs and out in the open. These traps estimated the ‘seed rain’ from perching birds. They were constructed from fibreglass fly wire, which was cut into four triangles and sewn to form a funnel, with a plastic bucket fastened to the apex. The traps sampled an area of 1m2 and were suspended approximately 1m above the ground from four wooden stakes that were hammered into the ground. The traps were deployed under plants

Tom Bradley

Emu faeces

Drusilla Patkin

“...some 1.1 million seeds are dispersed per hectare per year to sites under bushes by perching birds.”

Emu with chicks

THE E C O L OG Y OF Y O U NGH U S B A ND P ENINS U L A

dragos

Moise

59

and in the open, with the ‘seed rain’ measured over three years. As might be expected, the seed traps set under shrubs collected very different quantities of seed compared to those set in open areas between shrubs. Traps set under Coast Beard-heath trapped an average of 296-679 seeds per trap per year over three years. Those traps set under the canopies of Coastal Wattle collected an average of 172-249 seeds per trap per year, while traps in the open caught an average of 1017 seeds per trap per year. These data, coupled with plant cover data (Table 4.1), can be used to estimate the quantities of seeds dispersed by perching birds. Assuming that on average fifteen seeds were deposited per open trap (=1m2) per year and that the bare areas accounted for 45% of the area (Table 4.1), then around 67,250 seeds per hectare per year are dispersed to open areas by perching birds. Assuming that on average 200 seeds are dispersed per m2 per year under bushes and that the cover of bushes in the coastal scrub is 55%, then some 1.1 million seeds are dispersed per hectare per year to sites under bushes by perching birds. Thus, perching birds are more important numerically than Emus as seed dispersers for these plants.

Common Boobialla

60

Fiona Paton

Third, the seedlings of fleshy-fruited plants, namely Black-anther Flax-lily, Coast Beardheath, Common Boobialla, Seaberry Saltbush, Coastal Wattle and Bower Spinach, were only found under the canopies of other plants, indicating that dispersal by perching birds would deposit seeds to favourable sites for germination and establishment. The only exception to this distribution pattern was the fleshy-fruited plant Native Pigface, for which seedlings were also found in open areas. However, this is not surprising. If Native Pigface is bird dispersed, then it is likely to be dispersed to open areas, as only Emus can consume its large fruits. Seedlings of this species found at sites under shrubs could be attributed to dispersal by lizards, such as the Sleepy Lizard, rather than perching birds.

Interactions between fleshy-fruited plants and movements of frugivorous birds The fate of the majority of seeds dispersed by Silvereyes and honeyeaters under the canopies of plants is not known. However, landing under a canopy may provide some protection from seed predators and a better micro-environment for germination and seedling growth. One of the consequences of this pattern of dispersal and recruitment is that the seedlings of different fleshy-fruited plants will potentially compete for space amongst themselves and also with the established plants. In turn, the canopies of those that establish will be intermixed and as their fruiting seasons broadly overlap,6 fleshyfruited plants may also compete for the services of frugivores that disperse their seeds. Closer examination of the fruiting seasons for some of the more abundant plant species shows some separation in the timing of fruiting peaks. For example, abundances of ripe fruit on Coast Beard-heath peak in late December-January, those on Coastal Wattle in January-February, for Common Boobialla February is the peak, while

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Seaberry Saltbush

Lydia PaTon

Seaberry Saltbush generally peaks in MarchApril. This separation of key fruiting times may help reduce interspecific competition, as may the diversity in sizes and composition of the different fruits, their colours and how they are displayed. But the net effect of having broadly overlapping fruiting times is that the frugivores have a smorgasbord of fruit to choose from.

Coast Beard-heath

the eCoLogY of YoUnghUsBAnd PeninsULA

Fiona PaTon

61

The actual distances over which the birds disperse the fruits are difficult to assess. For small perching birds, the seeds are probably excreted within 20-60 minutes of ingestion. In January 2004, Silvereyes caught in mist-nets were fitted with tiny radio-transmitters and then tracked to determine their patterns of movement over the coastal vegetation. The home ranges of eight Silvereyes ranged from 1-75ha (mean 20ha), with the smallest home ranges belonging to breeding birds that were constrained to a nest. Collectively, these Silvereyes spent over 70% of their time in the coastal shrublands, but they also used nearby areas of Swamp Paperbark (25%) and some visited adjacent areas of Coastal Mallee and Smooth Cutting-grass sedgeland. The maximum distances moved by the birds in any 10 minute period ranged from 50 -150 metres for seven individuals, suggesting most seed dispersal will be over short distances. However, one individual moved 4.4km during one 10 minute period, indicating considerable potential for dispersal over longer distances. Silvereyes and other frugivorous species can roam over these coastal scrubs during summer and autumn with little risk, because there

F

south-eastern South Australia

Arrows show where birds banded in the Coorong moved to during winter.

Silvereye

62

4.1 Silvereye movements,

Lynn PedLer

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

is an abundance of fruit. However, once the fruit supplies diminish during autumn, many Silvereyes and honeyeaters are forced to move away. Banding studies show that some of the Silvereyes that live and breed in the Coorong during summer move to areas like the Mt Lofty Ranges for winter (Fig. 4.1). Although the majority of the detected movements of Silvereyes are between the Coorong and the Mt Lofty Ranges, this pattern of movement is likely to reflect areas where banding programs were being conducted (nearly all of these movements were of banded birds being recaptured in mistnets). As a consequence they may not necessarily reflect the movements of all Silvereyes. However, the detected movements indicate an important connection between coastal scrublands and woodlands and heathlands that are some distance from the Coorong. Failing to manage these winter refuges for the frugivorous birds may ultimately result in reduced numbers of frugivorous birds using the Coorong and, with those reductions, reduced seed dispersal for the plants. Thus managing these woodlands and heaths contributes to the resilience of the coastal shrublands of the Coorong. Avian dispersal of seeds has also allowed two introduced plants with fleshy fruits, African Boxthorn and Bridal Creeper, to spread across the coastal scrubs that surround the Coorong. Unlike many environmental weeds, both of these species can invade undisturbed native vegetation. African Boxthorn was originally introduced and planted as hedges to provide windbreaks and protection for stock, but has spread into natural areas in many parts of Australia. Whether it was deliberately introduced to the Coorong is not known, but it tends to be more abundant near those areas that were settled and grazed, suggesting it was deliberately introduced. Bridal Creeper also has been spread via birds into the coastal scrubs of the Coorong and is considered a much more serious environmental weed. The species’ climbing growth and dense foliage can smother other plants and its root mass, a dense

Bridal Creeper

David Paton

mat of tubers, can impede root growth and seedling establishment of native plants. One other specialist fleshy-fruited plant is prominent in the Coorong – the Tea-tree Mistletoe. It parasitises melaleucas, particularly Swamp Paperbark, and like other mistletoes,

THE E C O L OG Y OF Y O U NGH U S B A ND P ENINS U L A

63

Tea-tree Mistletoe

Grey Currawong

64

David Paton

Lynn Pedler

Tea-tree Mistletoe is dispersed by perching birds, whereby sticky seeds excreted by perching birds attach to branches of suitable host trees. The seeds then germinate, infiltrate the bark of the branch and establish a connection with the vascular tissue of the host plant. Unlike the other fleshy-fruited plants in the Coorong, Tea-tree Mistletoe flowers during summer and so provides supplies of nectar for honeyeaters, including some of the more specialist nectar-feeders like the New Holland Honeyeater. Flowering of Teatree Mistletoe largely accounts for the presence of New Holland Honeyeaters in the tea-tree swamps and adjacent coastal shrublands along the southern Coorong during summer. Tea-tree Mistletoe then fruits in late autumn and winter when the majority of other fleshy-fruited plants have finished. By avoiding the times when other plants are fruiting, this mistletoe should increase the likelihood that its seeds will be dispersed to the branches of melaleucas and not to those of non-host plant species. If other plants were fruiting, then the frugivorous honeyeaters would be likely to visit and perch in these other species and so some of the mistletoe seeds would likely be dispersed to inappropriate hosts. A specialist frugivore, the Mistletoebird, may also move into these coastal areas during autumn, significantly improving the dispersal services provided by frugivorous honeyeaters, like the Singing and Spiny-cheeked Honeyeaters. The foliage of Tea-tree Mistletoe stands out in the canopies of Swamp Paperbark, signalling their presence and drawing frugivores to them. A range of other birds also consume fruits in the coastal scrubs at times, including Musk and Rainbow Lorikeets, Grey Currawongs, Little Ravens, the introduced Common Starling and Common Blackbird and, rather surprisingly, Silver Gulls, with the gulls often defaecating or regurgitating seeds along the shore-line of the Coorong.

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Emus on Younghusband Peninsula

Arthur Grosset

The fate of seeds and seedlings in the Coorong region The quantity of seedlings establishing under shrubs and in the open was very low, particularly when compared with the ‘seed rain’. For example, the average density of seedlings under shrubs ranged from 1.16 seedlings/m2 under Coastal Wattle to 2.24 seedlings/m2 under Coast Beardheath, while the ‘seed rain’ was at least 200 seeds/ m2/year. In nearby open areas there were only 0.12 seedlings/m2. A range of non-fleshy-fruited plants also had seedlings in the open, including various grasses and Coast Daisy-bush, but even for these species, the density of seedlings under canopies was often higher than in the open. Any number of factors may account for the low recruitment, including low seed viability, loss of seeds to predators post-dispersal or loss

Coast Daisy-bush

THE E C O L OG Y OF Y O U NGH U S B A ND P ENINS U L A

Lydia Paton

65

A tale of orchids, rabbits & RHD

I

t is hard to imagine how the Coorong National Park landscape has been altered by historical grazing pressure from livestock and rabbits. The livestock are long gone but the insidious effects of rabbits remain. Larger perennial species such as Drooping Sheoak are all but extinct across much of the Coorong hinterland, their highly palatable seedlings continually mowed down by a century of rabbit grazing. But what of ground layer species such as orchids? When rabbit researcher Brian Cooke erected several rabbit-proof exclosures along the Loop Road near Salt Creek in the late 1970s, the landscape was so grazed by rabbits he didn’t suspect there were even orchids in the area. He was only alerted when orchids first appeared in the exclosures several years later. Today, amazingly, at least 10 species grow in the exclosures at a density of 60,000 per hectare. During the three years after Rabbit Haemorrhagic Disease (RHD) arrived in the Coorong in 1996, orchids also became widespread and common outside the rabbit-proof exclosures. Monitoring on 240 experimental plots over the subsequent six years showed a further 6-fold increase in orchid numbers to 66,000 per hectare. Orchid diversity also increased from four to nine species over this period. Extrapolating this to the surrounding area, at least 50 million orchids were recruited in the 1,000 hectare section of park bordering Loop Road. Imagine trying to plant them all! This demonstrates dramatically the benefit to biodiversity conservation from a little rabbit control. While RHD did not control rabbits as spectacularly in the Coorong as in the arid interior, annual winter-spring outbreaks of the disease suppressed rabbit numbers at just the right time for orchids to successfully emerge, flower and set seed. Several years on, rabbit numbers are on the rise. No doubt orchids will wane without ongoing rabbit control.

Pink Caladenia

By Peter Bird, Greg Mutze & David Peacock

66

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s



Peter Bird

of seedlings to herbivores, such as rabbits and kangaroos. Dispersal by Emus is not ideal from an individual seed’s perspective, since only one seed, or at best a few seeds, from the thousands that may be present, will be able to establish from any one scat. Furthermore, the scats of Emus are dropped in the open and along well-traversed tracks used by Emus and other fauna such as Western Grey Kangaroos. Thus any seedling establishing in the open has to contend with greater exposure to the elements (wind and sun) and also the risks of subsequent consumption or trampling by kangaroos and even Emus that use the path. In

addition, for the Emu scats examined by Drusilla Patkin, almost all of the seeds had been parasitised by the grubs of an unidentified moth, rendering the seeds unviable. Since seeds taken from the plants were not parasitised, this parasitisation must have taken place post-dispersal. Brian Cooke demonstrated elegantly for areas on the eastern side of the Coorong that, unless rabbits and kangaroos were excluded with fencing, no seedlings established.7 Cooke was primarily interested in recruitment of Drooping Sheoaks and Swamp Paperbarks. Although the initial seedlings that established inside exclusion plots died in the drought of 1982, other seedlings

Coorong wombats

A

t the time of European settlement, Common Wombats were widespread in the Coorong region, with warrens prominent as far north as Narrung Peninsula. By the middle of the twentieth century, their numbers were greatly reduced and only small numbers remained in the coastal scrubs south of Salt Creek. However, with reductions in the numbers of rabbits, wombats have begun to increase. Rabbits in the Coorong area generally favour well-drained soils and are found at much lower densities in the swampy low-lying areas that are favoured by Common Wombats, and vice-versa. In 1992, when rabbits were cleared from a 50ha experimental plot of well-drained coastal shrubland and grassland near Salt Creek, the pattern of use changed dramatically. The extent to which different herbivorous mammals use areas can be assessed by systematically collecting the faeces deposited by different mammals over predetermined sampling areas. With the extra annual growth of introduced grasses and forbs, Western Grey Kangaroos doubled their use of the treated area compared to adjoining untreated plots where rabbits had not been controlled. Common Wombat activity actually increased ten-fold after a gradual increase in the perennial native grasses and sedges on which they feed, albeit slowly over about four years. Wombats also began to use favourable patches in the adjoining untreated plots but never to the same extent as the areas where rabbits were controlled. Confirmation that rabbits had been restricting kangaroo numbers and largely excluding wombats from this habitat came when Rabbit Haemorrhagic Disease (RHD) reached the Coorong in 1996. Initially, kangaroos dispersed evenly across the two treatments because there was little remaining difference in rabbit numbers but, in subsequent years, their relative numbers varied according to the different effects of RHD on the number of rabbits in the untreated plots. While rabbit numbers remained low, wombat numbers continued to increase in both treated and untreated plots. However, wombats have declined since 2001 after rabbit control treatment ceased and rabbit numbers have gradually recovered from RHD. By Greg Mutze

the eCoLogY of YoUnghUsBAnd PeninsULA

67

Drooping Sheoaks and their rates of growth, Cooke was able to estimate that the last time this species successfully recruited was around the late 1950s, a time when the numbers of rabbits had been decimated by myxomatosis. However, the rabbit numbers recovered and no further periods of recruitment for these plants have taken place since then.

Fenced area in 1978 (top) and again in 2009 (bottom) showing recovery of vegetation after rabbit exclusion Peter Bird subsequently established. If seedlings of these plant species were deployed in areas where rabbits and/or kangaroos had access, then they were quickly discovered and consumed, often within 1-2 days, and particularly during autumn when there was little other feed around. By measuring the sizes of the few remaining mature

68

With the arrival of Rabbit Haemorrhagic Disease in the Coorong region in August 1996, the numbers of rabbits were reduced to about 4.5 rabbits per hectare, a quarter of their longterm average abundance,8 and another potential opportunity for recruitment was presented. However, although rabbit numbers were much lower, subsequent monitoring revealed that there was no recruitment of sheoaks. Additional poisoning, warren ripping and fumigation were used to reduce rabbit densities a further ten-fold to around 0.44 per hectare. Even then, only 3% of deployed sheoak seedlings survived, although the rate of browsing was halved.9 This increased survival was despite the level of grazing by Western Grey Kangaroos and Common Wombats increasing two and three-fold respectively in these areas, suggesting rabbits rather than kangaroos and wombats were the primary factor preventing sheoak recruitment. In comparison, seedlings protected by fencing or brush piles showed high rates of survival (60-100%) and growth during the first year. Although some of these subsequently died, perhaps due to drought, some were up to 5m tall by 2006-7, eight to nine years after original planting. Although Drooping Sheoaks have fared poorly and will continue to do so, even in the presence of small numbers of rabbits, other plants that are less preferred by rabbits have responded, including various species of orchids. The condition of the coastal vegetation along the Coorong is not just influenced by grazing or the intrusion of weeds. Many of the fleshy-fruited plant species are sensitive to frosts and, when severe frosts occur, many of the plants in swales and low-lying areas suffer extensive dieback of

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

T

4.4 Frost damage to fleshy-fruited plants

Plant species

Percentage of canopy intact

Number of  plants 0

90

Coastal Wattle

318

33

14

14

16

15

8

Ruby Saltbush

70

13

9

14

19

29

17

Coast Cherry

154

3

11

11

8

21

45

Coast Beard‐heath

461

7

26

15

16

21

10

African Boxthorn

177

24

10

10

13

12

25

Common Boobialla

285

3

12

14

13

26

17

Sea‐berry Saltbush

327

1

9

16

24

33

16

Canopy conditions of seven fleshy-fruited plant species in January 2007 following severe frosts in August 2006.The table shows the percentage of plants that had different levels of their canopy intact. Plants with 0 had no foliage while those with >90 had at least 90% of their canopy intact. Data pooled for six coastal sites spread between Salt Creek and 10km S of Cantara. their canopies and some plants are killed (Table 4.4). This happened after severe frosts in August 2006, reducing vegetation cover and productivity, in terms of fruit production, for at least the next

Frost-damaged vegetation

three years in low-lying areas in the southern Coorong. Changes in the condition of the vegetation in turn are likely to affect the numbers of birds that these coastal scrubs can support.

Tom BradLey

the eCoLogY of YoUnghUsBAnd PeninsULA

69

Insectivorous birds of the coastal scrubs The second most prominent group of birds using the coastal scrubs in the Coorong region are species that largely consume invertebrates that are either gleaned from the vegetation or taken from the ground or from amongst the fallen plant litter. These mainly insectivorous birds account for around a third of the birds using the coastal vegetation. Unlike the frugivorous and nectarivorous species, these insectivorous species are relatively sedentary, with the same individuals being recaptured in the same areas regularly over several consecutive years.

Coast Cherry

Lydia Paton

Rufous Bristlebird habitat on the dunes of Younghusband Peninsula

70

This group of insectivorous birds can be divided into two groups based on size: small insectivores weighing 6-15 grams and larger species weighing 30-100 grams. The small insectivores include two species of fairy-wren, three species of thornbill, the Southern Emu-wren and the White-browed Scrubwren. These smaller species are widespread



At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Lydia Paton

in a variety of habitats and are not restricted to coastal shrublands, although some species like the Southern Emu-wren require dense low vegetation.10 The second group of larger species includes the Southern Scrub-robin, Whitebrowed Babbler, Grey Shrike-thrush and Rufous Bristlebird.

rufous brisTlebirds: a disTincTive feaTure along The coorong The Rufous Bristlebird is a conspicuous component of the denser coastal scrubs of the Coorong and the South East of South Australia, foraging on the ground and in the leaf litter that exists under Coastal Wattle, Coast Beard-heath and Common Boobialla. As a consequence, bristlebirds are difficult to see, with the bird only being glimpsed as it scurries from one dense clump of vegetation to another. Despite this, the bird is conspicuous because of its penetrating call. Far more often heard than seen, the bird heralds its presence in the dense vegetation by its distinctive call, audible even in a boat on the Coorong lagoon. Rufous Bristlebirds, like most of the other insectivorous species, are sedentary in the Coorong, with pairs occupying year-round home ranges that are typically 2-3 hectares in area.11 A similar species of ground-dwelling bird, the Southern Scrub-robin, is also more often heard than seen in these coastal scrubs, but is not as widely distributed as the bristlebird in the Coorong. Unlike the bristlebird, scrub-robins are inquisitive and will often approach an observer and afford good views.

Male Southern Emu-wren

david PaTon

“...the bird heralds its presence in the dense vegetation by its distinctive call...”

Three subspecies of the Rufous Bristlebird are recognized in Australia, all occupying coastal vegetation. However, the subspecies in southwestern Western Australia (Dasyornis broadbenti litoralis) is extinct, the last individual being recorded in 1906.12 The loss of this subspecies has been attributed to its coastal habitat being

the eCoLogY of YoUnghUsBAnd PeninsULA

71

F

4.2 Sonogram of the call of a pair of Rufous Bristlebirds

 

A Song = male bird; B Song = female bird

Southern Scrub-robin

72

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Lynn PedLer

The song of Rufous Bristlebirds repeatedly burnt and converted to agriculture. The other two subspecies in south-eastern Australia have fared better and are still extant. The nominate subspecies, Dasyornis broadbenti broadbenti, is distributed along the coast from near the Murray Mouth in South Australia to Portland in Victoria, while D. broadbenti caryochrous exists only in Victoria, extending east from near Peterborough to near Torquay. The stronghold for the species is almost certainly the Coorong, because the coastal scrubs of the Coorong are contained within a National Park that is not subject to coastal developments. However, because the birds spend much of their time foraging on the ground and build bulky nests close to the ground, they are likely to be vulnerable to predation by foxes and cats. Within the Coorong region, dense patches of invasive Bridal Creeper may be a new threat, since it restricts access to the ground under native shrubs. Within the Coorong, Rufous Bristlebirds are widely distributed and an estimate of their abundance can be made from mapping the numbers of calling birds in areas of coastal vegetation and extrapolating those counts. Rufous Bristlebirds call throughout the day and year. However, the frequency of calling is greater in the morning and in late winter and spring, so estimating the numbers of calling birds and hence population size is best accomplished at those times. This involves mapping the locations from which different individual birds call. Individual birds can be distinguished from their neighbours because their calls are often slightly different and, often when one bird begins to call, the adjacent territory owners also call. Furthermore, pairs of Rufous Bristlebirds call antiphonally (Fig. 4.2), where the female responds immediately after the call of her mate, so helping to establish the presence of a pair of birds in an area. Using these simple techniques and knowing the area of suitable habitat (shrubland consisting mainly of Coastal Wattle, Coast Beard-heath and Common Boobialla), the estimated population size of Rufous Bristlebirds in the Coorong region is around 7,500.13

Rufous Bristlebird

David Paton

R

ufous Bristlebirds hold small (2-3ha) territories for life and can be fiercely territorial, particularly during the breeding season. As neighbourhoods of bristlebirds tend to be fairly stable through time, the birds need some way of discriminating between their longterm neighbours, and new birds that are trying to ‘invade’ and set up new territories. This is important as individuals do not want to be wasting energy continuously defending territories against established neighbours who are unlikely to invade anyway. One way bristlebirds recognise neighbours from strangers is by sharing a proportion of their ‘song repertoire’ with their neighbours - that is, each bristlebird can sing a range of different songs, and neighbouring birds tend to share more of these songs than birds that live some distance from one another. The theory goes that if a bird singing near me has a similar song that I recognise, I don’t need to worry, but if an unfamiliar song turns up, then it is time to be concerned. Neighbour recognition through song is particularly important for a species like the Rufous Bristlebird, given that its cryptic habits, and dense habitats, preclude other (for example, visual) recognition cues. This relationship between distance and song similarities even extends to different bristlebird populations, with birds from different patches of coastal shrubland possessing distinct song traits. Furthermore, the songs of the two extant subspecies are also different, and have been used to confirm the geographic boundary between the two subspecies.1

By Daniel Rogers 1. DJ Rogers, ‘Geographic song variation within and between populations and subspecies of the rufous bristlebird, Dasyornis broadbenti’, in Australian Journal of Zoology, 51 (2003):1-14.

THE E C O L OG Y OF Y O U NGH U S B A ND P ENINS U L A

73

Beautiful Firetail foraging on sheoak seeds

Seed-eating birds in the coastal scrubs of the Coorong Seed-eating birds form a third group of birds that are much less abundant than frugivores and insectivores, but nevertheless are prominent in the coastal vegetation of the Coorong. Four granivorous bird species were regularly encountered in areas of coastal vegetation where birds were counted during summer: Elegant Parrot, Brush Bronzewing, European Goldfinch and Beautiful Firetail. The seeds consumed by these birds are not well documented for the Coorong. However, a broad range of seeds, including the seeds of native and introduced grasses, sedges, daisies, as well as those of selected shrubs and trees, are likely to be taken. Introduced European Goldfinches largely seek seeds of various introduced thistles during summer. Elegant Parrots mainly consume the

74

Nicholas Birks

seeds of various grasses, both introduced and native, and also seeds of daisies. Beautiful Firetails also consume the seeds of native and introduced plants, but largely take the seeds of native grasses, herbs and sedges. However, the largest granivores – the Brush Bronzewing and the less abundant Common Bronzewing – consume significant quantities of acacia seeds, including the seeds of Coastal Wattle, as well as taking the seeds of grasses and herbs, including the seeds of introduced Salvation Jane. This group of birds may now be a beneficiary of the pastoral activities on the Peninsula, because many of the plants that have been introduced now provide them with sources of seeds, but there is no way of assessing the availability of native seeds prior to European settlement. Seed-eating birds are also likely to have benefited from having access to additional sources of water that were provided for stock along the Peninsula.

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Seeds, being rich in carbohydrates and protein, are good sources of energy and nutrients for the birds, but they contain little water, and so sources of water are critical for the presence of granivorous species in these coastal scrubs. All of these granivorous species regularly seek fresh water to drink, and opportunities to access fresh water abound along Younghusband Peninsula, with waterholes and soaks regularly distributed along the eastern side. Other species of birds, including the largely frugivorous species, also regularly visit waterholes and soaks during summer when the weather is warmer, including most honeyeaters, Silvereyes and Emus. Access to fresh water is also important for mammals, including Western Grey Kangaroos.

Freshwater soaks and waterholes There was never much difficulty in finding fresh water on the Peninsula, since sitting close to the surface within the dunes of Younghusband Peninsula is a lens-shaped aquifer of fresh water, which is recharged by rain that percolates through the dunes.14 The aquifer can be easily accessed by digging in the appropriate places and this provided a secure source of fresh water for the Ngarrindjeri, as well as serving the needs of early Europeans who travelled along the Coorong or settled on the Peninsula. Many of the current existing waterholes on Younghusband Peninsula were probably dug originally by early

Ducks gather where fresh water seeps out of Younghusband Peninsula

THE E C O L OG Y OF Y O U NGH U S B A ND P ENINS U L A

David Paton

75

pastoralists to provide water for their stock, and then regularly maintained to reduce silting and allow easy access for stock. Since the destocking of the Peninsula, dense coastal vegetation has established around many of them. Fresh water is also close to the surface along the eastern or mainland side of the Coorong as evidenced by some place names such as Woods Well, Stony Well and Chinamans Well. These and other wells facilitated travel and settlement of the region by Europeans. At numerous points along the eastern shore of Younghusband Peninsula where it abuts the Coorong lagoons, fresh water from the aquifer seeps out across the shore and into the salty waters of the Coorong. The locations of these seeps and soaks are readily detected since stands of freshwater reeds, such as Common Reed, often establish along the shore-line at the points

of discharge.15 Many of the discharge points are at the back of small bays or coves. Various rushes, such as Juncus species and Spiky Clubrush, are also often prominent at these sites. These freshwater soaks are important sources of fresh water during summer for both terrestrial and aquatic birds, particularly waterfowl such as ducks and swans, with large numbers gathering at the seeps during summer and autumn to drink. Before the provision of waterholes, the birds of Younghusband Peninsula would have relied heavily on these. The flows are more prominent during the early morning, before higher temperatures and associated evaporation reduce the flows to a damp surface. Small quantities of relatively fresh water also seep into the Coorong from the mainland side but these are less frequent and less prominent than the soaks along Younghusband Peninsula.

Male Chestnut Teal

76

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Nicholas Birks

1.

Department of Environment and Planning, Draft Management Plan: Coorong National Park and Game Reserve (Adelaide: Department of Environment and Planning, 1984).

2.

Birds Australia, Coorong and Murray Lakes Orange-bellied Parrot Survey (Melbourne: Birds Australia, 2007).

3.

Bill Phillips and Kerri Muller, Ecological character of the Coorong, Lakes Alexandrina and Albert Wetland of International Importance (Adelaide: Department for Environment and Heritage, 2006).

4.

Mike Hilton, Nick Harvey, Andrew Hart, Kris James and Chris Arbunkle, ‘The impact of exotic dune grass species on foredune development in Australia and New Zealand: a case study of Ammophila arenaria and Thinopyrum junceiforme’ , in Australian Geographer, 37 (2006): 313-34.

5.

Drusilla Patkin, Role of native birds in the distribution of fleshyfruited plants in the Coorong region of South Australia (Final report to the National Estate Grants Program Project # 9766, 2000).

6.

Neville Forde, ‘Relationships between birds and fruit in temperate Australia’, in The dynamic partnership: birds and plants in southern Australia, edited by Hugh Ford and David Paton (Adelaide: Government Printer South Australia, 1986), 42–58.

7.

Brian Cooke, ‘The effects of rabbit grazing on regeneration of sheoaks, Allocasuarina verticilliata and saltwater ti-trees, Melaleuca halmaturorum, in the Coorong National Park, South Australia’, in Australian Journal of Ecology, 13 (1988): 11–20.

8.

Greg Mutze, Peter Bird, David Peacock, Scott Jennings and Brian Cooke, ‘Emerging epidemiological patterns in rabbit haemorrhagic disease and myxomatosis and their effects on rabbit populations in South Australia’, in Wildlife Research, 29 (2002): 577–90.

9.

Peter Bird, Greg Mutze, David Peacock and Scott Jennings, ‘Did RHD suppress rabbit numbers sufficiently to promote seedling recruitment of drooping sheoak, Allocasuarina verticillata, and sweet bursaria, Bursaria spinosa, in coastal South Australia?’, unpublished manuscript, 2009.

Beautiful Firetails drinking

Lynn PedLer

10. David Wilson and David Paton, ‘Habitat use by the Southern Emu-wren Stipiturus malachurus (Aves: Maluridae) in South Australia, and evaluation of vegetation at a potential translocation site for S.m.intermedius’, in Emu, 104 (2004): 37–43. 11. John Seymour, David Paton and Daniel Rogers, ‘The conservation status of the Rufous Bristlebird, Dasyornis broadbenti, in South Australia’, in Emu, 103 (2003): 315–22. 12. Seymour, Paton and Rogers, 2003. 13. Seymour, Paton and Rogers, 2003. 14. BJ Noye, ‘The Younghusband Peninsula’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 38–57. 15. Sybille Winter and Eva Squire, Monitoring fresh water soaks in the Southern Lagoon of the Coorong National Park, South Australia (Adelaide: SA Department of Water, Land and Biodiversity Conservation and SA Department for Environment and Heritage, 2003).

the eCoLogY of YoUnghUsBAnd PeninsULA

77

Dredge, Murray Mouth

78

Image by Michael Bell 4WD used with the permission of the MDBA over the dunes . Nicholas Birks

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

ChAPteR 5

The Coorong Lagoons: Dynamic but hydrologically challenged

t

he wetlaNds associated with the

Lower Lakes and Coorong were designated as a Wetland of International Importance under the Ramsar Convention on 1 November 1985. In nominating this region, Australia accepted an international obligation to manage these wetlands in a manner that maintained their ecological character. As a general rule, the ecological condition at the time of nomination is used as the benchmark against which future changes in ecological character are judged. In 1985, the ecological condition of the key assets of the Coorong and Lower Lakes were not well defined and there were suggestions that these had been seriously

Red-necked Stints in flight

degraded already by reduced flows to the Mouth, a result of increased water extraction upstream. Despite this, the Coorong and Lower Lakes still easily met selection criteria needed for successful nomination. Key attributes of the region included: the diversity of wetlands - from the freshwater wetlands of the Lower Lakes to the estuarine and hypersaline systems of the Coorong; and the vast numbers and diversity of waterbirds that used these wetlands. Trying to reconstruct what the ecological conditions were like historically for the Coorong and Lower Lakes is difficult because humans have a habit of recalling the unusual or extreme

chris tzaros

the CooRong LAgoons: dynAmiC but hydRoLogiCALLy ChALLenged

79

What are Ramsar wetlands? » support plant and/or animal species at a criti cal stage of their life cycles, or provide refuge during adverse conditi ons » regularly support 20,000 or more waterbirds » regularly support 1% of the individuals in a populati on of one species or subspecies of waterbird » support a signifi cant proporti on of indigenous fi sh subspecies, species or families, life-history stages, species interacti ons and/or populati ons that are representati ve of wetland benefi ts and/or values and thereby contribute to global biological diversity

Bar-tailed Godwit

paul waiNwright

R

amsar wetlands gain their name from the Conventi on on Wetlands of Internati onal Importance Especially as Waterfowl Habitat held in Ramsar, Iran, in February 1971. The broad aims of the Conventi on are to halt and, where possible, reverse the worldwide loss of wetlands and to conserve those that remain through wise use and management. Australia is a contracti ng partner to the Ramsar Conventi on.1 At the centre of the Ramsar philosophy is the ‘wise use’ concept. The wise use of wetlands is defi ned as ‘the maintenance of their ecological character, achieved through the implementati on of ecosystem approaches, within the context of sustainable development.’ ‘Wise use’ therefore has at its heart the conservati on and sustainable use of wetlands and their resources, for the benefi t of humankind.

» are an important source of food for fi shes, spawning ground, nursery and/or migrati on path on which fi sh stocks, either within the wetland or elsewhere, depend » regularly support 1% of the individuals in a populati on of one species or subspecies of wetland-dependent non-avian species The Coorong and Lower Lakes were listed under the Ramsar Conventi on as site 321 in 1985.2 There are 159 contracti ng parti es and 1869 sites designated as Wetlands of Internati onal Importance.3

B� P���� P���� 1. The Ramsar Convention on Wetlands, at Accessed 29 October 2009. 2. Department for Environment and Heritage, Coorong, and Lakes Alexandrina and Albert Ramsar Management Plan (Adelaide: SA Department for Environment and Heritage, 2000).

Ramsar wetlands can be listed under one or more of nine criteria, that is that they:

3. The Ramsar Convention on Wetlands, at Accessed 29 October 2009.

» contain representati ve, rare, or unique examples of a natural or near-natural wetland type found within the appropriate biogeographic region » support vulnerable, endangered or criti cally endangered species or threatened ecological communiti es » support populati ons of plant and/or animal species important for maintaining the biological diversity of a parti cular biogeographic region

80

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

events (the droughts and floods), instead of recording the average or typical conditions. In most cases, our individual abilities to benchmark, and to record changes against that benchmark, are limited to our own personal experiences. Being able to marry our observations with those of the previous generations to indicate the extent of changes over the last 100 or so years is challenging. In providing a description of the ecology of the Coorong lagoons (and later the Lower Lakes), I will focus largely on the conditions over the last 20-30 years. However, I will cross reference these modern conditions with some of the earlier descriptions and opinions to provide historical context. The Coorong and Lower Lakes have been targeted for human interventions almost from the day Europeans first arrived on their shores, and proposals to manage these wetlands continue to be proffered. Until recently, most proposals

Aerial view showing the Barrages ca. 1940.

have aimed to manipulate or control water levels or salinities by building weirs, dredging channels or by re-directing water to allow increased human use of the water bodies for transport and agricultural production. Recent proposals have increasingly focused on the recovery, protection or enhancement of natural assets within the wetlands. Of the proposals put forward for the Coorong and Lower Lakes, only a few have been implemented, although these interventions have significantly changed the hydrology of these wetlands. Importantly these wetlands at the end of the River Murray are also influenced by upstream interventions, particularly the extraction of water. Any attempt to manage these wetlands into the future will need to address the current extent of upstream use of water, if the Coorong and Lower Lakes are to have a sustainable future. This section of the book is broken into four chapters. The first focuses on the hydrology of the Coorong and how it has changed. Later chapters explore some of the early natural history

Image courtesy of the State Library of South Australia PRG1258/2/546

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

81

F 82

5.1 Map of the Coorong and Lower Lakes

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

of the region and the biotic responses to changes in hydrology, particularly salinity. The final chapter focuses on the waterbirds of the Coorong and the challenges that they face in using a greatly altered wetland system.

The Coorong lagoons

storms generated in the Southern Ocean. Midway along the Coorong, a peninsula, known as Parnka Point, juts out from the mainland side almost across the Coorong. Here the Coorong lagoon is barely 100 metres wide but elsewhere it can be as great as four kilometres across. By convention, the two lagoons are referred to as the North and South Lagoons.

The Coorong originally referred to the long shallow coastal lagoon stretching south-east along the coast from Pelican Point on the western tip of Narrung Peninsula for 100 kilometres (Fig. 5.1). On the western side of the lagoon, Younghusband Peninsula protects this body of water from the persistent waves and regular

Prior to the completion of the Barrages in 1940, a broad and expansive body of open water north-west of Pelican Point connected Lake Alexandrina to the Murray Mouth. Closer to the mouth, and running either side of Hindmarsh and Mundoo Islands, were three narrower channels that also connected Lake Alexandrina

F

5.2 Map of the Lower Lakes

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

83

Goolwa Barrage to the Murray Mouth. These were the Goolwa Channel, Mundoo Channel and Boundary Creek. Many other small islands also exist within this region, mainly to the east of the larger islands (Fig. 5.2). These islands, channels and expanses of water formed a broad deltaic estuary. Before Tauwitchere Barrage was built, vessels usually accessed the Coorong from Lake Alexandrina. However, the actual access to the entrance of the Coorong at Pelican Point was often difficult when water levels were low because of a calcareous reef that ran between Pelican Point and Tauwitchere Island. Tauwitchere Barrage was ultimately built along the line of that reef, the reef being the extension of the ~120,000 year old Pleistocene shoreline that lines the eastern shore of the Coorong lagoon.1 The construction of the Barrages has significantly altered the hydrology of the Coorong, principally by disconnecting the Coorong from the Lower

84

Nicholas Birks

Lakes and all but eliminating the deltaic estuary. In essence the Barrages have extended the narrow coastal lagoon of the Coorong from Pelican Point north-west to the Goolwa Barrage. This 17 kilometre length of water is now referred to as the Murray Estuary and is often considered part of the Coorong. An examination of the bathymetry of the North and South Lagoons shows that the Coorong consists of a linear series of nine elongated basins with deeper water in the middle. Each basin is around 10 kilometres in length and separated by areas of shallower water.2 The basins are more sharply defined in the South Lagoon where the Coorong is generally wider. The overall average water level is quoted as being around 1.2 metres3 but there is deeper water in each basin, the deepest water (around 4 metres in winter) being found in the Salt Creek Basin, near Salt Creek. However, water levels fluctuate seasonally by around one metre in the southernmost parts of

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

the Coorong (less so in the North Lagoon), with water levels being lowest during late summer and autumn. At this time, there can be extensive mudflats exposed, particularly around the South Lagoon, with the southernmost 12 kilometres (from Tea Tree Crossing south) often completely dry by late summer. Seasonal changes in sea level, rainfall, evaporation and flows over the Barrages largely account for these seasonal changes in water level.4 There are also daily and even hourly changes in water levels, particularly for the southern Coorong, influenced by changes in the strength and direction of winds.5 These shortterm changes in water level can approach 0.3 metres in the South Lagoon, although these are dampened in the North Lagoon. In the Murray Estuary, water levels fluctuate with daily tides, the relative amplitude of these tidal fluctuations decreasing with distance from the Murray Mouth.6 A slight tidal signal penetrates into the northern sections of the North Lagoon.

The total volumes of water in the Coorong during winter (when water levels are highest) are around 150 Gigalitres (GL) for the South Lagoon and 110GL for the North Lagoon and Murray Estuary combined.7 In summer, the volumes of water drop to around 90 and 70GL, respectively. Approximately 170GL of water evaporates from these lagoons per annum.8 An important feature for the ecology of the Coorong is a marked gradient in salinity along its length. The salinity is estuarine near the Murray Mouth, fluctuating between fresh and marine and depending on flows over the Barrages. As one moves south-east down the Coorong, the salinity gradually increases, with the North Lagoon having slightly hypersaline salinities that typically range from being a little above the salinities of sea water to about two times those of sea water. A litre of sea water contains 35 grams of salt. The South Lagoon is moderately hypersaline and ranges from around 1.5 to 4 times the salinity of

Aerial view showing Salt Creek entering the Coorong T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

Tim Thorpe

85

F

5.3 Seasonal changes in salinity along the Coorong from December 1999 to

September 2000

120 

Salinity (g/L) 

Murray  North Lagoon  Estuary 

South Lagoon 

100 

Dec 1999 

80 

Mar 2000 

60 

Jun 2000 

40 

Sep 2000 

20 

Salinity of  sea water 

0  7 

17 

27 

37 

46 

54 

58 

68 

78 

85 

95 

Distance from the Murray Mouth (km) 

sea water, with the southern end of the South Lagoon being more salty than the northern end of the lagoon. This increase in salinity with distance from the Murray Mouth is known as a reverse estuary. In a typical estuary the salinities decrease with distance upstream from the mouth, but for the Coorong, the salinities increase with distance from the mouth – the reverse of an estuary. Figure 5.3 illustrates the longitudinal gradient and seasonal changes in salinities along the Coorong. This salinity profile is typical of the salinities measured in the 1980s9 and 1990s.10 The salinities are also typical of salinities recorded in the 1960s and 1970s.11 For example, Noye provided an overview of the salinities of the Coorong based on measurements taken in the 1960s, where in winter the North Lagoon

86

showed varying degrees of influence from River Murray flows, with brackish or marine waters being found at different times.12 In winter, the South Lagoon was entirely hypersaline, increasing from around 40g/L near Hack Point to 60g/L near Salt Creek, but by the end of summer the salinities in the South Lagoon could approach 90g/L over most of its length. There were periods when the higher salinities were dampened – for example from 1962-64, the salinities at Policeman Point varied from 40-50g/L in winter to 70-80g/L in autumn.13 However, Noye suggested that the salinities in the South Lagoon had gradually increased during the late 1960s and early 1970s, almost reaching the point where plant and fish life could not be sustained. In 1973, the River Murray flooded and significant flows went into the Coorong, diluting

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Murray Mouth and North Lagoon

Image by Michael Bell used with the permission of the MDBA

and flushing out some of the salt from the system and reducing the salinities considerably. This flushing had the effect of re-setting the salinities that then gradually increased until the next substantial flow. A similar pattern was documented in the 1980s.14 These data suggest that, for the last 40 years of the twentieth century, salinities have fluctuated. However, there is no evidence of a trend for salinities to be consistently increasing in the Coorong. Although there were suggestions that the Coorong may have been fresher prior to this, those fresher periods are likely to be linked to years following substantial River flows (viz. the 1956 flood). There were also cases of higher salinities, for example, Noye reports very low water levels and abnormally high salinities in the very hot summer of 1939.15 Slade also noted

that the salinity of the water at Parnka Head Station, near the junction of the two lagoons, was more than twice the density of sea water in the early 1880s, suggesting periods of high salinities comparable to those post-1960.16 Although the vast majority (>99%) of the fresh water that is released over the Barrages leaves through the Mouth, significant volumes of water (from the Coorong’s perspective) flow into the North Lagoon during major flows. This can sometimes be seen as a wedge of fresh water sitting above saline water, but the frequent winds and shallow depth of the Coorong result in ready mixing of the two layers, and any vertical separation of the different waters is short-lived.17 During periods of flood, the Barrage Gates are kept open at least into late summer. As a

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

87

result, water levels remain high throughout the Coorong and the winter salinity levels are sustained well into summer, if not through summer. Lower salinities allow a suite of aquatic organisms to extend their distribution southwards, some moving into the South Lagoon, albeit temporarily. Depending on the extent of freshening, this has in the past included crabs and fish such as Mulloway, though not in recent years. Fishermen were certainly aware that in the year that followed a River Murray flood, the growth of water weed was greater than normal and the fish were more plentiful. Distant memories of catching fish such as Mulloway and Black Bream in the southern Coorong are likely to coincide with periods when the salinities were lower, which are likely to be linked to periods immediately following substantial releases of water over the Barrages (as occurs when the River Murray floods). That those halcyon days have largely deserted the Coorong for the last 30-40 years reflects the infrequency of substantial flows over the Barrages during this period. Also there have been suggestions that the narrow channels that connect the North and South Lagoons, between The Needles in the North Lagoon to around Hack Point in the South Lagoon, have gradually silted, restricting water movement between the lagoons and perhaps contributing to the accumulation of salt in the South Lagoon in recent years. However, early descriptions of these channels suggest there has been little change. For example, the severe constriction in the channel near The Needles at the southern end of the North Lagoon was described in The Register on 7 June 1856, ‘…two islands of limestone impede the channel. The islands are a continuation of a reef from the mainland, with a narrow intricate channel, called The Needles, on the Coorong side.’18 A fuller description of the area was provided in

88

1883 by the Marine Board’s engineer, Mr WE Slade. Slade conducted a survey and estimated the costs of dredging the bars and flats from Lake Alexandrina to Salt Creek to provide sufficient depth of water (4 feet 6 inches) to allow boat passage. The intention was to assess the feasibility of providing safe boat passage to Salt Creek and so eliminate some of the rough coach travel between Meningie and Kingston SE. Arriving at what is known as The Needles, the real difficulty commences. The Coorong here narrows itself to a width of about 500 ft., and the navigation is intercepted by reefs of rocks which run out across the channel, and which doubtless suggested the name of the place. The reefs are dry at low water, with the exception of a narrow channel barely sufficient for a good sized boat to go through; being very disjointed, they could easily be blasted and then dredged. For the next 4,000ft. (about) the channel is narrow, shallow in places, and circuitous, and would require both deepening and straightening. The channel then loses itself in a large flat or bight, but again emerges at the other end, a little to the north-west of Sharp’s or Stony Point. I would, however, recommend that, insted [sic] of following this old circuitous channel, a new and shorter one be made straight across the flat opposite Snake Island. The new channel would be about 3,500ft. long or, 1,000ft shorter than the present one, which is about 4,500ft. Between Sharp’s Point Crossing there ia [sic] a small channel that would require both deepening and straightening. At Sharp’s Crossing the Coorong widens to about three-quarters of a mile, but again narrows at Bluff Island, about two miles further up. The whole of this distance would have to be deepened, and as the bottom is composed of soft black mud, the channel should be made wider, or the constant action of the water caused by the paddles of the steamers would soon wash the banks into the channel and fill it

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

up. At Bluff Island the channel is about 200ft. wide, and makes a sharp turn round the back of the island. I would recommend here leaving the old channel, and cutting through a sandy spit which dries some inches at low water. The length of the proposed channel would be about 2,200ft., as against 4,500ft. at present. The next obstructions are two reefs of limestone, called The Gates, each from 20ft. to 25ft. wide, and running right across the Coorong. These reefs dry at low water, with exceptions of openings barely sufficient to allow a small boat to go through; they are very disjointed, and could easily be blasted., The channel for the next mile, viz., to Panka [sic] Head Station, carries good water, but is very narrow and tortuous. From Panka [sic] Head Station to Howard Island is a distance of about five miles, and the whole of this,

with the exception of a few small holes, will require more or less deepening and widening. At Howard Island the Coorong again widens to about two miles, and good water (about 5ft. to 7ft.) will be found for about a mile south of Fat Cattle Point, but the channel is studded with small islands, reefs and sunken rocks, which should be beaconed off. Some of the rocks will also have to be removed by blasting.19 Although Slades’ description does not provide the actual depths of the channels, the channels clearly have been historically narrow, shallow and circuitous. For those who are familiar with the area, Slade’s detailed description remains accurate. That Younghusband Peninsula farmers regularly crossed the Coorong at two points between

Aerial view of Parnka Point and narrow channels

David Mariuz

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

89

The Needles and Hack Point, at least during summer, also fits with the crossing being narrow and shallow. The presence of many small islands and reefs and sunken rocks are also still key characteristics of the South Lagoon.

Changes To The hydrology oF The Coorong The major changes to the hydrology of the Coorong are linked to major changes in the quantities of water reaching the Murray Mouth. The long-term average quantity of water that would have naturally flowed to the Murray Mouth is around 12,000GL per year (Fig. 5.4). However, these volumes are the predicted quantities of water that would flow on average to the Mouth, if no water was being extracted for human use. They are based on modelling by the Murray-Darling Basin Authority, since there are no actual measures of the quantity of

F

water reaching the Mouth, or being released over the Barrages. Note that the long-term average quantity predicted to have flowed to the Mouth naturally will vary a little, depending on the sequence of years over which the average is based. However, whatever average is used, this is an unbelievable volume of water (12,000GL per year), particularly in comparison to the volume of water in the Coorong (160-250GL). The actual volumes reaching the Murray Mouth are much lower than this, particularly in recent decades, when levels of extraction have been highest. Predicted actual flows for the last three decades, taking current extraction into account, show that the reductions in flows to the Mouth have been most severe in the last decade (Fig. 5.4). In the 1870s, extraction of water from the River Murray commenced in the Kerang region and the volumes extracted have increased steadily since then. As early as the 1880s there were

5.4 Predicted River flows reaching the Murray Mouth since 1901

20,000 

     Natural Flow       Actual Flow 

16,000 

Mean volume  (GL) 

Long‐term Average Flow  12,000 

8,000 

4,000 

0  1900s 

1910s 

1920s 

1930s 

1940s 

1950s 

1960s 

1970s 

1980s 

1990s 

2000s 

Decade 

Mean volumes (GL) of water reaching the Murray Mouth per annum in each decade, based on modelling by the Murray-Darling Basin Authority. Natural flows are those predicted if there were no impediments or extraction of water. Actual flows are those predicted given the current levels of extraction and have only been provided for the last 30 years. The long-term average annual flow is based on predicted natural flows from 1900-2008.

90

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

concerns about the extraction of water leading to more frequent incursions of salt water into the Lower Lakes during periods of low River flow.20 Those concerns were echoed during each of the next five decades, yet the volumes extracted increased from 2,000 to 4,000GL per annum from the 1920s to the 1940s.21 The salty water incursions into Lake Alexandrina caused difficulties for watering stock, particularly during autumn in years of low flow. The lack of access to fresh water also reduced the carrying capacity of the land for stock and resulted in groundwater resources being accessed to provide fresh water. At times, salt water fish were caught commercially in the Lower Lakes. Various options for preventing incursions of salt water into the Lower Lakes were considered and costed but not implemented during this period. This included suggestions of barrages across the Goolwa, Mundoo and Coorong Channels dating as far back as 1890. These were estimated to cost £51,600 in 1892. In 1915, an initial barrage was built across the Mundoo Channel, between

F

5.5

Hindmarsh Island and Mundoo Island, with the object of stopping the main flow of salt water coming in through the Mouth from moving directly into the Lakes. As Mundoo Channel was directly opposite the Mouth, it was believed to be the primary source of salt water entering the Lakes. The solid Mundoo Barrage built of sand bags was blown up in 1917, in part because of fears of flooding some of the floodplains that had been reclaimed for farming upstream of Wellington. In 1919, the Mundoo Barrage was rebuilt with timber and gates as a trial. At that time, the costs to extend the barrages across the Tauwitchere Channel and Boundary Creek were estimated to be £112,000. In due course, the Mundoo Barrage fell into disrepair.22 The current Barrages were eventually commissioned in 1934 for around £600,000, which included a barrage over the Goolwa Channel. Building commenced in 1935 and the five barrages were completed and operational by early 1940 (Fig. 5.5). The Barrages successfully prevented sea water incursions and secured a permanent freshwater environment for the Lakes.

Map of the Barrages

the CooRong LAgoons: dynAmiC but hydRoLogiCALLy ChALLenged

91

Goolwa Barrage

F

image By arthur mostead used with the permissioN of the mdBa

5.6 Predicted River flows reaching the Murray Mouth over the last 20 years 20,000 

     Natural Flow       Actual Flow 

16,000 

Volume (GL) 

Long‐term Average Flow  12,000  8,000  4,000  0  89  90  91  92  93  94  95  96  97  98  99  00  01  02  03  04  05  06  07  08 

Year  Annual volumes (GL) of water reaching the Murray Mouth for the last 20 years based on modelling by the MurrayDarling Basin Authority. Natural flows are those predicted if there were no impediments or extraction of water. Actual flows are those predicted given the current levels of extraction.The long-term average annual flow is based on predicted natural flows from 1900-2008.

92

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

F 250 

5.7 Changes in salinity along the Coorong for January from 2001 to 2009

Murray  Estuary 

North Lagoon 

South Lagoon 

2001  2002 

200 

Salinity (g/L) 

2003 

150 

2004  2005 

100 

2006  2007 

50  2008  2009 

0  ‐2 

5 

12 

18 

28 

38 

45 

49 

55 

62 

67 

72 

77 

82 

87 

92 

97 

Distance from the Murray Mouth (km) 

Changes in salinity along the Coorong for January from 2001 to 2009. Negative two (-2) on the x-axis indicates 2km NW of the Murray Mouth and all other values are to the SE. Following construction of the Barrages in 1940, the volumes of water extracted from the River Murray increased further and by the end of the 1980s, 10,000-11,000GL per annum were being extracted. Modelling suggests that this extraction reduced flows to the Murray Mouth region by around 8,100GL.23 Taking extractions into account, the estimated quantities of water reaching the Mouth during the 1980s were around 4,385GL per annum and 5,456GL per annum during the 1990s. For the nine years from 2000-2008, the average annual volume was just 1,006GL. The low flows over the last nine years are due to both extraction and a regional drought across the Murray-Darling Basin. Without extraction, 4,507GL per annum would have reached the Mouth on average over the last nine years (Fig. 5.6). However, flows to the Murray Mouth have been particularly low since 2001, with no water flowing to the Mouth since 2005.

The almost complete cessation of flows to the Mouth since 2001 has had a profound effect on the salinities of the Coorong, particularly the South Lagoon (Fig. 5.7). In January 2001 and January 2002, the salinities along the South Lagoon were consistently below 100g/L and typical of the salinities that would normally be expected in the Coorong at this time of year. Since January 2002, with negligible flows over the Barrages, the salinities have increased more or less gradually each year. By January 2007, salinities throughout the South Lagoon in summer exceeded 150g/L, more than four times the salinity of sea water (35g/L), and peaked in some areas at over five times the salinity of sea water. The salinities in the North Lagoon have also increased during this period, with the bottom 20 kilometres of the North Lagoon experiencing summer salinities in excess of 100g/L in the last two years.

the CooRong LAgoons: dynAmiC but hydRoLogiCALLy ChALLenged

93

why does The saliniTy in The Coorong Vary seasonally? and whaT has Caused The saliniTy To inCrease oVer The lasT eighT years?

Salt crystals form as the Coorong water evaporates

tom Bradley

Winter salinities in the southern Coorong have also increased over this period and mirror the increases in summer. Typical salinities across the South Lagoon in 2000-2002 were 60-80g/L but for 2007 and 2008 they were typically well above 100g/L, almost double the typical salinities. Similarly, the southern sections of the North Lagoon had salinities around 60-80g/L in recent years, while 8-10 years ago winter salinities were typically 30-50g/L.24 High salinities have profound effects on the types of aquatic plants and animals that can exist along the Coorong and there should be little wonder that the ecology of the Coorong is changing. The biotic responses to these changes in salinity are explored in a later chapter.

94

Higher salinities are expected in the Coorong during summer and autumn than in winter and spring. During the warmer months of the year, significant quantities of water evaporate off the surface of the Coorong, equivalent to about one metre of water per year. Thus, the salinities are typically highest in late summer and early autumn when the water levels in the Coorong are lowest. The salinities in early autumn (March) are likely to be even higher than those for January. These high salinities then decrease during winter and spring due to a seasonal rise in mean sea level (20 centimetres higher in winter than summer), increased rainfall events and greatly reduced evaporation. Rainfall adds fresh water to the surface of the Coorong lagoons and this provides a direct dilution effect that is not immediately countered by evaporative losses which are negligible in winter. Increases in mean sea level lead to increases in the quantity of marine water entering via the Murray Mouth and, if high tides are coupled with storm events and strong north-westerly winds, significant volumes of marine water can be pushed into the Coorong. Since marine water has a lower salinity than the existing water, the salinities drop. These processes lead to water levels in the South Lagoon being consistently higher, by around one metre, in winter and early spring compared to late summer. As spring approaches, mean sea level drops and some of the water from the South Lagoon flows northwards into the North Lagoon. As summer approaches and evaporative losses greatly exceed rainfall, the water level drops and the salinity rises. The reason salinity has increased so dramatically in recent years is simple. For the 1980s and 1990s, flows of fresh water to the Murray Mouth usually occurred from July to December and sometimes into January (Fig. 5.8), with smaller

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

F

5.8 Seasonal patterns of River flows reaching the Murray Mouth

1800 Long-term Average Natural Flow

Volume (GL/month)

1500

Actual Flow 1980s Actual Flow 1990s

1200

Actual Flow 2000s 900 600

Volume (GL/month) 300

0 Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Month Changes in the monthly volumes (GL) of water reaching the Murray Mouth for each of the last three decades, against the natural long-term 109-year average (1900-2008). Data are based on modelling by the Murray-Darling Basin Authority. volumes being released at other times of the year. This was the typical pattern, although the flows would have been much higher in the absence of extraction, with reasonable flows extending into January. As a consequence, moderately fresh water usually sat at the northern end of the Coorong over most of the warmer months. This relatively fresh water was then drawn into the southern Coorong to offset the evaporative losses during summer and, being relatively fresh, carried little salt into the southern Coorong. However, for most of the last nine years, there has been very little water released over the Barrages, and none since 2006. Consequently, instead of relatively fresh water being drawn into the Coorong to offset evaporative losses, marine water has been drawn in. This marine water carries 35g of salt per litre or 35,000 tonnes/GL. Overall, around 170GL of water evaporates off the surface of the Coorong during summer and, although not all of

this is offset immediately (as water levels drop), even a few gigalitres of marine water delivers significant quantities of additional salt to the southern Coorong, causing salinities to rise over time.

Tidal prisms and the Murray Mouth Flows of River water to the Murray Mouth are also important for maintaining an open Mouth and maintaining a connection between the sea and the Coorong and Lower Lakes. Coastal processes, including the volume and direction of sand transported along the beach, sea levels, tides and storms plus the volume of River Murray water discharged to the sea, all have an influence on the width, depth and location of the Murray Mouth. Like so many of the ecological attributes of the Coorong region, the Murray Mouth is

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

95

dynamic, shifting in location, width and depth over time. Since the late 1830s, it has moved a net distance of about 1.6km to the west, but during this 170-year period it has actually moved back and forth along the coast, alternating years when it shifted to the north-west with periods when it shifted to the south-east.25 Reports of significant changes in the locations of sandbars and in the positions, widths and depths of water in the channels and the Murray Mouth, were common throughout the latter half of the nineteenth century. Bennett Hays provided a summary of the influences of river and sea on the dynamics of the mouth, …the river, during the time of its periodical

River Murray Mouth

96

flooding, should be permitted to excavate for itself a channel just sufficient for the passage of its waters, which seldom exceeds 15 feet in depth, while in the interim the ocean should be at full liberty to work away at the filling up of the same, which it never fails to punctually perform, generally managing, before the return of the freshes, to reduce the outlet to a depth of from 4 to 6 feet. . . at the season when there is sufficient depth of water, a strong current is always setting out. . .26 The mobility of the Murray Mouth continued even after the Barrages were installed and flows reduced, with the Mouth shifting back and forth within about a 1.6 kilometre range between 1945

Image by Michael Bell used with the permission of the MDBA

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

and 1995.27 However, the direction of shifts in the Mouth was not clearly linked to the direction of the net movement of sand along the coast,28 nor did River flows have a dominant influence.29 Instead, individual events such as storms during spring tides may have been important. For example, in a two week period in May 2002, a storm coupled with spring tides deposited around 44,000 cubic metres of sand on to the shoals and channels inside the Murray Mouth.30 Over a six month period from December 1999 to June 2000, an additional 88,000 cubic metres of sand were deposited inside the Mouth.31 On the ocean side of the Murray Mouth is a high-energy coast, with a persistent swell that results in waves that are typically 2-4 metres in height, breaking as they come to shore. These waves suspend sand and other material in the water column. Flooding tides then transport that suspended material in through the Murray Mouth. Once inside the Mouth, wave energy is dissipated and the sediments drop out of suspension. The ebb tides that result in water leaving through the Mouth are, on their own, not able to resuspend all of the material and so sediments accumulate inside the Mouth and form sandbars. Significant River Murray flows are then needed to scour and resuspend the sediments and flush them back out to sea. During storms, when the waves coming ashore are larger, more material is likely to be suspended and available for transport in through the Mouth. Prior to any extraction of water from the River Murray, flows to the Murray Mouth were almost continuous, with periods of no flow accounting for only 1% of the time.32 Under these natural conditions, the probability of the Mouth closing was relatively remote, even during droughts. However, the current extraction of water for human uses has reduced the frequency and magnitude of flows to the Murray Mouth, such that periods without flow now amount to 40% of the time.33 This is likely to be even higher in the future, given a predicted hotter and drier climate. Extended periods of no flows lasting more than

100 days are now much more common and it is during these periods that sand accumulates rapidly within the estuary,34 restricting the Mouth further. During floods, the accumulated materials are scoured out and the width of the Mouth is significantly widened. At these times the Mouth may be several hundred metres wide. One of the conspicuous changes to the Murray Mouth region, as a consequence of reduced flows, has been the formation and rapid growth of Bird Island within the Estuary following the construction of the Barrages.35 Bird Island has established near the entrance to Mundoo Channel and its formation is almost certainly related to the lack of discharge through the Mundoo Barrage,36 which would normally have flushed any accumulated sand from the region of the channel back out to sea. In the absence of these flushing flows, sediments accumulated and, when the sandbars were exposed during periods of lower water, some of the loose sand was blown into shallow fore-dunes, which were quickly vegetated.37 Bird Island is now about 1km across, covers more than 40ha and is well vegetated.38 Severe restrictions to the Murray Mouth were reported in 1914 towards the end of an exceptionally dry three-year period, and also during the 1920s and at the end of a two-year drought in 1939.39 However, the first time that the Murray Mouth closed was in April 1981, following a period of no flow. Over a four week period, some 20,000 tonnes of sand accumulated at the Mouth. Although it momentarily reopened in May 1981 during a storm, it quickly re-closed. Eventually the Murray Mouth was re-opened on 15 July 1981 by excavating a channel.40 There were further cases in the 1980s and 1990s when the Murray Mouth became very constricted, but it was not until 2002 that it threatened to close again, following a period of no River Murray flows. Another factor contributing to silting of the Murray Mouth and nearby channels has been significant reductions in the tidal prism. When

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

97

the Murray Mouth is open, a substantial volume of water enters and leaves the Murray Estuary on the tides. Prior to the Barrages being built, the tidally-influenced area within the Murray Estuary was around 97km2 and the tidal prism the quantity of water entering and then leaving the estuary on a tidal cycle - was around 17GL.41 Once the Barrages were built, the area that was tidally influenced was reduced substantially, with the tidal prism estimated to be between 0.6 and 2.2GL,42 although the tidal prism during spring tides was estimated at 20GL.43 Tidal prisms of 15-20GL are equivalent to reasonable River flows and would probably have kept the Murray Mouth open during extended periods of low or no flows.44 However, with much smaller tidal prisms (about 10%), and with low or no River flows, material will accumulate inside the Mouth, causing it to become increasingly constricted, which in turn further restricts the quantity of water entering on tides.45

Sharp-tailed Sandpiper

Red-necked Stint

98

Paul Wainwright

Chris Tzaros

The extent of the tidal prism is important for the migratory waders that use the Murray Estuary, since this largely determines the area of intertidal mudflat that they can use for foraging. Sandpipers that use the Murray Estuary, like Red-necked Stints, Curlew Sandpipers and Sharp-tailed Sandpipers, forage on aquatic invertebrates like polychaete worms, which live in the surface sediments of intertidal mudflats. The birds are limited to foraging on mudflats that are covered by no more than about 6cm of water.46 These depths are determined largely by the length of their legs. When there is no tidal prism, there is no regular fluctuation in water levels over the mudflats, other than small wind-induced changes. With no tidal prism and no significant shift in water levels, the birds are forced to forage on the same narrow strip of mudflat that is covered by a few centimetres of water, potentially day after day. With an open Mouth and full tidal prism, water levels can change by up to half a metre on a regular daily basis within the Murray Estuary47 and the birds can spread their foraging over a broad area of mudflat. Under these conditions, the birds get access to additional mudflats that

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

become progressively exposed as the water level drops on an outgoing tide. Thus, the provision of a tidal prism significantly increases the available habitat for these birds. Such arguments, coupled with the needs of fish (like Mulloway), to be able to move between inshore marine habitats and the more sheltered waters of the Coorong, were sufficient to help persuade the South Australian government to dredge the Murray Mouth and prevent it from closing in 2002. This dredging and subsequent pumping of sand out of the Estuary was intended to provide a lifeline to the Murray Estuary and Coorong during this period of limited River Murray flow. At the time, it was intended to be a short-term measure and was not considered a long-term solution. Seven years later, more than 5.7 million cubic metres of sand have been removed at a cost of over $35 million.48 This sand pumping program will need to continue for several more years, because the likelihood of an environmental flow reaching this region is still at least several years away.

Mudflats in the Coorong

The Murray Mouth sand pumping program is an engineering solution for a symptom and does not address the underlying cause of the problem - the lack of an environmental flow to the Mouth, let alone an adequate environmental flow. Without pumping the accumulating sand out of the Estuary to keep the Murray Mouth open, the Coorong environment would have deteriorated much more rapidly. If the Mouth had closed, the Coorong would have become an isolated evaporation basin, salinities would have risen more sharply and water levels would have dropped rapidly throughout the Coorong. Maintaining an open Mouth has other ecological benefits, such as allowing a range of fish to continue to move between the sea and Coorong. While dredging continues, the northern sections of the Coorong (the so-called Murray Estuary), will experience salinities on or a little above marine salinities, and not outside the tolerances of many of the estuarine-marine organisms that use that part of the Coorong. As

Bryan Haywood

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

99

communication and transport routes to the coast. Some of this fresh surface water was likely to reach the Coorong in some years.

The dredge at the Murray Mouth Image by Michael Bell used with the permission of the MDBA

such, these engineering works allow the Murray Estuary to hang on during the current stressful period, with reasonable prospects of recovery once environmental flows are re-established. However, the overall productivity of these tidallyinfluenced mudflats will decline with time without environmental flows, as River flows add nutrients to the mudflats and help to maintain their productivity.49

Flows from the Upper South East The other potential sources of fresh water for the Coorong are flows from the Upper South East into the southern Coorong via Salt Creek. Much of the South East of South Australia was prone to surface flooding and, in the 1860s, as much as half of the land south of Salt Creek was underwater every wet season.50 These extensive swamps and wetlands largely constrained early

100

The region south-east and inland of the Coorong consists of a series of north-west running ranges separated by broad interdunal flats. The ranges were formed from the beach-dune barriers that established during periods when sea levels were much higher.51 They were then subsequently stranded when sea levels dropped. The interdunal flats are subject to periodic inundation during winter when runoff from rainfall accumulates on the eastern side of the ranges, because the ranges block the westward movement of this surface water to the coast. Although some water may slowly percolate through the range, most of the accumulated surface water moves northwest along the eastern side of the ranges.52 As winter rains accumulate, surface water spreads out across the interdunal flats and then, during summer and autumn, when there is increased evaporation and reduced rainfall, these wetlands retract back to a series of more or less permanent wetlands along the eastern margin of the ranges. Historically, these extensive areas of temporary and permanent wetlands would have been widely used for breeding by a wide range of waterfowl, particularly ducks. However, even though surface flooding of pastures is still a problem in wet years, most of these wetlands have now been drained and the reclaimed areas used for agriculture. The actual quantities of water that historically entered the Coorong via Salt Creek are difficult to re-construct. However, flows did not occur every year and may have been infrequent, with reported flows often coinciding with wetter periods. Assessments for the CardwellBuckingham Committee suggested that surface flows from the Upper South East to the southern Coorong probably occurred on at least 10 occasions during the period from 1865 to 1956.53 This included a period between 1865 and 1912 when flows to the southern Coorong were likely to have been enhanced by drainage works. Initially, flows into the southern Coorong would

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

have only occurred when sufficient water had pooled in Tilley Swamp to breach depressions in the last dune system, and so allow flows into Salt Creek. Early drainage works, including cutting and deepening of the connection between Tilley Swamp and Salt Creek in 1864 and 1886, and construction of drains that increased flows into Tilley Swamp, are likely to have facilitated more water reaching the Coorong. Subsequent to this period, the construction of drains at right angles through the ranges south of the Coorong greatly improved drainage of surface water directly to the sea, and reduced northward flows of surface water towards the Coorong. Most of these major cross drains were constructed between 1944

Salt Creek

and 1972. By the 1990s, the consensus, based on available evidence, was that flows from the South East were not a significant source of fresh water for the Coorong system.54 As the Upper South East was settled, more and more of the deep-rooted native vegetation was cleared and replaced with shallower-rooted pasture crops. Clearance of native vegetation increased dramatically in the 1940s and 1950s but, by the 1970s, large areas of agricultural land were being degraded by dryland salinisation. Dryland salinisation is a process in which salt accumulates in surface soils, reducing agricultural productivity. It is essentially caused by replacing

Paul Wainwright

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

101

deep-rooted native plants with shallow-rooted pastures. Shallow-rooted pastures evapotranspire less water than deep-rooted native vegetation and pastures with shallow roots only access water near the surface. Any rainwater that enters the soil profile is available to plants until it moves beyond the depth of their roots, upon which it continues to percolate through the soil until it reaches the groundwater. This recharges the groundwater and the groundwater rises. Since the underlying groundwater throughout much of the Upper South East is saline, the rise in groundwater brought salt closer to the surface and into the root zones of some of the key pasture plants with disastrous results. The productivity of the region declined as a consequence and there were also increased problems of surface flooding. To recover the productivity of the area, a 270kmlong network of 3-4m deep drains was proposed to intercept the saline groundwater, as well as another 180km of shallower (1-2m deep) surface drains, which were proposed in the mid 1990s to drain water to the sea or Coorong.55 Modelling of the likely yields of water from the proposed Upper South East Drainage Scheme during the early 1990s suggested in excess of 100GL of water may need to be drained annually.

Stoneleigh Park Drain

102

Lydia Paton

Modelling suggested that the addition of 100GL of relatively fresh water into the southern end of the Coorong annually would freshen the South Lagoon, changing the South Lagoon from a hypersaline system, where salinities were above those of sea water most of the time, to an estuarine system where the salinities were less than those of sea water.56 The Australian government eventually approved release of 40GL of drainage water per annum (a 10-year rolling average) into the southern Coorong, provided the hypersaline system was not eliminated. However, they did not specify the actual area of hypersaline wetland that should be retained. Even with a 40GL per annum rolling average, the unique hypersaline environment of the South Lagoon is ultimately replaced by an estuarinemarine environment and the longitudinal salinity gradient is eliminated.57 To date, only 5-10GL of water have been released into the Coorong in some years (and none in others), with these yields having no lasting influence on the salinity of the southern Coorong. In part, the yields are lower than expected because the initial modelling was conducted using a period of higher rainfall, while in recent years lower rainfalls have been experienced. This Drainage Scheme is another clear example of an engineering solution being used to address a symptom (rising saline groundwater) rather than addressing the underlying cause (the loss of deep-rooted native vegetation) of an environmental problem. A more sustainable environmental solution would have considered re-establishing some of the deep-rooted native plants to intercept more water, thereby reducing the risk of saline groundwater rising. However, this would have required some of the cleared farming land on the break of slopes to be revegetated and taken out of farm production. Instead, the Drainage Scheme, as approved, is being implemented. This includes some major cuts through dunes, to allow the water from inland flats to reach the Coorong, leaving a significant ecological footprint. For example, a

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

massive cut was required through the dunes of Stoneleigh Park to the south-east of Morella Basin. Here, a massive multi-tiered drain, perhaps 30m deep and 80m across, was cut through native vegetation that supposedly had been protected under a South Australian government Heritage Agreement. The actual drain snakes for several kilometres through the range, leaving a scar easily visible from the air when flying between Adelaide and Melbourne. In recent years, there have been suggestions of enhancing the flows from the Upper South East to the Coorong to help counter the rising salinities. Much of the region immediately south of the Upper South East continues to be drained directly to the sea (for example, the Blackford Drain near Kingston SE). The intention is to re-

Stoneleigh Park Drain

Stoneleigh Park Drain from the air

tom Bradley

tom Bradley

the CooRong LAgoons: dynAmiC but hydRoLogiCALLy ChALLenged

103

vegetation that has been temporarily flooded. Many of these freshwater wetlands are ephemeral and so the waterfowl are forced to find alternative wetlands during summer and autumn. The Coorong’s immense value to waterbirds is as a summer and drought refuge because it is a permanent body of water due to its connection to the sea. Although the water levels fluctuate seasonally in the Coorong, the lack of suitable fringing vegetation and the higher salinities deter breeding. Therefore, from the ducks’ perspective, both wetland systems are required. So care is required in redirecting and using the drainage water, as the requirements of the freshwater systems should not be sacrificed to increase the volumes that can be released into the Coorong.

The hydrological future of the Coorong

In drought, waterbirds, like the Black-winged Stilt, rely on the Coorong Lynn Pedler

direct some of this drainage water northwards towards the Coorong. The actual quantities of water that might be provided are still being assessed. Importantly, this scheme provides opportunities to re-instate and re-habilitate a series of freshwater swamps en route to the Coorong. These freshwater swamps provide additional and complementary waterbird habitat to the Coorong, particularly for ducks, which breed in these freshwater wetlands and not the Coorong. Rising water levels are often a stimulus for ducks to breed in these freshwater wetlands, with nests being placed low in dense fringing

104

The hydrology of the Coorong has changed considerably as a consequence of River regulation. Those changes have been particularly dramatic in recent years when there has been no flow to the Murray Mouth. Although the current extended drought may provide a convenient scapegoat for the recent deterioration, the deterioration is ultimately due to over-extraction of water from the River, an impact that has been occurring for decades. In the absence of extraction and regulation, water would have flowed to the Murray Mouth most of the time during the current drought conditions. Given that the region is likely to experience a drier climate in the future, the current drought provides a glimpse of the future. If we wish to maintain the ecological characteristics of the Coorong, as we are obliged under the Ramsar Convention, then re-instating an adequate environmental flow to the region is critical. However, for the foreseeable future, reestablishing an adequate flow to the Coorong seems very unlikely. Even the promised meagre and inadequate allocation of 500GL of water for environmental purposes for the River is yet to be

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

secured, and more water than this is required. At the moment, before any water could be released to the Coorong, the water levels in the Lower Lakes (currently below sea level at about -1m Australian Height Datum (AHD) and falling) would need to be returned to levels of around 0.6m AHD. The water to do this is not available. Under the current conditions, the Coorong is likely to continue to deteriorate, with salinities continuing to rise in the southern Coorong.58 Given this, the immediate task is to devise interventions that minimise further deterioration. Appreciating how these hydrological changes have affected the biota, and managing the biota under these changed conditions, are also part of our obligations under the Ramsar Convention. Southern end of Coorong

Grey Teal in flight

Nicholas Birks

Paul Wainwright

T h e C o o r o n g L a g o o n s : d y n a m i c b u t h y d r o l o g i call y c h all e n g e d

105

Coorong, south of Salt Creek, January 2008 1. RP Bourman, CV Murray-Wallace, AP Belperio and N Harvey, ‘Rapid coastal geomorphic change in the River Murray Estuary of Australia’ in Marine Geology, 170 (2000): 141–168. 2. BJ Noye, ‘Waters of the Coorong Lagoons’ in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 59–79.

11. MC Geddes and AJ Butler, ‘Physicochemical and biological studies on the Coorong lagoons, South Australia, and the effect of salinity on the distribution of the macrobenthos’, in Transactions of the Royal Society of South Australia, 108 (1984): 51–62. 12. Noye, ‘Waters of the Coorong Lagoons’, 59–79.

3. Ian Webster. Hydrodynamic modelling of the Coorong (Canberra: CSIRO Water for a Healthy Country National Research Flagship, 2007).

13. Noye, ‘Waters of the Coorong Lagoons’, 59–79.

4.

Webster, Hydrodynamic modelling of the Coorong.

15. Noye, ‘Waters of the Coorong Lagoons’, 59–79.

5.

Noye, ‘Waters of the Coorong Lagoons’, 59–79.

6.

David Walker, ‘What is possible: Hydrology and morphology’, in The Murray Mouth, Exploring the implications of closure or restricted flow. A report to the Murray-Darling Basin Commission (Adelaide: Department of Water, Land and Biodiversity Conservation, 2002).

16. Report to the House of Assembly on 26 June 1883, ‘Dredging, rail and desalination proposals’, in The Coorong and lakes of the Lower Murray, Tom McCourt and Hans Mincham (Adelaide: The Beachport Branch of the National Trust, 1987), 173-4.

7. A Jensen and C Nicolson, Conservation value of the Coorong Ecosystem (Adelaide: Department of Environment and Land Management, 1993). 8.

Jensen and Nicolson,Conservation value of the Coorong Ecosystem.

9. MC Geddes, ‘Changes in salinity and in the distribution of macrophytes, macrobenthos and fish in the Coorong lagoons, South Australia, following a period of River Murray flow’, in Transactions of the Royal Society of South Australia, 111 (1987): 173–181. 10. David Paton (unpubl.).

106

Lydia Paton

14. Geddes, 1987.

17. Geddes, 1987. 18. The Register, 7 June 1856. 19. Report to the House of Assembly on 26 June 1883, ‘Dredging, rail and desalination proposals’, in The Coorong and lakes of the Lower Murray, 173–174. 20. Terry Sim and Kerri Muller, A fresh history of the Lakes: Wellington to the Murray Mouth, 1880s to 1935 (Strathalbyn: River Murray Water Catchment Management Board, 2004). 21. Andrew Close, ‘The impact of man on the natural flow regime’, in The Murray, edited by Norman Mackay and David Eastburn (Canberra: Murray-Darling Basin Commission, 1990), 61–74. 22. Sim and Muller, 2004.

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

23. Close, 1990.

45. Walker, 2002.

24. See Figure 7.5.

46. See Figure 8.1.

25. Kris James, ‘Shift ing sands at the Murray Mouth: evidence from historic surveys 1839-1938’, in South Australian Geographical Journal, 103 (2004): 25–42.

47. Walker, 2002.

26. W Bennett Hays, Engineering in South Australia (London: printed by John Knott , 1856), 30–1.

48. Richard Brown and Tom Campbell, Murray Mouth Sand Pumping Project. Key Performance Indicator monthly report to 31 August 2009 (Adelaide: Department of Water, Land and Biodiversity Conservati on, 2009).

27. N Harvey, ‘The signifi cance of coastal processes for management of the River Murray estuary’ in Australian Geographical Studies, 34 (1996): 45–57.

49. NJ Grigg, BJ Robson and IT Webster, Nutrient budgets and biogeochemical modelling of the Coorong (Canberra: CSIRO Water for a Healthy Country Nati onal Research Flagship, 2009).

28. Harvey, 1996.

50. Graham Allison and Paul Harvey, ‘Freshwater Lakes’, in Natural history of the South East, edited by MJ Tyler, CR Twidale, JK Ling and JW Holmes (Adelaide: Royal Society of South Australia, 1983), 61–74.

29. DJ Walker, ‘The role of river fl ows in the behaviour of the Murray Mouth’, in South Australian Geographical Journal, 90 (1990): 50–65. 30. Ian Webster, An overview of the hydrodynamics of the Coorong and Murray Mouth, (Canberra: CSIRO Water for a Healthy Country Nati onal Research Flagship, 2005). 31. Murray Townsend and Doug Fotheringham, ‘Coastal processes’, in The Murray Mouth. Exploring the implications of closure or restricted flow. Report to the Murray-Darling Basin Commission (Adelaide: Department of Water, Land and Biodiversity Conservati on, 2002), 81-3. 32. CSIRO, Water availabiity in the Murray Darling Basin, A Report to the Australian Government from the CSIRO Sustainable Yields Project (Australia: CSIRO, 2008). 33. CSIRO, Water availability in the Murray Darling Basin. 34. RP Bourman and N Harvey, ‘The Murray Mouth fl ood ti dal delta’, in Australian Geographer, 15 (1983): 403–6. 35. Bourman and Harvey, 1983, 403–6 36. RP Bourman, ‘Geomorphology of the Lower Murray Lakes and Coorong’, in River Murray Barrages Environmental Flows. An evaluation of environmental flow needs in the Lower Lakes and Coorong. A report for the Murray-Darling Basin Commission, edited by Anne Jensen, Michael Good, Paul Harvey, Prudence Tucker and Marti ne Long (Adelaide: Department of Water Resources, 2000), 22–9. 37. RP Bourman and EJ Barnett , ‘Impacts of river regulati on on the terminal lakes and mouth of the River Murray, South Australia’, in Australian Geographical Studies, 33 (1995): 101–15. 38. S Carruthers, ‘Vegetati on change on Bird Island’, in South Australian Geographical Journal, 92 (1992): 19–29.

51. DA Schwebel, ‘Quaternary Dune Systems’, in Natural history of the South East, edited by MJ Tyler, CR Twidale, JK Ling and JW Holmes (Adelaide: Royal Society of South Australia, 1983), 15–24. 52. JW Holmes and JD Waterhouse, ‘Hydrology’, in Natural history of the South East, edited by MJ Tyler, CR Twidale, JK Ling and JW Holmes (Adelaide: Royal Society of South Australia, 1983), 49–59. 53. A Jensen, P Hoey, P Kopli, R Shepherd, M Till and M Weinert, The effects of drainage on groundwater behaviour in Counties Cardwell and Buckingham and the effect on the Coorong (Adelaide: Department of Environment and Planning, 1983). 54. Upper South East Dryland Salinity and Flood Management Plan Steering Committ ee, Upper South East Dryland Salinity and Flood Management Plan. Draft Environmental Impact Statement – for Public Comment (Adelaide: Natural Resource Council of South Australia, 1993). 55. Upper South East Dryland Salinity and Flood Management Plan Steering Committ ee, 1993. 56. Upper South East Dryland Salinity and Flood Management Plan Steering Committ ee, 1993. 57. Computati onal Fluid Mechanics Internati onal, Long-term salinity trends in the Coorong Lagoons (Part 2). Report PIR1-2/2000 for Primary Industries and Resources SA (Adelaide: Computati onal Fluid Mechanics Internati onal, 2000). 58. Rebecca Lester, Ian Webster, Peter Fairweather and Rebecca Langley, Predicting the future ecological condition of the Coorong. Effects of management and climate change scenarios (Canberra: CSIRO Water for a Healthy Country Nati onal Research Flagship, 2009).

39. Paul Harvey, ‘Introducti on’, in The Murray Mouth, Exploring the implications of closure or restricted flow. A Report to the Murray Darling Basin Commission (Adelaide: Department of Water, Land and Biodiversity Conservati on, 2002). 40. Bourman and Harvey, 1983. 41. Harvey, 1996. 42. Harvey, 1996. 43. Walker, 1990. 44. Bourman, Murray-Wallace, Belperio and Harvey, 2000.

the CooRong LAgoons: dynAmiC but hydRoLogiCALLy ChALLenged

107

Pelican landing

108

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Paul Wainwright

ChAPteR 6

The Coorong Lagoons: Early natural history and use of natural resources

g

french angas ProVided some initial descriptions of the Coorong and Lower Lakes and their aquatic wildlife around the time of European settlement based on his visit to the region in April 1844.1 On reaching the ‘low flat shores of Lake Alexandrina, after travelling over the sheoak country beyond the Bremer...the lake appeared intensely blue... the reeds had assumed the yellow garb of autumn, and thousands of birds, pelicans, black swans, and ducks were scattered over the smooth bosom of the water’. Along the shores of the North Lagoon of the Coorong, on the sandy bays between the rocky headlands ‘red-legged gulls, plovers and sandpipers, eorge

Black Swan

were forever busy in search of marine insects, or paddling in the gentle ripple of the mimic waves in undisturbed enjoyment’. Near Magrath Flat hundreds of Black Swans were swimming on the surface of the Coorong. Next day when looking over the Coorong from a high promontory near The Narrows, Angas contributed ‘a myriad of ducks, swans, pelicans and every variety of seafowl, darkened the water beneath us’. From all accounts, the Lakes and Coorong teemed with fish and waterfowl during European settlement, but the initial sense of wonderment and discovery was short-lived and

rohan clarke

C o o R o n g L A g o o n s : e A R L y n At u R A L h i s t o R y A n d u s e o f n At u R A L R e s o u R C e s

109

Grey Teal quickly changed to one of exploitation. By the 1860s, fishermen and shooters were supplying fish and ducks to markets in Adelaide coupled with positive proclamations in the media.2 For example on 15 May 1866, The Advertiser reported that wildfowl and cod fish were abundant, the former in clouds upon the Lake. Other articles over the next two years noted that there were large quantities of wild geese (Cape Barren Geese) and that great numbers of them and other wildfowl were being shot. A duck canning factory even established about 15 kilometres from Meningie in the early 1890s,3 where wild ducks, mainly teal, were canned after being shot. This factory operated for

Professional duck-shooter on Lake Albert ca.1910 Image courtesy of the State Library of South Australia PRG 1258/2/1032

110

Lydia Paton

only a couple of years,4 and only during the six month open season for duck. Ducks were in their thousands then, breeding anywhere around swamps, out in the tall grass, in the scrub and also in the reeds and bulrushes around Lake Albert.5 Professional duck-shooters continued to hunt in the Coorong region until the early 1920s but there were growing concerns about the status of duck populations and various restrictions were introduced, including the banning of punt guns. Punt guns were large shot guns that could deliver around 500g of shot at a time and so could kill or maim 50-100 ducks in a single shot. Punt guns were very effective wherever ducks congregated, such as the freshwater seeps and soaks along the Coorong. Here, the effectiveness of a punt gun could be further enhanced by digging a narrow channel to pond some of the fresh seepage water, which the ducks would then congregate at, literally becoming ‘sitting ducks’. Various other legislative initiatives were taken to provide some havens for waterfowl within the Coorong. In 1908 the Birds Protection Act 1900 was applied to some of the islands in the Coorong and, from 1914 onwards, this Act was extended to include some of the waters of the Coorong.6 The Animals and Birds Protection Act 1919 was used to close the waters and islands

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

A pair of Australian Shelduck in flight (except Cattle Island) of the southern Coorong to the shooting of birds in 1920.7 Following this, local people put pressure on the government to lift restrictions on duck-shooting in the southern Coorong. By May 1923 there were two closed areas left in the southern Coorong, one from the Needles to Parnka, and another from Woods Well to Policeman Point.8 From 1925 the sanctuary area was changed to cover the area from The Needles to Stony Well.9

Arthur Grosset

from February to June. The Coorong Game Reserve was in the South Lagoon and ran from approximately Jack Point (about 2km north of Policeman Point) to almost Tea Tree Crossing. The area excluded some of the islands on which pelicans bred, including a buffer of about 150m around each. The Game Reserve was eventually abolished in January 1993. Only three other

In the years that followed, the government banned the sale of game, reduced the length of the open season, brought in a recreational game shooters’ limit on the number of ducks that could be bagged in a day and changed tactics by setting aside selected areas where hunting was permitted, as opposed to setting aside areas where hunting was prohibited. Nevertheless, duck-hunting continued in the Coorong until the 1990s, but was restricted to the Coorong Game Reserve from 1968 onwards. Much of the Coorong was declared a National Park in 1966, while the Coorong Game Reserve was gazetted in 1968. Duckhunting was permitted within the Game Reserve during a declared open season, typically running

Duck carcasses following a duck-shoot in the early 21st Century in the South East Nicholas Birks

C o o r o n g la g o o n s : e arl y n a t u ral h i s t o r y a n d u s e o f n a t u ral r e s o u rc e s

111

Game Reserves remain within the Coorong and Lower Lakes region, all in Lake Alexandrina: Tolderol Game Reserve, Currency Creek Game Reserve and Mud Islands Game Reserve. Duck-hunting per se was unlikely to be the cause of the decline in ducks within the region and several other factors were more likely causes; the ongoing drainage of the extensive areas of freshwater swamps across the South-East of South Australia (and beyond); changes in flows down the Murray affecting the fringing wetlands along the Murray; changes to the hydrology of the Lower Lakes following the construction of the Barrages; and the arrival of foxes in the region in the late 1880s. These changes drastically reduced the area of breeding habitat as well as the quality of that habitat, and opportunities for the ducks to breed were reduced further because the frequency of flooding, a key stimulus for breeding for some waterbirds,10 was also reduced.

“Mulloway died in hundreds but the water was by then so salty that they did not decay, but were pickled...” The above causes for the reduction in duck populations in the Coorong region were certainly the opinion of Sam (Laurie H.) Mincham, born in 1885, who grew up and lived in the Meningie district and even tried his hand at duck-hunting. He provides a retrospective view written as an octogenarian in 1966 of some of the changes that he had noticed since his childhood in both the Lakes and Coorong.11 He concluded that by the 1960s ducks were scarce in the district, that up until then sanctuaries had been mostly a farce, and that duck-hunting had almost become a sport, with at times hundreds of ducks being shot and left to rot. At the time, Mincham thought that the whole of the Hummocks and western shore of the Coorong (that is the Younghusband Peninsula) should be

112

declared a sanctuary to protect bird life. The government of the day clearly concurred. Mincham also provides some insights into some of the changes and dynamics that took place within the Coorong. The Coorong is salt, being directly connected to the sea, and in the early days it maintained a fair supply of sea fish. There were weeds growing from the shore out to the channel, thus providing areas of thousands of acres for sea fish to spawn in, and there were plenty of sea fish in the Coorong. But in later dry years, with a low tide and southern winds blowing the water back to the channel, the Coorong became so low that you could walk over it in many places. The hot sun soon dried and killed the exposed weed. Mulloway died in hundreds but the water was by then so salty that they did not decay, but were pickled. Most of the fresh water soaks also dried up, and the young swans died in hundreds for want of water. But a favourable year or two would allow an extensive regrowth of weed and the Coorong to return to normal. The warm, shallow water and abundance of weeds made the Coorong an ideal spawning ground for fish. Years later when the Coorong became exceptionally low, crabs came through the Murray Mouth in millions. It was not long before they had eaten most of the weeds, which made it easier for the fishermen to use their gill nets. Then, within a few years the crabs took over completely, playing havoc with the nets and costing the fishermen hundreds of pounds by their destruction. Today [1966] they have to keep their nets well clear of the bottom or the crabs will ruin them.12 Although there are no dates or locations for his observations, and some of the interpretations like the crabs eating all the plants may not be correct,

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

George and Andy Ross with a catch of Mulloway, 1934 Image courtesy of the State Library of South Australia PRG 1258/2/184

Mincham provides important insight into the ecology of the Coorong – one of an ecosystem that changes, perhaps back and forth between different states, depending on the conditions, most notably linked to changes in water levels and salinities. One of the very dry periods mentioned by Mincham may have been in 1939. Noye reports that fishermen had indicated to him that there were very low water levels during the extremely hot summer of 1939, with abnormally high salinities and temperatures, such that most of the aquatic plants and animals, at least in the northern basin of the South Lagoon, died.13 Interestingly, 1939 was a year in which very high tonnages of fish were caught, perhaps because the fish were restricted to the lower salinities that only existed in the northernmost parts of the northern Coorong.

Fishing the Coorong Olsen provides a summary of the early development of the fishing industry in the Coorong and Lower Lakes region and, although fishing enterprises began in 1846 (with two people selling fish caught near the Murray Mouth), commercial development of the industry was initially slow, due to poor transport, storage and refrigeration facilities.14 With the advent of better transport (steam rail services from Goolwa and Milang to Adelaide from 1885), the industry grew from supplying 85 tonnes of fish to the

Catch of Mulloway from Nine Mile Point, 1934 Image courtesy of the State Library of South Australia PRG/1258/2/173

Adelaide market in 1887, to around 167 tonnes in 1908, 209 tonnes in 1912 and a peak of over 1,000 tonnes in 1939.15 In 1939, the fishery accounted for more than half of the total South Australian catch of marine scale fish. Mulloway and Yellow-eyed Mullet were the major species harvested, with 595 and 446 tonnes caught in 1939 respectively.16 The quantity of fish harvested today is reduced, with around 150-200 tonnes of Yellow-eyed Mullet and 50-100 tonnes of Mulloway harvested annually, primarily from the Coorong.17 Other commercially harvested species include Black Bream and Greenback Flounder, but the tonnages of these species are smaller in comparison to the other species, in recent years rarely exceeding 10 and 20 tonnes respectively.

C o o r o n g la g o o n s : e arl y n a t u ral h i s t o r y a n d u s e o f n a t u ral r e s o u rc e s

113

Pelicans in the Coorong

F

or many people, pelicans are synonymous with the Coorong. Approaching the Coorong and lakes from Tailem Bend, the ‘V’-shaped formations of pelicans lazily floating to and from their feeding areas are seen long before the waters come into view. The book and film of ‘StormBoy’ further cemented this link between the wild landscapes of the Coorong and this iconic bird.

witnessed the aftermath of one such episode, where hundreds of young pelican bodies remained after their heads had been removed for the one penny bounty. White and other ornithologists lobbied the government to remove the bounty and, to further protect the pelicans, the South Australian Ornithological Association (SAOA) obtained a lease over their breeding islands.

The Coorong is a special place for pelicans as it represents their only regular historic breeding location in South Australia. Pelicans came into conflict with fishermen early in the colony’s history and massacres of birds occurred in the 1870s, alarming John Mellor who noted a marked decline in numbers in the Coorong.1 As recently as the early years of the twentieth century, the South Australian government paid a bounty on pelicans and cormorants. This was due to the belief that these birds competed for fish with commercial fishermen. Captain SA White, visiting the Coorong in 1918,

The lease, known as Licence 662 and secured in 1911, proclaimed the islands as bird sanctuaries. Signs to this effect were erected and the first caretaker, the aptly named Mr Goldfinch, was appointed. All went well until he was called up for active service and until 1919 there was a succession of local people enlisted as honorary caretakers by the SAOA to look after the bird-life on the islands and to assist in bringing offenders to justice. Some custodians took their role more seriously than others and mention is made in the SAOA Correspondence for 1918 of a meeting with the government over rumours that their recommended custodian had entered into partnership with a shooter, raising doubts about his suitability. Captain White investigated in person, meeting with Mounted Constable Kaine from Meningie, who he described as ‘an energetic officer and friend of the birds’. In company with the caretaker, Mr Appelkamp, who appears to have taken his role very seriously, White visited Pelican Island and described the experience thus:

Australian Pelican

114

Paul Wainwright

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

‘It was a fine sight to see so many pelicans. They were of all ages, from squabs not long hatched, to many ready to leave the island, and there were also many old birds watching over their young. I examined much of the food which had been vomited up by the young birds in their agitation, and found that there was not one marketable species of fish amongst the lot, the bulk of the food being

imported golden carp, a useless fish, and amongst them a few congolly [sic].’2 At least from 1919 onwards, the SAOA paid a fee of one shilling per annum for their annual licence to occupy the Coorong islands. Despite the proclamation of the breeding islands as bird sanctuaries, depredations on pelicans, their young and eggs, continued through at least to the 1960s. Condon, writing in 1939, documented that many times from the mid-1920s young pelicans were clubbed and trampled to death, but with no reliable informants, no prosecutions Australian Pelicans flying in formation eventuated.3 Licence Number 662 was held continuously by the Association until 1962, when it was cancelled. At this time the government declared the islands prohibited areas and gave full protection to the species in South Australia. This action followed widespread newspaper publicity of destruction of pelican eggs in September 1962.4

daVid Paton

“the ‘V’-shaped formations of pelicans lazily floating to and from their feeding areas are seen long before the waters come into view...”

B� P���� P����

1.

FRH Chapman, ‘The pelican in South Australia’, in South Australian Ornithologist, 24 (1963): 6-14.

2.

SA White, ‘A visit to the breeding grounds of swan and pelican on the Coorong’, in South Australian Ornithologist, 3 (1918): 198-200.

3.

HT Condon, ‘Young pelicans’, in Emu 41 (1941): 92-3.

4.

Chapman, ‘The pelican in South Australia’, 6-14.

Reductions in the quantities of fish being harvested from the Coorong since the 1940s are attributed to the construction of the Barrages, that drastically reduced the available nursery habitats for fish like Mulloway, and reductions in the frequency and volumes of fresh water flowing to the Mouth. Coorong fishermen knew that during a year when the River Murray flooded, the Barrage gates were kept open longer and often through summer, such that well into summer, water levels and salinities in the Coorong remained little changed from those of winter. During these periods, the growth of water weed was greater than normal and subsequently fish more plentiful.18

C o o R o n g L A g o o n s : e A R L y n At u R A L h i s t o R y A n d u s e o f n At u R A L R e s o u R C e s

115

A school of young Yellow-eyed Mullet According to Noye, during the 1930s and 1940s, many professional fishermen made a living by netting fish in both lagoons of the Coorong.19 By the 1960s, only a few of them made a living in the South Lagoon, with most fish being caught in the North Lagoon. However, the catch in the North Lagoon was generally poor when there was an influx of fresh water released over the Barrages. At these times, fishermen at the north end of the South Lagoon generally caught more fish, while fishing in the North Lagoon was generally better at times of low water levels, when the salinity was one to one and a half times that of sea water. Today the Coorong and Lakes fishery is well managed with a suite of regulations in place to control both commercial and recreational activities; minimum sizes for fish that can be taken, specifications for type and quantity of gear that can be used (for example, mesh sizes and lengths of net), seasonal closures of parts

116

Nicholas Birks

of the Coorong, plus bag limits for recreational fishers.20 Regulations have been part of the fishery since the late 1880s, when limits on the sizes of Mulloway that could be taken were first introduced. In 2008, the Coorong and Lakes fishery secured Sustainability Certification accredited by the independent Marine Sustainability Council. In the future, regular stock assessment should facilitate the maintenance of a sustainable fishery.21 However, sustaining harvest rates does not mean that the commerciallyharvested fish are largely unaffected by a lack of flow to the Mouth region. Although Yelloweyed Mullet populations appear secure, there is concern that recruitment for Mulloway has been greatly reduced with the reductions and cessation of environmental flows since the mid 1990s.22 Despite the historical success of the industry, fishing interests were blamed for the regular raids on the breeding colonies of pelicans in the South Lagoon of the Coorong. Early on, pelicans were

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

considered to compete with fishermen for fish, not helped by the pelicans’ habit of regularly taking fish from fishing nets. In retribution, the breeding colonies of pelicans on islands in the southern Coorong were regularly raided, the eggs smashed, and young clubbed or trampled to death. The earliest massacres occurred in the 1870s and continued until the 1960s. At one stage, the State government offered a bounty for pelicans. The South Australian Ornithological Association took an active interest in trying to protect the birds from the early 1900s onwards, leasing the islands on which the pelicans bred for many years and lobbying to have the islands declared as sanctuaries to prohibit access. A flotilla of pelicans

Coorong fisherman

Paul Wainwright

Paul Wainwright

C o o r o n g la g o o n s : e arl y n a t u ral h i s t o r y a n d u s e o f n a t u ral r e s o u rc e s

117

Aquatic macrophytes in the Coorong The prominence of water weeds was one of the key components of the biota that was mentioned regularly in accounts of the Coorong prior to the 1980s. In addition to the observations of Mincham and reports of Noye, others also commented on the abundance of water weeds. Sutton, travelling south along the Coorong in March 1925, noted that Swan Grass was first encountered near an extensive exposed sandspit on the western side of the Coorong opposite Dodd Landing Point (a little south of Long Point).23 Here, the Swan Grass was visible along the water’s edge. On the southern side of the spit was an extensive bay with a great quantity of Swan Grass and with large numbers of wading

birds along the shallow western end. Swan Grass became so dense further south of this point that it clogged the propeller of the launch, which turned back after travelling another 1-2km and before reaching Sam Island (about 1km north of Noonameena). Sutton went on to remark that Swan Grass so fouls the fishermen’s nets that fishing south of this point is practically impossible. Sutton referred to Swan Grass by the generic name of Zostera, but this may have been an error since swans are not known to feed on Zostera, but are known to feed on a wide variety of other plants, including the foliage of Ruppia.24 The importance of aquatic plants to waterfowl was highlighted by Delroy. Delroy collected samples of waterfowl in the southern Coorong in 1965-66 and found that Grey Teal, Chestnut

Pelican chick on an island in the South Lagoon

118

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Daniel Rogers

The breeding biology of pelicans

T

he Coorong is the only historic location in South Australia to support regular breeding of Australian Pelicans. This is probably due to their very specific requirements for ‘an undisturbed site with abundant and assured food supply for 3 months for successful colonial breeding’.1 Pelicans nest on the group of six islands, loosely called the pelican islands, which lie between Jack Point and Policeman Point, and Seagull Island south of Policeman Point, in the South Lagoon. These limestone islands range from less than a hectare to about five hectares. They are generally vegetated with small salt-tolerant plants, but the larger islands support some taller plants like African Boxthorn.2 Those parts of the islands where pelicans congregate become denuded over the period of the breeding season.

Pelican chick crèche

daVid blair

Information on pelican breeding in the Coorong is based mainly on single and infrequent visits, so data on breeding ecology, population size and breeding success are incomplete. Paton summarized information to the early 1980s, concluding that adult numbers sometimes reached 3-4000, and numbers of eggs and chicks varied from 500 to 2000, from 1910 to 1965.3 The 1981-82 breeding season was an excellent one and, while no counts were made, Seagull and North Pelican Islands supported large numbers of breeding birds.

Chapman stated that breeding occurred between June and March, with egg-laying varying from season to season and within any one season.4 The following general breeding information is from Marchant and Higgins.5 Nests are placed on the ground in shallow depressions and are encircled or sparsely lined with plant or animal material, sometimes even dead birds. Clutch size varies from one to three eggs, with two being the most common. When first hatched, the pink and naked chicks are brooded continuously by the adults, but by four weeks of age the down-covered chicks form crèches of up to 30 birds. Crèches move about and vary in size depending on the number of parent birds coming to feed. At two months the young are nearly as large as adults, testimony to their nutritious fish diet. Young leave the crèche at about three months when their first attempts at flying are made.

B� P���� P����

1.

S Marchant and PJ Higgins, Handbook of Australian, New Zealand and Antarctic birds. Volume 1. Ratites to ducks, Part B Australian Pelican to ducks (Melbourne: Oxford University Press, 1990), 744-5.

2.

FRHChapman, ‘The pelican in South Australia’, South Australian Ornithologist, 24(1963): 6-13.

3.

P Paton, Biota of the Coorong (Adelaide: SA Department of Environment and Planning, 1982), 20.

4.

Chapman, ‘The pelican in South Australia’, 10.

5.

Marchant and Higgins, 1990, 744-5.

C o o R o n g L A g o o n s : e A R L y n At u R A L h i s t o R y A n d u s e o f n At u R A L R e s o u R C e s

119

Teal and Australian Shelduck largely consumed the tubers (turions) and seeds of ‘Widgeon Grass’ (Ruppia spiralis) and tubers of Musk Grass.25 However, the species of Widgeon Grass was likely to be a different species26 and Delroy’s photograph,27 of the turions taken from the

Ruppia tuberosa turions from a duck’s oesophagus Lawrie Delroy

oesophagus of the ducks, identifies the species as Ruppia tuberosa. The ducks harvest the turions by dabbling just below the surface of the mud when the mudflats are covered with shallow water, the dabbling often leaving large numbers of small potholes or indentations on the muddy surface. Both Delroy and Womersley provided additional information on the biology of these aquatic plants. For example, Delroy noted that Widgeon Grass and Musk Grass both produced dense vegetative growth in the brackish waters of Salt Creek (with salinities up to 20g/L), but Widgeon Grass produced no tubers and Musk Grass only a few in these conditions.28 In hypersaline (>35g/L) conditions (above those of sea water), both plants produced tubers. Widgeon Grass continued to grow in salinities greater than 71g/L but Musk Grass failed to grow satisfactorily when salinities exceeded 60g/L. Womersley added to this by indicating that in laboratory trials, Widgeon Grass grew well in water temperatures of 12oC, but good tuber production only occurred when water temperatures were at 20oC and above.29 However, Musk Grass did not grow at 12oC but grew and produced tubers at temperatures of 16oC and 20oC. Delroy went on to indicate that the maintenance of appropriate water levels during spring was critical for the plants to complete their life cycles in the warmer temperatures of summer.30 When water levels did fall, large areas of Widgeon Grass were left exposed to the air and died. This was less of an issue for Musk Grass, which generally grew in deeper water.

Early counts of waterbirds

Sharp-tailed Sandpiper

120

Paul Wainwright

Although the Coorong is regarded as an important place for waterbirds, little quantitative data exist for birds prior to the 1980s. Most of the early ornithological work in the region focused on monitoring breeding birds on islands in the South Lagoon, particularly Australian

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Pelicans, but even then the counts of breeding birds were infrequent.31 White inspected some of the islands south of Hack Point probably in 1918, reporting dozens of Black Swans with nests built amongst clumps of tussock grass.32 Sutton visited some of the same islands as White (as well as other islands also in the South Lagoon), in October 1932.33 Across the sixteen islands that were visited, he reported 579 active nests of Silver Gulls, 233 for Black Swans, 300 for Australian Pelicans, 195 for Fairy Terns, 48 for Caspian Terns and 24 for Pied Cormorants. Sutton also recorded the occasional nests of Pied Oystercatchers (4), Hooded Plover (2), Redcapped Plover (4), Masked Lapwing (1) and Australian Shelduck (2) on these islands. Signs of foxes were seen on several of the islands, and most had rabbits. A large flock of 50,000 Banded Stilt was also present near the islands off Hack Point. Most of the available historic information on the waterbirds in the Coorong is for breeding birds. In good years, 3,000 to 4,000 Australian Pelicans nested on islands near Policeman Point.34 Although the numbers of birds and timing of breeding varied, breeding occurred regularly, if not annually, any time between June and March. This breeding colony seems remarkably resilient, persisting for more than 100 years, despite regular disruption to nesting when eggs and chicks were destroyed by fishermen, the raids continuing into the 1960s.35 The colony remains the only permanent breeding colony of pelicans in South Australia. For pelicans, much of the food provided to chicks is collected from the Lower Lakes and includes non-commercial fish such as Goldfish, as noted by White.36 During breeding, flotillas of pelicans are commonly seen flying to and from the breeding colonies and the northern Coorong and Lower Lakes. Pelicans banded as nestlings in the Coorong also disperse widely; birds have subsequently been recovered at locations within South Australia,Victoria, New South Wales, Queensland, the Northern Territory and as far away as Papua New Guinea.37

Pied Oystercatcher nest

Daniel Rogers

Juvenile (left) and adult (right) Pied Oystercatcher Chris Tzaros

Other species to regularly breed in colonies on islands in the southern Coorong include Crested, Caspian and Fairy Terns plus Silver Gulls. Of these species, Crested Terns have shown greater fidelity to one or two islands, with between 4,000 and 8,000 birds breeding regularly on Stony Well Island during the 1960s and 1970s.38 The lack of early systematic counts of waterbirds is not surprising given the lack of easy access to many parts of the Coorong and the size of the wetland. Perhaps what is surprising is that the early ornithologists who visited the Coorong rarely remarked that they had seen large numbers of waterbirds and, if they did, the numbers were often couched in qualitative terms. For example, White noted in 1918 that the Coorong lagoon opposite Magrath Flat was covered in wildfowl, swans in thousands, mountain ducks, black ducks

C o o r o n g la g o o n s : e arl y n a t u ral h i s t o r y a n d u s e o f n a t u ral r e s o u rc e s

121

Caspian Terns breeding on an island in the South Lagoon Lyall Howard

and teal in countless numbers but the overall area over which the observations were based and the exact date were not provided.39 Sutton reported some thousands of smaller waders feeding on the mudflats on the south-east side of Tauwitchere Island in early March 1925, including Rednecked Stints, Sharp-tailed Sandpipers, Curlew Sandpipers and Red-capped Plovers. Sutton also noted flocks of waders on mudflats along the

North Lagoon.40 He provided a summary of the birds seen during a four-day visit to the northern 20km of the North Lagoon and Tauwitchere Island in March 1925, tallying 3,057 Red-necked Stints, 773 Sharp-tailed Sandpipers, 102 Curlew Sandpipers and 922 Red-capped Plovers. Sutton also provided counts of waterfowl seen during the same trip, indicating that there were in excess of 1,300 Black Swans, 2,300 Australian Shelducks and 500 Pacific Black Ducks within this region. These counts in the northern Coorong do not suggest vast numbers of waterbirds were present in that year. However, Delroy suggested that there were two million ducks in the Coorong in 1964-5,41 presumably deriving this estimate by extrapolating counts of ducks from a small section of the Coorong. In the following year, the estimate was only about 200,000 ducks in the Coorong. Those figures contrast with the view of Mincham, who commented in 1966 that ducks were now scarce in the Coorong. The only other substantial number of birds reported

Crested Terns breeding on an island in the South Lagoon

122

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Lyall Howard

was an agglomeration of around 250,000 small waders seen by John Eckert between Tauwitchere Barrage and the Murray Mouth in October 1967.42 The birds were predominantly Rednecked Stints, but large numbers of Curlew and Sharp-tailed Sandpipers were also present. Although the counts of birds within the Coorong have been patchy and fragmented, over eighty species of waterbirds have been recorded using the Coorong and, of these, more than 40 species were regularly seen and considered to be common or abundant. Twenty of the eighty species were migratory waders from the Northern Hemisphere. Couple this with the occasional reports of large numbers of waterbirds and regular breeding of species like the Australian Pelican, and one can justify the early basis for the Coorong’s reputation as an important haven for waterbirds.

By the 1970s, although there was a sense that the system had changed or was at risk of changing because of higher salinities, there was little or no quantitative historical data by which those concerns could be assessed. As a result, most reports were cautious in suggesting that there had been any significant changes.43 Those concerns, however, gave rise to more detailed studies in the 1980s.

Red-necked Stints

Male Red-capped Plover

Chris Tzaros

Chris Tzaros

C o o r o n g la g o o n s : e arl y n a t u ral h i s t o r y a n d u s e o f n a t u ral r e s o u rc e s

123

Sunset over Coorong National Park

124

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Paul Wainwright

1.

George French Angas, Savage Life and Scenes in Australia and New Zealand Volume 1 (London: Smith, Elder and Company, 1847).

24. S Marchant and PJ Higgins, Handbook of Australian, New Zealand and Antarctic Birds. Volume 1. Ratites to ducks, Part B Australian Pelican to ducks (Melbourne: Oxford University Press, 1990), 1180–1.

2.

LH Mincham, ‘Sam’s memoirs of Meningie district’, in The Coorong and lakes of the Lower Murray, Tom McCourt and Hans Mincham (Adelaide: Beachport Branch of the National Trust, 1987), 152–71.

25. LB Delroy, ‘The food of waterfowl (Anatidae) in the southern Coorong saltwater habitat of South Australia’, in South Australian Ornithologist, 26 (1974): 157-163.

3.

Mincham, ‘Sam’s memoirs of Meningie district’, 166.

4.

Department of Environment and Planning, Draft Management Plan: Coorong National Park and Game Reserve (Adelaide: Department of Environment and Planning, 1984), 70, 73.

5.

Mincham, ‘Sam’s memoirs of Meningie district’, 155.

6.

Department for Environment and Planning, 1984, 71.

7.

The Express, 30 January 1920.

8.

The Advertiser, 9 May 1923.

9.

Department for Environment and Planning, 1984, 71.

10. HJ Frith, Waterfowl in Australia, Revised edition (Sydney: Angus and Robertson, 1982). 11. Mincham, ‘Sam’s memoirs of Meningie district’, 152-71. 12. Mincham, ‘Sam’s memoirs of Meningie district’, 156. 13. BJ Noye, ‘Waters of the Coorong Lagoons’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 59-79. 14. AM Olsen, The Coorong – A multi-species fishery. Part 1 – History and Development (Adelaide: Department of Fisheries, 1991). 15. Olsen, The Coorong – A multi-species fishery. 16. Olsen, The Coorong – A multi-species fishery. 17. Sean Sloan, Management plan for the South Australian Lakes and Coorong fishery. The South Australian Fisheries Management Series paper number 44 (Adelaide, Primary Industries and Resources South Australia, 2005). 18. Noye, ‘Waters of the Coorong Lagoons’, 73. 19. BJ Noye, Fishing in the Coorong’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 89-103. 20. Sloan, Management plan for the South Australian Lakes and Coorong fishery. 21. Sloan, Management plan for the South Australian Lakes and Coorong fishery. 22. Greg Ferguson, Tim Ward and Michael Geddes, ‘Do recent age structures and historical changes in catches of mulloway, Argyrosomus japonicas (Sciaenidae), reflect freshwater inflows in the remnant estuary of the Murray River South Australia?’ in Aquatic Living Resources, 21 (2008): 145-152.

26. HBS Womersley, ‘Plant life in the Coorong lagoons’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 81–88. 27. Delroy, ‘The food of waterfowl (Anatidae) in the southern Coorong saltwater habitat of South Australia’, 162. 28. Delroy, ‘The food of waterfowl (Anatidae) in the southern Coorong saltwater habitat of South Australia’, 158. 29. Womersley, ‘Plant life in the Coorong lagoons’, 86. 30. Delroy, ‘The food of waterfowl (Anatidae) in the southern Coorong saltwater habitat of South Australia’, 163. 31. P Paton, Biota of the Coorong. (Adelaide: SA Department of Environment and Heritage, 1982), 20–1. 32. SA White, ‘A visit to the breeding grounds of swan and pelican on the Coorong’, in South Australian Ornithologist, 3 (1918): 198–200. 33. J Sutton, ‘Inspection of some island-sanctuaries in the Coorong’, in South Australian Ornithologist, 12 (1933): 19–28. 34. FRH Chapman, LB Delroy and BJ Noye, ‘Aquatic birds of the Coorong’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 105–18. 35. FRH Chapman, ‘The pelican in South Australia’, in South Australian Ornithologist, 24 (1963): 6–13. 36. White, ‘A visit to the breeding grounds of swan and pelican on the Coorong’, 198–200. 37. Marchant and Higgins, 1990, 741. 38. Paton, Biota of the Coorong, 23. 39. White, ‘A visit to the breeding grounds of swan and pelican on the Coorong’, 198-200. 40. Sutton, ‘A trip to the Coorong’, 75–95. 41. LB Delroy, PM Macrow and JB Sorrell, The food of waterfowl (Anatidae) in salt water habitats of South Australia (Adelaide: Unpublished report of Fisheries and Fauna Conservation Department of South Australia, 1967). 42. Paton, Biota of the Coorong, 15–16. 43. Noye, ‘Waters of the Coorong Lagoons’; Womersley, ‘Plant life in the Coorong lagoons’; Chapman, Delroy and Noye, ‘Aquatic birds of the Coorong’; Paton. Biota of the Coorong.

23. J Sutton, ‘A trip to the Coorong’, in South Australian Ornithologist, 8 (1925): 75–95.

C o o R o n g L A g o o n s : e A R L y n At u R A L h i s t o R y A n d u s e o f n At u R A L R e s o u R C e s

125

Pelican landing

126

Coorong Lagoon shore-line

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Paul WPainwright eter Bird

ChApteR 7

The Coorong Lagoons: Biotic responses to a changed hydrology

B

aSed on natural hiStory oBServationS

up until the 1980s, salinity and water level stand out as two key drivers in the ecology of the Coorong lagoons. Salinities typically increase along the Coorong from north to south, vary seasonally and often fluctuate from one year to the next, depending on freshwater flows to the Murray Mouth. Most of the ecological studies from the 1980s onwards aimed to strengthen the relationship between salinity (and to a lesser extent water levels) and the distribution of aquatic plants and animals taking advantage of the salinity gradient along the Coorong lagoons. This chapter provides a summary of those studies that have explored patterns to the distributions and abundances of aquatic plants, invertebrates and fish along the Coorong. The distributions and abundances of birds are covered in the following chapter. Birds are only partially influenced by hydrological changes and more likely to be influenced by changes in their aquatic food resources, which are potentially sensitive to salinity and water level changes.

Amphipod (~3mm long) from the Coorong lagoons

Scott MillS

Small crab from the Coorong lagoons

Scott MillS

aquatiC inVertebrates and fish in the Coorong The initial research of limnologists, such as Mike Geddes, explored relationships between the distributions and relative abundances of aquatic macro-invertebrates and salinity. Macroinvertebrates are invertebrates like polychaetes, crustaceans and snails that are typically at least 1mm in size and visible to the naked eye. Geddes’ work was based primarily in the North Lagoon where he repeatedly sampled nine sites spread

Polychaete worm (Capitella sp.) (~5mm long) from the Coorong lagoons Scott MillS

the CooRong LAgoons: biotiC Responses to A ChAnged hydRoLogy

127

evenly along 32km of the lagoon from Mark Point to The Needles. He also visited sites in the South Lagoon though less frequently. There was a marked salinity gradient along the northern section of the Coorong, and the salinity changed through time. This allowed the salinity tolerances of many of the macro-invertebrates to be assessed. At the start of the study (December 1981) salinities ranged from 20-50g/L along the North Lagoon, while at the end of the first year (January 1983) they ranged from 40-80g/L, corresponding to a period when negligible water was released over the Barrages.1 Geddes continued to monitor the biota along the North Lagoon during the following two years but not as frequently. During these two years, water was released over the

Barrages (primarily during winter and spring) and the salinities dropped, such that they were typically in the 5-35g/L range for much of 1984.2 In the 1980s, macro-invertebrates in the North Lagoon were dominated by three species of amphipods (Melita zeylanica, Paracorophium sp. and Megamphopus sp.), four species of polychaete (Simplisetia aequisetis, Nephtys australiensis, Capitella sp. and Ficopomatus enigmaticus), two bivalves (Notospisula trigonella and Arthritica helmsi) and two gastropods (Hydrobia buccinoides and Salinator fragilis). All of these invertebrates were present at the five northernmost sampling sites used by Geddes throughout 1982, as well as 1983 and 1984. The salinities at these sites did not exceed

Polychaete worms in the Coorong

P Simplisetia jaws

SaBine dittMann

olychaete worms, also known as bristleworms, are so named because of the fleshy protrusions from their body which bear many bristles, or chaetae (Poly = many, chaetae = long hairs/ bristles). They are abundant, typically marine organisms found throughout the world’s oceans and estuaries. There are at least seven species of polychaete worms that inhabit the mudflats of the Murray Mouth and northern lagoon regions of the Coorong. One species, Capitella sp., despite being less than 10mm in length, is present in enormous numbers: sometimes over 30,000 per square metre. Capitella is a deposit feeder, essentially eating the mud that it lives in, extracting any algae, organic detritus and other nutrients. It is able to withstand low oxygen levels and is frequently an indicator of organically-enriched (and sometimes polluted) environments. Another common polychaete in the Coorong is the predator Nephtys australiensis. This species actively hunts its prey of other small polychaete worms (such as Capitella) and small bivalves. It is much larger than Capitella, reaching maximum lengths of approximately 30mm. Simplisetia aequisetis is another larger polychaete (up to 20mm length) that is common in the marine section of the Coorong. However, it is a scavenger or opportunistic feeder and bears a powerful set of jaws. The large opportunistic feeder, Phyllodoce novaehollandiae, everts, or vomits out, its muscular pharynx, which grabs on to the food source (including other small polychaete worms such as Capitella), before being sucked back in for digestion.

B� A��� R������ Polychaete bristles or ‘chaetae’

128

SaBine dittMann

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

58g/L and were lower than those further south. At the sites further south, most of these species were present when salinities were below 60g/L but by summer, when the salinities exceeded 60g/L, many had disappeared. Most estuarine invertebrates can tolerate salinities up to about 55-60g/L. Only Capitella and Salinator, which can tolerate salinities up to 70-80g/L, remained prominent at the southernmost sites in the North Lagoon in 1982. At these sites, the aquatic stages of two species of Diptera were also prominent – the chironomid or midge (Tanytarsus barbitarsis) and the brine fly (Ephydrella sp.). Both of these species can tolerate salinities of at least 100g/L and were consequently also widespread in the South Lagoon. Salinities in the South Lagoon were often in the range of 80-100g/L, but in autumn salinities at the southern end of the South Lagoon exceeded 120g/L during the period of Geddes’ studies. Two other invertebrates were also prominent in the higher salinities of the South Lagoon, the isopod Haloniscus searlei and the ostracod Diacypris compacta3 (Fig. 7.1).

Congolli

Several species of small fish were also sampled in the hand nets used by Geddes in 1982-84. The three common species were primarily caught amongst submerged aquatic vegetation, particularly Ruppia. The Western Blue Spot Goby and Bridled Goby were only caught in the North Lagoon, in water with salinities up to about 70g/L. However, Small-mouthed Hardyheads were detected at all sites, being prominent in the higher salinities at the southern end of the North Lagoon and throughout the South Lagoon, where the species was very abundant and the only small fish detected. The number of species of aquatic invertebrates found in the northern Coorong, relative to other estuaries in Australia and around the world, was generally poor, perhaps reflecting the greater range of salinities in the North Lagoon of the Coorong, where at times salinities increased well above those of sea water.4 However, the North Lagoon areas sampled by Geddes were more than 10km from the Murray Mouth and

Scotte Wedderburn

T h e C o o r o n g la g o o n s : b i o t i c r e s p o n s e s t o a c h a n g e d h y d r o l o g y

129

F

7.1 Salinity tolerances of selected aquatic organisms in the Coorong DIPTERA

Ephydrella sp.  Tanytarsus barbitarsis  Arthritica helmsi  Salinator fragilis  Hydrobia buccinoides  Capitella sp.  Ficopomatus enigmaticus  Nephtys australiensis  Simplesetia aequisetis   Diacypris compacta  Paragrapsus gaimardii   Melita zeylandica  Haloniscus searlei  Macrobrachium intermedium  Tamar River Goby  Small‐mouthed Hardyhead  Congolli  Greenback Flounder  Yellow‐eyed Mullet  Mulloway  Black Bream  Bony Herring  Common Galaxias 

BIVALVA GASTROPODA POLYCHAETA

CRUSTACEANS

FISH

0 

50 

100 

150 

Salinity (g/L)  Salinity tolerance ranges (g/L) for key species in the Coorong. Data are based on Dittmann et al. 2006; Geddes and butler 1984; Noell et al. 2009 (see endnotes for full reference).The salinity tolerances are a guide only.They are based on the salinities at which organisms have been detected.They do not consider if organisms can reproduce across the range of salinities.Temperatures modify salinity tolerances and temperature effects have not been considered.

130

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

at least 5km from the Barrages, and so would be expected to differ from the typical salinities of an estuary. Although Geddes did not collect quantitative data in these early studies and did not explore areas closer to the Murray Mouth, subsequent work since 2004 by Sabine Dittmann and colleagues assessed the abundances of the benthic invertebrates (those dwelling on or in the sediments) within the Murray Estuary, as well as the North and South Lagoons.5 This sampling was limited to sampling across the intertidal mudflats or an equivalent range of water depths in the southern Coorong. Species richness was highest within the Murray Estuary between the Goolwa Barrage and Pelican Point, with a variety of polychaetes, amphipods and molluscs present. Abundances were also high with >27,000 individuals/m2 within this region. Although these abundances are typical of other

Small-mouthed Hardyhead

estuaries, the biomass of invertebrates is about ten times lower, reflecting the small sizes of many of the invertebrates. The diversity and abundances of benthic invertebrates were much lower in the southern sections of the North Lagoon (particularly south of Long Point) and throughout the South Lagoon, where the lowest diversity and abundances of benthic invertebrates were found. In these southern sites, the only abundant benthic invertebrates were chironomid larvae, with densities of about 1,000 individuals/ m2. This pattern to the distribution and abundance of benthic invertebrates around the shore-lines of the Coorong was confirmed with further sampling in 2006 and 2007.6 However, in January and March 2007, there were no benthic invertebrates present in the South Lagoon when salinities were around 140g/L (Fig. 7.2).

Michael Hammer

T h e C o o r o n g la g o o n s : b i o t i c r e s p o n s e s t o a c h a n g e d h y d r o l o g y

131

F

7.2 Number of macro-invertebrate taxa found along the Coorong

12  North Lagoon 

Murray Estuary 

December 2006

South Lagoon 

Number of Species 

10 

Insecta  Bivalva 

8 

Gastropoda  6 

Crustacea  4 

Oligochaeta  Polychaeta 

2 

0  ‐5 

3 

4 

11 

20 

27 

37 

58 

61 

80 

91 

Distance from the Murray Mouth (km) 

12  North Lagoon 

Murray Estuary 

March 2007

South Lagoon 

10 

Number of Species 

Insecta  Bivalva 

8 

Gastropoda  6 

Crustacea  4 

Oligochaeta  Polychaeta 

2 

0  ‐5 

3 

4 

11 

20 

27 

37 

58 

61 

80 

91 

Distance from the Murray Mouth (km) 

Number of macro-invertebrate species found at 11 sampling sites along the Coorong in December 2006 (top) and March 2007 (bottom). Negative numbers (-5) are kilometres NW of Murray Mouth and positive numbers kilometres SE of Mouth. Data sourced from Rolston and Dittmann, 2009 (see endnote for full reference).

132

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Two patterns stand out from the work of Geddes in the early 1980s and confirmed by subsequent studies. First, the number of species of aquatic invertebrates was highest in the northern, more estuarine parts of the Coorong, where the salinities were lowest. The numbers of species then declined progressively as salinities increased, such that there were only a few species of highly salt-tolerant invertebrates present in the South Lagoon. Second, the distributions of many aquatic invertebrates in the northern Coorong expanded and contracted in response to decreases and increases in salinity, respectively. A similar pattern existed for fish. For example, Hall detected 16 species of fish using the North Lagoon in 1984, including several primarily freshwater fish like Common Carp, Bony Herring and Flathead Gudgeon, presumably washed in with the River Murray flow, and only likely to be temporary inhabitants.7 Three species, Congolli, Black Bream and Yellow-eyed Mullet,

F

that were normally restricted to the North Lagoon, also expanded their distribution into the South Lagoon in spring 1984, when salinities in the South Lagoon had dropped (ranging from 55-70g/L), with mullet extending as far south as Salt Creek. This incursion was short-lived and once salinities exceeded 70g/L none of these fish species was caught. Thus, a pattern was established, whereby the relative richness of fish species shifted from high to low along the salinity gradient of the Coorong. This trend was confirmed during systematic sampling along the Coorong during 2006-2008.8 During this period, 26 species of fish were sampled in seine nets within the Murray Estuary; however, only 13 of these were present in the more saline parts of the North Lagoon and just a single species, the Smallmouthed Hardyhead, existed in the South Lagoon at salinities up to 134g/L (Fig. 7.3). The Small-mouthed Hardyhead was also the most

7.3 Changes in the number of fish species along the Coorong

25  Murray Estuary 

North Lagoon 

South Lagoon 

Number of Fish Species 

20 

15 

10 

5 

0  ‐5 

5 

11 

17 

37 

58 

80 

92 

Distance from the Murray Mouth (km) 

Changes in numbers of species of fish caught at different locations along the Coorong using seine nets between October 2006 and September 2008. Negative numbers (-5) are kilometres NW of Murray Mouth and positive numbers kilometres SE of Mouth. based on data from Noell et al. 2009 (see endnote for full reference).

the CooRong LAgoons: biotiC Responses to A ChAnged hydRoLogy

133

Chironomids in the southern Coorong abundant small fish caught in the North Lagoon, accounting for 92% of the fish caught in seine nets. The next most salt-tolerant fish species were the Yellow-eyed Mullet, Greenback Flounder and Congolli, which were caught in salinities up to 74g/L, followed by the Sandy Sprat, which was found in salinities up to 69g/L. A suite of other species used water with salinities up to 60g/L, including Black Bream, Mulloway and Australian Salmon. All of these species were confined to the Murray Estuary and northern parts of the North Lagoon during the two year study.

Chironomid larva

T

Scott MillS

anytarsus barbitarsis is a midge or small fly about 3-4mm in length and is widespread and abundant near wetlands, particularly the Coorong. Adult midges are often attracted to lights in residential areas, but in the Coorong the adults are usually seen settled in coastal vegetation, or in the air in massive swarms or stacks that form a cloudy haze of tiny moving insects, usually on the lee side of some taller vegetation. These swarms consist predominantly of males. Females fly into these swarms to be mated. Once mated, females lay their eggs on the water and the eggs drop to the bottom, where they subsequently hatch. The larvae that hatch from these eggs live on the bottom in protective tubes, while grazing on surface algae. They are sometimes called bloodworms because they use haemoglobin to store oxygen. As they grow, the larvae must shed their skins multiple times, as they progress through four separate stages or instars, before eventually pupating. When the pupae are ready to hatch they float to the surface of the water where the adult midge emerges. The larval stages of the midges are a major source of food for aquatic birds and fish in the Coorong, while adults are also taken by aerial flycatchers like the Welcome Swallow. Larval stages usually last about 30 days, depending on water temperature, while the pupae may take 3 days to mature before hatching. Adult midges, however, only live for a few days.

B� M��� K������

134

Most of these aquatic organisms have some ability to shift their distribution moderately quickly in response to changes in salinity and water levels, with the organisms either capable of moving or having larval stages that are highly dispersive. Other components of these aquatic ecosystems, such as some of the aquatic plants, lack the ability to respond quickly to changes in salinity and water levels. The aquatic plants provide habitat for a range of invertebrates and fish, and also food for selected waterbirds, so how they respond to changes in salinity and water levels is critical to the ecological health of the Coorong.

Changes to the distribution of aquatiC PLants in the north Lagoon In the early 1980s, the North Lagoon (at least from near Mark Point to The Needles), supported extensive beds of Ruppia megacarpa, as well as Lepilaena cylindrica and Zostera muelleri.9 However, the latter two species were not as abundant or as widely distributed. In particular, Zostera was only found at the more northerly sites. The beds of Ruppia megacarpa and Lepilaena cylindrica were both particularly vigorous in October 1983, when they flowered profusely, particularly towards the southern end of the North Lagoon. They remained vigorous until June 1984 and then died back before becoming

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

vigorous again by December 1984, although no flowering was detected.10 These aquatic plants were usually present in water no deeper than 1m, but occasionally patches occurred in deeper water (up to 2m) in the middle of the lagoon. During the summer, mats of filamentous algae, including Cladophora, Enteromorpha and Oscillatoria, were also present in and amongst these macrophyte beds. Although no quantitative data were collected on the biomass of the plants during 1982-84, Snoejis and van der Ster estimated that the vegetative biomass within a typical bed of Ruppia megacarpa was around 240g (dry weight)/m2, while the associated filamentous algae accounted for 47g/ m2 in February 1981.11 These samples came from a site about 1km north of Robs Point in water that was no more than 45cm deep, and where the heights of the plants were no greater than 40cm. As such, they may underestimate the biomass of Ruppia megacarpa in deeper water where the plants were larger. Ruppia megacarpa is regarded as a perennial plant that does not produce tubers (turions) and only a modest number of seeds. In 1981, the seed banks within the Ruppia megacarpa beds contained about 1,100seeds/m2.12 During February and March 1981, the abundances of aquatic invertebrates in the Ruppia megacarpa beds were substantial13 and illustrate the importance of these aquatic plants in providing foraging opportunities and habitats for aquatic invertebrates. Gastropod densities were up to 35,000/m2 for Hydrobia buccinoides and up to 1,100/m2 for Salinator fragilis. The bivalve Arthritica helmsi had densities of up to 1,900/ m2, while two species of polychaete, Simplisetia aequisetis and Capitella sp. had densities of around 1,000 and 35,000/m2 respectively. The larvae of several Diptera were also present; there were up to 2,100 Tanytarsus barbitarsis larvae/m2, while two species of brine fly had about 3,800 larvae/ m2. Salinities at the time of sampling were 58g/L. On the basis of these findings, the Ruppia megacarpa beds were highly productive.

Ruppia tuberosa

Fiona Paton

Turbidity differences between Adelaide tap water (left) and water from the Coorong (right) David Blair

T h e C o o r o n g la g o o n s : b i o t i c r e s p o n s e s t o a c h a n g e d h y d r o l o g y

135

Changes to the distribution and abundance of Ruppia tuberosa in the southern Coorong A different species of Ruppia, Ruppia tuberosa, is found in the South Lagoon. This species reproduces by both seeds and turions (starchfilled organs) and functions as an annual plant in the southern Coorong. The seeds, turions and foliage of Ruppia tuberosa provide important food resources for waterfowl, such as ducks and swans, but also habitat and resources for other aquatic organisms that form the food chains in the southern Coorong (ostracods, chironomids and hardyhead fish). Like Ruppia megacarpa, this plant has fared poorly over the last decade and has almost disappeared from the system.

Dead Ruppia tuberosa exposed to air

Fiona Paton

For the next twenty years, there were no surveys of the distribution of aquatic plants in the northern Coorong. However, surveys undertaken in March 2007 failed to detect any Ruppia megacarpa plants and only two viable seeds were found in 2,200 core samples taken from surface sediments.14 The surveys were partly prompted by observations that few plants were present probably since the early 1990s. So some time since the mid 1980s, the perennial beds of Ruppia megacarpa have been lost from the northern Coorong. All that now remains are a few viable seeds at a very low overall density15 – about one seed per 20m2.

136

Ruppia tuberosa with flower heads

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

David Blair

A core sample containing Ruppia tuberosa shoots Coby Mathews

In the Coorong, Ruppia tuberosa grows on the shallow mudflats that are seasonally inundated around the shores of the South Lagoon, in water approximately 0.3m to 1m deep. Two factors may prevent the species growing in deeper water. First, the water of the Coorong is very turbid due to very high phytoplankton abundances. When water levels approach 1m, this turbidity may prevent sufficient light reaching the floor of the lagoon, so any plants trying to establish in water 1m or deeper may not receive sufficient light to grow. Second, the plants may only be able to grow in areas where consolidated sediments provide adequate anchorage for their shallow roots and rhizomes. At water depths of around 1m, the sediments on the lagoon floor are not compacted and any plants establishing in these areas may be easily dislodged by wave action. Although Ruppia tuberosa readily germinates in water less than 0.3m deep within the Coorong, few plants survive in water this shallow, because changes in the strength and direction of the wind may alter the water levels at any one location by up to 0.3m from one day to the next. Consequently, plants growing in water shallower than 0.3m may be left out of the water for periods of time and, once exposed to air, the plants quickly desiccate. The annual cycle of Ruppia tuberosa commences in May or June when the ephemeral mudflats around the shore of the South Lagoon are

Collecting core samples from the Coorong bed Coby Mathews

re-inundated with water. Seeds and turions, produced during the previous season(s) and deposited on the mudflats before they dried out in autumn, germinate and sprout when these mudflats are re-wetted. The plants then grow over winter and into spring, before flowering in mid to late spring and producing seeds. The plants also produce turions during late spring and summer when the salinities and water temperatures are increasing and before water levels drop and expose the plants. In the 1980s and early 1990s, and for at least two decades prior to this, Ruppia tuberosa was widespread and abundant along the length of the southern Coorong, including the extensive ephemeral mudflats south of Tea Tree Crossing.16,17,18 By 1999, Ruppia tuberosa was still prominent at sites along the length of the South Lagoon to about Tea Tree Crossing, where shoots were present in over 30% of core samples taken in July 1999. However, the incidence of

T h e C o o r o n g la g o o n s : b i o t i c r e s p o n s e s t o a c h a n g e d h y d r o l o g y

137

Progressive loss of Ruppia tuberosa from the South Lagoon of the Coorong.The figures show the percent of 200 core samples that contained Ruppia tuberosa in July in each year at five monitoring sites spread along the Coorong

F

7.4 Loss of Ruppia tuberosa from the South Lagoon

138

F

7.5 Winter salinities in the southern Coorong

160  North Lagoon North Lagoon 

South Lagoon 

140 

1998 

1999 

2000 

2001 

2002 

2003 

2004 

2005 

2006 

2007 

2008 

2009 

Salinity (g/L) 

120  100  80  60  40  20  0  NM 

VdY 

PP 

SC 

TTX 

Location 

Changes in winter salinities (g/L) at sites where Ruppia tuberosa was monitored over the last 12 years. One site was in the North Lagoon (NL), and four sites in the South Lagoon (SL): NM = Noonameena (NL);VdY = Villa dei Yumpa (SL); PP = Policeman Point (SL); SC = Salt Creek (SL);TTX = Tea Tree Crossing (SL). Ruppia tuberosa steadily declined at this site and in July 2005 shoots were no longer detected (Fig. 7.4). Similarly, at the site near Salt Creek, Ruppia tuberosa was present in over 50% of the core samples taken during July from 2000 to 2002, but the incidence of the plant in samples dropped substantially in 2003, and by July 2005 there were no plants present. At Policeman Point, 10km further north of Salt Creek, the initial incidence of Ruppia tuberosa was higher and remained at over 40% through 2004, but then dropped rapidly in July 2005, with no plants sampled in the following year. At Villa dei Yumpa, at the northern end of the South Lagoon, the incidence of Ruppia tuberosa remained above 80% and usually above 90% from 1999 to 2006, but the frequency of detecting shoots dropped in July 2007 to a little over 50% and by July 2008 no shoots were detected. Thus, over a period of just four years from 2005 to 2008, the

once widespread and abundant Ruppia tuberosa disappeared progressively from the South Lagoon. Another macrophyte, Musk Grass, was also abundant in the 1960s, still present at many sites along the South Lagoon in the early to mid 1980s and also in spring 1990,19,20 but has not been detected over the last decade. The pattern of decline for Ruppia tuberosa between 2002 and 2008 is interesting in that the plant has disappeared from the southern end of the South Lagoon, progressively northwards, during a period (2000-2004) when there was little difference in the salinities along the length of the South Lagoon (Fig. 7.5) and prior to really high salinities establishing in the South Lagoon. Thus, high salinity does not provide a satisfactory explanation for the gradual disappearance of Ruppia along the southern Coorong.

the CooRong LAgoons: biotiC Responses to A ChAnged hydRoLogy

139

Although very high salinities may reduce growth and reproduction, and even germination for Ruppia tuberosa, another factor likely to be influential in the decline of this species is inadequate water levels during spring. During spring and early summer, when there are releases of water over the Barrages, water levels remain higher in the southern Coorong and do not drop during spring,21 allowing Ruppia tuberosa to complete its reproductive cycle and produce turions over summer, when water temperatures are higher. However, if the Barrages close in spring, the drop in water levels in the South Lagoon is about 30cm and, for plants already growing in shallow water, such changes in water depth at this time of year could be critical. The importance of maintaining water levels through spring for Ruppia tuberosa has been known since the 1970s. For example, Delroy

reported that when water levels dropped in the southern Coorong during spring, large areas of Ruppia tuberosa were exposed and killed.22 Historical reports also suggest that the growth of both species of Ruppia was greater in years when flows were sustained over summer and water levels maintained, providing the plant with an extended period for growth. Based on modelling by the Murray-Darling Basin Authority, flows to the Murray Mouth would have naturally continued for most of the year and, in almost all years, continued throughout spring. For the period September to December at least 2,000GL of water (and more than 500GL in each month) would have reached the Murray Mouth in 86 of the 100 years from 1901-2000 under natural conditions (that is, no diversions or impediments to flow). However, with current levels of extraction and impediments to flows,

F

7.6 Changes in abundances of seeds and turions for Ruppia tuberosa in the South Lagoon 4,500       Seeds 

4,000 

     Turions 

Propagules per m2 

3,500 

     Turions and Seeds 

3,000  2,500  2,000  1,500  1,000  500  0  2001 

2002 

2003 

2004 

2005 

2006 

2007 

2008 

2009 

Year  Changes in overall abundances of seeds and turions of Ruppia tuberosa in the South Lagoon of the Coorong in January from 2001-2009. Data are mean + standard error sampled at three depths – dry, water line and 30cm of water – at 8 sites spread evenly along the Coorong. At each site and depth, ten 75mm diameter mud cores (4cm deep) were taken in each year from 2001-2006, while 25 samples were taken from each depth at each site for 2007-2009.

140

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

those volumes would have arrived at the Mouth in only six of the last 30 years (1979-2009), or just 20% of years. Furthermore, in 82% of years from 1901-2000, monthly flows to the Mouth would have increased between September and October under natural conditions, but this drops to just 50% over the last 30 years under current levels of extraction. So, not only have the volumes been reduced, but the frequency of increasing flows through spring has also diminished. Under natural conditions, there were only two months (both December), when flows would have ceased for the whole of a calendar month during the months of September to December over the 100 years from 1901-2000. There was also just one additional month during this 100 year period when the flows were below 100GL in a calendar month in the September to December period, again in December. With current extraction during the last 30 years, there were 28 calendar months between September and December when there were no flows, 22 of these since 2000. In 9 of the last 30 years, flows to the Murray Mouth and Coorong had stopped by November. For comparison, under natural conditions during the same period, there would have been just 3 months with no flows (December 1982, November and December 2006), a nine-fold difference in frequency. These changes in flows suggest that diminished water levels in spring in the South Lagoon may have occurred over the last 30 years, not just recently, and impacted on the reproduction of Ruppia tuberosa over this period. Importantly, in 5 of the last 7 years, there have been no flows to the Murray Mouth and Coorong region during spring. The once permanent beds of Ruppia tuberosa have consequently been stranded without adequate water cover in spring for several consecutive years, with no opportunity to reproduce. When there is no environmental flow (as has been the case in 5 of the last 7 years), water levels in the South Lagoon are likely to drop substantially during spring. This leaves most, if

not all, of the Ruppia tuberosa beds out of the water or at best in shallow water, with a high risk of exposure to the air before they have been able to reproduce. Since Ruppia tuberosa only germinates a proportion of its seeds in any one year, it has some capacity or resilience to cope with one or two poor years when it fails to reproduce. However, after a series of failed years, as in the last 7-8 years, the accumulated propagule banks will be exhausted. Each year, additional reserves of seeds have germinated during winter, but the resultant plants have failed to reproduce and the seed and turion banks have all but disappeared. Although some seeds still remain on the sediments (Fig. 7.6), more than 99% of these when tested did not germinate and were no longer viable. Ruppia tuberosa has essentially been in a ‘drought’ for the last 7-8 years, and that drought has been human-induced. If there had been no extraction of water, then in only 1 of the last 8 years would there have been no flows reaching the Murray Mouth in November and December, and Ruppia tuberosa would have experienced just one poor year. Since the day-to-day fluctuations in water levels are greater at the southern rather than northern end of the South Lagoon, Ruppia tuberosa is more likely to be eliminated from the southern sections before the northern sections. Strong southeasterly winds blow water northwards and away from the southern end of the South Lagoon.23 Under these conditions, water levels will rise at the northern end of the South Lagoon but not to the same extent as the drop in water at the southern end, because some of the extra water will be blown into the North Lagoon. With winds from the opposite quarter, water is blown southwards, but the extent to which the water levels drop in the northern parts of the South Lagoon are dampened because they are offset by water being blown in from the North Lagoon. Thus, wind-induced water level fluctuations are greater at the southern end of the South Lagoon than the northern end, and hence are more likely to impact on Ruppia tuberosa.

T h e C o o r o n g la g o o n s : b i o t i c r e s p o n s e s t o a c h a n g e d h y d r o l o g y

141

F

7.7 Changes in the abundances of chironomids in the South Lagoon 1,600  1,400 

Chironomids per m2 

1,200  1,000  800  600  400  200  0  2001 

2002 

2003 

2004 

2005 

2006 

2007 

2008 

2009 

Year 

Changes in the abundances of chironomid larvae in the South Lagoon of the Coorong in January from 2001-2009. Data based on 7.5cm diameter mud cores (4cm deep) that were taken in water 30cm deep in January of each year at each of eight evenly-spaced sites along the South Lagoon.Ten samples at each site were taken in the years 2001-2006, 25 samples from 2007 onwards. Data are mean + standard error.

F

7.8 Changes in the abundances of hardyhead fish in the South Lagoon 180 

Hardyheads per trawl 

150 

120 

90 

60 

30 

0  2001 

2002 

2003 

2004 

2005 

2006 

2007 

2008 

2009 

Year 

Changes in the abundances of hardyhead fish in the South Lagoon of the Coorong in January from 2001-2009. Data are means + standard error for the numbers of hardyheads caught in three replicate trawls at each of eight sites spread evenly along the South Lagoon.Trawls consisted of dragging a 7m long x 2m deep seine net in water 0.6-0.8 m deep for approximately 50m.

142

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

Although Ruppia tuberosa has disappeared from the South Lagoon during the last few years, small populations have established in the southern sections of the North Lagoon during the same period of time, and have been expanding northwards with a few plants detected as far north as Long Point by winter 2008.24 The successful dispersal of Ruppia tuberosa to the North Lagoon has probably been accomplished by dispersal in the water column of small fragments of Ruppia plants that have been dislodged from Ruppia beds by waves. However, the spread and establishment of Ruppia tuberosa northwards has in no way compensated for the loss of the extensive beds of this plant throughout the South Lagoon, or the earlier loss of Ruppia megacarpa from the North Lagoon. In summary, changes in water levels, in particular the magnitude of water level changes along the Coorong during spring, coupled with very high salinities, are likely to have caused the disappearance of Ruppia tuberosa from the southern Coorong. Changes in salinities and water levels are directly related to reductions in flows of River Murray water to the Murray Mouth.

Further recent changes to the aquatic biota of the southern Coorong In addition to the loss of Ruppia tuberosa from the southern Coorong, the once very abundant Small-mouthed Hardyhead and the chironomid Tanytarsus barbitarsis have also disappeared from the South Lagoon of the Coorong (Figures 7.7, 7.8), a consequence of the high salinities that have established. In January 2001 and 2002, the salinities were typical of those recorded from the 1960s to the 1990s, but since then they have risen steadily and for the last 3 years have typically been between 150-180g/L during January (see Chapter 5), around 5 times the salinity of sea water, and occasionally higher. These salinities now exceed the maximum salinity tolerances

Brine Shrimp in the South Lagoon

David Mariuz

Close-up of a Brine Shrimp

David Mariuz



of both the Small-mouthed Hardyhead and the common chironomid Tanytarsus barbitarsis,25,26 and both are now absent from the South Lagoon. Even the winter salinities are now often above the levels that these species can tolerate. The other striking recent biological change to the Coorong has been the rapid colonisation of the South Lagoon by Brine Shrimps. Brine Shrimps were not detected in plankton trawls in the South Lagoon until July 2004 when a few were detected near Salt Creek, although they were present in a few nearby ephemeral, highly saline wetlands where there were no fish.27 The high salinities in the South Lagoon and the absence of fish provide ideal conditions for Brine Shrimp. By July 2005, the whole of the South Lagoon was dominated by them, with perhaps

T h e C o o r o n g la g o o n s : b i o t i c r e s p o n s e s t o a c h a n g e d h y d r o l o g y

143

Brine Shrimp in the Coorong

B

rine Shrimp of the genus Artemia are well known and occur in ephemeral salt lakes and salinas around the world. In Australia, we have an endemic genus of Brine Shrimp, Parartemia, which has independently adapted to living in salt lakes. There are presently 12 described species of Parartemia with more to be described. The most widespread species is Parartemia zietziana which occurs in south-eastern Australia and Tasmania. This species is found in winter-filled ephemeral salt lakes adjacent to the Coorong lagoons. In July 2004, P. zietziana were collected from the main body of the South Lagoon at Salt Creek, and quickly established a large population across the South Lagoon by mid 2005, which persists until now. P. zietziana is dispersed as resistant eggs which hatch to nauplii when salinities fall. Brine Shrimp probably arrived in the South Lagoon as resistant eggs, carried on the feet of birds. These subsequently hatched when salinities fell in winter. The establishment of the population would have been related to the salinities in the South Lagoon increasing so as to exceed the tolerance of the small hardyhead fish that are characteristic of the South Lagoon. These fish would selectively prey on Brine Shrimp and not allow a population to establish. P.zietziana can grow from nauplii to adults in 6 to 8 weeks. They are unusual among Parartemia species because the females lay two types of eggs, eggs that hatch immediately in the brood pouch or resistant eggs that sink to the sediments and hatch some time later, when suitable environmental cues are provided. Resistant eggs are usually produced when salinities and temperatures rise. These two modes of reproduction mean that populations can grow rapidly when conditions are favourable. When the conditions are not suitable, the resistant eggs allow them to over-summer.

B� M��� G�����

brine Shrimp

144

Scott MillS

brine Shrimp washed up on the South Lagoon shore-line lydia Paton

as many as 100 Brine Shrimps per cubic metre throughout the lagoon. During summer, when the salinities are generally higher, Brine Shrimps moved northwards into the southern 10km of the North Lagoon, provided the salinities were well above 100g/L, and then retreated back to the South Lagoon in winter, when salinities in the North Lagoon dropped below about 100g/L. Over the last couple of decades, there have been dramatic changes in the distributions and abundances of key aquatic organisms along the Coorong. These are strongly linked to changes in the hydrology of the Coorong lagoons, particularly increasing salinity, but also water depths. The extent of these changes, both hydrological and biological, would contravene international expectations of meeting obligations to manage this wetland in a sustainable manner. One of the key components in the original nomination of the Coorong and Lower Lakes as a Wetland of International Importance was the use of this system by large numbers of waterbirds, including migratory waders and iconic endemic species that regularly use the Coorong, like the Australian Pelican and Banded Stilt. Therefore, the question that must now be addressed is: how have the waterbirds responded to these ecological changes?

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

1.

MC Geddes and AJ Butler, ‘Physicochemical and biological studies on the Coorong lagoons, South Australia, and the effect of salinity on the distribution of the macrobenthos’, in Transactions of the Royal Society of South Australia, 108 (1984): 51–62.

15. Nicol, 2007.

MC Geddes, ‘Changes in salinity and in the distribution of macrophytes, macrobenthos and fish in the Coorong lagoons, South Australia, following a period of River Murray flow’, in Transactions of the Royal Society of South Australia, 111 (1987): 173–181.

17. BJ Noye, ‘Waters of the Coorong Lagoons’, in The Coorong, edited by John Noye, Revised edition (Adelaide: Department of Adult Education, University of Adelaide, 1975), 59–79.

3.

Geddes, 1987.

19. Geddes, 1987.

4.

Geddes and Butler, 1984.

20. David Paton unpubl.

5.

S Dittmann, A Cantin, W Noble and J Polkington, Macrobenthic survey 2004 in the Murray Mouth, Coorong and Lower Lakes Ramsar site, with an evaluation of food availability for shorebirds and possible indicator functions of benthic species (Adelaide: Department for Environment and Heritage, 2006).

21. Noye, ‘Waters of the Coorong Lagoons’, 73; David Paton unpubl.; IT Webster, An overview of the hydrodynamics of the Coorong and Murray Mouth (Canberra: CSIRO Water for a Healthy Country National Research Flagship, 2005).

6.

A Rolston and S Dittmann, The distribution and abundance of macrobenthic invertebrates in the Murray Mouth and Coorong lagoons 2006 to 2008 (Canberra: CSIRO Water for a Healthy Country National Research Flagship, 2009).

2.

16. LB Delroy, ‘The food of waterfowl (Anatidae) in the southern Coorong saltwater habitat of South Australia’, in South Australian Ornithologist, 26 (1974): 157–163.

18. David Paton unpubl.

22. Delroy, 1974. 23. Noye, ‘Waters of the Coorong Lagoons’, 55–79.

7.

Geddes, 1987.

24. DJ Rogers and DC Paton, Changes in the distribution and abundance of Ruppia tuberosa in the Coorong (Canberra: CSIRO Water for a Healthy Country National Research Flagship, 2009).

8.

CJ Noell, Q Ye, D Short, L Bucater and NR Wellman. Fish assemblages of the Murray Mouth and Coorong region, South Australia, during an extended drought period (Canberra: CSIRO Water for a Healthy Country National Research Flagship, 2009).

25. MJ Kokkinn and WD Williams, ‘Adaptations to life in a hypersaline water-body: adaptations at the egg and early embryonic stage of Tanytarsus barbitarsus Freeman (Diptera, Chironomidae)’, in Aquatic Insects, 10 (1988): 205–214.

9.

Geddes and Butler, 1984; Geddes, 1987.

26. LC Lui, ‘Salinity tolerance and osmoregulation of Taeniomembras microstomus (Gunther 1861) (Pisces: Mugiliformes: Atherinidae) from Australian salt lakes’, in Australian Journal of Marine and Freshwater Research, 20 (1969): 157–162.

10. Geddes, 1987. 11. Pauli Snoejis and Honorée van der Ster, An integrated hydrobiological-geobotanical study of the Leilaeno-Ruppion in South Australia (Toernooivaeld Nijmegen: Laboratorium voor Aquatische Oecologie Botanisch Laboratorium, Afdeling Geobotanie,Katholieke University, 1981). 12. Snoejis and van der Ster, 1981.

27. M Geddes and M Brock, ‘Limnology of some lagoons in the southern Coorong’, in The southern Coorong and lower Younghusband Peninsula of South Australia, edited by DD Gilbertson and MR Foale (Adelaide: Nature Conservation Society of South Australia, 1977), 47–49.

13. Snoejis and van der Ster, 1981. 14. JM Nicol, Impact of barrage releases on the population dynamics of Ruppia megacarpa in the Murray Estuary and North Lagoon of the Coorong. Progress Report 2006/07 (Adelaide: South Australian Research and Development Institute, Aquatic Sciences, 2007).

the CooRong LAgoons: biotiC Responses to A ChAnged hydRoLogy

145

Red-necked Avocet

146

At t h e E n d o f t h e R i v e r – T h e C o o r o n g a n d L o w e r L a k e s

Rohan Clarke

ChAPteR 8

The Coorong Lagoons: A critical refuge for waterbirds

O

veR The lasT DeCaDe TheRe have Been

significant changes to the hydrology of the Coorong that have in turn influenced the distribution and abundance of a range of aquatic organisms that provide food resources for birds. As a general rule, the changes have been more dramatic in the southern Coorong than in the northern Coorong. In the South Lagoon, key components of the food chain, including the once abundant aquatic plant Ruppia tuberosa, a key aquatic invertebrate the chironomid Tanytarsus barbitarsis and the highly salt-tolerant fish, the Small-mouthed Hardyhead, have all disappeared. Instead Brine Shrimps are now prominent in the highly saline water. In the North Lagoon, the major changes have been a contraction in the distribution of many aquatic fauna northwards to the northern reaches of the North Lagoon where the salinities are still

A resident Black-winged Stilt foraging

ChRis TzaRos

suitable. However, significant changes to the food chains of the North Lagoon may have taken place in the past, since the once abundant Ruppia megacarpa has been absent for much of the last 20 years. Small amounts of Ruppia tuberosa are now colonising the southern reaches of the North Lagoon where Ruppia megacarpa was once abundant. Although there are no historical data, the aquatic benthic invertebrates and fish that would be expected to inhabit the Murray Estuary are still all present, even though their abundances may have changed.

One of the migratory waders – Sharp-tailed Sandpiper Paul WainWRiGhT

t h e C o o R o n g L A g o o n s : A C R i t i C A L R e f u g e f o R wA t e R b i R d s

147

The responses of waterbirds to these changes in key food resources will vary from species to species, depending on their feeding ecology and on their dependence on particular food resources. An understanding of the ecology of the various waterbirds that use the Coorong is required before any changes in their distributions and abundances can be assessed. This chapter

T

begins by describing the waterbird communities of the Coorong before assessing changes in their distribution and abundance. Given that the major changes to resources have taken place in the southern Coorong, changes in the bird populations are likely to be more severe for the southern Coorong than the northern Coorong.

8.1 Waterbird species of the Coorong

Waterbird species Australian Pelican (10)

Eastern Curlew (10)

Pied Cormorant (10)

Australian Spotted Crake (6)

Eurasian Coot (10)

Pied Oystercatcher (10)

Australian Shelduck (10)

Fairy Tern (10)

Pink‐eared Duck (4)

Australasian Shoveler (8)

Great Cormorant (10)

Purple Swamphen (2)

Australian Wood Duck (2)

Great Crested Grebe (10)

Red‐capped Plover (10)

Australian White Ibis (10)

Great Egret (10)

Red‐kneed Dotterel (7)

Bar‐tailed Godwit (8)

Great Knot (6)

Red Knot (3)

Black‐faced Cormorant (10)

Greater Sand Plover (1)

Red‐necked Avocet (10)

Black‐fronted Dotterel (1)

Grey Plover (5)

Red‐necked Phalarope (1)

Black‐tailed Godwit (9)

Grey Teal (10)

Red‐necked Stint (10)

Banded Lapwing (3)

Gull‐billed Tern (6)

Royal Spoonbill (10)

Banded Stilt (10)

Hardhead (4)

Ruddy Turnstone (3)

Black Swan (10)

Hoary‐headed Grebe (10)

Ruff (1)

Black‐tailed Native‐hen (5)

Hooded Plover(10)

Sanderling (5)

Black‐winged Stilt (10)

Little Black Cormorant (10)

Sharp‐tailed Sandpiper (10)

Caspian Tern (10)

Little Egret (10)

Silver Gull (10)

Cape Barren Goose (10)

Little Pied Cormorant (10)

Sooty Oystercatcher (7)

Chestnut Teal (10)

Little Tern (1)

Straw‐necked Ibis (10)

Common Greenshank (10)

Masked Lapwing (10)

Terek Sandpiper (2)

Common Sandpiper (7)

Marsh Sandpiper (7)

White‐faced Heron (10)

Common Tern (8)

Musk Duck (10)

Whimbrel (3)

Crested Tern (10)

Pacific Black Duck (10)

Whiskered Tern (10)

Curlew Sandpiper (10)

Pacific Golden Plover (10)

Yellow‐billed Spoonbill (1)

Darter (2)

Pacific Gull (6)

Alphabetical list of waterbird species counted in the Coorong in January over the last ten years (2000-2009).The number of years in which each species was detected is given in parentheses.There are additional species such as Double-banded Plover that are seen at other times of the year.

148

At t h e e n d o f t h e R i v e R – t h e C o o R o n g A n d L o w e R L A k e s

F

waTerbirds of The coorong lagoons

100 

Percent of Birds 

Over the last 10 years, 71 species of waterbirds have been detected using the Coorong during the summer months. Of these, 40 species have been recorded in every year, another 17 species in most years, while 14 species were detected in no more than 3 years and then only in small numbers, often a single individual (Table 8.1).

8.1a Foraging depths of small waders in the Coorong Red‐capped Plover 

80  60  40  20  0