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FOREWORD
The Great Lakes National Program Office (GLNPO) of the United States
Environmental Protection Agency was established in Region V, Chicago to
focus attention on the significant and complex natural resource represented
by the Great Lakes.
GLNPO implements a multi-media environmental management program drawing
on a wide range of expertise represented by Universities, private firms, State,
Federal, and Canadian Governmental Agencies and the International Joint
Commission. The goal of the GLNPO program is to develop programs, practices
and technology necessary for a better understanding of the Great Lakes Basin
Ecosystem and to eliminate or reduce to the maximum extent practicable the
discharge of pollutants into the Great Lakes system. The Office also coordi-
nates U.S. actions in fulfillment of the Agreement between Canada and the
United States of America on Great Lakes Water Quality of 1978.
This study was supported by a GLNPO grant to the University of Michigan
at Ann Arbor for investigating the phytoplankton assemblages of the nearshore
zone of southern Lake Michigan.
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EPA-905/3-79-001 c- 2.
PHYTOPLANKTON ASSEMBLAGES OF THE
NEARSHORE ZONE OF SOUTHERN LAKE MICHIGAN
by
E. F. Stoermer and Marc L. Tuchman
Great Lakes Research Division
University of Michigan
Ann Arbor, Michigan M8109
Grant R005337 01
Project Officer
David C. Rockwell
Great Lakes National Program Office
536 South Clark Street
Chicago, Illinois 60605
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION V
CHICAGO, ILLINOIS 60609
U.S. Environmental Protection Agency
Region 5, Library (PL42J)
77 West Jackson Boulevard, 12th Ftoor
Chicago, It 60604-3590
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DISCLAIMER
This report has been reviewed by the Great Lakes National Program Office,
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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ABSTRACT
Phytoplankton samples from nearshore stations along the Indiana coast of
Lake Michigan were analyzed to determine the composition and seasonal abundance
of phytoplankton populations in this region. Occurrence patterns of major
populations and population groups were inspected to detect unusual patterns
which might be indicative of particular inputs to this region of Lake
Michigan. As might be expected in a local inshore region where physical mixing
and advection processes are relatively intense, phytoplankton distribution is
highly variable. The largest general effect noted is a continuing increase in
groups other than diatoms, apparently as a result of silica depletion resulting
from phosphorus enrichment. The singular exception to this trend is the
abundant occurrence of Cyclotella comensis. a diatom which has only recently
become abundant in Lake Michigan and which can apparently tolerate very low
silica levels. An effect more specific to the region is the atypically high
abundance of members of the diatom genus Nitzschia during some sampling
periods. High abundance of these organisms is often associated with organic
nitrogen and ammonia inputs, and this appears to be the case in the Indiana
nearshore region of Lake Michigan. Occasional occurrences of populations such
as Thalassiosira sp. and Skeletonema spp. were also noted in the samples.
These appear to be associated with isolated water masses and may be indicative
of local areas of high conservative ion input. It should be noted that the
thermal bar period, when the effects of conservative ion loadings might be
expected to be most intense, was not represented in the samples examined.
Another characteristic of the phytoplankton assemblages in the Indiana
nearshore region is the high abundance of microflagellates, especially
iii
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organisms which apparently belong to the Haptophyceae or Prasinophyceae.
Although these organisms are known to be abundant in areas of the Great Lakes
which are substantially perturbed, and are apparently generally increasing in
Lake Michigan, little is known about their specific ecology due to
methodological difficulties in identification. Further research should be
devoted to this topic.
iv
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CONTENTS
Abstract . iii
List of Figures vi
List of Tables. . . vi
Acknowledgments . .vii
1. Introduction 1
2. Materials and Methods 4
3. Results
Overall Abundances of Major Algal Groups . 7
Regional and Seasonal Trends in Abundance of Selected Taxa. . . 10
Bacillariophyta 10
Chlorophyta 28
Cryptophyta .28
Cyanophyta . 32
Microflagellates 36
4. Discussion 38
References 45
Appendix Figures 47
Appendix Table 1 80
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FIGURES
Number Page
1 Sampling station locations; southern Lake Michigan, 1977. .... 5
2 Seasonal Distribution and Abundance Trends of the Total
Phytoplankton Assemblage 9
3 Distribution of Asterionella formosa 11
4 Distribution of Cvclotella comensis 13
5 Distribution of Cvclotella crvpfrica 14
6 Distribution of Cvclotella pseudostelligera 16
7 Distribution of Cvclotella stelligera 17
8 Distribution of Fragilaria^ crotonensis 19
9 Distribution of Nitzschia acicularis 20
10 Distribution of Nitzschia, fonticola 22
11 Distribution of Nitzschia palea 23
12 Distribution of Stephanod^gous minutus 24
13 Distribution of Svnedra filiformis 26
14 Distribution of Tabellarifl flocculosa, var. linearis 27
15 Distribution of Chlamvdomonas spp 29
16 Distribution of Scenedesmus spp 30
17 Distribution of Crvpfromona,s ovata 31
18 Distribution of Anabaena f}os-aauae 33
19 Distribution of Anacystis incerta 34
20 Distribution of Oscillatoria bornetii 35
21 Distribution of Haptophyte sp. #1 37
TABLE
Table 1 Statistical summary of major algal groups in southern Lake
Michigan, 1977 8
vi
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ACKNOWLEDGMENTS
We would like to thank Ted B. Ladewski for his assistance on the computer
analysis used in this study. We would also like to acknowledge the U.S.
Environmental Protection Agency for collecting the samples and performing the
physico-chemical analyses.
vii
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INTRODUCTION
Compared to most areas of the Great Lakes, the southern shoreline region
of Lake Michigan has enjoyed a relatively long period of study. Qualitative
records of phytoplankton and benthic algal occurrence extend back into at least
the 1870's. The history of these investigations has been reviewed by several
authors, including Stoermer and Yang (1969). One of the more interesting,
aspects of this historical perspective is that the majority of the studies
undertaken, including some of the very earliest, were in response to some
perceived pollution problem of the day. This long succession of practically
oriented studies has provided a record of extensive population replacement in
phytoplankton communities, and some indication of change in absolute abundance
of populations and modification of seasonal population dynamics.
Although there is little doubt that the major factor driving algal
succession in Lake Michigan is phosphorus pollution due to both its primary and
secondary effects, there are undoubtedly other effects which are partially
masked by this overriding factor. Perhaps the least understood of these is the
effect or effects of increasing conservative ion abundance. It has long been
recognized that there are striking differences in the algal floras in waters of
different salinities. It is also very apparent that many of the algal
populations which have invaded the Great Lakes during the past few decades are
characteristically found in high salinity environments. This particular
modification is, of course, true not only of algal populations but of consumer
organisms as well. The actual physiological and/or ecological mechanisms
operating have not been satisfactorily determined. It is clear, however, that
further modification of the indigenous biota is highly undesirable, and that if
-------
conservative ion contamination is a major contributory factor, it poses a very
serious problem due to the very long residence times of the Great Lakes and the
difficulty in controlling sources.
At the present time the most pronounced and complicated effects of
multiple loadings occur in the nearshore waters. This zone is also the region
of most intensive physical effects. Local and transient advection regimes may
cause gross variations in the dispersion of pollutants entering the lake and,
as would be expected, the influence of these materials on the algal flora may
be highly variable. These regions may thus show a long term statistical trend
in population modification but, at any given time, these trends may be
submerged by local effects of transient intensity.
The present project deals with a limited area of Lake Michigan along the
Indiana coastline. This region lies within the area of Lake Michigan which has
been extensively modified by factors which affect phytoplankton occurrence and
abundance. Several qualitatively different local sources are present, and the
effect of these sources on phytoplankton composition and abundance are of
special interest because adjacent regions of the lake are intensively utilized
for both recreational purposes and as a source of potable water.
The primary objectives of the project, which is part of a more
comprehensive investigation, are the following:
1. To determine the composition and abundance of the phytoplankton flora
in comparison with past conditions to the extent that they are known, and
provide firm documentation for comparison with future studies;
2. To determine if there are occurrence patterns of specific
phytoplankton physiological group populations which may reflect the effects of
specific sources;
-------
3. To determine if distribution patterns In the phytoplankton are
oorrelafced with particular chemical or other blotio paramettrs which may
indicate a cause-effect relationship.
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MATERIALS AND METHODS
"X
The sampling array utilized in this study is shown in Figure 1. Sampling
was conducted on 11 June, 20 August, and 24 September, 1977. Four transects
were analyzed with stations located 1/4, 1/2, 1, and 2 miles offshore. The
eastern-most transect did not have a 2 mile station. For each station a 2 m
and bottom sample were analyzed. All samples were collected by the U.S.
Environmental Protection Agency.
All samples for phytoplankton population analysis were taken as 250 ml
splits of the original 5-liter Niskin Bottle cast. These subsamples were fixed
with a Lugols solution and stored. For subsequent analysis, the sample bottles
were agitated and a 50 ml aliquot was removed. Material was concentrated by
filtration onto 25 mm "AA" Millipore filters, partially dehydrated through an
ethanol series, and embedded in clove oil. Prepared filters were mounted on a
50 x 75 mm glass slide and covered with a 43 x 50 mm #1 cover glass.
Preparations were kept in a horizontal position and allowed to dry for
approximately two to four weeks, during which time embedding medium lost by
volatization was periodically replaced. When the filter was completely
cleared, the edges of the cover glasses were sealed with paraffin.
Slides were analyzed by visual counts of phytoplankton cells present using
Leitz Ortholux microscopes fitted with fluorite oil 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
average of two 10 mm radial strips counted. Effective filtration diameter in
the filtration apparatus used is 20 mm.
Raw counts were transformed to computer format on punched cards. Computer
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87° 20'
87° 10'
87°00f
• LM 01
• LM 02
0LM03
I IND 38
IND 44
(Jl
IND30
• IND 3i
MND32
IND 37
• IND 39
BURNS V HARBOR
FIG. 1. Sampling station locations; southern Lake Michigan, 1977.
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data summaries are available for all samples counted (see Stoermer and Krels,
in press). Summaries include estimates of absolute frequency and assooiated
error, and an estimate of relative abundances for individual taxa as well as
major algal divisions. Assemblage parameters calculated included 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. Summary information is stored
on magnetic tape and is available for further data anlysis.
Various physico-chemical analyses were conducted by the EPA at the time
the samples were collected, and they provided this information to us. Contour
plots for these data are presented in Appendix Figures 1-33.
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RESULTS
OVERALL ABUNDANCES OF MAJOR ALGAL GROUPS
Relative and absolute average abundances of major algal groups for a given
cruise are presented in Table 1. Highest overall densities were attained by
blue-green algae and diatoms, with greens, ehrysophytes, and cryptomonads,
secondarily important. The undetermined category consists almost entirely of
mioroflagellates which presumably belong to the Haptophyceae (Stoermer and
Sicko-Goad, 1977; Sicko-Goad, Stoermer, and Ladewski, 1977). Total absolute
abundances for the three cruises are presented in Figure 2, A total of 288
taxa were identified and recorded. The average total density for all samples
was 4420 cells/ml, ranging from 844 to 12,078 cells/ml.
In June, depending on the station, either blue-green algae, diatoms, or
haptophytes were the major group present. At Gary Harbor, haptophytes were
dominant at the two offshore stations, with diatoms dominant nearshore. At
Burns Harbor, diatoms were the dominant group at all stations except the 1/2
mile station, where blue-green algae dominated the assemblage. At the Indiana
Dunes transect, diatoms were the most numerous at the near- and offshore
stations, with haptophytes dominant at the 1/2 mile and 1 mile stations,
composing 57 and 50% of the total community respectively. Along the
eastern-most transect near Michigan City, diatoms were dominant at the two
nearshore stations, averaging 55% of the population, with blue-green algae
dominant at the 1 mile station, composing about 38$ of the community. Over all
15 stations in June, diatoms averaged 35.8$ and blue-green algae averaged 18,6$
of the total phytoplankton.
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TABLE 1. STATISTICAL SUMMARY OF MAJOR ALGAL GROUPS IN SOUTHERN LAKE MICHIGAN, 1977.
co
June
Blue-greens
Greens
Diatoms
Chrysophytes
Cryptomonads
Dino flagellates
Undetermined
Ave. Relative
Abundance %
18.60
8.01
35.82
8.52
4.99
0.69
22.59
Ave.
Cells/ml
423.49
168.11
780.50
224.38
122.87
13.26
581.26
August
Ave. Relative
Abundance %
51.55
17.37
17.33
1.32
3.41
0.36
5.38
Ave.
Cells/ml
2038.82
697.15
680.53
52.78
136.69
14.10
213.77
September
Ave. Relative
Abundance %
50.48
7.76
23.42
1.92
6.64
0.18
2.61
Ave.
Cells/ml
1683.05
249.93
757.60
59.48
207.91
5.73
82.52
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JUNE 77
20 AUG. 77
FIG. 2. Seasonal Distribution and Abundance Trends of the Total
Phytoplankton Assemblage.
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In the August sampling period, blue-green algae were the dominants at all
stations along all four transects. They ranged from a low of 33$ of the total
algal assemblage at station 33 to 6f% at station 37. The diatom component
ranged from 9 to 28$ of the total assemblage. The green algae composed
approximately the same proportion of the community as did the diatoms, ranging
from 12 to 28$.
In Septembers blue-green algae maintained their dominance. Only at the 1
mile station off Burns Harbor and Gary Harbor did the diatoms dominate. Over
all 15 stations, blue-green algae averaged 52% (Table 1) of the total community
and reached a maximum of 5B% at the 1 mile station at Indiana Dunes. Diatoms
composed 23% of the total and were more numerous at the western-most two
transects, possibly as a response to the higher silica values.
REGIONAL AND SEASONAL TRENDS IN ABUNDANCE OF SELECTED TAXA
Hass . (Fig. 3)
This species occurs in all regions of the Great Lakes, and appears to be
eurytopic. In southern Lake Michigan, it seemed to be fairly sensitive to
silica levels. In June, it was found in higher numbers offshore and along the
Gary Harbor transect, where all silica values were above 0.30 mg/1 (Appendix
Fig. 22). In August, it was present in low densities, not over 30 cells/ml.
It was found at its maximum at the 1/2 mile station off Burns Harbor, with a
silica value of 0,58 mg/1 (Appendix Fig. 23). This large silica value was
probably the result of an isolated "slug" of river water derived from Burns
10
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Harbor and entrained in a local circulation gyre. The effect of this "slug"
was also noted in various other species examined. Highest abundances of _A.
formosa were present in September, probably related to the higher silica values
present in this month (Appendix Fig. 24).
Cvclotella comeqsj.s (Grun.) V.H. (Fig. 4)
This species is a relatively recent introduction into Lake Michigan, and
its ecological affinities are not well known. In Saginaw Bay in 1974, it
appeared in bloom quantities in August, and was still abundant into October
(Stoermer and Kreis, in press). They also noted that it was able to tolerate
very low levels of silicon. In southern Lake Michigan, a similar seasonal
effect was present. It was found in very low numbers in June, but increased
substantially in the August and September sampling periods. Abundances of this
species appeared to be highest near shore and along the Gary Harbor and Burns
Harbor transects, possibly displaying a high tolerance for more perturbed
areas. Analysis of variance determined that, in August, densities were
significantly lower (.05 level) at the offshore stations on each transect than
at the three nearshore stations. Additionally, significant positive
correlations at the .01 level were found with NO,, NH~, and conductivity in
both August and September. However no such significant correlations were found
with silica.
Cvclotella crvptica Reimann. Lewin, and Guillard (Fig. 5)
This species was originally described from a brackish-water habitat
(Reimann .gi. JLL«, 1963). Most of the records of its occurrence in Lake Michigan
come from harbors and inshore areas subject to high chloride levels (Stoermer
12
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II JUNE 77
20 AUG. 77
FIG. U. rtistribution of gvclotella comensis.
13
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JUNE 77
20 AUG. 77
FIG. 5. Distribution of Cyclotelja crvp.t4.ca.
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and Yang, 1969). In southern Lake Michigan, it was found in low numbers in
June and September. However, in August, it was found in fairly high densities
near shore along the Gary and Burns transects. A maximum density of 180
cells/ml was found at the 1 2 mile station at Burns Harbor, probably due to the
presence of river water derived from the harbor. In August, £. cryptica was
significantly correlated with conductivity, NO-, Si02, and aerobic heterotrophs.
Cyclotella pseudostelligera Hust. (Fig. 6)
Populations of this species are usually found in eutrophied areas. Its
range in the Great Lakes appears to be restricted to harbors and river mouths
(Stoermer and Ladewski, 1976). It was present in southern Lake Michigan in low
numbers in June and September. However, in August, it had a distribution
similar to Cyclotella cryptica. A maximum density was found at the 1/2 mile
station at Burns Harbor once again, where it appears that the river water is
having a great effect on the makeup of the algal community. High numbers were
also found at the 1 mile station at Burns Harbor, and the 1/4 mile station at
Gary. Similar to £. cryptica, it also was found to be significantly correlated
with conductivity, NO-, SiO,,, and aerobic heterotrophs in August.
Cyclotella stelligera (Cl. & Grun.) V.H. (Fig. 7)
This species has been reported to be intolerant of high levels of
eutrophication, and is usually removed from regions of the Great Lakes which
have undergone extensive perturbation. Hohn (1969) reported that its abundance
in Lake Erie has declined since the 1930's. In southern Lake Michigan, it was
present in highest numbers in the August and September cruises. In August, the
15
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JUNE 77
20 AUG. 77
FIG. 6. Distribution of Cvolotella pseudostelligera.
16
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20 AUG. 77
FIG. 7. Distribution of Cvclotella
17
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analysis of variance procedure demonstrated that, at the 5% level of
significance, higher numbers were found at the less disturbed eastern-most two
transects than at Gary or Burns Harbor. In June and September, no trends were
apparent. No significant correlations were found for C. stelligera versus any
physico-chemical parameter monitored for the three sampling dates.
Fragilaria crotonensis Kitton (Fig. 8)
This species is one of the most common plankton diatoms. It is present in
all the Great Lakes, and can tolerate a wide range of ecological conditions.
As in Saginaw Bay in 1974 (Stoermer and Kreis, in press) densities were lowest
in August, with only isolated low level populations found. Highest densities
were recorded in September, with a decreasing offshore trend apparent. In this
month it exhibited a significant positive correlation at the .01 level with
conductivity, N0~, NH~, and SiO-. In June, densities were intermediate between
August and September values, with no trends evident.
Nitzschia acicularis Win. Sm. (Fig. 9)
This species is widely distributed in the Great Lakes. In southern Lake
Michigan, in June, its distribution was erratic, although it was found in
slightly higher numbers at the Burns Harbor transect. Populations declined to
very low numbers in August, similar to the seasonal pattern observed in
southern Lake Huron (Stoermer and Kreis, in press). Densities increased in
September, attaining their highest values, with greatest abundances tending to
be concentrated along the nearshore areas and the Gary and Burns Harbor
transects. In September, significant positive correlations at the .01 level
were found with conductivity, NO-, NH-j, SiO^, and aerobic heterotrophs.
18
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JUNE 77
20 AUG. 77
FIG. 8. Distribution of Fragilaria crotonensis.
19
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I JUNE 77
20 AUG. 77
FIG. 9. Distribution of NitzsQfria, acicularis.
20
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Nitzschia fonticola Grun. (Fig. 10)
This species has predominantly been recorded from nearshore localities in
the Great Lakes (Stoermer and Yang, 1969). In June, its distribution was
erratic, with no trends evident. Its numbers declined in August, and it was
not present at all at the offshore stations. By September, it attained its
highest densities. Like N_. acicularis it demonstrated a preference for the
nearshore regions and for the Gary and Burns Harbor transects. In September,
it was found significantly correlated at the .01 level with N03, NH3, and
aerobic heterotrophs. Overall, its distribution appears to be fairly similar
to N. acicularis, and it too displays a tolerance for polluted conditions.
Nitzschia palea (Kutz.) Wm. Sm. (Fig. 11)
Stoermer and Yang (1969) noted that most of the records for this species
in Lake Michigan come from polluted harbors and river mouths. In this study,
it reached its greatest abundance in June, and displayed definite affinities
for the Gary and Burns Harbor regions. On this first cruise, it was found to
be significantly correlated at the .05 level with N03 and NH3> Its numbers
decreased in August and September. Larger densities were found at the
nearshore stations than at the furthest offshore station for all transects in
the latter two months.
Stephanodiscus minutus Grun. (Fig. 12)
This species has been reported to be a winter dominant in mesotrophic to
eutrophic lakes (Huber-Pestalozzi, 1942). In Lake Michigan, Stoermer and Yang
(1970) noted that it becomes abundant in early spring collections from certain
near and offshore localities. They also noted that it was more abundant in
21
-------
I JUNE 77
20 AUG. 77
24 SEPT. 77 720
FIG. 10. Distribution of Nitzschia fonticola.
22
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U)
-------
JUNE 77
20 AUG. 77
•150
J> /100
24 SEPT. 77 /0
FIG. 12. Distribution of Steohanodiscus minutus.
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1967 than 196U. In June, in southern Lake Michigan, this species was present
in fairly high numbers, and displayed a preference for the more eutrophied Gary
and Burns Harbor regions. By August and September, its numbers declined
drastically and it was present in very low numbers at a few stations.
Synedra filiformis Grun. (Fig. 13)
This species has been recorded mainly from offshore regions in Lake
Michigan, and Stoermer and Kreis (in press), regard it as one of the
characteristic species of the offshore phytoplankton in the upper Great Lakes.
However, Cleve-Euler (1953) noted that it can tolerate brackish water. In
September, it was found in greatest abundance in the polluted Gary Harbor
region, and it decreased moving east to Michigan City. Its abundance was also
found to correlate highly with conductivity, NO., and NH, at the .01 level.
Its numbers were very low in June and August at all stations.
Tabellaria flocculosa var. linearis Koppen (Fig. 14)
This species was present at scattered stations in June. By August, its
numbers declined, similar to the occurrence pattern noted in southern Lake
Huron (Stoermer and Kreis, in press). In September, large populations occurred
at the two nearshore stations at Gary Harbor (Fig. 14). Generally, in
September, offshore densities were lower than they were near shore. It also
exhibited significant positive correlations with NO- and SiOp at the .01 level
in September.
25
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JUNE 77
20 AUG. 77
FIG. 13. Distribution of Svnqflra fijiformia.
26
-------
I JUNE 77
20 AUG. 77
FIG. 14. Distribution of Tabellaria flocculosa var. linearis.
27
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Chlorophyta
Chlamvdomonas spp. (Fig. 15)
This green flagellate was a dominant in the system in August, and occurred
only in minimal numbers in June and September. In August, it displayed highest
densities at the three nearshore stations at Gary and Burns Harbor. This
species correlated at the .01 level in August with NO., and NH,. Stoermer j§.t
al. (1975) noted that Chlamvdomonas spp. was abundant in some areas of Lake
Ontario, and reached its maximum populations around July.
Scenedesmus spp. (Fig. 16)
The genus JScjen.ed.esro.us. was found in fairly high numbers, and was
represented by a variety of different species. Most species of Scenedesmus
reported from the Great Lakes prefer eutrophic waters. In southern Lake
Michigan, it was found in approximately similar numbers over all three dates
with no trends apparent within a given cruise. Further substantiating this
lack of habitat preference is the fact that no significant correlations were
found when compared to any physico-chemical parameters.
CrvptoDhvta
Crvptomonas pyata Ehr,- (Fig. 17)
This species is very common in all regions of the Great Lakes. In this
study, over all three cruises it exhibited affinites for both the nearshore
waters and the Gary and Burns Harbor regions. It does not appear to exhibit
any seasonal trends. In both August and September, it correlated highly (.05
level) with conductivity, N0_, and NH.,.
28
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-------
I JUNE 77
FIG. 16. Distribution of Scenedesmus spp.
30
-------
II JUNE 77
20 AUG. 77
FIG. 17. Distribution of Cryptomon^s oyata.
31
-------
QvanoDhvta
Anabaena flos-aouae (Lyngb.) Breb. (Fig. 18)
Low levels of this species are found consistently in the Great Lakes;
however, high densities are found only in the more eutrophic regions within the
system. Stoermer and Kopczynska (196?) found the maximum abundance of J,.
flos-aouae in southern Lake Michigan to be on the same order as in eastern Lake
Ontario. In this study in June, it was found at only three of the stations
sampled. By August, it was found scattered in about half of the stations, with
a maximum occurrence at the nearshore station at Indiana Dunes. In September,
it was found at 10 stations, with no trends apparent.
Anacvstis incerta Dr. & Daily (Fig. 19)
This species is common in the summer and fall phytoplankton assemblages in
the Great Lakes. Stoermer £jb. Jti.- (1975) noted that this species is most
successful under conditions of silica depletion. In the June cruise, this
species was not present to any significant extent. By August, it increased
greatly, and was dominant at every station. It maintained these high numbers
into September, and remained as one of the dominants. No trends could be
detected within the sampling scheme, and this may be due to its pattern of
indeterminate colonial growth, which causes varying degrees of error in
abundance estimates.
Qscijlatoria bornetii Zukal (Fig. 20)
This species has previously been reported from Lake Michigan mainly at the
thermocline depth during summer stratification, but rarely in the surface
32
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7
JUNE 77
20 AUG. 77
FIG. 18. Distribution of Anabaena fjos-aquae.
33
-------
20 AUG. 77
24 SEPT. 77 / 1000
FIG. 19. Distribution of Anacvstis jtiQerta.
-------
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waters. It has only occasionally been found in abundance in the upper Great
Lakes. In southern Lake Michigan, in June, it was one of the dominants. It
tended to be in higher densities both nearshore and at the Gary and Burns
Harbor regions. In August, it decreased in numbers, and only the 1/2 mile
station off Michigan City had an extensive population. It increased slightly
in September, with highest abundances along the Gary Harbor transect.
Microflagellates
Haptophvte sp. #1 (Fig. 21)
One group of flagellates which may be playing an increasingly larger role,
especially in the Lake Michigan phytoplankton assemblages, are the
haptophytes. Little is known about the freshwater ecology of this primarily
marine group. Chrvsochromulina parva has been reported from both Lake Erie and
Lake Ontario. Munawar and Munawar (1975) regard it as one of the most
numerically abundant species in the St. Lawrence Great Lakes. In Lake Ontario,
Stoermer .§_£. .ai.. (1975) found Chrvsochromulirxa Darya to be abundant, with its
largest populations occurring in June and July. In southern Lake Michigan,
Haptophyte sp. #1 was a dominant component of the system in June. Lowest
densities were recorded at the 1/4 mile stations at each transect, and it
appeared as if some type of nearshore inhibition effect was occurring. Highest
abundances were found along the Gary Harbor and Indiana Dunes transects.
Numbers decreased in August, with abundances lowest at the offshore stations.
Densities further decreased into September, where this species played only a
minor role in the system.
36
-------
-------
DISCUSSION
There is no doubt that diatoms as a group have decreased in dominance in
south Lake Michigan since the early 1960's, when Stoermer and Kopczynska (1967)
found them dominant at all stations and all months. The diatoms that are now
of consequence are typically those species associated with varying degrees of
eutrophication. Green and blue-green algae are composing larger portions of
the phytoplankton assemblages. They can outcompete diatoms, especially in the
summer, under conditions of low silica and high temperatures. In this study,
Anacvstjs incerta was the dominant taxon in both August and September.
Additionally, phytoflagellates are now a major part of the Great Lakes system
(Munawar and Munawar, 1975).
Within the past 50 years, chloride concentrations have been increasing in
the Great Lakes. Beeton (1965) noted that chloride levels, along with other
conservative elements, have been increasing in Lake Erie, Lake Ontario, and
Lake Michigan since the early 1900's. A number of marine and halophilic algal
species have been recorded in the Great Lakes, with most of these reported
within the last twenty years. Stoermer (1978) noted that most of the
phytoplankton species which have invaded the Great Lakes are halophilic in
nature. In 1977, the brackish-water species BiddulDhia sp. and Terosinoe
musica were recorded from southern Lake Michigan for the first time (Wujek,
pers. comm.). In this study, a variety of salt tolerant forms were present in
fairly high numbers, including Cvclotella crvptica, Cyclotella
pseudostelligeraf pia^oma tenue var. eloncatum. and Synedra filiformis. Also,
two species of Skeletonema. a brackish-water genus, were found. Haptophytes
were found as a dominant in June, and this group appears to be increasing in
38
-------
abundance in the Great Lakes.
Aside from the halophilic forms, other species typical of eutrophic waters
were present. Many of the diatoms found in abundance were species described by
Stoermer and Yang (1969) as tolerating moderately disturbed portions of the
Great Lakes. Included in this group are Asterionella formosa, Fragilaria
crotonensis. Stephanodiscus alpinus, Stephanodiscus minutus, and Synedra
ostenfeldii. Other species found in southern Lake Michigan that are common in
disturbed areas include Nitzschia spp., Stephanodiscus hantzschii and
Stephanodiscus subtilis. In the green algae, the genus Scenedesmus is common
in eutrophied areas. It was also noted that, in many instances, those species
which were found to tolerate disturbed waters were found in higher densities at
the Gary Harbor and Burns Harbor regions than at the eastern-most two transects.
One of the more striking aspects of phytoplankton distribution in the area
of study is the atypically large abundance of species of the genus Nitzschia,
particularly species such as flu palea and other forms which are often found in
areas with extremely degraded water quality conditions. Cholnoky (1968) and
others have noted that many members of this genus are often associated with
high levels of organic or reduced nitrogen compounds. Species such as N^. palea
are, in fact, often considered to be indicative of this type of pollution.
Although NH, levels are not extremely elevated at the stations studied, our
data suggest that this type of perturbation may be an important factor in the
area of study. This hypothesis is further enhanced by the fact that the
occurrence of Nitzschia species reported to be tolerant of organic loadings is
positively correlated with estimates of aerobic heterotroph abundance developed
and furnished to us by the EPA Region V laboratories.
In the August cruise, with low silicon levels and increased temperatures,
39
-------
diatoms were found in low densities . Only Cvclotella comensis and Cvclotella
were able to thrive under these conditions to any significant
extent. Both of these species have been reported to be extremely tolerant of
low silica levels, and it appears they can outcompete other species when such
conditions exist. It is interesting to note that in August, £.. opmensls. was
found in higher numbers along the more polluted Gary and Burns transects , while
£.. stellieera was recorded in greater abundances at the less disturbed
eastern-most two transects.
The sudden dominance of Pyc^otej.^ comensis. a diatom which , so far as we
have been able to ascertain, was exceedingly rare in Lake Michigan prior to
1975 is difficult to interpret. This species has become an important element
of the flora throughout the lake (GLRD, unpublished data) during the summer and
fall. Similar blooms have been noted in Lake Huron (Lowe, 1974; Stoermer and
Kreis, in press). Although the ecological tolerance of this species is very
poorly known, it is usually reported from oligotrophic systems which are under
some nutrient stress. Based on data from Lake Huron, the species is very
tolerant of low levels of dissolved silica but does not tolerate nitrate
depletion (Stoermer and Kreis, in press). In Lake Huron it forms large late
summer and fall blooms in the interface waters of Saginaw Bay and Thunder Bay.
It is interesting to note that £.. comensis has apparently effectively replaced
£.. michiganiana . an indigenous species which was previously a consistent summer
dominant in Lake Michigan. Although there may be several plausible
explanations for this, it would appear that the superior competetive ability of
£.• comensis may be related to its tolerance of low silica levels, and thus
related to continued phosphorus stress on the system.
It should be recognized that , due to the timing of collections in the
-------
present study, maximum levels of phytoplankton standing crop were probably not
encountered. Previous studies have shown that maximum phytoplankton density
and maximum regional differentiation of the flora occur during the spring
thermal bar period. In most instances, phytoplankton abundance in the
nearshore zone, except in the immediate vicinity of strong sources, is on
average lower, but extremely variable following stratification. The samples
reported here thus represent a "best case" situation so far as illustrating the
effects of eutrophication and salinification on the phytoplankton flora is
concerned. It would be reasonable to expect much larger and better defined
trends within the area of study during the spring thermal bar period when the
dispersion of inputs tends to be constrained by the thermal bar.
Another interesting result of the study is the documentation of the
increasing importance of microflagellates in the Lake Michigan phytoplankton.
In the Great Lakes system, extreme abundance of these organisms is generally
associated with regions which have undergone extensive modification.
Unfortunately the taxonomy of microflagellates in the Great Lakes is very
poorly known since many of them can be identified with certainty only with the
aid of the electron microscope. Because of their increasing ecological
importance more research should be devoted to determining what entities are
present and to developing techniques whereby reliable population estimates can
be made.
One of the characteristics which appears to distinguish the phytoplankton
flora of the study area from that of previously studied nearshore localities is
the abundance of filamentous blue-green algae. Although the Cyanophyta have
become more abundant in the offshore waters of Lake Michigan in the past
decade, the most numerically important forms are generally coccoid species.
-------
Although these forms are also a dominant element of the phytoplankton flora in
the study area, filamentous species are relatively more abundant than expected.
Running concurrently with this study was an investigation into the
phytoplankton assemblages of Green Bay (Stoermer and Stevenson, in press). The
phytoplankton components of both systems are highly comparable. The dominant
taxa of Green Bay for May, August, and October 1977 included Anacvstis incerta.
£yclotel,la comensis, Gloeocystis planctonica. and Rhodomonas minuta. These
species were also of major importance in southern Lake Michigan in 1977- Total
densities were higher in Green Bay, averaging 5400 cells/ml, while southern
Lake Michigan averaged only 4400 cells/ml.
The August sampling period in Green Bay was also dominated by the
Cyanophyte Anacvstis incerta. with Cvclotella comensis the dominant diatom.
Cvclotella stellicera was not present in appreciable numbers in Green Bay,
possibly due to the more perturbed conditions found there than at the
eastern-most two transects of southern Lake Michigan where it was found in
fairly high abundances. Phytoflagellates were also of importance in Green Bay
in August.
In October in Green Bay, similar to the September sampling period in this
study, Anacvstis incerta was still the dominant species at a majority of
stations with diatoms and phytoflagellates secondarily important. It is
interesting to note that, for all of the sampling dates, the flagellate
composition was very similar. Species of consequence common to both systems
include: Qhroomonas spp., Crvptomonas marssonij.r Crvptomonas ovata, Qchromonas
spp., Qchronusnas vallesiaca. Rhodomonas minuta. and undetermined haptophytes.
In 1971 and 1972, GLRD collected and analyzed samples along the Burns
Harbor transect. This allowed for the comparison of the phytoplankton
42
-------
assemblages on a temporal scale. In June 1971, at the 1/4 mile station, a
plume emerging from Burns Ditch was intersected and a bloom condition of 31,000
cells/ml was recorded. Diatoms, most of which were Gentries, composed 98$ of
the assemblage. The plume did not reach the three stations further offshore,
and total numbers averaged only 2500 cells/ml, with Rhizosolenia cracilis the
dominant taxon. Diatoms as a group were also dominant, averaging 70% of the
phytoplankton component. In June 1972, diatoms were once again most numerous,
averaging 93$ of the assemblage. The major taxa included Steohanodiscus tenujs
and £. minutus. In June 1977, the assemblage was different than five and six
years previous. The blue-green algal filament Oscillatoria bornetii and
undetermined haptophyte species were most numerous. Diatoms as a group were
still dominant, but only composed 38$ of the assemblage. Blue-green algae
increased to 23$ of the phytoplankton component, whereas in 1971 and 1972 they
averaged only about 2.5$. Phytoflagellates as a group increased dramatically
in importance, averaging 31$ of the assemblage in June 1977, while in 1971 and
1972 they averaged only M.2 and 1.5$ respectively.
The August phytoplankton assemblage in 1977 appeared to have changed from
the earlier studies. In 1977, the blue-green algae, mainly due to Anacvstjs
incerta. were dominant, while diatoms as a group were most abundant in 1971 and
1972. In 1971 and 1972, blue-green algae averaged about 23$ (300 cells/ml) of
the assemblage, while in 1977 they averaged about 52$ (2030 cells/ml) off Burns
Harbor. However, the blue-green algal species present over the three years
were similar, mainly belonging to the genera Anacvstis and Gomphosphaeria. As
in June, flagellates were found in much higher abundances in 1977 than in the
previous years. In 1971 and 1972 they averaged 7$ (180 cells/ml) and 1$ (1H
cells/ml) respectively, and increased to 22$ (890 cells/ml) of the assemblage
-------
in 1977.
In September, blue-green algae were dominant over all three years,
averaging 66$ (1200 cells/ml), 61$ (3500 cells/ml), and 49$ (1660 cells/ml) for
1971, 1972, and 1977 respectively. Interestingly, Anaqvstis incepta was the
dominant taxon for all three years. Diatoms composed a larger portion of the
assemblage in 1977 due to the appearance of CycloteHa comensis. a species not
found in the earlier two years. Once again, flagellates were found in greater
abundances in 1977 (14$), than in 1971 (1$) or 1972 (3$).
From the analysis of the phytoplankton component over the three years,
some definite assemblage shifts can be noted. These include:
1. An increase in filamentous blue-green algae in 1977;
2. An earlier seasonal dominance of blue-green algae in 1977, to the
point that they are found in higher abundances in June, and are dominant in
August;
3. Extremely large increases in the flagellate component;
4. A decrease in the relative abundance of the diatom component in May
and June, with it now being dominated by Cvclotella comensis and £.. stellicera
in the summer months under silica-limited conditions.
It still appears that the cultural eutrophication of southern Lake
Michigan is continuing, albeit at a slower rate than five to ten years ago.
Under silica-depleted summer conditions, blue-green algae, phytoflagellates,
and low-silica-tolerant diatoms are now the dominant phytoplankters in the
system. However, those diatom species characterized by Stoermer and Yang
(1969) as thriving only in disturbed habitats are not present in large
abundances in 1977 in southern Lake Michigan, although it is possible that they
may have been present in April and May under thermal bar conditions.
-------
REFERENCES
Beeton, A. M. 1965. Eutrophication of the St. Lawrence Great Lakes.
Limnol. Oceanogr., 10:240-254.
Cholnoky, B. J. 1968. Die Okologie der diatomeen in Binnengewassern.
Verlag von J. Cramer, Lehre. 699 pp.
Cleve-Euler, A. 1953. Die Diatomeen von Schweden und Finnland. Teil II.
Arraphidae, Brachyraphidae. Kungl. Svenska Vet. - Akad. Handl., Fjarde
Serien, 4(1):1-158.
Hohn, M. H. 1969- Qualitative and quantitative analyses of plankton
diatoms, Bass Island area, Lake Erie, 1938-1965, including synoptic
surveys of 1960-1963. Ohio Biol. Surv., N. S., Vol. 3, No.1. 211 pp.
Huber-Pestalozzi, G. 1942. Das Phytoplankton des Susswassers, Teil 2,
2 Halfte. Diatomeen. Jn: Thienemann, A. (Ed.), Die Binnengewasser, Band
16, pp. 366-549.
Lowe, R. L. 1974. Environmental requirements and pollution tolerance of
freshwater diatoms. EPA-670/4-74-005, 333 pp.
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.
Reimann, B. E. F., J. M. Lewin, and R. R. L. Guillard. 1963. Cvclotella
crvpfrica. a new brackish water diatom species. Phycologia, 3(2):76-84.
Sicko-Goad, L., E. F. Stoermer, and B. G. Ladewski. 1977. A morphometric
method for correcting phytoplankton cell volume estimates. Protoplasma,
93:147-163.
Stoermer, E. F. 1978. Phytoplankton assemblages as indicators of water
quality in the Laurentian Great Lakes. Trans. Amer. Micros. Soc., 97:1-16.
Stoermer, E. F., and E. E. Kopczynska. 1967. Phytoplankton populations
in the extreme southern basin of Lake Michigan, 1962-1963, pp. 19-46.
In; J. C. Ayers and D. C. Chandler, Studies on the environment and
eutrophication of Lake Michigan. Univ. Michigan, Great Lakes Res. Div.,
Spec. Rep. No. 30.
Stoermer, E. F., and R. G. Kreis. In press. Phytoplankton composition and
abundance in southern Lake Huron. Univ. Michigan. Great Lakes Res Div.
Special Report No. 66. 382 pp.
Stoermer, E. F., and T. B. Ladewski. 1976. Apparent optimal temperatures
for the occurrence of some common phytoplankton species in southern Lake
Michigan. Univ. Michigan, Great Lakes Res. Div. Publ. No. 18. 48 pp.
-------
Stoermer, E. F., and L. Sicko-Goad. 1977. A new distribution record for
Hvmenomonas roseola Stein (Prymnesiophyceae, Coccolithophoraceae) and
Spiniferomonas triorali? Takahashi (Chrysophyceae, Synuraceae) in the
Laurentian Great Lakes. Phycologia, 16(4):355-358.
Stoermer, E. F., and R. J. Stevenson. In press. Green Bay phytoplankton
composition, abundance, and distribution.
Stoermer, E. F., and J. J. Yang. 19&9. Plankton diatom assemblages in Lake
Michigan. Great Lakes Res. Div., Univ. Michigan, Spec. Rep. No. 47. 268
pp.
Stoermer, E. F., and J. J. Yang. 1970. Distribution and relative abundance
of dominant plankton diatoms in Lake Michigan. Univ. Michigan, Great
Lakes Res. Div. Publ. No. 16. 64 pp.
Stoermer, E. F., M. M. Bowman, J. C. Kingston, and A. L. Schaedel. 1975.
Phytoplankton composition and abundance in Lake Ontario during IFYGL.
Univ. Michigan, Great Lakes Res. Div., Spec. Rep. No. 53. 373 PP.
-------
BURNS » HARBOR
Appendix Figure 1. Temperature contours, southern Lake Michigan; 11 June, 1977.
-------
OO
BURNS V HARBOR
Appendix Figure 2. Temperature contours, southern Lake Michigan; 20 August, 1977.
-------
BURNS » HARBOR
Appendix Figure 3. Temperature contours, southern Lake Michigan; 2U September, 1977.
-------
VJI
O
BURNS B HARBOR
Appendix Figure M. Conductivity contours, southern Lake Michigan; 11 June, 1977.
-------
87° 20'
87° 10'
8 7° 00'
VJl
BURNS K HARBOR
Appendix Figure 5. Conductivity contours, southern Lake Michigan; 20 August, 1977.
-------
IM
BURNS V HARBOR
Appendix Figure 6. Conductivity contours, southern Lake Michigan; 21 September, 1977.
-------
87° 20'
87° 10'
87° 00'
u>
£.0
BURNS B HARBOR
GARY
Appendix Figure 7. Secchi disc contours, southern Lake Michigan; 11 June, 1977.
-------
-------
BURNS K HARBOR
Appendix Figure 9. Secchi disc contours, southern Lake Michigan; 24 September, 1977.
-------
87° 20'
87° 10'
87°00f
CTi
BURNS I HARBOR
41°40'
Appendix Figure 10. Contours for pH, southern Lake Michigan; 11 June, 1977.
-------
BURNS I HARBOR
Appendix Figure 11. Contours for pH, southern Lake Michigan; 20 August, 1977.
-------
CO
BURNS V HARBOR
Appendix Figure 12. Contours for pH, southern Lake Michigan; 24 September, 1977.
-------
87° 20'
87° 10'
8 7° 00'
1OB
110
BURNS K HARBOR
Appendix Figure 13- Alkalinity contours, southern Lake Michigan; 11 June, 1977.
-------
CTl
o
BURNS V HARBOR
Appendix Figure 14. Alkalinity contours, southern Lake Michigan; 20 August, 1977.
-------
BURNS I HARBOR
Appendix Figure 15. Alkalinity contours, southern Lake Michigan; 24 September, 1977.
-------
0\
ro
BURNS V HARBOR
Appendix Figure 16. NO_-N contours, southern Lake Michigan; 11 June, 1977.
-------
CO
BURNS K HARBOR
Appendix Figure 17. NO--N contours, southern Lake Michigan; 20 August, 1977.
-------
en
-tr
BURNS I HARBOR
Appendix Figure 18. NO--N contours, southern Lake Michigan; 24 September, 1977.
-------
ON
VJ1
BURNS » HARBOR
Appendix Figure 19. Ammonia contours, southern Lake Michigan; 11 June, 1977.
-------
87° 20'
87° 10'
87° 00'
41° 40'
BURNS I HARBOR
Appendix Figure 20. Ammonia contours, southern Lake Michigan; 20 August, 1977.
-------
BURNS V HARBOR
Appendix Figure 21. Ammonia contours, southern Lake Michigan; 24 September, 1977.
-------
ON
OO
Si02 2m
mg/Jt
JUNE 1977
BURNS I HARBOR
Appendix Figure 22. Silica contours, southern Lake Michigan; 11 June, 1977.
-------
cr>
10
BURNS V HARBOR
Appendix Figure 23. Silica contours, southern Lake Michigan; 20 August, 1977.
-------
BURNS V HARBOR
Appendix Figure 24. Silica contours, southern Lake Michigan; 24 September, 1977.
-------
BURNS I HARBOR
Appendix Figure 25. Anaerobic heterotroph contours, southern Lake Michigan; 11 June,
1977.
-------
87° 20'
87° 10'
8 7° 00'
ro
BURNS V HARBOR
Appendix Figure 26. Anaerobic heterotroph contours, southern Lake Michigan; 20 August,
1977.
-------
Appendix Figure 27. Anaerobic heterotroph contours, southern Lake Michigan;
September, 1977.
-------
BURNS I HARBOR
Appendix Figure 28. Turbidity contours, southern Lake Michigan; 11 June, 1977.
-------
87*20'
87°IO'
87°00'
Ul
BURNS I HARBOR
Appendix Figure 29. Turbidity contours, southern Lake Michigan; 20 August, 1977.
-------
BURNS V HARBOR
Appendix Figure 30. Turbidity contours, southern Lake Michigan; 24 September, 1977.
-------
87° 20'
87° IO1
87° OO1
41° 40'
BURNS I HARBOR
Appendix Figure 31. Fecal coliform contours, southern Lake Michigan, 11 June, 1977.
-------
87° 201
87«M 0'
87°OO!
co
BURNS I HARBOR
Appendix Figure 32. Fecal coliform contours, southern Lake Michigan, 20 August, 1977.
-------
VO
BURNS 1 HARBOR
Appendix Figure 33. Feoal coliform contours, southern Lake Michigan, 21 September, 1977.
-------
APPENDIX TABLE 1. Summary of phytoplankton species occurrence in the near-surface waters of southern
Lake Michigan during 1977 sampling season. Summary is based on all samples analyzed. Summary includes
the total 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.
# Average
CYANOPHYTA
Anabaena flos-aquae (Lyngb.) Breb.
Anabaena sp.
Anabaena spp.
A. subaylindriaa Borge
Anaaystis incerta (Lemm. ) Dr. and Daily
A. thermalis (Menegh.) Dr. and Daily
Daatyloaooaopsis rhaphidioides Hansg .
Gomphosphaeria aponina Kutz,
G, lacustris Chod.
Miorocoleus spp.
Oscillatoria bornetii Zukal
0. retzii Ag.
Osaillatoria sp.
Osaillatoria spp.
Sehizothrix sp.
Sehizothrix spp.
Total for division (16 spt.-ies)
CHLOROPHYTA
Ankistrodesmus falcatus (Corda) Ralfs
A. gelifactum (Chod.) Bourr.
Ankistrodesmus sp. #3
Ankistrodesmus sp. #6
Ankistrodesmus sp.
Ankistrodesmus spp.
Ankyra spp.
Chlamydomonae sp.
Chlamydomonas spp.
Coelastrum sp.
Cosmarium sp.
Cosmarium spp.
Cruaigenia irregularis Wille
C, quadrata Morren
C. rectangularis (A. Braun) Gay
C. tetrapedia (Kirch.) West and West
Dictyosphaerium ehr&nbergianum Naegeli
Elakatothrix gelatinosa Wille
slides
29
1
1
3
70
62
27
5
33
1
61
2
12
17
11
8
28
4
14
3
1
64
1
26
22
2
12
7
13
25
9
3
1
7
cells/ttl
24.458
0.372
0.419
0.605
1435.488
86.288
2.397
2.653
226.078
1.257
275.063
2.048
4.328
5.050
0.698
0.768
2067.968
1.862
0.186
0.652
0.140
0.047
9.401
0.047
107.930
64.903
0.559
0.419
0.209
3.002
11.380
2.234
0.559
1.443
0.396
7, pop
0.640
0.012
0.011
0.009
27.888
1.844
0.060
0.071
3.366
0.035
7.683
0.048
0.063
0.088
0.012
0.024
41.854
0.059
0.006
0.017
0.004
0.001
0.195
0.001
1.443
1.620
0.011
0.006
0.007
0.056
0.208
0.028
0.011
0.022
0.005
Maximum
cells/ml
335.103
33.510
37.699
33.510
5443.328
295.309
23.038
62.832
1748.819
113.097
1283.863
94.248
94.248
169.646
14.661
27.227
18.850
4.189
12.566
6.283
4.189
56.549
4.189
1212.654
772.831
33.510
6.283
4.189
69.115
167.551
35.605
33.510
129.852
12.566
% pop
7.045
1.047
1.030
0.391
"63.185
8.338
0.654
1.507
21.305
3.125
36.015
3.197
1.752
3.024
0.308
0.921
0.661
0.180
0.282
0.157
0.121
1.044
0.122
12.725
16.698
0.838
0.078
0.192
0.972
4.676
0.495
0.495
2.016
0.176
(continued).
60
-------
APPENDIX TABLE 1 (continued).
Franaeia droesaheri (Lemm.) G. M. Smith
Gloeoaystis planatoniaa (W. and W. ) Leram.
Golenkinia radiata (Chod.) Wille
Kirchneriella contorta (Schmidle) Bohlin
K. elongata G. M. Smith
K. lunaris (Kirch.) Moebius
Kivahneriella sp.
Kirchneriella spp.
K. subsolitaria G. *S. West
Lagerheimia ailiata (Lag.) Chod.
L. subsalsa Lemm.
Miaraatinium sp.
Mougeotia sp.
Mougeotia sp. #1
Mougeotia spp.
Nepkfoaytium agardhianum NSg.
M, obesum West and West
Nepkroaytium sp.
Nephrocytiwn spp.
Ooaystis pusilla Hansg.
Ooaystie sp.
Osaystis spp.
Pediastmm duplex Meyen
P. duplex var. alathratum (A. Braun) Lag.
P. obtueum Lucks
P. simplex var. duodenarium (Bailey) Raben.
P. tetras (Ehr.) Ralfs
Pedinamonas minutissima Skuja
Quadrigula sp.
Soenedesmus aauminatus (Lag.) Chod.
S. acutus f. costulatus (Chod.) Uherkov.
S. aautus Meyen
S. avauatus Lemm.
S. armatus var. boglariensis Hortob.
S. biaaudatus (Hansg.) Chod.
5. bijuga var. alternans (Relnsch) Hansg.
S. bijuga (Turp.) Lag.
5. brasiliensis Bohlin
S. carinatus (Leiran. ) Chod.
#
slides
7
86
2
4
23
1
4
19
1
12
2
1
12
1
5
7
1
2
2
1
1
61
3
1
1
1
7
2
1
26
4
4
3
2
1
1
9
2
2
Average
cells/ml
0.186
123.545
0.093
0.326
1.769
0.186
0.140
1.443
0.093
0.512
0.093
0.745
0.908
0.279
0.559
0.908
0.093
0.279
0.209
0.582
0.023
30.881
1.978
0.186
0.186
0.512
1.373
0.349
0.047
4.049
0.745
0.349
0.326
0.186
0.047
0.186
1.001
0.279
0.186
% pop
0.004
3.168
0.002
0.011
0.039
0.003
0.004
0.041
0.002
0.011
0.002
0.006
0.021
0.026
0.017
0.022
0.003
0.003
0.007
0.013
0.001
0.567
0.036
0.005
0.004
0.014
0.036
0.011
0.001
0.099
0.019
0.009
0.008
0.003
0.001
0.002
0.038
0.007
0.003
Maximum
cells/ml
4.189
513.126
6.283
18.850
23.038
16.755
6.283
20.944
8.378
8.378
6.283
67.021
10.472
25.133
18.850
23.038
8.378
16.755
12.566
52.360
2.094
263.894
92.153
16.755
16.755
46.077
33.510
27.227
4.189
41.888
16.755
8.378
12.566
8.378
4.189
16.755
41.888
16.755
8.378
% pop
0.088
8.687
0.156
0.542
0.539
0.312
0.181
0.663
0.220
0.208
0.188
0.555
0.327
2.299
0.587
0.635
0.294
0.176
0.446
1.174
0.055
3.002
1.686
0.463
0.378
1.283
0.790
0.851
0.130
0.932
0.719
0.251
0.330
0.130
0.099
0.176
1.204
0.455
0.202
(continued).
81
-------
APPENDIX TABLE 1 (continued).
SaenedeemuB diapav BrSb.
5. quadriaauda (Turp.) Brlb.
B, quadriaauda var. longiepina (Chod.) G.M.
SaenedeemuB sp.
SaenedeemuB apinosue Chod.
SaenedeemuB spp.
Sohroederia sp.
SelenastTwn sp.
Selenaetvwn spp.
Stauraetrum sp.
Tetraedrom aaudatum (Corda) Hansg.
7. minimum (A. Braun) Hansg.
r. regulars Kuetzing
Ulotkrix sp.
Undetermined green colony
Undetermined -green filament
Undetermined green filament #5
Undetermined green Individual
Total for Division (75 species)
BACILLARIOPHYTA
Aahnanthee alevei Grun.
A. lanaeolata (Brfib.) Grun.
A. minutissima (KUtz.)
A. veaurvatal
Aahnanthee sp.
AahnantheB spp.
Amphipleura pelluaida KUtz.
Amphora negleeta Stoerm. and Yang
A. ovalis var. pediaulue (KUtz.) V. H.
A. ovalis KUtz.
A. perpueilla Grun.
Amphora spp.
Amphora eubaostulata Stoerm. and Yang
Aeterionella formosa Hass.
Cooooneis plaaentula Ehr.
Coeaoneia sp. #2
ft
slides
1
54
Smith 18
1
12
73
1
2
2
2
4
30
1
2
3
1
9
77
9
2
3
6
7
2
27
1
1
3
24
1
2
81
1
1
Average
cells/ml
0.093
8.866
2.560
0.047
0.884
17.686
0.023
0.070
0.116
0.047
0.116
1.280
0.023
0.628
0.489
0.093
9.634
13.008
436.857
0.233
0.047
0.070
0.233
0.209
0.047
1.629
0.047
0.023
0.070
0.698
0.023
0.047
22.131
0.023
0.023
% pop
0.003
0.227
0.114
0.001
0.020
0.454
0.000
0.002
0.004
0.001
0.003
0.027
0.000
0.011
0.013
0.003
0.188
0.349
9.392
0.005
0.001
0.002
0.007
0.005
0.002
0.032
0.001
0.001
0.002
0.019
0.001
0.001
0.531
0.000
0.003
Maximum
cells/ml
8.378
58.643
25.133
4.189
8.378
92.153
2.094
4.189
8.378
2.094
4.189
14.661
2.094
37.699
23.038
8.378
259.705
90.059
4.189
2.094
2.094
10.472
4.189
2.094
16.755
4.189
2.094
2.094
4.189
2.094
2.094
182.212
2.094
2.094
% pop
0.235
1.802
2.978
0.060
0.234
2.730
0.017
0.121
0.278
0.033
0.100
0.326
0.041
0.589
0.662
0.231
6.263
3.640
0.098
0.041
0.071
0.289
0.118
0.095
0.350
0.117
0.075
0.087
0.248
0.052
0.060
3.413
0.022
0.248
(continued).
82
-------
APPENDIX TABLE 1 (continued).
#
slides
Cyalot&lla atomus Hust.
C. aomensis Grun.
C. oamensis auxospore
C. aomta auxospore
C. oomta (Ehr.) KUtz.
C. cryptica Reimann, Lewin, and Guillard
C, kutzingiana Thw.
C. meneghiniana K(ltz.
C. meneghiniana var. plana Fricke
C. michiganiana Skv.
C. oeellata Pant.
C. pseudostelligera Hust.
Cyalotella sp. #1
Cyalotella sp. #6
Cyclotella spp.
Cyalotella etelligera (Cl. and Grun.) V. H.
Cymatopleura elliptiaa (Breb. and Godey) Wm. Smith
C. eolea (Br6b. and Godey) Wm. Smith
Cymbella mieroaephala Grun.
C. prostrata var. auerswaldii (Rabh. ) Reim.
Cymbella sp. #12
Cymbella sp.
Cymbella spp.
Diatoma ehrenbergii KUtz.
D. hiemale var. mesodon (Ehr.) Grun.
Diatoma sp.
Diatoma spp.
Diatoma tenue Ag.
£>. tenue var. elongatwn Lyngb.
0. tenue var. paahyaephala Grun.
D. vulgare Bory
Diploneis oaulata (Breb.) Cl.
Entomoneis ornata (J. W. Bail.) Reim.
Fragilaria oapuoina Desm.
F. conetruens (Ehr.) Grun.
F. aonatruens var. binodis (Ehr.) Grun.
f. conetruene var. aapitata Herib.
F. construens var. minuta Temp, and Per.
10
90
24
15
61
49
9
17
31
25
50
44
1
45
58
90
1
7
6
4
2
2
2
7
1
1
1
10
29
38
1
5
2
4
1
1
1
13
Average
cells/ml
0.279
86.754
1.117
1.257
5.027
7.330
0.209
0.559
1.466
0.931
3.537
3.863
0.023
7.493
7.912
191.845
0.023
0.163
0.256
0.093
0.047
0.047
0.047
0.209
0.023
0.023
0.023
0.489
2.630
5.818
0.023
0.116
0.047
2.118
0.070
0.023
0.023
0.512
7. pop
0.007
1.930
0.024
0.030
0.096
0.186
0.007
0.018
0.048
0.025
0.072
0.121
0.001
0.189
0.225
5.172
0.000
0.004
0.008
0.003
0.002
0.000
0.002
0.007
0.001
0.000
0.001
0.013
0.086
0.208
0.001
0.004
0.002
0.060
0.002
0.001
0.001
0.014
Maximum
cells/ml
4.189
418.879
14.661
16.755
54.454
180.118
2.094
6.283
33.510
8.378
23.038
23.038
2.094
62.832
56.549
456.578
2.094
2.094
8.378
2.094
2.094
2.094
2.094
4.189
2.094
2.094
2.094
16.755
31.416
41.888
2.094
2.094
2.094
98.436
6.283
2.094
2.094
10.472
% pop
0.094
5.347
0.228
0.395
0.473
4.245
0.095
0.496
1.084
0.271
0.448
0.993
0.058
1.806
1.526
13.582
0.029
0.073
0.348
0.090
0.074
0.022
0.090
0.146
0.088
0.037
0.057
0.483
0.916
1.985
0.060
0.078
0.095
2.833
0.188
0.059
0.049
0.199
(continued).
83
-------
APPENDIX TABLE 1 (continued).
# Average
Fragilaria aonstruens var. venter (Ehr.) Grun.
F. arotonensis Kitton
F. intermedia Grun.
F. intermedia var. fallax (Grun.) A. Cl.
F. pinnata Ehr.
Fvagi tafia s p .
Fragilaria spp.
Fragilaria vaucheriae (KUtz.) Peters.
Gomphonema dichotonam Kutz.
Gamphonema sp.
Gomphonema spp.
Mastogloia spp.
Melosira granulata var. angustissima 0. Miill.
M. granulata (Ehr.) Ralfs
M. islandiaa 0. Miill.
M. italioa (Ehr.) Kiitz.
M. vafians Ag.
Naviaula angliea var. signata Hust.
N. angliea var. subsalsa (Grun.) Cl.
N. aapitata Ehr.
N. aapitata var. luneburgensis (Grun.) Patr.
N. aostulata Grun.
N. aryptoaephala var. veneta (Kiitz.) Rabh.
N. cryptoaephala Kiitz.
N. decussis 0str.
N. exiguiformis Hust.
N. gastriformis Hust.
N. luzonensis Hust.
N. menisculus var. obtusa Hust.
N. meni.ssu.lu8 var. upsaliensis Grun.
N. platystona var. pantoasekii Wislouchand
Kolbe
N. pupula KUtz
N. pupula var. mutata (Krasske) Hust.
N. radiosa var. tenella (Brgb.) Grun.
ff. radiosa Kutz
Naviaula sp. #19
Naviaula sp. #48
Naviaula sp. #78
slides
1
77
13
10
8
14
7
10
1
2
1
1
13
27
15
57
1
1
24
20
6
1
6
3
5
10
1
1
4
2
1
7
3
5
1
1
1
1
cells/ml
0.023
99.530
6.260
3.398
1.978
0.559
0.628
0.396
0.047
0.047
0.047
0.023
1.466
10.193
1.489
10.000
0.047
0.023
0.908
0.605
0.256
0.047
0.163
0.070
0.116
0.233
0.023
0.023
0.093
0.047
0.023
0.163
0.070
0.140
0.023
0.023
0.023
0.023
% pop
0.001
2.403
0.158
0.124
0.046
0.010
0.012
0.014
0.001
0.001
0.001
0.000
0.038
0.213
0.041
0.302
0.001
0.000
0.033
0.016
0.004
0.000
0.006
0.001
0.002
0.005
0.001
0.000
0.002
0.001
0.000
0.004
0.001
0.005
0.000
0.000
0.000
0.001
Maximum
cells/ml
2.094
397.935
92.153
100.531
75.398
8.378
25.133
6.283
4.189
2.094
4.189
2.094
23.038
167.551
27.227
56.549
4.189
2.094
10.472
4.189
6.283
4.189
4.189
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
2.094
4.189
2.094
2.094
2.094
2.094
% pop
0.065
8.955
2.564
3.493
2.260
0.131
0.343
0.285
0.060
0.035
0.099
0.035
0.662
2.500
0.750
1.985
0.088
0.026
0.496
0.151
0.118
0.045
0.151
0.049
0.073
0.068
0.058
0.045
0.052
0.049
0.041
0.075
0.060
0.176
0.043
0.022
0.020
0.049
(continued).
84
-------
APPENDIX TABLE 1 (continued).
# Average
Naviaula sp.
Naviaula spp.
Naviaula subhamulata Grun.
fl. tripunotata (0. F. Mull.) Bory
N. viridula (KUtz.) KUtz.
Neidium dubium fo. constrictum Hust.
N. dubium var. #1
Neidium sp.
Neidium sp. #3
Neidium spp.
Nitzeahia aaiaularis (KUtz.) Win. Smith
N. aauta Hantz.
N. amphibia Grun.
N. angustata var. aauta Grun.
N. baaata Hust.
N. aonfinis Hust.
N. dissipata (KUtz.) Grun.
N. fontiaola Grun.
If. frustulum (KUtz.) Grun.
N. graailis Hantz.
N. kutzingiana Hilse
N. linearis Wm. Smith
N. luzonensis Hust.
If. palea (KUtz.) Wm. Smith
N. paleaaea Grun.
N. reata Hantz.
N. romana Grun.
Nitzsahia sp. #1
Nitzsahia sp. #8
Nitzsahia sp. #9
Nitzsahia spiauloides Hust.
Nitzsahia spp.
Nitzsahia sublinearis Grun.
N. tryblionella Hantz.
Opephora sp.
Plagiotropis lepidoptera var. probosaidea
(Cl.) Reim.
Rhizosolenia eriensis H. L. Smith
R. graailis H. L. Smith
slides
6
50
1
2
1
1
1
2
3
3
76
12
1
1
39
60
16
75
9
5
36
11
1
75
3
17
1
18
1
13
9
75
2
2
1
1
57
48
cells/ml
0.140
2.397
01023
0.047
0.023
0.023
0.023
0.279
0.070
0.349
18.919
0.326
0.023
0.047
3.956
4.026
0.535
14.032
0.977
0.209
3.933
0.326
0.023
17.127
0.256
0.582
0.023
0.791
0.070
2.653
0.559
20.060
0.093
0.047
0.023
0.023
12.520
5.329
% pop
0.003
0.068
0.001
0.001
0.001
0.001
0.000
0.003
0.001
0.003
0.474
0.008
0.001
0.000
0.107
0.120
0.016
0.389
0.047
0.006
0.107
0.008
0.000
0.493
0.006
0.025
0.000
0.026
0.002
0.094
0.024
0.583
0.003
0.001
0.000
0.001
0.289
0.179
Maximum
cells/ml
2.094
43.982
2.094
2.094
2.094
2.094
2.094
16.755
2.094
16.755
85.870
4.189
2.094
4.189
46.077
18.850
8.378
54.454
27.227
4.189
43.982
4.189
2.094
104.720
14.661
8.378
2.094
14 . 661
6.283
64.926
16.755
113.097
6.283
2.094
2.094
2.094
81.681
46.077
% pop
0.050
1.528
0.068
0.033
0.052
0.068
0.045
0.210
0.068
0.139
1.898
0.130
0.049
0.044
1.374
0.746
0.248
2.358
1.241
0.131
1.148
0.130
0.026
3.639
0.348
0.993
0.022
0.423
0.142
2.256
0.542
4.049
0.264
0.068
0.035
0.049
1.859
1.707
(continued).
85
-------
APPENDIX TABLE 1 (continued).
t Average
Rhoieosphenia curvata (Kutz.) Grun.
Skeletonema potamos (Weber) Hasle
Skeletonema sp.
Skeletonema spp.
Stephanodisaus alpinus Hust.
S. bindevanus (Ktitz.) Krieger
S. hantzsahii Grun.
S. minutus Grun.
S. niagarae Ehr.
Stephanodisaus sp. #5
StephanodiscuB sp. #6
Stephanodisaus sp. #8
Stephanodiscus sp.
Stephanodisaus spp.
Stephanodisaus subtilis (Van, Goor) A. Cl.
S. tenuis Hust.
Surirella augusta Klitz.
S. biser-iata var. bifrons (Ehr.) Hust.
5. ovata Kutz.
S. ovata var. afriaana Hust.
Synedra deliaatissima var. angustissima Grun.
S. filiformis Grun.
S. minusaula Grun.
S. ostenfeldii (Krieger) A. Cl.
Synedra spp.
Synedra ulna var. ahaseana Thomas
Tabellaria fenestrata (Lyngb.) KUtz.
T. floeaulosa var. UneavLs Koppen
Undetermined centric diatom sp. #1
Undetermined centric diatom spp.
Total for Division (160 species)
CHRYSOPHYTA
Ckpysooosous dokidophorus Pasch •
Dinobfyon aysts
D. divergens Imhot
Dinobfyon sp.
Dinobruon spp.
slides
2
5
3
7
59
4
42
85
3
3
1
2
2
39
33
22
14
1
1
1
27
85
67
52
8
33
13
82
22
9
38
66
35
12
63
cells /ml
0.047
0.535
0.209
0.791
9.145
0.396
2.769
29.438
0.070
0.070
0.023
0.047
0.047
2.583
4.235
0.861
0.489
0.023
0.023
0.047
1.838
36.861
16.080
8.843
0.233
12.450
1.443
121.893
16.546
0.814
876.994
3.467
6.888
15.661
1.838
12 . 008
% pop
' 0.001
0.007
0.003
0.019
0.294
0.013
0.081
1.034
0.002
0.002
0.001
0.001
0.001
0.078
0.186
0.028
0.016
0.001
0.001
0.00-1
0.060
0.953
0.484
0.309
0.007
0.409
0.043
2.254
0.468
0.028
22.509
0.096
0.203
0.337
0.050
0.372
Maximum
cells/ml
2.094
31.416
12.566
35.605
69.115
18.850
20.944
154.985
2.094
2.094
2.094
2.094
2.094
33.510
94.248
10.472
8.378
2.094
2.094
4.189
14.661
297.404
94.248
50.265
4.189
75.398
41.888
927.816
314.159
14.661
23.038
48.171
217.817
35.605
136.136
% pop
0.035
0.335
0.131
0.853
1.989
0.614
1.387
9.926
0.073
0.065
0.049
0.087
0.060
1.047
6.716
0.746
0.262
0.066
0.073
0.133
0.528
9.368
2.749
2.219
0.228
3.327
1.206
10.886
8.322
0.796
0.719
1.500
3.665
0.964
3.382
(continued).
86
-------
APPENDIX TABLE 1 (continued).
# Average
Mallomonas pseudooorotia'Ui Presc.
Mallomonas sp.
Mallomonas spp.
Oshfomonas sp. #4
Ochpomonas sp.
Oahromonas spp.
Spinifefomonas sp.
Tr-ibonema spp.
Uroglenopsis spp.
Total for Division (14 species)
CRYPTOPHYTA
Chvoomonas spp.
Cryptomonas marssoni-i Skuja
(7. ovata Ehr.
Cvyptomonas sp.
Cryptomonas spp.
Rhodomonas minuta Skuja
fl. minuta var. nannoplanotiaa Skuja
Total for Division (7 species)
PYRROPHYTA
Cerat-ium hirundinella (0. F. Mull.) Shrank
Ceratium sp.
Glenodinium sp.
Glenodin-iwm spp.
Gyrrmodiniwn sp.
Gymnodini-wn sp.
Gyrnnodi.ni.um spp.
Peridinium sp.
Peridin-iwn spp.
Unidentified dinof lagellate sp.
Unidentified dinof lagellate spp.
Total for Division (11 species)
slides
29
3
3
31
1
89
1
1
1
89
22
90
1
60
90
34
7
5
2
2
10
1
3
22
42
22
7
cells/ml
1.559
0.209
0.163
15.778
0.023
147.793
0.023
0.186
0.698
206.297
68.602
1.280
28.647
0.023
5.282
150.656
8.540
263.031
0.186
0.116
0.070
0.047
0.465
0.023
0.163
1.094
5.608
1.745
0.419
9.937
% pop
0.040
0.006
0.003
0.378
0.001
3.561
0.001
0.008
0.029
5.084
1.672
0.025
0.678
0.000
0.131
3.408
0.266
6.180
0.004
0.003
0.002
0.001
0.009
0.001
0.004
0.023
0.200
0.037
0.013
0.298
Max imum
cells/ml
12.566
14.661
10.472
337.197
2.094
1145.633
2.094
16.755
62.832
196.873
18.850
98.436
2.094
23.038
846.135
83.776
4.189
2.094
4.189
2.094
12.566
2.094
6.283
18.850
41.888
23.038
8.378
% pop
0.569
0.427
0.151
10.502
0.060
27.187
0.073
0.697
2.641
4.578
0.624
2.766
0.026
0.760
16.515
3.442
0.086
0.061
0.143
0.061
0.245
0.061
0.181
0.495
2.635
0.573
0.228
(continued).
87
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APPENDIX TABLE 1 (continued).
Average
slides cells/ml % pop
Maximum
cells/ml 7. pop
EUGLENOPHYTA
Phacus sp.
Total for Division (1 species)
1 0.023 0.001
0.023 0.001
2.094 0.066
UNDETERMINED
Undetermined haptophyte sp. #1
Undetermined haptophyte sp. #2
Undetermined colony sp. #2
Undetermined flagellate spp.
Total for Division (4 species)
85
80
34
88
292.841
16.173
20.688
229.242
558.944
8.793
0.447
0.529
4,912
14.681
1866.105 56.974
106.814 3.380
134.041 4.597
772.831 13.503
88
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-905/3-79-001
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Phytoplankton Assemblages of the Nearshore Zone of
Southern Lake Michigan
5. REPORT DATE
March 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Eugene P. Stoerroer & Marc L. Tuchman
8. PERFORMING ORGANIZATION REPORT NO,
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Great Lakes Research Division
University of Michigan
Ann Arbor, Michigan ^8109
10. PROGRAM ELEMENT NO.
2 BA 6k5
11. CONTRACT/GRANT NO.
Grant - R005337-01
12. SPONSORING AGENCY NAME AND ADDRESS
Great Lakes Surveillance £ Research Staff
Great Lakes National Program Office
U.S. Environmental Protection Agency
Chicago, Illinois 60605
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA - GLNPO
Great Lakes National Program
Office
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Phytoplankton samples from nearshore stations along the Indiana coast of Lake
Michigan were analyzed to determine the composition and seasonal abundance of
Phytoplankton populations. Occurrence patterns of major populations and popu-
lation groups were inspected. As might be expected in a local inshore region
where physical mixing and advection processes are relatively intense, phyto-
plankton distribution is highly variable. The largest general effect noted is a
continuing increase in groups other than diatoms, apparently as a result of silica
depletion. The singular exception to this trend is the abundant occurrence of
Cyclotella comensis, a diatom which has only recently become abundant fn Lake
Michigan and can apparently tolerate very low silica levels. Specific to the
region is an atypically high abundance of members of the diatom genus N^tzschjj
during some sampling periods. High abundance of these organisms appears to be
associated with organic nitrogen and ammonfa inputs. Occasional occurrences of
populations such as Thai assiosi ra sp. and Skeletonema spp. were noted and may
be indicative of local areas of high conservative ion input. Another character-
istic of the phytoplankton assemblages in the Indiana nearshore region is the
high abundance of microflagellates, especially organisms which apparently belonging
to the ffaptophyceae or Prasinophyceae,
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
phytoplankton populations
water quality, microflagellates, monitor-
ing, nitrogen, phosphorus, silica
Southern Lake Michigan
Indiana Nearshore
8. DISTRIBUTION STATEMENT
Available through
Springfield, VA 22161
19. SECURITY CLASS (ThisReport)
Unclass ified
21. NO. OF PACES
20. SECURITY CLASS (ThispageJ
Unclass ified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
89
U S GOVERNMENT PRINTING OFFICE 826-681
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