Underwater Sydney Book 9781486311187, 9781486311194, 9781486311200

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This book is dedicated to our wonderful, supportive families who have always encouraged us to follow our passion for the ocean. John Turnbull: My amazing family: Jane, Adele, Olivia and Emilia Turnbull Inke Falkner: My parents Doris and Horst Falkner, my sister Kerstin and my love Dominick ter Huurne

INK E FA LK N ER A ND JOHN T URNBULL

© Text: Inke Falkner 2019 © Images and captions: John Turnbull 2019 All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO Publishing for all permission requests. The authors assert their moral rights, including the right to be identified as an author. A catalogue record for this book is available from the National Library of Australia. ISBN: 9781486311187 (pbk.) ISBN: 9781486311194 (epdf) ISBN: 9781486311200 (epub) Published by: CSIRO Publishing Locked Bag 10 Clayton South VIC 3169 Australia Telephone: +61 3 9545 8400 Email: [email protected] Website: www.publish.csiro.au Front cover: Port Jackson shark Back cover: (left to right) Eastern blue groper, red cuttlefish, Sydney Harbour, weedy seadragon All photographs are by John Turnbull unless otherwise specified Edited by Joy Window (Living Language) Cover design by Andrew Weatherill Typeset by Desktop Concepts Pty Ltd, Melbourne Printed in China by 1010 Printing International Ltd. CSIRO Publishing publishes and distributes scientific, technical and health science books, magazines and journals from Australia to a worldwide audience and conducts these activities autonomously from the research activities of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The views expressed in this publication are those of the author(s) and do not necessarily represent those of, and should not be attributed to, the publisher or CSIRO. The copyright owner shall not be liable for technical or other errors or omissions contained herein. The reader/user accepts all risks and responsibility for losses, damages, costs and other consequences resulting directly or indirectly from using this information. The paper this book is printed on is in accordance with the standards of the Forest Stewardship Council ®. The FSC ® promotes environmentally responsible, socially beneficial and economically viable management of the world’s forests.

May19_01

Foreword Sydneysiders instinctively recognise that something magical – and precious – lies beneath the sparkling waters of our harbour, one of the largest, most spectacular and most biologically diverse natural harbours on earth. My own favourite harbour diving spot, beneath the steep sandstone cliffs of the ‘heads’ that mark the wide opening to the Pacific Ocean, epitomises what makes our harbour so special. Jumping from a boat at the bottom of North Head, I love to follow the cliff face down, underwater. I’m quickly 30 metres below the surface, among sponge gardens and sea squirts that undulate like decorative bunches of flowers. The huge blue gropers never fail to circle in for a look, their thick lips nibbling inquisitively, baring pointy, crooked teeth. No matter how many times I dive here, the magic never diminishes. Nor do I ever forget that I’m swimming below a big, busy, modern city. As a marine ecologist, I see the sponge gardens of the heads as an extraordinary living link between a dynamic city of some five million people and the harbour’s complex ecosystems. This is, of course, a fragile relationship. Only by better understanding Sydney’s marine environment – and how it interacts with the people and processes of this humming economic hub – can we protect and nurture it into the future. Underwater Sydney takes us on a fascinating, inspiring and important journey into this unique underwater world. While Sydney’s Opera House, Harbour Bridge and famous beaches are recognised worldwide, this beautiful book dips below the surface to reveal a less familiar world. As a drowned river valley, first carved into Hawkesbury sandstone some 25–29 million years ago, then filled by rising seawaters 6000 to 17 000 years ago, Sydney Harbour’s geographical diversity is notable. Its numerous sandy bays, steep rocky shores, sandstone cliffs, rock pools, deep blue channels and sparkling turquoise shallows lend it its exceptional natural beauty. From the shore to the depths, this complex natural underwater architecture supports a dazzling array of natural habitats, from mangroves and saltmarshes to rocky reefs, sandy seafloors and seagrass meadows and the fascinating rock pools that come and go as the tides rise and fall over the rocky shores and coastal rock shelves. Those habitats in turn support very high biodiversity. Even today, after centuries of settlement, industrialisation and development, Sydney Harbour has many more species of fish – 586 recorded to date – than more pristine estuaries. And although about half of the extensive shoreline of Sydney Harbour has been altered by artificial structures, the harbour remains perhaps the most biologically diverse port in the world. This wonderful expanse of water shows us that a city can exist side by side with nature.

How do we value such an extraordinary asset, an asset that supports unique marine ecosystems at the same time as it helps power the economic engine of Australia’s largest city and supports the well-being and social interaction of residents and visitors? One recent research project suggested that approximately $43 billion was a reasonable starting point, taking into account everything from the ports and trade to tourism, cultural heritage, coastal access, boating, swimmable beaches and waterfront parks. Whatever the figure, Sydney Harbour is a genuine gem that is worthy of our effort and care. Sydney Harbour has been my natural laboratory and my studies have given me some cause for optimism. Since the 1970s, major efforts to clean up industrial pollution and to protect the waters and the ecosystems that rely on them from further pollution have led to significant improvements in water quality. I’ve seen oyster beds regrow along the intertidal zone and watched as green waters have become increasingly clear. All this while the city’s economy and social life have continued to thrive. I’ve focused much of my own research around this wonderful harbour and, with a large team of collaborators, we are building an unprecedented knowledge bank to inform the future. But, there are still many questions to be answered. Perhaps, more than anything else, we need to connect the dots. We don’t yet truly understand how the harbour’s complex and greatly varied environments and ecosystems function and how they interact with each other, or how they then interact or co-exist with the city above. Such insights are more important than ever before. New threats are building as the climate changes and waters warm, new species are arriving every day from the north, more frequent extreme weather events batter the coast and debris and microplastics find their way into natural water systems with as yet unknown results. We also know that past industries have left behind a toxic legacy of heavy metals and other contaminants locked in the harbour’s silty seafloor. This is a challenge for all of us: governments, businesses, researchers and the community. Underwater Sydney reveals that we have much to celebrate today and introduces us to what it will take to protect this remarkable harbour for tomorrow. Perhaps more than anything else, this wonderful book is a call to ‘get out there’ – to swim, snorkel, dive, learn and enjoy! Professor Emma L Johnston AO

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Underwater Sydney

Contents Foreword v About the authors

viii

Acknowledgements ix Introduction 1 Intertidal rocky shores

13

Underwater forests

29

Sponge gardens

45

Beaches and seagrass meadows

61

Mud and mangroves

77

Novel habitats

93

Ocean travellers and visitors

109

The future of Sydney Harbour

125

Underwater photography

135

What can I do?

141

References 142 Index 155

About the authors Inke Falkner is a marine ecologist who focuses on creative science and environmental education. In her role as Community Outreach Coordinator at the Sydney Institute of Marine Science, she developed and established an extensive marine science program for primary and high school students focusing on Sydney Harbour. She also curated the content for the Institute’s Discovery Centre, and ran educational harbour cruises and foreshore walks featuring the amazing underwater world of Sydney Harbour. Having moved to the Southern Tablelands, New South Wales, she is now the Program Coordinator at the Australian National University’s Kioloa Coastal Campus. In her spare time Inke works as a freelance science writer. John Turnbull is a marine ecologist, social scientist, and passionate underwater photographer. John has dived extensively in Sydney Harbour and coastline and knows their inhabitants extremely well. His delightful and exciting photographs bring this book to life. A few years ago, John traded a life in the business sector to pursue his passion for marine conservation, and is currently researching the relationship between humans, nature and stewardship of the marine environment at the University of New South Wales. You can visit John’s website or photo stream www. marineexplorer.org/ and www.flickr.com/photos/johnwturnbull/ for some examples of his extraordinary work.

Acknowledgements We, the authors, acknowledge the Gadigal people of the Eora Nation as the traditional custodians of this place we now call Sydney and we pay our respect to Elders past, present and future. This book would not have been possible without the work of so many scientists who have spent years studying Australia’s extraordinary temperate coast and the underwater communities of Sydney Harbour and surrounds. All information presented in this book is based on their work. A special thank you must go to our colleagues who reviewed individual chapters and provided great feedback and advice: Introduction: Dr Pat Hutchings and Dr Carol Langley Intertidal rocky shores: Dr Tony Underwood Underwater forests: Dr David Booth, Dr Geoffrey Liggins and Dr Carol Langley Sponge gardens: Dr Nathan Knott and Dr Stephen Smith Beaches and seagrass meadows: Dr Alistair Poore and Dr Carol Langley Mud and mangroves: Dr Vivian Sim and Dr Pat Hutchings Novel habitats: Dr Katherine Dafforn Ocean travellers and visitors: Dr Penelope Ajani, Dr Vanessa Pirotta, Dr Amy Smoothey and Dr Adriana Vergés The future of Sydney Harbour: Dr Edwina Tanner We are most grateful to the photographers who generously supplied photographs of animals and special moments. These are Dr Penelope Ajani, Ann Killeen, Dr Gurjeet Singh Kohli, Dr Vanessa Pirotta and Dr Frank Tränkle. Many thanks also to Dr Emma Johnston, the inaugural director of the Sydney Harbour Research Program at the Sydney Institute of Marine Science, for writing such a passionate foreword for this book. Our extended families have played a big part in supporting us through our lives, to allow us to write a book like this. We’d like to make particular mention of Geoff, Betty and Wes Turnbull, Heather Bennett, Anneliese Gall, and Frieda and Fritz Prozeske. Last but certainly not least we would like to thank CSIRO Publishing for giving us the opportunity to produce this beautiful book, which we hope will ignite a sense of wonder about the underwater world of Sydney in readers. Many thanks to Eloise Moir-Ford who guided us thoughtfully through the publication process.

Introduction

One gorgeous spring day, mild and clear, I remember travelling home on the ferry from Taronga Zoo to Circular Quay. On our way, the captain made an announcement that we had to stop. There was a communal sigh of impatience, followed by an ‘ooh’ after we were told that we had to give way to a humpback whale. All of us instantly headed for the ferry’s bow ready to take a look at the animal ahead. In anticipation, we stood waiting in front of a smooth swirling patch of water. We never saw the whale, but the fact that we crossed paths with one of these magnificent creatures in the middle of Sydney Harbour, this busy waterway at the heart of a major city, still astounds me. Humpback whales are regular visitors inside the harbour on their biannual migration along the coast and they are always greeted with much enthusiasm, but what most of us don’t know is that Sydney Harbour and the adjacent coast are teeming with wildlife. This book is a celebration of this rich and colourful underwater world with its extraordinary plants and animals. Importantly, we also discuss how our actions have changed the harbour over time and how marine scientists help to restore and maintain this spectacular landmark. Sydney Harbour is instantly recognisable from above, but underwater, its beauty and diversity are perhaps even more breathtaking. Beaches interspersed by rocky reefs adorn the harbour foreshore and surrounding coastline, seagrass meadows grow in protected bays, pontoons and wharfs are densely overgrown with strangely shaped and beautifully coloured invertebrates, and mangroves grow further upstream. Scientists from the Australian Museum analysed more than 20  000 museum records of fishes and invertebrates, to get an estimate of the harbour’s extraordinary wealth in marine life and counted over 3000 species – and that’s a conservative estimate. The Museum scientists concluded, ‘Considering that Australia’s largest city surrounds the harbour, it’s amazing that we have such a diverse fauna.’ So why is Sydney Harbour so incredibly diverse? Well, its geological past has much to do with it. The Sydney estuary is what experts call a ‘drowned river valley’, an ancient eroded river valley carved out of the soft Sydney sandstone and shale by the Parramatta River and its tributaries and repeatedly flooded by the ocean during interglacial periods. Until the end of the last ice age, when sea levels were around 100  m below those of today and the shore up to 30  km further out at sea, rising temperatures and the thawing of glacial ice once again raised the ocean to present-

2

Underwater Sydney

Just inside North Head, Little Manly is a playground for swimmers, snorkellers, boaters and picnickers.

day levels around 6000 years ago. There are eight drowned valley estuaries along the New South Wales coast and Sydney Harbour or Port Jackson, which is its original name, is one of the largest. Drowned river valley estuaries such as Sydney Harbour are flanked by steepsided banks and are well flushed by the tides, making conditions inside the estuary largely marine, especially since freshwater input from the Parramatta, Duck and Lane Cove rivers is small for most of the year. The harbour is connected to the open ocean through a 3 km-wide entrance framed by North and South Heads. The southward flowing East Australian Current (EAC) brings warm, nutrient-poor water to Sydney’s shores, while winds and other currents push cold, nutrient-rich bottom water to the surface. Twice daily with the tides up to 6000 m3 per second of harbour water, which is more than two Olympic-size swimming pools per second, are exchanged with new oceanic water. The regular renewal of harbour water con-

Introduction

3

tributes greatly to the overall health of the system and its natural resistance to environmental stress. The complex nature of submerged river valleys provides a range of living spaces and niches for diverse underwater communities. Depth varies greatly in different parts of the harbour and this, together with water quality, determine how much light reaches the seafloor. Light is gradually absorbed in water so marine plants are restricted to shallower depths along the shore. This is where we find kelp forests and seagrass meadows. The harbour entrance and the main channel are naturally quite deep, up to 35  m, and there are a series of holes up to almost 50  m in depth. Just west of the Harbour Bridge happens to be one of the deepest holes. These deeper, less lit parts of the harbour are inhabited by animal communities that are not dependent on light for photosynthesis. Almost 700 species of fish alone have been recorded over the years in Sydney Harbour. Some of these fishes are visitors and not local residents, but such a diversity in an estuary roughly 50  km2 in area is astonishing and even more impressive

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Underwater Sydney

Looking south across the old Quarantine Station at North Head on the left, with South Head on the horizon in the centre, and Middle Head on the right. The skyline of Sydney is just visible behind Middle Head.

Rocky foreshores and reefs are a feature of Sydney Harbour – this shot shows the steep rocky shoreline at Clifton Head, Sydney Harbour.

when compared to other parts of the world. The entire Mediterranean Sea, for example, and, similarly, the coasts of both the United Kingdom and New Zealand are home to fewer species of fish than Sydney Harbour! With scientists studying the harbour’s marine life for more than a century, one might think that the fish fauna is well described. But as recently as 2001, a group of recreational divers discovered a new species in 14  m depth at Chowder Bay – the Sydney scorpionfish (Scorpaenopsis insperatus)! It has so far not been found anywhere else in the world and therefore seems to be unique to the harbour. Indeed, there is no shortage of rare, charismatic, stunningly beautiful or plain weird fishes that live inside the harbour and along Sydney’s coast. Sydney’s rocky reefs and kelp forests are home to some of the most striking inhabitants. Old wives, yellowtail scads, eastern pomfrets and silver batfish are common sights, and so are leatherjackets, pufferfishes and wrasses. Among the kelp live golden weedfish, which mimic perfectly the appearance and movement of kelp. Bullseyes and pineapple fish hang out underneath rock ledges. One of the most famous and

Introduction

5

admired fishes inhabiting Sydney’s waters is the weedy seadragon. However, weedy seadragons are rarely seen in the harbour and are sadly declining in numbers in wider Sydney. But their relatives, the seahorses, pipehorses and pipefishes, are somewhat easier to find – that is if you can spot these well-camouflaged and, in the case of the Sydney pygmy pipehorse, also extremely tiny creatures! Invertebrates well outnumber fishes both in species richness and actual numbers. Molluscs are the most diverse group of invertebrates with well over 1000 recorded species. The charismatic octopuses, squids and cuttlefishes are masters of disguise and agile predators. The reaper cuttlefish (Sepia mestus), for example, can change body colour and texture rapidly and blend in superbly with its environment. When undisturbed, it is easily recognised by its red body and two dark blotches on the back. Most molluscs, however, live on the sea floor. Snails, sea slugs and chitons are particularly diverse on Sydney’s rocky reefs and they come in all sizes, shapes and colours while extensive mussel and oyster beds cover the rocky foreshore. In addition, there are at least as many different types of crustaceans living in the harbour as there are fishes. The echinoderms and bristle worms are somewhat less diverse with just over 100 and 300 species respectively, but they include some of the most ecologically important animals found in Sydney. Growing on sandstone boulders and reefs among the seaweeds and in greater depths are sea squirts, sponges and other invertebrates that have the appearance of plants, but are in fact animals. These communities form living habitats for other

6

Underwater Sydney

A golden weedfish (Cristiceps aurantiacus, left) and the Sydney pygmy pipehorse (Idiotropiscis lumnitzeri, right) blend in beautifully with their surroundings. The pipehorse is only around 20 mm long!

A reaper or red cuttlefish (Sepia mestus) sits camouflaged against red encrusting algae on a boulder (left). On the right, the same species has changed its appearance to match the shark net overgrown with algae in the background.

organisms and, being attached to rock, they are unable to escape predators. So many of these creatures produce chemicals and sometimes bony elements in their tissues that make them unpalatable. Other animals, like sea slugs, take advantage of this and have evolved to eat sponges and borrow their defences. Spotting ‘nudies’, these delightful critters, frivolously covered in polka dots, frills and stripes, is a highlight for any diver or snorkeller.

The nudibranch Chromodoris tasmaniensis feeds on its preferred pink sponge at Kurnell in Botany Bay. The animal’s external gills are the feathery structures at the top right of the picture. The head is at the bottom left.

Introduction

7

Although corals are mostly thought of in the context of tropical reefs, Sydney is home to several species of hard corals. The coral Plesiastrea versipora, for example, grows in shallow depths where plenty of sunlight can reach it, so the algae inside the coral body can photosynthesise. Some colonies can be of an extraordinary green colour. The bright orange coral Culicia tenella, on the other hand, does not have photosynthesising algae in its tissue and it is common on rocky surfaces with little light, such as the walls of caves and overhangs. Nowadays more than half of the harbour’s natural foreshore has been replaced by seawalls and other marine infrastructure. The remaining, isolated small pockets of natural habitat are less biodiverse compared to unfragmented natural shores. The foreshore is dotted with countless wharfs, pontoons and jetties, and these structures provide new habitat for marine life. Some of the timber pylons that have been in place for many years are densely overgrown with the most colourful organisms, in turn attracting fish and crabs. Artificial structures do have their problems, though. Many of the organisms that flourish on these structures are not naturally at home here. Having hitched a ride on ships entering the harbour, non-natives can thrive on artificial structures at the expense of the local plant and animal life. So it’s important to recognise that we are creating artificial habitats that do not resemble natural environments. All harbours – and Sydney is no exception – have a problem with introduced pests because they are globally connected through shipping. Other non-natives found on our shores, such as the Pacific oyster (Crassostrea gigas), have escaped aqua-

8

Underwater Sydney

Several colonies of the green coral (Plesiastrea versipora) grow on a vertical rock surface at Fairlight (left). Culicia sp. coral polyps grow underneath a rock ledge at Bare Island, Botany Bay (right).

Boats, jetty and Sydney ferry at Manly. Artificial structures such as jetties allow non-native species to spread in the harbour.

culture farms or, like the green alga Caulerpa taxifolia, have spread with the aquarium trade. Caulerpa taxifolia originates from Queensland and was first discovered in Sydney Harbour in 2002. It is highly invasive and the smallest dislodged pieces can grow and multiply. Being toxic to many marine animals, it is known to create an environment that supports a completely different fish and invertebrate community than that of neighbouring native habitats. Interestingly, its close relative Caulerpa filiformis, which is native to the Sydney region, has also spread and is now considered a ‘native pest’. At low tide you may have seen beds of this bright-green alga growing in the shallows of the harbour, for example at the Botanic Gardens next to the Opera House. Caulerpa filiformis seems to grow easily at newly disturbed sites, where competition is low, and it copes better with murkier, nutrient-rich water compared to other native algae. These are exactly the conditions we find in many parts of the harbour and along the coast, where foreshore developments have changed local conditions. While water quality in the harbour has improved tremendously due to the closure of sewage discharge points and many polluting harbourside industries, some of the harbour’s seafloor sediments remain highly toxic. Many pollutants, including

Introduction

9

Green alga Caulerpa filiformis among red and brown algae at Fairy Bower, Manly.

Small, local stormwater drains feed run-off straight into the harbour.

10

Underwater Sydney

metals such as copper, zinc and lead, a variety of organic chemicals, nutrients and sediments, continue to enter the harbour today via drains and stormwater canals. Scientists have identified pollution as one of the main environmental threats to a healthy harbour and coastline together with the impacts of fishing activities, nonnative species, habitat modification and climate change. In a comprehensive review of all scientific knowledge available for Sydney Harbour, the scientists conclude: ‘Sydney Harbour is a paradox; stunningly beautiful, astonishingly diverse but subject to serious threats. …. This iconic estuary has been subject to dramatic change and is facing enormous new challenges. The scientific community will be integral to providing independent, rigorous and credible data and analyses to manage the natural resources of Sydney Harbour into the future.’ Despite the challenges, Sydney Harbour and the surrounding coast are incredibly diverse and a great national treasure. Scientists and non-scientists, locals and visitors alike love its natural beauty and cherish any encounters with the harbour’s wildlife. The underwater world of Sydney is full of life, drama and interaction, and there are struggles, too. We hope this book will excite you and give you an appetite to explore this spectacular, largely hidden world for yourself. To see some of this theatre unfold before your eyes is a wonderful experience.

Introduction

11

Shelly Head

Intertidal rocky shores

Sydney’s sandstone rocky shores and headlands are a spectacular sight. The North and South Heads stand proudly at the harbour’s entrance and protect the harbour foreshore from stormy seas and incoming waves. On the open coast the constant pounding of waves weathers and transforms the fragile sandstone coast. When the tide is going out, extensive rock platforms and boulder fields appear. The rocky intertidal zone, the transition zone between land and sea, is a highly dynamic and challenging environment. Twice daily, Sydney’s shores are flooded by the sea. During low tide, when the ocean has retreated, the upper shore becomes exposed, leaving the plants and animals living there unprotected from the sun’s burning rays, drying winds and pelting rain. Only the tough survive here. Molluscs, with their protective, hard shells, have truly conquered rocky intertidal shores. At high tide billions of grazing snails, limpets, chitons and other herbivores constantly scrape microscopic algae off the rocks, leaving nothing but barren rock comparable to an overgrazed paddock. Competition for food is fierce and when parts of the shore are protected from these grazers, a variety of algae grow back within days. But when the tide is low, these animals tuck into their shells and rest. Cracks, crevices and pools retain moisture, which is why snails such as striped periwinkles, zebra winkles, and black nerites cluster there. The undersurfaces of loose boulders offer another specialised living space. Hidden from sunlight and predators, softbodied animals such as sea cucumbers, sea slugs and flat worms as well as nocturnal animals such as brittle stars find a suitable home here.

A view over the Oak Park rock platform in southern Sydney reveals the great complexity of the intertidal zone. Pools, fissures and overhangs all provide refuge for the animals and plants that call the intertidal their home.

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Underwater Sydney

Rock pools are a distinct feature of intertidal shores. They may differ in size, shape and depth, but they all retain water during low tide, making them a welcome refuge for the animals living exposed on the intertidal shore. In addition, rock pools contain plants and animals from greater depths and thus are a microcosm of the reef below. The communities occupying rock pools are therefore ever-changing and diverse. Exploring rock pools is like going on an aquarium tour. The walls are lined with an array of red, green and brown algae. For example, Neptune’s necklace (Hormosira banksii), which forms chains of algal pearls, is a common sight and so is sea lettuce (Ulva australis), a bright green alga that grows like floppy lettuce leaves and can be harvested and eaten. The cracks and crevices are often home to anemones, squishy blobs of soft tissue with a ring of tentacles to catch food. The bright red waratah anemone (Actinia tenebrosa) stands proud in the open, while the shell grit anemone Oulactis muscosa decorates itself with pieces of shells, which make it less likely to be seen and eaten. Juvenile fish and shrimps often get trapped in the pools when the water recedes, while predatory crabs, whelks and sea stars feast on the confined prey. If you are very lucky you can even spot a gloomy octopus (Octopus tetricus) ‘crawl’ from one pool into the next or discover a palm-size, blue-ringed octopus (Hapalochlaena sp) flashing its blue rings to warn you of its venom.

A great diversity of plant and animal life can be found in rock pools like this one at Narrabeen Head Aquatic Reserve in northern Sydney.

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Underwater Sydney

Extensive oyster reefs once decorated the harbour’s foreshore and provided nutritious food for Indigenous Australians. European settlers also benefitted from this resource and oysters were apparently casually chipped off the rocks during picnic outings. But 200 years of city growth almost wiped out the once common native Sydney rock oyster (Saccostrea glomerata) until in the 1990s rock oyster beds came back. Their come-back is likely to be a result of improved water quality due to better sewage and stormwater management from the 1970s onwards. The much larger mud oyster (Ostrea angasi), however, disappeared from Sydney Harbour by the mid1870s and has not returned since. Today native rock oysters grow alongside non-native Pacific oysters (Crassostrea gigas), which were introduced to Australia from Japan in the 1940s for aquaculture purposes. The larger Pacific oyster grows faster and produces more offspring. It has therefore outcompeted native rock oysters and other native intertidal species in many estuaries along the New South Wales coast. Reef-building oysters and mussels are important for the harbour’s health. Their rough, three-dimensional shells provide shelter for a host of creatures and, by filtering hundreds of litres of seawater through their large, sheet-like gills every day, filterfeeding oysters and mussels help to keep the harbour’s water clean. They can shape their environment so greatly that oysters and mussels that form living reefs are considered ecosystem engineers.

Oyster beds at Shiprock, Port Hacking.

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Underwater Sydney

Living side by side Cunjevoi (Pyura praeputialis), the knobbly, often overgrown ‘blobs’, can cover large areas on rock platforms of rocky reefs. These animals, although they may not look like one, are sea squirts and another important inhabitant of rocky intertidal shores. Similar to oyster and mussel beds, cunjevoi, by growing densely side by side, provide a refuge for many creatures such as chitons, limpets and snails that need a place to hide. Their filter-feeding action is equally important. Each ‘blob’ represents an individual animal that lives inside a rubbery housing, the tunic. Seawater enters the animal through one large opening, is pumped through a sac-like sieve where food particles are captured, and the depleted seawater leaves the cunjevoi’s body through a second opening. Interestingly, these animals can orientate so that the opening for incoming water is directed towards the swell and the opening for outgoing water is directed away from the swell. This simple adjustment can contribute about half of the total water flow through the animal and so make a huge difference in the amount of food each cunjevoi can capture. Cunjevoi are also popular with recreational anglers, who use the animals’ internal organs as bait. Up to 20 animals can be harvested legally per person per day. Whether this is a sustainable number is not known. But we do know that at popular fishing locations cunjevoi beds have decreased in size or have almost disappeared and most likely the plant and animal communities living on the cunjevoi have changed, too.

Close-up of a single cunjevoi animal with green, brown and red algae growing on the outside of its tunic. 20

Underwater Sydney

Pink turfs on rocky shores Many of the algae in the marine environment are not green. Red algae, for example, display the most striking arrays of red, pink, purple and orange due to a combination of pigments unique for this group. The algae’s distinctive red pigments absorb blue light, which penetrates deeper into the water. Red algae can therefore grow successfully in deeper water or under the canopy of larger brown and green algae. An exception are pale-pink coralline algae, which often grow as short, dense turfs or hard crusts in the shallows of rocky intertidal shores and on coral reefs, where light is intense. Turfing corallines are tough to the touch because their algal body is heavily calcified. Calcite, a type of calcium carbonate, on the surface of the cells helps to protect the algae from wave damage and grazers. When inspected closely, countless tiny invertebrates such as snails, worms and shrimp-like crustaceans can be seen living in the algal turfs; some specifically seek shelter in these turfs during their vulnerable juvenile life. The newly metamorphosed juveniles of the local brittle star Ophiactis resiliens, for example, live within the coralline turf while they grow up before they move underneath rocks, where the adults live. The young O. resiliens share the algae with other tiny brittle stars (Amphipholis squamata and Amphiura constricta) that never leave the algal turfs and give birth to their young in the algae, too.

Red coralline algae at Whale Beach, Sydney. Intertidal rocky shores

21

Tube worms Dense patches of white, squiggly tubes covering entire rocks belong to another common resident on Sydney’s intertidal reefs – the coral worm, Galeolaria caespitosa. The worm is only small, ~2 cm in length, but what it lacks in size it makes up in numbers. Thousands of individuals live side by side in their calcareous tubes, forming a living reef, sometimes several layers thick. When the tide is low the tubes are sealed with an umbrella-shaped lid, which the worm holds onto tightly. During high tide the white reefs change completely. Black worm heads covered in long, feathery tentacles emerge ready to capture food that is drifting by. Galeolaria produces eggs almost all year round and development from fertilised egg to juvenile takes only 2 weeks. The life cycle of this worm is well studied and the sperm or developing embryos are used for toxicity testing and exposed to toxic chemicals and metals. Very often the tested substance induces malformations in the embryos or reduces the ability of sperm to fertilise eggs successfully; this shows us that the substance may be harmful at higher concentrations. Non-mobile invertebrates in the intertidal zone are exposed more frequently to pollutants through stormwater run-off or other means, and the fact that they can’t escape puts these animals even more at risk.

A colony of Galeolaria tube worms in the intertidal zone. You can see the tiny trapdoors that seal the worm tubes during low tide. 22

Underwater Sydney

Going on a hunt at snail’s pace

A cartrut shell (top left) and mulberry whelk (bottom left) feeding on a barnacle at Bluefish Point, Manly. Spengler’s tritons (right) clustering off Shark Point, Clovelly. It is unclear whether they are feeding, mating or just enjoying each other’s company!

Not all snails on intertidal rocky shores are vegetarians. On the contrary, meat-eating snails are diverse and common. Some go hunting, others are scavengers and a third group prefers to ‘graze’ on animals living attached to the rocks. Cartrut shells (Dicathais orbita) kill other snails by drilling a small hole into the prey’s shell using their sharp teeth at the tip of their tongue combined with chemicals that dissolve the shell. The holes are drilled in specific locations so the cartrut shell has access to the most nutritious part of the prey animal. The mulberry whelk (Morula marginalba) is one of the most common predatory snails on rocky shores. It, too, gets access to preferred prey including barnacles, oysters and limpets by drilling a hole into their shell. Spengler’s tritons (Cabestana spengleri) have a different strategy. These tritons exclusively eat cunjevoi and to get to the soft tissue inside the tough housing or tunic, the snails ‘bite’ a chunk out of tunic with their muscular tongue and sharp teeth. Once there is a hole in the tunic, the cunjevoi is defenceless and the soft internal tissues are sucked out with the proboscis, a long tube that acts like a straw.

Intertidal rocky shores

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Cute but deadly – blue-ringed octopuses Slightly larger than a 50-cent piece and sandy brown in colour, this octopus is difficult to spot. The bright blue lines appear only when it feels disturbed and threatened. This is the moment to step away! Blue-ringed octopuses (Hapalochaena sp.) are some of the most poisonous creatures in the ocean. Their bite is deadly, not only to their fish and crab prey but to humans as well. Whether the octopus produces the nerve poison itself, incorporates it from its food or receives it from bacteria that live inside the octopus is not clear. Luckily for us these gorgeous animals are very shy and seek shelter as soon as they are discovered.

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Underwater Sydney

A foot to hold on tight Have you ever tried to peel a chiton off a rock? Once these animals feel your touch it is almost impossible to move them. These ancient-looking creatures are related to snails and their broad foot acts like a suction cup. Just as well, as oystercatchers are known to hammer or chisel chitons off the rocks during low tide and wrasses target the animals at high tide.

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Crustaceans of the other kind Anyone who has walked barefoot on a rock platform has surely cursed barnacles. Inside the armour-like, rock-hard shell lives a crustacean. The animal literally lives back to front with the head firmly attached to the rock surface and the feet moving freely about. At high tide, when food particles drift by, the feet, covered in fine hair, rhythmically expand in and out of the shell to capture food. But more strangely even is how most barnacles mate. For example, acorn barnacles (Balanus amphitrite), which are common in Sydney, are male and female at the same time. When it comes to mating season each animal extends a long, flexible penis out of the shell to a neighbouring barnacle to fertilise the neighbour’s eggs. Knowing this, you may not look at rocky shores covered in barnacles the same way ever again!

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Underwater Sydney

See intertidal rocky shores for yourself Ku-ring-gai Chase NP

North Narrabeen Long Reef

Sydney CBD

Little stars The cushion star Parvulaster exigua is the size of a fingernail and, having a mottled appearance, it is quite difficult to spot. But where there is one, there are several – in rock pools and on exposed rock baking in the sun. The sex life of this little starfish is fascinating. Some males change into females later in life and some adult stars produce eggs and sperm at the same time, disposing of the need for a partner. The eggs develop protected in a gelatinous egg-mass attached to rock and in less than a month miniature seastars hatch.

Foreshore walk from Chowder Bay to Taronga Zoo Coastal walk from Bondi to Maroubra

Botany Bay

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Oak Park

Intertidal rocky shores

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Cabbage Tree Bay Aquatic Reserve, Manly

Underwater forests

Sydney’s dramatic cliffs, headlands and rock platforms extend well beneath the water, where they form complex, three-dimensional rocky reefs. Here, steep rock walls, overhangs, piled-up boulders and underwater canyons offer a home to a myriad of creatures. In fact, these hard surfaces are colonised and inhabited so densely that shallow rocky reefs are some of the most diverse and productive environments in the ocean. Sydney’s reefs are colourful and lively environments. Swathes of algae, sponges in all shapes and forms, sea squirts and other animals grow and compete for space on the rock surface. Space is limited so competition is fierce. In the shallows, the rocks are mostly covered in a carpet of turfing algae, barnacles and bivalves. But well below the low-water mark, rich communities of brown, green and red algae unfold. These algae form the basis of the food web on rocky reefs. Like grassy meadows on land, algal beds feed many creatures, both great and small. Millions of tiny herbivores such as shrimp-like crustaceans can be found feeding on the plant matter. Such small herbivores are, in turn, a delicious meal for carnivores such as fishes and crabs. In crevices and underneath rocks, the small hunters and gatherers live out of predator sight. Attracted by the abundance of food, many fishes and several bottomdwelling sharks also call rocky reefs their home.

Kelp flourishes above red-algaeencrusted rock at Shark Point, Clovelly.

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Seaweed beds, particularly large, brown algae – also commonly called kelps – are key living habitats on rocky reefs. Kelps photosynthesise and form underwater forests not unlike trees on land, but they can’t be grouped together with terrestrial plants because their physical structure, which evolved in the ocean, is entirely different. Kelps have long, leathery fronds called ‘laminae’ that can withstand strong currents and waves. They have a ‘stipe’ for a stem or trunk, a hollow tube allowing the alga to grow towards the sun, and a root-like ‘holdfast’, which cements each individual to the rock. These algae can photosynthesise at almost any point along their body and they can absorb nutrients directly from the seawater in which they are immersed. At low tide, these unfamiliar forests come into view and the laminae and stipes can be seen at the surface along the water’s edge. Many harbours in the world are overgrown with non-native macroalgae. But not Sydney Harbour; here the local kelp Ecklonia radiata is still the most common and distinctive. Crayweed (Phyllospora comosa), another large brown alga with long, slender fronds and grape-like gas bladders, has not fared as well. Named after one of its main associates, the rock lobster or crayfish, it disappeared from Sydney’s coast in the 1980s due to heavily polluted waters. Good regulation, however, has led to much improved water quality since and scientists are re-introducing crayweed on Sydney’s rocky reefs. The results so far are promising. The transplants are growing healthily and have started to reproduce, which is great news for lobsters, abalone and many other species living in the sanctuary of its canopy.

Crayweed at Palm Beach. Palm Beach and Cronulla have the only remaining naturally occurring crayweed populations in the Sydney region.

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Under and around the protective canopy of kelp forests, many fish and invertebrate species thrive. Urchins, which are prominent on rocky reefs, love eating kelp in large quantities. Where there are many urchins, there is hardly any kelp, except in places the urchins cannot reach. Scientists call these kelp-free areas ‘urchin barrens’ and they occur naturally on rocky reefs. Sometimes, however, urchin barrens increase dramatically in size if predators such as wrasses, snappers and lobsters are not abundant enough to keep urchin numbers in check or when an urchin species migrates to new grounds where there are no natural predators. The long-spined black urchin Centrostephanus rodgersii, for example, has expanded its range south of New South Wales and is now a permanent resident in Tasmania, where it seems to adversely affect the abundance and behaviour of native species such as the black-lip abalone (Haliotis rubra), a commercially harvested species. The minute algae that grow like a film on the kelp surface are also a major food source for herbivorous fish and tiny invertebrates such as shrimp-like crustaceans and snails. So important are these herbivores that if they were not present the algae would get overgrown and become unhealthy. The cracks and crevices on rocky reefs are inhabited by other mobile invertebrates. Crabs, shrimps, snails, urchins, sea stars, octopuses and countless other animals go about their business hunting and gathering food. Small and cryptic fish species also like to hide in crevices. These animals are then food for the large predatory fishes such as pike, snapper, wrasse and bream. Sydney’s rocky reefs are bursting with life.

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The rock scraping by the urchin Centrostephanus rodgersii has led to this interesting rock sculpture at Shark Point, Clovelly.

Underwater forests

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Blue gropers and other wrasses Eastern blue gropers (Achoerodus viridis) are iconic residents along Sydney’s shore. These curious, charismatic and funny-looking fish will come and inspect you with an intense stare. Gropers with their thick lips and crooked teeth are much loved and legally protected from spearfishing, but you can catch them on fishing line. Gropers are one of the many colourful and fascinating wrasses on Sydney’s rocky reefs. Wrasses are famous for changing their colour and sex throughout their life. Juveniles are coloured differently from their parents, while males and females don’t look alike either. Wrasses live in social groups with one or two dominant males and in some species up to 40 females. Curiously, blue gropers, like many wrasses, are born female and only once the dominant male has died or there are too many females in the group will a large female turn into a male fish and lead the group. Wrasses are well adapted to foraging prey on the seafloor and their powerful jaws are made to crush hard food. Not surprisingly, wrasses, including blue gropers, feed on invertebrates such as shellfish, urchins, crustaceans and worms. The rubbery lips of blue gropers, for example, protect it from urchin spines and the odd, anvillike teeth allow the fish to ‘hit and smash’ or crush the shells of its prey. Blue gropers (top left) are curious and will come right up to you if you’re patient and still underwater. Maori wrasse (top right) at Shelly Beach, Manly. Maori wrasses like to feed on invertebrates disturbed by larger fish like stingrays – so they often follow divers, hoping for something stirred up by a diver’s fins. A senator wrasse (bottom right) on the move. These wrasses are hard to photograph as they dart off as soon as you approach them. Crimson banded wrasse (bottom left) at Fairy Bower, Manly. The male of the species is one of the more colourful fishes in Sydney’s waters.

What causes harm to rocky reefs? Submerged rocky reefs are impacted by coastal urbanisation similarly to intertidal reefs and seagrass beds. Even if they are not directly replaced by infrastructure, they are often heavily disturbed and fragmented through the building process. Poor water quality and sedimentation put additional pressure on kelp forests around urban centres. Recreational fishing, in particular, has an impact on the communities of Sydney’s rocky reefs. First, a lot of the debris found underneath jetties and beneath the foreshore is discarded and lost fishing equipment. Fishing lines are particularly dangerous as they often entangle marine life. Second, recreational fishing pressure is high in the harbour and along the Sydney coast. Many of the reefs have been depleted of the bigger sizes of the fish species targeted by anglers, such as snapper, mulloway and tarwhine. Lower order species such as leatherjackets and luderick are also targeted in the absence of more preferred fishes. This has a flow-on effect on the entire reef community as many of the larger predatory fishes targeted by anglers feed on invertebrates and other fishes. Marine reserves with no-take zones, also called sanctuary zones, can re-establish native fish assemblages including the large predatory fishes, natural levels of interaction between species and natural processes. They are not just about fish numbers. Cabbage Tree Bay Aquatic Reserve in north Manly is a wonderful example of a sanctuary zone and diverse rocky reef. The Reserve is teeming with fishes; it has twice as many fish species and four times the amount of fish compared to surrounding areas. Going for a snorkel there is like entering a different world.

A large school of luderick finds sanctuary in the Cabbage Tree Bay Aquatic Reserve in Manly.

Weedy seadragons One of the most unusual and rare fish along the Sydney coast is the weedy seadragon (Phyllopteryx taeniolatus). This beautiful, unique fish lives in and around kelp forests only in the southern parts of Australia. Seadragons spend their entire adult life in the same patch of kelp forest and different groups don’t seem to mix much. Like their cousins the seahorses and pipefishes, seadragons are unique in their care for their young. It’s just as well that the breeding season is up to 6 months long as the males court the females for several weeks and the females may show interest in more than one male at a time. After performing an elaborate dance, which involves curling tails and nodding heads, the female transfers around 200 eggs to the male’s brood patch underneath the tail. The eggs are fertilised afterwards and carried by the males for about a month before the babies hatch and live independently from day one. So tempting is the males’ precious cargo that toadfishes and leatherjackets sometimes take a bite of a male’s tail to get to some of the eggs. Scientists followed seadragon populations in Sydney and Tasmania for almost a decade and found that the number of animals was declining at some sites. Whether the decline had a natural cause or was due to changes in the environment caused by human activities and coastal developments is not known. The beautiful dragons are protected now. But considering that adult dragons don’t migrate and breed only few young, these animals would certainly benefit from the additional protection of their rocky reef habitat.

A weedy seadragon male with eggs at Kurnell. In Sydney, weedy seadragons prefer deeper waters along the kelp–sand interface, so they are rarely seen except by scuba divers.

Red and grey morwongs

A red morwong (left) rests in deep water at Henry Head, La Perouse. In winter there isn’t much light at 20 m depth, so the background to this shot is dark. The morwong is lit by a pair of strong camera strobes. A blue morwong (right) approaches the camera in shallow water at Fairy Bower, Manly.

Red morwong are a common sight on Sydney’s rocky reefs and are easily identified by their fleshy lips, red upper bodies and two little horns above the eyes. Males are larger than females and also have longer horns. Juvenile red morwong, smaller than 20 cm in size, spend most of their day foraging for food on shallow reefs. They feed mainly on small, shrimp-like crustaceans that they ‘suck up’ amongst algal turfs. Sand, pieces of shells and other indigestible items are spat out again or removed through the gills. Adult red morwong, on the other hand, live in deeper waters and prefer to feed at dusk or dawn or during the night. They go for larger prey such as crabs, chitons, snails and mussels, which they selectively pick of the rocks. Even juvenile sea urchins are crushed open and the internal organs eaten. One can understand why these fleshy lips can come in handy. The species is popular with spearfishers, and New South Wales authorities have used red morwong as an indicator of environmental pollution, specifically of heavy metals, off the Sydney coast. Unfortunately, some of the morwong collected near off-shore sewage outfalls had high levels of mercury in their flesh and therefore posed a health risk when consumed by humans. Less well known is the grey morwong (Nemadactylus douglasii), a shiny silveryblue fish that can grow up to almost a metre in size. These striking fish are good eating and are therefore commercially fished and marketed as ‘deep sea bream’. Officially overharvested, grey morwong now caught and sold are only 30–40 cm in size. Bigger sizes can sometimes be seen at Cabbage Tree Bay Aquatic Reserve and other sanctuary zones, where they are protected.

Powered by the sun – blue dragons Blue dragons (Pteraeolidia ianthina) are one of the gorgeous sea slugs that live on Sydney’s rocky reefs. Their body is covered with finger-like appendages called ‘cerata’, which have two very specific purposes. Inside each finger, countless photosynthetic algal cells convert sunlight into sugars for energy, which the minute algae share with their host. The slug must acquire the algae, either directly from the surrounding water or from food – we don’t understand how this happens. But they are not passed on to the next slug generation. The end of each ceras hides a surprise for would-be predators, too: stinging cells similar to those of jellyfish, which the dragon has also assimilated from the hydroids it eats. So beware when blue dragon mamas behave like angry dragons, defending their nest of developing eggs!

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An old wives’ tale Small schools of what look like butterfly fish dart back and forth among the kelp. These fish (Enoplosus armatus) are, however, not a type of butterfly fish but are a single species in their own group and they can’t be found anywhere else in the world. Their weird name, ‘old wife’, stems from the grinding noise these fish make with their teeth when they are caught and distressed. Yes, common names are rather inappropriate at times. Old wives are supposedly venomous, but they have neither a venom gland nor a glandular groove in their dorsal fin spine as is typical for other venomous fishes. So maybe the story of their venomous spines is an old wives’ tale!

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A crown fit for a queen or king On rocky reefs even the worms are pretty. This delicate, feathery crown belongs to the native fanworm, Sabellastarte australiensis (pictured above). Just like the segmented worm Galeolaria caespitosa in the intertidal zone, fanworms use their ornate tentacles to trap minute food particles drifting in the water. They also live in tubes, but these are made of sand and mud, not calcium carbonate like Galeolaria’s. Another fanworm found around Sydney is Sabella spallanzani. The name sounds Italian, doesn’t it? Well, this particular fanworm originates from the Mediterranean and probably came to Australia on the hulls of ships. As far as introduced species go, Sabella doesn’t seem to be as harmful as other introduced species. On the contrary, in some areas where Sabella settles the tubes provide habitat for many native species.

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A hazardous journey – eastern rock lobsters

See underwater forests for yourself Ku-ring-gai Chase NP

Cabbage Tree Bay

Sydney CBD

Botany Bay

Clovelly (outside pool)

Eastern rock lobsters (Sagmariasus verreauxi) are highly prized and rightly so. It takes years for a lobster to grow into its adult size and its life cycle involves a hazardous journey, too. Large female lobsters carry up to two million fertilised eggs under their tail until they hatch. The tiny lobster larvae have to moult more than a dozen times in order to grow. During this period, they are swept into the open ocean and carried away by currents. Once the transformation is complete, the baby lobsters return to the coast after up to 2 years in the plankton and settle in shallow rocky reefs. Here the juvenile lobsters grow for several years before they join the adults in deeper water and the complex lobster life cycle is complete.

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Bare Island, Botany Bay

Sponge gardens

Where rocky reefs extend into dimly lit, deeper water, different communities dominate the reef. Here, where little sunlight reaches, animals that live fixed to the rocky sea bed and don’t move (scientists call them ‘sessile’) have found their niche. Rich in colours and shapes these gardens are alive with animals that grow into beautiful three-dimensional sculptures. Sponges are the most diverse in colour and form, growing into branched bushes with finger-like extensions, balls, plates, mounds, fans and crusts blanketing rock like molten lava. Sponges are ancient animals, having lived on this planet for almost 600 million years. Their simple body, which is effectively a living water filter, puts sponges at the very base of the animal kingdom. Lots of minute pores on the sponge surface act as inlets through which seawater is channelled into the sponge, where specialised cells trap and absorb food items that move through with the flowing current. Eventually the filtered seawater is discharged through larger outlet openings, which often look and function like chimneys. Soft corals and hydroids also thrive in a darker world. Much like their relatives in tropical coral reefs, soft corals and hydroids form colonies, in which thousands of individual polyps connect to become a more complex organism.

Sponges display a range of growth forms at Kurnell, Botany Bay.

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Colonial animals in the marine environment are nothing like animal colonies on land, where many individuals, for example bees and ants, live together and share different tasks. Marine colonial animals are comprised of individual animals that are physically connected and often share body organs. Sometimes individuals in the colony have evolved to fulfil specific functions, for example the production of eggs and sperm or the protection of the colony. Marine colonies can grow indefinitely by cloning and therefore can rapidly adapt to local conditions. Sessile animal colonies are so successful in the ocean that the strategy has been adopted by diverse animal groups – sea squirts and moss animals, which are their own diverse invertebrate group, also live in colonies among the sponges and corals. If these animals live attached to the seafloor, how do they colonise new places? The answer can be found in the water at certain times of the year! Most marine invertebrates release their eggs and sperm into the open water, where they mix, fertilise and are then dispersed by currents, waves and tides. The developing embryos drift for days, weeks or even months and throughout this perilous journey develop into larvae, which in some cases resemble the parents, but more often look completely alien. The larvae can’t swim strongly and many settle down in unsuitable habitats and die, but scientists have found that some larvae follow settlement cues, for example chemicals released from adults of the same species, that indicate a good place to live. When the drifting larvae metamorphose into juveniles, miniature versions of the parents, they settle and start growing attached to the seafloor. So, without a vagabond larval stage, colonial animals wouldn’t be able to readily disperse.

Sponges interspersed with Carijoa soft corals, hydroids and ascidians at Shark Point, Clovelly. A red scorpionfish nestles, well hidden, among the diverse sessile life.

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Sponges are unable to move and can be soft, but they are by no means defenceless when it comes to predators. Their first line of defence is a body that mainly consists of spongin fibres, the squishy material we know from bath sponges, and small, sometimes needle-sharp, bony elements called spicules, that are embedded in the sponge tissue. So sponges are not particularly fun to eat! Their second line of defence is a range of toxic chemicals that are either produced by the sponges themselves or by microbes that live in and on the sponges. These poisons act as powerful deterrents against most predators. Many of these chemicals are of great interest to modern medicine. Some of the substances have antibacterial, antiviral or antifungal properties, which are of great value for the development of effective medication against multi-drug-resistant organisms. Other sponge products have been found to be effective against tumours and several of these compounds are now used in chemotherapy. Unfortunately, sponges and their microbes are notoriously difficult to cultivate, which at the moment limits the number of chemical compounds that can be produced at large scales. Despite the sponges’ wall of defence, some sea stars, urchins, fishes and sea slugs feed on sponges. Sea slugs, especially, have found ways to take advantage of sponges.

Shady areas, like under this ledge at Shark Point, Clovelly, allow sponges to flourish without competition from algae.

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An explosion of colour – nudibranchs The brilliant colours and wild patterns of nudibranchs are astounding. One would think that a soft-bodied animal without the protection of a shell and as slow-moving as a snail would avoid sticking out like a sore thumb. And, indeed, some nudies such as the brightly pink Okenia atkinsonorum prefer to camouflage themselves and take on the colour of their prey, which in Okenia’s case is the red moss animal Pleurotoichus clathratus. The majority of nudibranchs, however, delight us with their outrageous colours and shapes, which aim to be a warning signal for potential predators – do not eat me, I am toxic and taste awful! The many chemicals produced by sponges to deter would-be predators are, in fact, not only useless against certain nudibranchs, but help the slugs to defend themselves. Many slugs have evolved to only feed on one species of sponge and incorporate the sponge’s toxic chemicals into glands that release their poisonous content when the slug is threatened or bitten. Similar to blue dragons, Spurilla braziliana feeds on anemones and not only internalises the anemone’s stinging cells, but carries the undamaged cells in the tips of the long appendages that extend all over its body. When a predator takes a bite, the stinging cells burst, releasing their toxin. Curiously, nudibranchs are not always naked! The free-swimming larvae develop a shell, which is lost when the larvae metamorphose into juvenile sea slugs.

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Top row, left to right: Spurilla braziliana, Okenia sp., Jorunna sp. Bottom row, left to right: Ceratosoma brevicaudatum, Hypselodoris bennetti, Goniobranchus splendidus.

Wobbegong sharks Snorkelers and divers exploring rocky reefs often come across wobbegong sharks that lie still among the rocks, in crevices or on the seafloor. Sponge gardens, boulder fields and artificial structures provide good homes due to their three-dimensional structure. Two species live around Sydney: the banded wobbegong (Orectolobus halei), which has large, dark blotches on its skin and the spotted wobbegong (O. maculatus), which is covered in white, dotted rings. Both species have the typical flat body and fleshy whiskers projecting down from the upper lip. As a top predator, wobbegongs ambush large fishes and even other sharks. The banded wobbegong, for example, regularly eats smaller wobbegong species. Wobbegongs have been commercially fished since 1991 and their meat is sold as ‘flake’ in fish shops. Within a decade wobbegong numbers declined to less than half their previous numbers, suggesting that they were overharvested. This is not surprising. Females only reproduce every 3 years and are pregnant for almost 1 year before they give birth to up to 50 pups. The New South Wales Government has since restricted the number of sharks that can be taken in the Ocean Trap and Line Fishery to six animals and wobbegongs caught by recreational anglers have to be released. Since these restrictions have been put in place, the number of wobbegong sharks harvested has decreased, but whether wobbegong populations are recovering is not known yet.

A spotted wobbegong resting under a ledge at Fairy Bower, Manly. Wobbegongs are easy to photograph as long as you don’t get too close.

Eastern blue devils Another rather rare resident of Sydney’s shallow and deeper rocky reefs is the eastern blue devil (Paraplesiops bleekeri), a colourful and eye-catching devilfish. Eastern blue devils only live along the New South Wales and southern Queensland coast in Australia. Unfortunately, their striking appearance has been detrimental to this species as wild specimens were collected for the aquarium trade. The New South Wales Government officially listed this fish, once it became rare in the wild, as a protected species in 2006. During the day, blue devils like to rest in caves or under ledges and emerge at night to hunt. Not much is known about the eastern blue devil’s diet, but, curiously, brittle stars seem to be a regular menu item. Its close relative the southern blue devil feeds on crabs, shells and fishes. Male blue devils are territorial and will attack other males to protect their refuge, but females are a different story. During the mating season these solitary fish pair up. The female then attaches thousands of tiny, sticky eggs onto the ceiling or a crevice of the male’s cave and disappears again. It is the male that guards the eggs until they hatch several days later. When the newly hatched baby devils leave their shelter, they are only 4–5 mm in size and live in the plankton.

Eastern blue devil fish under a ledge at Shark Point, Clovelly.

Sea tulips – a most unusual partnership Among the sponges, sea tulips – clumps of knobbly purple or yellow ‘heads’ – grow on stalks. These creatures are not one but two animals: a partnership between the stalked sea squirt Pyura spinifera, a sister species of the intertidal cunjevoi, and the pink or yellow sponge Halisarca laxa, which covers the sea squirt’s entire body. This is a tight-knit relationship, but what do the partners get out of it? We don’t know for certain, but the sponge certainly gets to live in a prime position on the reef and the sea squirt doesn’t have to deal with other fouling organisms. The relationship between the two animals is, in fact, more complicated than this because the Halisarca sponge first colonises another sea squirt (Cnemidocarpa pedata), which grows directly on the rocky sea floor, before it gets to live on the sea tulip in loftier heights. Once the sponge and the ascidian Cnemidocarpa are united, they induce the larvae of the stalked sea squirt to settle nearby, which allows the sponge to keep growing onto the sea tulip and eventually cover its entire surface. The world of sessile invertebrates is a strange one indeed!

The trio of the two ascidians and sponge at Henry Head, La Perouse. Each bunch of stalked ascidians (Pyura spinifera) is accompanied by the squat ascidian Cnemidocarpa pedata at the base and both are completely overgrown by the sponge (Halisarca laxa). But there are more ascidian species in this photograph! Can you see the flared syphons of some algaeencrusted ascidians in the background?

Glowing cheeks – pineapple fish Pineapple fish (Cleidopus gloriamaris) like to hang out in caves, under ledges and in gloomier depths, too. Funnily enough, their skin really does resemble a pineapple, but what’s more fascinating about these fish is the presence of a light organ on each side of the lower jaw. The organs consist of a pouch filled with red symbiotic bacteria that produce an eerie glow. The fish use their living lanterns to detect and maybe attract prey at night.

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Growing with every tide Soft corals like Dendronephthya australis are uncommon in Sydney Harbour. In Port Stephens, within the Port Stephens–Great Lakes Marine Park, these soft corals are much more common and support a unique fish community including seahorses and juvenile snapper, which find shelter among the colonies. Unlike corals on tropical reefs, most soft coral colonies don’t build a hard, calcium carbonate skeleton. Instead, their body is held up by minute, spiny skeletal elements called ‘sclerites’ and by water pressure, which changes with every tide. While the tides are going in and out, the soft coral Dendronephthya australis increases in size up to four times and the polyps open to catch planktonic prey with their tiny tentacles. During low-flow conditions at slack water, the colonies retract, releasing water from their bodies, and the polyps close. Imagine quadrupling your body size every six hours and then shrinking to normal size for an hour over and over again.

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Catching food in the comfort of home Crustaceans, worms and other invertebrates take shelter in the porous surface of sponges and the intricate colonies of moss animals, sea fans and hydroids. This beautiful moss animal colony is home to several brittle stars, who extend and wave their spiky arms to catch food that drifts by. Brittle stars will sacrifice their arms if they are in danger of being eaten. The stars can drop and regrow their aims repeatedly. Imagine if we could regrow our arms and legs!

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See sponge gardens for yourself

Plant or animal? Flame-red and orange sea fans decorate the deep harbour floor and some of the underwater vertical cliffs of Sydney. Sea fans are soft corals, but their delicately branched bodies are not held up by water pressure alone. The coral polyps produce tiny skeleton pieces that are embedded in a horn-like material, a protein called gorgonin, which gives the colonies an elastic quality and thus allows sea fans to live at exposed sites.

Ku-ring-gai Chase NP

North Head Sydney CBD

Shark Point (Clovelly)

Botany Bay

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Narrabeen Head

Beaches and seagrass meadows

Sydney’s coastal beaches are famous! Who hasn’t heard of Manly or Bondi Beach? What may be less well known are the beaches inside the harbour; there are more than 50. With the exception of birds, dogs and humans, these Sydney beaches appear largely devoid of life, but this is deceptive. The real action on a beach takes place below the surface, where countless minute invertebrates, many not visible with the naked eye, occupy the tiny spaces between the grains of sand. Food is hard to come by here and many of the worms and crustaceans, some of them living in their thousands per square metre of sand, consume the decomposing organic material that has been washed up on the beach and buried in the sand. Molluscs such as tiny snails and bivalves filter the water between the grains. Plant life on the beach exists either as microscopic phytoplankton or as so-called ‘wrack’ (washed-up dead seagrasses, seaweeds and other algae). The word ‘wrack’ stems from the Middle Dutch word ‘wrak’, which means wreckage or wrecked ship. Many small critters have been found living in stranded wrack, among them flies, beetles and many little prawn-like crustaceans such as beach hoppers. These invertebrates, in turn, are food for shorebirds such as plovers, and for fishes at high tide. Most of Sydney’s beaches, however, are mechanically cleaned several times a week to remove any rubbish including wrack. So, while we all appreciate a clean beach, we are depriving beach wildlife of an important source of food.

Wrack on Turimetta beach.

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In shallow, protected bays, beaches extend into lush green seagrass meadows. With the exception of the paddle grasses (Halophila sp.), which have oval-shaped leaves, seagrass leaves are shaped like long thin blades, hence their common name ‘seagrass’. And although they are not real grasses, they are the only flowering plants that have adapted to life in the ocean. Botanically, seagrasses are related to arum and flamingo lilies. Their roots anchor them into the sand, and rhizomes – elongated underground tubers – give rise to new, genetically identical shoots that remain connected to the parent plant. Established seagrass meadows grow in size by cloning, and the extensive networks of rhizomes, dense mats several metres deep and sometimes hundreds of years old, form an effective erosion barrier. Seagrasses also reproduce sexually and the modest flowers are pollinated by currents, although, more recently, scientists have watched little crustaceans act like underwater bees. The crustaceans visited male seagrass flowers to feed on pollen grains and, by moving from flower to flower, also fertilised female flowers in the process. The developing seeds can be as tiny as a pinhead or as large as a pea or podded bean. Australia is home to over half of the 70-odd seagrass species worldwide, most of which live in the tropics. Here, along the Sydney coast, three types of seagrasses can be found: eelgrasses of the genus Zostera and Heterozostera, the southern strapweed (Posidonia australis), and the paddle grasses (Halophila sp.).

Seagrass meadow at Quarantine Bay with Halophila and Zostera plants.

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Seagrasses support a complex food web. Three distinct communities utilise the grasses: algae and animals small enough to live on the actual seagrass stems and leaves; larger, travelling animals that seek out the beds for food and shelter, but may move in and out of those beds; and animals that live on and in the sea floor and eat the decomposing seagrass material. On closer inspection, seagrass leaves look somewhat furry because their surface is overgrown with algae and animals. It is this growth that serves as food for the many freely moving animals such as small crustaceans, snails and fishes. Surprisingly, little live seagrass is eaten – only once the seagrass has died and partially broken down does it become a valuable food source. Predators such as shrimps and fishes, including species we like to eat such as trevally (Pseudocaranx georgianus), tarwhine (Rhabdosargus sarba) and leatherjackets (for example, Meuschenia trachylepis and M. freycineti) benefit from the large number of herbivores living among the grasses. Many of these fishes grow up in seagrass meadows and then move to other habitats such as rocky reefs.

A colourful nudibranch, Dendrodoris denisoni, moves through the sand and seagrass.

Silver trevally (Pseudocaranx georgianus) feed in the seagrass by scooping up sand and eating the invertebrates within.

Ghost crabs – the canaries in the coalmine The smooth-handed ghost crab (Ocypode cordimana) is one of Sydney’s local beach residents. Its burrows are scattered on the upper beach and small piles of dug-up sediment next to the entrance reveal that someone is home. At night, under the protection of darkness, ghost crabs, about the size of a 50-cent piece (including legs) and as pale as their name suggests, emerge from their burrows to hunt for food on the beach. Ghost crabs have been studied widely in order to understand the impact of human activities on beach organisms. Not surprisingly, beaches that are packed with visitors year-round and mechanically cleaned daily are less attractive to ghost crabs and few burrows can be found there. And while we all understand the need for foreshore protection, the replacement of natural dune systems with seawalls and other urban infrastructure has robbed many beach creatures, ghost crabs included, of a place to live. In Sydney Harbour the frequent, mechanical cleaning of beaches seems to have the largest impact on ghost crab numbers. Chinamans Beach stands out in that it is not mechanically cleaned and is the only beach inside the harbour that still has an intact sand dune system and the largest number of ghost crabs that call it home. If we take the needs of wildlife into account and clean beaches less often and less mechanically, and restore or maintain natural sand dunes systems where possible, we can share Sydney’s beautiful beaches with more wildlife!

A young ghost crab scurries along the sand at night on one of Sydney’s few remaining ungroomed beaches.

Southern strapweed The southern strapweed Posidonia australis is the largest of the seagrasses in Sydney Harbour. Its leaves grow into ribbons more than half a metre long. Once common along the New South Wales coast, Posidonia meadows now cover a fraction of the area they populated in the 1940s. Their disappearance, slow growth and difficulty to re-establish prompted the New South Wales Government to declare these meadows as endangered in five New South Wales estuaries. Recently, scientists analysed high-resolution aerial imagery of these estuaries, including Sydney Harbour, and discovered that Posidonia meadows have continued to shrink in size. In Sydney Harbour, Posidonia is disappearing at an alarming rate of 10% per year despite its protection. If the current rate continues, these meadows could disappear within a decade. In general, seagrasses have taken a hit. Foreshore developments have replaced and continue to fragment seagrass meadows in the harbour while stormwater runoff carries sediments, pollutants and nutrient-rich water into the estuary, affecting the ability of seagrasses to photosynthesise. Managing water quality and minimising the impacts of coastal developments are therefore a priority. Boating activities and moorings – there are more than 4000 mooring sites inside the harbour – are particularly detrimental to seagrass meadows. Anchors and propellers damage the grasses directly, while the swinging chains of boat moorings scour and turn over the sediment, ripping out seagrasses in the process. ‘Seagrassfriendly’ moorings, which replace the mooring chain with a stiff rod suspended above the seafloor, are effective in not harming seagrasses growing in the vicinity. With such an easy solution available, why wouldn’t we use seagrass-friendly moorings when and where we can?

Posidonia seagrass enjoys good natural light in shallow water in Sydney’s North Harbour.

A Nobel Prize winner Sea hares (Aplysia sp.) live among the seagrass beds in Sydney Harbour. The hares are, in fact, giant sea slugs, and there is a lot more to them than their pointy rabbit ears, floppy wings and squishy, brown/green-mottled bodies suggest. Almost two thousand years ago, the Roman naturalist Pliny the Elder mentioned sea hares in his encyclopaedia Historia Naturalis (~60 AD). In his accounts Pliny declares the hares’ poison capable not only of dispatching emperors, but also of causing nausea and vomiting in a pregnant woman who ‘so much as looks upon one of these fishes’. Though sea hares use chemicals extracted from their algal food to make themselves taste unpleasant, they are not poisonous. If you have ever come across a hare, you may have been up for a surprise. When touched or disturbed these animals secrete a dark purple ink, which aims to distract potential predators by confusing their sense of smell. The hares themselves are very sensitive to chemicals and use their ‘ears’, called rhinophores, as sensory organs with which they smell under water. Female sea hares lay up to 41 000 eggs per minute, which equates to almost 700 eggs per second. Each of the spaghetti-like egg masses can contain more than 80 million eggs. And that’s not all – a female can lay several egg masses over several months and can therefore produce over a billion eggs in her lifetime. Their real claim to fame is their huge nerve cells, which can measure more than 1 mm in diameter and are the largest found in nature. Sea hares may not be the smartest, but they can learn and remember, which makes them ideal model organisms to study how nerve activities relate to brain functions and so these curious animals have contributed to medical research that has earned researchers a Nobel Prize.

A sea hare (Aplysia juliana) feeds on sea lettuce at North Narrabeen on Sydney’s northern beaches.

Little penguins Little penguins (Eudyptula minor), the smallest penguins in the world, are one of Sydney’s most celebrated residents. The Manly breeding colony is the only mainland colony remaining along the New South Wales coast and it is fiercely safeguarded by local residents, the volunteer Penguin Wardens. The little penguins spend at least 9 months of the year at Manly, where they raise their chicks in the sheltered bays of the harbour. The same pairs return annually to the same nesting site to start a family, putting themselves at risk of collision with the human world. In 2015 one fox alone killed 27 little penguins at the start of the breeding season before it was captured. Pet dogs, too, are a danger, but the Manly breeding grounds have been declared a ‘critical habitat’ and today dogs are not allowed anywhere near the birds. The critical habitat includes rock platforms, beaches, foreshore areas, and ridge tops covered in native vegetation, where the penguins nest in rock crevices, burrows and nest boxes. Within the habitat, restrictions have been placed on activities such as fishing or boating from dusk till dawn, when the penguins are most active. The protected habitat also extends 50 m from the mean high water mark into the harbour in order to give the penguins easy access to their nests. The habitat includes seagrass beds, which are used by the penguins to hunt for food nearby. Before the fox attack in 2015, around 60 penguin couples returned every year to Manly to raise their chicks. Since then, only around 40 pairs have returned, but a good breeding season in 2017/2018 suggests that the penguins who lost their mates in the attack have successfully bonded with new partners. This is encouraging and with support from the Penguin Wardens we hope to continue to see these gorgeous birds nesting on Sydney’s beaches.

A little penguin near the entrance to its nest in the bushes.

Purple flying gurnard – an ocean butterfly When it feels threatened, the ordinary looking purple flying gurnard (Dactyloptena orientalis) suddenly turns into a beautiful ocean butterfly. Adapted to life on the sea floor, three of the gurnard’s pectoral fin rays are used for walking and probing for prey. The remaining pectoral fins are wing-like and are spread to put off any predators exposing false eye spots, which make the animal appear much larger. Funny that a fish and flying insects such as butterflies can have the same strategy when it comes to fooling predators!

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A pair of mourning cuttlefish (Sepia plangon) are displaying their gender specific body patterns. The male on the left exhibits a pattern of pulsating white stripes on a dark brown body while the female on the right has a lighter, mottled camouflage pattern.

Masters of deception Cuttlefish communicate through colour displays on their bodies. Within seconds they become invisible, show their anxiety, warn opponents, charm the opposite sex or fool competitors, all by rapidly changing the size and shape of the pigment cells in their skin. Mourning cuttlefish (Sepia plangon) are particularly sneaky and the males regularly cheat to win a female’s heart. Some of the males simultaneously display two different patterns on their body; the side facing an interested female is covered in white stripes, the male’s courtship pattern, while the other body half facing a rival male displays a female pattern. This prevents the rival from attacking the competitor and disrupting the courtship. If you are a cuttlefish, being a cheat pays off!

Beaches and seagrass meadows

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A common stingaree (Trygonoptera testacea, left) at Fairy Bower, Manly. The small dorsal fin is one specific feature of this species. Another species of stingaree at Fairy Bower (Trygonoptera imitata, top left) has no dorsal fin. A third species of stingaree at Fairy Bower (Urolophus kapalensis, top right) has a distinctive dark eye mask.

Watch your step! When stingarees are not slowly cruising over the sea floor to hunt, they often rest half-buried in the sand. These animals may pierce you with their venomous spine if they are taken by surprise and accidently stepped on, but generally they will shuffle away to escape. Smaller than stingrays and with a rounded fin at the end of the tail, the common stingaree (Trygonoptera testacea) is only one of several species that live along the Sydney coast. But telling them apart is tricky and relies on the colour pattern of the skin and the small dorsal fin.

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Pipefishes and co.

See seagrass meadows for yourself Ku-ring-gai Chase NP

Manly Cove Shelly Beach Quarantine Bay Balmoral Camp Cove Rose Bay

Botany Bay

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Tiger pipefish (Filicampus tigris) are one of the many small fishes that hang out among the seagrasses in Sydney, where they blend in well when they sit still on the sandy sea floor. Like their cousins, the seahorses and seadragons, pipefishes have a long, narrow snout with which they catch tiny, drifting organisms, and it is the dad that looks after the brood. Interestingly, pipefishes and their relatives can be used as a flagship group for conservation because places that support large numbers of pipefishes and seahorses tend to support diverse fish communities, which generally benefit from protection.

Beaches and seagrass meadows

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Homebush Bay

Mud and mangroves

In sheltered bays inside the harbour and along the banks of the Parramatta and Lane Cove rivers, small mangrove trees fringe the intertidal shore. Like trees on land, mangrove trees have roots that anchor the plants into the ground and a wooden trunk with branches and leaves. And while most plants can’t stand ‘wet feet’, mangrove trees thrive in the wet and brackish conditions of an estuary. The word ‘mangrove’ is often used to describe a whole community of trees, shrubs and animals. The most diverse mangroves are found in the tropics, but Sydney has its own mangrove communities. There are two species of mangrove trees, the grey mangrove Avicennia marina and the river mangrove Aegiceras corniculatum, that grow in Sydney and in southern New South Wales. The roots of mangrove trees are essentially waterlogged and surrounded by anoxic sediments so the trees can’t breathe through their underground roots. They combat this through aerial roots called pneumatophores – ‘pneumato’ meaning ‘air’, ‘breath’, ‘spirit; and ‘phore’ meaning ‘bearer of’ – which are sent into the air from below the surface. These aerial roots, which give mangroves their characteristic look, take up oxygen from the air and supply it to the tree, and they assist in anchoring the tree into the soft sediment. With their extensive root system, which can extend many metres from the tree, mangrove forests stabilise the soft sediment and prevent erosion of the shore. Excessive salt is toxic to most plants. So how do mangrove trees deal with the seawater surrounding them? Both grey and river mangroves have special salt glands in their leaves, which secrete excess salt. When the water evaporates, the salt on the leaf surface becomes visible as small white crystals. One can see them on the undersurface of the leaves. Water absorbed through the roots is also filtered so less salt enters the plant and, as a third strategy, grey mangroves deposit excess salt in socalled sacrificial leaves, which are dropped at some stage. Interestingly, mangrove trunks were widely used for mooring piles as they are fairly resistant to shipworms of the family Teredinidae.

Mangrove trees with pneumatophores and seedlings in the foreground. Sydney Olympic Park.

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Both land and marine animals make use of Sydney’s mangrove vegetation. Birds such as lorikeets and honeyeaters visit the mangrove trees when they are in flower, and insect-eating birds and bats feed on the mosquitos, flies and spiders hidden in the forest. Cormorants nest and breed among the mangroves and other shore birds forage in the mud for worms and small crustaceans. Hard surfaces are mostly lacking in mangrove forests, but some oysters, tubeworms and barnacles live attached to the pneumatophores, trunks, branches and even the leaves of the mangrove trees. Snails and crabs are common on the muddy seafloor, where they nibble on the dead plant material, but some snails such as the mangrove periwinkle (Littoraria luteola) and the limpet Patelloida mimula prefer to live up high in the trees. Few fishes live permanently in mangrove forests; instead most fishes move in and out of mangroves with the tides. Juvenile fishes, in particular, like mangrove habitats because they provide shelter from larger predatory fishes, and so juvenile yellowfin bream (Acanthopagrus australis), luderick (Girella tricuspidata), flathead (Platycephalus fuscus) and whiting (Sillago ciliata) spend some of their youth among the roots in the mangrove shallows. Here, they are accompanied by the juvenile stages of many crustaceans.

Ravens take advantage of the shelter and food supply in the mangroves.

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Saltmarsh communities occupy the upper reaches of intertidal soft sediments in the harbour’s sheltered bays, growing side by side with mangroves. Less than 10% of saltmarsh habitats have survived since European settlement due to urban development and more recently due to the expansion of mangroves with increasing sedimentation in the harbour. Sydney Harbour being a drowned river valley with a steep, often rocky foreshore provides little space for saltmarsh communities and the areas of saltmarsh that existed in the harbour have largely been lost. In 2004 coastal saltmarsh was declared an Endangered Ecological Community by the New South Wales Government. Saltmarsh communities comprise annual and perennial herbaceous plants such as creeping brookweed (Samolus repens), grasses, sedges and rushes, which grow no taller than half a metre. Introduced grasses and flowering plants have also taken hold among the native species. The lower areas of a saltmarsh are often occupied by coastal succulents that have fleshy leaves and stems. Like mangroves, saltmarshes are home to both terrestrial and marine animals. Insects and spiders are common and so are crabs and snails. These in return are food for wetland and wading birds, insectivorous bats and the native water rat (Hydromys chrysogaster), which inhabits Sydney’s bushy foreshore and has also been reported to forage in saltmarsh habitat along the New South Wales coast. The seeds of the beaded samphire (Sarcocornia quinqueflora) are a preferred food for the critically endangered orange-bellied parrot (Neophema chrysogaster), which overwinters in wetlands on the coasts of Victoria and, locally, the two largest patches of saltmarsh habitat in Sydney (Newington Nature Reserve in Sydney Olympic Park and Towra Point at the Georges River) are critical for the survival of a local population of another gorgeous bird, the white-fronted chat (Epthianura albifrons), which has been declared ‘vulnerable’ under the Threatened Species Conservation Act 1995.

Intertidal mud (lightly coloured) gives way to dark red-green saltmarsh vegetation and then trees at the Waterbird Refuge, Sydney Olympic Park.

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Wetland restoration – Sydney Olympic Park Sydney Olympic Park is a success story in conservation. Nowadays the Park is home to the largest saltmarsh community in the Sydney region, covering around 20 ha of foreshore parkland, and most of these communities were established from plants propagated at a nursery on site and transplanted to remediated sites. Many of the propagated saltmarsh plants include succulents such as the rare narrow-leafed wilsonia (Wilsonia backhousei), the beaded and blackseed samphire (Sarcocornia quinqueflora and Halosarcia pergranulata respectively), the austral seablite (Suaeda australis) and the little noonflower (Lampranthus tegens), which was described in Australia, but may originate from South Africa. A diversity of succulent plants found in boggy saltmarsh seems counter-intuitive considering we know succulents from arid regions, where the fleshy leaves and stems are used for water storage. However, succulence is an adaptive feature in many plants that grow in salty environments and it contributes to the regulation of salt inside the plant tissue. Succulent saltmarsh plants are able to control salt levels in their tissue by varying the amount of water internally. In saltier conditions the plants store more water in their tissue to counteract an increase in salt intake. These days the juicy, slightly salty little stems of samphire and some of the other coastal succulents are celebrated as a delicious bush food.

Beaded samphire, also known as glasswort (Sarcocornia quinqueflora), in the saltmarsh of Badu Mangroves at Sydney Olympic Park.

Bioturbation – reworking the sediments The muddy sediments, composed of fine silt, clay and organic matter, where mangroves and saltmarshes flourish are defined by poor drainage and a lack of oxygen below the top few centimetres of sediment. Microbial communities on the surface use the available oxygen to digest organic matter while microbes in deeper sediments metabolise other chemical compounds to produce energy. You may have noticed a rotten-egg smell walking alongside mangroves. The smell is a result of sulphides produced by microbes in anoxic sediments. The lack of oxygen deeper in the sediment means that most animals live in the top 10 cm. Similar to sandy beach communities, worms, small shrimp-like crustaceans and bivalves make up the bulk of larger invertebrates living in the sediment. Many of these creatures build and live in tubes and burrows, while others dig their way through the sediment, allowing fresh seawater and oxygen to seep through the mud. This reworking helps to change the structure and chemistry of sediments.

Sydney cockle shells (Anadara trapezia) litter the shoreline among the mangroves of Lane Cove River.

A case of metal poisoning The sediments of Sydney Harbour’s seafloor, especially the fine, muddy sediments in the sheltered bays and along Parramatta River, are not only home to mangrove and saltmarsh communities, but they also contain a cocktail of toxic chemicals and heavy metals, which are a relic of past industrial waste management practices. Many of these compounds find their way into the food chain through organisms that live on or in soft sediments and are food for other animals. The toxins are also directly absorbed through the skin and gills. Some of these chemicals and metals are linked to disrupting the production of sex hormones that regulate the reproductive cycle of marine animals. Smooth toadfish (Tetractenos glaber) are very common along the Sydney coast and in the estuary. They belong to the pufferfishes and, like their relatives, have a characteristic barrel shape and are poisonous. Smooth pufferfish like to hang out at the seafloor and burrow themselves into the sediment. They feed on crabs, mussels and worms in the sediment. Due to this lifestyle smooth toadfish are exposed to high levels of toxic metals such as cobalt, cadmium and lead, which have been found in the gills, muscle tissues, livers and gonads of these fish. The exposure and uptake of metals have consequences for the fish’s reproduction. At particularly polluted sites some female toadfish produce smaller and fewer eggs, while some male toadfish produce a protein, which is later turned into egg yolk and normally only found in the blood of females.

A smooth toadfish (Tetractenos glaber) buries itself in the soft sediments of the Sydney estuary.

Microplastic pollution Pollution from stormwater run-off is a big concern and new contaminants, for example from cosmetic and other domestic products or antifouling paints, are making their way into the harbour continuously. Microscopic pieces of plastic, so-called microplastics, are another type of pollutant that has only fairly recently emerged and there is great concern about the plastics’ environmental and health impacts. When harbour sediments were recently searched for microplastics, it turned out that they were everywhere. Up to 100 microplastics were found in 100 mL of sediment! Embayments with low water flow were polluted the worst. Interestingly, microplastic pollution was not worse near stormwater drains, indicating that these tiny plastics readily disperse in the harbour, and most of the microplastics found in the sediments were synthetic fibres from clothing. Microbeads from cosmetic products and tiny fragments of plastic were, in fact, rare. Polyester and acrylic fibres used in clothing are the most prevalent microplastic component found in habitats that receive sewage discharges. When scientists sampled the wastewater from domestic washing machines, they found that a single garment can produce more than 1900 fibres in a single wash. This suggests that a large proportion of microplastic fibres found in the marine environment stem from washing of synthetic clothing. Knowing this, should we reduce the amount of synthetic clothes we buy, considering that natural fibres require land, water, fertiliser and pesticides in their production? So how can we convince the manufacturers of washing machines to develop a filtration system that reduces the amount of fibres released into wastewater? And should new sewage treatment plants remove microplastics before the sewage is released? It is important that we find solutions for questions like these to prevent these pollutants from entering the harbour.

Microscopic plastic fibres that have been filtered from beach sand collected at one of Sydney’s beaches. Photo credit: Inke Falkner.

Mangrove propagules take root along the edge of the Sydney estuary.

Mangrove productivity Mangrove forests are very productive environments and the dropped leaves, branches, flowers, seeds and seedlings provide nutrients for the forest and food for the many animals that feast on organic material and decomposing litter. Where mangrove trees grow in front of seawalls there is less leaf litter on the seafloor, the depth of mangrove forest is reduced and the trees grow more pneumatophores compared to mangrove forests unimpeded by seawalls. Scientists are currently investigating how these differences could be linked to the presence of seawalls. Mud whelks (Pyrazus ebeninus and Velacumantus australis) and an abundance of tiny snails live among the decaying leaf litter and feed on dead plant material, as does the semaphore crab (Heloecius cordiformis), one of several crabs that live in mangrove forests. Mangrove seeds are particularly welcome meals for insects and crabs. Mangrove trees are special in that the seeds germinate when they are still attached to the parent tree. This gives the young seedlings a head start so when they drop onto the muddy seafloor they can start forming roots within days. So next time you find a bright green, roundish pod washed up on the beach in Sydney Harbour, take it home with some mud and seawater to grow your own mangrove tree!

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Walking on silts Black-winged stilts (Himantopus himantopus) are one of several wading bird species that have returned to Homebush Bay. With their long, pointy beaks these pretty birds catch insects and marine invertebrates while wading through shallow water with their bright red, disproportionately long legs.

Mud and mangroves

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Not your typical rat Rats are usually not a welcome sight unless we happen to see or talk about the native water rat or rakali (Hydromys chrysogaster), who lives along the harbour’s foreshore. These native rodents are larger than the European black rat that arrived with the First Fleet and they are superbly adapted to an aquatic life. With a water-proof pelt and toes that are joined by skin to create effective paddles, water rats are excellent swimmers and are happy to forage for food in the water. Curious and highly intelligent, female rats will teach their young several tricks for catching food.

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Photo credit: Ann Killeen.

Mangrove crabs

See mud and mangroves for yourself

Together with snails, crabs such as semaphore crabs (Heloecius codiformis) are the other obvious inhabitant of mangrove forests. Semaphore crabs belong to the same family as the ghost crabs we find on beaches and the two animals have a very similar lifestyle. During low tide semaphore crabs are very active on the mangrove floor, feeding on plant waste and microscopic algae, and during high tide the crabs hide in their shallow burrows, which they plug with a ball of mud. If you go on an excursion to find semaphore crabs in winter, you will have no luck because the crabs spend the winter months in their burrows and are more than happy to use their claws to defend their burrow against other crabs!

Ku-ring-gai Chase NP

Sugarloaf Point Olympic Park

Sydney CBD

Botany Bay

Towra Point

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Mud and mangroves

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The Spit

Novel habitats

Despite its natural beauty, Sydney Harbour is a highly modified and largely humanmade environment. Long stretches of harbour foreshore consist of reclaimed land, armoured with sandstone and concrete seawalls to provide a stable footing for foreshore developments and protection from the sea. In addition, wharfs, marinas, pontoons and jetties with pilings are dotted all along the coast and inside the harbour to support the many boating and shipping activities. This multitude of marine infrastructure not only has replaced and fragmented natural intertidal and subtidal environments, but it also provides artificial or ‘novel’ habitats, which support plant and animal communities that haven’t existed before, often dominated by non-native species. If you imagine a natural rocky reef, it is generally flat or gently sloping with lots of places to hide and seek shelter, such as cracks and crevices, dips and pools, rocks and boulders. Marine infrastructure such as seawalls and jetty pilings, on the other hand, typically has a vertical, smooth surface, which greatly reduces the diversity of habitat niches and attachment sites for local plants and animals. In addition, marine infrastructure changes the light and water-flow conditions of its surroundings.

Under the jetty in Clifton Gardens, Mosman.

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Estuaries and busy harbours are prime destinations for non-native plants and animals to take up residence because harbours often represent the most disturbed marine environments. Disturbances, like dredging and development, open up opportunities for invasive species to take hold. Harbours are also naturally exposed to more non-native species through their shipping and boating activities, as vessels can carry foreign organisms on their hulls. Curiously, environmental pollution also plays a role in the spread of non-native organisms. Ship hulls are treated with toxic antifouling paints, which prevent most marine plants and animals from growing on the hulls. Some species, however, are resistant to these paints, which often contain high levels of the heavy metal copper. The species that can resist the paint, and thus can travel to far-flung places, are also likely to be more tolerant to toxic chemicals in polluted harbours. Fouling species therefore have an advantage over the local flora and fauna, which may not cope as well with the polluted environment. Marine infrastructure often provides a stepping stone for these opportunistic fouling species by providing a ‘blank canvas’ to colonise and on which to successfully multiply. The underside of a pontoon, for example, resembles a boat hull in many ways and therefore is perfect for an arriving species to ‘jump ship’ to. When the new arrivals start dominating and out-competing native communities, they become ‘invasive’. Making matters worse, invasive fouling organisms not only overgrow local sessile species, but they also assist the colonisation of other invaders.

This foreshore at Fairlight shows the contrast between natural shores and boatshed, marina, pontoon and moorings.

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So-called ‘eco-engineering’ measures aim to modify existing marine infrastructure to attract viable communities of native species and to develop new, multipurpose designs that accommodate the needs of humans and wildlife. The foreshore design at Barangaroo Reserve, where local sandstone blocks were used to create a stepped, rocky intertidal shore rich in habitat niches, is an example of multipurpose infrastructure. The stepped boulder field protects the foreshore from wave action and resembles a natural rocky intertidal shore at the same time. Seaweeds have already started to grow between the steps, marking the beginning of what could become a diverse underwater forest. Another more commonly practiced eco-engineering technique has been to add artificial rock pools to infrastructure in order to increase local biodiversity and ecological function. Sydney has a long history of local scientists investigating plant and animal communities on seawalls, and designs of artificial rock pools. ‘Seeding’ artificial structures, which involves transplanting habitat-forming organisms such as native algae, oysters or mussels onto the surface of these structures, can increase local biodiversity and productivity, decrease the chances of colonisation by non-native species by occupying the available space, and improve the water quality at the same time through the absorption or removal of contaminants. So it’s a win, win, win situation! At Balmain and Waverton foreshore, specifically designed tiles using 3D-printing technology were seeded with baby oysters to test if the crevices on the tiles would offer protection from predation of fishes. And, yes, the increased surface complexity of the tiles led to fewer oysters being eaten on those tiles, but only if the number of predatory fishes was high. For any eco-engineering measure to be successful, it is important to set specific, achievable management goals that include measurable ecological outcomes.

The seawall structure at recently developed Barangaroo provides complexity, which is sympathetic to the settlement of native organisms.

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Netted swimming enclosures The protective nets around swimming enclosures in the harbour are densely overgrown with algae, sponges, sea squirts and other fouling invertebrates. Among all that growth live White’s seahorses (Hippocampus whitei), which are only found in several estuaries along the NSW coast and are now listed as endangered. Seahorses rely on their surroundings to hide from predators and so prefer seagrass beds, overgrown artificial structures and sponge gardens for camouflage. They are poor swimmers and tend to live at one location all their lives. In the case of the swimming enclosures, the seahorses like to attach themselves to the protective nets, which at some point become so profusely overgrown that the nets are in danger of collapsing and breaking from their floating support. Councils have to replace or clean the nets every few years. But cleaning the nets means that the seahorses lose their hideouts and have to move on, and it can take over a year for the seahorses to return. Some councils have taken notice and now only clean or replace a section of the netting at a time, leaving some nets overgrown. The timing of cleaning is also important – the nets should be cleaned during the winter months to ensure that mating animals are not disturbed. Artificial structures such as swimming nets are obviously not the seahorses’ natural home, but when their natural habitats, for example seagrass beds, continuously shrink in size or disappear, the nets do provide a refuge for these amazing animals. In Port Stephens ‘seahorse hotels’ – small chicken-wire cages – give the seahorses a place to live where their natural habitat has disappeared.

A White’s seahorse (Hippocampus whitei) on the net at Clifton Gardens, Mosman.

Artificial lighting at night The daily and seasonal rhythm of day and night determines many of our activities and the activities of most plants and animals. So it is not surprising that the invention of artificial lighting has dramatically changed our way of life and by association that of the plants and animals living with and near us. So how are coastal creatures affected by artificial lighting illuminating the busy waterways of Sydney Harbour and coast? Artificial lighting changes the amount of time animals spend on foraging for food, hiding and resting. Although light emitting diodes (LEDs) are more cost and energy effective than traditional lighting, their impact on marine creatures is actually greater. LEDs emit a broader spectrum, so-called white light, which peaks in the blue and green wavelengths that penetrate deeper into the water column. Scientists tested the effects of artificial lighting on fish behaviour under a wharf in Sydney Harbour. It turns out that fishes indeed behave differently when their environment is artificially lit at night. Day-active predatory fishes such as yellowfin bream (Acanthopagrus australis) and leatherjackets (Monocanthidae spp.) tend to seek shelter and rest at night near artificial structures. But when these structures are lit up these animals start feeding at pre-dawn twilight as if it were broad daylight already. This seemingly small change in behaviour appears to be enough to reduce the number of prey organisms surrounding lit wharfs. Interestingly, yellowfin bream and leatherjackets don’t seem to be ‘attracted’ by the artificial light. Squid, on the other hand, actively seek out the light, as do some of the smaller fishes such as yellowtail scad (Trachurus novaezelandiae), which aggregate around lit artificial structures around the early morning hours, probably to catch zooplankton. There is no easy answer as to how artificial lighting affects fish communities and their prey in well-lit harbours and along developed coasts. But we do know that it alters behaviours, resulting in changes within the community. To lessen the impact of artificial lighting, the use of red light, which penetrates water far less, has, for example, been proposed.

Artificial lighting floods Circular Quay every night of the year.

What lives on pilings? Pier pilings at wharfs and jetties have their own little ecosystems. Kelps, oysters, mussels and tube worms wrap around the pylons up high. Deeper down, rich and often colourful communities of other sessile plants and animals thrive, among them many sponges, sea squirts and moss animals often introduced from different parts of the world. These pylon communities attract a variety of fishes, which gather around the overgrown pylons. The cosmopolitan sea squirt Botrylloides leachi, for example, is common on Sydney’s wharf pylons and other artificial structures. Colonies can be bright orange, yellow and white, or dark in colour, which made it difficult for scientists to describe and name this species. Many individuals called ‘zooids’ live together in one colony and each individual has its own water inlet, visible as a small opening, but several individuals share one water outlet, which is visible as a larger opening. Some of the zooids produce eggs and sperm, which are released into the water where they develop into swimming larvae that look like tadpoles with tails. These larvae identify sea squirts as chordates, highly developed animals that have a primitive backbone and spinal cord, similar to us and other vertebrates. When the larvae settle and transform into adult sea squirts, they lose their spine, nerve tube and tail, leaving no trace of the animal’s fascinating ancestry. Botrylloides leachi is so successful because it can handle rough and changing environmental conditions. When times get particularly tough, for example when water temperatures get abnormally high, the colony can go into a form of ‘hibernation’. But the colony doesn’t just fall asleep; it also reduces itself to a small remnant of tissue, just enough to stay alive without feeding, and only regenerates to a fully functional colony when conditions are right again.

A red rock crab (Guinusia chabrus, left) on a pylon under the jetty at Clifton Gardens. The pylon is coated in other invertebrates, including bryozoans, sponges and orange Leache’s ascidians. This close-up of a Leache’s ascidian (Botrylloides leachi, right) shows the small individual inlet syphons and the large communal outlet syphons.

Seawalls

A sea wall at Shiprock, Port Hacking (left). The original rocky shore is visible at low tide; the difference in angle and complexity is evident. An artificial rock pool inset into a seawall at Lavender Bay, Sydney Harbour (right).

Seawalls, even when they are built from a local building material such as sandstone, are less biologically diverse than the surrounding rocky reefs. Many of the plants and animals that live attached on rocky reefs also live on seawalls, but mobile animals such as snails, sea stars and urchins are not commonly found on seawalls. But why? It is the rough and rugged nature of rocky shores that makes them so attractive to wildlife. Seawalls, on the other hand, are smooth and even in comparison without the dips, pools, cracks and crevices that offer protection on rocky shores. A seawall’s vertical surface also offers less space to settle on, and walls heat up more in summer than the surrounding reefs. Wide, shallow holes drilled into vertical seawalls are a simple way to provide shelter for snails and other small invertebrates, but the holes don’t retain water during low tide and over time they fill with animals growing attached to the surface. In an attempt to make seawalls more liveable for native wildlife, Sydney-based scientists have designed and trialled a range of artificial rock pools. At Glebe foreshore and Cremorne Point, existing seawalls have been retrofitted with concrete flowerpots to mimic natural pools. These artificial pools are colonised by algae and soft-bodied animals such as sponges and sea squirts, which then attract crabs, sea stars and snails. A new seawall at McMahon’s Point has been built with custom-designed cavities at various heights. This intervention is easy, requires no additional material and increased the number of plants and animals living on the new wall by around 50% despite the fact that the cavities are permanently shaded, which is not ideal. The upshot is that there is no one-size-fits-all solution. However, previous experiments have shown that artificial structures can be built or retrofitted to accommodate native wildlife, but a detailed knowledge of the local ecological communities is essential to achieve a successful design.

Lurking in the shadows Another harbour resident, generally known from the deep sea, sits perfectly still on the shaded, gloomy seafloor below wharfs, occasionally waving a lure attached to the front of the head. The striped anglerfish (Antennarius striatus) is a master of disguise and extremely difficult to spot. It mostly crawls on its feet-like pectoral fins, but when some unsuspecting prey is close it can strike within a few milliseconds. One snap with its big mouth and the prey is gone.

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A living camouflage suit It can be fascinating to take a closer look at pier pylons. If you’re lucky, you can spot a decorator crab (Hyastenus elatus), so-called because it selectively sticks sponges, algae, anemones and other animals onto its shell in order to perfectly blend in with its surroundings. Decorator crabs found at different locations will have decorated themselves with the residents of that particular environment. Firmly attached on the crab’s shell, the new housemates are moved to new feeding grounds every day and the crab is concealed in return. When the crab sheds its shell so it can grow, it simply picks up new housemates and attaches them to the new shell. Hooked hairs on the shell act almost like Velcro in keeping the companions in place.

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Great collectors Clifton Gardens has its own resident gloomy octopus (Octopus tetricus), which lives in a den in the sandy seafloor next to the wharf. These octopuses stay loyal to their homes, but are not great at house-keeping. Empty shells discarded from prey brought back to the den are piled up at the entrance together with collected junk. Sometimes the octopus hides in other places, too, such as this glass jar – not that clever considering the glass is transparent!

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Globetrotters

See novel habitats for yourself

The cosmopolitan moss animals Watersipora subtorquata and Bugula neritina look very much like coralline algae, but they are colonial animals and consist of thousands of tiny individuals that each live inside a housing. Firmly attached together, these housings form the stiff moss animal body. Both species produce larvae that happily settle on artificial structures and the colonies themselves can handle greater concentrations of heavy metals such as copper. This explains why these species have managed to spread around the globe.

Ku-ring-gai Chase NP

Manly Wharf

Blues Point

Balmoral

Barangaroo

Chowder Bay

Glebe

Botany Bay

Modified sea walls: Glebe, Blues Point, Barangaroo Wharfs and shark nets: Balmoral, Manly Wharf, Chowder Bay

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Northern headland of Bondi Beach

Ocean travellers and visitors

The Sydney coast and estuary don’t exist in isolation, of course, and many of the local plants and animals are connected to populations outside the region. Some species visit our coast sporadically, while others return every year to find a mate. The East Australian Current or EAC, which runs off the Australian east coast and transports warm, tropical water southwards and towards New Zealand, is particularly important. Over the last 60 years the EAC has strengthened, meaning more warm, tropical water is now reaching the Sydney coast and further south. This has implications for the underwater communities that call Sydney their home. Remember Finding Nemo, where Nemo’s dad Marlin is riding the EAC all the way to Sydney together with Crush, the turtle and his tribe? Tropical species are, in fact, hitching a ride in the EAC. Juvenile reef fishes, labelled ‘tropical vagrants’, have been among the first tropical species to arrive along the Sydney coast and harbour. Staghorn corals seem to be making their way south, too, and divers have spotted Pocillopora corals at North Head, just outside the harbour. Higher water temperatures might be advantageous for tropical visitors, but the warmer, nutrient-poor water doesn’t suit our temperate seaweeds, which become stressed when the water gets too warm. In addition, some of the tropical vagrant fishes arriving in Sydney are herbivores. In the tropics these fishes are an important component of healthy reefs by keeping algae in check, which benefits slow-growing corals. But in places like Sydney, plant-eating fishes can cause considerable damage by overgrazing kelp forests.

The bluespine unicornfish (Naso unicornis) is a tropical herbivore that is arriving in increasing numbers in summer in Sydney. This juvenile doesn’t have the characteristic horn developed yet.

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Butterflyfishes, damselfishes, sergeant fishes – all of these can be found in Sydney during the summer months. Scientists observed almost 50 different tropical fish species along the New South Wales coast throughout a 3-year study period. Most of these tropical vagrants arrive as juveniles in Sydney, and are eaten during winter when the water gets colder and they slow down. The temperature threshold for many of these warm-water fishes seems to be around 17°C. Butterflyfishes need slightly higher temperatures with a minimum of 19°C to survive. Although most vagrants are not able to survive winters at the moment, some individuals are making it through and it is only a matter of time until these animals reproduce. Looking at current trends we will most likely see thriving populations of tropical fishes in Sydney in the near future. What happens when tropical, herbivorous fishes take up residence in kelp forests? The Solitary Islands at northern New South Wales might give us a glimpse into the future. Within a period of 10 years kelp forests disappeared from several offshore sites. Underwater videos documented how tropical fishes, in particular black rabbitfish (Siganus fuscescens) and grey drummers (Kyphosus bigibbus), consumed entire kelps. Once the kelps had gone, small turfing algae, which were continuously grazed by other herbivores such as Australian sawtails (Prionurus microlepidotus), took their place. By keeping the smaller algae in a cropped state, these fishes are thought to prevent the recovery of kelps and other canopy algae. Ultimately, the presence of these colourful, tropical fishes along Sydney’s coast might come at a cost – the loss of kelp forests and the establishment of completely different communities.

A juvenile tropical threadfin butterflyfish swims with hulafish at Shiprock in Port Hacking.

An adult Bengal sergeant (Abudefduf bengalensis) near Fairlight in Sydney Harbour.

The EAC doesn’t only transport plankton organisms including tiny coral and fish larvae southward; migrating species such as humpback whales (Megaptera novaeangliae) also take advantage of the EAC’s southward flow. After being hunted almost to extinction along Australia’s east coast up to the 1950s, the collapse of the fishery and legal protection brought these animals back. Since then humpbacks have steadily increased in numbers by around 10% annually. Today Australia’s east coast population contains more than 30 000 animals. Twice yearly, humpbacks pass Sydney on their migration between Antarctic feeding grounds and the tropical breeding grounds off the Queensland coast. Travelling north in the winter months, the whales avoid the EAC and stay close to the shore. Returning south in spring, the whales with their new-born calves utilise the EAC’s strong flow to ease the almost 10 000 km journey. These are the best times to go whale watching in Sydney. Recently local scientists collected whale ‘snot’, the spray emerging from a whale’s blowhole when it breathes at the surface, using a custom-designed drone off the Sydney coast. The drones are remotely operated and fitted with a special holder for Petri dishes, flat plastic dishes with a lid, which are used to grow microbes in the laboratory. Imagine operating a drone from a boat around 200 m away from the whale using the drone camera to time the collection of ‘snot’ when the whale is surfacing and breathing out! Since no-one has collected the snot of whales belonging to the east coast population before, the lung bacteria and viruses collected in this study form a baseline for future studies to assist in monitoring the health of individuals in this population, but also to compare the results to health information from other whale populations around the world.

An exuberant humpback whale (Megaptera novaeangliae) breaches off Sydney. Photo credit: Vanessa Pirotta.

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Visiting sharks Sydney’s coast and harbour are also visited by a variety of sharks throughout the year. Port Jackson sharks (Heterodontus portusjacksoni) or ‘PJs’ are named after our very own harbour. In winter and spring these sharks gather in the coastal areas of Sydney to find a mate and form breeding aggregations. During the other months of the year PJs travel to foraging sites in southern New South Wales and Victoria. Port Jackson sharks have an excellent site memory, meaning they return to the same rocky reef in Sydney they visited in previous years. Female PJs lay eggs in spiral casings and individuals can often be seen with one of these casings in their mouth. This can be bad or good – bad because males are known to eat the eggs of their own species and good because females move their eggs to protective crevices using their mouth. Cabbage Tree Bay Aquatic Reserve in Manly is famous for juvenile dusky whalers (Carcharhinus obscurus), which visit the reserve in summer and early autumn. We don’t know the exact movements of dusky whalers along the Australian east coast, but we do know from South Australian populations that larger juveniles can migrate long distances and that this species is very slow to reproduce.

A Port Jackson shark (Heterodontus portusjacksoni) rests on the bottom at Shelly Beach, Cabbage Tree Bay Aquatic Reserve.

A young dusky whaler (Carcharhinus obscurus) cruises around Fairy Bower, near Manly Beach.

Bull sharks are considered to be one of the more dangerous sharks that visit Sydney. These sharks prefer warm waters and are most abundant in the coastal and estuarine waters of Sydney during the summer and autumn months when water temperatures are around 22°C. We know that bull sharks migrate from coral reef areas in Queensland south to Sydney. The sharks might follow prey such as yellowtail kingfish (Seriola lalandi), Australian bonito (Sarda australis), frigate mackerel (Auxis thazard) and mackerel tuna (Euthynnus affinis), which are more numerous in the harbour during the summer months. Alternatively, some bull sharks might travel to Sydney to mate. But we just know too little about their mating behaviour and breeding habits to confirm this. However, we do know that water temperature is a key predictor of their presence. Magic Point in the southern Sydney suburb of Maroubra used to be the main location in Sydney where divers could see critically endangered grey nurse sharks (Carcharhinus taurus). Small numbers of juveniles and young adults aggregate at the site on their migration between the Solitary Islands in the north and Montague Island in the south. More recently divers have been spotting the occasional grey nurse shark in North Bondi, South Head and Long Reef. What is interesting is that the movement patterns of this shark depend on its sex and whether the animal is sexually mature. Immature sharks roam less far than mature sharks; male sharks have a different migration route than female sharks and the migration route of pregnant females differs from that of non-pregnant females. We still know very little about the biology and ecology of many sharks, but we need information such as mating behaviour, reproductive biology and migration habits to successfully protect these magnificent creatures.

A critically endangered grey nurse shark (Carcharhinus taurus) drifts near the cave at Magic Point, Maroubra.

Red tides The Pacific Ocean and the East Australian Current not only bring the charismatic animals to Sydney’s coast. A large number of microscopic organisms, often singlecelled, are brought here floating in ocean currents. These largely invisible organisms form the basis of the food web and are therefore vitally important. Every few years, when the conditions are right, one particular single-celled organism called Noctiluca scintillans explodes in numbers and taints Sydney’s beaches blood-red. Admittedly, the sight of bright red water on a beach is eerie. These so-called ‘red tides’ are caused by pigments that Noctiluca obtains from its food and stores in the body. Surprisingly, Noctiluca is a predator! It captures other planktonic organisms with one long tentacle that it sweeps through the water. Sometimes a clump or thread of sticky slime sits at the tip of the tentacle, helping in trapping prey. The tentacle then moves the prey to a mouth-like groove, where it is wrapped into parcels, which are then internalised and digested. At night the spooky red ocean turns into a magnificent, sparkling blue with every movement and wave that breaks on the beach. These brief flashes of blue, less than a second long, are caused by a chemical reaction inside the Noctiluca cells, when they are moved about in the water. Luckily, Noctiluca blooms are not dangerous and they are largely a natural phenomenon. Nonetheless, swimming in a red tide is not a good idea. Noctiluca cells produce and release a lot of ammonia, which can irritate the skin and eyes.

A Noctiluca scintillans cell. These organisms are on average about half a millimetre in size, but can be quite large, up to 2 mm, for a single cell. Photo credit: Penelope Ajani.

A red tide occurred along the Sydney coast including Clovelly Beach a few years ago. Photo credit: Gurjeet Singh Kohli.

Shark nets on ocean beaches

Shark nets are at four locations in this picture: Bronte and Bondi at right, and Coogee and Maroubra at left.

From 1 September to 30 April bottom-anchored gill-nets are set at around 50 ocean beaches along the New South Wales coast including the most popular Sydney beaches, with the aim of removing potentially dangerous sharks from swimming beaches. The nets are 150 m long and 6 m high with a mesh size of more than half a metre. The nets are installed several metres below the surface about half a kilometre from the beach. Many different shark species are caught in these nets, some of them dangerous such as bull (Carcharhinus leucas), tiger (Galeocerdo cuvier) and great white sharks (Carcharodon carcharias). The vast majority of animals caught in these nets, however, are non-target species, including other shark species that have never or rarely been implicated in shark attacks, rays, and sometimes even turtles, dolphins and whales. Independent of the species, if the animal is still alive when the nets are retrieved, it is released. The number of non-target casualties has declined due to several measures that have been introduced over recent years. Nets are now set on the seafloor to avoid contact with birds and turtles, and they are removed during whale migration season. The effectiveness of acoustic devices, which send out an alarm signal to discourage any interaction of whales and dolphins with the nets, is debatable. One study in Queensland found that humpback whales responded to the alarm while a study off the Sydney coast did not find a change in whale behaviour when the alarm went off. The question remains – considering we have no evidence that these nets protect humans, does the protection the New South Wales Shark Meshing Program may provide outweigh the number of animals being caught, entangled and often dying in these nets? Aren’t there better alternatives available now such as surveillance programs using drones, which would offer the same or even better protection without causing the death of marine wildlife?

Painful flotsam Going to the beach after a storm or onshore winds, chances are you’ll come across some blue bottles (Physalia utriculus) – small, pale-blue balloons that often have a long, crinkly, dark-blue tentacle attached to them – lying stranded on the beach. Blue bottles belong to the same group as jellyfish, anemones and corals and like many members of this group they have stinging cells, which discharge their venom when touched. To avoid a nasty sting – don’t touch them! Interestingly, these creatures represent a colony of different members called persons, which take on specific functions including feeding, stinging, reproducing and floating in the case of the persons that make up the gas-filled bladder. Blue bottles spend their lives floating out at sea as either left- or right-handed forms and, depending on the direction of the breeze, only the colonies with their crest facing the ‘right’ direction will sail towards the beach and ultimately die. This seems nature’s quirky way to ensure that some blue bottles survive.

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Photo credit: Vanessa Pirotta.

Sun-bathing at the Opera House Since 2014 a male New Zealand fur seal (Arctocephalus forsteri), also known as the long-nosed fur seal, has been enjoying the winter sun on the steps of the Sydney Opera House. New Zealand fur seals are at home on Australia’s south coast, New Zealand and several sub-Antarctic islands and they can travel up to 100 km per day in search for food. Interestingly, we see their relatives, Australian fur seals (Arctocephalus pusillus), less often in Sydney, perhaps because these seals are somewhat less widespread and only live along the mainland’s south coast and Tasmania. The male New Zealand fur seal hanging out in Sydney Harbour obviously doesn’t seem to be bothered by crowds of people and a busy harbour!

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Another tropical visitor Hawksbill turtles (Eretmochelys imbricata) live in the tropics, but divers sometimes spot one of these turtles in the harbour and along Sydney’s coast. They are smaller than other marine turtles and grow between half a metre to 1 m in size. As their common name suggests, their mouth is shaped like a bird’s beak, with which the animals pluck sponges, anemones and algae off reefs. Their shell is covered with strikingly patterned, overlapping bony plates and each flipper has a pair of claws. Hawksbill turtles are listed as ‘Vulnerable’ in Australia. If you have ever watched marine turtles lay their eggs on a beach, you can appreciate the effort it takes for these ancient-looking animals to crawl on land, dig a massive hole and bury their eggs. Like other marine turtles, hawksbill turtles have an incredible memory and females will journey between feeding and breeding grounds often hundreds or even thousands of kilometres. So a stint to Sydney from the Great Barrier Reef isn’t too long a journey for a hawksbill turtle!

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Moon jellyfish

See ocean travellers for yourself Ku-ring-gai Chase NP

Cabbage Tree Bay North Head South Head Sydney CBD

Botany Bay

Cape Solander

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During the summer months, when you peek below a wharf, you can sometimes see great numbers of jellyfish – pulsating, contracting their bell-shaped bodies to propel themselves forward, bumping into each other like rushed pedestrians crossing on a green light. The swimming jellyfish represent only half the story and are, in fact, the short-lived generation of a two-stage life cycle that carries the reproductive organs. The jellyfish, also called medusae, produce eggs and sperm, which after fertilisation in the water develop into larvae. After several days the larvae settle on the sea floor and transform into tiny polyps 1–2 mm in size, strongly resembling coral polyps or miniature anemones. These polyps represent the second generation and they can live for several years. Eventually in spring the polyps segment their bodies into a series of flat discs, which ultimately free themselves from the polyp to become free-swimming, juvenile jellyfish and so complete the cycle. Isn’t it amazing what an incredible transformation these deceptively simplelooking creatures go through!

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Sydney Harbour Bridge

The future of Sydney Harbour

Sydney Harbour and the adjacent coast are strikingly beautiful and amazingly diverse. Their natural splendour not only complements the architectural beauty of the iconic Opera House and Harbour Bridge; some people would argue that Sydney Harbour is one of the most if not the most beautiful harbour in the world! The estuary has undergone an incredible transformation since European settlement and yet most of the plant and animal communities that initially inhabited the waterway appear to be still present in the harbour today. But some fare better than others. Like other harbour cities worldwide, Sydney faces environmental problems that are mainly linked to urbanisation and global climate change. Pollution affecting water quality and seafloor sediments, invasive species, fishing pressure and an everincreasing volume of marine infrastructure are just four of the challenges our harbour is confronted with today. If we are to overcome these challenges, we have to tackle them on multiple fronts and focus our efforts on reducing existing threats, preventing further impacts and restoring damaged ecosystems that provide so many benefits and services for free. Good governance lies at the heart of a sustainably managed harbour. Unfortunately, most of the time regulators and managers have to trade off between conservation goals and competing social and economic values of different users. Nonetheless, we should acknowledge how government regulations and initiatives have contributed positively to maintaining and improving harbour health in the past. The stakeholders of Sydney’s marine environment are varied – surfers here enjoy the waves at Voodoo near Cronulla Beach.

Swimmers race from Shelly Beach to Manly in Sydney’s north.

Beachgoers enjoying the summer sun at Manly Beach.

Let’s take water quality as an example. A series of regulations led to the construction of off-shore ocean outfalls and basic treatment plants to stop raw sewage from entering the harbour. Similarly, after toxic industry wastes had been released unregulated into the harbour until the 1970s, improved environmental laws, including the Clean Waters Act 1970, led to the closure of Sydney’s most polluting industries. Better waste management practices were established and some of the most polluted sites could be partially remediated. Since these measures have been implemented, water quality in the harbour has much improved and Sydneysiders can enjoy a much cleaner harbour today. However, pollution remains a concern as contaminants continue to make their way into the harbour in stormwater run-off. The challenge here is to not only manage rainfall effectively, but to also strengthen and re-establish the harbour’s natural filtration systems such as wetlands, saltmarshes, mangroves and oyster beds. The regulation of local fisheries has always been controversial. After all, the harbour and its bounty belong to all. However, with an ever-growing Sydney population and people fishing 24/7 throughout the harbour and along the coast, many sought-after fish species such as snapper, trevally, grey morwong and mulloway are now overfished in New South Wales. One of the tools to allow these target species to recover is to establish a network of marine reserves, where line-fishing, spearfishing and the collection of invertebrates are not permitted. No-take marine reserves give marine life a safe place to live and allow the whole community to thrive without interference from fishing.

Fishing is a popular pastime in Sydney and therefore requires good governance to ensure sustainability.

Shiprock is a tiny no-take reserve in greater Sydney.

The Sydney region has several marine reserves, but North Harbour Aquatic Reserve is currently the only reserve inside the harbour and line-fishing is permitted there. In fact, fishing is allowed in most of Sydney’s reserves. For decades many Sydney residents and environmental groups have advocated a Sydney Marine Park, which would include several no-take reserves within the harbour. However, to this day no firm plans exist for a marine park with adequate no-take zones despite the wealth of scientific studies that show the benefits of fully protected marine parks. Science, both academic and citizen science, has a key role to play in maintaining the harbour’s natural environment and healthy functioning. Experts from Sydney’s universities, various state agencies and the Australian Museum have studied our local marine communities and the impacts of urbanisation extensively for many years and their findings continue to guide policy makers and urban planners today. Some of the restoration and management tools developed by these scientists have been featured in this book. South-east Australia is one of the global hot spots for climate change and the ocean is warming faster here than in other parts of the world. Whether it is the interactions between local and tropical fish species that arrive in Sydney from the Great Barrier Reef or the effects of increased water temperatures and a decreasing pH on the physiology of local invertebrates, scientists continue to study the impacts of climate change in order to understand how quickly local species may be able to

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Marine scientist using stereo cameras to record all fishes in an area. Software can then be used to size each fish in the video.

adapt to these changing conditions. There are even efforts to breed populations of Sydney rock oysters for the aquaculture industry that are better adapted to changing conditions. Some parts of Sydney have experienced local flooding and wave damage in the past. As sea levels rise and more severe storms are predicted in coming years, the construction of additional coastal infrastructure including seawalls is likely to be the main response. For more than a decade now, Sydney has been leading the world in implementing innovative designs for ‘green’ seawalls and a recent initiative named ‘Living Seawalls’ is continuing this tradition by retrofitting existing structures with purposely designed tiles that facilitate native marine wildlife. There are many more examples of how scientific discoveries have helped over the years to better manage the harbour’s natural environment. Recently scientists synthesised the wealth of scientific knowledge published on the harbour and while we know a fair amount about the harbour’s ecosystems and how they have been affected by our many activities, there are still many knowledge gaps. To systematically tackle some of these questions, scientists from different disciplines are working together on initiatives such as the Sydney Harbour Research Program and the World Harbour

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Low-lying areas such as Collaroy are at the frontline of erosion and inundation.

Custom-made tiles installed in Sydney Harbour as part of the Living Seawalls project.

The Sydney Institute of Marine Science is located at the shores of Sydney Harbour at Chowder Bay.

Project, which aim to future-proof urban marine and estuarine waterways by sharing knowledge and experiences. Both programs were initiated by the Sydney Institute of Marine Science, a modern research facility located at the harbour foreshore at Chowder Bay, which has also been set up as a partnership to encourage cooperative research in a wide range of marine science topics. Similarly, the New South Wales Government recognised several years ago that the activities run by the many agencies involved in managing the New South Wales Marine Estate, including Sydney Harbour, could be coordinated more effectively. The government established the Marine Estate Management Authority in 2013, which developed a framework to better assess management priorities and recommend responses, among other things. With greater awareness and improved coordination of these existing research and conservation programs, it is hoped that we will be able to maximise the benefits of our conservation efforts. If we would like our iconic harbour to remain this beautiful, natural landmark at the heart of Sydney, we – the residents, business owners, users and visitors – also need to adjust our expectations, be prepared to make changes and strive to minimise the impact of our activities. This vision of a healthy, clean and natural harbour is as

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A volunteer diver records fish species, size and abundance at Clovelly as part of Reef Life Survey.

much in our hands as it is in those of regulators, environmental managers, scientists and other professionals who actively work towards managing the harbour responsibly and sustainably. Getting actively involved in a local restoration project or volunteering as a citizen scientist is a wonderful way to immerse yourself in nature and make a positive contribution. More and more people are volunteering their time and skills to assist scientists in their research. In Sydney, local divers conduct underwater visual census surveys, for example, as part of an international research program called Reef Life Survey. The divers are trained by scientists and follow a strict protocol when recording the fishes and many invertebrate species they encounter along transect lines. The data for a recent analysis of Aquatic Reserves in the Sydney region were collected by scientists together with a group of Reef Life Survey divers. Of course, not every project involves getting wet! Sydney Harbour’s underwater communities have proven to be extraordinarily resilient. With good governance supported by reliable scientific information and targeted actions on our behalf, this unique harbour and waterway will continue to thrive. We, the authors of this book, have a love and deep respect for the underwater communities that call Sydney their home and we hope the stories in this book will add to your appreciation of Sydney’s stunning harbour and coast. Goat Island, just west of the Harbour Bridge. Sydney is fortunate to have many green areas preserved throughout the region, including along the foreshore.

Underwater photography John Turnbull

Taking underwater photographs can be a challenging yet rewarding activity. Marine life is so unusual, and often colourful, that it makes a wonderful, intriguing subject. A lot of interesting marine life will sit still for a photograph, too – particularly invertebrates like sponges, soft corals, and kelp, of course. Fishes can be trickier, but with practice they, too, can make great photo subjects. Underwater photography presents some unique challenges; the photographer is most likely moving in the current, water quality may be poor, but most important of all is lighting. Light changes colour and weakens as it passes through water, so unless you are just taking photos in the shallowest of areas, like rock pools, you’ll have to work with artificial lighting. Modern artificial lights – strobes – are fired by mimicking the flash of the camera, and they can often be set to automatic. The biggest challenge then is positioning. If the strobe is angled incorrectly, you can get a photo filled with particles, or no light on the subject at all. Positioning the strobe is therefore one of the most important tasks in getting a great underwater photo. I’m going to suggest three levels of sophistication in taking underwater photos. Which level you aim for is, of course, up to you – and your budget.

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Simple snapshots without a strobe These can be taken with a point-andshoot camera, either a waterproof model or one in a waterproof housing, with no external lighting. Don’t use the in-camera flash – it will just light up the particles in the water in front of the subject. With this setup you will be able to take good photos on bright sunny days in shallow water only, on full auto.

Simple camera on auto, in a housing, with single strobe With this setup you can take shots down to the depth rating of the housing – often much deeper than you’ll want to go. You’ll need a tray and arm to get the strobe away from the camera – preferably at least 30 cm. Practice angling the strobe at home, so you just clip the front of the subject with the edge of the strobe light. Take care to not light up the area between the subject and the camera. You can set the camera and strobe on auto, and start to experiment with different settings, like setting the aperture to control depth of field. You don’t need to worry too much about shutter speed, as the strobe light will freeze the subject.

Going manual There are no two ways about it – to get the best shots underwater you need to go to manual camera settings. You can get great shots with a quality compact camera – in my view, lighting is much more important than the camera you choose. But the camera must be able to be set to full manual (ISO, aperture and shutter speed) with the strobe set to auto or manual. Use the manual settings of the camera to set the exposure of the background – if you want a dark background, underexpose by two stops or more; for a blue or green

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My rock pool setup – a simple, water-resistant compact camera.

Large camera setup – digital SLR camera in a housing with dome port and twin strobes.

background, depending on water quality, use around one stop underexposure. In general, you want to always underexpose the background to some degree. Use your strobe(s) to then expose the foreground correctly – this can be done with TTL if your camera and strobes support it, or by manually setting the strobe levels. Once you’ve mastered this with a single strobe, you can add a second strobe, which will allow you to take wider subjects. You also need two strobes for close-ups so you can light both sides of the critter you’re photographing. You can add a wideangle lens – either an interchangeable lens if you have mirrorless or SLR, or a wet lens if you have a manual compact camera. A macro lens is also worth buying, to allow you to get a bit closer to those tiny subjects.

Some other tips ●●

It’s generally best to shoot underwater photos in RAW, because they nearly always need correction due to the challenges with light, and RAW gives you more scope to fix the photos on your computer later.

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Get as close to your subject as possible. I rarely zoom my camera lens – I leave it on the widest setting and concentrate on getting close to the subject. This reduces the water between the camera and the subject, and improves the quality of the shot. Set up wider than you do on land. If you normally use a 50 mm lens on land, you need a 30 mm lens underwater to compensate for the narrowing effect of refraction. A wider lens also gives you more light, and with today’s high resolution sensors you can crop a lot on the PC to get down to your subject later. Get low and shoot upwards. Subjects backlit by water can be quite spectacular, as water offers less distraction from the subject compared to silty algae, rock or sand.

My personal camera rig My personal rig, which has served me for over 100 000 photographs including the ones in this book, is a compact camera (Sony RX-100) in a Nauticam housing, two strobes (Sea and Sea YS-01), tray, dual arms per strobe, and Inon wet lenses for wide

My well-worn underwater setup – high-end compact camera with twin strobes and video light.

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and macro. I also add a video light to use for videos and general lighting when I’m poking around in deep water or caves. Most of all, whatever camera you have, try to ‘paint with light’. Photography is first and foremost about lighting, and the process of seeing the lighting, then using it to get the shot you want, can be the most rewarding part.

Underwater photography

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Southern passion star (Ptilometra australis) in around 20 m of water off Shark Point, Clovelly.

Moray eel (Gymnothorax prasinus) peering out from its hole at Shiprock.

A hairy red hermit crab (Dardanus crassimanus) watches me take a photo up close at Clifton Gardens.

A colourful firebrick seastar (Asterodiscides truncatus) at Shark Point, Clovelly.

Underwater Sydney

What can I do? Get out there! The beauty of Sydney Harbour and the surrounding coast is best enjoyed by being outdoors and experiencing the water and its life firsthand. Going for a walk along the foreshore, coast and beaches, exploring rock pools and going for a swim, snorkel or dive are great ways to immerse yourself. But make sure you don’t leave any rubbish behind or disturb the marine life!

Educate and advocate! Learning about your local marine life and sharing your knowledge with others not only allows you to meet likeminded people but also deepens your appreciation of the rich and diverse wildlife out there.

garden and household, the fewer chemicals enter the harbour through stormwater and sewage drains. Cutting down on single use plastics makes a big difference too.

Get involved! Join a local community group, non-governmental organisation or council initiative. You can contribute to a citizen science project, local community stewardship activity or restoration project to make a difference in your backyard.

Petition regulators!

Personal choices count!

Evidence-based environmental regulation will ensure the harbour and surrounding coast are adequately protected, so they can thrive. Make sure your concerns are heard by your local government and councils!

Remember that your actions and choices make a difference. For example, the fewer chemicals you use in your

The Aquatic Reserve at Shelly Beach has strong local stewardship, with an active Friends of Cabbage Tree Bay group

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Index abalone  32, 34 advocacy 141 algae brown  32, 110, 112 Caulerpa filiformis 9–10 Caulerpa taxifolia 9 coralline 21 crayweed 32 Ecklonia radiata 32 epibionts  34, 66 Hormosira banksia  16 kelps see algae, brown Neptune’s necklace  16 Phyllospora comosa  32 red  21, 30 sea lettuce  16, 70 seaweeds see algae, brown symbiotic  8, 40 turfing see algae, red Ulva australis  16 wrack 62 Anadara trapezia 85 anemones Actinia tenebrosa 16 Oulactis muscosa 16 shell grit  16 waratah 16 animal colonies  22, 48, 58, 59, 71, 102, 107, 120 antifouling paints  96 aquarium trade  9, 54 artificial habitats see novel habitats artificial lighting  101 ascidians see sea squirts Australian Museum  2, 129 Balanus amphitrite 26 Balmoral 107 Barangaroo Reserve  98, 107 Bare Island  8, 43, 44, 59 barnacles 26 beach cleaning  68 beach hoppers  62 beaches  62, 68, 71, 120 biodiversity  2, 4 bioturbation 85

birds  80, 82, 89 black-winged stilts  89 Epthianura albifrons 82 Eudyptula minor 71 Himantopus himantopus 89 little penguins  71 Neophema chrysogaster 82 orange-bellied parrot  82 oystercatcher 25 white-fronted chat  82 black-lip abalone  34 blue bottles  120 blue-ringed octopus  16, 24 Blues Point see Lavender Bay boating  69, 94, 96 Bondi  27, 108–9, 117 brittle stars  14, 21, 54, 58 bryozoan see moss animal burrows  85, 91 bush foods  84 Cabbage Tree Bay Aquatic Reserve  28–9, 37, 39, 43, 116, 123 calcite 21 calcium carbonate  21, 22, 57 cameras, underwater  136–8 Cape Solander  123 chemicals  11, 22, 23, 48, 50, 52, 70, 86, 96 Chinamans Beach  68 chiton  14, 25 Chowder Bay see Clifton Gardens Circular Quay  101 citizen science  134 Clifton Gardens  5, 27, 94, 100, 102, 106, 107, 132 Clifton Head  5 climate change  129–30 cloning 64 Clovelly  23, 30, 35, 43, 48, 50, 54, 59, 118, 140 cnidarians  8, 16, 57, 59, 120, 123 coastal development see urban development colonial animals see animal colonies contamination see pollution corals Culicia sp.  8

Dendronephthya australis  57 green 8 hard  8, 110 orange 8 Plesiastrea versipora 8 Pocillopora sp.  110 soft  46, 48, 57, 59 courtship  36, 38, 73 crabs Dardanus crassimanus 140 decorator 105 ghost 68 Guinusia chabrus 102 hairy red hermit  140 Heloecius cordiformis  88, 91 Hyastenus elatus  105 Ocypode cordimana  68 red rock  102 semaphore  88, 91 Cronulla 32 crustaceans  6, 26, 43, 64 cunjevoi  20, 23 cuttlefish  6, 7, 73 mourning 73 reaper see cuttlefish, red red 6–7 Sepia mestus 6–7 Sepia plangon 73 debris  37, 87 detritivores  80, 88, 91 development see reproduction drones  114, 119 drowned river valley  2–4 Duck River  3 EAC see East Australian Current East Australian Current  3, 110, 114 eastern rock lobsters  43 echinoderms  6, 27, 34–5, 140 eco-engineering 98 ecosystem engineers cunjevoi 20 oyster and mussel reefs  18 urchins 34–5 education 141

endangered species and communities  69, 71, 82, 100, 117 Enoplosus armatus 41 Fairlight  8, 96, 112 Fairy Bower  10, 36, 39, 53, 74, 116 feather star Ptilometra australis 140 southern passion star  140 feeding  23, 36, 39, 52, 54, 62, 68, 75, 89, 91, 101, 102, 104, 112, 118, 122 filter-feeding  18, 20, 22, 26, 42, 46, 57 fishes  4–6, 34, 37, 66, 75, 80, 100, 110–12 Abudefduf bengalensis 112 Acanthopagrus australis 80 Achoerodus viridis  36 Antennarius striatus  104 Australian bonito  117 Australian sawtails  112 Auxis thazard  117 Bengal sergeant  112 black rabbitfish  112 blue gropers  36 bluespine unicornfish  110 butterflyfishes 112 Cleidopus gloriamaris 56 crimson banded wrasse  36 Cristiceps aurantiacus 6 Dactyloptena orientalis 72 damselfishes 112 eastern blue devils  54 Euthynnus affinis 117 Filicampus tigris 75 flathead 80 frigate mackerel  117 Girella tricuspidata 80 golden weedfish  6 grey drummers  112 grey morwong  39 Gymnothorax prasinus 140 Hippocampus whitei  100 hulafish 112 Idiotropiscis lumnitzeri 6 Kyphosus bigibbus 112 leatherjackets  66, 101 luderick  37, 80 mackerel tuna  117 Maori wrasse  36 Meuschenia freycineti 66 Meuschenia trachylepis 66 moray eel  140 Morwong fuscus 39 Naso unicornis 110 Nemadactylus douglasii 39 Paraplesiops bleekeri 54 Phyllopteryx taeniolatus  6, 38 pineapple 56

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pipefishes 75 Platycephalus fuscus 80 Prionurus microlepidotus  112 Pseudocaranx georgianus 66 purple flying gurnard  72 red morwong  39 red scorpionfish  48 reef 110–13 Rhabdosargus sarba 66 Sarda australis  117 Scorpaenopsis insperatus  5 senator wrasse  36 sergeant 112 Seriola lalandi  117 Siganus fuscescens  112 Sillago ciliata 80 smooth toadfish  86 striped anglerfish  104 Sydney pygmy pipehorse  6 Sydney scorpionfish  5 tarwhine 66 Tetractenos glaber  86 tiger pipefish  75 Trachurus novaezelandiae 101 trevally 66 weedy seadragons  6, 38 White’s seahorses  100 whiting 80 wrasses  25, 36 yellowfin bream  80, 101 yellowtail kingfish  117 yellowtail scad  101 fishing commercial  39, 53, 119 recreational  20, 36, 37, 128–9 food webs  30, 66, 82, 86, 88, 118 foraging see feeding foreshore development see urban development fragmentation  8, 37, 69, 94 geology 2–3 gill-net 119 glacial periods see ice ages Glebe  103, 107 gloomy octopus  106 grasses 82 grazing  14, 23, 110, 112 Haliotis rubra  34 Hapalochaena sp.  16, 24 herbivores  14, 30, 34, 66, 110, 112 Homebush Bay see Sydney Olympic Park human-made habitats see novel habitats hydroids  46, 48 ice ages  2–3 interglacial periods see ice ages

intertidal zone see rocky shores, intertidal introduced species see non-native species invasive species see non-native species invertebrate communities  6–7, 21, 34, 46–51, 55, 62, 66, 85, 100, 102, 103 jellyfish 123 jetties  94, 102 Kurnell  7, 38, 46, 59 La Perouse  39, 55 Lane Cove River  3 larvae  43, 48, 52, 55, 102, 107, 123 Lavender Bay  103, 107 LEDs 101 life cycle see reproduction light organ  56 limpets  14, 23, 80 Little Bay  43 lobsters  32, 43 Long Reef  27, 117 mammals  90, 114, 121 Arctocephalus forsteri  121 Arctocephalus pusillus 121 Australian fur seals  121 bats 82 humpback whales  114 Hydromys chrysogaster  82, 90 Megaptera novaeangliae  114 New Zealand fur seal  121 rakali see mammals, water rat water rat  82, 90 mangroves  76–81, 88, 91 Aegiceras corniculatum 76 Avicennia marina 76 grey 76 river 76 seedling 78 Manly  3, 9, 10, 23, 28–9, 36, 37, 39, 53, 62, 71, 74, 75, 107, 116 maps beaches and seagrass meadows  75 intertidal rocky shores  27 mangroves and saltmarshes  91 novel habitats  107 ocean travellers  123 sponge gardens  59 underwater forests  41 marinas 94 marine infrastructure see novel habitats marine reserves  37, 128–9 Maroubra  27, 117 mating  26, 27, 36, 38, 54, 73, 116–17 microplastics 87 migration  114, 116–17, 122

molluscs  6, 7, 14, 18, 23, 25, 40, 52, 62, 66, 70, 73, 80, 85, 106 monitoring 114 moorings 69 moss animal  52, 58, 107 Bugula neritina  107 Pleurotoichus clathratus 52 Watersipora subtorquata  107 mussels 18 Narrabeen  16, 27, 60–1, 70 New South Wales Shark Meshing Program 119 Noctiluca scintillans  118 non-native species  8–9, 18, 42, 82, 94, 96, 98, 102 North Head  4, 59, 110, 123 no-take zones  37, 128–9 novel habitats  8, 92–6 nudibranchs see sea slugs Oak Park  14, 27 ocean shark nets see shark nets Octopus tetricus  16, 106 old wife  41 open water  108–23 oysters  18, 23, 98, 130 Crassostrea gigas  8, 18 mud 18 Ostrea angasi  18 Pacific  8, 18 Saccostrea glomerata  18, 130 Sydney rock  18, 130 Palm Beach  32 Parramatta River  2–3, 86 Patelloida mimula 80 perennials 82 photography, underwater  135–8 Physalia utriculus 120 pilings  94, 102 plankton  43, 54, 114, 118, 120 plankton bloom  118 plant-eaters see herbivores pneumatophores 78 poisonous  24, 50, 52, 70, 86 pollution  9–11, 39, 69, 86, 87, 96, 128 polychaetes see worms pontoons  94, 96 Port Stephens  57 predators  16, 23, 34, 37, 50, 52, 53, 66, 70, 72, 80, 101, 117, 118 protected species  36, 38, 54, 69, 71, 82, 90, 114 Quarantine Bay  4, 64, 75

red tide  118 Reef Life Survey  134 reproduction  22, 27, 38, 43, 48, 53, 54, 64, 70, 86, 102, 123 restoration  32, 84, 98, 103, 134 rock pools  16, 27, 98, 103 rocky reefs see rocky shores rocky shores  94, 103 intertidal  12–27, 98 subtidal  5, 28–43, 44–59 roots  64, 78 rushes 82 Sagmariasus verreauxi 43 saltmarsh 82–4 austral seablite  84 beaded samphire  82 blackseed samphire  84 creeping brookweed  82 Halosarcia pergranulata 84 Lampranthus tegens 84 little noonflower  84 narrow-leafed wilsonia  84 Samolus repens 82 Sarcocornia quinqueflora  82, 84 Suaeda australis 84 Wilsonia backhousei 84 sanctuary zones see no-take zones sea cucumbers  14 sea fans  59 sea levels  2–3, 130 sea slugs  6, 14, 40, 50, 52, 66, 70 Aplysia juliana 70 blue dragons  40 Ceratosoma brevicaudatum 52 Chromodoris tasmaniensis 7 Dendrodoris denisoni 66 Goniobranchus splendidus 52 Hypselodoris bennetti 52 Jorunna sp.  52 Okenia sp.  52 Pteraeolidia ianthina  40 sea hares  70 Spurilla braziliana 52 sea squirts  20, 55, 102 Botrylloides leachi 102 Cnemidocarpa pedata 55 Pyura praeputialis 20 Pyura spinifera 55 sea tulips  55 seagrasses  64–7, 69, 75, 100 eelgrasses 64 flowers 64 Halophila sp.  64 Heterozostera sp.  64 paddle grasses  64 pollen 64

Posidonia australis  64, 69 southern strapweed  64, 69 Zostera sp.  64 seastars  27, 140 Asterodiscides truncatus 140 cushion star  27 firebrick 140 Parvulaster exigua 27 seawalls  94, 98, 103, 130 seaweeds see algae, brown algae sedges 82 sedimentation  37, 69, 82 sediments  9, 78, 85, 86, 87 seeding 98 sharks  53, 116–17, 119 banded wobbegong  53 bull 117 Carcharhinus leucas  117, 119 Carcharhinus obscurus 116 Carcharhinus taurus 117 Carcharodon carcharias 119 dusky whaler  116 Galeocerdo cuvier  119 great white  119 grey nurse  117 Heterodontus portusjacksoni  116 Orectolobus halei 53 Orectolobus maculatus 53 Port Jackson  116 spotted wobbegong  53 tiger 119 wobbegong 53 shark nets  7, 100, 107, 119 Shark Point see Clovelly shells  14, 16, 18, 26, 36, 105, 106, 122 Shiprock  18, 103, 112, 129, 140 shrimps  16, 34, 66 snails  6, 14, 23, 62, 80, 82, 103 black nerites  14 Cabestana spengleri 23 Cartrut shells  23 Dicathais orbita 23 Littoraria luteola 80 mangrove periwinkle  80 Morula marginalba 23 mud whelks  88 mulberry whelk  23 Pyrazus ebeninus  88 Spengler’s tritons  23 striped periwinkles  14 Velacumantus australis  88 zebra winkles  14 South Head  4, 117, 123 sponge gardens  44–59 sponges  46–52, 55 Halisarca laxa 55 squid 101

Index

157

starfish see seastars stewardship 141 stingarees 74 Trygonoptera imitata 74 Trygonoptera testacea  74 Urolophus kapalensis 74 stinging cells  40, 52, 120 stormwater run-off  10, 11, 22, 69, 87, 128 strobes, underwater  135–7 succulents  82, 84 swimming enclosures  100 Sydney cockle  85 Sydney Harbour Research Program  130–1 Sydney Institute of Marine Science  132 Sydney Olympic Park  78, 82, 84 symbiotic bacteria  56

158

Underwater Sydney

Taronga Zoo  27 tides  3, 14, 57 toxins see chemicals turtles Eretmochelys imbricata  122 hawksbill 122 underwater forests see rocky shores, subtidal urban development  8, 9, 37, 69, 82, 94–9 urbanisation see urban development urchins  34, 36, 39 black 34–5 Centrostephanus rodgersii 34–5 urchin barrens  34 venomous  41, 74

vulnerable species  82, 122 water quality  9, 18, 32, 37, 69, 98, 128 wetland 84 wharfs  94, 102 World Harbour Project  130–1 worms  6, 14, 21, 22, 42, 62, 78, 85, 86 bristle  6, 22, 42 coral 22 fanworm 42 Galeolaria caespitosa 22 Sabella spallanzani 42 Sabellastarte australiensis 42 tube  22, 42