Phytoplankton Dynamics in the North American Great Lakes: Volumes 1 and 2 [1 & 2, 1 ed.] 0992100704, 9780992100704

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Phytoplankton Dynamics in the North American Great Lakes

ECOVISION WORLD MONOGRAPH SERIES

Series Editor M. Munawar

Managing Editor I.F. Munawar

PHYTOPLANKTON DYNAMICS IN THE NORTH AMERICAN GREAT LAKES

Volume 1 1996 Lakes Ontario, Erie, and St. Clair

Photo Credits: Front cover: Georgian Bay (J Lorimer) Ships from left to right: The Martin Karlson (Environment Canada) c.s.s. Bayfield (Fisheries & Oceans Canada and Environment Canada) c.s.s. Limnos (Fisheries & Oceans Canada and Environment Canada) Back cover: Waves (J Lorimer)

ISBN: 978-0-9921007-0-4

© 2014 Ecovision World Monograph Series, Aquatic Ecosystem Health and Management Society, Burlington, Ontario, Canada. Printed by Volumes, Kitchener, Ontario, Canada. Previously published: Volume 1: 1996, SPB Academic Publishing bv, Amsterdam, The Netherlands. Volume 2: 2000, Backhuys Publishers, Leiden, The Netherlands.

All rights reserved. Nothing from this publication may be reproduced, stored, transmitted, or disseminated in any form or by any means without prior written permission ofthe AEHMS.

Citation: Munawar, M., Munawar, I.F., 2014. Phytoplankton Dynamics in the North American Great Lakes: Covering Lakes Ontario, Erie, St. Clair, Huron (Including Georgian Bay and North Channel), Michigan and Superior. Ecovision World Monograph Series, Aquatic Ecosystem Health and Management Society, Burlington, ON, Canada.

Volume 1

Table of contents

Dedication Preface

vii IX

Salutation J.R. Vallentyne

xiii

Foreword c.s. Reynolds

xvii

Chapter 1. Introduction, Techniques, and Procedures Chapter 2. Lake Ontario: Phytoplankton Composition

17

Chapter 3. Lake Ontario: Phytoplankton Parameters and Ecological Implications

105

Chapter 4. Lake Erie: Phytoplankton Composition

133

Chapter 5. Lake Erie: Phytoplankton Parameters and Ecological Implications

199

Chapter 6. Lake St. Clair: Phytoplankton Composition, Parameters and Ecological Implications

221

Taxonomic Index

281

Volume 1

Scientific Advisor

c.s.

Reynolds Institute of Freshwater Ecology Windemere Laboratory Ambleside Cumbria, UK

Scientific Editor M. Legner University of Toronto Erindale College Mississauga, Ontario Canada

Technical Editor H.F. Nicholson

Technical Committee W Finn A. Lacivita J. Lorimer N. Munawar S. Munawar S. Nielsen J. Wotherspoon

Volume 1

Dedication

*** To the fond memory, love, and admiration of' my mother: Khursheed Begum and my father: Abbas Munawar

who devoted their lives for the proper development, nurturing, and training of their family. They always strived hard to encourage and promote frontiers of higher education for their children. In addition they had the untiring and integrated personalities of parent, teacher, and guide. They are no more with us but their memory, legacy, tradition, love, and inspiration lives on ... and will continue to be passed on to the future progeny.

*** To the glory and beauty of Hyderabad - our birthplace. Historically the City of Hyderabad, popularly known as the "garden city" of Deccan, was founded in 1591 by one of the Golconda kings-Muhammed Quli Qutub Shah. Later Hyderabad served as the capital of the former Asaf Jahi Hyderabad State, and now the contemporary capital of the province of Andhra Pradesh, India. Its splendour has been described by many: "The City of Hyderabad lies among the trees on the south bank of the river Musi, the like of which for beauty and cleanliness is not to be found in the whole of Hindustan [India] east, west, south or North." (Abul Qasim Farishta, historian) "There are many fair gardens in this Town, their beauty consists in having long walks kept very clean and lovely fruit trees; but they are satisfi!!d with s~er~i1 cisterns or basins with\vater."(Theovenot, 1665-1666) . .. ~ 1"" ')
3.2

SOlem

Fig. 6 b. Lake Ontario 1970: Seasonal changes of the spatial distribution of Cyanophyta (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 30 CYANOPHYTA 1970

Aug 17

Sep 14

83.2

r - - - - - --\

SOlan Fig. 11 b. Lake Ontario 1970: Seasonal changes of the spatial distribution of Dinophyceae (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 50 DlNOPHYCEAE 1970

Jul 16

Aug 17

Sep 14

B 0 .6

MELOSIRA BINDERANA 10 MAY TO 23 MAY 1972

PORT

MELOSIRA ISLANDICA 18APRIL T03MAY1972

LEGEND 9 m- 3 C J 0-0.1

PORT

YYI::'.LI::',,'"

MELOSIRA ISLANDICA 10 MAY TO 23 MAY 1972

Fig. 20. Lake Ontario 1972, Southwestern Nearshore Region: Spatial biomass distribution of Melosira binderana and M. islandica ssp. helvetica (after Lorefice & Munawar, 1974).

and the higher temperatures generally enhanced the growth of algal cells in the inshore zone. The deep circulation of colder waters offshore, however, could have accentuated the horizontal differences by causing additional light limitation to the offshore phytoplankton. Thus far, conclusions have been mainly based on biological data such as the abundance of certain species of Stephanodiscus and Melosira, indicating nutrient enrichment of the nearshore waters. The thermal bar might have acted as a

Volume 1 72 Table 3. Lake Ontario 1972: Mean biomass of Stephanodiscus spp. (mg m-3 ; after Lorefice & Munawar, 1974).

Distance from shore (km)

Period 0.5

4.0

8.0

Apr 18 to May 3 S. hantzschii v. pusilla Griin. S. tenuis Hust.

58 186

55 97

16 70

May 10 to May 23 S. hantzschii v. pusilla Griin. S. tenuis Hust.

16 143

6 41

32

5

barrier to water movement as indicated by the temperature contours around the Niagara River mouth. There the river water 'pushed out' the 3°, 4°, and 5°C isothenns and yet appeared to have not broken through. This physical evidence of the bar as a 'barrier' is also supported by biological data since the phytoplankton biomass, diatoms, and particularly Melosira binderana showed high concentrations on the nearshore side of the bar. Higher abundance of M. binderana, known to grow in nutrient-enriched environments (Holland, 1968; Stoenner, 1968), suggests that the thennal bar, acting as a 'barrier' may retain the nutrients in the nearshore region (Munawar & Munawar, 1975b). In this investigation, two species of Melosira were encountered: M. binderana, usually associated with eutrophy and M. islandica ssp. helvetica, a species preferring oligotrophic conditions (Rawson, 1956; Lund, 1962; Holland, 1968; see the discussion in Section 4). M. islandica ssp. helvetica was found by Nalewajko (1966) to be more abundant in the central area of the lake, which is regarded as oligotrophic. 3.4. Vertical distribution

Very little is known about the vertical distribution of phytoplankton biomass and its species composition in Lake Ontario. Munawar et at. (1974) described the vertical profiles at an offshore and at a nearshore station during the summer phytoplankton peak of 1972. Maximum biomass was recorded at a depth of 10 m at the midlake station, which was dominated by phytoflagellates, mainly Cryptophyceae (Fig. 21). Similar composition of phytoplankton was found at 5 m at the nearshore station, again fonning the maximum biomass (Fig. 22). The peak biomass of phytoplankton was much higher at the midlake (3.2 g m-3 at 10 m) than at the nearshore station (1.6 g m-3 at 5 m). The available data only allow for the comparison of the upper 10 m of the midlake profile to the nearshore profile. While Cryptophyceae predominated at both stations, a higher biomass of

"

~

00

CRYPTOPHYCEAE

,

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DlNOPHYCEAE

CHRYSOPHYCEAE

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~

~

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./

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,

PRIMARY PRODUCTION (14C ASSIMILATION) mgC m- 3 h- 1

PRODUCTION

,,'PRIMARY

('

//

~

ro

~ TEMPERATURE °c

CHLOROPHYLL a mg m-3

!------"""-"""-> ,,_.........':==:-::;,.---------,...

,

BIOMASS 9 m-3

/BIOMASS

•

~

ro

18

16

12

,.

10

8

6

4

o

e :I:

o

Ii: w

Fig. 21. Lake Ontario July 18, 1972, Midlake Station: Vertical profiles of the proportion of algal taxonomic groups, phytoplankton biomass, 14C assimilation, chlorophyll a and temperature (after Munawar et al., 1974).

Iilllll

~ CHLOROPHYTA

,

,

cYANOPHYTA

mDiATOMEAE

= e

~

~

e

w

o

PERCENT BIOMASS

VERTICAL PROFILE AT A MID· LAKE STATION

LAKE ONTARIO - JULY 18,1972

Vl

-..l

Volume 1

CYANOPHYTA

filill

100 0

CHRYSOPHVCEAE

80

ffi] DINOPHYCEAE

III

60

CRYPTOPHYCEAE

~ CHLOROPHYTA

40

PERCENT BIOMASS

20

.4

"

1.2

,

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,-

PRODUCTION

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PRIMARY PRODUCTION (14C ASSIMILATION) mg C m-3 h-1

5

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200

I

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,

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CHLOROPHYLL! mg m-3

'c

~

I

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20

20

I

20

18

16

14

12

10

8

6

4

0

E

0

~ "w

Fig. 22. Lake Ontario July 27, 1972, Nearshore Station: Vertical profiles of the proportion of algal taxonomic groups, phytoplankton biomass, 14C assimilation, chlorophyll a and temperature (after Munawar et al., 1974).

~ DIATOMEAE

1m

E

o

VERTICAL PROFILE AT A NEARSHORE STATION

LAKE ONTARIO - JULY 27, 1972

-...l

.j::..

Volume 1

Volume 1 75 Chrysophyceae plus Dinophyceae but a lower biomass of Cyanophyta was found at the midlake station as compared to the nearshore station. In the 10 to 20 m layer, the proportion of diatoms greatly increased with depth at the midlake station, whereas the proportion of Cryptophyceae increased between 10m and the water surface along both profiles. A closer look at the species composition of phytoplankton reveals that at the midlake station Rhodomonas minuta and Katablepharis ovalis formed most of the Cryptophyceae biomass (particularly at 10 m), while at the nearshore station Cryptomonas erosa and C. marssonii contributed most to the biomass of that group (Fig. 23). Previously, Findenegg (1971) reported that cryptomonads and particularly C. erosa showed high photosynthetic activity. This might partly explain the pattern of primary production in both vertical profiles as will be discussed later. The presence of Chrysochromulina parva and Oscillatoria limnetica at the nearshore station and of Scenedesmus bijuga var. irregularis at the midlake station are among other differences in the species composition.

4. Taxonomic composition and species succession With the exception of those of Rawson (1956), few data had been available on species composition of the phytoplankton of large lakes before the studies of Munawar & Munawar (1976, 1978, 1979, 1982). The relationship between nutrient levels and the occurrence of some algal species has been established empirically for small lakes of Europe and has been known as the 'indicator' species concept (Thienemann, 1928; Hutchinson, 1967). Although this concept has not been widely applied to large lakes, it helped us assign most species to respective categories, namely eutrophic, mesotrophic, and oligotrophic. A preliminary attempt was made by Munawar & Munawar (1980) to compare phytoplankton composition changes in Lake Erie during 1970 and 1979, keeping in mind 'indicator' affiliation of respective species. Although this kind of approach is complex and sometimes plagued with difficulties, it might be rewarding to test this concept further in the North American Great Lakes, since they provide an excellent gradient of trophic levels. Table 4 lists the occurrence of common species in Lake Ontario during spring, summer, and fall 1970. Note that in spring the plankton was dominated by diatoms. In detail, the species succession in 1970 was as follows: Winter. Flagellates belonging to Cryptophyceae were found in large numbers. They mainly comprised Rhodomonas minuta and Cryptomonas erosa. A few other Cryptophyceae were usually present, but were less common, such as Sennia parvula, Katablepharis ovalis, and Cryptaulax rhomboidea. Among the

Volume 1

76 LAKE ONTARIO JULY 27,1972 NEARSHORE STATION o

160

o

160

BIOMASS mg ril3 0 160 320

0

o

160

160

. :-.e.--._:- .

10 •

JULY 181972 MID-LAKE STATION 400

600

1200

BIOMASS mg m3 1600 0 80

160 0

60

S :I:

Ii:

10'• • • • • • •_

l!l

20

.1l~J>Jr~MONAS

~ CHRYSOCHROMULINA r,::::!CRYPTOMONAS

~Mltr~PHAR'S

~OSCILLATORIA SP.

lI~t~'1.DESMUS

~CRYPTOMONAS

~ PARVA

~MARSONII

~EROSA

Fig. 23. Lake Ontario July 27, 1972, Nearshore Station and July 18, 1972, Midlake Station: Vertical profiles of algal species biomass (after Munawar et ai., 1974).

Volume 1 77 Table 4. Lake Ontario 1970: List of phytoplankton species contributing 2!:5 % to the total biomass (data from Munawar & Munawar, 1982). A =spring; B =summer; C =fall.

Name Cyanophyta Aphanizomenon flos-aquae Ralphs Aphanocapsa sp. Chroococcus dispersus var. minor G.M.Smith Chroococcus minutus (Kiitz.) Naegeli Gomphosphaeria aponina Kiitz. Oscillatoria limnetica Lemm. Chlorophyta Ankistrodesmus falcatus (Corda) Ralfs Ankistrodesmus falcatus var. mirabilis (West & West) Ankistrodesmus falcatus var. spirilliformis G.S.West Asterococcus sp. Carteria cordiformis (Carter) Diesing Chlamydomonas globosa Snow Chi orella sp. Closterium limneticum Lemm. Coelastrum microporum Naegeli Coelastrum proboscideum Bohl. Cosmarium sp. Gloeocystis ampla (Klitz.) Lagerheim Gyromitus cordiformis Skuja Lagerheimia ciliata (Lagerheim) Chodat Mougeotia sp. Oedogonium sp. Oocystis borgei Snow Oocystis sp. Pediastrum simplex (Meyen) Lemm. Pedinomonas minutissima Skuja Phacotus lenticularis (Ehr.) Stein Scenedesmus bijuga (Turp.) Lagerheim Scenedesmus quadricauda (Turp.) de Brebisson Staurastrum paradoxum (Meyen) Staurastrum sp. Tetraedron sp. Ulothrix subtilissima Rabenhorst

B A A

B

C C

A

B

C C

A A

A A

A A

A A

B B B B B B B B B B B B B B B B B B B B

C C C C C C C C C C C C C C C C C C C

B

Euglenophyta Lepocinclis sp. Phacus sp. Chrysophyceae Chromulina sp. Chrysochromulina parva Lackey Dinobryon sociale Ehr. Ochromonas sp.

C B

B B

A A A

B B B

C

Volume 1 78 Table 4. Cont.

Name Diatomeae Asterionella fonnosa Hass. Asterionella gracilllima (Hantzsch) Heib. Cymbella ventricosa Klitz. Fragilaria crotonensis Kitton Melosira binderana Klitz. Melosira varians Ag. Navicula sp. Nitzschia palea (Klitz.) W. Smith Stephanodiscus astraea (Ehr.) Grtin. Stephanodiscus hantzschii var. pusilla Grtin. Stephanodiscus niagarae Ehr. Stephanodiscus tenuis Hust. Surirella ovalis de Brebisson Synedra ulna (Nitzsch) Ehr. Synedra utennohlii Hust. Tabellaria fenestrata (Lyngb.) Klitz. Tabellaria flocculosa (Roth.) Klitz. Tabellaria sp. Cryptophyceae Cryptaulax rhomboidea Skuja Cryptomonas erosa Ehr. Cryptomonas ovata Ehr. Katablepharis ovalis Skuja Rhodomonas minuta Skuja Dinophyceae Ceratium hirundinella (Mueller) Schrank Glenodinium pulvisculus (Ehr.) Stein Glenodinium sp. Gymnodinium helveticum Penard Gymnodinium. sp.

A

A

B

A A A

B

C C

C

A

B B

A

B

C

A

A A A A A A A

C

B

C C

B

C C

B

C

A A A

B

C

A A

B B

C

A A

B A

A A A

B B B

C C

green algae, Scenedesmus bijuga var. irregularis was the most abundant. Asterionella formosa, Diatoma elongatum, and Surirella angustata were typical winter diatoms. Spring. Phytoplankton was mainly composed of Scenedesmus bijuga var. irregularis, Chlorella sp., Coelastrum microporum, Melosira binderana, Melosira varians, Melosira islandica ssp. helvetica, Stephanodiscus tenuis, S. hantzschii var. pusilla, S. niagarae, Asterionella gracillima, and A. formosa. Distinct spring blooms were developed by Melosira binderana, Stephanodiscus tenuis, and S. hantzschii var. pusilla. Summer. Phytoplankton was dominated by Pediastrum simplex, Actinastrum

Volume 1

79 hantzschii, Chlorella sp., Pedinomonas minutissima, Ankistrodesmus Jalcatus var. spirilliformis, Oocystis borgei, Scenedesmus bijuga, and Chrysochromulina parva. Plenty of colourless chrysomonads were found in samples, particularly during June and July. Certain other species, such as Rhodomonas minuta, Cryptomonas erosa, Dinobryon sociale var. americanum, Katablepharis ovalis, and species of Gymnodinium and Glenodinium were observed in small numbers. Fall. The phytoplankton community consisted of Cyanophyta as Chroococcus dispersus var. minor, Oscillatoria limnetica, and Chlorophyta as Chlamydomonas globosa, Pedinomonas minutissima, Chlorella sp., Ankistrodesmus Jalcatus, Oocystis borgei, Coelastrum microporum, and Oedogonium sp. The fall phytoplankton showed very few diatoms. Flagellates belonging to Chrysophyceae and Cryptophyceae appeared frequently in considerable numbers. Chrysochromulina parva, Rhodomonas minuta, Cryptomonas erosa, and Katablepharis ovalis were the main components, C. parva in particular developed dense populations. Colourless chrysomonads were also observed in the fall but less frequently as compared to their summer maximum. Dinophyceae were represented by Gymnodinium helveticum and Glenodinium sp., the latter in low numbers only. Certain species occurred all year round. Such species were Rhodomonas minuta, Cryptomonas erosa, Katablepharis ovalis, Ankistrodesmus Jalcatus var. spirilliformis, Scenedesmus bijuga, Chroococcus dispersus var. minor, and Chroococcus minutus. Considerable variations in the body size and shape were observed in several species throughout the year. Examples are Scenedesmus bijuga, which during the winter assumed an appearance close to Scenedesmus bicellularis, and Stephanodiscus hantzschii var. pusilla, which occurred both as single cells and as threads of different sizes, with or without spines. Melosira binderana, which formed a major part of the diatom biomass, is the most important spring species. The species starts to develop in early spring along the shore and especially in nutrient-rich regions. Its early development seems to be very closely related to the development of the thermal bar. However, its numbers had decreased before the thermal bar broke down, and it could scarcely be found in the zone where the temperature was above 8°C. Chrysochromulina parva is the only Chrysophyceaean of quantitative importance, since it has a summer-through-fall distribution with its maximum in July and obviously prefers water temperatures between 10° and 15°C. Rhodomonas minuta is a species with year-round occurrence and a late summer biomass maximum. The species favours the inshore regions at the beginning of the season, but it is quite evenly distributed all over the lake in summer. This pattern might have resulted from increased nutrient concentrations inshore during the thermal bar conditions and from a lakewide availability of nutrients after the thermal bar has been overcome. The species' preference for high nutrient cQncentrations seems to be confirmed by its occurrence in upwelling

Volume 1 80 regions such as in Burlington Bay in September and October. Comparison of species composition between inshore and offshore areas in 1970 revealed certain characteristic features. In the inshore region, the maximum observed in March was mainly made up of Stephanodiscus tenuis, S. hantzschii var. pusilla, Asterionella formosa, and Melosira varians. Another pulse was recorded during May when the water temperature was relatively high in which a different species composition was found, dominated by Melosira binderana, with Asterionella gracillima, Stephanodiscus tenuis, and Melosira varians as codominants. In the offshore region, the development of diatoms was delayed and the maximum development was not as striking as the inshore region. Only one pulse was noticed in the offshore region and it was relatively reduced in magnitude. Species which were abundant inshore like Melosira binderana, Stephanodiscus tenuis, and S. hantzschii var. pusilla, were found only in small numbers and the offshore communities were dominated by Melosira islandica spp. helvetica. Inshore-offshore differences were observed in other seasons as well. For example, the inshore region showed two peaks of blue-greens during summer and late fall, consisting of Oscillatoria spp. and Chroococcus dispersus var. minor, respectively. On the other hand, the offshore region showed only one summer pulse of blue-greens of similar species composition. During the fall period, maximum diversity of phytoplankton composition was seen in both regions since all the taxonomic groups were represented with a reasonable share in the community structure. After a gap of three months when the diatoms were either absent or in extremely low numbers, they returned again to both regions along with the Cryptophyceae and Dinophyceae flagellates, Chlorophyta, and Cyanophyta. Compared to the inshore region where diatoms developed earlier and in large numbers (September and October), their abundance in the offshore region showed a lag (until November). Table 5 lists the occurrence of common species in Lake Ontario during spring, summer, and fall 1978. Note that although spring was dominated by diatoms as in 1970, there were less dramatic changes in the species composition in 1978. Chlorophyta increased in the fall of both years, whereas Dinophyceae appeared more common in the spring of 1978 than in the spring of 1970.

5. Lakewide studies: comparison of 1970 and 1978 Only two extensive lakewide studies of the Lake Ontario phytoplankton had been accomplished before the recent surveys of six transects across the Lake (see Chapter 4). They were carried out in 1970 (Munawar & Nauwerck, 1971) and 1978 (Munawar et al., 1987), respectively. The data from these two surveys form the basis of the 1970 to 1978 comparison discussed below. Table 6 compares the

Volume 1 81 Table 5. Lake Ontario 1978: List of phytoplankton species contributing A =spring; B =summer; C =fall.

~5

% to the total biomass.

Name Cyanophyta Aphanizomenon flos-aquae Ralphs Chroococcus dispersus var. minor G.M. Smith Oscillatoria limnetica Lemm. Chlorophyta Chlamydomonas globosa Snow Chlamydomonas sp. Coelastrum sphaericum Naegeli Gloeocystis gigas (Kiitz.) Lagerheim Gloeocystis planktonica (West & West) Lemmermann Gloeocystis sp. Oedogonium sp. Oocystis borgei Snow Oocystis crassa Wittrock Oocystis lacustris Oocystis sp. Oocystis submarina Pediastrum duplex Pediastrum simplex (Meyen) Lemm. Scenedesmus bijuga (Turp.) Lagerheim Scenedesmus bijuga var. flexuosa (Lemm.) G.M. Smith Staurastrum paradoxum (Meyen) Staurastrum sp. Chrysophyceae Chrysochromulina parva Lackey Dinobryon sp. Erkenia subaequiciliata Skuja Mallomonas sp. Uroglena sp. Uroglenopsis sp. Diatomeae Asterionella formosa Hass. Cyclotella sp. Diatoma elongatum Ag. Diatoma elongatum var. tenuis Fragilaria crotonensis Kitton Melosira binderana Kiitz. Melosira granulata (Ehr.) Ralfs Melosira sp. Navicula cryptocephala Kiitz. Stephanodiscus astraea var. minutula (Kiitz.) Griin. Stephanodiscus hantzchii Griin.

A A

A A A

B B B

B B B B B B

B

A

B

C C C

C C C C C C C C C C C

B

A A A

A A A

A A A A

B B B B B B

B B B B B B B B B B

C

C

C C

C

Volume 1 82 Table 5. Lake Ontario 1978: List of phytoplankton species contributing A =spring; B =summer; C =fall.

~

% to the total biomass.

Name Stephanodiscus astraea (Ehr.) Grtin. Stephanodiscus hantzschii var. pusilla (Grtin.) Krieger Stephanodiscus niagarae Ehr. Stephanodiscus sp. Tabellaria fenestrata (Lyngb.) Kiitz. Cryptophyceae Crypotmonas brevis Cryptomonas erosa Ehr. Cryptomonas marssonii Cryptomonas ovata Ehr. Cryptomonas reflexa Cryptomonas tetrapyrenoidosa Katablepharis ovalis Skuja Rhodomonas minuta Skuja Rhodomonas minuta var. nannoplanctica Dinophyceae Ceratium hirundinella (Mueller) Schrank Glenodinium sp. Gymnodinium helveticum Penard Gymnodinium sp. Gymnodinium uberrimum Gymnodinium varians Peridinium aciculare Peridinium aciculiferum Peridinium sp.

A A A A A

A

A

B B B

B B B B B B B B B

C

C C

C C

C

A A A A A A

B B B B B B B

C C C C C

total biomass and taxonomic groups representation (in percentage of the biomass) for the spring and summer seasons. With the exception of Cryptophyceae (summer), the differences between the two years were not statistically significant. However, some of the changes were large enough to warrant discussion. Total phytoplankton biomass decreased considerably from 1970 to 1978 during both seasons, especially during summer. The spring population of Chrysophyceae and Dinophyceae increased from 1970 to 1978 while Diatomeae and Cryptophyceae decreased in 1978. The summer populations of phytoplankton, meanwhile, underwent considerable changes in the relative contribution of respective taxonomic groups. The proportion of Cyanophyta and Chlorophyta was substantial in the 1970 summer phytoplankton, but it was reduced by 1978, while Chrysophyceae, Diatomeae, and Cryptophyceae showed

Volume 1 83 Table 6. Lake Ontario 1970 and 1978: Comparison of the biomass of main taxonomic groups (after Munawar et al. , 1987). Spring 1970' Biomass (g m· 3) Percent biomass: Cyanophyta Chlorophyta Chrysophyceae Diatomeae Cryptophyceae Dinophyceae

Summer 1978"

1970

1978

2.0

1.1

5.3

1.2

2.8 5.6 8.0 59.6 16.2 7.7

2.9 6.0 15.5 39.6 9.9 25.5

26.1 34.9 9.8 7.5 15.1 6.1

5.8 14.1 13.5 28.2 29.1 8.7

•

Mean of four cruises, 27 to 30 stations. ,. Mean of three cruises, 22 stations.

an increase. The above changes represent a considerable shift in community structure between 1970 and 1978, emphasized by the fact that Diatomeae only dominated the spring and fall phytoplankton in 1970 while they also became dominant during summer in 1978. The apparent suppression of blue-green and green algae and the prevalence of Diatomeae in summer 1978 is very similar to the community structure observed in the Upper Great Lakes (Lake Huron, Georgian Bay, etc.; Munawar and Munawar, 1986. The seasonal fluctuations of phytoplankton during 1970 which are based on lakewide cruise-means of 27 to 30 stations distributed across the lake are shown in Fig. 24. Only one clearly pronounced biomass peak was observed in the middle of the summer with two relatively small maxima occurring during the spring period. The mean phytoplankton biomass varied between 1 and 9 g m-3 with the only peak in August. At that time, Cyanophyta and Chlorophyta formed a substantial part of the phytoplankton. During the period January through June, diatoms formed most of its biomass. During the entire year of 1970, higher numbers of maxima (four) were observed in the inshore region (Fig. 25b) than in the offshore region which had only a single pulse (Fig. 25a). It was also found that the average biomass of the inshore region was about 25 percent greater than that of the offshore region. Diatoms dominated during the winter-spring period (January to May) in both regions but their abundance in the inshore area was much higher, producing welldeveloped maxima. The above phenomena may be well ascribed to the effect of the thermal bar which allowed for spring diatom maxima inshore by holding the warmer and nutrient-rich water. Consequently, the late summer pulse both offshore and inshore resulted from the lack of horizontal nutrient gradient at that time. Species composition also differed between these regions. However, in the

Volume 1

84 LAKE ONTARIO 1970

'"'e Q

,JAN

, FEB , MAR , APR , MAY , JUN

, JUL , AUG , SEP , OCT , NOlI , DEC ,

0000

~~~~ Cyanophyta

Chlorophyta

~ ~Diatomeae

Cryptophyceae

Chrysophyceae

D

Dinophyceae

Fig, 24, Lake Ontario 1970: Seasonal variations of phytoplankton biomass and of the proportion of taxonomic groups (after Munawar & Nauwerck. 1971).

offshore region, the development of diatoms was restricted and the maximum development was not as striking as the inshore region. Only one pulse was noticed in the offshore area and it was relatively small in size. Further inshore-offshore differences were observed in other seasons as well. For example, the inshore region showed two peaks of blue-greens during summer and late fall. Conversely, the offshore region showed only one summer pulse of blue-greens of similar species composition. During the fall period, maximum diversity of phytoplankton composition was seen in both regions since all the taxonomic groups were well represented in the community structure. After a period of three months, when the diatoms were either absent or in extremely low numbers, this latter group returned to both regions along with the phytoflagellates (Chrysophyceae, Cryptophyceae, and Dinophyceae), Chlorophyta, and Cyanophyta. However, the biomass of diatoms in the offshore region remained low until November as opposed to the inshore region where it developed earlier in large quantity (September and October). The phytoplankton composition began to show more diversity from June onwards when phytoflagellates, green algae, and blue-green algae contributed significantly throughout the summer and

Volume 1 85 LAKE ONTARIO OFFSHORE 1970

0000

bo~o~o~o Cyanophyta

Chlorophyta

::::::: Diatomeae

Cryptophyceae

0000

Chrysophyceae

/\ . .] Dinophyceae

Fig. 25 a. Lake Ontario 1970: Seasonal variations of phytoplankton biomass and of the proportion of taxonomic groups (after Munawar & Munawar, 1982). a. Offshore Region.

fall periods. The biomass ratio between greens and blue-greens was considerably higher in the offshore region. In 1978, the total biomass showed two maxima, one in June and one in September (Fig. 26). Diatoms prevailed in spring as they did in 1970, but in June 1978, phytoflagellates (Chrysophyceae, Cryptophyceae, and Dinophyceae) formed more than 50 percent of all biomass and remained that way until the end of summer. The diatoms showed another peak in September, but otherwise the proportion of individual taxonomic groups did not fluctuate as dramatically during 1978 as it did in 1970. In summary, the lakewide data showed that the total phytoplankton biomass decreased from 1970 to 1978 and this drop was accompanied by changes of proportions among various taxonomic groups. Only further research can show if these changes substantiate areal trend or fall within year-to-year fluctuations of phytoplankton biomass. In order to detail the above changes, three stations

Volume 1 86 LAKE ONTARIO INSHORE 1970

0000

~o~~~o Cyanophyta 0000

··.... .. Diatomeae ·... ...

Chlorophyta

Cryptophyceae

Chrysophyceae

D

Dinophyceae

Fig. 25 h. Lake Ontario 1970: Seasonal variations of phytoplankton biomass and of the proportion of taxonomic groups (after Munawar & Munawarm 1982). h. Inshore Region.

(located in each basin) were chosen in an attempt to make a long-term comparison of phytoplankton biomass and its species structure. Because of the immense size of the lake, however, the possibility of extrapolating the results from individual stations to the whole lake ecosystem is limited.

6. Long-term station comparisons 6.1. Western Station

The phytoplankton biomass and taxonomic composition at the Western Station were described by Munawar et al. (1987) and are given in Fig. 27a for 1970, 1975, and 1979. Statistically, no significant differences were detected either for the total biomass or for the individual groups among the three years. This may be attributed to the lack of replication in microscopic enumeration (see Section 2). On the other hand, visual inspection of Fig. 27a reveals conspicuous differences

Volume 1

87 LAKE ONTARIO 1978 1.6 1.4 1.2

•E '"

..

C/) C/)

1 0.8

:::;;

Q 0.6 co 0.4 0.2 0

C/)

! !zw

ffia.

APR 15 MAY 15 JUN 14 JUL 14 AUG 13 SEP 12 OCT 12

II .........

CYANOPHYTA

···· m ......... .........

DIATOMEAE

~

CHLOROPHYTA

mimi

CRYPTOPHYCEAE

II1II

CHRYSOPHYCEAE

DINOPHYCEAE

Fig. 26. Lake Ontario 1978: Seasonal variations of phytoplankton biomass and of the proportion of taxonomic groups.

in the total biomass, particularly in summer. The summer phytoplankton biomass in 1970 was 7 to 8 g m-3 which was three times higher than in 1975 and 1979 during the same season (0.2 to 1.1 g m-3) . The relative proportion of phytoplankton groups was not radically different between the years, with a few exceptions. For example, Diatomeae contributed less in 1979 (23 %) compared to 1970 (36 %) and 1975 (40 %). Conversely, Chlorophyta contributed only 13 percent in 1970 but 16 percent in 1975 and 25 percent during 1979. During July and November, Chlorophyta formed from 11 to 57 percent of the total biomass. The Cryptophyceae flagellates contributed moderately from 19 to 24 percent during the three years of evaluation. The species composition of the Western Station phytoplankton for three years

Volume 1 88 is given in Table 7. The list is restricted to species contributing 1 percent or more to the total biomass. It is apparent that higher numbers of species were observed during 1979 compared to 1970 and 1975. The phytoplankton consisted of a mixture of eutrophic through oligotrophic species. Spring and summer of 1970 had a predominance of Tabellaria flocculosa but that disappeared during the spring periods of 1975 and 1979. As the decade progressed, this species shifted its pulse from spring to the summer and fall periods. Melosira binderana, which is considered to be an indicator of eutropy, was only observed in 1970. Other species which were only found in 1970 were Phacotus lenticularis and Melosira varians. Species regularly found during the spring of 1975 were Lyngbya limnetica and Oscillatoria limnetica while Cyclotella sp. occurred during the summer and fall of 1975. The following species were observed both in 1975 and 1979: Cyclotella sp., Diatoma elongata, Tabellariaflocculosa, Fragilaria crotonensis, Gymnodinium sp., and G. varians. In 1979, the community showed a large species diversity and comprised both oligotrophic and eutrophic species. The former were Cyclotella glomerata, Gloeocystis sp., G. gigas, G. pianctonica, and Mallomonas sp. while the eutrophic species consisted of Melosira granulata, Diatoma elongatum, Oscillatoria limnetica, Stephanodiscus astrea var. minutula, S. hantzschii var. pusilla, and S. niagarae. This group of species indicates that no clear cut changes could be detected. Instead, the assemblage appears to be a mixture of oligotrophic and eutrophic species, indicating perhaps a transitional stage since low biomass and low phosphorus concentrations were observed, which will be discussed later (Chapter 3). 6.2. Eastern Station

The phytoplankton biomass and its taxonomic composition at the Eastern Station were described by Munawar et al. (1987) and are shown in Fig. 27b. No statistically significant differences were detected for biomass or for various groups. However, the mean biomass concentration was found to be 50 and 26 percent higher in 1970 than in 1975 and 1979 respectively. The percent contribution of Cyanophyta was highest in 1970 (29%). Chlorophyta showed an increasing trend from 21 to 29 percent. Chrysophyceae contribution ranged from 8 to 10 percent over the three years. Diatomeae increased from 10 percent in 1970 to 22 percent in 1975 and slightly declined to 21 percent during 1979. The Cryptophyceae phytoflagellates showed similar contributions during 1970 and 1975 but a relatively lower percentage (13%) in 1979. The contribution of Dinophyceae was only 3 percent in 1970 but 9 percent in 1975 and 17 percent during 1979. The species composition for the Eastern Station is presented in Table 8. Greater numbers of species occurred in 1979 than in 1970 or 1975. Species that were prominent only in 1970 included Chroococcus dispersus var. minor,

Volume 1 89 Table 7. Lake Ontario 1970, 1975, and 1979: List of phytoplankton species contributing ~1 % to the total biomass at the Western Station (data from Munawar et al., 1987). A spring; B summer; C fall.

=

=

1970

1975

1979

ABC

A

AB C

B AB

AB

=

Name Cyanophyta Chroococcus dispersus var. minor G.M. Smith Lyngbya limnetica Lemm. Oscillatoria limnetica Lemm. Chlorophyta Ankistrodesmus fa1catus (Corda) Ralfs Chlamydomonas globosa Snow Chlorella sp. Chlorella vulgaris Beyerinck Coelastrum microporum Naegeli Coelastrum sphaericum Naegeli Cosmarium phaseolus De Brebission Gloeocystis gigas (Klitz.) Lagerheim Gloeocystis planctonica (West & West) Lemm. GIoeocystis sp. Mougeotia sp. Oedogonium sp. Oocystis borgei Snow Oocystis crassa Wittrock Oocystis sp. Oocystis submarina Lagerheim Pedinomonas minutissima Skuja Phacotus Ienticularis (Ehr.) Stein Scenedesmus bijuga (Turp.) Lagerheim Scenedesmus bijuga var. flexuosus (Lemm.) Collins Scenedesmus sp. Chrysophyceae Chromulina sp. Chrysochromulina parva Lackey Chrysomonas sp. Dinobryon sociale Ehr. Mallomonas sp. Ochromonas sp. Euglenophyta Phacus sp. Diatomeae Asterionella formosa Hassal Cyclotella glomerata Bachmann Cyclotella sp. Diatoma elongatum Ag. Fragilaria crotonensis (Edw.) Kitton

A A

B A BC B B B A B B B B C C B B

A A ABC B A

C ABC ABC AB

AB

AB B B

AB A C

AB

B

A

B

B A C

AB B C

B B B C

Volume 1 90 Table 7. Cont. Name Fragilaria sp. Melosira binderana Kiitz. Melosira granulata (Ehr.) Ralfs Melosira sp. Melosira varians Agardh Stephanodiscus hantzschii Griin. Stephanodiscus hantzschii var. pusilla (Griin.) Krieger Stephanodiscus astraea var. minutula (Kiitz.) Grunow Stephanodiscus niagarae Ehr. Stephanodiscus sp. Stephanodiscus tenuis Hust. Synedra acus var. radians (Kiitz.) Hust. Synedra ulna (Nitzsch) Ehr. Tabellaria flocculosa (Roth.) Kiitz. Cryptophyceae Chroomonas sp. Cryptomonas caudata (Massart) Schiller Cryptomonas erosa Ehr. Cryptomonas ovata Ehr. Cryptomonas sp. Katablepharis ovalis Skuja Rhodomonas minuta var. nannoplanctica Skuja Rhodomonas minuta Skuja Dinophyceae Glenodinium pulvisculus (Ehr.) Stein Gymnodinium helveticum Penard Gymnodinium sp. Gymnodinium varians Maskell Peridinium aciculiferum Lemm.

1970

1975

1979

B A A A

C

A AB C B

C A

AB C A C A

A

B A AB

C

C

C A ABC B

BC B BC

AB

A

ABC

C ABC

A C AB B B

AB

B B C AB

C AB C AB AB C

Aphanizomenon flos-aquae, Oocystis borgei, Chrysomonas sp., Melosira varians, and Glenodinium pulvisculus. A similar pattern of conspicuous occurrence only in 1975 was represented by some species which are known to exist in eutrophic environments. These included Oscillatoria limnetica, Stephanodiscus hantzschii var. pusilla, S. niagarae, and Peridinium aciculiferum. Some species such as Tabellariaflocculosa and Chromulina sp. were found in 1970 and 1975 while others occurred only in 1975 and 1979. The majority of these species are regarded as eutrophic and included Aphanizomenon flos-aquae, Oocystis borgei, O. submarina, Stephanodiscus hantzschii, and Diatoma elongatum.

Volume 1 91 Table 8. Lake Ontario 1970, 1975, and 1979: List of phytoplankton species contributing ~1 % to the total biomass at the Eastern Station (data from Munawar et ai. , 1987). A = spring; B = summer; C = fall. Name Cyanophyta Aphanizomenon flos-aquae (L.) Ralfs Chroococcus dispersus var. minor G.M. Smith Chroococcus sp. Merismopedia sp. Oscillatoria limnetica Lemm. Chlorophyta Ankistrodesmus falcatus var. rnirabilis (West & West) Chlamydomonas globosa Snow Chlamydomonas sp. Chlorella sp. Chi orella vulgaris Beyerinck Closterium parvulum Naegeli Coelastrum sphaericum Naegeli Gloeocystis sp. Gyromitus cordiformis Skuja Mougeotia sp. Oedogonium sp. Oocystis borgei Snow Oocystis crassa Wittrock Oocystis sp. Oocystis submarina Lagerheim Pediastrum simplex (Meyen) Lemm. Pedinomonas minutissima Skuja Phacotus lenticularis (Ehr.) Stein Scenedesmus bijuga (Turp.) Lagerheim Scenedesmus quadricauda (Turp.) De Brebission Scenedesmus sp. Staurastrum paradoxum Meyen Tetraedron minimun (A. Braun) Hansgirg Chrysophyceae Chromulina sp. Chrysochromulina parva Lackey Chrysomonas sp. Dinobryon sociale Ehr. Erkenia subaequiciliata Skuja

1970

1975

B ABC

A

C

A

C C C

B

C

B C C

C

C AB C

C C ABC

C C B A

A

AB B C B

B

A

A A

A

A

ABC

AB C A B A

B B ABC B C A

C

A ABC A A

A A B B

AB C

B

Euglenophyta Trachelomonas sp. Diatomeae Asterionella formosa Hassal Cyclotella atomus Hust.

1979

B

A

A

C C

Volume 1 92 Table 8. Cont. Name Diatomeae Cyclotella glomerata Bachmann Cyclotella sp. Diatoma elongatum Ag. Fragilaria crotonensis (Edw.) Kitton Fragilaria sp. Melosira binderana Kiitz. Melosira granulata (Ehr.) Ralfs Melosira varians Ag. Stephanodiscus hantzschii Griin. Stephanodiscus hantzschii var. pusilla (Griin.) Krieger Stephanodiscus astraea var. rninutula (Kiitz.) Grunow Stephanodiscus hantzschii Griin. Stephanodiscus niagarae Ehr. Tabellaria flocculosa (Roth.) Kiitz. Cryptophyceae Cryptaulax rhomboidea Skuja Cryptomonas marssonii Skuja Cryptomonas caudata (Massart) Schiller Cryptomonas erosa Ehr. Cryptomonas ovata Ehr. Cryptomonas sp. Katablepharis ovalis Skuja Rhodomonas rninuta Skuja Rhodomonas rninuta var. nannoplanctica Skuja Rhodomonas sp. Dinophyceae Glenodinium pulvisculus (Ehr.) Stein Glenodinium sp. Gymnodinium helveticum Penard Gymnodinium sp. Gymnodinium uberrimum (Allman) Kofoid & Swezy Gymnodinium varians Maskell Peridinium aciculiferum Lemmermann

1970

1975

1979 A

B A B A A A A A

C

C B AB B C A A A

A C A B

A

B C A A

C A

A

C C ABC

ABC B C

C AB C B

C ABC

B C ABC C

C AB C

A A

C B

B A

B A B

A A AB A

The species reported for 1979 alone reflect a predominantly eutrophic assemblage and only a limited number of oligotrophic species were represented (Cyclotella glomerata, C. atomus, Gymnodinium uberrimum.) The eutrophic species were represented by Oscillatoria limnetica, Oocystis crassa, Tetraedron minimum, Melosira granulata, Stephanodiscus astraea, Gymnodinium helveticum,

Volume 1 93 WESTERN STATION 1~ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _1~9~ro

8

i. n

'e

CD

7

8 5 • 3

MAY

III

Cyanophyta

..IJN

•

JUL

Chlorophyta

AUG

SEP

•

mill Oiat~ II Cr~ D

OCT

NCN

Chrysophyceae Dinophyceae

Fig. 27 a. Lake Ontario 1970, 1975, and 1979: Seasonal variations of phytoplankton biomass and of the proportion of taxonomic groups (after Munawar et aI., 1987). a. Western Station.

Volume 1 94

I I II [ill

Cyanophyta

Oiatomeae

•

II

Chlorophyta

Cryptophyceae

•

D

Chryaophyceae

0in0phyceM

Fig. 27 h. Lake Ontario 1970, 1975, and 1979: Seasonal variations of phytoplankton biomass and of the proportion of taxonomic groups (after Munawar et al., 1987). h. Eastern Station.

Volume 1 95 Table 9. Lake Ontario: Two-sample t-test for the differences between years of the biomass of main phytoplankton groups at the Midlake Station (after Munawar et ai., 1987; ns =not significant).

1970/72 1970177 1970179 1970/83 1972177 1972179 1972/83 1977179 1977/83 1979/83

Cyano

Chloro

Chryso

Diato

Crypto

Dino

Total

p 3.2

SOlem Fig. 6 c. Lake Erie 1970: Seasonal changes of the spatial distribution of Cyanophyta (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 147 CHLOROPHYTA 1970

May 6

gm~

El

3.2

50km

Fig. 7 a. Lake Erie 1970: Seasonal changes of the spatial distribution of Chlorophyta (maps created using contouring analysis of the SPANS Geographic Infonnation System).

Volume 1 148 CHLOROPHYTA 1970

July 27

Aug 26

Sep 22

~ 0.1-0.2

l%J 0.2-0.4

I lI D 0.4-0.8

II 0.8-1.6

Ih6-3.2 •

> 3.2

50m Fig. 7 b. Lake Erie 1970: Seasonal changes of the spatial distribution of Chlorophyta (maps created

Volume 1 149 CHLOROPHYTA 1970

Nov 20

Dec 13

gm"""'*

8

3.2

SOlon Fig. 7 c. Lake Erie 1970: Seasonal changes of the spatial distribution of Chlorophyta (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 150

CHRYSOPHYCEAE1970

May 6

Jun 2

Jul2

g m-"3

S

3.2

501em Fig. 12 a. Lake Erie 1978: Seasonal changes of the spatial distribution of phytoplankton biomass (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 165 TOTAL BIOMASS 1978

Aug 19

Sep 13

Sep 30

9

3.2

50km Fig. 12 b. Lake Erie 1978: Seasonal changes of the spatial distribution of phytoplankton biomass (maps created using contouring analysis ofthe SPANS Geographic Information System).

Volume 1 166 CYANOPHYTA 1978

Jun 19

Jul 13

9

m~

E;3 < 0.1

~ 0.1-0.2

W&l 0.2-0.4

I DI I 0.4-0.8

IV 0.8-1.6

III 1.6-3.2

• > 3.2

50km

Fig. 13 a. Lake Erie 1978: Seasonal changes of the spatial distribution of Cyanophyta (maps

Volume 1 167 CYANOPHYTA 1978

Aug 19

Sep 13

Sep 30

gm~

El

3.2

SOlan Fig. 13 b. Lake Erie 1978: Seasonal changes of the spatial distribution of Cyanophyta (maps

Volume 1 168 CHLOROPHYTA 1978

Jun 19

gm~

~ 3.2

50km Fig. 14 a. Lake Erie 1978: Seasonal changes of the spatial distribution of Chlorophyta (maps

Volume 1 169 CHLOROPHYTA 1978

Aug 19

Sep 13

Sep 30

gm~

8

3.2

50km

Fig. 14 b. Lake Erie 1978: Seasonal changes of the spatial distribution of Chlorophyta (maps

Volume 1 170 CHRYSOPHYCEAE 1978

Jun 19

Jul 13

gm~

9

3.2

50km Fig. 15 a. Lake Erie 1978: Seasonal changes of the spatial distribution of Chrysophyceae (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1

171

CHRYSOPHYCEAE1978

Aug 19

Sep 13

Sep 30

g m""'3 [;3 < 0.1

~ 0.1-0.2

w.l 0.2-0.4 IIIID 0.4-G.8

110.8-1.6

811.6-3.2

81 >3.2

50km Fig. 15 b. Lake Erie 1978: Seasonal changes of the spatial distribution of Chrysophyceae (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 172 DIATOMEAE 1978

Jun 19

9 m-3

9

3.2

50km Fig. 16 a. Lake Erie 1978: Seasonal changes of the spatial distribution of Diatomeae (maps created

Volume 1 173 DIATOMEAE 1978

Aug 19

Sep 13

Sep 30

gm~

E3 3.2

50km Fig. 16 b. Lake Erie 1978: Seasonal changes of the spatial distribution of Diatomeae (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 174

CRYPTOPHYCEAE1978

gm~

9

3.2

50km Fig. 17 a. Lake Erie 1978: Seasonal changes of the spatial distribution of Cryptophyceae (maps

created using contouring analysis of the SPANS Geographic Information System).

Volume 1 175

CRYPTOPHYCEAE1978

Aug 19

Sep 13

Sep 31

gm~

9

3.2

f-~

50km

Fig. 17 b. Lake Erie 1978: Seasonal changes of the spatial distribution of Cryptophyceae (maps

created using contouring analysis of the SPANS Geographic Information System).

Volume 1 176 DINOPHYCEAE 1978

Jun 19

Jul 13

Jul31

gm"""3

EI < 0.1

~ 0.1-0.2

l%l 0.2-0.4

IIIill 0.4-0.8

II 0.8-1.6

111.6-3.2

II> 3.2

50km Fig. 18 a. Lake Erie 1978: Seasonal changes of the spatial distribution of Dinophyceae (maps created using contouring analysis of the SPANS Geographic Information System).

Volume 1 177 DINOPHYCEAE 1978

Aug 19

Sep 13

Sep 30

g m-3

8

E

o

0.8 04

o

04

0.8

J

1.21

o

04j

o

j

II

-,--

Ochromonas sp.

APR

"

,"

,' , «''',

MAY JUN

JUL

AUG

SEP OCT

NOV

",

. DEC

.

,~~-'

'r''' ' , . "'-T. ~ .'-'-'r-.~.~t--r-.r

- - Stephanodiscus tenuis . - - - Fragilaria crotonensis

............ ~

0.8

1.36,

APR

-

/ -- _

-____

MAY JUN

___ --,"

JUL

AUG

I

SEP

OCT

NOV

r - ".

I

DEC

Gymnodiniumhelveticum .... Gymnodinium uberrimum

I-~

V \

r---'-r~"

:' \\'" /

-

,"\

,

- - Ceratium hirundinella . . .. Peridinium aciculiferum

.Ahodomonas minuta . . .. Cryptomonas erosa

o.J ~

o

04

1.2

1.6

2.0

o

0.4

T---'

r ---,--.---.--.---,------,

- - Stephanodiscus niagarae . ... Fragilaria capucina

I

6

--I

,','~

cosma~

i i i

0.8

1.2

L6

Fig. 21. Species succession of phytoplankton in the eastern basin of Lake Erie, 1970 (after Munawar & Munawar, 1976).

"1

04

o I

~T='---~---~=:r=-=..,............

- - Staurastrum paradox~~ 04j .... Oedogonlum sp._"" -""

o

04~

- - Aphanizomenon flos·aquae . ... Chroococcus dispersus ,-_ var minor

EASTERN BASIN

...... 00 ......

Volume 1

Volume 1 182 Table 4. Lake Erie, western basin, 1970: Mean percent biomass of common species (contributing % to the phytoplankton biomass; Munawar & Munawar, 1976).

~5

Apr 7

Fragilaria crotonensis (Edw.) Kitton Stephanodiscus tenuis Hust. Melosira binderana Kiltz.

62.5 17.0 8.5

May 6

Cryptomonas erosa Ehr. Stephanodiscus tenuis Rhodomanas minuta Skuja Melosira binderana

20.5 14.5 9.0 7.5

Jun 2

Cryptomonas erosa Rhodomonas minuta Gymnodinium helveticum Penard Staurastrum paradoxum (Meyen) Stephanodiscus tenuis

18.0 14.0 12.0 8.5 7.5

Jul3

Cosinodiscus rothii (Ehr.) Griln. Cryptomonas erosa Stephanodiscus niagarae Ehr. Rhodomonas minuta Aphanizomenon flos-aquae (L.) Ralfs

23.0 22.0 9.5 8.0 9.0

Jul25

Ceratium hirudinella (Milller) Schrank Pediastrum simplex (Meyen) Lemm. Aphanizomenon flos-aquae Stephanodiscus niagarae Coscinodiscus rothii Cryptomonas erosa

20.5 19.5 13.0 10.0 9.0 7.5

Aug 25

Coscinodiscus rothii Aphanizomenon flos-aquae Cryptomonas erosa Rhodomonas minuta

35.5 14.0 12.5 10.0

Sep23

Coscinodiscus rothii Aphanizomenon flos-aquae Rhodomonas minuta Stephanodiscus tenuis Crypyomonas erosa

27.0 20.0 13.5 6.5 6.5

Oct 21

Coscinodiscus rothii Melosira islandica Milller

40.5 27.5

Nov 25

Stephanodiscus niagarae Stephanodiscus tenuis Coscinodiscus rothii Melosira islandica Cryptomonas erosa

18.5 20.0 14.0 10.5 6.5

Dec 14

Stephanodiscus tenuis Stephanodiscus niagarae Fragilaria crotonensis (Edw.) Kitton Melosira islandica

28.0 16.0 10.0 8.5

Volume 1 183 Table 5. Lake Erie, central basin, 1970: Mean percent biomass of common species (contributing ~5 % to the phytoplankton biomass; Munawar & Munawar, 1976). Apr 7

Stephanodiscus tenuis Hust. Chlorella sp. Stephanodiscus hantzschii var. pusilla Griin. Rhodomonas minuta Skuja Chlamydomonas globosa Snow Melosira binderana Kiitz.

34.0 20.5 12.5 8.0 7.0 5.0

May 6

Stephanodiscus niagarae E. Peridinium aciculiferum (Lemm.) Lemm. Rhodomonas minuta Gymnodinium helveticum Penard Gymnodinium uberrimum (Allman) Kofoid & Sweezy Cryptomonas erosa Ehr.

30.0 17.0 12.0 7.0 7.5 7.0

lun 2

Gymnodinium helveticum Rhodomonas minuta Cryptomonas erosa Chrysochromulina parva Lackey Chroococcus dispersus var. minor G.M. Smith Gymnodinium uberrimum

24.0 23.0 13.5 6.0 5.5 5.0

lui 3

Cryptomonas erosa Fragilaria crotonensis (Edw.) Kitton Rhodomonas minuta

34.0 32.5 15.0

lui 25

Ceratium hirundinella (0. Miill.) Schrank FragiJaria crotonensis Anabaena spiroides Klebahn Oedogonium sp. Aphanizomenon flos-aquae (L.) Ralfs

37.5 13.0 12.5 10.0 8.5

Aug 25

Ceratium hirundinella Staurastrum paradoxum (Meyen) Fragilaria crotonensis

31.0 17.0 15.0

Sep23

Fragilaria capucina (Desm.) Stephanodiscus niagarae Ehr. Ceratium hirundinella FragiJaria crotonensis

37.0 11.0 8.5 7.5

Oct 21

Stephanodiscus niagarae Rhodomonas minuta Cryptomonas erosa

54.0 9.5 6.5

Nov 25

Stephanodiscus niagarae Pediastrum simplex (Meyen) Lemm.

71.0 6.5

Dec 14

Stephanodiscus niagarae Pediastrum simplex

73.5 8.5

Volume 1 184 Table 6. Lake Erie, eastern basin, 1970: Mean percent biomass of common species (contributing % to the phytoplankton biomass; Munawar & Munawar, 1976).

Apr 7

Stephanodiscus tenuis Rust.

85.0

May 6

Peridinium aciculiferum (Lemm.) Lemm Chroococcus dispersus var. minor G.M. Smith Stephanodiscus niagarae Ehr. Gymnodinium uberrimum (Allman) Kofoid & Sweezy Cryptomonas erosa Ehr.

27.0 13.0 9.0 8.0 7.0

Jun 2

Rhodomonas rninuta Skuja Gymnodinium helveticum Penard Ochromonas sp. Cryptomonas erosa Chroococcus dispersus var. minor

37.5 11.0 12.5 10.0 6.0

Jul3

Rhodomonas rninuta Cryptomonas erosa Chroococcus dispersus var. minor Chrysochromulina parva Lackey

34.5 20.0 11.5 10.0

Jul25

Ceratium hirundinella (Muller) Schrank Aphanizomenon flos-aquae (L.) Ralfs Oedogonium sp. Rhodomonas rninuta Cryptomonas erosa

25.0 17.0

Aug 25

Rhodomonas minuta Ceratium hirundinella Cosmarium sp. Pediastrum simplex (Meyen) Lemm. Sphaerocystis sp.

14.0 12.5 13.0 7.0 7.5

Sep23

Ceratium hirundinella Fragilaria crotonensis Rhodomonas minuta Cosmarium sp. Staurastrum paradoxum (Meyen)

22.0 18.0

Cryptomonas erosa Fragilaria crotonensis Fragilaria capucina (Desm.) Pediastrum simplex Staurastrum paradoxum Rhodomonas minuta Stephanodiscus niagarae

15.0

Nov 25

Stephanodiscus niagarae Chlamydomonas globosa Snow

64.5 7.0

Dec 14

Stephanodiscus niagarae

80.0

Oct 21

ll.5 ll .5 6.0

18.5 10.5 7.0

ll.5 10.0 8.0 8.5 9.0 10.0

~5

Volume 1 185 community was dominated by Fragilaria capucina, Coscinodiscus radiatus, and Melosira binderana. This comparison more or less confirms Verduin's findings in that those species that were dominant before 1950 (A. formosa, T. fenestrata, and M. ambigua) continued to be less important in the 1970 collections. A comparison with the diatoms found in 1961 to 1962 shows that Coscinodiscus rothii and Melosira binderana continued to dominate for almost eight years, but F. capucina, although quite common in our collections, is not important when its percent contribution to the total biomass is considered (Table 7). Another comparison can be made with the data of Hohn (1969) on the longterm changes of diatom populations over the past several years based on analyses of data from 1938 to 1940, 1948 to 1949, and 1960 to 1965. He drew a number of conclusions: 1) Species that were previously present in large numbers had almost disappeared (e.g. Cyclotella stelligera and Rhizosolenia eriensis); 2) Tabellaria fenestrata has lost its relative importance in the species complex; 3) Species that were not present or were observed only occasionally have become major dominants (Melosira binderana, Diatoma tenue var. elongatum, Cyclotella meneghiniana, Stephanodiscus alpinus, and S. tenuis); 4) Fragilaria crotonensis has shown a significant increase; 5) Fragilaria capucina has increased in abundance more than any other species during recent years; 6) Coscinodiscus radiatus increased considerably since the 1938 to 1940 collections. The seasonal characteristic features of the three basins of Lake Erie in 1970 can be summarized from a comparative point of view. In the western basin, diatoms were dominant most of the time; blue-greens were abundant during spring and summer, and phytoflagellates were common in the spring. The central basin was also dominated by diatoms, but to a lesser extent during spring and summer. Blue-greens were considerably lower in concentration, and phytoflagellates were more abundant during spring and found in large numbers during summer. The eastern basin was dominated by diatoms only during the fall, as they were absent during the summer. The blue-greens were less abundant, but the green algae were common during the summer. Phytoflagellates were most prevalent in this basin. The species present in 1970 were those which are usually found under mesotrophic and eutrophic conditions. During the spring, the western basin harboured species such as Fragilaria crotonensis, Melosira binderana, Stephanodiscus tenuis, Cryptomonas erosa, and Rhodomonas minuta (Table 4). Central Lake Erie contained species such as Chlamydomonas globosa, Chlorella sp., Melosira binderana, Stephanodiscus hantzschii var. pusilla, S. niagarae, S. tenuis, Cryptomonas erosa, Rhodomonas minuta, Gymnodinium helveticum, G. uberrimum, and Peridinium aciculiferum (Table 5). The spring species composition in the eastern basin was similar to that in the central basin except that e.g. Melosira binderana, found in the western and central basins, and Stephanodiscus hantzschii var. pusilla, occurring in the

Asterionella formosa A. gracillima Cocconeis sp. Coscinodiscus rothii Diatoma elongatum Fragilaria capucina F. crotonensis Melosira binderana M. varians Navicula sp. Nitzschia sp. N. dissipata N. linearis N. palea Rhizosolenia sp. Stephanodiscus hantzschii S. niagarae S. tenuis Surirella angustata Surirella sp. Synedra sp. S. ulna S. utermohlii Tabellaria fenestrata T. flocculosa

Species

x

Apr 7

x

x

x x x x

x

x x

x

x x

x

x

x x x x x

Jun 2

May 6

x

x x

x x

x

x

x x x

x

x

x

x x x x x

x x

Jul25

x x

Jul3

x

x x x

x

Aug 25

x

x

x

x

x

x

x x

x

x

Sep23

x x x x

x

x x x x

x x

Oct 27

x

x

x

x

x

x x

x

Nov 25

x

x

x

x x x x

x

x

x x x

Dec 14

Table 7. Lake Erie, western basin 1970: Occurrences of less common diatom species (contributing