xvEPA
United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
EPA 600 3-80-061
July 1980
Research and Development
Phytoplankton
Composition and
Abundance in
Southern Lake Huron
LIB
U.S.
EDI80M, 2l.J« V
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RESIEARCH REPORTING SERIES
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EPA-600/3-80-061
July 1980
PHYTOPLANKTON COMPOSITION AND ABUNDANCE
IN SOUTHERN LAKE HURON
by
E. F. Stoermer and R. G. Kreis, Jr.
Great Lakes Research Division
University of Michigan
Ann Arbor, Michigan 48109
Grant No. R803086
Project Officer
Nelson Thomas
Large Lakes Research Station
Environmental Research Laboratory-Duluth
Grosse He, Michigan 48138
ENVIRONMENTAL RESEARCH LABORATORY-DULUTH
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
.
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DISCLAIMER
This report has been reviewed by the Environmental Research Laboratory-
Duluth, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views and
policies of the U.S. Environmental Protection Agency, nor does mention of trade
names or commercial products constitute endorsement or recommendation for use.
11
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FOREWORD
Our nation's freshwaters are vital for all animals and plants, yet our
diverse uses of water for recreation, food, energy, transportation, and
industry physically and chemically alter lakes, rivers, and streams. Such
alterations threaten terrestrial organisms, as well as those living in water.
The Environmental Research Laboratory in Duluth, Minnesota develops methods,
conducts laboratory and field studies, and extrapolates research findings
to determine how physical and chemical pollution affects aquatic life
to assess the effects of ecosystems on pollutants
to predict effects of pollutants on large lakes through use of models
to measure bioaccumulation of pollutants in aquatic organisms that are
consumed by other animals, including man
This report, as part of our continuing large lakes study program, details
our findings and interpretations of the present conditions of and the
interactions between the Southern Lake Huron basin and Saginaw Bay.
Norbert A. Jaworski, Ph.D.
Director
Environmental Research Laboratory
Duluth, Minnesota
111
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ABSTRACT
Southern Lake Huron contains a diversity of phytoplankton assemblage types
ranging from assemblages characteristic of oligotrophic waters to those which
usually occur under highly eutrophic conditions. The offshore waters are
generally characterized by oligotrophic associations and most eutrophic
associations are associated with the Saginaw Bay interface waters. Under
certain conditions, populations which are generated within Saginaw Bay are
found mixed with offshore assemblages, apparently as a result of passive
dispersal. The most widely dispersed populations include nuisance-producing
blue-green algae such as Aphanizomenon flos-aquae. During the period of study,
floristic modification resulting from inputs from Saginaw Bay was usually found
along the Michigan coast south of the bay, but cases were noted where greatest
effect was found at stations north of the bay or eastward into the open lake.
These differences appear to be related to circulation patterns governed by
transient meteorological events. Marked changes in phytoplankton abundance and
composition were also noted at stations along the Canadian coastline. This
effect was most pronounced during the spring thermal bar period and appeared to
result from the stimulation of populations characteristic of oligotrophic to
mesotrophic conditions by nutrients from land runoff. Phytoplankton
assemblages in this region were qualitatively and quantitatively dissimilar
from assemblages in Saginaw Bay. On the basis of our results southern Lake
Huron appears to be a somewhat more disturbed region than generally realized.
Phytoplankton assemblage modification appears to result from both the influence
of nutrients and other materials entering the lake directly and from the
dispersal of populations from highly eutrophic Saginaw Bay into the open lake.
The wide dispersal of these populations is of special interest since it may
furnish a mechanism for transport of nutrients and toxic material from highly
impacted Saginaw Bay into the open lake.
iv
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CONTENTS
Page,
Foreword ill
Abstract iv
Figures vi
Tables x
INTRODUCTION 1
Objectives 3
CONCLUSIONS AND RECOMMENDATIONS 4
MATERIALS AND METHODS 6
Sampling Array 6
Archival Plankton Collections ... 6
Samples For Phytoplankton Population Analysis 6
Data Handling and Presentation 10
RESULTS 14
Overall Averages 14
Segment Averages 14
The Phytoplankton Flora of Southern Lake Huron 22
Regional and Seasonal Trends in Total Phytoplankton
Abundance 28
Regional and Seasonal Trends in Abundance of Major
Groups and Selected Taxa 33
Bacillariophyta 33
Chlorophyta 157
Cyanophyta 199
Chrysophyta 240
Cryptophyta 266
Pyrrophyta 280
Microflagellates 296
Vertical Distribution of Phytoplankton at Master Stations . . . 296
Integrated Floristic Effects . 303
Relation of Selected Species to Specific Chemical
Parameters 303
Dimensional Ordination Analysis Utilizing Principal
Components . 317
DISCUSSION 361
References 364
Appendix I - Summary of Phytoplankton Species Occurrence 367
Appendix II - Chronology of Lake Huron Algal Research 378
Bibliography 379
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FIGURES
1 .
2.
3-
4.
5.
6.
7.
8.
9.
10.
11 .
12.
13-
14.
15-
16.
17.
18.
19-
20.
Sampling array, Southern Lake Huron, 1974
Segmentation scheme as recommended by the International Joint
Commission
Seasonal trends of total phytoplankton abundance by segment . .
Seasonal abundance trends of the major algal divisions by
segment
Seasonal abundance and distribution trends of the total
phytoplankton assemblage
Seasonal abundance and distribution trends of diatoms
Distribution of Actinocvclus normanii fo. subsalsa
Distribution of Asterionella formosa
Distribution of Cyclotella comensis
Distribution of Cyclotella comta
Distribution of Cvclotella michiganiana
Distribution of Cyclotella ocellata
Distribution of Cvclotella ooerculata
Distribution of Cvclotella pseudostelligera
Distribution of Cyclotella stelligera
Distribution of Diatoma tenue var. elongatum
Distribution of Diatoma tenue var. pachycephala
Distribution of Fragilaria capucina
Distribution of Fragilaria crotonensis
Distribution of Fragilaria pinnata
Page
7
13
19
21
29
34
38
40
45
49
54
58
63
67
69
73
77
80
85
89
VI
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Page
21 . Distribution of Melosira granulata 94
22. Distribution of Melosira islandica 98
23. Distribution of Nitzschia acicularis 102
24. Distribution of Nitzschia dissioata 106
25- Distribution of Rhizosolenia eriensis 110
26. Distribution of Rhizosolenia gracilis 115
27- Distribution of Stephanodiscus alpinus 119
28. Distribution of Stephanodiscus binderanus 124
29. Distribution of Stephanodiscus hantzschii 128
30. Distribution of Stephanodiscus minutus 132
31. Distribution of Stephanodiscus subtilis 136
32. Distribution of Svnedra filiformis 140
33. Distribution of Svnedra ostenfeldii 145
34. Distribution of Tabellaria fenestrata 149
35- Distribution of Tabellaria flocculosa var. linearis 153
36. Seasonal abundance and distribution trends of green algae . . . 158
37. Distribution of green filament sp. #5 162
38. Distribution of Ankistrodesmus sp 16?
39. Distribution of Chodatella ciliata 171
40. Distribution of Coelastrum microporum 173
41. Distribution of Crucigenia quadrata 176
42. Distribution of Gloeocvstis planctonica 180
43. Distribution of Mougeotia sp 184
44. Distribution of Oocystis spp 189
45. Distribution of Scenedesmus quadricauda 193
vn
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Page
46. Distribution of Staurastrum paradoxum 197
47. Distribution of Tetraedron minimum 201
48. Seasonal abundance and distribution trends of blue-green algae. 205
49. Distribution of Anabaena flos-aquae 209
50. Distribution of Anabaena subcylindrica 213
51. Distribution of Anacystis cyanea 216
52. Distribution of Anacystis incerta 218
53. Distribution of Anacystis thermalis 222
54. Distribution of Aphanizomenon flos-aquae 226
55. Distribution of Gomphosphaeria lacustris 229
56. Distribution of Oscillatoria bornetii ... 233
57. Distribution of Oscillatoria retzii 237
58. Seasonal abundance and distribution trends of filamentous
blue-green algae 241
59. Seasonal abundance and distribution trends of Chrysophytes. . . 246
60. Distribution of Dinobryon divergens 250
61. Distribution of Chrysosphaerella longispina 254
62. Distribution of Chrysococcus dokidophorus 258
63. Distribution of Ochromonas sp 262
64. Seasonal abundance and distribution trends of Cryptomonads . . 267
65. Distribution of Cryptomonas ovata 271
66. Distribution of Rhodomonas minuta var. nannoplanctica 275
67. Seasonal abundance and distribution trends of dinoflagellates . 279
68. Distribution of Peridinium spp 284
69. Distribution of Spirodinium sp 288
70. Seasonal abundance and distribution trends of microflagellates. 292
71. Vertical distribution of total phytoplankton cell densities at
master stations 297
viii
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Page
72. Vertical distribution of diatoms at master stations 298
73. Vertical distribution of green algae at master stations .... 299
74. Vertical distribution of blue-green algae at master stations . 300
75. Vertical distribution of chrysophytes at master stations ... 301
76. Vertical distribution of cryptomonads at master stations . . . 302
77. Vertical distribution of dinoflagellates at master stations . . 304
78. Vertical distribution of microflagellates at master stations . 305
79. Correlation plots of Aphanizomenon flos-aauae vs. chloride . . 307
80. Correlation plots of Aphanizomenon flos-aauae vs. nitrate . . . 308
81. Correlation plots of green filament sp. #5 vs. chloride .... 311
82. Correlation plots of green filament sp. #5 vs. nitrate .... 312
83. Correlation plots of Fragilaria capucina vs. chloride ..... 313
84. Correlation plots of Cvclotella comensis vs. silica 315
85. Correlation plots of Cvclotella comensis vs. nitrate 316
86. Correlation plots of Cyclotella ocellata vs. silica 318
87. Cruise 1 phytoplankton associations as determined by
dimensional ordination and principal components analysis. ... 319
88. Cruise 2 phytoplankton associations as determined by
dimensional ordination and principal components analysis. . . . 324
89. Cruise 3 phytoplankton associations as determined by
dimensional ordination and principal components analysis. . . . 328
90. Cruise 4 phytoplankton associations as determined by
dimensional ordination and principal components analysis. . . . 334
91. Cruise 5 phytoplankton associations as determined by
dimensional ordination and principal components analysis. . . . 339
92. Cruise 6 phytoplankton associations as determined by
dimensional ordination and principal components analysis. . . . 344
93. Cruise 7 phytoplankton associations as determined by
dimensional ordination and principal components analysis. . . . 350
94. Cruise 8 phytoplankton associations as determined by
dimensional ordination and principal components analysis. ... 351
ix
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TABLES
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Sampling sequence and depths sampled at all stations
Format of phytoplankton data reduction
Statistical summary of SLH phytoplankton for all cruises. . . .
SLH station groupings according to the segmentation scheme. . .
Yearly average absolute abundance of the major algal divisions
by segment
Yearly average relative abundance of the major algal divisions
by segment.
Average total phytoplankton standing crop by segment
Average diversity of phytoplankton assemblages by segment . . .
Absolute abundance of diatoms by segment
Absolute abundance of green algae by segment
Absolute abundance of blue-green algae by segment
Absolute abundance of chrysophytes by segment ....
Relative abundance of diatoms by segment
Relative abundance of green algae by segment
Relative abundance of blue-green algae by segment . .
Relative abundance of chrysophytes by segment ....
Correlation matrix of A_phan,;ir3Qmejip.n .fA.Qs-aqua_e vs. macronutrient
values for Cruise 7
Correlation matrix of green filament sp. #5 vs. macronutrient
values for Cruise 8
Correlation matrix of Fragjylar^a capucina vs. macronutrient
values for Cruise 3
8
11
15
16
17
17
20
20
23
24
24
25
25
26
26
27
306
310
310
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Page
20. Correlation matrix of Cvclotella comensis vs. macronutrient
21.
22.
23.
24.
25.
26.
27-
28.
29.
values for Cruise 6
Correlation matrix of Cvclotella ocellata vs. macronutrient.
values for Cruise 4 . . . .....
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 1 ...
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 2 ...
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 3 ...
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 4 . . .
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 5 ...
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 6 ...
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 7
Summary of average species abundance by region as determined by
ordination and principal components analysis for Cruise 8 ...
314
~J ' '
314
_J ' T
320
325
329
335
340
345
352
358
XI
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INTRODUCTION
Compared to the other Great Lakes, there has historically been little
research on the composition, distribution, and seasonal cycles of phytoplankton
assemblages in Lake Huron (Davis, 1966). More recently, Vollenweider et ajj,.
(197*0 have summarized the current status of knowledge in this area and have'
presented a synthesis based on both previous studies and their own previously
unpublished observations. In Appendix II of this report, we have compiled a
list of publications dealing with algal populations in Lake Huron that have
come to our attention. The majority of these report limited observations from
one, or a limited number of sites and are of peripheral interest. There are
several recent publications, however, which merit further attention in the
context of the present study. Schelske and Roth (1973) found sufficient
differences to divide the open waters of Lake Huron into three north-south
zones. The types of differences noted could be interpreted as reflecting a
higher degree of eutrophication of southern Lake Huron than had previously been
suspected. Schelske and Roth emphasized that Saginaw Bay differed drastically
from the rest of the lake and imply that materials entering the open lake from
Saginaw Bay have measurable effects, particularly on the southern region.
Subsequently Schelske ji. ^i.. (1974) demonstrated that there were consistent
north-south differences in phytoplankton species composition at stations along
the Michigan coast of Lake Huron which could be interpreted as reflecting some
degree of eutrophication in the southern part of the lake. This study also
showed that certain phytoplankton populations characteristic of highly
eutrophic conditions were transported from Saginaw Bay to the open waters of
Lake Huron, at least under certain conditions. More recently Schelske et_ .gJL.
(1976) have demonstrated the transport of populations developed under severely
silica-limited conditions in Lake Michigan into Northern Lake Huron through the
Straits of Mackinac. Although this indicates slight eutrophication of northern
Lake Huron due to this transport, it should be emphasized that transport from
Saginaw Bay presents a much more serious problem in terms of water quality
management. While populations transported from Lake Michigan have little or no
nuisance potential, those coming from Saginaw Bay are often associated with
direct water quality problems. It is also apparent that the total flux of
nutrients and conservative contaminants is higher from Saginaw Bay than through
the Straits. The same general implication can be derived from Lowe's (1976)
study of phytoplankton populations at several nearshore localities along the
Michigan coast. Lowe's data additionally show that certain nearshore localities
in the northern sector of the lake support large populations of species
possibly associated with eutrophied conditions. For instance, Lowe found much
higher phytoplankton abundance in Thunder Bay, near Alpena, than at comparable
stations in other parts of northern Lake Huron. He, however, pointed out the
great differences in assemblages found in Saginaw Bay, compared to the rest of
the lake, as well as the effects of the Saginaw Bay discharge on nearshore
stations south of the bay. Nicholls .et .ajL. (1975) have also shown local areas
of eutrophication at nearshore localities in Georgian Bay.
-------
In summary, the limited evidence available indicates that certain
nearshore areas in Lake Huron are significantly eutrophied. There is also
increasing evidence that materials derived from Saginaw Bay are having
significant effects on the rest of Lake Huron, particularly the waters of the
southern basin. As might be expected, this evidence suggests that the direct
effects of the Saginaw Bay discharge are highly dependent on meteorological
conditions and resultant circulation patterns.
It should be emphasized here that conditions in Saginaw Bay are exemplary
of perhaps the worst water quality degradation found in the Great Lakes
system. This region has had a long history of water quality problems including
obnoxious blue-green algal blooms, taste and odor problems in municipal water
supplies, and fish flesh tainting. The historical context of present problems
in Saginaw Bay has been reviewed by Freedman (1974). Vollenweider et al.
(1974) emphasize that certain regions of Saginaw Bay have the highest
phytoplankton standing crop and highest rates of productivity found within the
Great Lakes system. While this reflects the high nutrient loading reaching the
bay, the qualitative composition of the phytoplankton assemblage also reflects
high conservative element loadings (Beeton _et_ a_l. , 1967) and quite possibly the
effects of toxic or inhibitory factors. Most significant to this study is that
the outputs from Saginaw Bay to the main body of Lake Huron might be expected
to be different in character than point source stream discharge entering the
lake, in that, nutrients entering the system have already been "processed"
through a highly specialized phytoplankton flora, quite different from the
assemblage found in most parts of the Great Lakes system. The data of Schelske
j_t aJ. (1974) indicate that most of the nutrients discharged into Saginaw Bay
are already sequestered by phytoplankton by the time they reach main Lake
Huron. These data also indicate that certain populations generated in Saginaw
Bay survive and are dispersed into Lake Huron, while others are apparently lost
rapidly through sinking, predation, or cell death and lysis.
This study is part of a general investigation of Saginaw Bay and Southern
Lake Huron. Included in the general investigation are studies of chemical
conditions in Saginaw Bay (Smith _et_ _a_l. , 1976), chemical conditions and
productivity in southern Lake Huron (Schelske et al., 1977 in prep.),
crustacean zooplankton standing stock and feeding rates (McNaught et al., 1977
in prep.), rotifer standing crop and distribution in southern Lake Huron and
Saginaw Bay (Gannon _et_ a\^. , 1977 in prep.), crustacean zooplankton numbers and
biomass in Saginaw Bay (Gannon _et_ al_. , 1977 in prep.), phytoplankton
composition and biomass in Saginaw Bay (Stoermer et_ _al_. , 1977 in prep.) and a
general model synthesis of conditions and processes in Saginaw Bay (Bierman et
al., 1977 in prep.) and southern Lake Huron (Di Toro et al., 1977 in prep.).
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OBJECTIVES
1. A quantitative assessment of phytoplankton standing crop and
composition in southern Lake Huron.
2. Provision of a complete set of archival samples which can serve as an
objective reference against which possible future changes in the
system may be judged.
3. An assessment of the degree to which populations generated in Saginaw
Bay are transported to the open waters of Lake Huron and the extent
of their subsequent survival and dispersal within the southern
portion of the lake.
4. Provision of independent estimates of size fraction, biomass, and
qualitative physiological group information to modeling efforts.
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CONCLUSIONS AND RECOMMENDATIONS
The phytoplankton flora of southern Lake Huron contains elements characteristic
of the entire range of conditions in the Great Lakes from oligotrophic to
hypereutrophic.
On the basis of phytoplankton assemblage distribution, it appears that there
are three primary input sources which modify the phytoplankton flora of
southern Lake Huron.
The most important of these is Saginaw Bay, Most of the eutrophic
elements in the flora are apparently generated from this source and its
influence is continuous and affects a substantial portion of southern Lake
Huron.
Phytoplankton abundance and composition are also modified by inputs from
the Canadian shoreline. The effects from these inputs are less drastic
and apparently less widespread than the effects of the Saginaw Bay inputs.
Phytoplankton abundance and composition also appear to be modified by
input from sources on the U. S. shoreline south of Saginaw Bay. The
influence of this source of perturbation is less well defined, partially
because in most cases studied the area of effect is also under the
influence of the effluent from Saginaw Bay.
The nature of phytoplankton assemblage perturbation resulting from the
influence of these sources is different in the three cases.
In the case of Saginaw Bay, floristic modification results from both
transport of materials from the bay and from transport of phytoplankton
populations generated within the bay to the open lake. In general, the
floristic response is characteristic of both high nutrient and high
conservative element loadings.
Modification of the phytoplankton assemblage along the Canadian coast
appears to result from stimulation of populations characteristic of
oligotrophic to mesotrophic conditions within the lake. The primary
effect in this case appears to result from nutrient addition.
Phytoplankton assemblages at stations on the southern U. S. coast appear
to reflect both secondary stimulation of scenescent populations generated
in Saginaw Bay and injection of certain populations unique to this area.
Certain of these populations usually find their primary habitat in benthic
associations.
The extent of influence of apparent sources is seasonally variable and
apparently strongly dependent on physical conditions at the time of sampling.
During the period of study, the influence of Saginaw Bay was most commonly
found at stations along the U. S. coast southward from the bay. In some
instances, however, the influence of discharges from the bay was
widespread in the open lake and in one instance the main effect of
materials from Saginaw Bay was found at stations along the U. S. coast
-------
north of the bay.
The effect of sources on the Canadian coastline is most pronounced during
the spring. This apparently results from the combined effects of the
spring peak in runoff and the effects; of the spring thermal bar which
tends to restrict material entering the lake to the nearshore zone.
Biotic interactions strongly influence the; distribution and eventual fates of
populations injected into southern Lake Huron from Saginaw Bay. Certain
populations, particularly some of the largfer diatoms, are lost from the water
mass rapidly, apparently through sinking. Other populations, particularly
certain species of blue-green algae, have a much longer residence time in the
water mass and are dispersed for considerable distances. Our data indicate
such populations could reach any part of southern Lake Huron under the proper
conditions.
This process should be studied in greater detail since it may be an
important mechanism in transporting nutrients and toxic materials from
highly impacted areas to the open lake.
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MATERIALS AND METHODS
SAMPLING ARRAY
The basic sampling array utilized in this study is shown in Fig. 1.
Station locations were chosen to provide greatest sampling density in the
Saginaw Bay interface region and less dense coverage over the rest of the
region. The constraints of sampling platform availability and the necessity to
accomodate the needs of several projects on cruises resulted in compromises
which render the design something less than ideal for the purposes of this
particular project. Specifically, it would have been highly desirable to have
additional stations in the southwestern quadrant of the sampling array (region
bounded by stations 14, 60, and 63) and in the northeastern quadrant (area
bounded by stations 20, 23, 53, and 56). Depths sampled at each station and
the sequence of sampling are given in Table 1. On some occasions weather
conditions led to deviations from the planned sampling schedule and, in a
limited number of instances, certain stations were not sampled on a particular
cruise. Any such omissions are noted on the following data plots.
Samples at all stations were taken as splits from a single 8 £ Niskin
bottle cast. In the following, we will discuss processing of the samples
utilized in this particular investigation. A more complete account of the
complete sampling routine can be found in Schelske et_ .§JL. (1977 in prep.).
ARCHIVAL PLANKTON COLLECTIONS
Archival samples were taken from all stations and depths sampled. Samples
were drawn as U subsamples of the original 82. Niskin bottle sample.
Subsamples were immediately filtered onto 47-mm Millipore "AA" cellulose
acetate membrane filters and placed in 5-dram amber glass capsule vials.
Material was preserved in a mixture of six parts water of collection, three
parts 95% ethanol, and one part commercial formalin. Samples were labeled and
sealed immediately following preservation.
SAMPLES FOR PHYTOPLANKTON POPULATION ANALYSIS
Samples for phytoplankton population analysis were taken as a 150-ml split
of the original 8X, Niskin bottle sample. These subsamples were immediately
fixed with glutaraldehyde (4$ by volume) and stored in the dark at
approximately 4 C for at least 4 hr to assure complete fixation. After
fixation, sample bottles were gently agitated to assure resuspension of
phytoplankton present and a 50-ml volume was withdrawn for further processing.
The remaining sample volume of fixed sample was retained as a contingency
sample until the subsequent processing steps were successfully completed, then
discarded. Material was concentrated by filtration onto 25 mm "AA" Millipore
-------
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TABLE 1. SAMPLING SEQUENCE AND DEPTHS AT ALL STATIONS
Station No.
Day 1
63
64
65
06
07
09
10
11
58
Day 2
57
56
20
21
23
24
25
26
Day 3
36
37
38
39
40
41
42
43
44
47
46
45
Day 4
48
49
50
Sampling Depths
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
5
5,
5,
5,
5,
5
5,
5,
5,
5
5,
5,
5,
5,
5,
5,
5
5
5,
5,
5,
5
5,
5,
5,
5,
5,
5
5,
5,
5,
5,
10,
10,
10
10,
10,
10,
10,
10,
10,
10,
IP,
10,
10,
10,
10
10
10
10,
10,
10,
10,
10
10,
10,
10,
15
15
15,
15
15,
15,
15,
15,
15,
15,
15,
15,
15
15,
15,
15,
15,
15,
15,
15
20, 25
20, 30, 40, 50, 60
20, 30 # bottles: 40
20
20, 30, 40
20, 30, 40, 60, 80, 9Q
20, 30, 40, 50
20, 30, 40, 50, 60
20, 30, 40, 50
# bottles: 51
20
20, 25
20
20, 30, 40
# bottles: 45
20, 30, 40
20, 30, 40
(continued)
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TABLE 1 (continued)-
Station No.
Day 1 Sampling Depths
Day 4
51 1, 5, 10, 15, 20, 30
16 1, 5, 10, 15, 20, 30
55 1, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80
54 1, 5, 10, 15, 20, 30, 40, 50, 60
53 1, 5, 10, 15, 20, 30, 40
52 1, 5, 10, 15, 20 # bottles: 62
Day 5
15 1, 5
14 1, 5, 10
67 1, 5, 10, 15, 20, 25
13 1, 5, 10, 15, 20, 25
66 1, 5, 10, 15, 20, 30, 40, 50
60 1, 5, 10, 15, 20, 30, 40 # bottles: 32
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filters, partially dehydrated through an ethanol series and embedded in clove
oil. Prepared filters were mounted on 50 x 75-mm glass slides and covered with
a 43 x 50-mm, # 1 thickness cover glass. Preparations were kept in a
horizontal position and allowed to dry for approximately 2 weeks, during which
time the embedding medium lost through volatilization was periodically
replaced. The edges of the cover glass were then sealed with paraffin.
Preparations were analyzed by visual counts of phytoplankton cells present
using a Leitz "Ortholux" microscope fitted with fluorite immersion objectives
with a nominal Numerical Aperature of 1.32. Magnification used for
identification and enumeration was approximately 1200 X. Population estimates
given are the averaged counts from two 10 mm radial strips, corrected for
volume filtered. Effective filtration diameter in the filtration apparatus
used is 20 mm.
DATA HANDLING AND PRESENTATION
Reduction and meaningful presentation of the amount of taxonomic data
generated by a project of this size present certain problems which are
difficult to resolve in a manner completely satisfactory to all potential
users. We would like to outline here our approach to this problem and to
specify the formats and stages of reduction of the available data.
Raw counts from bench sheets were encoded in computer compatible format on
punched cards. Initial card input was machine verified against a master
taxonomic code file and card listings were hand verified against bench sheets.
After any necessary corrections were made, these cards served as a primary data
archive.
First-cut data reduction is in the format shown in Table 2. Summaries
include estimates of absolute frequency and estimates of associated error and
an estimate of relative abundance for all taxonomic categories. The same
information is also provided for data summarized at the level of major
physiological division. Assemblage parameters calculated include an estimate
of total phytoplankton abundance and a measure of error associated with the
estimate, an estimate of assemblage diversity (H), and an estimate of the
evenness component of the calculated diversity. These semi-reduced data were
reproduced as hard copy for final verification, then reduced to tape file
storage. Subsequent data reduction and manipulation routines operated on these
files.
Since the semi-reduced data are too extensive to be economically
reproduced in standard report format, but may be of interest to other
investigators, we have transmitted copies (on tape file) to the project officer
and copies can be obtained from that source. Permanent files are also
maintained at this institution.
Data display in the results section following is in three main formats:
1. A complete listing of the taxa encountered during the study is
given. This summarization includes the number of occurrences of each
10
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ana the maximum absolute and relative abundance found in any sample.
Since one of the main objectives of this project was to assess the
pattern of phytoplankton distribution in Southern Lake Huron, the
distribution of many of the more quantitatively important taxa and
major physiological groups have been plotted.
Finally, we have made a broad scale summarization of abundance of
both total phytoplankton and some of the major groups according to
the lake segmentation scheme proposed by the International Joint
Commission (1976). The segmentation adopted by IJC is shown in
Fig. 2. Because some of our stations fall on the Saginaw Bay side of
the proposed Lake Huron segmentation, we have added an additional
segment, designated as 7A on the figure, which furnishes comparison
with conditions found near the mouth of Saginaw Bay.
12
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RESULTS
OVERALL AVERAGES
The overall abundance of phytoplankton at all stations in all cruises
sampled during the study is shown in Table 3. As will be noted from Table 3,
total average phytoplankton abundance within the area is moderate. However
there is an extreme range in the phytoplankton concentrations which were
encountered during the study. Of the major physiological groups present in the
phytoplankton, diatoms are most abundant in southern Lake Huron and the green
and blue-green algae comprise a lesser but still important part of the flora.
Chrysophytes and cryptomonads, although present at nearly all stations sampled,
are on the average minor components of the flora. Dinoflagellates constitute a
very minor portion of the flora in terms of cell numbers, however due to the
very large cells of some species, they may be an important part of the
biomass. Euglenoids, although present, comprise a very minor fraction of the
phytoplankton standing stock. In Table 3, an undetermined category is
indicated. This category is comprised almost entirely of microflagellates
which cannot be satisfactorily determined under the light microscope. Many of
these organisms probably belong to the algal division Haptophyta (Stoermer and
Sicko-Goad, 1977; Sicko-Goad, Stoermer, and Ladewski, 1977).
SEGMENT AVERAGES
In order to inspect regional differences during the reference study, the
offshore waters of Lake Huron have been segmented according to the scheme shown
in Fig. 2 (Smith _et_ a_l. 1976). For the purposes of this study, an additional
segment labeled segment 7A in Fig. 2 has been designated which includes the
waters in the Lake Huron-Saginaw Bay interface. A compilation of the stations
sampled during this study according to their segment position is given in Table
A. The yearly average abundance of phytoplankton belonging to the major
physiological divisions is given in Table 5. It will be noted that the average
standing crop in segment 7A is significantly higher than in the other
segments. Segments 7 and 8 have comparable standing crop levels, while segment
6 is significantly lower in phytoplankton abundance. In the case of the major
physiological groups, the diatoms, the blue-greens, and particularly the green
algae are significantly more abundant in segment 7A than in the other
segments. The same trend is exhibited by the minor groups with the exception
of the cryptomonads which are slightly more abundant in segment 6. As will be
seen later, differences at the major group level are reflective of even larger
differences at the specific population level.
The relative abundance of the major physiological groups by segment is
shown in Table 6. On average, diatoms are the most important component of the
flora, with similar relative abundances in segments 6 and 8, somewhat reduced
-------
TABLE 3. STATISTICAL SUMMARY OF
SOUTHERN LAKE HURON PHYTOPLANKTON
CRUISES 1-8 AT 5 METER DEPTH
AVE. CELLS /ML 2100.7
RANGE 38221.0 - 293.22
STANDARD DEVIATION 3165.3
MEAN DIVERSITY 2.2923
Blue-greens
Greens
Diatoms
Chrysophytes
Cryptomonads
Dinof lagellates
Euglenoids
Undetermined
Ave. Relative
Abundance %
13.46
20.17
55.72
4.72
1.34
.10
.00
4.46
Ave.
Cells/ml
381.39
777.08
790.52
75.72
16.36
1.31
.03
58.18
-------
TABLE 4. SOUTHERN LAKE HURON
STATIONS GROUPED ACCORDING TO THE
SEGMENTATION SCHEME
Segment 6 7a
20 36
21 37
38
39
40
41
42
43
44
45
7
6
13
14
15
16
23
24
25
26
46
47
48
49
50
51
52
53
63
64
65
67
8
7
9
10
11
54
55
56
57
58
60
66
16
-------
TABLE 5. YEARLY AVERAGE ABSOLUTE ABUNDANCE (CELLS/ML) OF
ALGAL DIVISIONS BY SEGMENT FOR CRUISES 1-8 AT 5 METER DEPTH
co
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7a 695.37 2130.48 969.75 120.74
]_ 294.34 382.12 753.82 74.50
8^ 214.46 134.31 759.14 34.85
CO
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15.47 1.91 51.
12.49 1.06 41.
31
80
97
23
TABLE 6. YEARLY AVERAGE RELATIVE ABUNDANCE ($) OF ALGAL
DIVISIONS BY SEGMENT FOR CRUISES 1-8
AT 5 METER DEPTH
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relative abundance in segment 7, and comprise less than 50 percent of the total
flora only in segment 7A. Green algae are significantly more abundant in
segment 7A than in the other segments. On the other hand, the relative
abundance of blue-greens is similar in segments 7, 7A, and 8, but considerably
lower in segment 6. Unlike these groups, the cryptomonads and undetermined
raicroflagellates tend to be relatively more abundant in segment 6 than in the
other segments.
The seasonal trends of total phytoplankton abundance are shown in Fig. 3-
Segment 6 is characterized by having relatively low and stable phytoplankton
assemblage abundance during most of the sampling period, with a slight peak
during August. Unfortunately stations in this segment were not sampled during
the April nor the October and November cruises. The general pattern of
phytoplankton abundance is similar in segment 7, although cell densities are
considerably larger, particularly during the fall maximum. In segment 8,
abundance is on the average somewhat less than in segment 7, and population
densities tend to be more stable with a slightly increased spring peak and a
markedly decreased fall peak. The situation in segment 7A is markedly
different than in the other segments. There is a generally rising trend in
phytoplankton density throughout the period sampled with peaks in late May,
July, and October. Phytoplankton densities in this segment are significantly
larger in all sampling periods than in the other segments. The numerical
averages of phytoplankton cell densities found in each segment by cruise are
shown in Table 7 and the average diversities of the phytoplankton assemblages
at the stations sampled during each cruise is shown in Table 8.
The seasonal trends in major physiological groups are shown in Fig. 4. In
segment 6 diatoms are dominant until July, when they are replaced to a
significant extent by green and blue-green algae. In segment 7 there is a
definite bimodal pattern in diatom abundance with peaks occurring in June and
August separated by an assemblage minimum in July. Green algae, on the other
hand, undergo a slight increase in average density in June, then reach minimum
abundance in July before reaching their seasonal maximum in October. The
blue-green algae only reach significant levels of abundance after June, and
increase to their seasonal maximum in October together with the green algae.
In segment 8, abundance of diatoms is somewhat more erratic, although a
definite spring peak is present. The overall abundance of green algae in this
segment is less than in segment 7, with only weak population peaks in June and
August. Similar to segment 7, the blue-green algae first reach appreciable
abundance in June and reach their seasonal population maximum in October. In
this segment, the blue-greens attain substantially larger abundance than do the
green algae. Segment 7A presents a considerably different picture. Diatom
populations exhibit a pronounced bimodal distribution with peaks in May and
November with a marked population minimum in July. The green algae are much
more abundant in this segment than in the other segments, and show a
considerably different pattern of seasonal succession. The populations rise
from very low abundances in April to maxima in late May. These are followed by
pronounced minima in June. Green algae then increase markedly in abundance to
maximum numbers in July, and remain the dominant element of the flora
throughout the rest of the season sampled. In this segment the blue-green
algae comprise an appreciable part of the phytoplankton assemblage during all
of the sampling cruises. However, they are a relatively minor part of the
18
-------
7000
5000
3000.
1000
SEGMENT
7a
7000
5000.
3000.
1000.
SEGMENT
6
A MJUJUJL A 0 N
AMJUJUJLAON
7000
5000
3000.
1000.
SEGMENT
7
7000
5000
3000
1000.
SEGMENT
8
AMJUJUJLAON
AMJUJUJLAON
Figure 3. Seasonal trends of total phytoplankton abundance (cells/ml)
by segment.
19
-------
TABLE 7. PHYTOPLANKTON STANDING CROP BY SEGMENT.
MEAN VALUES EXPRESSED AS CELLS/ML
FOR CRUISES 1-8 AT 5 METER DEPTH
Ave.
Total
Cells/ml 1
6, 691.58
_7a 3888.13
]_ 1573.87
8 1200.25
670.2 873.4 706.9 686.9 1520.5
1070.9 3169.0 4173.3 2265.9 6150.8 4422.1 6404.0 4519.9
1014.4 1305.5 1626.7 1187.7 700.1 1815.0 2925.5 2017.0
1058.9 1417.6 810.1 1045.1 551.7 1364.2 1861.6 1492.7
TABLE 8. AVERAGE DIVERSITY OF PHYTOPLANKTON FOR CRUISES 1-8
AT 5 METER DEPTH BY SEGMENT
Ave.
8
2.386 2.948 2.661 2.831 1.736 1.753
2.273 2.891 2.682 2.060 2.237 1.694 1.969 2.327 2.274
2.372 2.899 2.874 2.691 2.556 2.006 1.737 2.334 1.908
2.294 2.861 2.869 2.615 2.590 1.864 1.762 1.954 1.825
20
-------
MICRO FLAGELLATES
SEGMENT
7
Figure U. Seasonal abundance (cells/ml) trends of the major algal
groups by segment.
21
-------
total assemblage until July, when they begin a rise to maximum population
densities in October. This seasonal peak is followed by a decline in abundance
in November. Numerical averages of the absolute abundance of major
phytoplankton groups by segment and by cruise are given in Tables 9-12. For
comparison, the relative abundances of these groups are given in Tables 13-16.
THE PHYTOPLANKTON FLORA OF SOUTHERN LAKE HURON
A summary compilation of the taxa occurring in samples taken during this
project is given in Appendix 1. In the appendix, taxa are arranged
alphabetically by genus and by species under the major divisions. In many
cases, taxa were encountered which could not be identified with known species.
In some cases, this is due to the lack of critical life cycle stages or
structures necessary for identification. In other cases, it may be due to the
availablity of only a limited number of atypical specimens. There are
undoubtedly a certain number of taxa which have not been previously described
in the literature. Morphological entities which could only be identified at
the generic level are listed with arbitrary numerical designations under the
appropriate genera. Entities which could not be satisfactorily determined at
the generic level are listed at the end of the divisional classification with
some qualifying descriptor, i.e. undetermined blue-green filament; undetermined
green individual. Unfortunately, in certain instances taxa which could not be
satisfactorily identified are a major element of the phytoplankton flora at
certain stations. This is particularly true in the case of the very small
filamentous green alga designated as undetermined green filament number 5. As
will be seen from the compilation, this taxon is the most abundant entity in
terms of cell numbers found in several stations.
In the compilation, the total number of occurrences for each taxon is
given, followed by the average population density and relative abundance of the
species, which is followed by the maximum level of abundance and percentage of
populations attained. A considerable proportion of the species noted during
this study are probably pseudoplanktonic. For instance, 22 species of the
genus Achnanthes were noted in the samples we examined. Most members of this
genus are sessile in growth habit and they are probably only secondarily
entrained into the plankton. The notable exception to this is Achnanthes
cj.eye.4. var. rggtr^ta which often grows attached to some of the larger
planktonic diatoms and thus, although sessile, is a normal component of
phytoplankton assemblages in the Laurentian Great Lakes.
In the compilation, we have also noted the occurrence of particular life
cycle stages for certain taxa. Examples of this would be auxospore formation
in certain fiycJ.SLte.iLla species which was quite common at certain of the stations
sampled, and statospores formed by genus P4p_gj?rycjn. In a limited number of
cases we have also noted the occurrence of populations which are obviously
morphologically abnormal and this information is included in the compilation.
22
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-------
TABLE 12. ABUNDANCE OF CHRYSOPHYTES (CELLS/ML) FOR SOUTHERN
LAKE HURON BY SEGMENT FOR CRUISES 1-8 AT 5 METER DEPTH
Ave. 12345 6 78
6. 19.47 27.23 5.24 29.32 29.32 6.28
7a 120.74 75.75 92.85 83.57 24.71 91.53 330.50 210.49 56.55
]_ 74.50 37.00 45.38 70.41 24.93 54.55 183.71 166.16 13.86
8 34.85 26.63 18.06 30.37 29.95 22.09 14.28 114.84 22.62
TABLE 13. RELATIVE ABUNDANCE (%) OF DIATOMS IN SOUTHERN
LAKE HURON BY SEGMENT FOR CRUISES 1-8 AT 5 METER DEPTH
Ave. 12345678
j> 66.91 78.13 76.87 78.77 78.50 22.31
7_a 41.67 69.67 64.60 36.88 60.80 22.38 19.19 27.12 32.73
1 58.71 79.20 75.15 66.13 70.30 60.78 56.75 30.06 31.36
8 67.13 82.55 65.82 79.38 79.38 78.66 58.68 45.07 47.19
-------
TABLE 14. RELATIVE ABUNDANCE (%) OF GREEN ALGAE IN
SOUTHERN LAKE HURON BY SEGMENT FOR CRUISES 1-8 AT 5
METER DEPTH
Ave.
1
2
3
4
5
6
7
8
6. 16.67 10.94 12.08 7.03 3.06 50.28
7a 32.02 11.36 22.52 46.43 22.29 52.94 36.14 24.46 40.03
1_ 15.88 8.85 15.80 19.12 6.68 11.73 15.65 26.88 22.38
8 10.92 .15 10.57 18.80 8.40 7.63 24.99 6.53 10.40
TABLE 15. RELATIVE ABUNDANCE (%) OF BLUE-GREEN ALGAE IN
SOUTHERN LAKE HURON BY SEGMENT FOR CRUISES 1-8 AT 5 METER
DEPTH
Ave. 1234 5 6 7 8
1 3.19 0 .02 .49 0 15.47
Ta. 15.01 .15 4.03 5.86 10.79 12.62 26.54 38.07 22.07
]_ 13.21 .10 .39 .48 6.69 10.19 16.19 30.79 40.83
8 11.44 .15 1.10 .30 4.61 0 10.43 38.55 36.39
26
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REGIONAL AND SEASONAL TRENDS IN TOTAL PHYTOPLANKTON ABUNDANCE
In early May (Fig. 5A) phytoplankton density was rather low and uniform in
all stations sampled. Slightly increased assemblage abundance was noted at
stations nearer shore along both the U.S. and Canadian coasts. By mid-May
(Fig. 5B) total phytoplankton abundance had increased markedly at stations in
the Saginaw Bay interface and at stations south along the Michigan coast below
Saginaw Bay. Slight increases in abundance were also noted along the Canadian
shore north and south of Goderich. Phytoplankton abundance during this period
was apparently affected by the spring excursion of the thermal bar, and the
high population densities noted on the eastern Canadian coast are at least
partially reflective of this condition. By early June (Fig. 5C) the effect of
the spring thermal bar was largely dissipated and total phytoplankton abundance
appeared to be controlled by nutrient input from Saginaw Bay. This is marked
by very high phytoplankton densities in the Saginaw Bay interface and somewhat
elevated densities southerly along the Michigan coast below the bay. By late
June (Fig. 5D) total phytoplankton abundance had declined at most stations
sampled. Markedly elevated phytoplankton abundance was noted only at stations
in the southerly sector of the Saginaw Bay interface, with slightly elevated
levels occurring at nearshore stations north and south of Tawas on the Michigan
coast, and north and south of Goderich on the Canadian coast. By mid-July
(Fig. 5E), phytoplankton abundance had further declined at most stations
sampled. However, very high phytoplankton densities were noted at several
stations in the southerly quadrant of the Saginaw Bay interface. During the
late August cruise (Fig. 5F) a general increase in phytoplankton cell numbers
was found throughout the area of study. It should be noted that this is not
necessarily reflective of an increase in biomass of the phytoplankton, since
most of the populations dominant during this period of the year are
small-celled species. Phytoplankton assemblage distribution during this month
is somewhat unusual in that highest cell densities were noted in the northerly
sector of the Saginaw Bay interface. This appears to result from Saginaw Bay
water being transported northward along the Michigan coast during this time
period. In all other cases sampled, it appeared that the dominant transport
was southerly along the Michigan coast. This situation appeared to prevail
during the early October sampling (Fig. 5G) when particularly elevated
phytoplankton cell densities were noted in the southerly sector of the Saginaw
Bay interface and southward along the Michigan coast in the vicinity of Harbor
Beach. Slightly elevated phytoplankton numbers were found at nearshore
stations above Tawas, but these were only on the order of 50 percent or less of
the cell densities found in the southern sector. A similar situation
apparently prevailed at the time of the mid-November sampling (Fig. 5H) when
highest cell densities again occurred in the southerly sector of the Saginaw
Bay interface and southward along the Michigan coast. It should be noted that
during all except the first cruise the pattern of phytoplankton distribution in
southern Lake Huron is strongly dominated by the extremely high cell numbers
found in the Saginaw Bay interface waters.
28
-------
ERST TBHflS
0
28 RPR - 3 MRY 74
GOOERICH
HURON
TOTRL
ERST TRHRS
GOOEBICH
0
14-17 MRY 74
HURON
TOTflL
Figure 5. Seasonal distribution and abundance
trends of the total phytoplankton assemblage
(continued)
29
-------
EAST TflMflS
0
4-8 JUN 74
GOOERICH
IT HURON
TOTRL
ERST TflURS
cooeniCH
0
17-21 JUN 74
HURON
TOTflL
Figure 5. (continued)
30
-------
EflST
0
17-22 JUL 74
HURON
TOTfiL
EflST
0
26-31 flUG 74
HURON
TOTBL
Figure 5. (continued)
31
-------
0
8-12 OCT 74
GOOEJUCH
HURON
TOTBL
ERST TflMflS
CODERICM
0
10-14 NOV 74
HURON
TCTflL
Figure 5. (continued)
32
-------
REGIONAL AND SEASONAL TRENDS IN ABUNDANCE OF MAJOR GROUPS AND SELECTED TAXA
Bacillariophyta
Although as will be seen later there are considerable differences in the
distribution patterns of individual populations, diatoms are an important
component of the phytoplankton assemblages at most stations during all seasons
of the year. In early May (Fig. 6A) diatom abundance tends to be highest at
nearshore stations, with little obvious pattern at the other stations sampled.
This trend is enhanced in the mid-May sampling period (Fig. 6B) when highest
diatom abundance is found at nearshore stations and in the Saginaw Bay
interface waters. Even in the Saginaw Bay stations, however, there is a
considerable increase in diatom abundance in stations nearest shore,
particularly in the southern sector. This distribution pattern is probably
controlled by the spring thermal bar. By early June (Fig. 6C) the thermal bar
has ceased to be an appreciable factor, and diatom abundance is relatively
uniform at the stations sampled, with slightly higher population densities in
stations in the Saginaw Bay interface and southward along the Michigan coast.
Essentially the same situation occurred during the mid-June sampling (Fig. 6D)
although there was a visible increase in diatom abundance at nearshore stations
along the Canadian shore. In mid-July (Fig. 6E) diatom abundance was low but
relatively uniform at most stations sampled. Diatom abundance was strongly
reduced in the central and southerly sectors of the Saginaw Bay interface and,
to a lesser extent, southerly along the Michigan coast. Population densities
similar to those at offshore stations and to nearshore stations on the Canadian
coast were found at nearshore stations in the northern sector of the Saginaw
Bay interface. By mid-August (Fig. 6F) diatom abundance had increased at most
stations south of Saginaw Bay, although the increase was not as large in
stations of the Saginaw Bay interface as at stations in the main body of Lake
Huron. The exception to this trend of increasing diatom abundance was the
relatively low numbers of this group found at stations in the extreme northern
part of the sampling area. In early October (Fig. 6G) diatom abundance was
quite uniform at stations sampled in the main part of Lake Huron, with slightly
increased densities in the Saginaw Bay interface water, particularly at
stations nearest shore. This trend towards increased diatom abundance at
nearshore stations continued during the mid-November sampling period (Fig. 6H)
when diatom abundance was considerably elevated at nearshore stations, possibly
as a result of the development of the fall thermal bar situation.
Actinocyclus normanii fo. subsalsa
This is one of the species which has increased markedly in abundance in
areas of the Great Lakes which have been greatly disturbed (Hohn, 1969). Its
correct classification has been a source of considerable argument and confusion
and it has been reported variously as Coscinodiscus radiatus by Hohn (1969), £.
rothii var. subsalsa, and J3. subsalsa by Stoermer and Yang (1969). Hasle
(1977) has studied this taxon with the scanning electron microscope and
confirmed Hustedt's (1957) contention that it should be included in the genus
Actinocyclus. Its distribution in our study area is relatively limited. One
isolated population was found in the Saginaw Bay interface waters in early May
(Fig. 7A). Maximum abundance of this species occurred during the October
sampling (Fig. 7B) when sizeable populations were found at a group of
33
-------
EBST TBHRS
GODER1CH
0
28 flPR - 3 MflY 74
HURON
OlflT
EBST Tl
0
14-17 MflY 74
ilCH
HURON
DIRT
Figure 6. Seasonal abundance and distribution
of diatoms. (coritinued)
34
-------
EflST TflHflS
GOOERICH
0
4-8 JUN 74
HURON
DIflT
B GOOERICH
0
17-21 JUN 74
HURON
DIflT
Figure 6. (continued)
35
-------
EflST TRHflS
o
17-22 JUL 74
IT HURON
OlflT
ERST TRHflS
0
26-31 flUG 74
ICH
HURON
DIRT
Figure 6. (continued)
36
-------
0
8-12 OCT 74
8GOOERICH
HURON
OlflT
EflST T,
GOOQHCH
0
10-1U NOV 74
HURON
OIHT
Figure 6. (continued)
37
-------
EflST TflMBS J
/v.
GOOEBICH
0
28 RPR - 3 MflT 7U
HURON
CSSSM.SA
EflST TRMflS
GOOERICH
0
8-12 OCT 74
CSSSRLSfl
Figure 7. Distribution of Actinpcyclus normanii
fo. subsalsa. (continued)
-------
stations in the southern sector of the Saginaw Bay interface. Small
populations were also found during November (Fig. 7C) at stations in the
Saginaw Bay interface. It reaches its greatest abundance in the inner bay
during fall.
Asterionella formosa
This well-known and apparently eurytopic phytoplankton dominant occurs in
all areas of the Great Lakes under conditions ranging from pristine to highly
disturbed. Like many similar "weed" phytoplankton species, it does not appear
to respond to other than extreme changes in environmental conditions. In
southern Lake Huron its distribution is not as highly patterned as that of some
more sensitive species. During early May (Fig. 8A) populations of this species
were found at all stations sampled, but no pattern of distribution was
evident. During mid-May (Fig. 8B) population levels tended to be highest at
nearshore stations along the Canadian shore and, to a lesser extent, at the
outer stations in the Saginaw Bay interface and southward along the U.S.
shore. During early (Fig. 8C) and late (Fig. 8D) June the distribution of this
species was rather erratic, with a slight tendency for higher population levels
to occur along the U.S. shore in early June, and in the Saginaw Bay interface
and southward along the U.S. shore in late June. In mid-July (Fig. 8E)
populations were markedly reduced except at stations in the southern part of
main Lake Huron, and in the northerly part of the Saginaw Bay interface. This
trend continued in August (Fig. 8F) when A. formosa was absent, or
EAST TAWS
GOOQUCH
0
10-1U NOV 74
HURON
CSSSBLSfl
Figure 7. (continued)
39
-------
EflST TflHflS
GODERICH
0
28 RPR - 3 MflY 7U
HURON
EflST TflMBS
GOOERICH
0
m-17 MflY 74
HURON
HSFOrtlOS
Figure 8. Distribution of Asterionella
formosa. (continued)
40
-------
ERST TRIMS
GOOERICH
0
4-8 JUN 74
HURON
RSFORMOS
0
17-21 JUN 74
HURON
RSFORHOS
Figure 8. (continued)
-------
EflST TflNflS
0
17-22 JUL 74
BtGOOERICH
HURON
HSFORMOS
0
26-31 RUG 74
ttGOOERICH
HURON
HSFORHOS
Figure 8. (continued)
-------
only present in minimal numbers, except at nearshore stations and stations in
the Saginaw Bay interface. As is the case for several other taxa during this
month, highest population levels were found at nearshore stations along the
northerly coast of Saginaw Bay. This species generally increased in abundance
by the October sampling period (Fig. 8G) with highest population levels again
being found in the Saginaw Bay interface waters. This trend apparently
continued into November (Fig. 8H) when maximum population levels were found in
the southerly sector of the Saginaw Bay interface and southward along the
Michigan coast. Slightly increased abundance was also noted at nearshore
stations along the Canadian shoreline.
Cyclotella comensis
The seasonal distribution of this species in southern Lake Huron is quite
unusual. Although small populations were detected during the April sampling
(Fig. 9A) it achieved only very low population densities during May, June, and
July (Figs. 9B-E). In August (Fig. 9F) it appeared in bloom quantities at most
stations sampled. Population densities were reduced only at stations in the
Saginaw Bay interface waters, particularly in the northern sector where other
species' populations were generally highest, and conversely at stations in the
far northern part of the sampling array where most other species' populations
were found in their lowest abundance. Although somewhat less abundant during
the October sampling period than it had been the previous month, substantial
populations were still found at most stations sampled during October (Fig. 9G),
with highest abundance in the northerly sector of the Saginaw Bay interface.
Abundance of this species was further reduced during the November sampling
period (Fig. 9H) at most offshore stations, although it remained abundant at
stations nearshore and stations in the Saginaw Bay interface waters. The
ecological affinities of this species are poorly known. It has been previously
reported from large alpine lakes in Europe, and it has previously been found in
limited abundance in Lake Superior and in northern Lake Huron (Schelske eJt. aL.,
1972, 1974; Lowe, 1976). While it has been reported as being a summer blooming
form in large European alpine lakes, the population levels achieved in southern
Lake Huron are unprecedented in our experience for the Great Lakes. More
recent data (Stoermer, unpublished) indicate that it has also become abundant
in Lake Michigan where it was previously unreported despite fairly intensive
sampling. The reasons for the apparent expansion of this particular species
are not apparent. However its seasonal pattern of occurrence would indicate
that it can tolerate very low levels of silicon and is one of the few diatom
species which can respond to loadings from Saginaw Bay during the summer and
early fall.
C_v_clotella comta
This species is a member of the classical oligotrophic CvcloteLla
association (Hutchinson, 1967). It is apparently tolerant of moderate levels
of eutrophication, but has been removed from areas of the Great Lakes which
have been excessively disturbed (Hohn, 1969; Duthie and Sreenivasa, 1971). In
southern Lake Huron scattered low level populations of this species are found
particularly in the northwestern sector of our sampling area during April
(Fig. 10A) and May (Fig. 10B). It is more abundant during the early June
sampling period (Fig. 10C) but high population levels are still largely
restricted to the western half of the sampling array. During late June
(Fig. 10D) populations are found at most stations sampled, and the species is
43
-------
ERST TflKflS
0
8-12 OCT 74
GOOERICH
HURON
R3FORMOS
ERST TRHHS
0
10-14 NOV 74
HURON
RSFORH03
Figure 8. (continued)
-------
EPST TflHflS
GODEBICH
0
28 RPR - 3 MflY 74
HURON CTCOHOB
EPST IfffB
GOOERICH
0
14-17 MflY 74
HURON CYCOHENS
Figure 9. Distribution of Cvclotella comensjs.
(continued)
-------
ERST TflHflS
GODERICH
0
U-8 JUN 74
HURON
CYCOMENS
WGOOEHICH
0
17-21 JUN 74
HURON
CYCOHEN3
Figure 9. (continued)
-------
EAST TAMRS
0
17-22 JUL 74
GOOERICH
HURON
CTCOHENS
0
26-31 RUG 74
ICH
HURON
CTCOMENS
Figure 9. (continued)
-------
EBST Tl
GOOERICH
0
8-12 OCT 74
HURON
CYCW0B
ERST TfiHfiS
0
10-14 NOV 74
ICH
HURON
CYCOHENS
Figure 9. (continued)
48
-------
GODERICH
0
28 RPR - 3 MRT 74
HURON
CTCOMTH
EflST THHHS
0
14-17 MflY 74
8 GOOERICH
HURON
CTCOMTfl
Figure 10. Distribution of Cvclotella
(continued)
-------
EflST TflHRS
0
4-8 JUN 74
HURON
CTCOMTR
EflST TflHflS
GOOERICH
0
17-21 JUN 74
HURON
Figure 10. (continued)
CTCOHTfl
50
-------
consistently absent only from stations in the southern sector of the Saginaw
Bay interface. Essentially the same situation prevailed during the July
sampling (Fig. 10E) but large populations were noted at nearshore stations
north of Tawas. The species generally increased in abundance by August
(Fig. 10F) and was absent only from a few stations in the Saginaw Bay interface
water and south along the Michigan coast. It remained abundant during October
(Fig. 10G) only to decline in abundance again in November (Fig. 10H).
rn.jctUKanj.ana
This species was originally described (Skvortzow, 1937) from the Great
Lakes and its recorded distribution is largely restricted to these bodies of
water and the inland lakes of Michigan. In southern Lake Huron only small
populations of these species were present during the May and June sampling
cruises (Fig. 11A-D). During July (Fig. 11E) it underwent an explosive
increase in abundance at stations in the western half of the area sampled,
although it was more abundant in stations in the main body of Lake Huron than
the Saginaw Bay interface waters. During August (Fig. 11F) this pattern was
reversed, with highest populations occurring in the eastern half of southern
Lake Huron, although appreciable populations were found at most stations
sampled. Population levels of this species began to decline during October
(Fig. 11G) and reached spring levels by the November cruise (Fig. 11H).
Cy_c,lote,Lla
This species is an important component of phytoplankton assemblages in
northern Lake Huron (Schelske £t. aL. , 1971*; Schelske £t. ai.. , 1976) and is
generally abundant in areas of the Great Lakes which have not undergone
significant eutrophication. In southern Lake Huron it was found at all
stations sampled during the April cruise (Fig. 12A) and was reduced in
abundance only at a few stations in the Saginaw Bay interface waters and
southerly along the Michigan coast. It was slightly more abundant during the
May cruise (Fig. 12B) but again its abundance was reduced at a few stations in
the Saginaw Bay interface. Its abundance continued to increase at most
stations sampled during the early (Fig. 12C) and late (Fig. 12D) June cruises.
During both of these cruises the abundance of this species was reduced at
stations in the Saginaw Bay interface waters, and at nearshore stations along
the Canadian shore. During the July cruise (Fig. 12E) population levels were
reduced at stations in the southerly half of the Saginaw Bay interface, and at
main lake stations in the southern half of Lake Huron, although it remained
abundant at stations in the northern and eastern sectors of the lake. Minimum
abundance of C_. ocellata was found during the August cruise (Fig. 12F) when it
was either absent or present in only very small numbers except at station 6 in
the far southeast sector of the lake. This isolated abundant occurrence may be
indicative of upwelling at this station, as C_. o_c_eJUat,a is one of the species
which has been noted to occur in large numbers at thermocline or
sub-thermocline depths. By October (Fig. 12G) this species was again present
at most stations sampled, with highest abundance at stations north of Saginaw
Bay. It was again present in November (Fig. 12H) although its distribution was
irregular, with the only trend being a tendency to decrease in abundance from
north to south in the area sampled.
51
-------
EflST TflHflS
0
26-31 RUG 74
s .
HURON
Figure 10. (continued)
ICH
CTCOMTfl
52
-------
EflST
GODERICH
0
8-12 OCT 74
HURON
CYCOMTH
bGODERICH
10-14 NOV 74
Figure 10
CTCOMTfl
-------
ERST TRMflS
0
28 RPR - 3 MflT 74
HURON
CYHICHIG
EflST TflHRS
GOOenlCH
0
14-17 MflY 74
HURON
CTMICHI6
Figure 11. Distribution of Cyclptella
michieaniana. (continued)
-------
EAST TflHRS
ItfGODERICH
0
4-8 JUN 74
HURON
CTMICHIG
EBST TflMHS
GOOERICH
0
17-21 JUN 74
HURON
CTMICHIG
Figure 11. .(continued)
55
-------
ERST TflHflS
COOEBICH
0
17-22 JUL 74
HURON
CYMICHIG
EBST Tl
IJCH
0
26-31 RUG 74
HURON
CYMICHIG
Figure 11. (continued)
56
-------
EflST TfiMflS
GOOERICH
0
8-12 OCT 74
'OUT HURON
CTMICHIG
EflST TfiMflS
ttGOQERICH
0
10-14 NOV 74
HURON
CTMICHIG
Figure 11. (continued)
57
-------
ERST TflHfiS
GOOERICH
0
28 RPR - 3 MflT 74
HURON
CYOCELLfl
EflST TflHflS
0
14-17 MflY 74
8GOOERICH
HURON
ctocaifl
Figure 12. Distribution of Cvclotella QC.ella.ta.
(continued;
-------
EfiST
0
4-8 JUN 74
tgGODERICH
HURON
CYOCELLfl
ERST TfiHflS
0
17-21 JUN 74
GooemcH
HURON
crocaifl
Figure 12. (continued)
59
-------
GODEHICH
0
17-22 JUL 74
HURON
CYOCELLfl
ERST TRHflS
0
26-31 RUG 74
GOOERICH
HURON
CTOCELLfl
Figure 12. (continued)
60
-------
EflST TfiMflS
0
8-12 OCT 74
GOOERICH
HURON
CYOCELLfl
EHST TflHflS
0
10-14 NOV 74
HURON
CTOCELLfl
Figure 12. (continued)
61
-------
Cyclotella operculata
Although this species is generally associated with oligotrophic
assemblages in the Great Lakes (Schelske et^ aJL. , 1976), its distribution is
highly erratic in southern Lake Huron. During April, May and June
(Figs. 13 A-D) only isolated populations were found at scattered stations
throughout the areas sampled. During July (Fig. 13E) it was consistently
present at the innermost stations in the Saginaw Bay interface, and isolated
populations were found in other areas of the lake. During August (Fig. 13F)
its abundance increased somewhat, although its pattern of occurence was still
extremely scattered. This species reached its maximum abundance during the
October cruise (Fig. 13G) when it was present in significant abundance at most
stations sampled, particularly in the northern part of the study area. It
however declined drastically by November (Fig. 13H) although populations were
still present at most stations sampled except those in the northeasterly sector
of the sampling area.
Cyclotella pseudostelligera
Unlike other members of this genus previously discussed, populations of
this species are usually restricted to significantly eutrophied or disturbed
areas. It is often a dominant member of the assemblage in eutrophic small
lakes and rivers (Belcher, Swale, and Heron, 1966; Hustedt, 1956). In the
Great Lakes large populations are generally restricted to harbor mouths and
eutrophied nearshore areas (Stoermer and Yang, 1970) although occasional
populations are found in offshore waters. In southern Lake Huron this species
was noted only in samples taken during the July, August and October cruises
(Figs. 14A-C). All occurrences noted were either at nearshore stations or
stations in the Saginaw Bay interface. It was most abundant during August
(Fig. 14B) when appreciable populations were found at several nearshore
stations in the far northwestern sector of the sampling area and at a nearshore
station along the Canadian coast.
Cyclotella stelligera
This species is a common offshore dominant in Great Lakes phytoplankton
assemblages. Although it responds strongly to experimental phosphorous
enrichment (Stoermer, Schelske, and Feldt, 1971) it is apparently intolerant of
highly eutrophied conditions in the natural environment, and tends to be
removed from regions of the Great Lakes which have undergone extensive
disturbance. It was present during the late April and May southern Lake Huron
cruises (Figs. 15A-B) generally in low abundance and no particular distribution
pattern was evident. Similar population densities were noted during the June
cruises (Figs. 15C-D), however reduced population densities were noted at
stations in the Saginaw Bay interface waters and stations along the Canadian
coast, particularly later in the month. During July (Fig. 15E) populations
increased markedly in the offshore waters of southern Lake Huron, although
populations remained at minimal levels at stations in the Saginaw Bay interface
waters. During August (Fig. 15H) highest population densities of this species
were found in the northern and eastern sectors of the sampling area, with
generally reduced populations at the rest of the stations. During October and
November (Fig. 15G-H) this species was at minimal levels compared to the
previous month, however low level populations were found at most stations
sampled.
62
-------
ERST TflHflS
GOOEBICH
0
28 RPR - 3 MflY 74
HURON
CYOPERCU
EflST TflHfiS
ttGOOEHICH
0
14-17 MflT 74
HURON
CYOPEHCU
Figure 13- Distribution of Cvclotella
operculatg. (continued)
63
-------
ERST TflMRS
GOOEHICH
0
4-8 JUN 74
HURON
CYOPERCU
EflST TflURS
GODERICH
Figure 13. (continued)
17-21 JUN 74
CYOPBWJ
-------
ERST TflHflS
0
17-22 JUL 74
IT HURON
ctorencu
EflST TflHflS
ttGOOERJCH
0
26-31 flUG 74
HURON
Figure 13. (continued)
CYorencu
65
-------
ERST Tl
GOOERICH
0
8-12 OCT 74
HURON
CYOPERCU
ERST
tit GOOERICH
0
10-14 NOV 74 N_
"HUHON
Figure 13. (continued)
CTWERCU
66
-------
EAST TAHflS
GOOERICH
0
17-22 JUL 74
HURON
CTPSTEa
EflST Tl
GOOERICH
0
26-31 RUG 74
HURON
CTPSTEU.
Figure 14. Distribution of Cvclotellg
ell ;lggra. (continued)
-------
ERST TftHflS
tt
GOOERICH
0
8-12 OCT 74
HURON
CTPSTELL
Figure
(continued)
Dlatoma, t.enue var . elongat_um
This species is widely distributed in the modern Great Lakes, generally
reaching its greatest abundance in areas that have undergone significant
eutrophication. It was present during all sampling periods in our study
(Fig. 16 A-H) but significant population densities were generally restricted to
stations in the Saginaw Bay interface waters and stations nearest shore. It
reached its greatest abundance during the November cruise (Fig. 16H) at the
innermost of the Saginaw Bay interface stations.
Dlatojna tenue var. nachvc epJnala
This entity is morphologically quite similar to D.. tenue. var. elongatuni
and in the Laurentian Great Lakes appears to have essentially similar
distributional affinities. In southern Lake Huron, however, it is both more
abundant and has a different temporal and spatial distribution than the
previously discussed taxon. It was found at most stations sampled during the
early May cruise (Fig. 17A), with maximum population densities occurring at
nearshore stations along the Michigan coast. By mid-May (Fig. 1?B) it had
become quite abundant at nearshore stations in the Saginaw Bay interface and
southward along the Michigan coast. During this cruise population densities
were generally elevated in nearshore stations, probably as a result of the
thermal bar condition. By early June (Fig. 17C) population densities had
begun to decline, although it remained relatively abundant at stations in the
southerly part of the Saginaw Bay interface and southward along the Michigan
coast. Populations apparently continued to decline and, by late June
(Fig. 17D), only scattered low level populations were found at the stations
sampled. This taxon was rare during the rest of the season with only a few
isolated populations being found during November (Fig. 1?E).
68
-------
gGOOGRICH
0
28 RPR - 3 MRY 74
HUMN
CYSTCLLI
0
14-17 MflT 74
HUMN
CTSTELU
Figure 15. Distribution of Cyclotella atelliggrg.
(continued)
69
-------
ERST TflHflS
0
4-8 JUN 74
GODERICH
'CRT HURON
CYSTELLI
ERST TRWfls J y
0
17-21 JUN 74
ORT HURON
Figure 15. (continued)
70
CYSTELLI
-------
EflST TfiHflS
0
17-22 JUL 74
GODERICH
IT HURON
CTSTELLI
EHST TflHflS
0
26-31 flUG 74
HURON
Figure 15. (continued)
ilCH
CY3TELLI
71
-------
GODERICH
0
8-12 OCT 74
HURON
CTSTELLI
EflST TflHfiS
GOOERICH
0
10-14 NOV 74
i* ^
RT HURON
Figure 15. (continued)
CTSTELL;
72
-------
EflST TflHflS}j J
&GOOERICH
0
28 RPR - 3 MflT 74
HURON
DITENUVE
ERST TflHflS
GODERICH
0
1U-17 MflT 74
HURON
DITENUVE
Figure 16. Distribution of Diatoma tenue var.
. (continued)
73
-------
EflST THHHS
ttGODEHICH
0
4-8 JUN 74
HURON
OITENUVE
EflST TflHflS
GOOEfilCH
17-21 JUN 74
HURON
DITENUVE
Figure 16. (continued)
-------
ERST TRHflS
toGODEHJCH
0
17-22 JUL 74
HURON
DJTENUVE
EflST TflHflS
GOOERICH
0
26-31 flUG 74
i, ^
HURON
Figure 16. (continued)
DITENUVE
75
-------
EflST TRHflS
GOOERICH
0
8-12 OCT 74
HURON
DITENUVE
EflST TflHflS
0
10-14 NOV 74
GODERICH
Figure 16.
PORT HURON
(continued)
OITENUVE
76
-------
EflST TflHflS
0
28 RPR - 3 MflT 74
GOOERICH
IT HURON
DITENUVP
0
14-17 MflY 74
HURON
GODERICH
DJTENUVP
Figure 17. Distribution of £ia£flHa JiSDJiS var
Dachvcephala. (continued)
77
-------
ERST TflHflS
4-8 JUN 74
ttGOOEfilCH
HURON
OITENUVP
EflST TflHflS
0
17-21 JUN 74
'ORT HURON
DITENUVP
Figure 17. (continued)
78
-------
EflST TflHflS
tt GODERICH
0
10-14 NOV 74
ORT HURON
DITENUVP
Figure 17. (continued)
FragJLlaria capucina
Although this species is most commonly reported from small eutrophic
lakes, it is one of the forms which can successfully invade portions of the
Great Lakes which become significantly eutrophied (Hohn, 1969) and may become a
dominant element of the flora in disturbed parts of the system (Stoermer and
Yang, 1970). It is surprisingly abundant in southern Lake Huron. During early
May (Fig. 18A) small populations were found in the Saginaw Bay interface waters
and at some localities along both the Michigan and Canadian coast. In mid-May
(Fig. 18B) it had become very abundant at stations in the southerly sector of
the Saginaw Bay interface and southward along the Michigan coast. Small
populations were also found at most shoreward stations sampled. It occurs in
the nearshore zone at this time with St_ep_hano-dlscus binderanus. where their
distribution is restricted by the spring thermal bar. During June (Fig. 18C-D)
it was abundant at stations in the Saginaw Bay interface and stations running
southeastward from this area. During late June (Fig. 18D) significant
populations were also found at stations along the Canadian coast. During July
and August (Fig. 18E-F) the species declined in abundance although occasional
populations were still found in the Saginaw Bay interface and at stations along
the Canadian coast. It again increased in abundance during the fall cruises
(Fig. 18G-H) but population densities did not approach those found during the
spring bloom, and occurrences were restricted to the Saginaw Bay interface
waters and a few stations southward along the Michigan coast.
79
-------
ERST TRHRS
GOOERICH
0
28 RPR - 3 MflY 74
HURON
FRWOCI
ESWT
0
14-17 MflY 74
HUROH
FfWWCI
Figure 18. Distribution of Fragilaria caoucina.
(continued)
-------
DOT TOWS
0
4-8 JUN 74
GODERICH
HURON
FRCflPUCI
EWTTflNflS
0
17-21 JUN 74
HURON
Figure 18. (continued)
8l
jttGOOCRICH
FBCflPUCI
-------
ERST TBWflS
0
17-22 JUL 74
HURON
FRCWUCI
GOOEBICH
0
26-31 RUG 74
HURON
FRCflPUCJ
Figure 18. (continued)
82
-------
ERST TflHflS
0
8-12 OCT 74
GOOERICH
HURON
FflCRPUCI
ERST TflHflS
10-14 NOV 74
GOOERICH
Figure 18. (continued)
FHCRPOCI
-------
Fraellaria cr_Qt_onensls_
This species is one of the most widely distributed and apparently
eurytopic of all freshwater planktonic diatoms. It is common throughout the
Great Lakes system and apparently tolerant of the full range of conditions
found within the system. It responds strongly to experimental phosphorus
enrichment (Stoermer, Ladewski and Schelske, 1978) but significant populations
may be found in areas of the Great Lakes which have low ambient nutrient
concentrations. It was present at most stations sampled during the early May
cruise (Fig. 19A) with highest population densities occurring at stations along
the Michigan coast. By mid-May (Fig. 19B) populations were highest at stations
in the Saginaw Bay interface and nearshore stations around the southern basin.
The increase at nearshore stations appeared to be associated with the
development of the spring thermal bar. In early June (Fig. 19C) population
levels were somewhat reduced, with highest densities occurring at scattered
stations in the Saginaw Bay interface. In late June (Fig. 19D) this species
bloomed at stations in the southerly portion of the Saginaw Bay interface, and
it was present at most stations sampled. These populations had apparently
collapsed by the time the raid-July samples (Fig. 19E) were taken and highest
population densities were found in the extreme southern portion of the lake.
Seasonal minimal abundance of this species occurred during August (Fig. 19F)
when only isolated low level populations were found. It increased in abundance
again during October (Fig. 19G) when highest population densities were again
found in the Saginaw Bay interface waters. Similar population densities were
found during the November cruise (Fig. 19H) when this species was most abundant
in the Saginaw Bay interface waters southward along the Michigan coast and at
certain stations along the Canadian coast.
FragilarJLa Pinnata
This species is primarily benthic in habitat preference and, although
occasional specimens may be found in plankton collections from the Great Lakes,
it is rarely a dominant element in phytoplankton assemblages. Its distribution
appears to be controlled by both nutrient availability and the availability of
suitable benthic substrates. For instance, in Lake Michigan (Stoermer and
Yang, 1970), its distribution is largely restricted to stations along the
western shore. It appears to be more abundant in southern Lake Huron than in
other areas of the Great Lakes so far studied. In May (Fig. 20A-B) occasional
populations were noted, particularly at nearshore stations and stations in the
Saginaw Bay interface. During early June (Fig. 20C) this species was not
abundant but did occur at nearshore localities in Saginaw Bay and north and
south along the Michigan coast. Populations were at very low levels during the
mid-June and July cruises (Fig. 20D-E). Abundance increased somewhat during
August (Fig. 20F) and it had become quite abundant by the time the October
(Fig. 20G) samples were taken, with appreciable populations present in the
Saginaw Bay interface stations and at most nearshore stations all along the
Michigan coast. Population levels of this species were generally reduced
during the November cruise (Fig. 20H) at stations south of Saginaw Bay,
although it reached seasonal maxima at stations along the Michigan coast north
of Tawas.
-------
EflST TRMflS
GOOQUCH
0
28 RPR - 3 MflT 74
ORT MUBON
FRCROTON
ERST THHRS
BGOOOUCH
0
14-17 MflT 74
HURON
FBOWTON
Figure 19- Distribution of Fragilaria
crotonenais. (continued)
-------
EflST TflHflS
0
4-8 JUN 74
GOOERICH
HURON
FRCfiOTON
ERST TflHflS
GOOERICH
0
17-21 JUN 74
IT HURON
FRCROTON
Figure 19. (continued)
86
-------
8GODERICH
0
17-22 JUL 74
HURON
FRCHOTON
ERST TflHflS
8GOOERICH
0
26-31 RUG 74
HURON
Figure 19. (continued)
87
FRCROTON
-------
ERST TRHRS
0
8-12 OCT 74
8OTOERICH
HURON
FfWWTON
ERST TRHRS
GOOERICH
0
10-14 NOV 74
HURON
Figure 19. (continued)
FRCflOTON
-------
EflST TflHflS
0
28 RPR - 3 MflY 74
SGOOERICH
HURON
FRPINNflT
ERST TRNRS
GOOERICH
0
14-17 MflY 74
HURON
FflPINNRT
Figure 20. Distribution of Fraeilaria pj.nna.ta.
(continued)
-------
ERST TfittfiS
0
4-8 JUN 74
GOOERICH
HURON
FRPINNRT
ERST TflHRS
toGOOERICH
0
17-21 JUN 74
HURON
Figure 20. (continued)
FRPINNRT
90
-------
ERST TflHflS
GOOERICH
0
17-22 JUL 74
HURON
FWINNflT
ERST TflHfiS
GOOERICH
HURON
0
26-31 RUG 74
Figure 20. (continued)
91
FRPINNHT
-------
EflST Tl
WGOOERICH
0
10-1U NOV 74
HURON
Figure 20. (continued)
FflPINNflT
92
-------
granulata
This species generally reaches its highest abundance in small eutrophic
lakes where it often forms sizeable early summer and early fall blooms. It is
a common element of phytoplankton assemblages of shallow eutrophied areas in
the Laurentian Great Lakes, but rarely, if ever, reaches high population
densities in the offshore waters of the lakes other than Lake Erie. It was
first noted during the early May sampling cruise at two nearshore stations
along the Michigan coast (Fig. 21A). By mid-May (Fig. 21B) it was abundant at
certain stations at the Saginaw Bay interface waters, and low level populations
were also noted at nearshore stations along the Canadian coast. Population
levels of M,. granulata declined during June (Fig. 21C-D) although scattered
occurrences were noted. This trend continued into July and August (Fig. 21E-F)
with only occasional populations found at nearshore stations. During October
(Fig. 21G) the abundance of this species again increased, and sizeable
populations were noted at stations in the southerly sector of the Saginaw Bay
interface and at most nearshore stations sampled. Maximum population levels
were noted in November (Fig. 21H) when it was abundant at stations in the
Saginaw Bay interface and present at several stations in the southern part of
main Lake Huron, including some stations near mid-lake. Two growth forms of
this taxon were noted during this study, a very coarsely punctate type with
large spines and a finely punctate form with short spines.
MeJosira, islan_dlca
This species is a common cold season dominant in boreal and alpine lakes
worldwide. It is common throughout the Great Lakes system and appears to be
favored by moderate levels of nutrient increase although it tends to disappear
in areas which are grossly perturbed. It was present at most stations sampled
during early May with greatest abundance at stations along the Canadian
shoreline. By mid-May populations had somewhat increased and the species was
again exceptionally abundant at stations along the Canadian coast north and
south of Goderich (Fig. 22A-B). Population levels generally declined during
June (Fig. 22C-D) and only occasional low-level occurrences were noted during
the rest of the sampling season (Fig. 22E-G).
NJLtzsohia acicularis
The distribution and ecological affinities of this species are not well
known, and it is rarely reported from plankton communities. It is widely
distributed in the Laurentian Great Lakes and is a common minor component of
phytoplankton assemblages in those areas which have been studied in detail. It
may be much more abundant than generally realized because cells may be confused
with members of the genus Svnedra if observed in wet mounts. Rather uniform
populations of this species were present at most stations sampled during May
(Fig. 23A-B). In early June (Fig. 23C) distribution of this species was more
erratic, and although it was still abundant at many stations, populations were
significantly reduced in the Saginaw Bay interface waters and at certain
stations offshore. Populations continued to decline in late June (Fig. 23D)
although the species remained abundant at nearshore stations north of Tawas
and, to a lesser extent, at stations south of Saginaw Bay along both the U.S.
and Canadian coasts. Population levels were minimal during July and August
(Fig. 23E-F) but the species became more abundant again in October and November
(Fig. 23G-H) particularly at stations in the Saginaw Bay interface waters and
nearshore stations.
93
-------
EflST TflHflS
28 RPR - 3 MflT 74
GOOERICH
IT HURON
MEGRflNUL
EflST Tl
0
14-17 MflY 74
GOOERICH
HURON
MEGRflNUL
Figure 21. Distribution of Melosira granulata.
(continued)
-------
EflST TflHflS
GOOERICH
4-8 JUN 74
HURON
MEGRRNUL
EflST TRMflS
BGOOERICH
HURON
0
17-21 JUN 74
Figure 21. (continued)
95
MEGRANUL
-------
EflST TflMflS
&GODEHICH
0
17-22 JUL 74
HURON
HEGRflNUL
EflST TfiHfiS
JtGODEBICH
0
26-31 RUG 74
HURON
HEGfWNUL
Figure 21. (continued)
96
-------
EflST TfiHRS
0
10-14 NOV 74
HURON
MEGtWWJL
Figure 21. (continued)
97
-------
EflST TfiHflS
0
28 RPR - 3 MRY 74
GOOERICH
ORT HURON
MEISLflNO
ERST TflMRS
14-17 MflT 74
HURON
MEISLflNO
Figure 22. Distribution of Melosira islandjlcgi.
(continued)
98
-------
EflST TflMflS J/
4-8 JUN 74
BGOOERICH
HURON
MEISLflNO
ERST TflMflS
GOOERICH
0
17-21 JUN 74
i, ^-
HUROK
Figure 22. (continued)
NEISLflNO
99
-------
EAST TflHfiS
0
26-31 flUG 74
8GOOOUCH
HURON
MEISLflND
ERST TfiHflS
ttGOOERICH
0
8-12 OCT 74
HURON
Figure 22. (continued)
100
MEISLflNO
-------
ERST TRUAS
tfGODQUCH
0
10-14 NOV 74
HEISLRND
Figure 22.
Nitzschia dissipata
This is another member of the genus that is unusually widely distributed
and abundant in plankton collections from the Great Lakes. In southern Lake
Huron maximum population densities were reached during May (Fig. 24A-B) when
this taxon was present at most stations sampled. During June (Fig. 24C-D),
population levels declined, particularly at stations in the Saginaw Bay
interface waters. Minimum population levels were reached during July
(Fig. 24E), when the species was noted at only a few nearshore stations. It
increased again slightly in August (Fig. 24F) when sizeable populations were
noted at several inshore stations along the Michigan and Canadian coasts of
southern Lake Huron. The taxon was more generally distributed in October
(Fig. 24G) although population densities were somewhat smaller than in the
previous month. Population densities declined again in November (Fig. 24H)
when only small populations were found at scattered stations. Unlike the
previous month, during November maximum population densities were found at
stations in the Saginaw Bay interface waters.
Rhizosolenia eriensis
This species was originally described from the Laurentian Great Lakes and
is one of the characteristic offshore dominants. It is generally abundant in
the offshore plankton of the upper lakes in winter and early spring, but is
apparently excluded from areas which have undergone extreme eutrophication
(Hohn, 1969). It was present at all stations sampled during May (Fig. 25A-B)
and increased in abundance during the course of the month. The increase in
101
-------
CflST
28 RPR - 3 MflY 74
HURON
NIflCICUL
ERST TAHRS
0
14-17 MflY 74
GOOBRICH
HURON
NlflCICUL
Figure 23- Distribution of Ni
acicularis. (continued)
102
-------
EflST TflHflS
WGOOOUCH
0
17-21 JUN 74
HURON
Figure 23. (continued)
103
HWCJCUL
-------
ERST TflNRS
GOKRICH
17-22 JUL 74
HUMN
NlflCICUL
BOT TflHBS
26-31 flUG 74
\
HURON
Figure 23. (continued)
MIACIOL
104
-------
8-12 OCT 74
ttGOOOUCH
HURON
NIBCJCUL
EBST
10-14 NOV 74
HURON
NJflCJCU.
Figure 23. (continued)
105
-------
EBST TfWRS
28 RPR - 3 MflY 74
RGOOOUCH
HUMW
Nioissir
ERST TWRS
GQOEIUCH
0
14-17 MflY 74
HURON
N10IS9IP
Figure 24. Distribution of Nitzschia
dissjpata. (continued)
106
-------
EAST TAWS
COOQUOt
0
U-8 JUN 74
tuat
Nioissir
CAST TAHAS
0
17-21 JUN 74
_ ptGOOOIICH
HUNM
HlOlSSIf
Figure 24. (continued)
10 T
-------
EflST TflMBS
GOOBMCH
17-22 JUL 74
HURON
MJOISSIP
HUTMH
26-31 flUG 74
Figure 2*L (continued)
108
wojssir
-------
BUT TWRS
8-12 OCT 74
BCOOCBICM
HURON
NIOISSir
oar TAWS
coomcH
10-1U NOV 74
HURON
NI01S9IT
Figure 24. (continued)
109
-------
EflST TfflJflS fll J
0
28 RPR - 3 MRT 74
IT HURON
RHCRIENS
EflST T
0
14-17 MflT 74
GODEftlCH
HURON
RHERIENS
Figure 25- Distribution of RhizoaplenjLa erjensis.
(continued)
110
-------
population density continued during June (Fig. 25C-D) at offshore stations, but
it began to decline in abundance at stations in the Saginaw Bay interface
waters, and was absent from several stations in this area by late June.
Populations collapsed during July (Fig. 25E) and remained at low levels during
August (Fig. 25F). Although population densities were low, this species
occurred at a number of stations in the Saginaw Bay interface waters and
southward along the Michigan coast in October (Fig. 25G) and appeared to spread
southward into the offshore waters of Lake .Huron during November (Fig. 25H).
Rhizosolenia gracilis
This species was also originally described from the Laurentian Great Lakes
and appears to have growth requirements similar to those of R.. eriensis. It,
however, appears to be somewhat more tolerant of eutrophic conditions and is
more often reported from small eutrophic lakes. It was present at all stations
sampled during May (Fig. 26A-B) and increased during the course of the month,
particularly at stations in the Saginaw Bay interface waters and nearshore
stations along both the Michigan and Canadian coasts. The trend toward
increased abundance continued at offshore stations sampled during June
(Fig. 26C-D), although it was reduced in abundance at stations in the Saginaw
Bay interface waters early in the month and absent from a few of these stations
by the late June sampling cruise. Population densities declined drastically
during July (Fig. 26E) and the species was absent from all except a few
stations in the Saginaw Bay interface waters and along the Canadian coast
during the August (Fig. 26F) sampling period. Small populations were
maintained at stations in the Saginaw Bay interface during October and November
(Fig. 26G-H) and occasional isolated occurrences were noted at offshore
stations.
Stephanodiscus alpinus
This species is a common minor component of phytoplankton assemblages in
the upper Great Lakes. It appears to be favored by low levels of
eutrophication but is not tolerant of extreme levels of perturbation. Although
it was present at many stations sampled during early May (Fig. 27A) its
distribution pattern was dominated by a massive bloom at station 57 near Port
Albert. It was also present at most stations sampled during mid-May (Fig. 27B)
with highest population densities occurring in Saginaw Bay interface waters and
particularly at nearshore stations along the Canadian coast. Population
densities declined during June (Fig. 27C-D) but it was noted at a few scattered
stations. Only isolated occurrences were noted during July (Fig. 27E) and
August (Fig. 27F). It increased somewhat during October (Fig. 27G) and
November (Fig. 27H) with most occurrences in the Saginaw Bay interface waters
and at stations southward along the Michigan coast.
Stephanodiscus binderanus
This species was apparently not a part of the indigenous phytoplankton
flora of the Laurentian Great Lakes, but has been introduced following
eutrophication and is now a dominant element of phytoplankton assemblages in
highly disturbed areas (Hohn, 1969; Stoermer and Yang, 1969). It apparently
has a restricted temperature tolerance (Stoermer and Ladewski, 1976) and
usually reaches its maximum abundance during the spring thermal bar period
(Nalewajko, 1967; Loriface and Munawar, 1974). It may reach very high
111
-------
rasr
0
4-8 JUN 74
GOOERICM
HURON
RHER1ENS
0
17-21 JUN 74
Figure 25.
a HURON
(continued)
ICH
RHERIENS
112
-------
EflST TflHflS
0
17-22 JUL 74
ttOOOERJCH
IT HURON
RHER1ENS
EAST TBWRS
ttCOOERICH
26-31 flUG 74
HURON
Figure 25. (continued)
flHERIENS
113
-------
gGOOOUCH
0
8-12 OCT 74
IT HURON
RHECUENS
ERST TBWRS
Figure 25. (continued)
10-14 NOV 7U
-------
8GOOERICH
0
28 RPR - 3 MflT 74
ORT HURON
RHGRflCIL
EflST Ti
0
14-17 MflT 74
ICH
IT HUBON
nHGRRCIL
Figure 26. Distribution of RhizQsolenj.a gracilis.
(continued)
L15
-------
EflST TflHflS
0
17-21 JUN 74
Fom HURON
Figure 26. (continued)
116
iDEfilCH
RMGRRCIL
-------
CAST TflUflS
17-22 JUL 74
EflST TRWflS
26-31 RUG 74
s.
HURON
Figure 26. (continued)
117
RHGRflCIL
-------
EflST TRHRS
ttGOOERICH
0
8-12 OCT 74
HURON
RHGRRCIL
EHST THWBS
COOERICH
0
10-14 NOV 74
'OKI HURON
RHGRRCIL
Figure 26. (continued)
118
-------
EAST TflHflS
ERST TflHflS
28 flPR - 3 MflT 74
0
14-17 MflT 74
POUT HURON
STflLfJNU
Figure 27.
STflLPINU
Distribution of Stephanodiscus
aloinus. (continued)
119
-------
COOERICH
0
4-8 JUN 74
HURON
STHLPINU
EfiST TflHftS
8GOOERICH
0
17-21 JUN 74
HURON
Figure 27. (continued)
STflLPINU
120
-------
EflST TflMflS
GOOERICH
17-22 JUL 74
'ORT HURON
STflLPINU
ERST TflMflS
1» GOOERICH
0
26-31 RUG 74
HURON
STflLPINU
Figure 27. (continued)
121
-------
EflST THHflS
8GOOER1CH
0
8-12 OCT
HURON
STRLPINU
ERST TRWRS
GODERICH
0
10-14 NOV 74
HURON
STHLTINU
Figure 2?. (continued)
122
-------
population densities during the spring bloom, and can become a serious nuisance
at municipal filtration plants (Vaughn, 1961). In the upper Great Lakes its
distribution is largely restricted to eutrophied bays and nearshore areas, but
it is abundant in the offshore waters of Lake Erie (Hohn, 1969) and Lake
Ontario (Stoermer .et. .aj,. , 1974) as a result of advanced eutrophication. In
southern Lake Huron only a few occurrences were noted in the early May samples
(Fig. 28A), but it was abundant in samples from the Saginaw Bay interface
waters taken during mid-May (Fig. 28B) . As is characteristic of this species,
maximum population densities were found at nearshore stations. Population
densities had been markedly reduced by the time the early June samples were
taken (Fig. 28C) , and by late June (Fig. 28D), only a few small isolated
populations were found. Although a few specimens were noted in fall samples,
this species was never a significant part of the flora during the rest of the
study.
Stepfcanod^scus hant^schii
This species is a common element of phytoplankton assemblages in
mesotrophic to eutrophic lakes. It is apparently able to respond rapidly to
increased nutrient supply and often forms blooms in areas which are
significantly enriched. It was present in most of our early May samples from
southern LaKe Huron but reached very high population densities only at station
57 (Fig. 29A). During mid-May (Fig. 29B) very high population densities were
again noted at stations along the Canadian coast and it remained fairly
abundant at stations in the Saginaw Bay interface waters and at other nearshore
stations, although population densities were somewhat reduced at offshore
stations. Populations of this species collapsed during June (Fig. 29C-D) and
although isolated specimens were found in a few samples, it was not found in
abundance during the rest of the study.
This species is a common element of phytoplankton assemblages in
mesotrophic to eutrophic lakes, and often forms winter blooms in large
eutrophic lakes (Huber-Pestalozzi , 19^2). This taxon is often found in
collections from the upper Great Lakes but is generally abundant only in areas
which receive elevated nutrient input. Like gtej^han.gdj^cija .lantzschii it
responds rapidly to nutrient enrichment (Stoermer, Ladewski, and Schelske,
1978) but is not tolerant of gross pollution. During early May (Fig. 30A) it
was present at most stations sampled in southern Lake Huron, but markedly more
abundant at nearshore stations along the Canadian coast. During mid-May
(Fig. 30B) high population densities of this species were maintained at
nearshore stations along the Canadian coast, but had begun to decline
particularly at stations in the Saginaw Bay interface waters and nearshore
stations along the Michigan coast. Population densities declined and the
distribution of the species became more erratic during June (Figs. 30C-D);
populations had collapsed by the time the mid-July samples were taken
(Fig. 30E). Only a few isolated examples of this species were found in samples
taken during August (Fig. 30F) but it became more abundant and widely
distributed in the October and November samples (Figs. 30G-H) , although it
never approached spring population densities.
123
-------
28 RPR - 3 MflT 74
GOOERICH
0
14-17 MflY 74
>, _
RT HURON STBINOER
Figure 28. Distribution of Stephanodiscus
binderanus. (continued)
-------
EflST TflWRS
0
4-8 JUN 74
GODERICH
IT HURON
STBJNDER
EflST TflWflS
0
17-21 JUN 74
Figure 28.
'ORT HURON
(continued)
GOOERICH
STBINDEfl
125
-------
EflST TflHflS
« CODERICH
0
17-22 JUL 74
'ORT HURON
STBINOER
EflST TfiWflS
CODER ICH
0
8-12 OCT 74
STBINOER
Figure 28. (continued)
126
-------
EflST IflWflS
10-14 NOV 74
Figure 28.
'ORT HURON
(continued)
S7BJNDER
Stephanodiscus subtilis
This species is rarely reported in the literature and its ecological
affinities are poorly known. It is abundant and widely distributed in Lake
Ontario (Stoermer _ejt _al_. , 1974). In Lake Michigan (Stoermer and Yang, 1970)
its distribution appears to be restricted almost entirely to harbor entrances
and eutrophied nearshore areas. Its distribution in southern Lake Huron is
highly unusual in that although it was present during all sampling cruises
(Figs. 31A-H), its distribution was almost entirely restricted to nearshore
stations along the Canadian coast. These populations may, in fact, be derived
from riverine habitats. The only exceptions to this were a few very small
populations noted at stations of the Saginaw Bay interface water collected
during late June and November.
Synedra filiformis
This species is one of the characteristic forms of the offshore
phytoplankton flora of the upper Great Lakes. In southern Lake Huron, large
and remarkably uniform populations were found at all stations sampled during
May (Figs. 32A-B). Populations remained high at offshore stations sampled
during June (Figs. 32C-D); however, population densities were reduced at
stations sampled in the Saginaw Bay interface waters during early June. By
late June, this species was absent from several stations in the Saginaw Bay
interface waters and south along the Michigan coast. Abundance of this species
was at a minimum during the July sampling period (Fig. 32E), but by August
(Fig. 32F) it had again become abundant at stations in the northerly sector
127
-------
ERST TflMflS
OHT HURON STHflNTZS
EflST TflHflS '
28 RPR - 3 MflY 74
ICH
0
14-17 MflY 74
Figure 29. Distribution of Stephanodiscus
hantzschii. (continued)
HURON
STHflNTZS
-------
EflST TflHflS
ttGOOERICH
0
4-8 JUN 74
HURON
STKSNTZS
EflST TflHflS
ttGOOERICH
0
17-21 JUN 74
>, .
HURON
Figure 29. (continued)
STHHKTZS
129
-------
ERST TANAS
GOOERICH
0
17-22 JUL 74
HURON
STHAHTZS
»GOOERICH
0
26-31 RUG 74
\.
HURON
Figure 29. (continued)
STHANTZS
130
-------
EAST TANAS
0
8-12 OCT 74
EAST TANAS
0
10-1U NOV 74
Figure 29,
on HURON
(continued)
STMRKTIS
131
-------
28 RPR - 3 MflY 74
0
14-17 MflT 74
STMINUTU
Figure 30. Distribution of StephanodisGus minutus.
(continued)
132
-------
EflST TRHflS
0
4-8 JUN 74
teGODERICH
HURON
STMINUTU
0
17-21 JUN 74
HURON
Figure 30. (continued)
teGOOERICH
STMINUTU
133
-------
0
17-22 JUL 74
ttGOOERICH
HURON
STMINUTU
EflST TflHflS
GOOERICH
0
26-31 RUG 74
Figure 30.
HURON
(continued)
STMINUTU
134
-------
EHST TflHfiS
WGODERICH
0
8-12 OCT 74
HURON
STMJNUTU
0
10-14 NOV 74
HURON
Figure 30. (continued)
STMINUTU
135
-------
ERST THWflS
28 flPR - 3 MRY 74
GOOERICH
HURON
STSUBTJL
EHST THHflS
0
14-17 MRY 74
ICH
HURON
STSUBTIL
Figure 31. Distribution of Steohanodiscus
aubtilis. (continued)
136
-------
EflST TflHflS
0
4-8 JUN 74
IICH
HURON
STSUBTIL
ICH
0
17-21 JUN 74
IT HURON
STSUBTIL
Figure 31. (continued)
137
-------
ERST TflMflS
GOOERICH
0
17-22 JUL 74
HURON
STSUBTIL
EflST TflMflS
ICH
0
26-31 RUG 74
>.
HUnON
Figure 31. (continued)
STSUBTIL
138
-------
ERST TflHRS
GODEHICH
0
8-12 OCT 74
HURON
STSUBTIL
ERST TflHRS
gGOOERICH
0
10-14 NOV 74
HURON
Figure 31. (continued)
STSUBTIL
139
-------
EAST TRUflS
EflST T!
0
14-17 MflY 74
GODERICH
28 flPR - 3 MflY 74
STFILIFO
RT HUflON
SYFILIFQ
Figure 32. Distribution of Svnedra f j-lj-formis.
(continued)
-------
ERST TflHflS
0
17-21 JUN 74
ICH
HURON
Figure 32. (continued)
SYFILIFO
141
-------
ERST TflHflS
GOOERICH
0
17-22 JUL 74
IT HURON
STFILJFO
EflST Ti
0
26-31 RUG 74
|»GOOERICH
IT HURON
SYFILIFO
Figure 32. (continued)
142
-------
of the Saginaw Bay interface waters. It remained abundant at some stations in
the Saginaw Bay interface waters during October (Fig. 32G) and appeared to
spread southward at stations along the Michigan coast. This trend continued
during November (Fig. 32H) and there was a small increase in population
densities of this species at offshore stations although it did not approach
abundances present in the spring samples.
gynedra os^enfeldii
Although this colonial species is not as abundant as gynedra
its areal and temporal distribution in southern Lake Huron are quite similar.
It was present at most stations sampled during May (Figs. 33A-B) , with highest
population densities occurring in stations in the northerly sector of the
Saginaw Bay interface waters. During June (Figs. 33C-D), populations began to
decline, particularly at stations in the Saginaw Bay interface, and by late
June it was absent from several stations in this area and southward along the
Michigan coast. Population densities of this species remained low during the
rest of the study (Fig. 33E-H), with most occurrences noted in the Saginaw Bay
interface waters and at stations southerly along the Michigan coast.
fenes^ra.ta
This species is one of the eurytopic plankton dominants which are common
to abundant throughout the Great Lakes system. In southern Lake Huron, it was
present in all samples taken during early May (Fig. 3^A), and population levels
increased by the time the mid-May samples were taken (Fig. 34B) . Populations
remained high in early June (Fig. 3^C) but began to decline in late June
(Fig. 3^D) and had collapsed by the time July (Fig. 34E) samples were taken.
Population levels were at a minimum during the August sampling cruise
(Fig. 34F) except at station 6 where this species was fairly abundant, perhaps
as a result of upwelling. There was a slight increase in abundance of this
species during October and November (Figs. 3^G-H) , although its abundance did
not approach spring levels.
TabeIIar4a flocculosa var. 14-"ear.4s
This species was present at most stations sampled during early May
(Fig. 35A) and peak population densities were found at nearshore stations north
of Saginaw Bay. Increased abundance was noted in the mid-May samples
(Fig. 35B) and peak abundance occurred during June (Figs. 35C-D). As was the
case with £. fenes_trata abundance of this species declined during July and
August (Figs. 35E-F) , but unlike that species occasional abundant occurrences
were noted, particularly at nearshore stations. Population densities increased
during October and November (Fig. 35G-H) particularly at stations in the
Saginaw Bay interface waters and southward along the Michigan coast. Fall
abundance of this species however did not approach the levels found in the
spring samples.
-------
0
8-12 OCT 74
btOOOERICH
HURON
STFILIFO
EflST THMflS&J j
UtGOOERICH
0
10-14 NOV 74
Figure 32. (continued)
'ORT HURON
SYFILIFO
-------
28 flPR - 3 MflT 74
ttGOOERICH
0
14-17 MflT 74
HURON
STOSTQT
Figure 33. Distribution of Svnedra ostenfeldii.
(continued)
-------
0
4-8 JUN 74
GOOOUCH
HURON
STOSTENF
EBST Tl
BGOOOUCH
0
17-21 JUN 74
SllftfltW
Figure 33. (continued)
146
-------
DOT TflHBS
8GOOERICH
17-22 JUL 74
HURON
STOSTENF
EAST TflHflS
ttGOOERICH
0
26-31 RUG 74
HURON
Figure 33- (continued)
STOSTOF
147
-------
ttGOOEJUCH
8-12 OCT 74
HURON
SYOSTENF
EflST TflHflS
GOOERICH
0
10-14 NOV 74
HURON
STOSTEWF
Figure 33. (continued)
-------
DOT
0
28 RPR - 3 MflY 7U
EBST Tl
8GOOEBIW
14-17 MflT 74
HURON
TflFQCST
Figure 34. Distribution of Tabellaria fgDe.3tra.ta.
(continued)
149
-------
4-8 JUN 74
ttGOOERICH
HURON
TBFQeST
ERST TflHRS
17-21 JUN 74
\
HURON
Figure 34. (continued)
HCH
150
-------
0
17-22 JUL 74
HURON
TflFENEST
toCOOERICH
26-31 RUG 74
HURON
Figure 34. (continued)
151
TflFEHEST
-------
ERST TRHRS
eOOOUOl
0
8-12 OCT 74
HURON
TflFENCST
ERST TRHRS
GOOERICH
10-14 NOV 74
»,
HURON
Figure 34. (continued)
TRFOCST
152
-------
ERST TOURS
0
28 flPR - 3 MflY 74
bCOOQMCH
HURON
TflflOCVL
GOOCRICH
0
14-17 MflY 74
HURON
TflfLOCVl.
Figure 35. Distribution of Tab_ellptrj.a flocculosa
var. Ij.pe^ri3. (continued)
153
-------
ERST
I CM
17-21 JUN 74 k_
"HURON
Figure 35. (continued)
TflflOCVL
-------
ERST TOURS
cooeniCH
0
17-22 JUL 74
HURON
Tffl-OCVL
RGOOEDICH
0
26-31 RUG 74
Figure 35.
HURON
(continued)
TflftOCVL
155
-------
ERST TAHR3
8GOOERICH
0
8-12 OCT 74
HURON
7BH.OCVL
EBST TflHRS
ttCOOEBJCH
0
10-14 NOV 74
\^
HURON
Figure 35. (continued)
TflFLOCVL
156
-------
Chlorophyta
The green algal flora of southern Lake Huron is more extensive and diverse
than most regions of the upper Great Lakes and appears to be dominated by
species which originate in Saginaw Bay. Green algae are relatively rare in
samples taken in early May (Fig. 36A) but fairly high population densities are
present in mid-May samples (Fig. 36B) from the Saginaw Bay interface waters and
stations southward along the Michigan coast. The number of green algae present
in samples from the Saginaw Bay interface further increases in early June
(Fig. 36C) and these populations appear to encroach further into the offshore
waters from Lake Huron. Abundance of green algae decreases slightly in late
June (Fig. 36D) but appreciable populations were still present in the Saginaw
Bay interface waters and southward along the Michigan coast. A large increase
from this group is noted in the July samples (Fig. 36E) with maximum abundance
in the southern sector of the Saginaw Bay interface waters. In August
(Fig. 36F), unlike the previous month, maximum green algal abundance is found
in stations in the northerly sector of the Saginaw Bay interface waters. Also
during this month, this group reaches its maximum abundance at stations in the
offshore waters of Lake Huron. The green algae remain abundant in October
(Fig. 36G) and November (Fig. 36H) samples, with maximum abundance in both
months being found in the southerly part of the Saginaw Bay interface and
southward along the Michigan coast.
Green Filament Number 5 (Gloeotilia sp.?)
This entity is of uncertain systematic position. It rather closely
resembles the genus Gloeotilia (Skuja, 1956) but we have been unable to
identify it with certainty. Although the individual plants are very small, it
sometimes occurs in very large numbers in Saginaw Bay and the adjacent waters
of Lake Huron. Its ecological affinities are entirely unknown, although
morphologically similar entities occur in Lake Erie and in certain areas of
Lake Ontario. It was present in relatively low abundance in early May samples
(Fig. 37A) with maximum abundance at nearshore stations along the Michigan
coast. By mid-May (Fig. 37B) it reached high population densities at stations
in the southerly part of the Saginaw Bay interface and south along the Michigan
coast. Smaller populations were also found at a number of offshore stations.
In early June (Fig. 37C) this species was abundant at the inner line of
stations in the Saginaw Bay interface, and was fairly abundant at nearshore
stations southward along the Michigan coast. It was also fairly widely
distributed at stations along the Canadian shoreline, but in considerably lower
abundance. This entity appeared to decline in abundance in late June
(Fig. 37D) but reached very high population densities at stations in the
southerly segment of the Saginaw Bay interface during July (Fig. 37E). During
this month however it was rarely noted in samples from offshore stations.
Unlike the previous month, this entity was most abundant at stations in the
northerly sector of the Saginaw Bay interface during August (Fig. 37F) and
during this sampling period it was absent from most stations south of Saginaw
Bay. Population densities remained high during October (Fig. 37G) and November
(Fig. 37H). During both months largest populations were found at stations in
the southerly sector of the Saginaw Bay interface and southward along the
Michigan coast. During November, significant populations were again found at
certain offshore stations.
157
-------
ERST TflHflS
GOOERICH
0
28 RPR - 3 MflY 74
'ORT HURON
GREEN
ERST TflHflS
GOOEHICH
0
14-17 MflT 74
HURON
GREEN
Figure 36. Seasonal abundance and distribution
trends of green algae. (continued)
158
-------
EflST TflHflS
4-8 JUN 74
GODERICH
IT HURON
GRFEN
ERST TflHflS
17-21 JUN 74
If IRON
Figure 36. (continued)
GODERICH
GREEN
159
-------
ERST TflHflS
0
17-22 JUL 74
GOOERICH
IT HURON
GREEN
ERST TftHflS
0
26-31 RUG 74
GOOERICH
Figure 36.
HURON
(continued)
GREEN
160
-------
EflST TflHflS
400007 HflfiBOR1
BEflCH
0
8-12 OCT 74
WGODERICH
HURON
GflEEN
EAST TflMflS
40000r HflRBOfi'
BEflCH
0
10-14 NOV 74
GOOERICH
HURON
Figure 36. (continued)
GREEN
161
-------
ERST IttWS
0
28 RPR - 3 MflT 74
GODERICH
IT HURON
GRFILSPE
EfiST TfiHfiS
0
14-17 nmr 74
ttGODERICH
HURON
GRFILSPE
Figure 37. Distribution of green filament sp. #5.
(continued)
-------
ERST TANAS
0
4-8 JUN 74
ttGOOERICH
IT HURON
GflFILSPE
EAST TRHAS
0
17-21 JUN 74
<, ^-
HURON
Figure 37. (continued)
GWILSPE
163
-------
EflST TflHflS
ttGOOERICH
EflST Tl
GRFILSPE
0
26-31 RUG 74
GBFILSPE
Figure 37. Continued
16 h
-------
0
8-12 OCT 74
8GOOERICH
IT HURON
GRFILSFE
EfiST TflHflS
BGOOERICH
0
10-14 NOV 74
HURON
Figure 37. (continued)
GWILSPE
165
-------
sp.
This species is unusual among the green algae, in that significant
populations were found at scattered stations in the offshore waters of Lake
Huron throughout the period of this study (Fig. 38A-H), It increases slightly
in abundance throughout the spring and summer, reaching maximum population
densities in the offshore waters during August. Abundance tends to decline
during October and November but, as in the previous months, no particular
pattern of areal distribution is evident.
C)iodaLtel4a
This species is a common element of phytoplankton assemblages in
mesotrophic to eutrophic lakes. Occasional individuals are found in plankton
collections from all areas of the Laurentian Great Lakes, but it reaches
significant abundance only in areas which have been enriched. Unlike the
species discussed previously, the areal and temporal distribution of £,. c^jLj-atja
in southern Lake Huron is extremely restricted. It was not noted in
collections taken during May and June, but was present at stations in the
Saginaw Bay interface and southward along the Michigan coast in July
(Fig. 39A). These populations apparently collapsed and only isolated
occurrences were noted during the August and October cruises (Fig. 39B-C) .
CoelaLs_trum microjjgrum
Ihis species is a common element of phytoplankton assemblages in
mesotrophic to eutrophic lakes. In the Laurentian Great Lakes it is usually
found in significant abundance only in eutrophic areas. In southern Lake Huron
it was entirely absent from early May samples, but isolated occurrences were
noted at stations in the Saginaw Bay interface waters during mid-May and early
June (Fig. MOA-B) . In late June (Fig. 40C) , it was relatively abundant at
stations in the southerly sector of the interface waters, and extended to a few
stations in the offshore waters of Lake Huron. In July (Fig. UOD), the species
was entirely limited to stations in the Saginaw Bay interface. It was absent
from August samples, but occurred again during the October sampling period
(Fig. JJOE), but again only at stations in the Saginaw Bay interface. It was
also present during November (Fig. 40F) at scattered stations in the Saginaw
Bay interface and along the U.S. and Canadian coasts.
Crucig_en4a cjua.drata
This species is usually a minor component of summer phytoplankton
assemblages in the upper Great Lakes. In southern Lake Huron only scattered
populations were noted during the May, June and July sampling cruises (Fig.
41A-D). During August (Fig. 41E) the abundance of this species increased
considerably, although its distribution remained erratic. Highest population
densities were found at offshore stations in the northerly sector of our
sampling array. Population densities again declined during the October
sampling cruise (Fig. 41F) and this species was absent from a majority of the
stations sampled. The decline apparently continued into November (Fig. 41G)
although isolated populations were still found, particularly at nea^shore
stations.
166
-------
ERST TRHflS
GOOERICH
0
28 RPR - 3 MflY 74
HURON
RKSPECOC
EflST TflHflS
ttGOOERICH
0
14-17 MflY 74
<, ^
HURON HKSPECOC
Figure 38. Distribution of frnkjusbrodesmus sp..
(continued)
167
-------
0
4-8 JUN 74
HURON
flKSPECOC
GOOEBICH
17-21 JUN 74
Figure 38.
IT HURON
(continued)
flKSPECOC
168
-------
GODERJCH
0
26-31 RUG 74
HURON
Figure 38. (continued)
169
RKSPECOC
-------
EflST TfiHflS
GOOERICH
0
8-12 OCT 74
HURON
flKSPECOC
ERST TflHflS
GOOOUCH
0
10-14 NOV 74
HURON
HK3PECOC
Figure 38. (continued)
170
-------
ERST
8GOOERICH
0
17-22 JUL 74
HURON
COCJLIfiT
ERST TOWS
GOOERICH
0
26-31 RUG 74
HURON
cocium
Figure 39. Distribution of Chodatella ciliata.
(continued)
171
-------
EflST TflMHS
8GOOQUCH
0
8-12 OCT 74
HURON
COCILIflT
Figure 39. (continued)
Gl_o_eocys.t:Ls filan.ctonj.ca.
Similar to the species previously discussed,
reached its
highest abundance in the summer phytoplankton assemblages in the upper Great
Lakes. It, however, tends to be more abundant, particularly in areas which
have been enriched. In southern Lake Huron, only very small populations were
found during the early and mid-May sampling periods (Fig. U2A-B) and most
occurrences were noted in the Saginaw Bay interface waters and at nearshore
stations. During June (Fig. M2C-D), this species became more generally
distributed and more abundant particularly at stations in the southerly sector
of the Saginaw Bay interface and stations southward along the Michigan coast.
A similar distribution pattern was noted during the July cruise (Fig. 42E) ,
although population densities continued to increase and the species became more
generally distributed at offshore stations. Similar to the other coccoid green
algae, this species reached its maximum abundance during August (Fig. ^2F) when
it was present in appreciable abundance at nearly all stations sampled. During
this cruise, unlike the other sampling cruises, maximum population densities
were found at offshore stations in the northerly and easterly sectors of the
sampling array. By October (Fig. 42G) , population densities were considerably
reduced and maximum abundance was again found at nearshore stations,
particularly near Saginaw Bay and southerly along the Michigan coast. This
decline continued into November (Fig. 42H), when only scattered minor
populations were found .
172
-------
ERST TflWflS
ttGODERICH
0
14-17 MflY 74
HURON
collator
OOT
GOCOUCH
4-8 JUN 74
HURON
CEHICnOP
Figure 40. Distribution of Coelastrum
microporum. (continued)
173
-------
ERST THHflS
GOOERICH
0
17-21 JUN 74
HURON caticncr
ERST TWR3
0
17-22 JUL 74
GOOHUCH
HURON
Figure 40. (continued)
cEHiovor
-------
ERST TRHRS
8-12 OCT 74
(GOOERICW
HURON
CQUOFW
EAST
0
10-14 NOV 74
Figure 40.
HURON
(continued)
cEHiovr
175
-------
EflST THHflS
0
14-17 MflY 74
BGOOQ1ICH
IT HURON
CUQUflORfl
8GODEBICH
0
4-8 JUN 74
Figure U1. Distribution of Crucigenia
(continued)
cuounoiw
176
-------
EAST TBHflS
GCOCniCH
0
17-21 JUN 74
HURON
CUQUROIW
EftST TAWS
cooemcM
0
17-22 JUL 74 x _
HUNON
Figure 41. (continued)
cueunom
177
-------
ERST TflWBS
0
8-12 OCT 74
Figure
RT HUftOH
(continued)
COOERICM
CUQURMW
IT 3
-------
EflST Ti
GOOQUCH
10-14 NOV 74
HURON
Figure 41. (continued)
cuouwiw
Mougeo.U.a sp.
We have been unable to make a satisfactory specific identification of this
entity due to the total lack of sexually mature material. It, or
morphologically very similar entities, are very abundant in western Lake Erie
and certain areas of Lake Ontario. In southern Lake Huron, it was very
uncommon during the May sampling cruises (Fig. 43A-B), although small
populations were noted at a few scattered stations. During early June (Fig.
43C), populations were noted at stations in the Saginaw Bay interface and at a
number of nearshore stations around the basin. Highest population densities
were found in the southerly sector of the Saginaw Bay interface waters. By
mid-June (Fig. 43D) population densities had increased slightly at stations in
the Saginaw Bay interface, particularly in the southern sector, but the species
was absent from other stations sampled. A similar pattern was noted during the
July sampling (Fig. 43E), although the species was again found at a few
nearshore stations along the Michigan coast. In August (Fig. 43F), Mougeot.ia
sp. was again relatively abundant in the Saginaw Bay interface waters, but
unlike the previous months, highest population densities were found at stations
north of the bay. This species had undergone a considerable increase in
abundance by the time the October samples were taken (Fig. 43G) , and high
population densities were found at stations in the southerly sector of the
Saginaw Bay interface and at stations southward along the Michigan coast. A
similar pattern was noted during the November cruise (Fig. 43H), although the
distribution of this entity had become somewhat more widespread and erratic.
179
-------
ERST TRHflS
cooenicH
0
28 RPR - 3 MflT 74
HURON
GLPLflNCT
EflST TflMflS
GODEFIICH
14-17 MflY 74
HURON
GLPUWCT
Figure H2. Distribution of Gloeocvstia
planetonica. (continued)
180
-------
ERST TfWflS
COOQUCH
0
4-8 JUN 74
HURON
GLPLflNCT
EHST TAWS
8GOOERJCH
0
17-21 JUN 74
HURON
GUT-fiNCr
Figure 42. (continued)
181
-------
ERST TflHflS
GOOERICH
0
26-31 RUG 74
HURON
GLPLflMCT
Figure 42. (continued)
182
-------
EflSt TflHHS
0
8-12 OCT 7U
GOOCRICH
HURON
GLPLflNCT
10-14 NOV 74
Figure 42.
HURON
(continued)
GLFLflNCT
183
-------
EflST TflMRS
8GOOOUCH
28 RPR - 3 MflY 74
HURON
MOSPECOR
ERST TflMflS
trcooenicH
0
14-17 MflY 74
HUHON
Figure H3. Distribution of Mouaeotia sp.
(continued)
184
-------
ERST TflNflS
4-8 JUN 74
ttGOOERICH
QRT HURON
HOSPCCOR
EHST TflHfiS
GOOERICK
0
17-21 JUN 74
HURON
Figure 43. (continued)
H09PECOR
185
-------
OBT TflHRS
17-22 JUL 7U
HURON
HOSfCCOR
EflST
B GOTHIC*
0
26-31 flUG 74
s _
HURON
Figure 43. (continued)
N03FECOR
186
-------
ERST TANAS
0
8-12 OCT 7U
ttcoooucx
HURON
HOSTCCOA
EB3T TANRS
GOOBfllCH
0
io-m NOV 74
HURON
M03PCCQH
Figure 43. (continued)
187
-------
Qoc vs t :ys spp.
Members of this genus are common minor components of summer assemblages in
the offshore waters of the Laurentian Great Lakes; however, they generally
reach maximum abundance under slightly eutrophied conditions. In southern Lake
Huron, Oocyst4_s was rare during the early May sampling period (Fig. U4A) with
only a few small populations being noted at stations in the Saginaw Bay
interface waters. By mid-May (Fig. 44B) , population levels had increased and
Qocys.tj.ff was present in significant abundance at stations outside the thermal
bar along both Michigan and Canadian coasts, and at a few stations in the
Saginaw Bay interface. During June (Fig. 44C-D), Qocys^tis continued to
increase in abundance, particularly at stations in the Saginaw Bay interface
and southward along the Michigan coast, although significant populations were
also found at scattered offshore stations. Its abundance continued to increase
during July (Fig. 4UE) and August (Fig. UHF) , with highest population densities
being found at stations in the Saginaw Bay interface waters. The genus reached
its maximum abundance during the October sampling period (Fig. 44G) when
significant populations were found at nearly all stations sampled. By November
(Fig. 44H), population densities were somewhat reduced, and its distribution
had become somewhat more erratic.
Scenedesmus
This species is generally rare in the offshore waters of the upper Great
Lakes, but may become very abundant in Lake Erie and Lake Ontario (Stoermer .e_t
JLL. , 197*0. In southern Lake Huron, its distribution was largely restricted to
a few stations in the Saginaw Bay interface waters during May and early June
(Fig. 45A-C). Somewhat increased abundances were noted during the late June
sampling cruise (Fig. 45D) but populations were again reduced by July (Fig.
45E) and had increased only slightly by the time the August samples were taken
(Fig. 45F) . £., quadrj.-Cajjda. reached its highest abundance during October (Fig.
45G), when large populations were found in the southerly sector of the Saginaw
Bay interface water southward along the Michigan coast, and at a few stations
in the southern part of the lake. Population levels were again reduced by the
time the November samples were taken (Fig. ^5H) , although the species was still
present at a few stations of the Saginaw Bay interface waters southward along
the Michigan coast.
Staurastrum paradoxum
Although many members of this genus are restricted to nutrient-poor or
dystrophic waters, ^.. par^adg-xuro generally reaches its highest abundance in
eutrophic areas. In the Great Lakes, it is relatively abundant in Lake Erie
(Vollenweider .e_t ^1. , 197*0 and in Lake Ontario (Stoermer .et .aJL. , 197*0.
Although it usually does not reach large population densities, it may
contribute a significant fraction of the biomass of phytoplankton assemblages
because of its very large cell volume (Stoermer and Ladewski, 1978). In
southern Lake Huron, first occurrences were noted in early June (Fig. 46A) at
the inner line of stations in the Saginaw Bay interface. By late June (Fig.
46B) , relatively large populations were found in stations in the southerly
sector of the Saginaw Bay interface and at a few stations southward along the
Michigan coast. Fewer occurrences were noted during the July sampling (Fig.
46C) , when it was again restricted to stations near the Saginaw Bay interface
and southerly along the Michigan coast. Unlike the. previous month, during the
August sampling period (Fig. M6D) the only populations noted were found at
188
-------
EB3TI TfiHflS
GOOERICH
0
28 flPR - 3 MflY 74
HURON
OOSPP
EBST TflHRS
ttGOOERICH
0
m-17 MflT 74
HURON
OOSPP
Figure 4^. Distribution of OQcvstis spp.,
(continued)
189
-------
ERST TRHRS
WGODERICH
4-8 JUN 74
HURON
OOSPP
EflST TfiHflS
0
17-21 JUN 74 ^ __
HURON
Figure 44. (continued)
GOOERICH
OOSPP
190
-------
ERST TflHRS
0
17-22 JUL 74
GOOERICH
HURON
OOSPP
EBsrr TI
y
y
y
'll //.
BGODERICM
26-31 RUG 74
>> ..
HURON
Figure 44. (continued)
OOSPP
191
-------
EflST TflHfiS
0
8-12 OCT 74
ttGOOEBJCH
HURON
003PP
EfiST
0
10-14 NOV 74
ICH
HURON
OOSPf
Figure 44. (continued)
192
-------
ERST THHflS
0
28 RPR - 3 MRY 74
GODERICH
PORT HURON
SCQUfiDRI
EflST TflWRS
0
14-17 MRY 74
CODER I CM
CRT HURON
SCQUflDRI
Figure 45- Distribution of Scenedesmus
. (continued)
193
-------
4-8 JUN 74
PORT HURON
SCQURORI
EflST TfiWflS
0
17-21 JUN 74
IT HURON
Figure 45. (continued)
19 h
ttGOOERICH
scounoni
-------
ERST TflHflS
0
17-22 JUL 74
CODERICH
IRT HURON
SCQUflORI
EflST TRHRS
0
26-31 RUG 74
Figure 45.
ORT HURON
(continued)
GODERICH
SCQUflDRI
195
-------
0
8-12 OCT 74
ttGODERICH
'PORT HURON
SCQUfiDRI
ERST TflMflS
10-14 NOV 74
\ .-
HURON
Figure 45. (continued)
ft CODER I CM
196
-------
EflST TflHRS
0
4-8 JUN 74
GOOERICH
'ORT HURON
SRPHRfl
17-21 JUN 74
8GOOERICH
HURON
SRPflRfl
Figure 46. Distribution of Staurastrum
paradoxum. (contiued)
197
-------
EflST TflHflS
0
17-22 JUL 74
ttGODERICH
HURON
SRPflRfl
EflST TflWflS
GODERICH
0
26-31 RUG 74
s ,
HURON
Figure 46. (continued)
SRPflRfl
198
-------
stations in the northerly sector of the Saginaw Bay interface waters. During
October (Fig. 46E) , most occurrences were found at stations in the southerly
part of the Saginaw Bay interface and southward along the Michigan coast
although isolated occurrences were found north of Saginaw Bay and at one
station in the offshore waters of southern Lake Huron. Abundance was reduced
by November (Fig. 46F), although the species occurred at a few stations in the
Saginaw Bay interface.
Tetraedron mj.nj.mum
This species is occasionally found in offshore summer phytoplankton
assemblages in the upper Great Lakes, but is generally more abundant in areas
that are somewhat eutrophied. In southern Lake Huron, it was first noted in
mid-May (Fig. 47A) at a single station in the southern part of the Saginaw Bay
interface waters. By early June (Fig. 4?B), it was present at most stations in
the Saginaw Bay interface and isolated occurrences were noted along the
Michigan coast. It appeared to decline in abundance by late June (Fig. 4?C),
although populations were still found in scattered stations in the Saginaw Bay
interface waters and southward along the Michigan coast. It had again
increased in abundance by the time mid-July (Fig. 47D) samples were taken.
Maximum abundance was found in the southerly sector of the Saginaw Bay
interface waters, although occasional populations were found in stations
southerly along the Michigan coast. Unlike previous months, X- minimum was
found in several of the July samples taken along the Canadian coast. During
August (Fig. 47E), only a few occurrences were noted at stations in the Saginaw
Bay interface waters and the species remained relatively rare during October
(Fig. 4?F) and November (Fig. 4?G) although populations were still found at
stations in the Saginaw Bay interface waters and occasionally at nearshore
stations in the main body of Lake Huron.
Cyanophyta
The abundance of blue-green algae is sometimes looked upon as a rough
index of eutrophication. The situation in southern Lake Huron is somewhat
confounded by the fact that the blue-green algal flora is a mixture of very
highly eutrophication-tolerant forms derived from Saginaw Bay and less
eutrophication-tolerant species which flourish in the open waters of the lake,
particularly during periods of silica limitation. During early May (Fig. 48A),
blue-green algae were practically absent from the stations sampled in southern
Lake Huron. By mid-May (Fig. 48B), however, significant numbers were found at
a few stations in the southerly sector of the Saginaw Bay interface waters.
Blue-green abundance increased slightly in early June (Fig. 48C) , but
distribution was largely restricted to stations in the Saginaw Bay interface.
By late June (Fig. 48D), populations had spread to a number of stations along
the Michigan coast and a few stations along the Canadian coast. In mid-July
(Fig. 48E), the blue-green algae were again largely restricted to stations in
the Saginaw Bay interface and southward along the Michigan coast. This
situation changed significantly in August (Fig. 48F), when very large
populations were found in the Saginaw Bay interface waters and smaller
populations were found at most stations sampled throughout the lake. The
blue-green algae were most abundant in southern Lake Huron during the October
sampling period (Fig. 48G). Very high population densities were found in the
southerly sector of the Saginaw Bay interface, and significant populations
199
-------
ERST TflWflS
8-12 OCT 74
GODERICH
IT HURON
SRPflRfl
EflST TflWflS
GOOERICH
0
10-14 NOV 74
IT HURON
SRPflRR
Figure 46. (continued)
200
-------
EBST TflURS
14-17 MflY 74
teGOOGRICH
HURON
TEHINIHU
4-8 JUN 74
HURON
TEMINIMU
Figure iJ7. Distribution of Tetraedron
(continued)
201
-------
ERST TflMRS
0
17-21 JUN 74
GOOERICH
HURON
TQUHIHU
»GODE*ICH
0
17-22 JUL 74
HURON
TEHINIHU
Figure ^7 (continued)
202
-------
ERST TOWS
0
26-31 RUG 74
ttCOOEMCH
HURON
TEM1NIHU
TOT
BGOOERIW
8-12 OCT 74
HURON
Figure 4?. (continued)
203
TOUNIHU
-------
am
GOOOUCH
0
10-14 NOV 714
HURON
TEHIHIMU
Figure 4?. (continued)
were found at most stations sampled throughout the lake. By November (Fig.
48H) , blue-green algal abundance was reduced; however, significant populations
were still found at most stations sampled.
Anabaena flos-aQua_e
This species is a common minor component of phytoplankton assemblages in
the upper Great Lakes, and generally reaches very high abundance only in areas
which have been significantly eutrophied. Estimates of its distribution are
somewhat confounded by the fact that it is a gas-vacuole-forming species and
often develops in very patchy surface blooms. In southern Lake Huron, it was
first noted during the early June sampling cruise (Fig. 49A) when small
populations were found at most of the inner stations in the Saginaw Bay
interface, and a large bloom was found at station 49. By late June (Fig. 49B) ,
this species was abundant at several stations in the southerly sector of the
Saginaw Bay interface and southward along the Michigan coast. Abundance was
reduced in the July samples (Fig. 49C) , and only small populations were found
at a few stations in the Saginaw Bay interface. In August (Fig. 49D), a large
bloom occurred at station 48 and smaller populations were found in the Saginaw
Bay interface and at a few stations in the southeastern sector of the lake
along the Canadian coast. During October (Fig. 49E), abundance of this species
was reduced and distribution was erratic; by November (Fig. 49F), it was
essentially absent from southern Lake Huron. This species is macroscopic and
readily observable in the surface waters of the column. It possibly could be
used to visually trace the transport of water from the bay. In an ancillary
study, we found amounts in the 1 m samples in excess of four times those of the
5-m samples, demonstrating the species' buoyancy, and its preference for
surface waters.
204
-------
EflST TfiHflS
GOOERICH
0
28 flPR - 3 MflT 74
HURON
BLUGR
EflST TflHflS
600ERICH
0
14-17 MflT 74
<, ^
KJRON 8LUGR
Figure 48. Seasonal abundance and distribution
trends of blue-green algae.
(continued)
205
-------
EflST TflHflS
0
4-8 JUN 74
GOOERICH
'ORT HURON
BLUGR
GOOERICH
0
17-21 JUN 74
BLUGR
Figure 48. (continued)
206
-------
ERST TAHftS
0
17-22 JUL 7U
GOOEfllCH
IT HURON
BLUGR
EflST Tl
0
26-31 RUG 74
HURON
BLUGR
Figure 48. (continued)
207
-------
0
8-12 OCT 74
8GODERICH
IT HURON
BLUGfl
GOOERICH
0
10-14 NOV 74
Figure 48,
'OflT HURON
(continued)
BLUGfl
208
-------
gGOOERICH
0
4-8 JUN 74
HURON
RBFLOSM
ERST TRMRS
GOOERICH
0
17-21 JUN 74
HURON
ABFLOSRQ
Figure 49- Distribution of Anabaena flos-aQuae.
(continued)
209
-------
EflST TflHflS
ttGOOERICH
0
26-31 RUG 74
>, .
HURON
Figure 49. (continued)
FWFLOSflQ
210
-------
ERST TfiHflS
GOOQUCH
0
8-12 OCT 74
HURON
flBFLOSflQ
ERST TflMflS
HURON
10-14 NOV 74
Figure 49. (continued)
211
flBFLOSRB
-------
Anabaena subcylindrica
The distribution and autecology of this species is very poorly known.
However, it has been particularly associated with water masses derived from
Saginaw Bay (Schelske et al., 1974). In our samples, it was present in very
limited abundance during May (Fig. 50A-B), and only slightly more abundant
(although more widely distributed) during early June (Fig. 50C). In July (Fig.
SOD), it was present in high abundance at a few stations in the southern sector
of the Saginaw Bay interface waters. It was almost equally abundant in August
(Fig. 50E), but its highest population densities were found at stations in the
northern sector of the Saginaw Bay interface and northward along the Michigan
coast. Populations of this species were considerably reduced by the time the
October (Fig. 50F) samples were taken; it was essentially absent from samples
taken after this date.
Anacystis cyanea
This species is one of the blue-green algae capable of forming the
classical nuisance blooms often found in small eutrophic lakes. In the
Laurentian Great Lakes, it is rare except in areas which have been highly
disturbed. Its distribution in southern Lake Huron is very limited, largely
restricted to areas directly affected by the outflow from Saginaw Bay. In
July, a large population was found at station 40 (Fig. 51A), and in August a
large population was found at station 37 (Fig. 51B). During both of these
months, other occurrences were small and limited to stations in the Saginaw Bay
interface. Maximum abundance of this species in southern Lake Huron occurred
during October (Fig. 51C). It was present in highest abundance at several
stations in the southerly sector of the Saginaw Bay interface during that
month. By November (Fig. 51D), its distribution was restricted to only two
stations, again in the southerly sector of the Saginaw Bay interface waters.
Anacystis incerta
Unlike A. cyanea, this species is not particularly uncommon in the
offshore waters of the Great Lakes and may be quite abundant in areas that have
been significantly disturbed. Although reported as capable of forming nuisance
blooms (Drouet and Daily, 1956), it has not been observed to do so in the Great
Lakes. Its seasonal pattern is somewhat unusual for a blue-green alga, in that
it generally reaches peak abundance late in the fall, with significant
populations surviving into the winter months (Stoermer et al., 1974). In
southern Lake Huron, isolated populations were found in mid-May, early June,
and late June (Fig. 52A-C), but it was absent from July samples (Fig. 52D).
Several large and erratically distributed populations were noted during the
August sampling (Fig. 52E), and the species reached its peak abundance during
October (Fig. 52F) when significant populations were present at most stations
sampled. Abundance was somewhat reduced in the November samples (Fig. 52G),
although it was still present in significant abundance at a number of stations.
Anacystis thermalis
This species is a common minor element of phytoplankton assemblages in
mesotrophic to marginally eutrophic lakes. It is often quite abundant in
regions of the Great Lakes that have been sufficiently eutrophied to induce
silica limitation, but is generally not a dominant element of the flora in
212
-------
EflST THWflS
CODERICH
0
28 RPR - 3 MflT 74
IT HURON
HBSUBCTL
ERST TflWflS
0
14-17 MflT 74
IT HURON
GODERICH
RBSUBCTL
Figure 50. Distribution of Anabgena subcvlindrica.
(continued)
213
-------
EflST TflWflS
ttGODERICH
0
4-8 JUN 74
HURON
flBSUBCTL
EflST TflHflS
GODERICH
0
17-22 JUL 74
Figure 50.
IT HURON
(continued)
RBSUBCTL
214
-------
ERST TRWflS
0
26-31 RUG 74
GOOERICH
IT HURON
RBSUBCYL
EflST THHfiS
0
8-12 OCT 74
GODERICH
Figure 50.
RT HURON
(continued)
HBSUBCTL
215
-------
EHST THHfiS
GOOERICH
0
17-22 JUL 74
HURON
RTCYflNEfl
EflST THWflS
GOOBRICH
0
26-31 RUG 74
HURON
flYCTBNEfl
Figure 51. Distribution of Anacvstis gyanea.
(continued)
216
-------
ERST TRHRS
BtGODERICH
0
8-12 OCT 74
IT HURON
RYCYRNEfl
EflST TRHfiS
GOOERICH
0
10-14 NOV 74 s_
HURON
Figure 51. (continued)
RYCYHNER
217
-------
EfiST TflHflS
0
14-17 MflT 74
8GOOERICH
HURON
RYINCERT
ERST TfiHflS
GOOERICH
0
4-8 JUN 74
HURON
Figure 52. Distribution of Anacvstis incerta.
(continued)
218
-------
EflST TflNflS
ttGOMJUCH
0
17-21 JUN 74
HURON
RYINCERT
EflST TflHflS
GOOERICH
0
17-22 JUL 74
-------
ERST Tl
0
26-31 RUG 714
CODERICH
HURON
flYINCERT
GOOERICH
0
8-12 OCT 74
HURON
Figure 52. (continued)
220
flTINCERT
-------
EflST TflHBS
BGOOEmCH
0
10-14 NOV 74
IT HURON
RYINCERT
Figure 52. (continued)
regions which have been grossly perturbed. In southern Lake Huron, only
scattered isolated populations were found during the mid-May, June, and July
cruises (Fig. 53A-D). During August (Fig. 53E), it was present at most
stations sampled, and abundant at several stations north of the Saginaw Bay
interface. It reached its maximum abundance during October (Fig. 53F) when
significant populations were present at most stations sampled throughout the
lake. Abundance of this species had been reduced by the time the November
samples were taken (Fig. 53G), although it was still present at the majority of
the stations sampled, and abundant at some stations in the southern part of the
sampling array.
Aphanizomenon flos-aquae
This species is a primary contributor to nuisance blue-green algal blooms
in highly eutrophic environments. In the Laurentian Great Lakes, its
distribution is restricted to highly disturbed areas. In southern Lake Huron,
small populations were found in the Saginaw Bay interface waters during the
early and late June cruises (Fig. 54A-B). By the time July samples were taken
(Fig. 54C), population densities had increased somewhat at stations in the
southerly sector of the Saginaw Bay interface waters. Even higher abundance
was found during the August cruise (Fig. 54D); however, at this time, maximum
abundance occurred at stations in a northerly sector of the Saginaw Bay
interface. Maximum abundance of this species occurred during the August cruise
221
-------
GOOERICH
0
14-17 MflY 74
HURON
fitTHERNfl
ERST TAWS
tt GOOERICH
0
4-8 JUN 74
HURON
BYTHERHfl
Figure 53- Distribution of Anacvstis thermalis.
(continued)
222
-------
BUST TAURS
GOOGRICH
0
17-21 JUN 74
HURON
RTTHERHB
EflST TflHRS
GOOERICH
0
17-22 JUL 74 k__
"HURON
Figure 53- (continued)
OTHER*)
223
-------
ERST Tl
.11 111
0
26-31 RUG 74
HURON
RYTHOWR
ERST
BtGOOERICH
8-12 OCT 74 ^
HURON
Figure 53- (continued)
flYTHEBNR
22k
-------
EflST TflHflS
8GOOERICH
0
10-1U NOV 74
HURON
RYTHEIWR
Figure 53. (continued)
(Fig. 54E) when large populations were present in samples in the southerly
sector of the Saginaw Bay interface waters and southward along the Michigan
coast. Abundance of .4. flos-aauae had declined significantly by the time the
November samples were taken (Fig. 54F). Small populations were found, however,
at offshore stations as far east as Station 11, apparently as a result of
dispersion of this organism from Saginaw Bay.
Gorophosphaeria lacustrls
This species is a common component of summer phytoplankton assemblages in
mesotrophic to slightly eutrophic lakes. It commonly occurs in the offshore
waters of the Laurentian Great Lakes in low abundance and may become quite
abundant in regions where silica has been depleted during summer
stratification. It is quite abundant in southern Lake Huron, although its
distribution is temporally and spatially erratic. It was first detected during
the early June sampling cruise (Fig. 55A) at a few stations in the Saginaw Bay
interface waters. In late June (Fig. 55B), it was abundant at a few stations
of the southerly sector of the Saginaw Bay interface and at isolated stations
outside the thermal bar along both the U.S. and Canadian coasts. Populations
were found at a few stations near the Saginaw Bay interface during both July
(Fig. 55C) and August (Fig. 55D); during August, small populations were also
found at several nearshore stations along the Michigan coast and in the
225
-------
ERST TfiHflS
8GOOERICH
0
4-8 JUN 74
HURON
MFLOSflQ
ERST TflHflS
ttGOOEMCH
0
17-21 JUN 74
HURON
HtFUHM
Figure 51*. Distribution of Aphanizomenon fJ._Q.3-aguae.
(continued)
226
-------
EAST TflHflS
0
17-22 JUL 74
HURON
RZFLOSRQ
UGODERICH
0
26-31 RUG 7U
HUhON
Figure 54. (continued)
227
-------
8-12 OCT 74
GODERICH
HURON
RZFLOSW
ERST TfMflS
GOOERICH
0
10-14 NOV 74
HURON
Figure 51*. (continued)
HZFlOSfla
228
-------
ERST TflWflS
CODERICH
0
4-8 JUN 74
'ORT HURON
GML.HCUST
EflST TflWHS
ft GODERICH
0
17-21 JUN 74
HURON
GMLHCUST
Figure 55. Distribution of Gorophosphaeria lacustria.
(continued)
229
-------
EflST TflHflS
0
17-22 JUL 74
GODERICH
HURON
GMLflCUST
EflST TflHflS
GOOEfllCH
0
26-31 RUG 74
HURON
GMLflCUST
Figure 55- (continued)
1 230
-------
GODEHICH
0
10-14 NOV 74
ORT HURON
Figure 55. (continued)
GMLflCUST
231
-------
southern sector of the lake. This species was present in increased abundance
during the October sampling period (Fig. 55E) and, unlike the previous month,
it was present in significant abundance at a number of stations in the offshore
waters of southern Lake Huron. This trend continued in November (Fig. 55F)
when significant populations were present at a majority of the stations sampled.
Q_3clllatoria bornetii
The autecology and distribution of this species is very poorly known.
While it is widely distributed in the upper Great Lakes, it is rarely present
in abundance. In Lake Michigan, maximum abundance of this species occurs at
thermocline depth during summer stratification; however, it is often rare or
absent in the surface waters. In southern Lake Huron, occasional small
populations of the species were found in samples from early May through late
June (Fig. 56A-D) with a slight trend towards increasing abundance throughout
this period. Populations apparently collapsed in the surface waters of
southern Lake Huron during July and August (Fig. 56E-F) and only isolated small
populations were found at a few nearshore stations. This species was again
widely distributed in the October samples (Fig. 56G) with maximum abundance
occurring at stations 63 and 64 in the extreme southern part of the lake.
Relatively small populations were found throughout the area sampled during the
November cruise (Fig. 56H), with no apparent pattern to their distribution.
Q_scilla,toria retzij.
This species usually grows in eutrophic environments and has rarely been
reported from the upper Great Lakes. In southern Lake Huron, it first appeared
in our mid-May samples (Fig. 57A) from the Saginaw Bay interface waters and
southward along the Michigan coast. By early June (Fig. 57B) large populations
were present at the inner line of stations in Saginaw Bay and small populations
were present in most stations southward along the Michigan coast and eastward
into the lake as far as stations 54 and 60. By mid-June (Fig. 57C), average
abundance of this species had declined somewhat in the Saginaw Bay interface;
it was not found in the open lake stations that it had occupied the previous
month, although it was still present in nearshore stations north of Harbor
Beach. Its abundance was further restricted in July (Fig. 57D) when abundant
occurrences were limited to stations in the southerly sector of the Saginaw Bay
interface. In August, as was the case with many eutrophication tolerant taxa,
highest populations of Q. retzii were found in th'e northerly sector of the
Saginaw Bay interface waters. In October (Fig. 57F) abundant occurrences were
restricted to a few stations in the southerly part of Saginaw Bay interface,
even though small populations were found at stations south along the Michigan
coast, and at a number of offshore stations. By November (Fig. 57G), abundance
of this species was greatly reduced, with only a few small populations found in
samples from the Saginaw Bay interface waters.
Filamentous Blue-Green Al^ae
Since the filamentous forms of blue-green algae perhaps have the greatest
potential for producing nuisance conditions, we have plotted the composite
abundance of forms described previously, plus the occurrences of several taxa
of minor abundance. During early May (Fig. 58A), this group was of very minor-
importance in southern Lake Huron where only occasional specimens were noted.
232
-------
EflST TflWflS
0
28 RPR - 3 MflY 74
GOOERICH
IRT HURON
OSBORNET
0
14-17 MflY 74
GOOFRICH
'ORT HURON
OSBORNET
Figure 56. Distribution of Oscillatoria
faprnetli. (continued)
233
-------
EflST TflHflS
0
4-8 JUN 74
IT HURON
OSBORNET
GOOERICH
0
17-21 JUN 74
Figure 56.
IT HURON
(continued)
OSBORNET
234
-------
EflST THWflS
0
17-22 JUL 74
GODERICH
HURON
OSBORNET
EflST TflHflS
GODERICH
0
26-31 RUG 74
HURON
Figure 56. (continued)
OSBORNET
235
-------
EflST TflHflS
8-12 OCT 74
GOOERICH
HURON
OSBORNET
0
10-14 NOV 74
HURON
OSBORNET
Figure 56. (continued)
236
-------
EflST TfiHflS
0
14-17 MflY 74
tttGODERICH
IT HURON
OSRETHJI
0
4-8 JUN 74
HURON
osnmn
Figure 57. Distribution of O^pillatoria
(continued)
237
-------
0
17-21 JUN 74
IT HURON
osnrrzn
EflST TflHflS
ttGOOERICH
0
17-22 JUL 74
HURON
Figure 57- (continued)
OSRETZII
238
-------
EflST Ti
0
26-31 flUG 74
GOOERJCH
IT HURON
OSRETZII
EflST TRWflS
&GOOERICH
0
8-12 OCT 74
HURON
osnrrzn
Figure 57. (continued)
239
-------
EflST TRHflS
GOOERICH
0
10-14 NOV 74
IT HURON
OSBETHII
Figure 57. (continued)
By mid-May (Fig. 58B) , significant populations were found at stations in the
south part of the Saginaw Bay interface waters, and small populations were
dispersed southward along the Michigan coast. During June (Fig. 58C-D),
members of this group were present at most stations in the Saginaw Bay
interface waters, but their dispersion into the open lake was limited largely
to stations near the U.S. coast north of Harbor Beach. Somewhat surprisingly,
the distribution of these organisms was even more limited in July (Fig. 58E)
than it had been in the previous month. In August (Fig. 58F), unlike all other-
months, maximum abundance of filamentous blue-green algae occurred at stations
in the northern part of the Saginaw Bay interface "waters, and populations
appeared to be dispersed northward along the Michigan coast. These species
reached their maximum abundance in October (Fig. 58G), when they were very
abundant in the southerly sector of the Saginaw Bay interface and southward
along the Michigan coast as far as station 13, and present at detectable levels
as far south as stations 63 and 64 above Port Huron. During November (Fig.
58H), the abundance of this group declined, although small populations were
widely dispersed in the offshore waters, occurring as far east as stations 11
and 55.
Chrysophyta
In southern Lake Huron, this group is represeted mostly by flagellate
forms, the majority of which are colonial. Most of the more abundant species
240
-------
EflST TflWRS
HRRBOR
30007- BEflCH
0
28 RPR - 3 MRY 74
CODERICH
IT HURON
BGFIL
EflST TflHflS
CODERICH
0
14-17 MflT 74
"~~ HURON BGFIL
Figure 58. Seasonal abundance and distribution
trends of total blue-green filaments.
(continued)
-------
EflST TfiHflS
HRRBOR
SOOOr BERCH
0
4-8 JUN 74
GODERICH
BGFIL
EHST THWflS
0
17-21 JUN 74
FORT HURON
Figure 58. (continued)
GODERICH
BGFIL
242
-------
EflST TflWflS
^r\r\r\ HflRBOR
oOOOr BERCH
0
17-22 JUL 74
W CODERICH
'ORT HURON
BGFIL
EflST TflWflS
0
26-31 RUG 74
Figure 58,
PORT HURON
(continued)
GODERICH
BGFIL
243
-------
ERST THWflS
0
8-12 OCT 74
CODERICH
IT HURON
BGFIL
0
10-14 NOV 74
GODERICH
HURON
BGFIL
Figure 58. (continued)
244
-------
are usually reported from oligotrophic to mesotrophic waters, although they may
form ephemeral blooms under a wide variety of conditions. In early May (Fig.
594), this group was most abundant at a few stations in the northerly sector of
the Saginaw Bay interface waters with small and fairly uniform populations
occurring over the rest of the regions sampled. Distribution was similar
during mid-May (Fig. 59B), although highest abundance during this period was
found in the southerly sector of the Saginaw Bay interface waters and southward
along the Michigan coast. This trend was accentuated in the early June cruise
(Fig. 59C), when fairly high population levels were noted as far southward as
station 59. Population levels had been strongly reduced by the time the late
June (Fig. 59D) samples were taken; numbers were low and rather uniform
throughout the area sampled with a slight trend toward highest population
densities occuring at stations where this group had been least abundant in the
previous sampling period. In July (Fig. 59E), population levels increased,
particularly at the outer stations in the Saginaw Bay interface and at stations
in the far southern part of the lake. During August (Fig. 59F), chrysophycean
algae were abundant at stations in the central and northerly sector of the
Saginaw Bay interface and southward along the Michigan coast, but present in
only very small numbers at most offshore stations. In October (Fig. 59G), this
group remained abundant at stations north of the Saginaw Bay interface and
became quite abundant at a limited number of offshore stations. Numerical
abundance of this group was strongly reduced in November (Fig. 59H) when most
significant occurrences were found at nearshore stations.
Dinobryon divergens
This species is apparently widely distributed and may occur in waters of
significantly different trophic levels. It tends to form ephemeral blooms,
particularly following major blooms by other species (Hutchinson, 1967).
During May (Fig. 60A-B), only scattered isolated populations were noted.
However, in early June (Fig. 60C), this species occurred in significant
abundance in a series of stations running southward from the Saginaw Bay
interface along the Michigan coast and outward as far as station 60. By late
June (Fig. 60D), the population had entirely collapsed, and D. divergens was
found only at scattered stations rimming the region where it had been abundant
during the previous sampling period. In July (Fig. 60E), D. divergens was
again abundant at stations in the Saginaw Bay interface, southward along the
Michigan coast, and at stations in the far southerly sector of the lake.
Similar to the June sequence, the July populations had apparently collapsed by
the time the August samples were taken (Fig. 60F) and only a few scattered
populations were noted. Distribution of D_. divergens remained scattered during
October (Fig. 60G); by November (Fig. 60H), population levels had increased
somewhat with abundant occurrences largely restricted to nearshore stations.
Chrysosphaerella longispina
This species is usually a minor component of phytoplankton assemblages in
oligotrophic to mesotrophic lakes and small ponds (Huber-Pestalozzi, 1941). It
has rarely been reported from the Laurentian Great Lakes. It appears to be
particularly abundant in Lake Huron (Schelske et al., 1974). During the
present study, only small, isolated populations were found in samples taken
from early May through June (Fig. 61A-D). However, during August (Fig. 61E) it
245
-------
EAST TflHflS
0
28 RPR - 3 MRT 74
IT HURON
CHRTS
EHST TflHflS
0
14-17 MflT 74
ttGODERICH
HURON
CHRYS
Figure 59. Seasonal abundance and distribution
trends of Chrysophytes. (continued)
2146
-------
EflST
4-8 JUN 74
HURON
CHRTS
EfiST TflHflS
GODERICH
0
17-21 JUN 74
HURON
Figure 59. (continued)
CHRTS
-------
0
26-31 RUG 74
CMflYS
Figure 59. (continued)
21*8
-------
EAST TRHflS
JJ 1 1 1 J
0
8-12 OCT 74
GOOERICH
HURON
CHRYS
ERST TflHflS
0
10-14 NOV 74
«,.
HURON
Figure 59. (continued)
BGOOERICH
CHRTS
249
-------
ERST TflHflS
GODERICH
0
28 flPR - 3 MflY 74
ORT HURON
ONDIVERG
EflST Tl
ttGOOERICH
0
14-17 MflY 74
'ORT HURON
DNOIVERG
Figure 60. Distribution of Dinobrvon dlvergens.
(continued)
250
-------
0
4-8 JUN 74
8GOOERICH
HURON
DN01VERG
ERST TflHflS
ttGOOERICH
0
17-21 JUN 74
HURON
Figure 60. (continued)
ONOIVERG
251
-------
ERST TPHflS
ttGOOEfllCH
26-31 HUG
HURON
DNDIVERG
Figure 60. (continued)
-------
ERST THHflS
0
8-12 OCT 74
GODERICH
QRT HURON
DrtOIVERG
EflST
0
10-14 NOV 74
HURON
ONUlVtflG
Figure 60. (continued)
253
-------
EAST TAHflS
0
28 flPR - 3 MRY 74
OR7 HURON
CQLONGJS
EAST TflHflS
0
14-17 MflY 74
IT HURON
COLONSIS
Figure 61. Distribution of Chrvsosphaerella
longjspina. (continued)
-------
EflST TftHflS
0
4-8 JUN 74
1ORT HURON
CQLONGIS
EflST TflMflS
17-21 JUN 74
HURON
COLONGIS
Figure 61. (continued)
255
-------
EflST TflWflS
0
8-12 OCT 74
COLONGIS
HURON
CQLONGIS
Figure 61. (continued)
256
-------
CAST TPHflS
GOOERIO1
10-14 NOV 74
HURON
COLONGIS
Figure 61. (continued)
bloomed at stations in the central and northern parts of the Saginaw Bay
interface waters and at stations southward along the Michigan coast. During
the October sampling period (Fig. 61F), population levels remained high at
stations north of the Saginaw Bay interface and at a series of midlake stations
surrounding the region in which it had been abundant during August. By November
(Fig. 61G), these populations had collapsed, and only isolated minor
occurrences were noted.
Chrvsococcus dpkidophQrus
Like the species discussed above, this taxon has rarely been reported from
the Laurentian Great Lakes, although it appears to be abundant in Lake Huron.
In our samples, its distribution is highly unusual, in that it occurs at all
seasons sampled (Fig. 62A-H) but has no readily apparent pattern of
distribution. Population maxima occurred during July (Fig. 62E) and October
(Fig. 62G). Although highest absolute population densities are reached at
stations north of the Saginaw Bay interface during October, population
densities at both nearshore and offshore stations tend to be remarkably similar
during other sampled months.
Ochromonas sp.
During the early May sampling period (Fig. 63A), this small chrysophycean
flagellate was abundant at stations north of Saginaw Bay along the Michigan
coast and in the southern portion of the lake, but virtually absent from
257
-------
BGOOQUW
0
28 RPR - 3 MflY 74
HURON
CVDOKIDO
EAST TAUflS
ttCOOCRICH
0
14-17 MflY 74
HUfWN
CVOOKIOO
Figure 62. Distribution of ChrYSQCQCCUs
doki-dopborus. (continued)
-------
EAST TflMflS
GOQQIICH
0
4-8 JUN 74
OUT HURON
CVDOKJOO
0
17-21 JUN 74
Figure 62,
IT HURON
(continued)
RGOOOUCH
CVOOKIOO
259
-------
EBST ^Wt&J)/ J
17-22 JUL 74
COOOtlCH
IT HURON
CVOOKIOO
CAST TWOS
0
26-31 HUG 74
HURON
Figure 62. (continued)
260
GOOQUCH
CVOOUQC
-------
OBT
tBGOOOUCH
0
8-12 OCT 74
CRT HUfWN
CVOOKIDO
EAST TflNAS
coocnicH
0
10-14 NOV 74
CVDOKIDO
Figure 62. (continued)
261
-------
oat
ttGOOUCH
28 RPR - 3 MOT 74
1U-17 MflY 74
OC3FECOR
HUMN
ourccoH
Figure 63. Distribution of Qchromonas sp.. (continued)
262
-------
ERST TMWS
GODERICH
OUT MJMN
OC3PCCOH
ewr
BCOOOUCH
17-21 JUN 74
MMM
Figure 63- (continued)
263
OCJTECOH
-------
ERST TfiNBS
GOOOIICH
17-22 JUL 74
HUKM
OC3PECQR
ERSTTWRS
26-31 RUG 74
*> .
HUMN
Figure 63- (continued)
GOOCniCH
OC3TECOH
264
-------
CAST TflMftS
0
8-12 OCT 74
GOOOICH
IT HUMN
OC3FECOR
ER5T TANR3
cooenicH
0
10-14 NOV 74
Figure 63-
17 HURON
(continued)
OCSt-ECt*
265
-------
stations in the southern sector of the Saginaw Bay interface waters and
nearshore stations above Harbor Beach. By mid-May (Fig. 63B), it had become
generally distributed and remained so during June (Fig. 63C-D). Population
levels were reduced during July and August and reached the seasonal minimum in
October, with only slight recovery at stations sampled during the November
cruise (Figs. 63E-H).
Cryptophyta
The cryptomonads are a rather enigmatic group of organisms with a number
of unusual morphological and physiological characteristics. They are
extensively distributed in nearly all fresh and brackish bodies of water. They
are generally distributed throughout the Great Lakes system, and unlike most
other phytoplankton groups, what appear to be the same species occupy habitats
ranging from pristine to highly disturbed. Although highest abundance is
usually found in eutrophic areas, members of this group do not usually show the
degree of habitat differentiation exhibited by most other phytoplankton
organisms. This is illustrated by the abundance of the group in southern Lake
Huron (Fig. 64A-H). Although there are seasonal fluctuations in abundance, the
group tends to be remarkably evenly distributed throughout the area of study.
Crvptomonas, pyata
This species is apparently widely distributed in the upper Great Lakes
including northern Lake Huron (Schelske et_ al.. 1974). It was present in most
of our early May (Fig. 65A) samples from southern Lake Huron with relatively
little variability in abundance from station to station. In late May (Fig.
65B) population levels tended to increase in the inner Saginaw Bay stations and
at nearshore stations particularly in the western and southern sides of the
lake. A similar pattern was noted in the early June (Fig. 65C) samples with
the trend towards increase in nearshore stations extended to the Canadian
coast. This pattern had been somewhat modified by late June (Fig. 65D) when
high population levels were found in the southern sector of the Saginaw Bay
interface and southward along the Michigan coast, but only very low populations
at other stations sampled. This species had been reduced to a seasonal minimum
in abundance by the time the mid-July samples were taken (Fig. 65E) and
remained present in low and relatively uniform numbers throughout the rest of
the season (Figs. 65F-H).
flh.od.o-moD.a3 minuta var. nannoplanctica
Like Crvp_tomonas oyata this species is generally distributed throughout
the Great Lakes system. Although less abundant than £.. pygj.a it too was
present at most stations sampled thoughout the year in southern Lake Huron
(Fig. 66A-H). The primary distinction in their distribution pattern is the
fact that E. minuta var. nannoDlanctlpa showed a consistent tendency to be
least abundant in the Saginaw Bay interface waters and nearshore stations on
the Michigan coast and the most abundant particularly during June (Fig. 66D) at
offshore stations and stations near the Canadian coast.
266
-------
EflST TflUflS
GOOERICH
0
28 flPR - 3 MflT 74
ORT HURON
CRYPT
EflST Tl
ttGOOERICH
0
14-17 MflY 74
HURON
CflYPT
Figure 64. Seasonal abundance and distribution
trends of Cryptomonads. (continued)
-------
ERST TRHflS
0
4-8 JUN 74
GOOQUCH
'OfiT HURON
CRYPT
ERST TRHflS
ttGODERICH
0
17-21 JUN 74
WT HURON
CRTPT
Figure 64. (continued)
268
-------
EflSl TfiHflS
0
17-22 JUL 74
'ORT HURON
CRYPT
26-31 RUG
OPT HURON
CRYPT
Figure 64. (continued)
269
-------
EflST TflHflS
0
8-12 OCT 74
GOOERICH
IT HURON
CflYPT
EflST TflHflS J /
.. /J /
0
10-14 NOV 74
HURON
orrpT
Figure 64. (continued)
270
-------
ERST TRURS
0
28 RPR - 3 MRY 74
GOOOIICH
ft HURON
CNOVflTfl
ERST TRUAS
coocniCH
0
1U-17 MflY 74
HURON
CNOVflTP
Figure 65. Distribution of Crvptomonas ovptta.
(continued)
271
-------
CAST TflURS
H-8 JUN 74
.< BGOOOUCH
CNOVflTfl
CAST TAWS
0
17-21 JUN 74
GODWICH
Figure 65,
WT HUN*
(continued)
CNOVflTfl
272
-------
EAST TflMAS
GODOUGH
0
17-22 JUL 7H
IT HURON
CNOVOTA
COOCRICH
0
26-31 RUG 74
Hunan
Figure 65. (continued)
273
CNOVflTfl
-------
EAST TMWS
0
8-12 OCT 74
GOOOUCH
HURON
CNOVATfl
CAST TflHflS
BGODOUCH
0
10-14 NOV 74
nun*
Figure 65. (continued)
CNOVRTfl
274
-------
0
28 flPR - 3 MflY 74
IT HURON
RDMINUVN
ERST
ttGOOERICH
0
14-17 MflY 74
WT HUfWN
ROMINUVN
Figure 66. Distribution of Rhodopongs jnj.np.ta
var. nannppj.apfiTtlfia- (continued)
275
-------
GOOERICH
4-8 JUN 74
HURON
ROMINUVN
GOOEBICH
0
17-21 JUN 74
HURON
Figure 66. (continued)
276
ROMINUVN
-------
ERST TOURS
GOOERICH
0
17-22 JUL 74
HURON
ROHINOVN
GOCEfUCH
0
26-31 flUG 74
HURON
ROKINUVN
Figure 66. (continued)
277
-------
ERST
0
8-12 OCT 74
'OUT HURON
RDHINUVN
ERST THMflS
GOOERICH
0
10-14 NOV 74
HURON
Figure 66. (continued)
2T8
ROMINUVN
-------
28 flPR - 3 MflT 74
ttGOOERICH
0
14-17 MflY 74
HURON
OJNO
Figure 67. Seasonal abundance and distribution
trends of dinoflagellates. (continued)
279
-------
Pyrrophyta
Although the dinoflagellates are relatively rare in the Great Lakes
phytoplankton assemblages they may, because of the large size of certain
species, constitute a significant portion of the biomass. The ecological
affinities of most species is very poorly known and most appear to be erratic
in their distribution, although this may be complicated by their relative
rarity in most phytoplankton assemolages. In southern Lake Huron
dinoflagellates were relatively abundant at a group of stations in the
northerly sector of the Saginaw Bay interface during early May (Fig. 6?A) but
were noted at only a few stations south of Saginaw Bay. By mid-May (Fig. 6?B)
'-h_3 pattern had changed in that the group was absent from most of the inner
stations in the Saginaw Bay interface, but found at scattered stations
throughout the rest of the area sampled. The group reached its greatest
abundance and widest distribution during early June (Fig. 67C) but was reduced
in abundance by late June (Fig. 6?D) and remained at relatively low abundance
througnout the rest of the sampling period (Fig. 67E-H). During July (Fig.
67E) dinoflagellates were consistently present at stations in the southerly
sector of the Saginaw Bay interface but this pattern was not repeated in
succeeding months.
spp .
During most months sampled (Figs. 68A-H) members of tnis g«nus reached
detectable levels of abundance at stations in or near the Saginaw Bay interface
waters, with sporadic occurrences at stations or clusters of stations in the
rest of the lake. Maximum levels of abundance were reached in the early spring
ana the primary species involved was Peridinium aciculiferum which may become
quite aounaant in eutropnic areas. Although its numbers are relatively low in
Saginaw Bay it may contribute an appreciable part of the total biomass because
of its very large cells.
app .
This unusual small form greatly resembles Splrodinium pusjlluin var. minor
(Skuja, 1956). So far as we have been able to determine, this species has not
been reported from the Great Lakes and most previous reports of its occurrence
come from small laK.es ana ponds. The entity we are dealing with here is widely
distributed in southern Lake Huron. During early May (Fig. 69A) sizeable
populations were present at stations in the northerly sector of the Saginaw Bay
interface waters and at isolated stations along the U.S. and Canadian coasts.
By mid-May (Fig. 69B) abundance had been reduced and the only occurrences noted
were at stations in tne northerly and easterly sectors of the area sampled.
During early June (Fig. 69C) , however, relatively large aoundances of this
species were found at scattered stations througnout southern Lake Huron. These
populations had apparently collapsed by late June (Fig. 69D) and this taxon is
fouiia only at occasional scattered stations during the rest of the study (Fig.
280
-------
EflST
0
U-8 JUN 74
HURON
OINO
EflST TflMflS
0
17-21 JUN 74
HMWN
Figure 6?. (continued)
281
01HO
-------
ERST TflHflS
ttGOOERJCH
17-22 JUL 74
HURON
OINO
ERST TflHflS
0
26-31 flUG 74
HUBON
Figure 6?. (continued)
282
ICH
OINO
-------
0
8-12 OCT 74
teGOOERICH
HURON
OINO
EAST TflHRS
0
10-1U NOV 7U
HURON
Figure 6?. (continued)
OINO
283
-------
0
28 RPR - 3 MflY 74
HURON
PERIO
BGODERJCH
0
14-17 MflT 74
i
HURON peniO
Figure 68. Distribution of Peridj.nj.uro spp.. (continued)
-------
EPS* TAHRS
_ jttGOOERICH
0
4-8 JUN 74
HURON
PERID
ERST TflHflS
17-21 JUN 74
COCBUCH
HURON
Figure 68. (continued)
ratio
285
-------
ERST TflKfiS
0
17-22 JUL 74
ttGOOOUCH
HURON
PQUO
BUST
0
26-31 RUG 74
gGODDUCH
HURON
PQIIO
Figure 68. (continued)
286
-------
EBST TflHfiS
GOOOUCH
0
8-12 OCT 74
HURON
ratio
DOT TWAS
ttoooeniCH
0
10-14 NOV 74
\
HURON
Figure 68. (continued)
ratio
287
-------
0
28 RPR - 3 MflY 74
GODERICH
\ _
#1=OR7 HURON
SDPUSVMQ
0
14-17 MflY 74
'ORT HURON
8 GODERICH
SDPUSVMQ
Figure 69. Distribution of Spirodinium sp..
(continued)
-------
ERST TflWfiS
0
4-8 JUN 74
l# GODERJCH
'ORT HURON
SDPUSVMQ
CODERICH
17-21 JUN 74
SDPUSVMQ
Figure 69. (continued)
289
-------
ERST TfiHflS
GOOERICH
0
17-22 JUL 74
n HURON
SDPUSVMQ
EflST THWflS
0
26-31 RUG
m HURON
Figure 69. (continued)
290
.ICH
SOPUSVMQ
-------
ERST TflWRS
0
8-12 OCT 74
CODERICH
ORT HURON
SDPUSVMQ
EflST TfiWflS
0
10-14 NOV 74
'ORT HURON
Figure 69. (continued)
291
CODERICH
SDPUSVMQ
-------
EflST TflNRS
0
28 RPR - 3 MflT 74
GOOERICH
HURON
FLSPP
EflST TflHfiS
GODtRICH
0
14-17 MflY 74
HURON
FLSPP
Figure 70. Seasonal abundance and distribution
trends of microflagellates. (continued)
292
-------
DOT Tl
GOOERICH
0
4-8 JUN 74
HURON
FT.SPP
ERST TflHflS
0
17-21 JUN 74
Figure 70.
HURON
(continued)
FL3Pf
293
-------
0
17-22 JUL 74
HURON
FLSPP
1 1 1 *A
ttGOOEBICH
0
26-31 RUG 74
HURON
FUSPf
Figure 70. (continued)
29 h
-------
ERST TfiHfiS
GOOERICH
0
8-12 OCT 74
HURON
FtSPP
GOOBUCH
Figure 70. (continued)
10-14 NOV 74
FLST?
-------
Microflagellates
This is a composite category comprised of small haptophytes and
chrysophytes which cannot be satisfactorily identified at the specific level.
Although relatively abundant in southern Lake Huron it is probably
quantitatively less important than some of the other flagellate groups such as
much larger dinoflagellates and cryptomonads. The overall distribution of this
group was remarkably stable during the period of our study. Appreciable
populations were found in most stations sampled during May (Fig. 70A-B).
Maximum abundance was found during early June (Fig. 70C) and this was followed
by an apparent collapse in late June (Fig. TOD). Population levels recovered by
mid-July (Fig. 70E) and remained quite stable during the rest of the study
(Fig. 70F-H).
VERTICAL DISTRIBUTION OF PHYTOPLANKTON AT MASTER STATIONS
In general, there was remarkably little consistency in the vertical
distribution of phytoplankton at the southern Lake Huron master stations
studied either at the given station over time or between stations during a
given cruise. In most cases (Fig. 71) greatest phytoplankton abundance was
found at some depth below the surface, however, there appeared to be relatively
poor correlation with the thermal structure. Pronounced subsurface peaks
occurred during homothermous conditions particularly during cruises 7 and 8,
and during thermal stratification. At station 25 the spring assemblage maximum
appeared to move downward through the water column to thermocline depths by the
initiation of stratification but no such trend was observed in the other
stations studied. Interpretations of the vertical distribution information is
considerably complicated by the possible presence of senescent populations from
Saginaw Bay sinking through the column.
Of the major physiological groups, diatoms (Fig. 72) tended to have the
most uniform vertical distribution, particularly during periods of homothermous
conditions. During stratification highest diatom abundance was generally found
at or below the thermocline, although very high population densities found at
station 60 during cruise 6 were restricted to the epilimnion.
Somewhat surprisingly the vertical distribution of green algae (Fig. 73)
was markedly discontinuous prior to stratification. Although the abundance of
green algae was uniformly low during cruise 5, following the initiation of
stratification, large populations had developed in the surface waters at
stations 23 and 25 by the time cruise 6 samples were taken but remained low and
relatively uniform at station 60.
Although it might be expected that blue-green algae would concentrate near
the surface, this was clearly not the case in southern Lake Huron (Fig. 7^4).
Maximum abundance of this group occurred in the fall under isothermal
conditions and in only one case (station 23, cruise 7) was maximum abundance
found at the surface.
296
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302
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Prior to the establishment of stratification, population densities of
phytoplankters in the division Chrysophyta were remarkably uniform with depth
(Fig. 75). Population densities of this group reached their minimum during
cruise 5 following the establishment of a stable stratification. During cruise
6 maximum population densities were found in the thermocline regions at station
23, but this group was present only in small numbers at station 25 and
virtually absent at station 60. During cruise 7, although the water column
sampled was essentially isothermal, peak abundance of chrysophytes was found at
20 m depth at stations 23 and 25, with a remarkably large peak at station 25
being composed almost exclusively of ChrvsosDhaerella longispina.
During cruise 1 cryptomonads (Fig. 76) were strikingly more abundant in
near surface waters than other depths sampled. Population densities of this
group were remarkably similar at all depths sampled during cruise 2. During
cruises 3, 4 and 5 minimum population densities usually occurred at the surface
at the master station sampled with maximum densities occurring at depths of
either 5 or 10 m. During cruise 6, a large population maximum was found at the
depth of 20 m at station 23, although the other stations sampled did not show
this trend. During cruises 7 and 8, the population densities of this group
were again relatively uniform with depth. During these cruises, maximum
abundance was again generally found in the surface samples although these peaks
were not as pronounced as they had been during the spring.
Due to the low population densities found in the offshore waters from Lake
Huron detectable quantities of dinoflagellates (Fig. 77) were generally found
only at 5 and 10 m depths at the stations sampled.
Considering the composite nature of the group the distribution of
microflagellates (Fig. 78) was remarkably similar at all the stations and dates
sampled in southern Lake Huron. In the majority of instances these organisms
tended to be strongly concentrated at a depth of 5 m. The main exception to
this was at all stations sampled during cruise 4, and at stations 25 and 60
sampled during cruise 5. Although population densities varied in most other
samples these organisms were several times more abundant at the 5 m depth than
the other depths sampled. The reasons for this highly unusual depth
distribution pattern are obscure although some active type of depth regulation
is suggested by such remarkably stable patterns.
INTEGRATED FLORISTIC EFFECTS
Relation of Selec_ted___Species to Specific Chemical Parameters
It is evident that the phytoplankton flora of southern Lake Huron reacts
to various chemical and physical conditions and gradients within the
environment in a complex manner. While nutrient control of phytoplankton
growth is an undeniably important factor in controlling the patterns of
distribution observed, it is also clear that certain populations react to the
conservative ion content of their environment and the temperature regime. The
effects of these directly observable parameters, although complicated by
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,47, "^."M; 3=,-3> ,oq ST=VIOO!"''>
STRAT = r,otlTcr :7
> 37 rip" nF 17 ll.47FLOSflO V« . 05. CL
47FL0540
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5.2200 6.3600 7.5000 S.6^00 9. 7800 CL
5.700u 6.^300 3.0700 °.2100 10.350
Figure 79- Correlation plots of absolute abundance (cells/ml) of
Aphanizomenon flos-aauae vs. chloride (mg/1).
307
-------
. PT STP AT=rpui<;c ;7
N= 37 ri)T HE T7 1 ] .AZFLTSSn VS.
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106.61 lcl.?3 l°5.96 240.AR 2^5.10
Figure 80. Correlation plots of absolute abundance (cells/ml) of
Aphanig;omenon flos-aauae vs. nitrate (mg/1) .
308
-------
historesis effects, usually can be evaluated by relatively straightforward
objective analysis if sufficient data is available. In most instances it is
much more difficult to evaluate more subtle biotic interactions, particularly
the characteristics of certain populations which render them more or less
subject to losses through sinking, predation or parasitism.
In the case of certain populations abundant in southern Lake Huron the
factors controlling distribution appear to be relatively straightforward. For
instance, Aphanizomenon flos-aciuae is a population which appears to be largely
restricted to water masses derived from Saginaw Bay. As would be expected its
abundance is highly correlated with high levels of chloride and total
phosphorus, and negatively with nitrate concentration (Table 17; Fig. 79, 80).
In the case of this species it may be speculated that it has competitive
advantage in waters rich in phosphorus and relatively depleted in nitrate and
silicon, since it is known to be capable of fixing atmospheric nitrogen and
does not require silicon for growth. It is also quite possible that the growth
of this species is in some way facilitated by relatively high conservative ion
levels, as might be inferred from the high correlation with chloride. Such
causality arguments are somewhat weakened by inspection of similar data for the
same cruise for undetermined green filament number 5 (Table 18; Fig. 81, 82).
Although the physiological capabilities of this entity are entirely unknown, it
is extremely doubtful that it is capable of fixing atmospheric nitrogen. It
however shows nearly identical high positive correlations with chloride and
total phosphorus and negative correlation with inorganic nitrogen
concentration. It may well be that apparent similarity in response of these
two species evolves from the fact that they are both generated under the
conditions present in Saginaw Bay, and that neither population is subject to
significant sinking or grazing losses as they are transported into southern
Lake Huron. Hence their behavior is essentially similar to that of the
conservative chemical ion species. In this case it is entirely possible that
the apparently high negative correlation with nitrate values of these two
entities may result from opposite causality (i.e. the growth of green filament
number 5 and similar populations may result in the depletion of nitrate in
water masses where they are abundant and this, in turn, may confer competitive
advantage on nitrogen-fixing poulations such as Aphanizomenon flos-aauae).
The situation with other populations may be even more complex. For
instance, Fragilaria capucina is a species which has been observed to increase
greatly in abundance in shallow embayments and nearshore areas which have been
significantly eutrophied. However it apparently does not invade the offshore
waters of the Great Lakes to any significant extent. On the basis of data from
cruise 3 (Table 19; Fig. 83) populations of this species show moderately high
positive correlation with the chloride level, although positive correlation to
total phosphorus and low negative correlations with inorganic nitrogen and
soluble silicon. Goad et al. (1977) have shown that this species has a
relatively thick siliceous wall compared to taxa which are euplanktonic in the
Great Lakes. It may well be that the apparently weak correlation of the
occurrence of this species with chemical factors results from high sinking loss
rates inherent in its morphology and cellular constitution.
309
-------
TABLE 18. CORRELATION MATRIX OF GREEN FILAMENT SP. #5
AND MACRONUTRIENT VALUES FOR CRUISE 7 AT 5 METER
DEPTH. N = 37
Cond.
Cl
N03
SK>2
TP04
GRFILS
1.0000
.7260
-.7579
-.3993
.6943
.7629
Cond.
1.0000
-.9062 1.0000
-.4705 .3879 1.0000
.8388 -.8319 -.4140 1.0000
.9229 -.9295 -.4316 .8765
Cl N00 SI00 TPO.
3 24
1.0000
GRFILS
TABLE 19.
CORRELATION MATRIX OF FRAGILARIA CAPUCINA
AND MACRONUTRIENT VALUES FOR CRUISE 3 AT 5 METER
DEPTH. N = 43
Cond.
Cl
N03
SI02
TP04
FRCAPU
1.0000
.8209
.3625
-.3001
.4562
.5773
Cond.
1.0000
.0771 1.0000
-.2538 -.1382 1.0000
.4857 .0994 -.1174 1.0000
.7350 -.1034 -.1203 .2963
Cl NO,, SI00 TPO,
3 24
1.0000
FRCAPU
310
-------
Sr»TTFR PLOT STRAT=r,»UI5F:7
N« 37 OUT OP V 47.r,R':!Lt;o = y?. 95.CL
GRFILSP?
7*56.0
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3778.0
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932.01 *
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+ 4. ». * 4. * t », 4. » ,. ». «. 4 f ». + 4. 4.
5.2200 6.3600 7.5000 S.6400 9.TPOO CL
5.7
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\i= IT HIT
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0.
151.71
?<-,?. 73 ^TjjfiT-r
7 i 0 . « 1 ?oc.lo'
Figure 82. Correlation plots of absolute abundance (cells/ml) of green
filament sp. #5 vs. nitrate (mg/1).
312
-------
lOO.FTAP'JCI V1:.
1013.-' +
901.0"'
Tpp.43 t
0. ** **??*? *?*«*
4. ---- > ---- 4. ---- +
5. 1210 6
4. ---- 4. ---- 4- ---- 4-
10. S3*) CL
Figure 83. Correlation plots of absolute abundance (cells/ml) of
Fraeilaria caoucina vs. chloride (mg/1).
313
-------
TABLE 20. CORRELATION MATRIX OF CYCLQTELLA COMENSIS AND
MACRONUTRIENT VALUES FOR CRUISE 6 AT 5 METER DEPTH
N = 44
Cond.
Cl
N°3
sio2
TPO.
4
CYCOME
1.0000
.3763 1.0000
-.1006 .0044
.1177 .0663
.5926 .7326
-.2507 -.2172
Cond. Cl
1.0000
-.4415 1.0000
-.0793 .1417 1.0000
.6194 -.7871 -.2430 1.0000
NO,, SI09 TPCV, CYCOME
TABLE 21. CORRELATION
MACRONUTRIENT VALUES
MATRIX OF CYCLQTELLA QCELLATA AND
FOR CRUISE 4 AT 5 METER DEPTH
N = 42
Cond.
Cl
N03
sio2
TP04
CYOCEL
1.0000
.9189 1.0000
.3894 .5044
-.7769 -.7649
.8672 .8746
-.6319 -.5403
Cond. Cl
1.0000
-.4989 1.0000
.3283 -.7795 1.0000
-.3780 .7328 -.5595 1.0000
N00 SI00 TPO. CYOCEL
3 24
314
-------
SC«TTEP PLOT
N= ittt OUT OF 4i IOO.CYCOMENS VS. =»R.SILICA
CYCOMENS
1508.0 * *
* *
1340.A +
1172.0
1005.3
837.78 «
670.22
502.67 t-
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*
335.11 * *
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*
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*
0. + * *
< ---- + ---- 1 ---- « ---- + ---- * ---- * --- «. ---- « ---- 4- ---- + ---- + ---- «. ---- f ---- + ---- + ---- + ---- + ---- «.
.*0000 .59778 . 70556 .P933T 1.1°11 SILICA
.^966"' .89i4i 1.092? 1.2900
Figure 84. Correlation plots of absolute abundance (cells/ml) of
Cvclotella pppepsris vs. silica (mg/1).
315
-------
335.11 +2
3
*
167.56 +»
2
0.
0. T4.333 148.67 ??3.00 2<57.33 NITRATE
37.16"7 111.50 1*5.93 ?f>0,l-> 334.50
Figure 85. Correlation plots of absolute abundance (cells/ml) of
Cvclotella coroensis vs. nitrate (mg/1).
316
-------
The occurrence pattern of Cyclotella comensis in the Great Lakes is
something of an enigma. Although this species was previously recorded from the
offshore waters of Lake Superior (Schelske et_ aJ^. , 1972) and northern Lake
Huron (Schelske _et _al., 1974; Lowe, 1976) its distribution range and abundance
has apparently increased considerably in recent years. It is now present in
Lake Michigan, where it was previously either absent or present in only very
small abundance (Stoermer & Yang, 1969), and during our study occurred in bloom
proportion at several stations in southern Lake Huron. In southern Lake Huron
blooms of this species were usually associated with auxospore formation during
the late summer which in our experience is highly unusual for most planktonic
diatoms. Inspection of data from cruise 6 (Table 20; Fig. 84, 85) shows that
this species has a relatively strong positive correlation with nitrate level.
Conversely it shows negative correlation with other nutrient and conservative
ions. It is particularly interesting that this species shows a high negative
correlation with dissolved silicon, although this nutrient is known to be an
essential requirement for its growth. These data, plus the highly unusual
occurrence pattern of this species in the Great Lakes in recent years, lend
some credence to the hypothesis that inorganic nitrogen levels in the offshore
waters of the upper Great Lakes are in fact increasing. It would also tend to
indicate that this species is particularly efficient in its utilization of
silicon at low levels and may become an increasingly important element of
summer phytoplankton assemblages in the upper lakes. Our data (Fig. 85)
suggest that this species has an absolute requirement for nitrate levels in
excess of 200 yg/fc, but when this requirement is supplied, it can tolerate
silica levels of less than .5 mg/£ (Fig. 84).
The distribution of Cyclotella ocellata, another species with apparent
oligotrophic affinites, is quite different with respect to major conservative
and nutrient ions (Table 21; Fig.86). Unlike ^C. comensis this species shows
relatively high positive correlation with increasing levels of dissolved
silicon, but it is negatively correlated with other major nutrients and with
chloride. Previous studies in northern Lake Huron (Schelske _et_ a_l. , 1976)
suggest that C_. ocellata is most abundant at or below the thertnocline. This
suggests that it has a relatively high silicon requirement but is able to
fulfill this limitation by adaptation to growth under low light conditions. As
will be discussed later, significant occurrences of this species in southern
Lake Huron during stratification appear to be associated with upwelling
incidents.
Dimensional Ordination Analysis Utilizing Principal Components
A number of multivariate statistical procedures are available to aid in
evaluating properties, in this case floristic associations, emergent from the
complex interactions of the basic physical and chemical properties of the given
system. In this case, we have chosen to utilize principal components
analysis. For each cruise, we have plotted the regions of floristic similarity
in southern Lake Huron derived from this analysis, and in addition have
prepared a tabular listing of the species particularly characteristic of the
regions defined. The analytical procedures used are essentially similar to
those utilized by Schelske et al. (1976) and Stoermer and Ladewski (1978).
317
-------
R v=100,9P>
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During cruise 1 (Fig. 87; Table 22) six fairly well defined phytoplankton
associations were present in southern Lake Huron. Three of these associations,
labeled A, C, and E, were associated with nearshore stations sampled. Although
these stations had in common relatively high abundance of certain predominately
benthic taxa such as Amphora oyalis var. pedj._GUlus. the predominant planktonic
taxa present were different in each region. Region A was dominated by
oligotrophic to mesotrophic species such as Rhodomonas m.inu_t$ var.
nannopIanG.y.ca. S-tephanodiscus transilvanicus. Synedra fillformis. and
Tabellaria flocculosa. Region C, on the other hand, was characterized by much
greater abundance of species with eutrophic affinities such as piatQloa teriuB
var. oaohycephala. Fragi.Tlar;la capucjlna. MeJ.pLsira grapulata. and StephanQcliscus
binde.ran.u3. Region E was dominated by a different set of taxa with mesotrophic
to eutrophic affinites including very high abundances of Melosj.ra islandlca.
Nitzschia dissipa_ta. several of the smaller species of Stephanpdj.sc_us. and
Surirella anpustata. Region B, which encompasses a number of stations in the
Saginaw Bay interface waters and southward along the Michigan coast, contained
a mixture of species with primarily eutrophic affinities but was mostly
distinguished by a very high abundance of microflagellates. Region D was
characterized primarily by the occurrence of a number of species with
oligotrophic or mesotrophic affinities, generally in low abundance. This
region is distinguished from Region D1 primarily by the greater abundance of
species such as pinobrvon divereens and Fragilaria intermedia var. fallax in
Region D1.
During cruise 2 (Fig. 88, Table 23) a somewhat different floristic pattern
was present. A large number of stations in the Saginaw Bay interface waters
and southward along the Michigan coast had floras dominated by species with
eutrophic affinities such as Diatoma terxue var. pachvcephala. F.ragj.j.aria
crotonensjLs. Gloeocvstis plank tonic a. _Mg.j.p,3Jlrg granulata. Qscillatoria re.tzii.
Scenedesmus juadricauda. and Stephanodiscus binderanus. Region A was
particularly characterized by very high populations of Dlatoma tenue
var. pachvcephala. and maximum abundance of microflagellates and Fragilaria
capucLina. Region A1 contained similar species but had a greater admixture of
primarily benthic taxa such as Fragilaria .pinna t a. and more mesotrophic
euplankters such as Apapystls inserta. Rhizosolenj.a gracilis. and Svnedra
oste-Q_f_eldii. At this time most offshore stations labeled as Region B on the
map were characterized by relatively low abundance of oligotrophic and
mesotrophic populations. Region C, along the Canadian coast, was characterized
by high abundance of some of the more eurytopic plankton dominants such as
Asterionella formosa. Cvclotella _3telligera. Mej-osira islandica. and
Stephanodiscus aloinus. together with certain species such as Cvclotella
roeneghiniana. Stephanpdispus han^zschii. Stephanodiscus minutus. S. subtilis.
and S.urlre11a angustata. which usually occur under more eutrophic conditions.
Stations in the area labeled C1 had a qualitatively similar flora to Region C,
but certain species such as Crucigenj.a au_adra_ta. Cvclotella opej.j.&.ta.
Rhizosolen;La graclljis. and Svnedra fj.j.j.fprmis were relatively more abundant.
This flora tended to grade into that found in Region B in the area labelled
BC1, but this region was also distinguished by relatively high population
densities of Chrvsosphaerella longispina and ChrYSQCQCCus dokidophorus.
323
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During cruise 3 (Fig. 89; Table 24) the floristic pattern in southern Lake-
Huron was essentially similar to that found during cruise 2 but somewhat more
complex. Stations within Region A were characterized by the presence of
relatively high numbers of benthic taxa, such as Amphora ovalis var. pediculus,
and Fragilaria pinnata, together with certain flagellate species such as
Cryptomonas ovata and Chrysosphaerella longispina. Region B was characterized
by relatively high abundance of species usually associated with eutrophic
conditions such as Anabaena flos-aquae, A_. subcylindrica, Aphanizomenon
flos-aquae, Fragilaria capucina, Gloeocystis planctonica, and Mougeotia sp..
Region Bl was floristically similar, however it had a greater abundance of
species such as Diatoma tenue var. pachycephala and Ulothrlx sp.. Region C was
characterized by relatively high abundance of certain benthic species such as
Achnanthes minutissima together with some of the more eutrophic plankton
dominants such as Melosira granulata and Oscillatoria bornetii. Immediately
adjacent Region D had a markedly different flora which was dominated by
eurytopic or oligotrophic species such as Asterionella fortnosa, Cyclotella
ocellata, Rhizosolenia eriensis, Synedra filiformis, and Tabellaria
fenestrata. At this time, offshore stations within region E were mainly
characterized by the presence of populations of small diatoms such as
Cyclotella stelligera and small flagellates such as Rhodomonas minuta var.
nannoplanctica. The region labeled BE was apparently a mixing zone between the
open Lake Huron and Saginaw Bay water masses, as it contains a mixture of the
species found in Region Bl plus substantial quantities of species such as
Crucigenia quadrata, Cyclotella comta, Cyclotella michiganiana, Dinobryon
divergens, and Fragilaria crotonensis which were also found in Region E. Region
F was defined primarily on negative characteristics and lacked species
dominance patterns displayed by any of the other regions. The region labeled
FE appeared to be a mixture of floristic associations found at nearshore
stations along the Canadian shoreline and populations found in the open waters
of Lake Huron. It was additionally characterized by relatively high abundance
of Chrysosphaerella longispina. Station 6, labeled G on the map, was
distinguished from adjacent stations by high abundance of some of the small
Stephanodiscus species such as j^. minutus and _S_. subtilis.
During cruise 4 (Fig. 90; Table 25), the influence of the Saginaw Bay
water mass was apparently less extensive than it had been during the previous
sampling period. The region labeled A contained a very high abundance of
species associated with highly eutrophic conditions such as Anabaena
flos-aquae, Aphanizomenon flos-aquae, Fragilaria capucina, Oscillatoria retz ii,
and Pediastrum boryanum. The region labeled Al had a substantially similar
flora but with a greater admixture of more mesotrophic taxa such as Anacystis
thermalis. Region A2 was likewise similar to Regions A and Al but had a greater
abundance of more eurytopic diatom species such as Synedra ostenfeldii. Region
B contained certain elements of the eutrophication-tolerant flora found in
Region A such as Anabaena flos-aquae. These species however were present in low
abundance and the flora of Region B was dominated by more eurytopic taxa such
as Cyclotella stelligera, Synedra filiformis, and Tabellaria flocculosa var.
linearis. Unlike Region B, Region C contained practically none of the species
associated with the Saginaw Bay water mass, and the flora of this region was
333
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dominated by species such as Chrvsosphaerella loneispina. Rhizosplenia
eriensis. Svnedra ulna var. chaseana. and Tabellaria fenestrata. none of which
is particularly tolerant of eutrophied conditions. Regions D and D1 were
characterized by low population densities and assemblages of species usually
intolerant of eutrophic conditions. Some of the characteristic populations in
Region D were species such as Crucigenia guadrata. Cyclotella pcella.ta.
Cvclotella stelligera. Dinobrvon divergens. and Rhpdpmopas minuta var.
nannoolapctica. Region D1 was distinguished from Region D primarily by the
greater abundance of species such as Anacvstis incerta. Cvclotella coroensis.
and Rhizosolenia gracilis. As in the previous sampling period, during this
cruise a series of stations along the Canadian coastline labeled E in the
diagram had a substantially different flora than the rest of the lake. Diatoms
were particularly abundant, and the flora at these stations contained both
significant quantities of primarily benthic taxa such as Achnanthes minutissiroa
and Amphora pya^is var. pediculus. as well as euplanktonic species tolerant of
elevated nutrient levels such as Melosira islandica. Stephanodiscus minutus.
and .S_. subtilis.
During cruise 5 (Fig. 91, Table 26), a number of stations along the north
Michigan coast labeled A in the diagram had a diatom dominated assemblage
containing primarily eurytopic species such as Asterionella formpsa. Cvclotella
comta. Fragilaria crotonensis. and Tabellaria fenestrata. together with a
number of species having more eutrophic affinities such as Fraeilaria caoucina.
and usually benthic taxa such as Frap;ilaria pinnata. The hypereutrophic
assemblage characteristic of Saginaw Bay dominated Region B where species such
as Anabaena 3UbCYlindrj.ca. Anacvstis cvanea. and Aphanizomenon flos-aauae were
particularly abundant. Certain elements of this flora were also found in the
region labeled B1, but this region also contained less eutrophication-tolerant
taxa such as Anabaena flos-aauae. Crypj-geDia auadrata. and Dinobryon
divergeps. Region C likewise had certain affinities to Region B1 since it
contained species in common such as Chodatella ciliata and pj.npbrypn driyergens.
but the flora of this region was dominated more by typical offshore summer
forms such as Anacvstis tbermalis and Cvclotella michjganiana. Stations within
the region labeled D appeared to reflect the influence of some nutrient
enrichment, possibly resulting either from upwelling or shoreline nutrient
discharge, since their floras contained both some of the typical offshore
phytoplankton dominants and species such as Melosira granulata. Stephanpdj.scus
minutus and g. subtilj.3. which generally occur under more enriched conditions.
The region labeled D1 contained a typical offshore assemblage dominated by
species such as Cvclotella stelligera and Rhodomonas minuta var. nannoplanctica.
Unlike the other cruises, during cruise 6 (Fig. 92, Table 27) the
immediate influence of Saginaw Bay appeared to extend northward. The flora of
Region A was dominated by blue-green algae such as Anabaena subovlindrica.
Anacvstis cvanea and Aphanizomenon flos-aauae. characteristic of hypereutrophic
conditions. This influence extended into Region A1 with the assemblages at
these stations containing more species with benthic affinities, and eurytopic
taxa such as Asterionella fprmosa and Chrysosphaerella lopgjspina. A large
sector of the lake labelled Region B contained an unusual assemblage dominated
by high abundance of Cvclotella comensis. but also containing certain species
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such as Pediastrum boryanuro generally associated with eutrophied conditions in
the Great Lakes. Region C had certain similarities to Regions A1 and B but
contained a greater abundance of mesotrophic blue-green species such as
Anabaena flos-aauae and Anacvstis thermalis. Region D also contained a flora
characteristic of silica depletion under midsummer conditions, but with a
greater abundance of species such as Anacvstis incerta. Crucigenia auadrata.
and RhodomopftS minuta var. nannoplanctica. During this cruise Region E
appeared to reflect the influence of upwelling. The flora within the primary
region was dominated by species such as Cvcj.otella pcellata. pj-PObrvon
divergens. Fragilaria crotonensJLS. Rhizosoj.enia eriensis. Tabellaria
fepestrata. and Tabellaria flocculosa var. linearis. Region E1 contained a
greater abundance of species such as Cvclotella corota. p.. michiganiana. and C.
stej-liaera. while Region E2 was distinguished primarily on the basis of high
population densities of microflagellates.
A somewhat more simple floristic pattern was present during cruise 7 (Fig.
93> Table 28). In this case the region labeled A contained the
diatom-dominated assemblage with species such as Asterionella formosa.
Cvclotella comta. C. michiganiana. and C. stelligera being prominent. As had
been the case at these stations in previous months, the flora also contained a
substantial number of primarily benthic species such as Amphora pyaj.j.3 var.
pedj-culus. Fragilaria pinnata. and F^ vaucheriae. Region B contained a typical
hypereutrophic assemblage. Although certain blue-green species such as
Aphanizomenon flos-aauae were still prominent, by this time a number of
fall-blooming diatom species, such as Actinocvclus pormanii fo. subsalsa.
Fragilaria capucj.na. and Mej.ps.ira granulata had also become prominent.
These elements in the flora were reduced in abundance at the stations in
Region B1 and blue-green algae such as Anabaena subcvlindrica and Apabaepa
cvanea were particularly abundant. All during this cruise assemblages at
offshore stations in Region C contained relatively large populations of species
like Chrvsosphaerella j.png^.3pj.na. Chrvsococcus dokidoohorus. Cvclotella
ocellata. and Gomphosphaeria lacustris. Stations in Region C1 were
distinguished from those in Region C primarily by having larger populations of
Dj-nobrvon divergens.
During cruise 8 (Fig. 9^, Table 29) a very complex pattern was present.
Region A contained assemblages composed of several primarily benthic diatoms, a
number of euplanktonic species tolerant of moderate nutrient enrichment, such
33 Fragilaria crotonensis. Melos^ra islapdjlca. and Tabellaria fenestrata. plus
a few green algae such as Crucigenia auadrata and Goj.enkinia radiata. plus
Dinobrvon divergens. Region A1 was distinguished from Region A primarily by
the greater abundance of species such as Cvclotella pcellata and Stepbanodiscus
aj.pj.nus. The flora of Region B was dominated by species usually occurring
under highly eutrophic conditions, such as Anapysl^j.s cvanea. Aphanizomenon
flos-aauae. and Fragilaria capucina. Assemblages at stations in Region C were
fairly typical of moderately disturbed offshore regions in the upper Great
Lakes, containing species such as Apacystj.3 thermaj.j.3. Gomphpsphaeria
lacustris. and Rhodomonas minutus. in moderate abundance. Region C1 was
distinguished from Region C primarily through the greater abundance of Oocvstis
356
-------
spp. The region labeled BC appeared to be a mixture of the floristic
assemblages found in the two primary regions. As had been the case in several
previous sampling periods, the region of the Michigan coast labeled D in the
diagram had a unique floristic composition. Assemblages in this region were
relatively rich in species like C₯OJ.ptella comensis and g.. stelligera. together
with Crvptomonas pya,ta and Anacvstis incerta. and benthic diatoms such as
Fragilaria vaucheriae.
357
-------
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360
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DISCUSSION
Based on the results of this study, it appears that the phytoplankton
flora of southern Lake Huron has been modified by anthropogenic inputs to a
greater extent than is generally realized. Although at any given sampling
period phytoplankton assemblages at offshore stations are generally dominated
by populations which develop under oligotrophic conditions, there is evidence
of nutrient stimulation of more tolerant populations, and the injection of
populations tolerant of extremely eutrophic conditions into the offshore
waters. Our results indicate that the areal extent of these effects is highly
seasonal, and it may well be that certain of the patterns observed during this
study result from transient meteorological events (Schelske _§£ _§!> 1974).
Unfortunately, the present data base does not allow evaluation of this source
of variability.
Because of the limited number of studies of the openwater phytoplankton
flora of southern Lake Huron, there is also a limited basis for evaluating
long-term chronic floristic effects of eutrophication. Those studies available
(Nichols j£ ai. , 1975, 1977; Schelske e& ji. , 1972, 197*0 indicate that the
waters of northern Lake Huron and Georgian Bay generally contain phytoplankton
assemblages more indicative of oligotrophic conditions. While local regions in
the northern part of the lake may show the effects of nutrient stress, they do
not appear to develop the populations tolerant of highly eutrophic conditions,
except in very local regions of southern Georgian Bay (Nichols .e£ j^. , 1977).
While some effect of chronic nutrient stress on southern Lake Huron may be
inferred from these apparent differences, direct comparison with historic
samples as has been done in Lake Erie (Hohn, 1969) and Lake Michigan (Stoermer
and Yang, 1969) is not possible.
In terms of the quasi-instantaneous effects directly addressable from our
study, it is clear that there are three primary areas of floristic modification
which have significantly different characteristics, and which vary appreciably
in the area of the lake effects. The floristic characteristics of these areas
are variable over the time period sampled in this study due ho seasonal
succession of the species involved. Although the apparent source regions are
consistent from cruise to cruise, the area of the effect is highly variable,
depending apparently on both the amount of input of nutrients and other factors
which may affect phytoplankton composition, and on the physical factors which
determine the subsequent dispersion of these materials into the main body of
Lake Huron.
As might be expected, most extensive and intensive modifications are
associated with Saginaw Bay. Populations developed within this area are
characteristic of extreme eutrophication and salinification, and are thus quite
clearly distinguished from assemblages developed in the open waters of Lake
Huron. As alluded to previously, the flora of this region contains a mixture
of populations, including those developed within Saginaw Bay proper and
dispersed into Lake Huron, and certain populations which develop in the mixing
zone between Saginaw Bay and Lake Huron proper. The areal extent, and direction
of the Saginaw Bay influence is highly variable, and apparently dependent on
361
-------
the circulation patterns in the bay and in main Lake Huron (Allender, 1975;
Danek and Saylor, 1977). Due to the rapid response of circulation patterns in
Saginaw Bay to wind stress, the dispersion of biological populations and
chemical materials from this source may be highly dependent on transient
meteorological events (Schelske et_ a_l. , 1974). For this reason the limited
number of sampling cruises undertaken during the course of this project may not
furnish a very complete assessment of the possible effects of this source on
southern Lake Huron. On the basis of the data available however, it appears
that the region most consistently affected is the area running southward from
Saginaw Bay along the Michigan coast. Only during the August cruise (Fig. 92)
did phytoplankton assemblages characteristic of Saginaw Bay extend northward
from the bay. The area of the affect appeared to extend beyond our sampling
array so that the full extent of northward excursion cannot be determined.
Nonetheless it would appear that most of the influences of discharge from
Saginaw Bay are found in southern Lake Huron rather than being distributed over
the entire lake. The areal extent of the Saginaw Bay influence in southern
Lake Huron is quite variable from cruise to cruise. During the mid-May and
early June cruises (Fig. 88, 89) while the lake is still under the influence of
the thermal bar, phytoplankton assemblage modification resulting from Saginaw
Bay discharge is restricted to stations along the Michigan coast, and appears
to move lakeward following the excursion of the spring thermal bar. The
furthest dispersal of material and populations from the bay appeared to occur
during July (Fig. 91) when the influence of the Saginaw Bay water mass extended
southeastward as far as stations 6 and 65 near the southern Canadian coast.
Somewhat surprisingly during November (Fig. 94) senescent populations
characteristic of the Saginaw Bay water mass were found at midlake station 66.
The influences of nutrient discharge on the Canadian coastline are both
less extensive and more seasonally variable. The largest area of affect was
found during the May and early June cruises (Fig. 88, 89) and appeared to be
controlled by a combination of maximum spring runoff from land sources and the
effects of the spring thermal bar. Phytoplankton assemblages at stations along
the Canadian coast were also quite strikingly different during the August
cruise (Fig. 92). This effect however appeared to be associated with upwelling
along the Canadian coastline during this period rather than the influence of
nutrients from shoreline sources. As discussed previously, the general pattern
of phytoplankton distribution during this cruise was different than all other
cases examined. The apparent excursion of the Saginaw Bay plume northward
combined with the apparent upwelling at stations along the Canadian coast
indicates that the surface waters of southern Lake Huron were being transported
in a northwesterly direction during this sampling period which is atypical of
the average case. Tt should also be noted that phytoplankton populations most
characteristic of the oligotrophic openwater stations in Lake Huron were
restricted to stations 21, 24, 25, and 54 during this cruise.
The other area of floristic modification noted during the study was in the
region of stations 14, 15 and 67. Although this pattern was less striking and
less consistent than those discussed previously, it was recurrent, which tends
to indicate a source of nutrient addition in this region. The greatest
apparent effect appeared during July (Fig. 91) when populations characteristic
-------
of this region extended as far south as station 64. This region was not
detectable during the mid-May cruise (Fig. 88) when any influence with sources
in this region were apparently overwhelmed by materials exiting Saginaw Bay
landward of the spring thermal bar and during August (Fig. 92) when, as
discussed previously, these stations were occupied by a water mass more
characteristic of the offshore waters of southern Lake Huron. The influence of
sources in this area thus appears to be less than the sources discussed
previously. The phytoplankton assemblages of southern Lake Huron are thus
reflective of an oligotrophic environment which is variably modified by
eutrophication. The primary difference between southern Lake Huron and other
areas of the Great Lakes which are undergoing eutrophication is in the nature
of perturbations arising from Saginaw Bay. In most areas of the Great Lakes,
changes in phytoplankton composition and abundance result directly from the
addition of nutrients and other materials. In southern Lake Huron this appears
to be the case at stations along the Canadian coast. The effects of materials
entering Saginaw Bay, on the other hand, are strongly modified by biotic
interactions within the bay. It appears that most of the nutrients entering
southern Lake Huron from Saginaw Bay are contained in phytoplankton cells. The
subsequent effect of this loading in southern Lake Huron is thus strongly
dependent on both the load carried by these populations and their subsequent
dispersal and fate in the lake. Our data indicate that certain of the
populations generated within Saginaw Bay are quite persistent and thus may be
transported over considerable distances in southern Lake Huron before they die
and the materials they contain are released. This is particularly true of
certain of the blue-green algal populations generated within Saginaw Bay.
These populations are apparently not subject to large losses from sinking
and/or grazing and persist in the near-surface waters for considerable periods
of time. The dispersion of these populations into the open waters of the lake
would appear to be of importance since they may store large quantities of
phosphorus as polyphosphate bodies. Many other populations, particularly some
of the larger diatoms, are apparently lost from water masses exiting Saginaw
Bay quite rapidly, and thus the materials entrained are either lost through
sinking or fairly rapidly recycled. Thus the ultimate effects of pollution
sources within Saginaw Bay on Lake Huron may be a function of not only the
biological productivity within the bay but also of the types of populations
which are produced. Our results indicate that it is conceivable, given the
right circulation conditions, that certain populations generated in Saginaw Bay
could reach nearly any part of southern Lake Huron. Under the specific
conditions examined in this study, it was demonstrated that these populations
do in fact reach midlake stations and stations along the southern Canadian
coast. Management strategies which minimize the loadings to Saginaw Bay thus
may be especially effective since they will not only reduce the total loading
to Lake Huron, but if sufficient to limit blue-green algal blooms, they may
also limit the dispersion of materials entering Saginaw Bay to the open lake.
363
-------
REFERENCES
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diffusion processses in Saginaw Bay, Michigan. Ph.D. Dissertation,
University of Michigan, Ann Arbor.
Beeton, A. M., S. H. Smith, and F. F. Hooper. 1967. Physical Limnology of
Saginaw Bay, Lake Huron. Great Lakes Fishery Comm. Tech. Rept. 12,
56 pp.
Belcher, J. H., E. M. F. Swale, and J. Heron. 1966. Ecological and
Morphological Observations on a Population of Cyclotella
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Danek, L. J. and J. H. Saylor. 1977. Measurements of the summer currents
in Saginaw Bay, Michigan. J. Great Lakes Res. 3: 65-71.
Davis, C. C. 1966. Plankton Studies in the Largest Great Lakes of the
World, with special reference to the St. Lawrence Great Lakes of North
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Drouet, F. and W. A. Daily. 1956. Revision of the coccoid Myxophyceae.
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Duthie, H. C. and M. R. Sreenivasa. 1971. Evidence for the eutrophication
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Hohn, M. H. 1969. Qualitative and quantitative analyses of plankton diatoms
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36k
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Huber-Pestalozzi, G. 1941. Das Phytoplankton des Susswassers. Die
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366
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APPENDIX I
SUMMARY OF PHYTOPLANKTON SPECIES OCCURRENCE IN THE NEAR-SURFACE WATERS
OF SOUTHERN LAKE HURON DURING 1974 SAMPLING SEASON*.
CYANOPHYTA ^
Agmenellucn quadruplica turn (Menegh . ) Breb .
Anabaena flos-aquae (Lyngb .) Breb .
Anabaena sp . SI
Anabaena sp, #2
Anabaena sp . #4
Anabaena subcylindnca Borge
Anacystis cyanea (Kutz.) Dr. and Daily
A. dimidiata (Kutz.) Dr. and Daily
A. incerta (Lemm.) Dr. and Daily
A. thermal is (Menegh .} Dr . and Daily
Aphanizomenon flos-aguae (L. ) Ral fs
Chroococcus dispersus var. minor G.M. Smi th
Coccochioris sp . #1
OsciLLatoria bornetn Zulcal
0 . 1 imne ti ca Lemm .
O. .retzii Ag.
Oscillator! a sp . ill
Oscillatoria sp . ff2
Oscillatoria sp . S3
Oscillatoria sp. £ 4
Oscillatoria sp. #5
Oscillatoria sp . #6
Schizotbrax calcicola (Ag.) Com,
Undetermined blue-green filament #1
Undetermined blue-green filament #2
ToLal for Division (26 species)
CHLOROPHYTA
Actinastrwn hantzschii Lag.
Ankistrodesmus faicatus (Corda) Ralfs
A. gel i fact um (Chod . ) Bourr .
Ankistrodesmus questionable sp .
Ankistrodesmus questionable sp . Si
Arikistrodesmus sp . #1
Ankistrodesmus sp . 62
Ankistrodesmus sp . #3
AnJcistrodes/nus sp . M
Ankistrodesmus sp . #5
Binuclearia eriensis Tiffany
Borodinella poJytetras Miller
9
Slides
2
45
2
1
1
35
13
2
67
110
75
45
2
80
131
7
98
2
1
1
50
13
2
21
5
1
1
It
11
2
1
1
8
185
4
5
2
1
Avc
Cells/nl
0.870
20.636
0.013
0.007
0.020
2.516
29.328
0.087
121.508
12.038
57.940
28.645
0.3U
90 .882
1.920
0.080
9.569
0.013
0.114
0.007
1.345
2.891
0.047
0.435
0.161
0.007
381.390
0.027
0.040
0.314
0.027
0.027
0.020
0.167
3.473
0.067
0.067
0.054
0.161
rage
% Pop
0.033
0.656
0.001
0.000
0.000
0.037
0.326
0.006
4.498
0.713
0.744
1.311
0.014
4 .541
0.133
0.002
0.274
0.001
0.001
0.000
0.038
0.112
0.001
0.012
0.005
0.00)
13.461
0.000
0.003
0.024
0.003
0.003
0.000
0.018
0.297
0.006
0.005
0.004
0.003
Maximi
Cells/ml
238.761
1989.674
2.094
2.094
6.283
211.534
2827.431
18.850
2722.712
190.590
2844.187
722.566
50.265
1466 .0 75
62.832
10.472
347.669
2.094
35.605
2.094
58.643
816.813
12.566
25.133
20.944
2.094
8.378
6.283
25.133
4.189
8.378
6.283
12.566
29.322
6.283
4.189
10.472
50.265
jm
% Pop
9.794
55.901
0.263
0.028
0.034
1.125
37.303
1.111
80.967
16.667
23.122
50.607
3.625
75 . 594
5.310
0.222
5.109
0.177
0.342
0.013
0.846
31.733
0.337
0.694
0.653
0.218
0.069
0.353
2.160
0.556
0.844
0.096
1.695
2.778
0.625
0.501
1.389
0.943
*Summary is based on all 5-m samples analyzed. Summary includes the totax
number of samples in which a given taxon was noted, the average population
density (cells/ml), the average relative abundance (% of assemblage) , the
maximum population density encountered (cells/ml), and the maximum relative
abundance (% of assemblage) encountered. (continued)
367
-------
APPENDIX I (continued)
# Average
Botryococcus braunii Kutz.
Characium limneticum Lemm.
Chodate.Ua ciliata (Lag.) Chod.
C. citriformis Snow
C. subsalsa Lemm.
CJosterium aciculare T. West
CJosteriun? sp. //I
Coeiastrum njicroporum Nag.
C. reticulatum (Dang.) Senn
Coelastrum sp. #1
Cosmar-ium bioculatum Breb .
C. botrytis Menegh.
C. depressum (Nag.) Lundell
C. geometric var. suecicum Borge
C. Jaeve var. distentum G. S. West
Cosmarium questionable sp. //I
Cosmarium sp . //I
Crucigenia irregularis Wille
C. guadrata Morren
E-ZaJcatothrix gelatinosa Wille
Eutetramorus questionable sp . //I
Franceia droeschen (Lemm.) G. M. Smith
Gloeocystis planctonica (W. and W.) Lemm.
Golenkinia radiata (Chod.) Wille
Kirchneriella lunans (Kirchn.) Moebius
Kirchneriella sp . #1
Mougeotla sp . #1
Nephrocytium agardhianum Nag.
Oocystis questionable spp.
Ped-iastrum biradiatum Meyen
P. fooryanum (Turp.) Menegh.
P. duplex Meyen
P. duplex var. clathratum (A. Braun) Lag.
P. duplex var. reticula turn Lag.
Pediastrum sp . #1
Pediastrum spp.
Pediastrum tetras (Ehr.) Ralfs
Pnacotus lentlculans (Ehr.) Stein
C>uadngu-Za lacustris (Chod.) G. M. Smith
Scenedesmus abundans (Kirch.) Chod.
S. acuminatus (Lag.) Chod.
S. acutus fo. alternans Hortob.
5. acutus f o . costu-Zatus (Chod.) Uherkov.
Slides
5
2
26
4
1
2
2
30
1
1
14
9
18
9
1
1
13
15
65
1
24
2
190
63
1
2
108
7
196
2
9
6
3
1
1
1
3
1
2
1
3
1
1
Cells/ml
2.978
0.013
0.488
0.040
0.007
0.013
0.013
2.851
0.375
0.054
0.134
0.120
0.154
0.074
0.007
0.007
0.107
1.586
9.555
0.013
1.084
0.013
41.339
0.629
0.007
0.120
9.388
0.268
15.109
0.120
2^101
0.937
0.803
0.087
0.020
0.054
0.161
0.147
0.080
0.027
0.107
0.054
0.054
% Pop
0.127
0.001
0.038
0.004
0.000
0.001
0.001
0.128
0.007
0.000
0.013
0.003
0.008
0.005
0.000
0.000
0.006
0.115
0.586
0.001
0.080
0.001
2.487
0.064
0.000
0.001
0.280
0.048
0.990
0.004
0.034
0.024
0.036
0.003
0.000
0.000
0.005
0.003
0.005
0.001
0.002
0.001
0.003
Maximum
Cells/ml
335.103
2.094
39.793
4.189
2.094
2.094
2.094
87.965
117.286
16.755
8.378
12.566
8.378
4.189
2.094
2.094
4.189
134.041
159.174
4.189
29.322
2.094
1172.860
8.378
2.094
33.510
165.457
33.510
115.192
25.133
259.705
83.776
142.419
27.227
6.283
16.755
33.510
31.416
16.755
8.378
16.755
16.755
16.755
% Pop
26.144
0.242
1.597
0.893
0.139
0.258
0.177
4.614
2.042
0.106
1.429
0.242
0.568
0.714
0.080
0.017
0.367
10.440
9.302
0.236
7.639
0.220
54.310
2.424
0.065
0.211
3.571
9.697
10.976
0.988
4.038
3.396
4.219
1.080
0.126
0.142
1.602
0.220
1.416
0.287
0.450
0.292
0.977
(continued)
368
-------
APPENDIX I (continued)
# Average
Scenedesmus armatus (Chod.) G. M. Smith
S. armatus var. ioglariensis Hortob.
S. bijuga (Turp.) Lag.
S. caranatus (Lemm.) Chod.
S. denticulatus var. linearis f o . costato-granula tus
(Hortob.) Uherkov.
S. dent-iculatus Lag.
S. dinvrphus (Turp.) Kutz.
S. longus Meyen
S. opo-Z-iensis var. aculeatus Hortob,
S. opoliensis P. Richt .
S. guadricauda var. longispina f o . granuJatus Uherkov.
S. quadricauda (Turp.) Breb .
S. guadncauda var. longispina (Chod.) G. M. Smith
S. guadracauda var. guadrispina (Chod.) G. M. Smith.
S. semper VJ rens Chod.
S. serratus (Chod.) Bonn.
Scenedesmus sp . //I
Scenedesmus spmosus Chod.
Scenedesmus spp .
Selenasiium sp. #1
Sphaerocyst-is scnroeteri Chod .
Staurastrum paradoxum Meyen
Staurastrum sp . ft
Staurastrum sp . #3
Staurastrum sp. //4
retraedion minimum var. apiculato-scorbiculatum (Reinsch,
La;,. ) Skuja
Tetraedron minimum (A. Br.) Hansg.
T. regulars Katz.
Tetraedror. sp. //I
Tetrallantos Jagerheimii Teiling
Tetrastrum staurogeniaeforme (Schroeder) Lemm.
Vlothrix sp. Itl
Undetermined green colony
Undetermined green colony sp . #1
Undetermined green filament #1
Undetermined green filament #2
Undetermined green filament #3
Undetermined green filament #4
Undetermined green filament #5
I'r.diterminea green filament spp.
Undetermined green individual
Total for Division (96 species)
Slides
6
1
35
1
1
8
1
1
1
7
1
42
1
20
1
14
1
12
25
1
1
27
7
2
1
10
58
2
1
1
1
5
11
1
1
2
4
1
198
1
8
Cells/ml
0.161
0.027
1.258
0.027
0.107
0.375
0.027
0.054
0.027
0.468
0.013
2.094
0.054
0.763
0.013
0.535
0.040
0.348
1.191
0.007
0.248
0.234
0.067
0.013
0.013
0.074
0.957
0.013
0.007
0.107
0.054
0.937
0.803
0.027
0.047
0.261
1.566
0.013
667.756
0.033
0.261
777.071
% Pop
0.007
0.001
0.051
0.001
0.001
0.016
0.000
0.002
0.000
0.005
0.000
0.054
0.001
0.014
0.000
0.012
0.000
0.007
0.030
0.000
0.004
0.009
0.001
0.001
0.000
0.005
0.047
0.001
0.000
0.015
0.002
0.035
0.066
0.004
0.003
0.015
0.115
0.002
14.139
0.001
0.019
20.172
Maximum
Cells/ml
8.378
8.378
29.322
8.378
33.510
25.133
8.378
16.755
8.378
37.699
4.189
108.908
16.755
46.077
4.189
33.510
12.566
20.944
52.360
2.094
77.493
8.378
6.283
2.094
4.189
4.189
41.888
2.094
2.094
33.510
16.755
142.419
67.021
8.378
14.661
71.209
257.610
4.189
35309.383
10.472
43.982
% Pop
0.572
0.168
1.852
0.344
0.211
1.597
0.156
0.664
0.053
0.362
0.026
1.575
0.292
0.840
0.035
0.798
0.080
0.858
1.043
O.OJ2
1.386
0.446
0.075
0.153
0.057
0.508
1.338
0.247
0.017
4.611
0.679
8.028
8.036
1.278
0.826
4.014
17.706
0.525
92.383
0.430
2.178
(continued)
369
-------
APPENDIX I (continued)
BACILLARIOPHYTA
Achnanthes a f finis Grun.
A. biasa] ettiana (Kutz.) Grun.
A. clevei Grun.
A. clevei var. rostra ta Hust.
A. exigua Grun.
A. exigua var. heterovalva Krasske
A. hauckiana var. rostrata Schulz
A. lanceolata (Breb.) Grun.
A. lanceolata var. dubia Grun.
A. lanceolata var. elliptica Cl .
A. linearis (Win. Smith) Grun.
A. linearis f o . curta H. L. Smith
A. microcephaJa (Kutz.) Grun.
A. minutissima var. cryptocephala Grun.
A. minutissima (Kutz.)
A. oestrupi (A. Cl.) Hust.
A. pinnata Hust.
Achnanthes questionable sp . //I
Achnanthes sp. ill
Achnanthes sp . 'HO
Achnanthes sp . #16
Achnan thes sp . //1 7
Achnanthes spp .
Afiiphipleura pellucida Kutz.
Amphora fonticola Maill .
A. neglects Stoorm. and Yang
A. ovalis var. gracilis (Ehr.) V. H.
A. ovalis var. libyca (Ehr.) Cl.
A. ovalis var. pediculus (Kutz.) V. H.
Amphora questionable sp . #1
Amphora veneta var. capitata Haworth
Anonoeoneis vitrea (Grun.) Ross
AsterioneJIa formosa Hass.
Caloneis bacillum (Grun.) Cl .
C. bacillum var. lancettula (Schulz) Hust.
Caloneis sp . #1
Caloneis ventricosa var. #2
C. ventricosa var. truncatula (Grun.) Meist.
Cocconeis dimlnuta Pant .
C. pediculus Ehr.
C. placentula var. euglypta (Ehr.) Cl .
C. placentu-Za var. lineata (Ehr.) V. H.
*
Slides
1
8
6
25
4
1
1
4
4
1
6
3
2
3
56
1
5
1
1
1
1
1
85
14
1
1
8
28
5
80
8
1
5
282
1
2
1
1
1
28
2
2
6
Average
Cells/ml
0.007
0.060
0.040
0.214
0.027
0.007
0.007
0.040
0.040
0.007
0.047
0.020
0.013
0.020
0.843
0.007
0.033
0.027
0.007
0.013
0.007
0.007
1.345
0.120
0.007
0.007
0.087
0.241
0.040
1.258
0.074
0.007
0.040
38.501
0.007
0.013
0.007
0.007
0.007
0.241
0.013
0.013
0.040
% Pop
0.000
0.003
0.002
0.012
0.001
0.000
0.001
0.002
0.003
0.000
0.002
0.001
0.001
0.001
0.072
0.000
0.002
0.003
0.000
0.001
0.000
0.001
0.076
0.007
0.000
0.001
0.004
0.013
0.002
0.069
0.004
0.000
0.003
2.941
0.000
0.000
0.000
0.000
0.000
0.010
0.001
0.002
0.002
Maximum
Cells/ml
2.094
4.189
2.094
6.283
2.094
2.094
2.094
6.283
6.283
2.094
4.189
2.094
2.094
2.094
58.643
2.094
2.094
8.378
2.094
4.189
2.094
2.094
50.265
4.189
2.094
2.094
10.472
6.283
4.189
35.605
6.283
2.094
4.189
393.746
2.094
2.094
2.094
2.094
2.094
6.283
2.094
2.094
2.094
7. Pop
0.054
0.197
0.165
0.348
0.165
0.057
0.175
0.320
0.494
0.054
0.172
0.115
0.111
0.174
10.370
0.118
0.124
0.926
0.117
0.213
0.025
0.231
1.958
0.390
0.102
0.195
0.366
0.714
0.200
1.387
0.531
0.082
0.234
18.444
0.032
0.106
0.143
0.013
0.037
0.341
0.183
0.341
0.278
(continued)
370
-------
APPENDIX I (continued)
Cocconeis sp. #1
Coscinodiscus subsalsa Juhl-Dannf .
Cyclotella atomus Hust.
C. comensis Grun.
C. comensis auxospore
C. comta (E.lr.) Kucz.
C. coata (abnormal)
C. comtu auxc^pore
C. ccmta var. glabriuscula Grun.
C. comta var. oliguctis (Ehr.) Grun.
C. crjptica Rciir.ann, Lewin, and Guillard
C. kulzin-jiana Thw.
C. meneghiniana Kutz.
C. meneghiniana var. plana Fricke
C. micAiganiana Skv.
C. michiganiana auxospore
C. oce.Z.Zata Pant.
C. ocellata auxospore
C. cpercu.icj£a (Ag.) Kutz. ;.
C. pseudosteliigera Hust.
Cyclotella questionable sp . //I
Cyclotella sp. //I
CycJotelia sp. #2
CycJoteJJa sp . #3
CycIote.Z.2a sp . #5
Cyclotella sp . auxospore
CydoteJJa spp .
CycJoteUa steJJagera (Cl . and Grun.) V. H.
C. stelljgera auxospore
Ci/matop-Ieura elliptica (B-reb . and Godey) Wm. Smith
C. solea var. apiculata (Wm. Smith) Ralfs
C. solea (Breb. and Godey) Wm. Smith
Cymbella aspera (Ehr.) H. Perag.
C. cesatli (Rabh.) Grun.
C. cistula (Ehr.) Kirchn.
C. delicatula Kutz.
C. hustedtn Krasske
C. hybrida Grun.
C. laevis Nag.
C. Icptoceros var. rostrata Hust.
C. microcephaly Grun.
C. minuta Hilse
C. minuta f o . Jatens (Krasske) Reira.
C. minuta var. silesiaca- (Bleisch and Rabh.) Reira.
t
Slides
1
9
1
154
49
222
2
2
1
3
1
3
14
1
257
2
281
23
109
16
1
1
1
7
105
9
2
302
4
1
4
1
1
3
1
6
1
2
1
1
47
5
7
11
Average
Cells/ml
0.007
0.147
0.007
150.126
0.716
4.724
0.013
0.027
0.007
0.020
0.007
0.020
0.161
0.007
14.567
0.013
24.128
0.194
2.549
0.201
0.013
0.007
0.007
0.187
2.262
0.047
0.013
53.884
0.033
0.007
0.027
0.007
0.007
0.020
0.007
0.040
0.007
0.020
0.007
0.007
0.502
0.060
0.100
0.120
% Pop
0.001
0.003
0.000
8.555
0.036
0.365
0.001
O.C04
0.001
O.C01
0.000
0.003
0.008
0.000
1.431
0.001
2.370
0.016
0.131
0.010
0.002
0.001
0.001
0.018
0.285
0.004
0.002
6.406
0.003
0.000
0.002
0.000
0.000
0.001
0.001
0.002
0.000
0.001
0.000
0.000
0.030
0.005
0.004
0.007
Maximum
Cells/ml
2.094
16.755
2.094
1507.963
18.850
31.416
2.094
4.189
2.094
2.094
2.094
2.094
10.472
2.094
140.324
2.094
169.646
6.283
37.699
12.566
4.189
2.094
2.094
14.661
46.077
2.094
2.094
720.471
4.189
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
4.189
2.094
2.094
12.566
6.283
10.472
10.472
7. Pop
0.165
0.242
0.056
76.250
1.288
3.704
0.249
0.738
0.260
0.121
0.138
0.377
0.694
0.042
29.949
0.211
17.438
0.647
2.179
0.733
0.763
0.158
0.231
1.984
7.143
0.377
0.346
86.216
0.763
0.054
0.394
0.146
0.012
0.099
0.174
0.158
0.029
0.197
0.115
0.121
0.927
0.634
0.348
0.566
(continued)
371
-------
APPENDIX I (continued)
# Average
Cynibella parvula Krasske
C. prostrata var . auerswaldn (Rabh .) Reim .
C. prostrata (Berk.) Cl .
Cynibella questionable sp . //I
Cynibe^Ja sp . #14
Cymbella sp . #2
Cymbella sp . #6
Cymbella spp .
Cymbella sub vent ricosa Cholnoky
C. triangu-Zum (Ehr.) Cl.
C. ventricosa (Ag . ) Ag .
Denticiila tenais Kutz.
D. cerj(_i;j var. cr^ssula (Nag. and Kut^.) W. and G. S.
West:
Diatcr.* cenue Ag.
£>. tenue var. elongatum Lyngb .
n. tenue var. pachycephala Grun.
n. vu-Zgare Bory
Diploneis boldtiana Cl .
D. elliptica var. pygmaea A. Cl .
D. oculata (Breb.) Cl .
D. parma Cl .
Diploneis sp . #1
£ucocconeis f-Zexella Kutz.
E. flexella var. alpestns (Brun) Hust.
£7ucoccone.is questionable sp . //I
Fragilaria irevistr-iata Grun.
F. irevistria ta var. infjata (Pant.) Hust.
F. capucina Desm.
F. capucina var. mesolepta Rabh.
F. construens (Ehr.) Grun.
F. construens var. binodis (Ehr.) Grun.
F. construens var. capitata Herib.
F. construens var. minuta Temp, and Per.
F. construens var. puntila Grun.
F. construens var. venter (Ehr.) Grun.
F. crotoriensis Kitton
F. intermedia Grun.
F. inter/media var. fallax (Grun.) A. Cl .
F. Jappon-ica Grun.
F. leptostauron (Ehr.) Hust.
F. -Zeptostauron var. dubia (Grun.) Hust.
F. pinnata var. intercedens (Grun.) Hust.
Slides
2
3
4
2
1
1
1
29
2
2
1
20
1
43
117
1
2
1
4
4
1
2
1
1
2
1
5
117
1
27
1
1
108
7
6
247
10
45
2
18
1
1
Cells/ml
0.013
0.020
0.333
0.013
0.007
0.007
0.007
0.301
0.013
0.013
0.007
0.007
0.201
0.007
0.943
8.398
0.007
0.013
0.007
0.027
0.027
0.007
0.013
0.007
0.007
0.181
0.007
0.094
77.010
0.013
1.024
0.013
0.007
1.720
0,067
0.167
115.679
0.074
3.165
0.020
0.442
0.013
0.007
% Pop
0.00.
0.000
0.002
0.001
0.000
0.000
0.001
0.018
0.002
0.002
0.000
0.000
0.012
0.000
0.052
0.487
0.000
0.001
0.000
0.004
0.002
0.000
0.001
0.000
0.000
0.021
0.000
0.006
3.007
0.001
0.038
0.001
0.001
0.163
0.003
0.013
7.577
0.004
0.234
0.002
0.022
0.002
0.001
Maximum
Cells/ml
2.094
2.094
4.189
2.094
2.094
2.094
2.094
8.378
2.094
2.094
2.094
2.094
8.378
2.094
77.493
475.427
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
37.699
2.094
12.566
2184.453
4.189
60.737
4.189
2.094
18.850
8.378
33.510
1897.521
4.189
278.554
4.189
23.038
4.189
2.094
% Pop
0.223
0.115
0.213
0.231
0.074
0.093
0.240
0.427
0.295
0.446
0.124
0.124
0.692
0.099
2.922
4.962
0.107
0.145
0.139
0.714
0.211
0.145
0.243
0.072
0.114
5.294
0.083
0.696
32.541
0.423
2.365
0.231
0.218
2.264
0.165
2.832
65.986
0.369
9.262
0.369
1.250
0.738
0.195
(continued)
372
-------
APPENDIX i (continued)
f Average
Fragilaria pinnata var. lancettula (Schum) Hust.
F. pinnata Ehr.
Fragilaria questionable sp. #1
Fragilaria sp . #10
Fragilaria spp.
Fragiiana vaucheriae (Kutz.) Peters.
F. vaucheriae var. capi tellata (Grun.) Patr.
F. vaucheriae var. truncata (Grev.) Grun.
Gomphonema intricatum Kutz.
G. o-Zivaceum (Lyngb.) Kutz.
Gomphonema questionable sp . //I
Gomphonema spp .
Gomphonema truncatum Ehr.
Gurosigma attenuatum (Kutz.) Rabh.
Helosira distans var. alpigena Grun.
M. granulata alpha status (Ehr.) Ralfs
Af. granulata var. angustissima 0. Mull.
Af. granulata (Ehr.) Ralfs
Af. islandica auxospore
Af. islandica 0. K-all .
Af. italica (Ehr.) Kutz.
Mcridion circulars (Grev.) Ag.
Navicula anglica var. slgnata Hust.
N. capitata Ehr.
AT. capitata var. hungarica (Grun.) Ross
N. capitata var. luneburgensis (Grun.) Patr.
N. cryptocephala var. intermedia Grun.
N. cryptocephala var. veneta (Kutz.) Rabh.
N. cryptocephala Kutz.
N. cuspidata (Kutz.) Kutz.
N. decussis 0str.
N. gottlandica Grun.
W. lanceolata (Ag.) Kutz.
H. later.s Krasske
Af. menisculus var. upsaliensis Grun.
N. minuscula Grun.
N. neoventricosa Hust.
N. nyassensis f o . minor 0. Mull.
N. placentula (Ehr.) Kutz.
N. pupula Kutz.
N. pupula var. capitata Skv. and Meyer
N. pupula var. elliptica Hust.
N. pupula var. rectangularis (Greg.) Grun.
Navicula questionable sp . #1
Slides
31
95
2
1
59
58
38
3
1
7
1
12
1
2
29
7
8
75
1
no
7
5
1
5
6
4
1
14
14
1
5
1
3
2
4
1
1
5
1
5
3
2
1
2
Cells/ml %
0
5
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
6
0
15
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.816
.032
.134
.007
.760
.830
.589
.020
.007
.094
.013
.134
.007
.013
.689
.308
.381
.417
.007
.236
.355
.094
.013
.033
.060
.027
.007
.120
.134
.007
.033
.007
.020
.013
.027
.007
.007
.033
.007
.040
.020
.013
.007
.020
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Pop
.034
.229
.015
.001
.105
.053
.033
.001
.000
.005
.001
.007
.000
.001
.058
.005
.018
.254
.001
.972
.014
.004
.001
.002
.003
.002
.000
.008
.007
.001
.001
.001
.002
.001
.002
.000
.000
.002
.001
.001
.001
.001
.000
.002
Maximum
Cells/ml
69
196
31
2
56
25
27
2
2
8
4
12
2
2
33
43
35
152
2
812
27
12
4
2
4
2
2
4
6
2
2
2
2
2
2
2
2
2
2
4
2
2
2
4
.115
.873
.416
.094
.549
.133
.227
.094
.094
.378
.189
.566
.094
.094
.510
.982
.605
.891
.094
.625
.227
.566
.189
.094
.189
.094
.094
.189
.283
.094
.094
.094
.094
.094
.094
.094
.094
.094
.094
.189
.094
.094
.094
.189
7.
2
7
3
0
4
1
1
0
0
0
0
0
0
0
3
0
2
4
0
27
1
0
Pop
.692
.667
.472
.173
.515
.493
.937
.117
.072
.279
.463
.418
.085
.155
.612
.539
.024
.768
.370
.019
.190
.502
0.422
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.143
.348
.174
.116
.658
.429
.246
.126
.172
.299
.118
.190
.120
.085
.211
.211
.163
.278
.189
.151
.491
(continued)
373
-------
APPENDIX I (continued)
t Average
Navicula spp.
Navicula radiosa var. tenella (Breb.) Grun.
N. radiosa Kutz.
N. rhyncbocephala Kutz.
H . rotunda Hust.
Navicula sp. #44
Navicula stroesei A. Cl .
N. subrhynchocephala Hust.
N. tripunctata var. schizonen&ides (V. H.) Patr.
N. tuscula Ehr.
N. viridula (Kutz.) Kutz.
ft. vulpina Kutz.
Neidium dubium f o . constrictum Hust.
iV. dubium var. //I
N. iridis var. vernajis Reich.
Neidium sp . #1
Nitzschia acicularis (Kutz.) Wm . Smith
N. acuta Hantz.
N. angustata var. acuta Grun.
K . bacata Hust.
N. capitellata Hust.
N. confinis Hust.
N. denticula Grun.
N. dissipata (Kutz.) Grun.
N. dissipata var. media (Hantz.) Grun.
N. fonticola Grun.
N. fonticola var. pelagica Hust.
N. interrupta (Reich.) Hust.
ft. kutzingiana Hilse
N. 1 means Wm . Smith
N. longissima var. reversa Grun.
N. luzonensis Hust.
W. palea (Kutz.) Wm. Smith
H. pseudoatomus Stoerm.
Nitzschia questionable sp . #1
Nitzschia questionable spp.
Nitzschia recta Hantz.
N. romana Grun.
N. sigmoidea (Nitz.) Wm. Smith
N. sinuata var. tabellaria (Grun.) Grun.
Nitzschia sp. //I
Nitzschia sp. 1119
Nitzschia sp . #2
Slides
79
4
8
6
1
25
1
2
1
3
1
1
1
1
1
1
179
33
1
17
25
4
3
1
127
1
57
1
1
3
18
1
12
37
1
1
153
1
1
8
1
7
21
34
Cells/ml
1.037
0.040
0.067
0.047
0.007
0.274
0.007
0.013
0.007
0.020
0.007
0.007
0.007
0.007
0.007
0.007
5.922
0.268
0.007
0.161
0.288
0.033
0.027
0.007
2.536
0.007
0.596
0.007
0.007
0.020
0.214
0.007
0.154
0.294
0.007
0.027
3.546
0.007
0.007
0.060
0.007
0.060
0.201
0.375
% Pop
0.060
0.002
0.004
0.002
0.000
0.013
0.000
0.000
0.000
0.001
0.000
0.001
0.001
0.000
0.001
0.000
0.454
0.016
0.001
0.009
0.018
0.002
0.001
0.000
0.238
0.000
0.038
0.000
0.000
0.001
0.017
0.000
0.009
0.025
0.000
0.003
0.218
0.001
0.000
0.004
0.000
0.004
0.013
0.027
Maximum
Cells/ml
23.038
4.189
4.189
4.189
2.094
8.378
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
52.360
6.283
2.094
6.283
10.472
4.189
4.189
2.094
29.322
2.094
14.661
2.094
2.094
2.094
18.850
2.094
23.038
4.189
2.094
8.378
58.643
2.094
2.094
4.189
2.094
4.189
6.283
16.755
% Pop
1.174
0.348
0.313
0.282
0.089
0.352
0.118
0.120
0.084
0.124
0.107
0.216
0.329
0.124
0.240
0.082
5.159
0.647
0.329
0.463
1.502
0.277
0.197
0.084
2.947
0.113
1.384
0.107
0.154
0.162
0.961
0.029
1.343
1.429
0.107
0.926
3.419
0.175
0.119
0.254
0.070
0.319
0.494
1.527
(continued)
374
-------
APPENDIX I (continued)
. .
t Average
Nitzschia sp. #32
Nitzschia sp . #6
Nitzschia sp . //7
Nitzschia sp . #9
Nitzschia spiculoides Hust.
W. subllnearis Hust.
N. tryblionella var. levidensis (Wm. Smith) Grun.
Oestrupia zachariasi (Reich.) Stoerm. and Yang
O. zachariasi var. undulata (Schulz) Stoerm. and Yang
Opephora martyi rierib .
Pinnularia brebissonn (Kutz.) Rabh .
Rhizosolenia eriensis H. L. Smith
R. gracilis H. L. Smith
Rhoicosphenia curvata (Kutz.) Grun.
Stephanodiscus alpinus Hust.
S. astraea (Ehr.) Grun.
S. binderanus (Kutz.) Krieger
S. hantzschu Grun.
5. minutus Grun.
S. niagarae Ehr.
Stephanodiscus questionable sp . #1
Stephanodiscus sp . #1
Stephanodiscus sp . #5
Stephanodiscus sp . auxospore
S. subtilis (Van Goor) A. Cl .
S. tennis Hust.
S. transilvanicus Pant.
Surirella angusta (Kutz.)
S. Mseriata var. bifrons (Ehr.) Hust.
S. ovata (Kutz.)
5. ovata var. pinnata (Wm. Smith) Hust.
Surirella questionable sp . #1
Surirella sp . #1
Synedra acus Kutz.
S. cyclopum Brutschy
S. de-Iicatjssima Wm. Smith
S. del icatissima var. angustissima Grun.
S. filiformis Grun.
S. incisa Boyer
S. minuscula Grun.
S. ostenfeldii (Krieger) A. Cl .
S. ostenfeldii (abnormal)
S. _odrasitica (Wa. Smith) Hust.
Sjnedra sp. (abnormal)
Slides
49
17
1
1
32
2
1
1
1
5
1
206
211
1
102
1
36
133
161
12
8
1
1
1
26
10
37
23
1
6
5
1
1
8
20
1
8-
247
1
124
157
2
10
1
Cells/ml
0.602
0.141
0.007
0.007
0.348
0.013
0.007
0.007
0.007
0.060
0.007
14.801
34.968
0.007
2.630
0.007
5.547
7.862
7.508
0.120
0.080
0.013
0.007
0.007
2.329
0.087
0.308
0.221
0.007
0.047
0.033
0.007
0.007
0.067
0.167
0.007
0.067
52.392
0.007
3.118
6.899
0.013
0.107
0.007
% Pop
0.058
0.009
0.001
0.000
0.021
0.001
0.000
0.001
0.000
0.003
0.000
1.273
3.125
0.001
0.144
0.001
0.177
0.451
0.602
0.006
0.005
0.001
0.000
0.001
0.166
0.006
0.022
0.016
0.000
0.002
0.001
0.001
0.000
0.003
0.015
0.001
0.004
4.350
0.000
0.224
0.625
0.002
0.007
0.000
Ma x imum
Cells/ml
12.566
8.378
2.094
2.094
8.378
2.094
2.094
2.094
2.094
6.283
2.094
115.192
192.684
2.094
420.973
2.094
462.861
651.356
337.197
6.283
4.189
4.189
2.094
2.094
142.419
6.283
6.283
6.283
2.094
4.189
2.094
2.094
2.094
4.189
6.283
2.094
4.189
257.610
2.094
75.398
64.926
2.094
8.378
2.094
% Pop
1.592
0.780
0.242
0.122
0.903
0.139
0.113
0.175
0.059
0.633
0.114
9.395
17.895
0.377
17.121
0.313
11.914
26.491
13.473
0.661
0.276
0.163
0.083
0.329
8.553
0.394
0.489
0.738
0.017
0.353
0.165
0.211
0.148
0.196
0.862
0.369
0.422
22.222
0.117
4.478
5.363
0.353
0.467
0.145
(continued)
375
-------
APPENDIX I (continued)
Synedra spp .
Synedra ulna var . chaseana Thomas
S. ulna var. claviceps Hust .
5. ulna var. danica (Kutz.) V. H.
S. ulna (Nitz.) Ehr.
Tabellaria fenestrata (Lyngb.) Kutz.
T. fenestrata var. geniculata A. Cl .
T. flocculosa (Roth) Kutz.
T. flocculosa var. lineans Koppen
Total for Division (271 species)
CHRYSOPHYTA
Chrysophyte cyst
Chrysococcus dokidophorus Pasch
Chrysosphaerella longispina Lautb .
Dinobryon bavaricum Irahof
D. cylindricum Irahof
D. cylindncum statospore
r^nusryon sp?. statospores
Dinobryon divergent Imhof
£>. divergens statospore
D. social e Ehr.
D. sociale var. americanum (Brunn.) Bach.
D-inoiryon spp.
Kephyrion spirale (Lackey) Conrad
Mallontonas >elcngata Reverdin
M. pseudocoronata Presc.
Mallormnas sp . //3
Mallomonas sp. #4
Mallon&nas statospore
Af. tonsurata var. alpina (Pasch. and Ruttn.) Krieger
Ochron&nas sp . //I
Ochromonas sp . /^2
Ochro/nonas spp .
Rhlzochrysis limnetica G. M. Smith
Rhizochrysis sp . #1
Uroglenopsis amencana (Calkins) Lemm.
Total for Division (25 species)
t
Slides
26
111
1
2
40
222
12
30
213
31
188
64
11
1
1
183
113
2
4
4
56
1
13
57
9
3
17
41
144
2
1
3
1
1
Average
Cells/ml
0.388
2.201
0.007
0.047
0.442
58.040
0.408
1.071
28.772
790.488
0.462
3.707
40.114
0.448
0.040
0.040
6.665
14.614
0.020
0.515
0.094
3.566
0.007
0.087
0.629
0.060
0-.020
0.134
0.335
3.720
0.020
0.013
0.033
0.007
0.836
75.725
% Pop
0.037
0.158
0.001
0.003
0.026
4.292
0.017
0.090
2.095
55.726
0.073
0.330
1.872
0.029
0.008
0.005
0.511
1.054
0.001
0.057
O.OC6
0.354
0.001
0.006
0.063
0.002
0.000
0.010
0.024
0.337
0.000
0.002
0.003
0.001
0.046
4.722
Maximum
Cells/ml
16.755
25.133
2.094
12.566
8.378
494.277
54.454
35.605
171.740
18.850
31.416
862.890
56.549
12.566
12.566
150.796
228.289
4.189
83.776
12.566
64.926
2.094
2.094
12.566
2.094
2.094
4.189
6.283
48.171
4.189
4.189
4.189
2.094
261.799
% Pop
3.019
1.757
0.377
0.714
0.846
28.710
0.911
3.390
18.304
3.782
3.472
45.632
4.147
2.362
1.467
7.886
21.087
0.146
9.542
1.502
8.148
0.244
0.347
2.538
0.107
0.060
0.446
0.435
8.051
0.117
0.491
0.533
0.249
14.468
(continued)
376
-------
APPENDIX I (continued)
# Average
CRYPTOPHYTA
Cryptorconas erosa Ehr.
C. ovata Ehr.
Cryptononas sp . //I
Rhodomonas minuta Skuja
R. minuta var. nannoplanctica Skuja
Total for Division (5 species)
PYRROPHYTA
Ceratium hirundinella (0.7. Mull.) Shrank
Gymnodinium helveticum Penard
Gyntnodinium sp.
Peridinium aciculiferum (Lemm.) Lemm.
P. lindemanni Lef.
Peridinium sp . //I
Peridinium spp.
Spirodinium pusillum var. minor? Skuja
Total for Division (8 species)
EUGLENOPHYTA
Phacus sp. //I
Trachelon&nas volvacina Ehr.
Total for Division (2 species)
MYXOPHYTA
Beggiatoa alba (Vauch.) Trev.
Total for Division (1 species)
Undetermined flagellates sp . HI
Undetermined flagellate spp.
Total for Division "Un" (2 species)
Slides
4
256
1
46
247
19
1
8
18
3
5
20
63
1
3
6
1
309
Cells/ml
0
7
0
0
8
16
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
58
58
.027
.106
.007
.522
.244
.367
.161
.007
.060
.161
.033
.033
.187
.669
.312
.007
.027
.033
.094
.094
.060
.120
.180
%
0
0
0
Pop
.000
.458
.001
0.048
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
4
.765
.345
.009
.000
.004
.014
.003
.003
.012
.056
.102
.000
.001
.001
.006
.006
.011
.452
.463
Maximum
Cells/ml %
2
113
2
12
54
6
2
4
8
4
2
6
10
2
4
8
18
416
.094
.097
.094
.566
.454
.283
.094
.189
.378
.189
.094
.283
.472
.094
.189
.378
.850
.784
0
4
0
2
7
0
0
0
0
0
0
Pop
.054
.008
.244
.542
.925
.341
.100
.456
.490
.489
.287
0.489
1
0
0
0
3
26
.303
.025
.154
.725
.422
.400
3TT
-------
APPENDIX II
CHRONOLOGY OF LAKE HURON ALGAL RESEARCH
Date Author
Divisional Group
Site
1842
1845
1847
1849
1872
1911
1911
1911
1912
1913
1913
1915
1915
1915
1921
1924
1927
1928
1961
1962
1964
1965
1966
1966
1967
1967
1967
1967
1968
1968
1969
1969
1969
1970
1970
1971
1972
1973
1973
1973
1973
1973
1974
1974
1974
1974
1974
1974
1975
1975
1975
1975
1975
1975
1975
1976
1976
1977
Bailey, J.W.
Ehrenberg, C.G.
Bailey, J.W.
KUtzing, F.T.
Briggs, S.A.
Baker, H.B. In: Ruthven, A.G.
Coons, G.H. In: Ruthven, A.G.
Klugh, A.B.
Klugh, A.B.
Klugh, A.B.
Klugh, A.B.
MacClement, W.T.
Boyer, C.S. In: MacClement, W.T.
Klugh, A.B. In: MacClement, W.T.
Bailey, L.W. and A.H. Mackay
Bailey, L.W.
Boyer, C.S.
Collins, F.S.
Schlichting, H., Jr.
Fenwick, M.
Neil, J.H. and G.E. Owen
Beeton, A.M.
Davis, C.C.
Patrick, R. and C.W. Reimer
Bellis, V.J. and D.A. McLarty
Fetteroff, C. and J. Robinson
Fetteroff, C. et. al.
Michigan Water Res. Commission
Fenwick, M.
Stoermer, E.F. and J.J. Yang
Herbst, R.P.
Michalski, M.F.P. In; Anderson, D.V.
Parkos, W.G. et. al.
Beeton, A.M. In: Swain, W.R. et. al.
Robinson, J.
Veal, D.M, and M.F.P. Michalski
Berst, A.H. and G.R. Sprangler
Hohn, M.H. In: Batchelder, T.L.
Chartrand, T.A.
Munawar, M. and I.F. Munawar
Neil., J.H. In: Ont. Water Res. Comm.
Schelske, C.L. and J.C. Roth
Freedman, P.
Limnetics, Inc.
Robinson, J.
Schelske, C.L. et. al.
Vollenweider, R.A. et. al.
Young, D.C.
Great Lakes Water Quality Board
Lowe, R.L.
Munawar, M. and I.F. Munawar
Neil, J.H. In: Shear, H.
Nicholls, K.H. e_£. al.
Patrick, R. and C.W. Reimer
Stoermer, E.F.
Lowe, R.L.
Stoerraer, E.F. et. al. In: Schelske
C.L. e£. al.
Fnedrich, P.O. and C .K. Lin
B-G
B-G
G,B-G
B-G
G,B-G
G
G,Ch,Cr,B-G,E,Dn,X
G,Ch,B-G,Dn
G,Ch,B-G,Dn
G,Ch,B-G
G,Ch,Cr,B-G
G,Ch,B-G,Dn
Ch,B-G
Ch,Cr,Dn
G,Ch,B-G,Dn
B-G,Dn
B-G
Cr,B-G,Dn
Ch,Cr,B-G,Dn
G,Cr,B-G,E,Dn
G,Cr,B-G,Dn
,G,Chl,Ch,Cr,B-C,E,Dn
,G,Ch,Cr,B-G,Dn
Mackinaw Is.-Lake Huron
Mackinaw Is.-Lake Huron
Lake Huron
Mackinaw Is.-Lake Huron
Mackinaw Is.-Lake Huron
Saginaw Bay
Saginaw Bay
Georgian Bay
Georgian Bay
Georgian Bay
Georgian Bay
Georgian Bay
Go Home Bay-Georgian Bay
Georgian Bay
Parry Sound-Georgian Bay
Georgian Bay
Mackinaw Is.-Lake Huron
Georgian Bay
Port Sanilac, Mi .-Lake Huron
Lake Huron
Lake Huron
Lake Huron
Lake Huron
Mackinaw Is.-Lake Huron
Port Franks, Ont.-Lake Huron
Lake Huron
Thunder Bay-Lake Huron
Lake Huron
Lake Huron
Lake Huron
Lake Huron
Lake Huron
Lake Huron
Lake Huron
Lake Huron
Georgian Bay
Lake Huron
Saginaw Bay
Whitestone Pt.-Saginaw Bay
Lake Huron
Georgian Bay, Lake Huron
Saginaw Bay, Lake Huron
Sagianw Bay
Lake Huron
Harbor Beach, Mi . -Lake Huron
Saginaw Bay, Lake Huron
Saginaw Bay, Lake Huron
Georgian Bay
Lake Huron
Lake Huron
Lake Huron
Saginaw Bay, Lake Huron
Georgian Bay
Mackinaw Is.-Lake Huron
Sagianw Bay, Lake Huron
Lake Huron
Mackinac Straits-Lake Huron
Lake Huron
D
Chi
G
Ch
Cr
diatoms
chloromonads
green algae
chrysophyts
crypt omonads
Baci llariophyta
Chloromonophyta
Chlorophyta
Chrysophyta
Cryptophyta
B-G blue-green algae
E euglenoids
Dn dinoflage Hates
X ye How-green algae
Cyanophyta
Euglenophyta
Pyrrhophyta
Xanthophyta
578
-------
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with some account of the most interesting species which have been found
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Bailey, J. W. 184?. Notes on the Algae of the United States. Amer. J.
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Bailey, L. W. 1924. An Annotated Catalogue of the Diatoms of Canada showing
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Baker, H. B. 1911. Mollusca. In: Ruthven, A. G. 1911. A biological
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Boyer, C. S. 1927. Synopsis of North American Diatomaceae. Proc. Acad.
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379
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Briggs, S. S. 18?2. Some of the Diatomaceae of Upper Lake Huron and the
Sault Lens, 1:235-237.
Chartrand, T. A. 1973-1975. A Report on Taste and Odor in Relation to the
Saginaw-Midland Supply at Whitestone Point in Lake Huron. Saginaw Water
Treatment Plant, Saginaw, Michigan.
Collins, F. S. 1928. Green Algae of North America. Text and Supplements.
Reprint, G. E. Stechert and Co. 1928, N.Y., N.Y.
Coons, G. H. 1911. Ecological relations of the flora, in: Ruthven, A. G.
1911. A biological survey of the sand dune region on the south shore of
Saginaw Bay, Michigan. Mich. Geol. Biol. Surv., 1910 Publ. 4, Biol.
Ser., 2:35-64.
Davis, C. C. 1966. Plankton Studies in the Largest Great Lakes of the
World, with special reference to the St. Lawrence Great Lakes of North
America. Univ. Mich., Great Lakes Res. Div. pub. 14:1-366.
Ehrenberg, C. G. 1845. Some Interesting Algae from Lake Huron. Trans.
Amer. Microsc. Soc., 81(1): 72-76.
Fenwick, M. G. 1968. Lake Huron Distribution of Tabellaria fenestrata
var. peniculata A. Cleve and Coelastrum reticulatum var.
POlYCordon Korskik. Trans. Amer. Microsc. Soc., 87(3): 376-383-
Fetteroff, C. and J. Robinson. 1967. Biological Surveys of the Harbor
Vicinity, Lake Huron, Harbor Beach, June 6, 1958 and August 5, 1965.
Mich. Water Res. Comm., mimeo, 12 pp.
Fetteroff, C., J. Robinson, M. Newton, J. Seeburger and B. Mills. 1967.
Biological Surveys of Thunder Bay and Thunder Bay River, Alpena,
Michigan, 1957 and 1965. Mich. Water Res. Comm., mimeo, 16 pp.
Freedman, P. L. 1974. Saginaw Bay: An Evaluation of Existing and Historical
Conditions. Environmental Protection Agency, Region V, 137 pp.
Friedrich, P. D. and C. K. Lin. 1977. Phytoplankton Culture and the Effects
of Light and Temperature on Growth, (abstr.). 20th Conf. Great Lakes
Res. Abstracts, Internat Assoc. Great Lakes Res.
Great Lakes Water Quality Board. 1975. Great Lakes Water Quality, 3rd
Annual Report. International Joint Comm., Windsor, Ont., 170 pp.
Herbst, R.P. Ecological Factors and the Distribution of Cladophora
glomerata in the Great Lakes. Amer. Midi. Nat., 82(1): 90-98.
Hohn, M. H. 1973- ID.: Batchelder, T. L. 1973- Saginaw Bay Baseline
Ecological Survey 1971. Waste Control Dept., Dow Chemical Co., 56 pp.
and appendices..
380
-------
Klugh, A. B. 1912. The Plant Formations of the Bruce Peninsula. Ont. Nat.
Sci., Bull. 7:10-21..
Klugh, A. B. 1913. Notes on the Plant Formations of the Shores of Georgian
Bay. Ont. Nat. Sci., Bull. 8:13-31.
Klugh, A. B. 1913. Notes on the Algae of Georgian Bay. Rhodora, 15(173):
88-92.
Klugh, A. B. 1915. In: MacClement, W. T. 1915. Preliminary Report on
the Plants of Georgian Bay. Contr. Can. Biol., 1911-1914(10), Fasc. 2:
201-211.
Kutzing, F. T. 1849. Species Algarum. Lipsiae, F. A. Brockhaus. 922 pp.
Reprint, A. Asher and Co., Amsterdam, 1969.
Limnetics, Inc. 1974. An Environemntal Study of the Ecological Effects of
the Thermal Discharge from Point Beach, Oak Creek, and Lakeside Power
Plants on Lake Michigan. 2 vols. Limnetics, Inc. Milwaukee, Wise.
Lowe, R. L. 1975. Comparative Ultrastructure of the Valves of some
Cvclotella species (Bacillariophyceae). J. Phycol., 11(4): 415-424.
Lowe, R. L. 1976. Phytoplankton in Michigan's Nearshore Waters of Lake
Huron and Lake Superior 1974. Mich. Dept. Nat. Res., Tech. Rept.,
30 pp.
MacClement, W. T. 1915- Preliminary Report on the Plants of Georgian Bay.
Contr. Can. Biol., 1911-1914(10), Fasc. 2: 201-211.
Michalski, M. F. P. 1969. Planktonic and Periphytic Algae of the Great
Lakes - A list of recorded species and their distribution. Appendix VI,
part 2: 40-66. 3.n: Anderson, D. V. (ed.). 1969. The Great Lakes as
an Environment. Univ. Toronto, Great Lakes OInst., Rept. No. 39,
189 pp. and appendices.
Michigan Water Resources Commission. 1967. Water Resource Uses Present and
Prospective for Lake Huron and Water Quality Standards and Plan of
Implementation. Mich. Water Res. Comm., Dept. Conserv., 98 pp.
Munawar, M. and I. F. Munawar. 1973. The phytoplankton of Lake Huron.
(abstr.). 16th Conf. Great Lakes Res. Abstracts, 16-17. Internat.
Assoc. Great Lakes Res.
Munawar, M. and I. F. Munawar. 1975. The abundance and significance of
phytoflagellates and nannoplankton in the St. Lawrence Great Lakes. 1.
Phytoflagellates. Verh. int. Verein. Limnol., 19: 705-723.
Neil, J. H. and G. E. Owen. 1964. Distribution, Environmental Requirements
and Significance of Cladophora in the Great Lakes. Univ. Mich., Great
Lakes Res. Div., Publ. 11: 113-121.
381
-------
Neil, J. H. 1973. Nature of Growth. In: Ontario Water Resource
Commission. 1973. Report on Cladoohora Investigations in Ontario
1958 to 1967. Ont. Ministry of the Environ., Toronto, Ont.
Neil, J. H. 1975. Distribution, 17-25. In : Shear, H. and D. E.
Konawewich (eds.). 1975. Cladoohora in the Great Lakes. Internat.
Joint Comm., Res. Advisory Board, 179 pp.
Nicholls, K. H., E. C. Carney, and G. W. Robinson. 1975. Phytoplankton of
an Inshore Area of Georgian Bay of Lake Huron Prior to Reductions in
Phosphorus Loading from Local Sewage Treatment Facilities. Ont.
Ministry of the Environ., Toronto, Ont. 33 pp.
Parkos, W. G., T. A. Olson, and T. 0. Odlaug. 1969. Water Quality Studies
on the Great Lakes Based on Carbon Fourteen Measurements on Primary
Productivity. Univ. Minn., Water Res. Res. Center, Bull. 17, 121 pp.
Patrick, R. and C. W. Reimer. 1966. The Diatoms of the United States
exclusive of Alaska and Hawaii. Vol. I. Fragilariaceae, Eunotiaceae,
Achnathaceae, and Naviculaceae. Acad. Nat. Sci., Phila., Monogr. 13,
688 pp
Patrick, R. and C. W. Reimer. 1975. The Diatoms of the United States
exclusive of Alaska and Hawaii. Vol. II., part 1. Entomoneidaceae,
Cymbellaceae, Gomphonemaceae and Epithemiaceae. Acad. Nat. Sci.,
Phila., Monogr. 13, 213 PP.
Robinson, J. G. 1970. Great Lakes Algae Monitoring Program. 19&9. Mich.
Water Res. Comm., Dept. Nat. Res., 16 pp.
Robinson, J. G. 1974. Reconnaisance Survey of Algae Conditions Vicinity of
Harbor Beach on Lake Huron. Unpubl. Rept., Mich. Water Res. Comm.,
Mich. Dept. Nat. Res.
Schelske, C. L. and J. C. Roth. 1973. Limnolgical Survey of Lakes Michigan,
Superior, Huron, and Erie. Univ. Mich., Great Lakes Res. Div.,
Publ. 17, 108 pp.
Schelske, C. F., L. E. Feldt, M. S. Simmons, and E. F. Stoermer. 1974.
Storm Induced Relationships among Chemical conditions and Phytoplankton
in Saginaw Bay and Western Lake Huron. Proc. 17th Conf. Great Lakes
Res., 1974: 78-91. Internat. Assoc. Great Lakes Res.
Schlichting, H. E., Jr. 1961. Viable Species of Algae and Protozoa in the
Atmosphere. Lloydia 24(2): 81-88.
Stoermer, E. F. and J. J. Yang. 1968. A Preliminary Report of the Fossil
Diatom Flora from Lake Huron Sediments. Proc. 11th Conf. Great Lakes
Res., 1968: 253-267. Internat. Assoc. Great Lakes Res.
382
-------
Stoermer, E. F. 1975. The Effects of Energy-Related Effluent on
Phytoplankton Communities. Proc. 2nd Fed. Conf. on the Great Lakes,
409-422. Argonne National Laboratory.
Stoermer, E. F. , R. G. Kreis Jr., and T. B. Ladewski. 1976. Phytoplankton.
Chapter 6, 90-180 and appendix D. Jp: Schelske, C. L., E. F.
Stoermer, J. E. Gannon and M. S. Simmons. 1976. Biological, Chemical,
and Physical Relationships in the Straits of Mackinac. Univ. Mich.,
Great Lakes Res. Div. Spec. Rept. 60, 267 pp.
Veal, D. M. and M. F. P. Michalski. 1971. A Case of Nutrient Enrichment in
an Inshore Area of Georgian Bay. Proc. 14th Conf. Great Lakes Res.,
1971: 277-292. Internat. Assoc. Great Lakes Res.
Vollenweider, R. A., M. Munawar, and P. Stadelmann. 1974. A Comparative
Review of Phytoplankton and Primary Production in the Laurentian
Great Lakes. J. Fish. Res. Bd. Can., 31(5): 739-762.
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cistula var. gibbosa Brun. (abstr.). J. Phycol., Suppl. 10:11.
383
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-6QO/3-8n-nfi1
3. RECIPIENT'S ACCESSIOONO.
4 TITLE AND SUBTITLE
Phytoplankton Composition and Abundance in
Southern Lake Huron
5. REPORT DATE
July 198J Issuing Date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
E.F. Stoermer and R.G. Kreis, Jr.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Great Lakes Research Division
University of Michigan
Ann Arbor, Michigan 48109
10. PROGRAM ELEMENT NO.
1BA769
11. CONTRACT/GRANT NO.
R803086
12. ^oNsoRiNfi AGENCY NAME AND ADDRESS
Environmental Research Laboratory-Dul uth
Office of Research and Development
U.S. environmental Protection Agency
Duluth, Minnesota 55804
13. TYPE OF REPORT AND PERIOD COVERED
Final 1974-1976
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Southern "Lake Huron contains a diversity of phytoplankton assemblage types
ranging from assemblages characteristic of oligotrophic waters to those which usually
occur under highly eutrophic conditions. The offshore waters are generally charac-
terized by oligotrophic associations and most eutrophic associations are associated
with the Saginaw Bay interface waters. Under certain conditions, populations which
are generated within Saginaw Bay are found mixed with offshore assemblages,
apparently as a result of passive dispersal. The most widely dispersed populations
include nuisance-producing blue-green algae such as Aphanizomenon flos-aquae.
During the period of study, floristic modification resulting from inputs from
Saginaw Bay was usually found along the Michigan coast south of the bay, but cases
were noted where greatest effect was found at stations north of the bay or eastward
into the open lake. Along the Canadian shore assemblages were qualitatively and
quantitively dissimilar from assemblages in Saginaw Bay. On the basis of our results
southern Lake Huron appears to be a somewhat more disturbed region- than generally
realized. Phytoplankton assemblage modification appears to result from both the
influence of nutrients and other materials entering the lake directly and from the
dispersal of populations from highly eutrophic Saginaw Bay into the open lake. The
wide dispersal of these populations is of special interest since it may furnish a
mechanism for transport of nutrients and toxic material from highly impacted
-Sag-inaw Bay into the open lake^
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Held/Group
Algae, Lakes, Nutrients
Lake Huron
06/C
13 DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
396
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
384
I) S GOVERNMENT PRINTING OFFICE 1 980--6 57-1 6 B/0026
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