PB83-261735
Phytoplankton Composition and
Distribution in Saginaw Bay
Michigan Univ., Ann Arbor
Prepared for
Environmental Research Lab.-Duluth, MN
Sep 83
U.S. Department of Commerce
Ptsttmal Technical Information Service
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FiP.A-bnO/S-SS-O'.H)
September 1983
PHYTOPLANKTON COMPOSITION AND DISTRIBUTION
IN SAGINAW BAY
by
E. F. Stoerner
and
E. Theriot
Great Lakes Research T i ion
University of V i ^ *
Ann Arbor, Michi »>-
Grant No. R807450-U3
Project Officer
Dr. Wayland Swain
Great Lakes Research Station
Grosse Tie, MI
Environmental Research Lab - Duluth
USEPA
Duluth, MN
1983
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment ->r recommendation for use.
ii
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TECHNICAL REPORT DATA
trifcse redd InMrucuont on the reirnc bejort compl-'ringj
1 H r •' (J ^ T N 2
11 ,\-<>'Mi
3 RECIPIEN r 5 ACCESSION NO.
.J-.i -At-/
4 title and Subtitle
t'l:. top 1 ankton Cc.T.jio-i i t ion and i' ist r ibut ion in Saginaw
"¦<. IV
5 REPOR r DATE
Sept enber
6 PERFORMING ORGANIZATION COOE
j AuTxonir.i
K.'r'. Stot-rrv.er and K. iheri>t
S. PERFORMING ORGANIZATION REPORT NO
¦3 PERFORMING ORGANIZATION NAMfc AND ADDRESS
(',(/•¦ it. Lakes IKsoai cli Uivision
l':i ivi rsilv o! M ii/ii ir.an
Ann ArS or, Michigan
10. PROGRAM ELEMENT NO.
11 CONTRACT GRANT NO.
80 7 ; 30
'2 SPONSORING AGENCY" NAME ANC AOORESS
Eiivi ronmental Research Laboratory
Office of Research and Development
U.S. F.nvi ronmental Protection Aqencv
Duluth, Mfl 55804
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
1 l'A/(»oi)/().S
15 SUPPLEMENTARY NOTES
'6 ABSTRACT
This suirijriztfs studies conducted during 1980 to assess the effects of reductions in
phosphorus loading to Saginaw Bay on phytop 1inkton in the bay and the adjacent waters
of Lake Huron. Quantitative estimates of phytop 1ankton .ibur.dance were developed tron
in array of sc it ions sampled during the ic^-free season. Distribution and abundance of
-u j o r speci'-s and multivariate statistical representations of '. s mc •' at ions were
cor.pired to ;inilar data collected durin.; L97;», prior to phosphorus loading reductions.
Results show a substantial reduction in the abundance and rani»e of distribution of
•."it rophicat ion tolerant ind potentially nuisance-producinvj ph> top lankton populations in
Saginaw Bay and reduced export of such populations to the main Lake Huron system.
17. KEY WORDS AND DOCUMENT ANALYSIS
J DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TEHMS
c. COSATl Field/Croup
'
IB DISTRIBUTION STATEMENT
RF.l.r.ASK TO IM'M.IC
19 SECURITY CLASS {This Rtportj
rNCI.ASSI.FlKn
21 NO. OF PAGES
JIM
20 SECURITY CLASS (ThUpagrl
l.'NCI.ASS 1 K 11.1)
22. PRICE
EPA For** 2220-1 (R»». 4-77) "Hvioui eivon h OBtoit't
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ABSTRACT
Phytoplankton abundance and species composition in Saginaw Bay in 1980
was highly variable by area. Assemblages sampled ranged from oligotrophic
associations similar to those found in the open waters of Lake Huron to those
characteristic of the most disturbed regions of the Great Lakes system.
Three major regions of influence of the phytoplankton flora are identifiable
under average conditions. A number of stations in the southern part of the
bay are strongly influenced by loadings from the Saginaw River and maintain
high numbers < species characteristic, of eutrophic environments. Stations in
Wild Fowl Bay and near Oak Point have a different algal association
characterized by very high numbers of blue-green algae. It appears that this
region is affected by local loadings. Other stations in the bay are more
flotistically similar, with a transit!<>n from more eutrophic associations in
the south to oligotrophic associations nea- the mouth of the bay.
When compared to a similar study conducted during 1974-1976, these re-
sults show a substantial improvement of water quality in Saginaw Bay attribut-
able to nutrient loading reductions. The abundance and distribution of blue-
green algal populations associated with nuisance conditions ha bpen restrict-
ed. Similarly, several species of diatoms associated with extreme water qual-
ity degradation in the Great Lakes have decreased to very minor constituents
of the flora, where they were previously important. The average cell size of
phytoplankton populations in the bay has been signlticantly reduced.
iii
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The reduction in range of distribution of eutrophication tolerant
populations has led to less transport of eutrophication tolerant populations
from the bay into the open waters of Lake Huron than was the case in 1974-
197b. Under 1980 conditions regions of phytoplankton similarity in the bay
are clearly related to average current patterns and loading sources. This was
not the case in 197/» —1976- We interpret this to mean that the phytoplankton
component of the Saginaw Bay ecosystem has returned to a raor. typical function
as a result of reduction of grossly excessive phosphorus loadings.
iv
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; >NTK\TS
I'age
Abstract iii
Figures v i
Tib Us
In I rod uc t i on - 1
'ibj'-ctivi'S ?
MaterinLs and Methods 3
Results b
Bay-Widn Summary 5
Sf? nme n t An a i y s i s 7
T!vj Phytoplankton Flora of Saginaw TViy 16
Total Phytoplank^on In
Cyaiophyt a 19
Bac i 1 1 ar i opnyt :i 54
f.hlorophyt a 93
Cryptophyta 114
Chrvsophyta 121
Undot»Tni ru».1 F1 ?»>',<.• 11 nt**s 12H
1'yrmphyta 135
Ku<;enophy t a 135
Community Analysis 135
Average Bay-wide Community Analysis 140
Community Analysis by Cruise 149
Discussion and Conclusions 168
Re commend at i ons 181
R-» f ¦' rences 182
Appendix I - Summary of Phytopl ankton Occurrence 18 6
v
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FIGURrS
Number Page
1. Station locations in Saginaw Bay for this study.
Segments 1-5 were previously defined by Bratzel e_t al.
( 1 977) 4
2. Seasonal variation of total cell abundance in Saginaw Bay 8
3. Seasonal variation of abundance of the three dominant algal
divisions in Saginaw Bay 9
4. Seasonal abundance of the three subdominant algal divisions
in Saginaw Bay 10
5. Seasonal abundance of ninor algal divisions in Saginaw Bay.... 11
Seasonal variation in total phytoplankton abundance by segment
in Saginaw Bay 15
7. Distribution of total phyto-1 aul-ton 17
8. Distribution of blue-green algae 2C
9. Distribution of blue-green filament if2 22
10. Distribution of blue-green fila-nent. ^!4 25
11. Distribution of Anabaena flos-aquae 27
12. Distribution of Anacystis cyanea 29
13. Distribution of Anacystis incerta 32
14. Distribution of Aphanizomenon gracile 34
15. Distribution of Gomphosphaeria lacustris 37
lf>. Distribution of Microcoleus vaginatus 40
17. Distribution of Osci 11 atoria limnerica 43
vi
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18. Distribution of Oscillatoria retzii.. 45
19. Distribution of Pelonema sp 47
20. Distribution of Porphyrosiphon sp 50
21. Distribution of Schizothrix calcicola 52
22. Di str i u.c ion of diatoms 55
2'). Distribution of Cyclotel la eomensis 57
24. Distribution of Cycl otel la omta f»0
2 5. Distribution of Cyclotella meneghiniana 62
26. Distribution of Cyclotel 1 a ooel lata - 64
2 7. Distribution of Cyclotel la pseudostelligera 67
28. Distribution of Fragi laria capucina 69
29. Distribution of Fragilaria crotonensis 71
3'J. Distribution of Melosira distans var. alpigena 74
31. Distribution of Melosira granulata 76
32. Distribution of Melosira islandica 79
33. Distribution cf Stephanodiscus binderanus 81
34. Distribution of Stephanodiscus hantzschii 84
3 5. Distribution of Stephanodiscus subtilis 86
36. Distribution of Stephanodiscus tenuis 89
37. Distribution of Synedra fi 1 iformis 91
38. Distribution of Thalassiosira spp 94
39. Distribution of green algae 96
40. Distribution of Chodatella quadrlseta 98
41. Distribution of Coelasr.rum microporum 101
42. Distribution of Gloeotila pelagica 103
43. Distribution of Mougeotia sp 105
vii
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44. Distribution of Pediastrum boryrnum - •• 108
45- Distribution of Scenedesrous acutiformis. .... IK)
46. Distribution of Scenedestnus decorus var.
bicaudato-granulatus i 1 2
47. Distribution of Scenedesmus spinosus 115
48. Distribution of cryptomonads 117
49. Distribution of Chroomonas spp 119
50. Distribution of Cryptomonas ovata 122
51. Distribution of Rhodomonas minora 124
52. Distribution of chrysophytes 126
53. Distribution of Ochromonas spp 129
54. Distribution of undetermined flagellates 131
55. Distribution of flagellate species "13 133
56. Distribution of dinoflagellates 136
57. Distribution of euglenophytes 138
58. Rsgions of Saginaw Eny based on average phytoplankton
assemblage associations 143
59. Cluster analysis of average Bay phytoplankton communities 144
60. Principal components analysis of -werage Bay phyto-
plankton conmunit Ins. Scores on PCI and PCII 145
61. Principal components analysis of average Bay phyto-
plankton communities. Scores on PCI and PCTI 146
62. Regions of Saginaw Bay during cruise 83 150
63. Regions of Saginaw Bay during cruise 84 152
64. Regions of Saginaw Bay during cruise 36 154
b5. Regions of Saginaw Bay during cruise 87 155
66. Regions of Saginaw Bay during cruise 88 157
67. Regions of Saginaw Bay during cruise 90 158
vi ii
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63. Regions of Saginaw Bay during cruise 91 160
69. Regions of Saginaw Bay during cruise 92 162
70. Regions of Saginaw Hay during cruise? 93 164
71. Regions of Saginaw Bay during cruise 94 166
72. Regions of Saginaw Bay during cruise 95 167
ix
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TABLES
Number Page
1. Cruise dates for 1980 sampling se.ison on Saginaw Bay 6
2. Summary of Saginaw Bay phytoplunkton densities by mnior
taxonomic group 6
3. Average absolute abundance (cells/ml) of algal divisions
by segment 13
4. Results of Kruskal-Wnllis test for comparisons of
adjacent .gments 14
5. Results of principal components analysis for average bay-wide
community association study 141
x
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INTRODUCTION
Saginaw Bay is located on the western side of Lake Huron, extending in a
southwesterly direction from the Lake into the lower peninsula of Michigan.
Several islands dot the Bay, ir^luding the Charity Islands in the center of
the Bay and several islai.ds along the eastern shore.
Although there is much spatial and seasonal variability in apparent water
quality, it is apparent that Saginaw Bay is one of the most culturally
impacted areas of t'ae upper Great Lakes. The historical context .>f present
problems in Saginaw Bay has been reviewed by freedman (1974). Vo 11 piiwpider
et al. (1974) emphasLze that certain regions of Saginaw Lay had the highest
phytoplankton standing crop and highest rates of productivity found wichi' the
Great Lakes system. While such estimates of water quality reflects the high
nutrient loading of the Bay, the qualitative composition of the phytoplankton
assemblage (Stoermer et^ jU. , in press) also reflects the high conservative
element loading? reported by Beeton j^t (1967).
Saginaw Bay is an important source of nutrients and phytoplankton biomass
to Lake Huron. The data of Schelske et al. ( 1 974) indic.n-e that most of the
nutrients discharged into Saginaw Bay are already sequestered by the
phytoplankton by the time they reach Lake Huron. ' .:oermer and Kreis (1980)
showed that certain populations derived from Saginaw Bay can survive and be
dispersed into Lake Hut on.
1
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This study Is part of a general investigation of Saginaw Bay and southern
Lake Huron. Included in this general investigation are studies of chemical
conditions in Saginaw Bay (Smith et al. 1977), chemical conditions and
productivity in southern Lake Huron (Schelske et a\_. 1977), crustacean
zooplankton standing crop (McNaught ejt _al. 1980), rotifer standing crop and
distribution (Stemberger et^ al^ 1979), a general model synthesis of conditions
and processes in Saginaw Bay (Bierman and Dolan 1981), and phytoplankton
composition and abundance in Lake Huron (Stoermer and Kreis 1980).
The studies cited above deal primarily with conditions in Saginaw Bay and
southern Lake Huron prior to extensive nutrient loading reductions to Saginaw
Bay accomplished in the late 1970's. This study attempts to measure the
qualitative and quantitative response of phytoplankton populations in the bay
to reduced nutrient loadings. By using the phytoplankton as an integrated
measure of loading effects we hope to be able to detect both the positive
effects of nutrient loading reductions and the possible presence of remaining
problems in either the general ecology of the bay or local regions within the
bay which may require further remedial action. This latter aspect is
particularly important in the case of Saginaw Bay, since prior investigations
indicate that prior to nutrient loading reductions, substantial portions of
the bay were nutrient saturated (Vollenweider et a_l. 1974) or ovar saturated,
resulting in transport of nutrients and algal populations adapted to eutrophic
conditions to Lake Huron (Stoermer et al. 1980, Stoermer and Kreis 1980).
2
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OBJECTIVES
1. A quantitative assessment of phytoplankton standing stock and
composition in Saginaw Bay.
2. Analysis of seasonal and SDatlal trends of variation in phytoplankton
assemblages of Saginaw Bay.
3. Provision of quantitative data for verification of a multi-class
phytoplankton model of phytoplankton dynamics in the bay (Bierman and
Dolan 1981).
The results pertaining to the first two objectives are reported here.
Data generated in support of the third objective will be reported elsewhere
(Bierman e£ al^. in prep.).
MATERIAL AND METHODS
The basic station array is shown in Figure 1. Stations were selected to
provide approximately equal areal coverage of the Bay, except that some bias
was given to the region near the mouth of the Saginaw River in terms of
station density. Phytoplankton were collected from I m depths at »»ach station
and, where possible, from 10 m depths. Only 1 m samples were analyzed for
this report. Due to occasional bad weather conditions, there were deviations
from the planned sampling schedule on some cruises and some stations were not
sampled. Such omissions are noted In the discussion of the appropriate data
3
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AST TAWAS
47
49
48
50
45
5i 53
42
43
36
37
44
35
38
60
29
32
34
28
27
26
56
54
BAY CITY
Figure 1. Station locations in Saginaw Bay for this study.
Segments 1-5 were previously defined by Bratzel rt jjK (1977).
4
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analyses. Eleven cruises were made from April 1980 through November 1980
(Table 1).
Samples at all stations were taken as splits from a single 8 liter Niskin
bottle cast. Immediately after collection, approximately 100 mis of sample
were fixed with 2 mis of 50°' electron microscope grade gluteral dehyde and
placed on ice for transportation to the laboratory for further process i.
Depending on the density of suspended material in the sample, between 5 and
50 mis was withdrawn after gentle agitation to resuspend the phytoplankton.
The suspension was concentrated by filtration onto 25 mm "AA" Millipore
filters, which was then partially dehydrated ough an ethanol series,
embedded in clove oil on 50 x 75 run glass slides, covered with a 43 x 50 mm "1
thickness cover slip and allowed to clear for approximately two weeks. The
finished mounts were examined on a Leitz Ortholux microscope fitted with
bright field optics at a magnification of approximately I200x. Populations
estimates are given for the averaged counts of two transects of 10 mm
corrected for the volume filtered and the area of the filter pad examined.
RESULTS
BAY-WIDE SUMMARY
The overall abundance of phytoplankton at all stations in all cruises
sampled during the study is shown in Table 2. Total average cell abundance is
high but there is a wide variation in the distribution of cell counts among
taxonomic groups. Blue-greens, diatoms and greens were the dominant taxa.
Cryptomonads, chrysophytes and undetermined flagellates wore present at all
stations but comprised a smaller portion of the average total assemblage.
5
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TABLE 1. CRUISE DATES FOR 1980 SAMPLING SE/vSON ON SAGINAW BAY
Cruise No. Dates
83
14-18 April
84
5- 9 May
86
26-30 May
87
16-20 June
88
7-11 July
90
28 July - 1 August
91
18-22 August
92
3-12 September
93
29 September - 3 October
94
20-24 October
95
10-14 November
TABLE 2. SUMMARY OF SAGINAW BAY PHYTOPLANKTON DENSITIES
BY MAJOR TAXONOMIC GROUP
Average Relative Abundance
Taxon cells/mL of Assemblage CO
Blue-greens
6,652.4
4 2.7
Diatoms
3,843.9
25. 1
Greens
3,698.2
24.1
Cryptomonads
469.2
3. 1
Chrysophytes
340.9
2.2
Undetemined flagellates
310.9
2.0
Dinoflagellates
14.8
0. 1
Euglenophytes
0.4
<0.1
To t a 1
15,330.7
6
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Dinof 1 agel lates and euglenoids were a minor port'on of the total assemblage,
never occurring in abundance.
Seasonal abundance of the total phytoplankton is shown in Figure 2.
There was a steady increase in abundance from the first sampling period in
April through the September sampling. Abundance declined through October and
November. In April, diatoms are the dominant group, but green algae become
the most abundance division by June (Figure 3). Thereafter, until the period
following the late summer maximum, blue-green algae dominate the assemblage.
In late fall diatoms reach their maximum abundance and are again the dominant
group (Figure 3). Only in late fall and early spring are chrysophytes,
cryptononads and undetermined flagellates relatively abundant (Figure A).
In terms of absolute abundance, each of these three groups have an early
spring maximum and a second maximum near the total phytoplankton maximum.
Dinoflagellates exhibit both a spring and late summer pulse, and are a
persistent but minor component of the assemblage through all seasons.
Euglanophytes occur only sporadically (Figure 5).
SEGMENT ANALYSIS
Analysis of phytoplankton abundance by Bay segments designated by Bratzel
et al. (1977) gives some insight into processes controlling phytoplankton
abundance and distribution in Saginaw Bay (see Figure 1). Bratzel et^ al.
(1977) based this segmentation scheme in part on average current patterns in
the Bay. Waters of Lake Huron usually enter from the northwest corner of the
Bay, travel down the western shore and receive significant nutrient input at
the Saginaw River, move up the eastern shore and exit into Lake Huron at the
northeastern corner of Saginaw Bay. In general, total phytoplankton
7
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3 5 n
30
o
o
25
E20
_C0
© 1 5 ¦
o
1 0J
APR MAY JUN JUL AUG SEP OCT
Figure 2. Seasonal variation of total cell abundance in Saginaw Bay.
NOV
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20-|
15-
p»
o
10-
Q)
O
/ blue gie .is \
greens
*
/
\
_V
diatoms
APR
MAY
J UN
JUL
AUG
SEP
OCT
'NOV
Figure 3. Seasonal variation of abundance of the three dominant algal
divisions in Saginaw Bay.
9
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1000
cryptomo nads
800
-j
600-
400-
\ >
chrysophytes
APR
MAY
AUG
JUL
JUN
OCT
NOV
SEP
Figure 4. Seasonal abundance of the three subdorainant algal divisions In
Saginaw Bay.
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2 0
d inof lageliates.
j 15
10-
euglenophytes
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
Figure 5. Seasonal abundance of minor algal divisions in Saginaw lay.
IM
mmmmmmm
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abundances by segment support the hypothesis. Cell densities increase from
segment 4 to segment 2 to segment 1, reach a maximum at segment 3, and then
decrease at segment 5 (Table 3).
Differences in cell densities for stations in each of the segment pairs,
in the order given, are statistically significant except for the pair of
segr. "its 1 snd 3 (Table A). Stations in segment 3 have significantly higher
cell densicies than stations in segment 2. The difference between segments 4
and 5 is not statistically significant, even though the abundance average of
segment 4 is approximately twice that of 5. This indicates that segment 5 is
heterogenous group of stations with varying levels and sources of control ">f
phytoplankton abundance. This contention will be more fully explored in the
section entitled "Community Analysis."
The absolute abundancr of the major divisions of algae by segment over all
cruises is shown in Table 3. Blue-green algae are dominant in segments 1, 3,
and 5 and diatoms are dominant in segments 2 and 4. Chrysophytes, cryptomonads
and undetermined flagellates tend to be most abundant ir. the three inner bay
segments but reach their highest rela. e abundance at segment 4 (Table 3).
Dinoflagellates and euglenophytes were mi ir components of the assemblage
at all segments except that euglenophytes wei-_ entirely absent from segment 5.
All segments reached peak abundant of total -hytoplankton in late August
to early September (Figure b). Abundance levels inc.r sed more or less
gradually to summer maxima in all segments. Abundance le^rls in segments 2
and 5 were less stable than the other three segments during • -e summer bloom
(Figure 6), indicating that ' rtant local effects on phytoplankton popula-
tions of these areas may not be qulcKly integrated with the rest of t • bay.
12
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TABLE 3. AVERAGE ABSOLUTE ABUNDANCE (CELLS/ML) OF ALGAL DIVISIONS BY SEGMENT
Abbreviations: N, total number of samples per segment; TP, Total Ptiytoplankton; BG, Blue-Green;
GR, Green algae; DI, Diatoms; CH, Chrysophytes; CR, Cryptomonads; UNDET., Undetermined flagellates;
DN, Dinof1agellates; EU, Euglenophytes
Segment N TP BG GR DI CH CR UNDET DN EU
1 48 24,355 8,754 8,270 5,707 423 724 457 19 1.5
2 90 11,023 2,688 2,670 4,467 348 611 227 12 0.1
3 30 45,888 30,401 8,978 5,057 423 475 526 28 0.6
4 64 4,359 1,058 534 2,021 265 208 262 11 0.0
5 37 8.304 4.990 1.462 2.080 283 241 235 14
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TABLE 4. RESULTS OF KRUSKAL-WALLIS T'.iST
FOR COMPARISONS OF ADJACENT SEGMENTS
Significance 'evels = *p<0.05; **p<0.01; ***p<0.001. N.S. = not significant
Kruskal-Wallis
Segment Pairs Statistic
24.269''**
1.866 NS.
20.060***
42. 347*:' *
28.987***
1.611 N.S.
1-2
1-3
2-3
2-4
3-5
4-5
14
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180
170-
80-
70-
60-
50-
CO 40"
30-
20-
10-
1
r
APR'
KAY
JUN
AUG
UL
SEP
OC T
NOV
Figure 6. Seasonal variation in total phytoplankton abundance by segment
in Saginaw Bay.
15
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THF PHYTOPLANKTON FLORA OF SAGINAW BAY
A summary compilation of the taxa occurring in samples taken during this
study are given in Appendix 1. In many cases, taxa were encountered which
could not be identified with known species. In some cases, this was due to
the lack of critical life cycle stages or structures necessary for identifi-
cation. In other cases, it was probably due to the availability of only a
limited number of specimens atypical of known species. Lastly, there were
undoubtedly specimens which belong to undescribed taxa. Specimens were
identified to the lowest possible raxonomic level, usually the species level,
but occasionally only generic affinity could be confidently determined.
If generic determination could not be made, then specimens were placed in the
appropriate division under some descriptive term, e.g. undetermined blue-green
filament.
In the rest of this section, seasonal and spatial trends of represen-
tative taxa of each of the major taxonomic groups are illustrated and dis-
cussed. Not only taxa with seasonal and spatial trends corresponding with
general trends, but ^Iso taxa with distributions exceptional to general
trends, were selected for study.
Total Phytoplankton (Figure 7)
Total abundance is uniform in all areas of the Bay from April through
May. Populations b"gin to increase in the inner Bay by June, but cell
densities in the outer Bay remain low. In July, cell densities begin to
increr.se in the outer Bay, but mainly only in nearshore areas between Wild
Fowl Bay and Port Austin. From late July through August, abundances increase
steadily in all areas with maximum densities occurring at inner Bay stations
16
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150000
cm
150300
16-20 JUN 80
cm
150000
7-U JUL
cm
DOT II
I5G000
cm
IS0000
26-30 MAT 80
CRT
150000
Figure 7. Distribution of total phytoplankton.
17
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ERST II
1SOOOO
13-22 RUG 80
ISOOOO T
150000
8-12 SEP
ISOOOO
10-14 NOV 80
ISOOOO
Figure 7. (continued).
18
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near the mouth of the Saginaw River and along the eastern shore between the
Quaniccassee River and Wild Fowl Bay. Total abundance levels then stabilize
through early October. Exceptions occur at Wild Fowl Bay and at Oak Point,
where significant blooms occur in September. Cell densities decline at all
stations from late September-early October through November.
Cyanophyta or Blue-green algae (Figure 8)
Most species of this division are associated with eutrophic to highly
eutrophic waters. Many, if not all, species are capable of nitrogen fixation
and so are at an advantage when other algae are nitrogen limited. This
situation occurs in many eutrophic lakes in mid- to late-summer following
diatom and green algae blooms. During this period blue-greens typically reach
their greatest abundance. In Saginaw Bay, blue-green abundance steadily
increased from late May through September. Highest levels were reached in the
eastern half of the inner Bay, especially at Wild Fowl Bay in September.
Blue-green algae are largely absent from the outer Bay, except for nearshore
stations such ts Oak Point (Station 44, Figure 1). Significant populations
develop here and in the shallow waters surrou'iding Charity Island in July,
August, and September.
Blue-green filament "3 (Figure 9)
Taxonomic affinities of this taxon and blue-green filament "4 are un-
certain but they both may be conspeolfic with Aphanizomenon gracile. The
areal distribution of blue-green filament '.'3 is highly restricted in Saginaw
Bay. It occurs in nearshore areas of the inner Bay and reaches its maximum
abundance in Wild Fowl Bay in August and September.
19
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150000
isoaoc
isoooo
150000
1SOOCO
Figure 8. Distribution of blue-green algae
-------
DOT II
1S000C T
18-22 flue 80
"TV
15C0CC t
0-12 SEP 80
150000
29 SEP - 3 OCT
nwr ti
150003
20-2U OCT 80
IS0000
10-14 NOV 80
Am —
Figure 8. (continued).
21
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cm • »«V'
25000
16-20 JUN 00
W-18 APR 80
OBI II
2SOOO
5-9 MAY 00
it cm
25000
7-11 JUL 80
cm
25000
26-30 MAT 80
25000
28 JUL - I RUC 80
Figure 9. Distribution of blue-green filament I'3.
22
-------
25000
18-22 AUG 80
25000
am cm
OUT
25000
8-12 5EP 80
CITT
10-U NOV
It CUT
29 SEP - 3 OCT 80
cm
Figure 9. (continued).
23
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Slue-green filament '!4 (Figure 10)
This taxon is sonwhat more widely distributed than blue-green filament
»'3, but shares its strong association with nearshore areas. Like blue-green
filament 3 and several other blue-green filamentous species, it first occurs
in significant numbers in August. Its maximum abundance occurs in September
when a large pulse occurs at Wild Fowl Bay, and moderate levels also develop
at Oak Point. During August and September, it is also abundant at stations
near the Quaniccassee River. Numbers decline in all areas from late September
through November.
Anabaena flos-aquae (Figure 11)
This species is a common minor component of phytoplankton assemblages of
offshore waters in the Great Lakes, but reaches its highest abundances in
eutrophie areas (Stoermer 1978). It is a heterocyst-forming blue-green and so
is capable of significant nitrogen fixation even in the presence of oxygen.
Its distribution in Saginaw Bay is somewhat atypical of other blue-green algae
in that moderate populations develop in May and that moderate to high cell
densities occurred in middle and outer Bay waters. High populations first
develop nearshore , but by June high cell densities are found at offshore mid-
Bay stations. It was then generally absent in early July, but reoccurred in
late July when maximal population levels developed along the western shore.
Anacystis cyanea (Figure 12)
This species is common, and occasionally forms nuisance blooms, in small
eutrophie lakes. It is rare in the Great Lakes except in highly eutrophie
24
-------
25000
16-20 JUN 80
25000
IU-18 RPR 80
cm
25000
7-11 JUL 80
25000
5-9 MRY 80
28 ju;
1 BUG 80
25000
26-30 MRT 80
Figure 10. Distribution of blue-green filament #4.
25
-------
25000
20-21 OCT 80
IT CUT
25000
18-22
¦n cm
8-12 5EP 80
25000
10-14 NOV 80
CI"
25000
29 SEP - 3 OCT 80
» Cltl
Figure 10. (continued).
26
-------
Figure 11. Distribution of Anabae. flos-aquae
-------
Figure 11. (continued)
-------
OBI II
60CO
16-20 JUN 80
cm
6000
CJTT
6000
cm
6000
7-1! JUL 80
6000
26-30 MAT 80
cm
6000
Figure 12. Distribution of Anecystls cyanea.
29
-------
6000
18-22 BUG 80
v cm
6000
8-12 SfP 80
it cm
6000 T
29 SEP - 3 OCT 80
cm
Figure
6000
20-2H OCT 80
cm
6000
10-1U NOV 80
it cm
12. (continued).
30
-------
areas. 1l reaches its maximum abundance in Saginaw Bay at stations near the
river and along the eastern shore all the way to the mouth of the Bay.
Its maximum distribution occurs in August and September when it is present in
abundance at nearly all stations in the middle and inner Bay.
Anacystis incerta (Figure 13)
Unlike cyanea, this species is not particularly uncommon in the
offshore waters of the Great Lakes, although it is generally most abundant in
areas which have been significantly disturbed. In Lake Huron it ocurs well
into the fall rd teaches its maximum in October Later than most blue-green
species (Krein ^na Scoermer 1980). A similar pattern of seasonal occurrence
has been noted in Like Ontario (Stoermer et al. 1974). In Saginaw Bay, this
species shows a clear preference for the eastern half of the Bay from July
through September, reaching its maximum abundance in that region in August and
Septemoer. However, moderate populations occur at the Bay-Lake Huron
interface in September and Octobei. Although abundance levels across the Bay
decline somewhat after early October, significant cell densities persist
through November.
Aphanizomenon graclle (Figure 14)
This species is a common important contributor to nuisr.nce algal blooms
in some eutrophic lakes. In Saginaw Bay its distribution is limited to Wild
Fowl Bay and other nearshore eastern inner Bay stations. The first
significant occurrence is in Wild Fowl Bay in late July. Large populations
develop quickly at nearshore stations from Oak Point to the Quaniccassee River
and low to moderate densities persist through November at these locations.
31
-------
15000
IU-18 APR 80
cm
15000
16-20 JUN 80
it cut
15000
5-9 MAT 80
it cm
15000
II CITT
DOT Tl
15000
26-30 MPT 80
It cut
15000
28 JUL - I BUG 80
Figure 13. Distribution of Anacystls incerta.
32
-------
•»-
20-21 OCT 80
it cur
15000 T
CITT
15000
8-12 SEP dO
it cm
isoao
10-W NOV 80
cm
DOT Tl
15000
29 SEP - 3 OCT 80
cm
Figure 13. (continued).
3?
-------
20000
11-1B RPR 80
cin
DOT Tl
20000
16-20 JUN BO
cm
OBI Tl
20000 T
5-9 MRT 80
It CITT
20000
7-11 JUL
20000
26-30 80
20000
28 JUL
RUG 80
Figure 14. Distribution of Aphanlzomenon gracile.
34
-------
20000
18-22 BUC 80
20000
it cirt
20000
8-12 5Er 80
tin
1st Cltl
20000
29 SEP - 3 OCT 80
it cm
Figure 14. (continued).
35
-------
This population seems to have completely replaced A_. flos-aquae, which
was previously abundant in many areas of Saginaw Bay (Stoerraer al. in
publication). The main differentiating characteristics between the two
species are in cell size (Huber-Pestalozzl 1938) and it is possible that the
two entities represent different growth forms of the same species. This
possibility has been debated in the literature without satisfactory
resolution. Most authors have chosen to retain the distinction since it may
be of ecological interest.
Gomphosphaeria lacustris (Figure 15)
This species is common in phytoplankton assemblages in mesotrophic to
eutrophic lakes in the summer. However, in Saginaw Bav, detectable cell
densities are already present in April at Wild Fowl Bay and nearby stations.
Population levels build slowly and erratically through early July, stabilizing
in late July, and then declining in late August. Moderate levels continue
through November at inner and middle Bay stations. Maximum cell densities
occur at nearshore stations near the river and along the eastern shore and to
the Lake Huron interface. An exception occurs in August when a pulse was
detected at stations from Point Au Gres eastward to Charity Island.
Microcoleus vaginatus (Figure 16)
This taxon reached its maximum abundance at nearshore stations In the
outer and middle Bay and so is somewhat atypical compared to other blue-green
algae. The only significant inner bay populations developed near the Saginaw
and Quaniccassee Rivers and at Wild Fowl Bay.
-------
Figure 15. Distribution of Gomphosphaerla lacustrls
-------
10-22 «JG 80
10000
8-12 SEP 80
CAST
but cm
29 SEP - 3 OCT 80
Figure 15. (continued)
38
-------
in late July, and then declining in late August. Moderate levels continue
through November at inner and middle Bay stations. Maximum cell densities
occur at nearshore stations near the river and along the eastern shore and to
the Lake Huron interface. An exception occurs in August when a pulse was
detected at stations from Point Au Gres eastward to Charity Island.
Mic.rocoleus vaginatus (Figure 16)
This taxon reached its maximum abundance af nearshore stations in the
outer and middle Bay and so is somewhat atypical compared to other blue-green
algae. The only significant inner bay populations developed near the Saginaw
and Quaniccassee Rivers and at Wild Fowl Bay.
Osci11atoria limnetica (Figure 17)
This blue-green filament is rarely reporttd from the Great Lakes.
In Lake Ontario, it was the most abundant alga on an annual basis in terms of
cell densities and the most important blue-green In terras of estimated cell
carbon content (Stoenru'r and Ladewski 1978). In Lake Huron, it occurred only
sporadically and v ^ry abundant (Stoermer and Kreis 1980). In Sagi-
naw Bay, it is ra; ' ted to the Saginaw River and Wild Fowl Bay.
Lower densities al d at Oak Point and at stations near the
Quaniccassee River. Maximum cell densities occurred in August and populations
persisted through September.
Qscillatoria rotzii (Figure 18)
This species is rarely recorded from the upper Great Lakes, but is
abundant in eutrophic environments. In Saginaw Bay, it first appeared in late
39
-------
Figure 16. Distribution of Microcoleus vaglnatus
40
-------
500
cm
500
20-21 OCT 80
CITT
500
10-IH NOV 80
cm
500
8-12 SEP 80
cm
EAST
500
29 SEP - 3 OCT
cm
Figure 16. (continued).
41
-------
Oscillatoria limnetica (Figure 17)
This blue-green filament is rarely reported from the Great Lakes.
Ir. ke Ontario, it was the most abundant alga on an annual basis in terms of
cell densities and the most important blue-green in terms of estimated cell
carbon content (Stoermer and Ladewsk.i 1978). In Lake Huron, it occurred only
sporadically and was never very abundant (Stoermer and Kre5s 1980). Ir Sagi-
naw Bay, it is mainLy restricted to t e Saginaw River and Wild Fowl Bay.
Lower densities also occurred at OaV Point and at stations near the
ijuaniccassee River. Maximum cell tensities occurred in August and populations
persisted through September.
Oscillatoria retzii (Figure 18)
This species is rarely recorded from the upper Great Lakes, but is
abundant in eutropnic environments. In Saginaw Bay, it first appeared in late
May samples and exhibited a short pulse in June in the Saginaw River. It
persisted through October in stations near the river mouth. Its broadest
areal distribution coincided with a second bloom in September and early
October. Except for sporadic occurrences near Charity Island, Oak Point,
and Wild Fowl Bay, it was found mainly in the inner Bay.
Pelonema spp. (Figure 19)
This atypical and apparently achlorotlc filamentous species is rarely
'port the literature. It seems closely related to the group of heter-
otr ilari r.tous species which have classical Ly been treated in both the
p'nycoiogical
-------
8000
CITT
OBT II
8000 T
16-20 JUN 80
CUT
5-9 MR'
8000
7-11 JUL 80
8000
28 JUL - 1 HUG 80
8000
26-30 MAT 80
cm
Figure 17. Distribution of Oscillatoria ]imiietica.
43
-------
19897
18-22 Rub 80
20-24 OCT 80
B-12 SEP BO
29 SEP - 3 OCT 80
Figure 17. (continued),
44
-------
Figure 18. Distribution of Oscillatoria retzii
-------
5000
5000
10-22 HUG 80
CIT1
scoo
6 -12 SEP 80
it cm
Dirt ti
5000
cm
5000
29 SEP - 3 OCT 80
Figure 18. (continued).
46
-------
40000
16-20 JUN 80
¦n cur
40000
1U-1P fiPfl 00
cm
40000
5-9 MAT
Cirr
40000
cm
40000
26-30 NAT BO
II CI"
40000
it cm
Figure 19. Distribution of Pelonema sp.
47
-------
40000
20-24 OCT 80
C1TT
40000
18-22
nuc 80
cm
40000
8-12 SEP 80
tin
40000
10-14 NOV 80
OBI
40000
29 SEP - 3 OCT 80
Figure 19. (continued).
Afi
-------
disturbed, originally ol igotrophic, alpine lakes in Europe (Huber-Pestalozzi
1938). In Saginaw Bay it is a numerically import component of phytoplankton
assemblages at a limited number of stations in the nearshore area from the
Quaniccassee River area to Oak Point. It is one of the dominants at Wild Fowl
Bay where it reaches its maximum cell densities. The high level of abundance
of Pelonema in this area is possibly indicative of organic loadings, although
further investigation would be necessary to establish this.
Porphyrosiphon sp. (Figure 20)
This genus is rarely reported from the Great Lakes. In Saginaw Bay it is
one of the summer dominants, appearing first in Jun^, reaching its maximum in
early September, and then declining in October. It reaches its maximum
densities at stations in and near the River, at Wild Fowl Bay and at mid-Bay
stations in the shallow water around Charity Island.
Schlzothr1x ca lei coin (Figure 21)
One of the important taxonomic characteristics of this species is lack of
definite cross walls betwween individual cells. Consequently, abundances
reported here for this species are in filaments/ml rather than cells/ml and so
cell densities are underestimated by a factor of 10-30 times. By either
density estimate, it Is one of the dominants at inner Bay stations from August
through October. Before and after this period, its spatial distribution was
sporadic and it occurred only occasionally In high abundance, especially at
nearshore stations and at Wild Fowl Bay. Its greatest abundance at a single
station was in late July-early August at Station 54 in the Saginaw River near
the town of Bay City.
49
-------
1000
16-20 JUN 80
cm
1000
tin
DOT
1000
7-11 JUL 80
CITT
1000
5-9 MAT
cm
cmt
28 JUL - I RUG 80
I' CI"
1000
26-30 HPT 80
CITT
Figure 20. Distribution of Porphyrosiphon sp.
50
-------
1000
cm
1000
20-2M OCT 80
cm
1000
8-12 SEP 80
CUT
1000
29 SEP - 3 OCT 80
CUT
Figure 20. (continued).
51
-------
Figure 21. Distribution of Schizothrix calcicola
-------
500
20-24 OCT BO
cm
500
18-22 AUG
ii cm
500
it cm
r
500
8-12 SEP 80
DOT
500
29 SEP - 3 OCT 80
cm
Figure 21. (continued).
55
-------
Bacillariophyta or Diatoms (Figure 22)
Members of this division are common and abundant in fresh, brackish, -,..u
marine environments. Although commonly associated with spring blooms in most
lakes, diatoms reach their greatest absolute abundance in Saginaw Bay in
September and October. However, diatoms are relatively abundant in spring and
do show declines in absolute abundance at soup stations in June and July.
During early summer, maximum abundances occur at and near the river and in
Wild Fowl Bay. During late summer and fail, inner Bay stations have much
higher cell densities than Bay-Lake Huron interface stations.
Cyclotella coroensis (Figure 23)
The seasonal and spatial distribution of this species in Saginaw Bay is
somewhat unusual for a diatom. Through June, low cell densities occur in the
outer and middle Bay. A strong pulse develops in July and August, highest
densities occur in the middle Bay and in the nearshore areas of the outer Bay.
In early August, moderate levels develop in the inner Bay and by late 'Vugust,
C. comensis is uniformly distributed across the inner and middle Bay. Cell
densities in the inner Bay drop in September, while high abundances persist in
the middle Bay. Abundances decline from late September through November.
Stoermer and Kreis (1980) found high abundances of this species in late summer
in Lake Huron. It had been found in the upper Great Lakes in low abundance
(Schelske e£ a1. 19/2, 1974; Lowe 1976). Its distribution in Lake Huron and
Saginaw Bay indicates that this species flourishes under low concentrations of
silica and high concentrations of nitrate (Stoermer and Kreis 1980).
54
-------
15000 T
16-20 JUN 80
•T CUT
15000
11—18 iifH 80
OCT T<
15000
5-9 MAT 80
15000
7-11 JUL 80
15000
28 JUL - 1 BUG 80
cm
15000
26-30 MAT 80
n cm
Figure 22. Distribution of diatoms.
55
V
-------
15000
18-22 RUG 80
15030
8-12 SEP 80
15000
Nja
cm
ISOOO
9 SEP - 3 OCT 80
Figure 22. (continued).
56
-------
Figure 23. Distribution of Cyclotella cor/rsis
-------
8000 t
18-22 MUG 80
IT CITT
8000
IT CITT
8000
I" CITT
8000
IT CITT
SEP - 3 OCT 80
IT CITT
Figure 23. (continued).
58
-------
Cyclotella comta (Figure 24)
This species is a member of the classical oligotrophic Cyclotella
association (Hutchinson 1967). It is apparently tolerant of moderate levels
of eutrophication but is absent from areas of the Great Lakes which have been
excessively disturbed (Hohn 1969, Duthie and Sreenivasa 1971). In Saginaw
Bay, it occurs in April and May but in very low densities. It is absent from
the Bay in June and in July occurs only at the Bay-Lake Huron interface
stations. Populations begin to increase again in late July, especially in the
region around East Tawas. By September, it has reached its apparent maximum
and numbers are declining by October. During summer months its distribution
is "-^neralLy limited to the middle and outer Bay. In spring and fall,
spovadic occurrences are recorded from the inner Bay.
Cyclotella menegheniana (Figure 25)
This centric diatom is distinctly riverine in its distribution and this
is reflected in sample from Saginaw Bay. Absent from all stations in April,
it occurred in the River on all cruises thereafter. Besides the River, the
only stations to have significant populations were Stations 2, 7, 8, and 12 at
the mouth of the River. A large pulse developed in July, densities declined
in early August, and then remained moderately high through early October. Low
levels persisted in the River area through November.
Cyclotella occllata (Figure 26)
This species is an Important component of phytoplankton assemblages in
oligotrophic areas of the Great La'/es. In Sagir.aw Bay it reaches its greatest
59
-------
14-10 APR 60
cm
16-20 JUN 80
cm
am
5-9 MAT 60
cm
ovt
7-11 JUL
cm
28 JUl \ RUG 60
cm
OVT
26-30 MAT 60
cm
Figure 24. Distribution of Cyclotella comta.
60
-------
ie-22
AUG 60
cm
8-12 SEP BO
cm
oar
20-2M OCT 80
cm
10-1U NOV 80
cm
29 StP - 3 OCT 80
cm
Figure 24. (continued).
61
-------
ISOO
1U-I8 RPR 80
cm
OBI
I50C
5-9 MfiT 80
CITT
16-20 JUN 80
15603
MT XI
- J JUL 80
26-30 MAT BO
not ti
28 JUL - 1 RUG 80
Figure 25. Dlscribuclon of Cyclotella menefthlnlana.
62
-------
1500 t
18-23 BUG 80
cm
1S00
cm
I SCO
29 5FP - 3 OCT
JO-14 NOV 80
Figute 25. (continued).
63
-------
16-20 JUN 00
Cirr
7-11 JUL 80
i> cm
ost
1-16 RPR 60
cm
5 -9 MAT
1*4
26-30 MPT 60
cm
OBI
Figure 26. Distribution of Cyclotella ocellata.
64
-------
cm
IT CJT1
TV
8-12 SEP 80
CPT
DOT
IT CI TT
DOT
29 SEP - 3 OCT 80
it cm
Figure 26. (continued).
65
-------
abundance in the middle and outer Bay in the spring and fall. In the inner
Bay it occurs only sporadically and never in great abundance.
Cyclotel]a pseudostelligera (Figure 27)
This is a small centric diatom with distinct riverine affinities.
Like C. meneghenlana, this species reaches high abundance levels in or near
the Saginaw River and it is persistent through all seasons. It is raOi.e widely
distributed in the Bay than is C. menegheniana, occurring sporadically in
nearshore areas in the middle Bay around Charity Island. However, cell
densities of this species away from the Saginaw River are always very low.
Fragilaria capuclna (Figure 28)
Although this species is most commonly reporter1, from small eutrophic
lakes, it can become a dominant in eutrophied portions of the Grpat Lakes
(Hohn 1969). In terms f cell densities, it is by far the dominant diatom in
Saginaw Bay on an annual basis; and, through most of the year, it is the most
abundant of all phytop'ankton species. In April, significant populations
develop in the middle Bay. Cell densities increase mainly in the middle and
outer Bay through May, with stations near the Saginaw River developing
relatively high levels in April and May. Inner Bay stations reach a
population maximum by June. Afterwards, numbers and distribution decline
slightly through August. Another large pulse then develops, mainly on the
western side of the Bay, and persists through November.
F ragiI aria crotonensi s (Figure 29)
This species is one of the most widely distributed and apparently
-------
ewi ti
600
16-20 JUN 80
cm
DOT II
600
11-18 APR 80
600
S-9 MAT 80
cm
600
7-11 JUL 80
cm
DOT TI
600
26-30 MAT 80
cm
600
28 JUL - 1 fiUC 80
Figure 27. Distribution of Cyclotella pseudostelligera.
67
-------
600
20-2U OCT 80
OBI II
600
18-22 HUG 80
Cirr
DB1 II
600
10-1H NOV 80
EAST
600
8-1? SEP 80
cm
HOT 11
600
29 SEP - 3 OCT 80
cut
Figure 27. (continued).
68
-------
OBI
10000
114-18 RPR 80
cm
10000
5-9 NAT
cm
10000
26-30 MAT 80
Figure 28. Distribution of
DOT
16-20 JUN 80
ii cm
7-11 JUL 80
cm
OOT
10000
28 JUL - 1 BUG 80
n cm
Fragilaria capucina.
69
-------
Figure 28. (continued)
-------
16-20 JUN BO
Figurs 79. DistribiLion of Fragllarla crotonensls.
-------
18-22 HUG 80
Fi,ure 29. (continued)
-------
eurytopic of all freshwater diatoms. It is common throughout the entire Great
Lakes system. It responds strongly to experimental phosphorus enrichment
l^toermer, Ladowski, and Schelske 1978), but is abundant in areas which
characteristically have low ambient concentrations of this nutrient.
In Saginaw Bay highest levels routinely occur in the middle Bay, indicating
that its development Is encouraged by moderate nutrient levels, but that it is
not as tolerant of more disturbed environments. Its distribution and
abundance are roughly uniform both seasonally and spatially in Saginaw Pay.
Cell densities are moderately high in April, with maximum abundance occurring
at the middle Bay stations. By June it has spread throughout the Bay, but
abundance levels decline in uer.rshore nro;.s in July and the largest popula-
tions are again found in the middle Bay. From August through early October it
reaches its greatest ienslties in the middle and inner Bay, but remains a
relatively important element of the stations at the nouth of the Bay. By No-
vember, populations have declined through most of Llie Bay with modest
abundance levels remaining again at the middle Bay stations.
Meloslra distans var. alpigena (Figure 10)
This species is a common component of phytoplankton assemblages of rivers
and it is rarely reported from offshore waters of the Cr^at Lakes. It reaches
its maximum density in Saginaw Bay at Station 54 in the Saginaw River and at
the stations at the mouth of the River. Sporadic occurrences of moderate
levels of the species were found from nearshore and shallow water stations.
Meloslra granulata (Figure 31)
This species generally reaches its highest nbunciau"e in small eutrophio
-------
iCQiSTvii east m
m-is 9Pn so
50 ¦
16-20 JUN 80
cm
00' Tl
'TV
/
V
Y
sc»
5-9 MOT 30
"TV
/
r
;
• \
• i
A/
^ *
/
?-n JUL 80
0 *
tar tMi
9
-------
IB-?.? BUG 80
lit
IRST II
OCT 80
175
i«T
29 SEP - 3 OCT 80
tin
Figure 30. (continued).
75
-------
TV
14-18 RPR 80
5- T MAT 80
26-30 Nht 80
BOO
16-20 JUN 80
CITT
800
7-11 JUL BO
cm
800
28 JUL - ! AUG BO
cm
Figure 31. Distribution of Meloslra granulata.
76
-------
8-22 BUG 80
0-12 SEP 00
"TV
BOO
20-2»i OCT 80
10-1U NOV 80
&/
800
29 SEP - 3 OCT 80
Figure 31. (continued)
77
-------
lakes where it often forms early summer blooms and early fall. It is common
in shallow eutrophied areas of the Great Lakes and in the offshore waters ol"
Like Erie, but rarely, if ever, reaches high abundance levels in offshore
water: of th> if' •" Great Lakes (Stoermer 1978). In Saginaw Bay it first
appears in tburd nice in and near the Saginaw River. Its npalial distribution
slowl*. ii. .s.»s until early September when it occurs in abundance throughout
the Bav with the exception of the offshore stations at the mouth of the Bay.
Population levels and distribution both decrease through November.
Melosira islandica (Figure 32)
This species is a common cold season dominant in boreal and alpine lakes
worldwide. It is common throughout the Great Lakes system and appear^ to be
favored by moderate levels of nutrient loading although it tends to disappear
from grossly perturbed habitats. Its distribution in Saginaw Bay is in accord
with these generalizations. In April and May it reached its greatest abun-
dance at mid-Bay stations and was absent from stations near the Saginaw River.
By late May, it occurred only at nearshorp stations in the outer one-third of
the Bay. In June a few cells were seen at East Tawas. It was absent from
r-amples until November when outer Bay offshore stations showed a sml l pulse.
Stephanodlscus blnderanus (Figure 33)
This species is a divnd Munawar 1974) , but Stoermer et^ jU. (19 7 ^) reported it froi..
offshore waters ir. Lake Ontario and Hohn (1969} found it in offshore waters of
78
-------
Figure 32. Distribution of Melooira islandica.
-------
DOT
C
30-2y OCT 80
ii cm
oat ti
8-12 SEP BC
mi Tims,
io-m nov bo
J
3 OCT 80
Figure 32. (continued).
80
-------
9T1IMXII ER5T
m-ie apr so
16-20 JUN 60
3*T CITT ~ nl
7-11 JUL 80
P6-30 Mm 80
/ 28 JUL - 1 RUG 60
Figure 33. Distribution of otephanodlBcus blnderanus.
81
-------
1
I
>
400
20-2U OCT 80
400
18-22 PUG 80
it cm
400
10-14 NOV 80
400
8-12 SEP 80
it cut
400 |
SEP - 3 0C1 30
Figure 33, (continued).
82
-------
Lake Erie. In Saginaw Bay, it reached its maximum abundance in early May at
stations near Charity Island and near the Quaniccassee River. Afterwards, it
occurred only sporadically and in low numbers until September when a small
pulse developed in the inner Bay. It persisted in moderate numbers at these
stations through November.
Stephanodiscus hantzschii (Figure 34)
This species is a common element of phytoplankton assemblages in
mesotrophic to eutrophic lakes. In April and (lay it wis present in moderate
abundance at nearly all of the stations between Charity Island and the Saginaw
River. In June, however, its distribution was mainly limited to stations in
and near the Saginaw River. Numbers declined through the summer and early
fall. By late fall, cell densities had again increased to detectable levels
in the inner Bay, primarily at nearshore stations on the east side and near
the Saginaw River.
Stephanodiscus subtilis (Figure 35)
In the Great Lakes, this spec s is associated with eutrophied areas,
particularly harbors and bays. Stoi'rmer and Kreis (1980) believed that near-
shore populations in Lik>' iluron wen* derived from ::vers. This species was
persistent in the Saginaw River throughout th-1 entire year. Cell densities
are high through thi spring but decline in August and September. From late
Scpttmber through November, abundance levels and areal distribution for this
species are at their f^rc est, as significant populations occur in and near
the Saginaw River and .if. nearshore stations in both sides of the inner Bay.
83
-------
5"*'™ r* r TiMts
IM-18 RPR 80
ens? t
JC j
5-9 MRT e.
26-30 MRT 00
,-X
Y?"-
16-30
/ ¦
I- -
frl ""
«» CJTt
A
„r-,j
28 JUL • Bug 80
Figure 34. distribution of Stephanodiscus hanttschii.
» Cl!t
q..
~5
84
-------
Figure 3A. (continued)
-------
Figure 35. Distribution of Stephanodiscus subtllis
-------
1000
18-22 BUG 80
1000
20-2M OCT 80 t
ERST IIMO^
B-12 SEP 80
1 CIT
10-m NOV 80
29 SEP - 3 0C. 80
Figure 35. (continued).
87
-------
Stephanodiscus tenuis (Figure 36)
This taxon is abundant in rivers throughout North America and in the
Great Lakes it is characteristic of mesotrophic to eutrophic areas. In Sagi-
n.iw Bay populations are strongly associated with the Saginaw River, and the
two stations (7 and 8) near the river mouth. In May, it reaches its greatest
distribution, occurring in abundance at several stations in the inner Bay and
sporadically and in low abundance near Charity Island. It persists in the
river, although in low abundance throughout the year. In late fall, popula-
tions again develop in the river and at stations in the extreme southeastern
portion of the Bay.
Synedra filiformis (Figure 37)
This species is common in the upper Groat Lakes in the spring and is
apparently tolerant of a wide variety of environmental conditions. In Saginaw
Bay, it is distributed over all stations in April and !iiy. Although numbers
are somewhat reduced at stations at the Bay-Lake Huron interface, it is
relatively abundant in these oligotrophic. waters. From May to early July, it
is largely absent from the Bay, but a large population develops in Wild Fowl
Bay in late July and persists through October. Sporadic occurrences of low
population levels are found in August and September at most middle Bay
stations. During August, moderate densities develop in the extreme south-
eastern portion of the Bay. This species was unique among diatoms in its
persistent, numerically important contribution to Wild Fowl Bay.
88
-------
3TTCHJI5 «5T T*«Sy
•py
urn tmj
1000 t
16-20 JUN BO t
0 i
5-9 MAT BO
7-11 JUL 00
¦» CITT
J
26-30 MAT BO
28 JUL - 1 AUG 80 I
I
0 ~
Figure 36. Distribution of Stephanodlscue tenuis.
89
-------
18-22 RUG 90
¦" CUT
20-2U OCT 80
B-12 SEP BO
0-4 NOV 80
29 SEP - 3 OCT 80
I CITT
Figure 36. (continued)
90
-------
800
16-20 JUN 80
BOO
m cm
800
"5-9 NAT 80
cm
800
JUL 80
CITT
900
08 JUL - 1 RUG 60
it cur
800
26-30 MAY 80
CIT
Figure 37. Distribution of Synedra filiformls.
91
-------
800
CITT
800
20-214 OCT 80
8-12 SEP 80
»1 CITT
It TME,
600
10-1U NOV 80
800
29 SEP - 3 OCT
CITT
Figure 37. (continued).
92
-------
Thalassiosira sp. (Figure 38)
Specific identification of this taxon could not he confidently made be-
cause of its small size and its weakly si'iicified valves. Most representa-
tives of this i;onus are marine and species with a freshwater distribution are
generally limited to rivers and to regions of high conductivity. TM - entity
reached its maximum abundpnee in the Saginaw River, occurring in the Bay only
sporadically and in low cell densities at stations near the river mouth.
Chlorophyta or Green Algae (Figure 39)
The green algal flora is more diverse and abundant in S'^inaw Bay than in
mosc areas of the upper Great Lakes. Green algae numbers increase in the
inner Bay from May through August. Cell densities during this period are
greatest in the eastern portion of the inner bay, somewhat lower in the
eastern middle Bay, and very low in the extreme western and middle Bay.
In September, maximum abundances are found at eastern stations of the inner
Bay, especially Wild Fowl Bay and Oak Point. Cell densities decline through
November; moderate levels are persistent in the extreme southeastern area and
in the Saginaw River.
Chodatella quadriseta (Figure 40>
This species is n common eLement of phytopiankton assemblages in
mesotrophic to eutrophic lakes. In the Laurentian Great Lakes, it is usually
found in significant abundance only in eutrophic areas. Initial development
of populations of chis species took place on the eastern side of the Bay in
early July. The maximum was reached in early August, and from late September
to November the species occurred only sporadically.
93
-------
T(OP» tiar t«n.
m-IB hph eo
r CItA-"7 o
/
1G0
X-'
16-20 JUN 80
7-11 JUL 80
SOT c n
26-30 Mflr 80
Figure 38. Distribution of Thalassioslra 8pp.
94
-------
419
100
18-22 BUG 80
CRV 11
100
20-24 OCT 80
» cm
100
10-IU NOV 80
It CtTI
100
8-12 SEP 80
ii cm
oot Tl
29 SEP - 3 OCT 80
Figure 38. (continued).
95
-------
f 15000
1H-18 RPR 80
JUN 80
BW /
out '««,
ISODO T
7-11 JUL 80
Dei tm.
25-30 MAT 80
I
1
far' isooo
/
/ 28 JUL - ! P'JC 80
Figure 39. Distribution of green algae.
96
-------
cm
20-2U OCT 80
cm
15000
8-12 SEP 80
tsooo
10-1IJ NOV 80
" cm
150GO T
c?9 SEP - 3 OCT 80
Figure 39. (continued).
97
-------
IM-ie HPH 80
T CUT
5-9 MAT 80
26-30 MRi 80
) JUN 80
?B JUL - 1 RUG 80
Figure 40. Distribution of Chodatella quadrlsete.
98
-------
Figure AO. (continued)
-------
Coelastrum microporum (Figure 41)
This species was present in low abundance in Che first two cruises.
Population development began in May in the inner Bay. Cell density increased
through June and July as the species spread through the inner Bay. After
early August, abundance decreased, although the species persisted through
November. Maximum abundance was reached in the southeastern corner of the Bay
and at the river mouth stations. This species is common in mesotrophic to
eutrophic areas of the Great Lakes.
Gloeotila pelagica (Figure 42)
Very large populations of this green filament developed in August but at
only a few stations. Maximum abundance was reached in early September in Wild
Fowl Bay where it was dominant. Its distribution also reached a maximum in
early September, but this species remained limited to nearshore areas along
the east side of the Bay and near the river mouth.
Mougeotia sp. (Figure 43)
We have been unable to make a satisfactory specific identification of
'lis entity due to the lack of sexually mature material. It occurred
radically in low abundance in the inner Bay until July when a large
population developed in the eastern Bay. Cell densities then declined slowly
throughout the rest of the year. As its numerical abundance decreased, its
distribution increased, and from August through October, it was found in low
levels from the shallows iust north of Charity Island, along the east side of
the Bay to the stations near the river mouth.
100
-------
16-20 JUS 80
2000
1M-IB RPR 80
ii cri
7-11 JUL BO
n cut
5-9 MKT 80
2000
2000
26-30 MKT 00
28 JUL - 1 BUG 80
Figure 41. Distribution of Coelastrum micropcrum
101
-------
2000
18-32 RUG 80
2000 T
20-24 OCT 80
ii cm
OBI
IT
l
2000
0-12 SEP 80
citt
2000
10-14 NOV 80
11 CJ"
2000
29 SEP - 3 OCT 80
It CI"
Figure 41. (continued).
102
-------
10000
N-18 APR 80
it cm
IS-20 JUN 80
mi cut
10000
7-U JUL 80
S-9 HRT 80
10000
26-30 Mat BO
10000
Figure 42. Distribution of Gloeotila pelagica.
103
-------
"py
DOT /
18-22 nuc so
B-12 SEP 80
\
0^
O ^ 1000C
¦/
/ 20-24 OCT 80
\ .
\s
^ fS tOQQG t
1
10-14 NOV 80
29 5EP - 3 OCT 80
Figure 42. (continued).
104
-------
1000
16-20 JUN 80
1000
5-9 MOT 80
citt
tooo T
JUL
100C
28 JUL - 1 BUD 80
» CI"
1000
26-30 urn 80
Figure 43. Distribution of Mougeofia sp.
105
-------
16-22 RUG BO
1000
20-24 OCT 80
9 I
B- 2 SEP BO
0-4 NOV 80
OCT 80
Figure 43. (continued),
106
-------
Pediastrum boryanum (Figure 44)
This species was one of the earliest blooming green algae. Sporadic
occurrences in April and early May preceded the maximum spatial distribution
of this colony-forming alga in June and July. Moderate levels occurred at
nearly all inner and middle Bay stations in June. By early August, its
distribution had declined to only a few stations. From this time through
November, occurrences of maximum abundance were mainly limited to near-river
stations and stations in the eastern inner Bay.
Scenedesmus acutiformis (Figure 45)
This species is rarely reported from the Great Lakes. Ir Saginaw Bay, it
reaches its maximum abundance and distribution in the Inner and middle Bay.
It first becomes abundant in August and reaches a maximum in September.
Numbers decline from late September through November.
Scenedesmus decorus var. bicandato-granulatus (Figure 46)
Like S. spinosus, this species reached its maximum abundances at shallow
water stations near the river and the eastern shore. Unlike J5. spinosus, but
like most other green algae, significant populations did not develop until
July. In early July, distribution was limited to nearshore areas of the
middle and inner Bay centered geographically around I'ild Fowl Bay. By late
July, this species reached its maximum cell densities and distribution. Its
bay-wide abundance declined slowly and its distribution was erratic through
November.
107
-------
PQMRTW DOT ra
1000 t
APR 60
TV
j.
1000 T
7-1! JUL 80
r citA-/ o
ERST
28 JUL - i RUG 80
Figure 44. Distribution of Pediastrum boryanum.
108
-------
Figure 44. (continued)
-------
1«-!B APR 00
1500 t
16-20 JJN 80
1500 T
7-11 JUL 60
cm
1500 i
5-9 MPT 80
IT CITT
1500 T
26-30 MAT 80
1500 t
1 HUC 80
Figure 45. Distribution of Scenedesaus acutiformis.
-------
1500 T
n CITY
1500 T
8-! 2 SEP BO
it cm
150!
20-21 OCT 80
IT CITT
ISOO T
10-11 NOV 00
1500
?9 SEP - 3 OCT 80
Figure 45. (continued).
Ill
-------
500 ,
16-20 JUN 80
ii cm
S00 I
m-18 APR 80
it cut
SOD T
5-3 HfiT 80
it cm
SQC T
7-11 JUL 80
500
28 JUl. - 1 BUG BO
cm
500 i
26-30 mi 80
cm
Figure 46. Distribution of Seenedesaus decorus var. blcaudato-granulatus.
112
-------
16-22 BUG 60
t cittN^/ o
•ay
20-?q oct 80
500
5EP 00
IO-:>4 NOV 00
29 SEP - 3 OCT 80
Figure 46. (continued).
113
-------
Scenedesmus spir.osus (Figure 47)
This was one of the most frequently occurring chlorophytes nf this study.
It was unusual among green algae in that it occurred in at least moderate
abundance in early spring, developing significant populations by late May, and
persisted in high numbers through November. Its highest densities were
restricted to nearshore areas, both near the river and in the eastern inner
Bay, into Wild Fowl Bay. In the outer Bay, low to moderate densities were
observed near Charity Island, Oak Point, and the Bay-like interface at
stations 52 and 53.
Cryptophyta or crypLomonads (Figure 48)
- cryptomonads are common in all types of fresh and brackish bodies of
water. in Saginaw Bay, highest abundances are reached in the inner Bay, but
this division is common at all stations at the interface of the Bay and Lake
Huron. Seasonally, highest abundance occur in late spring to early summer and
in late September but these peaks are not strong ones.
Chroomonas spp. (Figure 49)
These flagellated organisms have only recently been recognized as part of
the Great Lakes flora. Their spatial distribution is fairly uniform in
Saginaw Bay, although inner Bay stations, especially near the river and
nearshore stations, have slightly higher abundances. Seasonally, a slight
increase occurred between April and May. By June numbers had decreased across
most of the Bay. Cell densities increased slightly in August, increased in
September, and again decreased through November.
114
-------
oat
1000 T
1Y-18 APR 80
citt
DOT
1000 T
5-9 NAT 80
1000
26-30 MAT 80
it cm
Figure 47. Distribution of
115
EAST II
1000 T
16-20 JUN 80
1000 T
[JOT Tl
1000 T
28 JU. - 1 AUG 80
IT CITT
Scenedesmus gpinosus.
-------
OBI II
1000 T
18-22 RUG 80
i» cm
1000 T
n citt
DOt Tl
1000 T
8-12 SEP 80
1000 T
it citt
oat ti
1000
29 SEP - 3 OCT 80
It CITT
Figure 47. (continued).
116
-------
4000
11-18 BPR 80
CITI
obt ti
4000
5-9 MRT 80
26-30 NAT 80
16-20 JUN 80
4000
7-11 JUL 80
n CITt
4000
Figure 48. Distribution of cryptomonads.
117
-------
4000
18-22 AUG 80
4000 i
20-2W OCT
it cm
4000 t
B-12 SEP 80
4000
4000
SEP - 3 OCT 80
Figure 48. (continued).
118
-------
IMl T
1000 r
IH-1B hPR 80
20 JUN 80
16
WS* Tl
1000 t
5-9 HPT
en*
1000 t
26- 30 HPT 80
IT CITT
7-:i j*ol eo
t cm
"TV
28 JUL - I BUG 80
Figure 49. Distribution of Chroomonns spp.
119
-------
CAST II
1000 T
II CITI
18-2? RUG 80
II CUT
B8T II
1000 T
8-12 SEP 80
DOT Tl
1000
10-1M NOV
ii cm
HOT Tl
iooo r
29 SEP - 3 OCT 80
IT CUT
Figure 49. (continued).
120
-------
Cryptomonas ovata (Figure 50)
This species is common in the upper Great Lakes. Although it was present
in all portions of Saginaw Bay through most of the year, maximum abundances of
this species occurred in June in the inner Bay, and occurrences at the Bay-
Lake Huron interface were sporadic.
Rhodomonas minuta (Figure 51 )
This species has been observed throughout the upper Great Lakes, in both
inshore and offshore waters. In Saginaw Bay, this species occurs at all
stations and in all seasons. There is a tendency for higher cell densities in
both May and June, and then again in September, and at stations in the western
half of the inner Bay. In early May, cell densities are moderately high at
the Bay-Lake interface stations, indicating that this species is relatively
important in this region in the spring.
Chrysophyta or chrysophytos (Figure 52)
Many of the species of this group are reported from oligotrophic to
mesotrophic waters, but individual species may form blooms under a wide
variety of conditions. In Saginaw Bay, only moderate abundances of repre-
sentatives of this Division ever develop. Greatest cell densities occur in
nearshore stations on both sides of tho Bay. Excluding nearshore stations,
inner and outer Bay stations have roughly equal abundances of this Division.
Tnis, along with total phvtoplankton data (Appendix I), Indicates that chryso-
phytes are relatively important at outer Bay stations.
121
-------
400 t
iu-ia bpr eo
cm
400 T
16-20 JUN BO
IT cm
400 T
5-S MOT 80
"wt cm
EKST Tl
400 t
7-11 JUL 60
400 t
26-30 MAT 80
it citt
400 T
28 JUL - 1 AUG 80
Figure 50. Distribution of Cryptomonas ovata.
122
-------
HUG 80
20-24 OCT 80
cm ^ o
, 8-12 SEP 80
¦IT CITI^' Q
CK5T TIMK
0-14 NOV 80
29 SEP - 3 OCT 80
Figure 50. (continued),
123
-------
1500 T
16-20 JUN 80
Mr cin
IS00 T
11-18 BPfl 80
1500 T
S-9 MAT
1500
7-li JUL
H CI"
ISOO
26-30 MRT
1500 t
Figure 51. Distribution of Rhodomonas minuta.
124
-------
1500 T
tsoo
8-12 SEP eo
i! cm
it cm
1500
29 SEP - 3 OCT
it cm
Figure 51. (continued).
125
-------
»
4000 T
m-i8 hph eo
out Tl
4000
5-9 MAT 80
tin
4000
26-30 MAY 80
cm
Figure 52. Distribution
126
4000
16-20 JUN 80
4000
7-11 JUL 80
IT CUT
4000
28 JUL - 1 RUG 80
i- cut
of chrysophytes.
-------
€W1 t|
4000
CltT
4000
8-12 SEP BO
4000
29 SEP - 3 OCT 80
cut
4000
20-21 OCT 80
10- m NOV 80
Figure 52. (continued).
127
-------
Ochromonas spp. (Figure 53)
These organisms are common in all areas of the upper Griat Lakes.
In Saginaw Bay, late May densities are highest at Bay-Lake interface stations
but it is present at all stations. By late May, numbers have decreased in
most areas remaining high at a few stations surrounding, but not including,
Wild Fowl Bay. In .July, pulses occur at nearshore stations on the western
side of the Bay, the maximum being reached near Point Au Gres. From then
through November, distribution and abundance remains uniform except for a
strong tendency to very low abundances at the bay-Lake interface, reversing
the May trend.
Undetermined flagellates (Figure 54)
This category is likely composed of small Chrysophyta and Haptophyta
whose specific affinities cannot be accurately determined with standard light
microscope techniques (Stoermer and Sicko-Goad 1977). May cell densities were
the highest for most stations. However, Wild Fowl Bay and stati-"-^ in and
near the Saginaw River exhibited sporadic pulses from .June throu^i. "/ember.
Flagellate species #13 (Figure 55)
This taxon reached its greatest abundance in nearshore areas of the Bay.
In April moderate densities occurred in the middle Bay near Charity Island.
In May it reached its broadest distribution although cell densities were
greatest along both shores. Low to moderate abundances characterized the
middle and outer Bay from June through August. Moderate to low densities
persist in scattered locations in the middle and inner Bay from late October
through November.
128
-------
DOT
1H-18 RPR 80
2000 t
16-20 JUN 80
n ci't
?000 t
7-n ju:
IT CIT»
S-9 MAT
ii cm
2000
2000 r
26-30 MAT 80
28 JUL - 1 HUG 80
it cm
Figure 53. Distribution of Ochromonas spp.
129
-------
20-2V OCT 80
CJTf
2000 T
1-22 BUG 80
citt
2000 T
10-IV NOV BO
it till
8-12 SEP 80
tin
2000 i
29 StP - 3 OCT 80
cm
Figure 53. (continued).
130
-------
I
DOT II
1500
16-20 JUN 60
cm
1500
cirr
DOT Tl
1500
5-9 MAT 80
cm
26-30 NAT 80
OBI Tl
1500
7-11 JUL 80
cm
1500
28 JUL - 1 flUC 80
Figure 54. Distribution of undetermined flagellates.
131
-------
1500
18-22 RUG 80
nor Ti
1500
20-24 OCT 80
ciri
1500
1
io-m NOV 80
1500
Figure 54. (continued).
132
-------
ISO
16-20 JJN 80
150
14-lb RPR BO
CITT
ISO
mar-
lb:
5-9 MOT 80
CUT
CAST Tl
ISO
ISO
26-30 MOT BO
1 BUG 80
IT CUT
Figure 55. Distribution of flagellate species #13.
133
-------
ISO
18-22 RUG 60
IT CITT
150 T
8-12 SEP 80
cm
150
CITT
150
10-11 NOv
CITT
150
29 SEP - 3 OCT 80
cm
Figure 55. (continued).
-------
Pyrrhophyta or dinoflagellates (Figure 56)
Although the dinoflagellates are relatively rare in the Great Lakes, they
may constitute a significant portion of the biomnss because of their large
size. Ecological affinities of many freshwater species are poorly known.
As a group, dinoflagellates are common but not abundant throughout the Bay.
Seasonal and spatial distribution is relatively uniform although there is a
tendency for higher densities nearshore in the eastern Bay.
Euglenophyta (Figure 57)
This division reaches its greatest abundance and diversity in wafers hi^h
in organic carbon. Representatives of this division are very rarely reported
from the Great Lakes and never In abundance. Sporadic occurrences of very low
cell densities in the inner Bay characterize this division's distribution in
Saginaw Bay.
Community Analysis
This pari of this report examines spatial and seasonal distributions of
more or less well defined phytoplankton communities. Two multivariate
statistical methods, principal components analysis (PCA), and cluster analysis
(see Sneath and Sokal I1' wr*re used to identify taxa whose distributions
were closely assoclat • another. Cluster analysis Illustrates well
In graphic form the mi >• relationships of stations or samples that are
highly similar. Complet- wiktge was the clustering strategy applied to the
Euclidean distances among stations or samples. Principal component-: analysis
135
-------
16-20 JUN BO
60 T
7-11 JUL 3C
cm
U-18 RPR 80
5-9 MAT 80
26-30 MRY 80
it cm
60 t
28 JUL - 1 RUG 80
Figure 56. Distribution of dinoflagellates.
136
-------
TV
DOT II
18-22 AUG 60
8-12 SEP 80
it cm
60 t
Svn cirt
29 SEP - 3 OCT 80
it cm
Figure 56. (continued).
137
-------
Figure 57. Distribution of euglenophytes
-------
cm
16-22 AUG 60
cm
DOT
8-12 SEP 80
it cm
io-m ncv
IT CITT
29 SEP - 3 OCT 60
cm
Figure 57. (continued)•
139
-------
illustrates and explains the relationships and differences among phytoplankton
associations previously defined by c.^ster analysis. Principal components
analysis (PC/.) was performed on the matrix of correlation coefficients of
seiec.s;.! ti'xa. Over 500 taxonomic entities were recorded in this study, at
.'rrious taxonomic levels. Even with computer-aided analyses, this is an
i! -Isldly collection of variables. Before a taxon was included in
multivariate analysis, it had to meet two criteria: that it be well defined
taxonomically, i.e. at the genus level or lower; and, that it was amcng the
twenty most abundant taxa on at least one cruise. Fifty-seven taxa met these
criteria (Table 5).
Average Bay-wide Community Analysis
For this analysis, the mean of each species was calculated for each sta-
tion over all cruises. This effectively integrated the seasonal component of
variation and allowed better recognition of average spatial relationships.
I 57 taxa listed in Table 5 were used in this analysis.
Stations were divided in two two major regions based on the phytoplankton
community associations (Figure 58). Region A was a loose association of
stations at or near the mouth of the Saginaw River. This region could be
identified via both cluster analysis and PCA (Figures 59, 60, and 61). Region
B consisted of 3 subgroups (Figure 58) which could be identified by cluster
analysis (Figure 59). Figures 60 and 61 illustrate that these subgroups merge
one into the other in a sequence which reflects their geographical
relationships (Fif re 58). Two stations. Stations 34 and 54 (Wild Fowl Bay
and the station at Bay City), are distinct from all other stations (Figures
60 and 61). Station 44, Oak Point, may be thought of as intermediate to
140
-------
TABLE 5. RESULTS OF PRINCIPAL COMPONENTS ANALYSIS
FOR AVERAGE BAY-WIDE COMMUNITY ASSOCIATION STUDY
FACTOR LOADINGS
PC T PC II PC III
Taxon % variance 36 o 18.4 10.8
Anabaena flos-aquae
Asterlonella formosa
Anacystls cyanea
A^. incerta
Aphanlzomenon gracile
Blue-green filament '.f3
Blue-green filament #4
Chodatella quadrlseta
Coelastrum microporum
Coelastrum spp.
Cryptomonas spp.
Cyclotella comensIs
£. meneghlniana
C. pseudostelligera
Dictyosphaerium ehrenbergianum
Diatoma tenue var. elongatum
Dlnobryon spp.
Flagellate "10
Fragilaria capuclna
F. crotonensls
£. pinnata
Gloeocystis planctonlca
Gloeocystls spp.
Gomphosphaerla lacustrls
G. wtchurae
Gloeotlla pelagicr.
Gloeotlla spp.
Chroomonas spp.
Kirchneriella spp.
Mlcrocoleus vaglnatus
Meloslra granulata
N1tzshia spp.
Ochromonas spp.
Oo ystls spp.
Oscillatoria llmnetlca
0. rer-11
Oscl1 oria spp.
Pedtaslrum boryanum
(cont t nued)
.02416
.04175
.05618
.01208
.01907
-.05515
.20020
-.01386
.09893
.16228
-. 15727
.02471
.13827
-.21229
.00065
.07591
-.26259
-.09095
.084 93
-.27353
-.07891
.11442
-.06891
.09731
. 18758
.08575
.09353
-.01195
.02225
.03705
.14322
.15967
-.10597
-.05052
-.21339
.07133
.05985
.11612
-.34136
.06974
.12199
-.32877
.16291
.10633
.03436
.15271
.02394
.11389
-.00261
-.04430
.11615
.23038
-. 17326
-.07452
.10738
.10233
.18021
.10705
.01069
.18762
.11174
-.24221
-.05392
.17107
.10863
.09010
.10845
.10173
-.08966
.18017
-.00002
. 13241
.12501
.05673
.10163
.14572
-.20429
-.03024
.06489
-.20681
-.02627
.15656
.05465
-. 14713
.15328
.08898
.12582
-.05758
-.02264
-.00434
.12199
.16047
1 8
.12637
-.24264
-.L. . . i
.14 732
-.02437
.22765
.11670
.00755
.15279
.17277
.02307
.15309
.09074
-.25146
-. 14213
.12429
.11688
-.24555
.07176
.084 76
-.29711
.17417
.03842
.07107
141
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TABLE 5. (continued).
.JTOR LOADINGS
PC I PC II PC III
Taxon % variance 36.8 18.4 10.8
Pelonema sp.
Porphyrosiphon sp.
Rhodomonas minuta
Scenedesmus acumlnatus
53. acutlformis
armatus var. boglariensis
j3. carinatus
S^. decorus var.
bicaudato-granulatus
A* quadricauda
S. spinosus
Scenedesmus spp.
Stephanodlscus binderanus
£. hantzschil
S^. subtilis
, tenuis
Synedra filiformis
Tabellaria flocculosa var. linearis
Fragilaria construens
09450
-.26079
-.07314
13691
-.05083
-.15433
05836
.11504
.09792
19940
.05815
-.08842
17954
.02400
.15380
18023
'300
.04192
17193
•331
.07916
.19904
.01820
. 10051
.20088
.04706
-.00878
.19988
.01268
.04788
.20689
.00986
.01359
.04643
.04626
.16890
.12858
.08257
.11475
.12119
.14834
-.25658
.14380
.14412
-.16188
.08321
-.26634
-.06568
-.04 923
-.04022
.12684
.15043
-.21139
-.04 348
142
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EAST TAWAS
I
¥
¥
fl2>
MEANS
BY
STATION
BAY CITY
Figure 58. Region, of Saginaw Bay baaed on average phytopl.nkton
assemblage associations.
143
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ST * T 10 I
2
7
">S
t
12
^6
1
52
19
50
51
53
15
18
17
J42
35
37
13
60
36
3$ _
18
22
27
32
2B
1? _
j<1
51
31
B.
B,
B
1
Figure 59. Cluster analysis of average bay phytoplankton communities.
-------
PC II
'54
21 22 _ IT
J> R|
/^«0 21
b2 »,
Vs".il
?s
si i;
4 4
PC I
1 4
Figure 60. Principal components analysis of average Bay phytoplankton
communities. Scatter plot of Saginaw Bay stations on PCI and PC1I.
145
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PC III
« )J
PC I
Figure 61. Principal components analysis of average Bay phytoplankton
communities. Scatter plot of Saginaw Bay stations on PCI and PCII.
146
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regions A and B in community structure and abundance (Figures 60 and 61),
although it is only loosely associated with either.
Species loading on principal components axes (PC axes) give some insight
into differences among station groupings based on phytoplankton associations.
Loadings on PC 1 ire nearly equal and all are near zero or strongly positive
(Table 5). Thus, the major average differences among stations are not in
kinds of «pecies but in levels of phytoplankton abundance. That is, stations
to the right of Figures 60 and 61 tend strongly to have higher abundance
levels than stations on the loft. However, qualitative information makes
finer distinctions among stations and regions '"han purely quantitative data.
Separation of Wild Fowl Bay and Oak Point from each other and from the
rest of the stations occurs on PC 11 (Figure 60). With the exception of
Synedra filiformis, species heavily loaded on this axis (arbitrarily, loading
factors > 0.25; Table 5), are all blue-green filaments. Individual species
plots previously showed that high abundances of these filaments and
JS. f 11 iformis were characteristic of Wild Fowl Bay and Oak Point. PC III
separates station 54 from all other stations (Figure 61). Species heavily
loaded on PC III (arbitrarily, loading factors >0.25; Table 5) are mainly
diatom species with distinct riverine distribution (Table 5, and individual
species plots).
Region A was characterized by Gloeotila spp., Rhodomonas minuta, certain
riverine diatoms, namely Cyclotella meneghinlana, Melosira granulata,
Skeletonema costatum and Thalassiosira spp. and hv the blue-green filaments
Aphanlzomenon graci le, blue-green rilament //4, Oscillatoria limneticn,
Pelonema sp. and I'orphyrosiphon sp. Also characteristic of A was the diatom
Synedra fillformls, which was again found In association with several bltie-
1 hi
-------
green filaments, although these were not the same blue-green species with
which it was associated at Wild Fowl Bay.
Three ireg.Tia were identified in Regie. 1 B. Region Bj is characterized
by high abundances of the blue-green algal Oscillatoria retzii, several green
algae including Scenedesmus carina, S. spinosus and Coelastrjm microporum, the
cryptomonads Rhodomonas minuta and Cryptomonas spp. , and the diatom
Stephanodiscus subtilis. Species loadings and individual species plots
indicate that Region B2 has a mesotrophic character relative to Bj, and hat
high abundances of the cryptoraonad Chroomonas spp, , and the eurytopic diatoms
Nitzschia spp., Tabellaria flocculosa var. linearis, Asterioneila formosa,
Cyclotella comensis and Synedra filiformis characterize region B2. Species
factor loadings indicate that none of the dominant species are strongly
associated with region B7. However, individual species plots show that
several species characteristic of the open waters of Lake Huron have Saginaw
Bay distributions generally restricted to, or reach their greatest abundance
at, stations in Bj. These species include the diatoms Melosira lslandica,
M. ita1ica, Cyclotella ocellata and £. comta, the chrysophyean alga
Spiniferemonas sp., and flagellate species #13.
In summary, the river -a in the inner Bay, i.e. Region A and station
54, was ' haracterized by diatom spe >s which reach their highest abundances
in the River proper, as well as many blue-green filaments which are indicative
of highly eutrophic conditions. The floristic elements associated with region
B indicate a transition across a broad front from the inner Bay to the outer
Bay stations. Only a few distinctly riverine taxa or taxa indicative of
severely disturbed habitats (in particular, Stephanodiscus subtilis and
Oscl1latoria retzii) are numerically important in B. A more mesotrophic flora
148
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consisting mainly of eurytopic diatoms is characteristic of region B2- Total
phytoplankton abundances are also lower in B2 than in Bj. Total abundances
are lowest of all in B3 and this region is characterized by diatoms and
flagellates associated with oligotrophie conditions. Thus, on the average,
all stations at the Bay-Lake Huron interface are more like one another, both
in kinds of species and in cell densities than they are like stations in the
middle Bay. Wild Fowl Bay and Ua*. Point are characterized by exceptionally
high abundances of blue-green filament species. The distribution of several
of these species is restricted to Wild Fowl Bay and the immediate area. The
high standing crops of species unique to Wild Fowl Bay, and to a lesser
extent, Oak Point, suggests that these areas nay not be well integrated with
the rest of the Bay.
Community analysis by cruise
For this part of the analysis, phytoplankton assemblages were rntified
by cruise with multivariate analyses on the 20 most abundant taxa for that
cruise.
Cruise 83, April 14-18 (Figure 62)
Saginaw Bay could be divided into three regions. Region A consisted of
stations at or near the Saginaw River. Characteristic of this region were
several taxa with eutrophic water affinities and others generally limited to
the River, including Gloecystis spp., Scenedesmus spp., Stephanodiscus
subtllis and S^. hantschii. Region B was a loose association of four stations
characterized Hy the eurytopic diatoms Fragilaria crotonensis, pinnata and
F. capucina, and the blue-green alga Gomphosphaerta lacustrls. Region C was a
149
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EAST TAWAS
BAY CITY
Figure 62. Regions of Saginaw Bay during cruise 83.
150
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tight association of stations characterized by the flagellates Qchromor.as spp.
and Chroomonas spp. , and the diatom Cyclotella comensis. Station 16 was not
associated with any region. Abundance levels of most all species were very
high at this station, but especially abundant at this station were Anacystis
incerta, Asterionella formosa, Diatoma tenue var. elongatum, Stephanodiscus
hantzsc.hii and Synedra fi 1 iformis.
Cruise S4, May 5-9 (Figure 63)
Station clusters were not as well defined on this cruise. Most of the
middle and inner Bay stations formed a loose cluster (Region C) which wac
geographically and floristically central to several outlying regions. The
river stations formed one endpoint (Region A) , characterized primarily by the
riverine diatoms Cyclotella pseudostelligera, Stephanodiscus tenuis,
Stepham 'scus subtilis and Olatoma tenue, and secondarily by the eurytopic
species Asterionella formosa, Rhodomonas minuta and Chroomonas spp. Region B
represented the transition between riverine (A) and Region C stations, and was
characterized by the riverine diatoms Stephanodiscus tenuis, S. subtilis,
Cyclotella pseudostelligera and Diatoma tenue var. elongatum, and by S^.
binderanus, Chroomonas spp. and Fragilaria capucina. Region C could not be
well characterized but contained floristic elements of all the surrounding
regions. Region D represents the transition betwr.on C and E and was
characterized by eurytopic algae such as Fragilaria capucina, Cyclotella
comensis and Chroomonas spp., and by two diatoms characteristic of open Lake
Huron waters, Mjlosira islandica and Cyclotella ocellata. Region E was
151
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EAST TAWAS
<< c i
Yl
22
BAY CITY
Figure 63. Regions of Saginaw Bay during cruise 84.
152
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characterized by Cyclotella comensi s, £. ocellata, £. stelligera, Meloslra
Islandica and relatively high levels of Rb jomonas mlnuta.
Cruise 86, May 26-30 (Figure 64)
live assemblages were recognized. Region A was composed of three
stations in and near the Saginaw River. Characteristic of this region were
Scenedesmus spinosus, S^. quadricauda, S^. armatus var. boglariensis, S>.
acur.inatus, Gleocystis planctonica, Coelastrum microporum, Stephanodiscus
tenuis and 55. subtilis. Region B was a loose association of inner Bay
nearshore stations characterized by flagellate species y'13, Chroomonas spp.,
Scenedesmus quadricauda, Scenedesmus spp., Cryptomonas spp. ind Pediastrum
boryanum. Region C was characterlz d by Anabaena f1os-aquae, Rhodomonas
mlnuta and Fragilaria capucina. Region D is intermediate geographically and
floristicaly to Regions B and E. Characteristic of D are Chroomonas spp.,
flagellate #10, flagellate //13, Ochromonas spp., Cyclotella comensis and
Tab i ia flocculosa var. linearis. Region E is characterized by Cyclotella
comensis, £. stel 1 igera, flagellate 013 and Monoc.hrysis aphanaster.
Cruise 37, June 16-20 (Figure 65)
No samples were taken from Se nent 5 on this cruise. Four regions could
be identified from tht. rest of the Bay. Region A, composed of stations in and
near the River, was characterized by Stephanodiscus tenuis, Gleocystis
planctonica, Scenedesmus spp., S5. spinosus, S. quadricauda, Osclllatorla
retzll and Anacystls Incerta. Region B was composed of Inner Bay stations,
forming a loose cluster characterized by Rhodomonas mlnuta, Anabaena flos-
aquae and Gomphosphaerla lacustris. Region C was co- osed of stations in the
153
-------
EAST TAWAS
U
35
Figure 64. salons • . ginav Bay during cruise 86.
154
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EAST TAWAS
1
uea ;
N
BAY CITY
Figure 65. Regions of Saginaw Bay during cruise 87.
155
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middle Bay and characterized by Monochrysis aphanaster, Mallomonas
pseudocoronata, flagellate <'13, flagellate /'10 and Cyclotella stelllgera.
Region D was characterized by Cyclotel la stelllgera, C^. ocellata and
Microcolens vaglnatus.
Cruise 88, July 7-11 (Figure 66)
Segmentation of the Bay during this cruise indicates a possible strong
influx of Lake Huron water into the Bay. Note that the outline of Regions C
and D resembles the 8 m depth contour. Four regions were recognized.
Region A is a loose association of stations characterized by Oscillatoria
retzll, Anacystis incerta, Goraphosphaevia lacustris, Coelastrum microporuro,
Scenedesmus acuminatus, 55. quadricauda, f5. acumir.atus, 55. carina, Cyclotel la
meneghinlana, and Meloslra granulatn. Region B was characterized by Anacystis
cyanea, Scenedesmus spinosus, Fragllaria capucina and Cyclotella comensis.
Region C Is a loose assemblage of stations characterized by high abundances of
species typical of both regions B and D, including Cyclotella comensis,
Fragilarla crotonensis and Scenedesmus spinosus. Relatively abundant in
Region D were eurytopic taxa and taxa which frequently occurred at the Bay-
Lake Interface Including Fragilarla crotonensis, Cyclotella stelllgera,
Chrysococcus dokldophorus, flagellate it 10, flagellate #13 and Dlnobryon spp.
Cruise 90, July 28-August 1 (Figure 67)
Three geographical regions could be Identified in Saginaw Bay, and three
stations represented separate point clusters which could not satisfactorily be
placed in any region. Station 12 was characterized by generallv high total
phytoplankton abundances and specifically by high levels of Anacystis cyanea,
1 ri6
-------
EAST TAWAS
4i
55
bay city
cruise 88.
66. Regions of Saglnnw Bay during
Figure
157
-------
EAST TAWAS
49
42
36
34
rT
54
BAY CITY
Figure 67. Regions of Saginaw Bay during cruise 90.
158
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Scenedesmus spp., acuminatus, carina and Fragllaria crotonensis.
Station 34 was characterized by blue-green algae, especially Anacystis
incerta, Pelonema sp. and Aphanizomenon gracile. Station 54 was characterized
by moderate abundances of such riverine diatoms a" Skeletonema potamos,
Cyclotella pseudostelllgera and Stephanodiscus subtilis, and by the blue-green
filament Schizothrix calcicola. Region A was a loose cluster of stations
characterized by Fragilaria crotonensis, Anacystis incerta and Scenedesmus
spinosus. Region B was characterized by the eurytopic Fragllarla crotonensis,
Cyclotella comensis, Rhizosolenia eriensis, and the oligotrophia indicators
Cyclotel1 a comta and Monochrysis aphanaster. The assemblage and abundance
levels in this region suggest a nesotrophic water body. Region C was
characterized by oligotrophic indicators Cyclotella stelllgera, C. comta and
Chrysococcus dokidophorus, and the eurytopic comensis.
Cruise 91, August 18-22 (Figure 68)
Four regions and a single point cluster were Identified. Station 34
(Wild Fowl Bay) had a unique assemblage and could not be associated with any
other station or stations. Wild Fowl Bay was character!zed by high standing
crops of blue-green filaments, especially Pelonema sp., Osclllatorla
limnetIca, blue-green filament 03, blt?-green filament '/A, Schizothrix
calcicol."., the green filament Gloeot l la pelagica, and the diatom Synedra
filiformls. Region A was composed of Saginaw River and near river stations
and was characterized by Cyclotella meneghi niana, Meloslra granulata,
Fragllar la capuclna, Osci l latorla retzil , Scenedesmus spinosus, £. quadrIcauda
and Fed last rum boryanum. Region B was characterized by a mlxiure of blue-
greens, eurytopic diatoms and greens, and so was Intermediate florist leally
l 59
-------
w
EAST TAWAS
52
34
BAY CITY
Figure 68. Regions of Saginaw Bay during cruise 91.
160
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between station 34 and regions A and C. The taxa Included Schizothrix
calcicola, Gomphosphaeria wlchurae, Anacystis cyanea, Pediastrum boryanum,
Scenedesumus acutiformls, Fragilaria capucina and Cyclotella comensis.
Region C was characterized by a mixture of eutrophic, eurytopic and
oligotrophia forms, Including Anacystis Jncerta, Coelastrum microporum,
Fragilaria crotonensis, Cyclotella comensis, C^. comta, £. stelligera,
flagellate #13 and Qchromonas spp. Region D was characterized by algae
typical of the Bay-Lake interface, Cyclotella stelligera, Cyclotella comta,
flagellate "10 and flagellate "13.
Cruise 92, September 8-12 (Figure 69)
When the Bay reached its maximum total phytoplankton abundance in early
September, it simultaneously reached its apparent greatest diversity and
divergence of apparent ytoplankton habitats in that four stations formed
separate point clusters. Each of the eastern nearshore stations contained
uniqu.' assemblages, very distinct from one another and from the open Bay.
Even the stations In the inner and middle Bays were relatively distinct from
one another. Nevertheless, they could be still identified as one loosely
defined region (A) with little floristic similarity to a second region (B), or
to the separate point regions. Station 34 was again characterized by blue-
green filaments, as it was during most of the summer and early fall. Taxa
important at Wild Fowl Bay were Pelonema sp., Aphanizomenon graclle, blue-
green filament #3, blue-green filament //4, Anacystis cyanea, Gloeot i la
pelag lea and Synedra f111formls. Station 44 ha 1 high abundances of Gloeot1 la
spp., AnacystIs 1ncerta, Anacystis cyanea and Mougeotla spp. Station 54, in
the Saginaw River, was characterized by the riverine diatoms Cyclotel1 a
iM
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EAST TAWAS
BAY CITY
Figure 69. Regions of Saginaw Bay during cruise 92.
162
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meneghiniana, and Skeletonema potamos, and by Oscl1latoria xetzii and
Chroomonas spp. Station 56, characterized by Coelastrum microporum,
Sc-' nedesmus spinosus, Oocystls spp. , Osci 1 latoria retzii and Melosira
granulata, was somewhat intermediate to station 54 and to Region A. Region A
was characterized by Fragilaria capucina, F\ crotonensis, Cyclotella comensis,
Melosira granulata, Rhodomonas minuta, Ochromonas spp. , Scenedesmus
ac.utiformis and S^. spinosus. Region B was characterized by Cyclotella
stelligera, (3. comta, C^. comensis, Fragilaria crotonensis, flagellate //10,
flagellate #13 and Monochrysis aphanaster, all species typical of the Bay-Laic;
interface.
Cruise 93, September 29-Octobor 3 (Figure 70)
Four regions could be identified during this cruise. Region A was a
loose association of stations in and near the River, characterized by
Oscl1latoria retzii, Cyclotel la meneghiniana, Melosi ra granulata, Fragilaria
capucina, Scenedesmus quadricauda, S^ decorus var. bicaudato-granulatus, S_.
acuminatus and Chroomonas spp. Region B was composed of eastern inner Bay
stations a.:d characterized by several blue-green algae and green algae.
Including Pelonema sp., Aphanizamenon gracile, Anacystis incerta, /V. cyanea,
lue-green filament /f4, Scenedesmus acutif ormis, S. spinosus, and by eurytopic
species such as Fragilaria crotonensis and Rhodomonas minuta. Region C was
characterized by Cvclotella comensis, Melosira granulata, Fragilaria capucina,
Rhodomonas minuta and Scenedesmus acutiformis. Reg!~>n D was characterized by
eurytopi*- and oligotrophic species such as Fragilaria crotonensis, Cyclotella
comensis, C. stell lgera, comta and Chrysococcus dokldophorus.
1 (S3
-------
EAST AWAS
9
$
BAY CITY
Figure 70. Regions of Saginaw Bay during cruise 93.
164
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Cruise 94, October 20-24 (Figure 71)
Although the outer row of stations at the Bay-Lake interface was not
sampled on this cruise, three regions and two point clusters could still bo
identified. Wild Fowl Bay again formed a separate point" assemblage which was
characterized mainly by the blue-green algae Pelonema sp., Schizothrlx
calcicola, Anacystis incerta and A. cyanea. Synedra filiformis was again an
important component of the phytoplankton assemblage at this station. The
River was also distinct, characterized by relatively high levels of the
riverine diatoms Skeletonema potamos and Stephanodlscus subtilis. Region A
was characterized by Monochrysis aphanaster, Scenedesmus acutiformis, S_.
spinosus, Cyclotella meneghlniana, Fragilaria capucina and Melosira granulata.
Region B was characterized in part by Gomphosphaeria lacustris, Anacystis
cyanea, Aphanizomenon gracile and Cyclotella meneghlniana. Region C was not
well-defined but did have moderate abundances of algae which did not occur in
other regions, Including Cyclotella comensis, C. stel li gera and Rhizosolenia
eriensis.
Cruise 95, November 10-14 (Figure 72)
Four regions were identified. Region A was characterized by the riverine
diatoms Step anodiscus subtilis, 55. tenuis and Cyclotella pseudostelllgera,
and by the blue-green algae Anacystis c>anea, Schizothrlx calcicola and
Pelonema sp. Region B was characterized by mesotrophic and eurytopir taxa
such as Cyclotella comensis, Fragilaria capucina, Scenedesmus armatus var.
boglarlensis, j?. carina and Gomphosphaeria lacustris. Region C was
characterized primarily by eurytopic taxa: Fragilaria capucina, Rhizosolenia
eriensis, Mlcrocoleus vaginatus, Ochromonas spp. and Chroomonas spp. Region D
165
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east tawas
i
BAY CITV
Figure 71. Regions of Saginaw Bay during cruise 94,
166
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EAST TAWAS
143
X
BAY CITY
Figure 72. Regions of S-flnaw Bay during cruise 95.
167
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was characterized by the presence of eurytopic and oligotrophia taxa such as
Cyclotella stelligera, £. comta, Melosirn islandica, Fragilaria crotonensls
and flagellate #13.
DISCUSSION AND CONCLUSIONS
Water current patterns and entraiirnent of water masses from Saginaw Bay
and Lake Huron apparently controlled phytoplankton distribution and abundance
in most of Sagiraw Bay during 1980. This general hypothesis
-------
Bratzel j?t a\_. ( 1977) suggested that phytoplankton populations char-
acteristic of the Bay exit into Lake Huron through the Bay region they
designated as Segment 5. This phenomenon, documented with 1974 data by
Stoet.uer and Kreis (1980), appears to have occurred in 1980, although
certainly not to as great an extent as in 1974. Cell densities in the western
outer Bay (Segment 4) are lower than densities in the eastern outer Bav
(Segment 5). However, this difference is not statistically significant
(Table 4). Community analyses showed th?: this is because Segment 5 is a
heterogenous collection of stations whose phytoplankton assemblages are
general Iv unrelated.
On • 'n.- all stations along the Bay-Lake interfacr- .•lu->c *r ;.1
'oivther, irregardless of which segment they nay occur in. On any one cruise,
however, the phytoplankton assemblage it Station S3 may be similar to stations
in Segments 2 or 3 in the inner Bay and/or to Station 44 (e.g.. Figures 63 and
hi). Thus, phytoplankton transport out of the Bay was limited to the extreme
nearshore portion of Segment 5 during the periods sampled in 1980.
This point is of interest for the following reasons. Two nearshore
stations, 34 in Wild Fowl bay (Segment 3) and 44 at Oak Point (Segment 5),
each have unique phytoplankton assemblages, in tlv avi-r.i.**' rase, in terms
of kinds and amounts of algae present. This indicates a nearshore
effect which overwhelms or at least strongly modifies the Saginaw Rtver
influr.ice on phytoplankton assemblages in the Bay region which appears to
make the most Immediate contribution to Lake Hu'on. It 1^ iof-ri-sring that
Station 44 (Oak Point) is located intermediate to Station 34 (Wild Fowl Bay)
and the inner and middle Bay stations along principal component axis II in
Figure 60. This suggests that Station 44 is better Integra: "d with the rest
169
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of the Bay than is Station 34, an attractive interpretation because Station 44
is not as uell protected from offshore Bay waters as is StEtion 34. Wild Fowl
Bay is encompassed by extensive cattail beds, by Sand Point, and by Katechay
and Stony Islands. These results imply that elevated cell densities nearshore
at the Bay-Lake interface, specifically Station 53, may also occasionally be
due to local factors such as runoff and/or nutrient flux from the sediments.
At the very least, it may be difficult to distinguish betwen Saginaw River
input and nearshore effects on algal transport into Lake Huron.
Application of water quality models require spatial resolution of the
Bay. Present divisions of the Bay separate the inner Bay from the outer Bay
along a line perpendicular to the Bay long axis (Bratzel e£ al. 1977; Bierman
and Dolan 1981). We have some remarks about this division which we do not
intend as a criticism. Indei ! , model output based on the present divisions
seems to fit quite well the actual data previously available for Saginaw Bay
(Bierman and Dolan 1981). We only wish to note an apparent phenomenon which
occurred in Lhe 1980 data. This may be of interest should steps be taken in
tne future to refine spaH il ispects of Saginaw Bay models.
: ti ytoplankton ' jta suggest 2 distinct regions of the Bay, the inner Bay
(Region A Figure SK) and the cuter Bay (Regions Bj-B^ of Figure 58). Note
that a line separating the two regions would be at an angle approximately 45°
tn the long :;is of the Bay. As discussed previously, two stations (34 and
44) belong to neither region, and apparently are not easily integrated with
the rest of the Bay. The question that remains is why should the inner and
outer Bay be separated at a 45° angle to the Bay long axis? Recall that the
Rlver-i.iner Bay area retains some Integrity on the average. Without Lake
Huron influence, the River-inner Bay community might well develop along a
170
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front perpendicular to the Bay's ' ong axis. However, Lake Huron water enters
along the west shore and appirently either deflects the River water mass or
mixes with River water in the region north of the River.
The fact Lin:: ^ar pattern of phytoplankton response to average
physical conditions and loading sources to the Bay is an indication of return
to a more ecologically stable condition. In a previous study we (Stoermer
et aK in press) found that large blooms of phytoplankton occurred throughout
the lower bay, often without obvious correlation to known loading sources.
This s'tuation apparently resulted fron overloading of phosphorus to the most
directly affected parts of the system. Vollenweider e£ a_l. (1974) concluded
that waters in the inner regions of Saginaw Bay were not nutrient limited, and
that variations in phytoplankton production resulted mainly from transient,
local meteorological conditions regulating light flux and the sinking velocity
of algal populations. Phosphorus overload was also demonstrated by luxury
consumption of phosphorus by many llgal populations occurring in the Bay
during the 1974-1976 period and the transport of phosphorus in the form of
polyphosphate bodies out of the Bay to the open waters of Lake Huron (Stoerner
ill* 19^0). Unfortunately the direct studies of phosphorus assimilation
wfre not repeated during the current study, but the fact that polyphosphate
bodies are not apparent in cells, as they were previously, and that algal
populations appear to show a direct response to loading sources argues that
the previous conditions :;f overload have been mitigated. This should result
in a reduction of phosphorus transport to Lake Huron over and above that
achieved directly from loading reductions to the Bay, since it Is now
reasonable to expect that phosphorus entering the Bay will be metabolical1v
processed within the Bay and, as a consequence, subject to normal loss Herms.
171
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Tho effects of phosphorus loading reductions are also evident in
qualitative changes in the phytoplankton flora of Saginaw Bay. The most
obvious of these is reduction in the abundance and range of distribution of
manv of the larger species of blue-green algae which form objectionable
blooms. These populations had previously been implicated in the production of
taste and odor nuisances at water filtration facilities which draw their
supplies from Siginav. Bay (Bratzel c£ a]_. 1977). Equally striking is the
virtual elimination of certain diatom populations which, because of their
large size, had been a dominant element of phytoplankrbiomass in the Cay.
As an example, Actinocyclus normanii fo. subsalsa was found at a limited
number of stations and always at low abundance during this study whereas it
had been a subdominant previously. This species has been documented to
increase dramatically in areas of th • it- Lakes which are grossly outroohi^d
(Hohn 196?) and is considered to be an indicator or gross eutrcphication in
the Great Lakes system. Similar, although rot so dramatic, reductions were
noted in the abundance and distr bution of other diatom species which have
been noted to occur under grossly polluted conditions, such as Skeletonema
spp., Thalasslosira spp., Stephanoriiscus binderanus, and S. tenuis.
One of the un.isual aspects of the phytoplankton flora of Saginaw Bay
prior to nutrient load lag reductions was the abundance of many large-celled
diatom species, which are usually restricted to benthic habitats, in the
Dlankton. Included in this group were s"veral species of Surlrellg,
Cymatopleura, and large, betithic species of the genus Nitzschla. During the
1974-1976 study it appeared that the levels of nutrient enrichment in Saginaw
Bay allowed these populations, which are usually restricted to the nutrient-
rich environment of the sediment-water Interface, to successfully exist in
172
-------
pla.ikt.on assemblages. Although these populations were not present in great
numerical abundance, they contributed significantly to the total cell volume
of assemblages in Saginaw Bay. Invasion of the plankton by normally benthic
populations under conditions of high nutrient loading seems to >>e a
peculiar - .ty of the Laurentian Great Lakes (Stoermer e£ ill 974, Holland and
Claflin 197 5, Stoermer and Stevenson 1980). The only similar situation occurs
in the African Rift Lakes, where large species of Surirella are common in the
plankton (Hustedl 1949). Such populations were only a very minor component of
phytoplankton assemblages sampled during 1980.
Conversely, some populations have increased in abundance in Saginaw Bay.
The greatest relative change in abundance is found in some of the smaller
species of Cyclotella which are usually components of the summer flora of
relatively undisturbed regions for the Laurentian Great Lakes (Stoermer 1978).
These species have both Increased In abundance and become nore widely
distributed in Saginaw Bay. Within this group, C. comensi s is numerically
most important (Figure 21). This species has only recently become an
important clement of the phytoplankton flora in the Great Lakes. Prior to
1970 it was occasionally found in samples from offshore stations in the upper
Great Lakes, hut rarely in significant abundance. Since that time it has
become a major dominant in the offshore flora of Lake Huron (Stoemer and
Kreis 1980) and Lake Michigan (:>chelsk^ ir ' Stoermer in publication).
Although it is apparently toleraT of a ertain degree of nutrient enrichment,
and forms atypical summer blooms in the nearshore waters of Lake Huron (Lowe
1976), this species has not been reported from l^ake Erie, Lake Ontario, or
other grossly disturbed regions of the Great Lakes. In Lake Huron it appears
to be particularly efficient at uptake of silica, and usually occurs at
173
-------
stations having relatively high nitrate concentrations (Stoerraer and Krels
!980). It was previously excluded from lower Saginaw Bay, but is an importaat
element of assemblages collected in 1980. Species of Cyclotella which are
less tolerant of eutrophication such as C. comta and C. ocellata (Stoermer
1978) have increased in abundance in Saginaw Bay, although their distribution
is stll large', *" -trlcted to stations in the outer Bay.
This shifc 'o increased abundance of small-celled species of diatoms is
indicat w < i genoral trend toward cells of much less average volume
dominating the flora of the Bay. This occurs both through the replacement of
larger-celled species by those with smaller average dimensions and through a
reduction in the average cell size of eurytoplc populations which have
remained abundant in the Bay through the period covered by both studies.
Since even a small reduction in principle dimensions result^ in a large
reduction in calculated biovolume, the reduction in blovolume of phytoplankton
assemblages in the Bay has decreased even more dramatically than have
phytoplankton numbers. This change to -smaller species probably signals more
rapid cycling of nutrient pools in the Bay. Mthough they wore not routinely
enumerated because of the requirement for specialized techniques, many samples
collected during 1980 contained large numbers of plco-plankton organisms. As
is the case in many areas of the oceans, some areas of the Groat Lakes are
relatively rich in both prokaryotic and eukaryotic photosynthetic organisms in
the less than 1 m size range. Although this component of che biota In 'lit
Great Lakes has not been well studied, our limited observations suggest that
they become most abundant H-iring periods of transition between one nutrient
cycling regime and another. An xample would he nutrient resupply during the
fall mixing period 'n the upper lakes. It Is possible that t^e relative
-------
abundance of such populations tn Saginaw Bay reflects the fact that conditions
in the Bay art- still changing rapidly and the waters of the Bay are undergoing
a continuing transition of nutrient regimes. On the basis of our results we
consider it likely that rhe phytoplenkton flora of Saginaw Bay will continue
to undergo qualitative and quantitative changes even if nutrient loadings are
stabili. d at the 1980 levels.
The fact that the seasonal succession of phytoplankton in Saginaw Bay was
unusual for a temperate water body during 1980 may be another manifestation of
this continuing instability. The major departure from previous conditions
noted in the 1980 samples is the virtual absence of a spring bloom. In the
previous years studied there was a large spring bloon dominated by large
species of Stephanodiscus and other populations such as Fragilaria capucina.
During 1980 this soring diatom bloom did not develop and the large biomass
contribution, particularly by the large species of Stephanodiscus was lacking.
Instead, all of the major phytoplankton groups, including diatomr, underwent a
continued increase to a seasonal maximum relatively late in the year, then
declined during the late fall period to a greater or lesser extent. The
reason for this drastic change in succession.il pattern is .lot apparent.
Nutrient loading measurements made concurrently with this study did not reveal
any particularly unusual t. ^s , although spring loadings to the Bay wt re
slightly less than the projected trend (David Dolan, personal communication).
Since there are numerous instances of large year to year variations in
seasonal succession pat'ems in eutrophied regions of the Great Lakes (e.g.
Chandler and Weeks 1*45, Stoermer e^ a^. 1974, Nichols e£ aK 1980, Danforth
and Ginsberg 1980), It would be useful to determine the necharlsm or
mechanisms which can .- these excursions from the long-ten average i ise.
175
-------
Although the dat.: presently available to us ' ¦» not allow a complete analysis,
there are plausible mechanisms which could explain the observations and which
should be further investigated. The most obvious of these is grazing and
consequent modification of nutrient i ycle rates. The depressed component of
the ohytoplani on are diatoms and flagellates which may be grazed most
efficiently. It is possible that grazing pressure in the early spring
depressed population levels of these species early in the spring and that the
recycled nutrients were eventually sequestered by less efficiently grazed
green and blue-green species as the season progressed. An alternate
hypothesis is that late-season populations were supported by nutrient?
released from the sedinents during the summer. I; is possible that both of
these mechanisms were operating in 1980 and that there will be a prolonged
period of instability until the e osystem of the Bay adjusts to its new
loading regime. This situation is most interesting because most of our
examples ot population and seasonal succession modification in the Great Lakes
come from areas which have been subjected to increased nutrient loadings. It
is becoming apparent that reductions i.i ..utrient loading resul * in equally
dramatic changes in species composition and succession but that these changes
are net simply a return to previous conditions. An example of this is the
apparent continued increase of blue-green algae in Lake Michigan despite
reductions in phosphorus loading (Ayers 1973, Danforth and Ginsberg 1980,
Ayers and Feldt 1982).
Lake Huron differs from the Lake Michigan case in that it has not
progressed as far in eutrophiration and in that such a high relative
proportion of loadings come from Saginaw Bay and are biologically processed
within the Bay. At this point it is clear that the direct contribution of
176
-------
outrophication tolerant phytoplankton populations from Saginaw Bay to Lakpulations
beyond the Bay could expected (Cruise 84, Figure 63; Cruise ''0, Figure 67).
In all other cases the outer line of stations had assemblages similar to each
other and closely related to assemblages in the open lake. In the two cases
where transport was apparent, only Station 53 had assemblages siiilar to.inner
Bay stations, which indicates that transport was restricted to nearshore
drift. Thus it is quite clear from our results that the direct effects of
phosphorus stimulated phytoplankton overproduction on the rest of the Lake
Huron ecosystem have been substantially mitigated. Thf- ¦ are still cases
whore populations generated in Saginaw Bay are transported out of the Bay
proper, but it is highly doubtful that the extensive iniection o:
eutrop'nication tolerant populations which occurred under previous conditions
(Schelske jet ^1_. 1974, Stoermer and Kreis 1980) occurs today.
Despite the fact that our results show that there has been substantial
water quality improvement in Saginaw Bay, it should be pointed out that some
significant problems still remain. In general, the phytoplankton flo of the
Bay 'ill contains many populations which are characteristic of eutrophic or
disturbed conditions. The seasonal cycle of total phytoplankton abundance
(Figure 2) and major physiological group dominance (Figure 3) remains more
177
-------
typical of a hypereutrophic system than of one which is balanced and
efficiently productive. As mentioned previously, this may indicate that
Saginaw Bay has not yet reached a stable equilibrium with ts present
loadings, but the conservative conclusion from our results would be that
additional loading reductions will be necessary to return the Bay to the most
desirable condition.
Results of summary analysis of phytoplankton community structure over the
period of this study (Figures 58, 59, 60, and bi) show the direction and
extent of perturbation of the phytoplankton community at the stations sampled.
As would be expected, Station 54 is a clear outlier. This station is located
in the Saginaw River and is only moderately and periodically influenced by
conditions in the rest of the Bay. During all s.impling periods this statio:
was dominated by phytoplankton populations which cha-ncteristically develop
under highly disturbed conditions. It is also obvious that this source quite
strongly affects a number of stations in the southern Bay (Group A,
Figure 58). The phytoplankton flora at these stations is dominated by a
mixture of populations derived from the river, eutrophication tolerant lak»
popalations which apparently develop within the region, and some eurytopic
populations which also occur at less affected stations.
The great departure of Station 34 and, to a somewhat lesser extent,
Station 44 from the flora of the rest of the Bay is perhaps the most
interesting result of this study. As will be noted from Figures 60 and 61,
these stations differ as much in average phytoplankton composition from the
rest of the Bay as Station 54 does. The flora of this area, particularly late
in t'ie season, is strongly dominated by blue-green algae and this is the
remaining area of the bay where nuisance producing blue-green blooms might be
178
-------
expected Co develop. Certain aspects of the phytoplankton flora of this
region are highly unusual. For instance, these stations support large blooms
of the atypical prokaryote Pelonema sp. This organism is apparently
achlorotic and most of its close relatives are usually found in highly
organically enriched, oxygen depleted environments. Pelonema itself has been
reported from the plankton of organically enriched lakes where oxygen
depletion is not complete (Huber-Pestalozzi 1938). The unique flora of this
region of the Saginaw Bay coast leads us to the conclusion that the
combinaHon of restricted circulation, loadings transported from the "outhern
part of the Bay, and likely local sourr»s of both nutrient and organic
loadings severely effect this region. Unfortunately there is not sufficient
information to further analyze this situation.
The rest of the station sampled during this study form an orderly
progression trom stations with fairly high populations of species tolerant of
eutrophic conditions in the southern part of the Bay (Region Bj, Figure 58) to
typically oligotrophia populations in the outer Bay Stations. As noted
previously, the degree of modif imr ion of the phytoplankton flora is skewed by
transport of loadings from the southern Bay by the average circulation
pattern. It needs to be emphasized that there are considerable differences
between these regions. Although thcoe stations and regions appear to be
closely clustered in the figures r>ser>ted, it must be remembered that these
analytical techniques scale themselves to the greatest differences in the data
set under analysis. In 1 lis case the scale of difference is determined by the
extremely modified and atypical floras generated at Stations 34 and 5'-t.
Although the differences between Regions Bj and B3 are small in comparisor,
they are still significant. To place some perspective on this, although we do
179
-------
not have sufficient data to supnort a quantitative evaluation, it is almost
certainly true that the differences between Region Bj and B3 are much larger
than between Region B3 and any other definable region of Lake Huron. In
different terms, most phycologists would classify the flora of Region Bj as
characteristic of eutrophic environments r.he f 101 . <• r.oi?ic . f.ore
characteristic of oligotrophic enviror
All of this points out thciL fhe S.. w 'J iy rnp . - '-aM., c> - i r
laboratory in which to study the f mfc. «- i. i -- , r> j s a
beyond. It is q'ite apparent ti 'ui.' r.l i - . i ¦ =~rae ->f (.¦•'. ,1 ¦
and pervasive problems of the syr.l . 11 ac laice int source phos>lio;u~
pollution, effective menagement •? -s '¦ . . f eveloped ri
with local specific problems ami ' ¦ « ;¦ e. Reco. . -sidle
(Frederick 1981, Harris and Vol I ' ' 'f *: :-d oroinat> mr
indicate that although nutrie- ¦ «it.»?.ic;s h.i»- ' i- • <-of-
in reducing 1 .oSS ecological i" i>.3, 1 ..'nth • i .1 . .si--ct.-ndir.
system processes and 1 r,,c e t -ou^h't ' -• ma
will be necessary t>. rec.i'-n the Great Lakes •- > < - "i > •' r- native, • .•
than merely tolerable, condition. Ou'" study ' : : pre 1. •:
generation of control measures have begun rJ re h>;p .. 1 •'") vr histc »
ecosystem degradation ' Saginaw Bay. Given the , t-f <
conditions present in the «ystem, the known loading charac»•] :;ti..= , > i : .1
-------
RECOMMENDATIONS
1. The Wild Fowl Bay region of Saginaw Bay still shows evidence of
excessive nutrient loading. Further study should be devoted to this specific
region to determine causes of potentially nuisance producing algal blooms.
2. There is substantial evidence that the Saginaw Bay system is still in
a transitional state in regards to its response to nutrient loading reduction.
Further studies should be conducted to develop a quantitative understanding of
processes in ecosystem rehabilitation.
3. Distribution of ecological effects in Saginaw Bay is strongly de-
pendent upon advective transport on both instantaneous and time-averaged
scales. These parameters be included in "iodel segmentation schemes.
A. Our study suggests that there is a step-wise rather than a continuous
succession of effects of nutrient loading on phytoplankton species
composition. Future research should be devoted to determination of the
specific points at which major perturbations occur.
5. Our data suggests that one of the important characteristics in phyto-
plankton assemblages under recovery conditions is a change from relatively
large celled populations to those with less volume per cell. The implications
of this for higher levels of the food chain should be investigated.
6. Our study indicates that reduction in nutrient loading does not
necessarily result in the phytoplankton flora returning to pre-eutrophication
condition. In Saginaw Bay It Is evident that many of the taxa now present
were not part of the original flora of the bay. The Implications', of this
modified succession should be lurther investigated.
181
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, et al. (in prep.) Model rrinarisons of thv' Saginaw Bay phyto-
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Kr ml er i ck , V. K. 1 981. Preliminary investigation of tin* alg.il flora in the
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185
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APPENDIX 1. SUMMARY OF PHYTJPLANKTON OCCURRENCE IN THE
NEAR-SURFACE WATERS OF SAGINAW BAY DURING THE FIELD SEASON OF I98O
number average
slides density 6 % pop.
Undetermined flagellates
Undetermined colony spp.
2
0.080
0.001
Undetermined cyst
1
0.016
0.000
Undetermined flagellate sp. #10
180
*~2.606
0.957
Undetermined flagellate sp. #11
10
0.16U
0.003
Undetermined flagellate sp. #12
107
6.8^5
0. 18*4
Undetermined flagellate sp. #13
1U0
8.72*4
0.200
Undetermined flagellate sp. #1*4
21
0.1*62
0.01*4
Undetermined flagellate sp. #6
1*4
0-397
0.013
Undetermined flagellate so. #7
1
0.008
0.000
Unoetermined flagellate sp. #8
2
0.5^8
0.009
Undetermined flagellate sp. #9
23
1 . U2
0.026
Undetermined c!age'late spp.
269
2^9-9^5
3.857
total unoetermined ( 12 categories)
310.937
5-26*4
Cyanophyta
Aqmenellum quadruplicatum (Meneqh.) Br£b.
21
60.3^3
0.176
Aqmenellum spp.
U
6.63**
0.022
Anabaena catenula var. intermedia Griffiths
9
3-517
0.015
Anabaena flos-aquae (Lynqb.) Brfeb.
88
7*4.388
0.870
Anabaena spp.
13
1*4.086
0.0*46
Anabaena subcy1indrica Borqe
3
3-239
0.022
Anacystis cyanea (KUtz.) Dr. 6 Dai ley
130
629.539
2.392
Anacystis incerta (Lemm.) Dr. £, Dai ley
168
1639.*403
8.061
Anacys ti s spp.
k
2. / 77
0.012
Anacystis thermalis (Meneqh.) Dr. 6 Dai ley
118
53.153
0.5W
Aphanizomenon qracile Lemm.
50
660.3*43
1.080
Chamaesiphon spp.
1
0.016
0.000
Coe1osphaerium spp.
2
0.227
0.002
Dacty1ococcopsis acicularis Lemm.
1
0.130
0.001
Dacty1ococcopsis rhaphidi0ides Hansq.
1
0.^5*4
0.002
Dactylococcopsis smithii Chod. & Chod.
¦>
0.285
0.005
Gomphosphaeria aponina KUtz.
9. *400
0.109
Gomphospnaeria lacustris Chod.
128
952.393
5.68*4
Gomphosphaeria wichurai (Hilse) Dr. & Dai ley
25
99.325
0.*»19
Lynqbya birgoi G. M. Smith
2
3.8*42
0.016
Microcoleus lynqbyaceus (KUtz.) Crouan
8
U.819
0.069
Microcoleus vaqinatus (Vauch.) Gom.
28
17-375
0.59&
Oscillatoria bornetii (Zuk.) Forti
k
3-908
0.137
-------
APPENDIX 1. (continued)
number average
slides density 6 % pop.
Oscillatoria limnetica Lemm.
17
115-260
O.271
Osc ilia tor i a 1utea Aq.
3
10.197
0.068
Osc i 1 1 ator i a retz i i Aq .
34
172.585
0.591
Osc i 1'ator i a spp.
28
51.803
0.195
Pelonema spp.
54
1177.82-U
1
Plectonema spp.
l
0.779
0.002
Porphyrosiphon spp.
20
52.039
0.165
Raphidiopsis curvata Fritsch I Rich
3
5-904
0.012
Schizothrix calcicola (Aq.) Gom.
99
1*4.215
0. 1/3
Schizothrix spp.
2
5-353
0.015
Undetermined blue-green colony
1
2.076
0.013
Undetermined blue-green filament sp.
#\
13
275.774
0.156
Undetermined blue-green filament sp.
#h
?5
365.789
0.308
Undetermined blue-green filament
43
119.2 16
0.365
total blue-green ( 37 categories)
6652.375
24.104
Chiorophyta
Act
nastrum nantzschii \-ar. fluviatile
Schroed.
5
5-737
0.021
Ank
strodesmus fusiformis Corda
25
2.417
0.027
Ank
strodesmus qelifactum (Chod.) Bourr
51
2.898
0.040
Ank
strodesmus qracilis (Reinsch) Kors.
121
H.536
0.113
Ank
strodesmus nannosel?ne Skuia
2
0.031
0.000
Ank
strodesmus setiaerus (Schroed.) G.
S. West
165
1 1.923
0.231
Ank
strodesmus spp.
77
6.053
0.068
Arthrodesmus spp.
1
0.065
0.000
Botryococcus braunii KUtz.
1
0.649
0.005
Characium spp.
1
0.016
0.000
Ch1amydomonas spp.
3
0.064
0.003
Chodatella ciliata (Lao.) Choa.
60
23.817
0.222
Chodatella citr^'ormis Snow
6
0.514
0.004
Chodatella guaariseta (Lemm.) G» M. Smi
th
120
69.771
0.422
Chodatella spp.
2
0.093
0.002
Chodatella subsalsa Lemm.
72
9.882
0.076
C1osteriopsis spp.
1 1
0.7C2
0.003
Closterium aciculare T. West
30
0.768
0.007
Closterium moniliferum (Bory) Ehrenb.
1
0.016
0.000
Closterium spp.
15
1.095
0.005
Coelastrum cambricum Archer
8
3-392
0.037
Coelastrum microporum Naeq.
152
219.991
1 .220
Coelastrum proboscideum Bohlin
2
1.604
0.017
Coelastrum reticulatum (Danq.) Senn
17
U.233
0. 120
Coelastrum spp.
12
18.359
0.138
187
-------
I
APPENDIX 1. (continued).
number average
s1i des
dens i ty I
% pop.
Cosm;-ium anqulosur.i Brfeb.
137
20.019
0.105
Cosmarium bioculatum Brfeb.
6
0. 132
0.003
Cosmarium depressum var. planctonicum Rev.
9
0.151
0.002
Cosmarium qeometricum var. suecicum Borae
Q
>
0.311
0.005
Cosmarium spp.
66
2. }k0
0.029
Cruciqenia irregularis Wille
3
O.589
0.002
Cruciqenia quadrata Morren
57
19.670
0.225
Cruciqenia rectanqu1aris (A. Braun) Gay
8
5-^70
0.028
Cruciqenia spp.
9
1.112
0.013
Cruciqenia tetrapedia (Kirch.) West 6 West
63
27-9^0
0. 106
Cruciqenia truncata G. M. Smith
16
13.032
0.039
DictvosDhaeriurn ehrenberqianum Naeq.
52
33 - " 10
0.139
Dictyosphaerium pulchellum Wood
7
5-756
0.03"
Dictyosphaeriurn spp.
6
0.502
0.013
Dimorphococcus tunatus A. Braun
1
0.195
0.002
Elakatothrix qelatinosa Wille
7
0.3^5
0.002
Elakatothrix spp.
1
0.260
0.001
Elakatothrix viridis (Snow) Printz
1
0.195
0.000
Eutetramorus spp.
35
3.9H
0.107
Franceia droescheri (Lemm.) G. M. Smith
22
O.856
0.010
Franceia oval is (France) Lemm.
1
0.031
0.000
Gloeocystis planctonica (West & West) Lemm.
U5
116.2^8
0.693
Gloeocystis spp.
62
39.872
0.643
Gloeocystis vesiculosa Naeq.
1
0.273
0.003
Gloectila pelaoica (Nyq.) Skuia
31
239.731
0.463
G1oeot i1 a spp.
i:
4 1 .296
0.091
Golenkinia radiata (Chod.) Wille
l
C.065
0.000
Hormidium tribonematoideum Skuia
1+0
10.5^5
0.057
Kirchnerie11 a contorta (Scnmidle) Bolin
33
6.60'4
0.028
K i r chner i e 1 1 a lunaris (K i i ii.) Hoebius
33
6.605
0.037
Kirchneriella lunaris var. d:anae Bohlin
]U
b . 683
0.022
Kirchnerie11 a lunaris var. irregularis
G . M. Sm i th
h8
U.9514
0.052
Kirchneriella obesa (W. West) Schmidle
12
1-27^
0.009
Kirchneriella obesa var. aperta (Teil.)
Brunntha1er
11
1.635
0.007
Kirchneriella obesa var. major (Bernard)
G . M. Sm i th
3
0.38*4
0.002
K i --chner i e 1 1 a spp.
'3*
30.665
0.268
Kirchneriella subsol i *:ar i a G. S. West
6
0.281
o.ooi*
Laqerheimia qenevensis Chod.
l
0.065
0.001
Lobocystis dichotoma Thompson
20
6.1*52
0.029
Monoraphidium contortum (Thur.) Kom.-Leq.
10
0.801
0.003
Monoraphidium irregulare (G. M. Smith) Kom.-Leq.
36
2.795
0.021
188
-------
APPENDIX 1. (continued).
number average
s 1 i des
dens i ty I
% pop.
Monoraphidium saxatile Kom.-Leq.
2
0.016
0.001
Monoraphidium setiforme (Nyq.) Kom.-Leq.
9
2.903
0.018
Monoraphidium spp.
27
2.262
0.017
Monoraph i q i um tortile (West I West) Kon-i.-Leq.
12
1 .254
0.007
Mougeotia spp.
91
38.179
0. 131
Nephrocytium aqardh i anun. Naeq.
8
0.841
0.018
Nephrocytium limneticum (G. M. Smith)
G. M. Smi th
5
4.755
0.012
Nephrocytium spp.
iO
0. J73
0.010
Oocystis parva West 6 West
1
0.584
0.004
Oocyst i s spp.
228
168.246
1 .252
Pediastrum biradiatum Meyen
25
14.973
0.075
Pediastrum boryanum (Turp.) Meneq.i.
86
74.036
0.461
Pediastrum duplex Meyen
27
26.617
0.129
Pediastrum duplex var. clathratum
(A. Braun) Lac.
4
3.989
0.031
Pediastrum duplex var. cohaerens Bohlin
16
16.519
0.083
Pediastrum duplex var. qracilimum West 6 West
17
13-462
0.054
Pediastrum duplex var. ruqulosum Raciborski
5
2.650
0.013
Pediastrum duplex var. reticulatum Laq.
3
3.086
0.022
Pediastrum simplex var. duodenarium
(Ba i I .) Rabh .
54
30.780
0.163
Pediastrum simplex (Meyen) Lemm.
3
0.908
0.C 3
Pediastrum spp.
30
8.285
O.O38
Pediastrum tetras (Ehrenb.) Ralfs
80
31 - 3^8
0. 180
Ped'lomonas m:nuta Skula
i
C.O65
0.000
Phacotus lenticularis (Ehrenb.) Stein
15
1.327
0.005
P1anktosphaeria qelatinosa G. M. Smith
1
0.125
0.001
Quadriqula c1osterioides (Bohlin) Print2
l
0.031
0.001
Ouadriqula lacustris (Chod.) G. M. Smith
l
0.062
0.001
Scenedesmus acuminatus (Laq.) Chod.
K1
118.480
0.473
Scenedesmus acutiformis Schroed.
119
288.034
1.358
Scenedesmus acutus Meyen
4
1.570
0.007
Scenedesmus anomalus var. acaudatus Hortob.
4
2.754
0.008
Scenedesmus anomalus (G. M. Smith) Tiff.
3
0.454
0.002
Scenedesmus arcuatus Lemm.
12
2.873
0.018
Scenedesmus armatus Chod.
46
17.968
0.118
Scenedesmus armatus var. boqlariensis Hortob.
104
73-816
0.391
Scenedesmus bicaudatus (Hansq.) Chod.
13
2.299
0.015
Scenedesmus bicellularis Chod.
105
28.562
0.178
Scenedesmus bijuga (Turp.) Laq.
1
0.125
0.002
Scenedesmus brevispina (G. M. Smith) Chod.
1
0.130
0.000
Scenedesmus carinatus (Lemm.) Chod.
121
96.349
0.509
189
-------
APPENDIX 1. (continued)
average
ns i ty & % pop.
Scenedesmus circumfusus var. bicaudatus
fo. qranulatus Hortob.
Scenedesmus decorus var. bicaudato-aranu1atus
sOl3-73J»
0.074
(Hortob.) Uherk.
89
81 .bi'O
0.297
Scenedesmus denticulatus var. linearis fo.
costato-qranu1atus (Hortob.) Uherk.
37
11*. 544
0.087
Scenedesmus denticulatus var. linearis V'^sr.
64
29.076
0.152
Scenedesmus denticulatus Lag.
2
0.285
0.003
Scenedesmus dispar Br6b.
5
0.7U
0.002
Scenedesmus ecornis (Ralfs) Chod.
9
2.998
0.007
Scenedesmus ecornis var. disci formic Chod.
6
1.774
0.006
Scenedesmus flexuosus (Lemm.) Ahl.cirom
16
4.927
0.025
Scenedesmus granuiatus West & \vest
46
24.375
0.084
Scenedesmus >ntemedius Chod.
50
16.618
0.076
Scenedesmus lefevrii var. semi <,erratus Uherk.
98
40.781
0.209
Scenedesmus lefevrii Defl.
116
58.380
0.304
Scenedesmus quadricauda Chod.
198
I5O.869
0.929
Scenedesmus quadricauda var. biornatus Kiss
6
0.359
0.005
Scenedesmus quadricauda var. lonqispina
(Chod.) G. M. Smith
5
1.055
0.008
Scenedesmus quadricauda var. maximus
West & West
24
4.199
0.020
Scenedesmus quadricauda var. quadrispina
(Chod.) G. M. Smi th
1
0.031
0.001
Scenedesmus quadricauda var.?
1
0.031
0.000
Scenedesmus semicristatus Uherk.
7
1 .200
0.008
Scenedesmus serracus (Corda) Bohlin
40
6.331
0.030
Scenedesmus spinosus Chod.
219
253.598
1.394
Scenedesmus spp.
214
162.148
1 .075
Schroederia spp.
1
0.0C8
0.000
Selenastrum bibraianum Reinsch
/»
0
1.614
0.008
Selenastrum qracile Reinsch
1
0.260
0.002
Selenastrum minutum (Naeq.) Collins
1
0.031
0.000
Selenastrum spp.
14
2.58/
0.010
Sphaerocystis schroeteri Chod.
1
0.062
0.003
Sphaerozosma granulatum Roy & Bissett
3
1.557
0.002
Sphaerozosmaspp.
1
0.093
0.001
Spondylosium planum (Wolle) West 6 West
1
0.358
0.004
Staurastrum paradoxum Meyen
17
0.536
0.005
Staurastrum spp.
1.1
2.228
0.011
Tetraedron caudatum (Corda) Hansq.
80
4.603
0.021
Tetraedron minimum (A. Braun) Hansg.
167
24.357
0.145
Tetraedron muticum (A. Braun) Hansq.
8
0.328
0.002
Tetraedron requlare KUtz.
4
0. 120
0.001
190
-------
APPENDIX 1. (continued)
number average
slides density 6 % pop.
Tetraedron spp.
17
0.797
0.006
Tetraedron triqonum (Naeq.) Hansq.
3
0.161
0.001
Tetrastrum qlabrum (Roll) Ahl. S Tiff.
90
11.81*0
0.172
Tetrastrum heteracar,thum (Nord.) Chod.
1
0.062
0.001
Tetrastrum spp.
1
0.031
0.002
Tetrastrum stauroqeniaeforme (Schroed.) Lemm.
^5
9-^70
0.045
Ulothrix amphiqranu1ata Skuja
1
0.1 i*0
0.001
Ulothrix spp.
25
3-33^
0.046
Ulothrix subtilissima Rabh.
4
0.358
0.012
Undetermined green colonies
178
325.637
1 .5^2
Undetermined green colony sp. #19
6
2.1*76
0.010
Undetermined green filament
1
0.343
0.006
Undetermined green filament #5
24
15-193
0. 168
Undetermined qreen filaments
12
3.227
0.019
Undetermined qreen individual
265
248. 446
1 .921
total green ( 1 GO categories)
3698.2l»6
20.847
Bac i11ar i ophyta
Achnanthes affinis Grun.
9
0.182
c.003
Achnanthes biaso1ettiana (KUtz.) Grun.
I
0.039
0.002
Achnanthes clevei Grun.
2
0.016
0.001
Achnanthes clevei var. rostraia Hust.
1
O.O65
0.000
Achnanthes exiqua Grun.
2
0.016
0.000
Achnanthes lanceolata (Br6b) Grun.
2
0.073
0.001
Achnanthes lanceolata var. dubia Grun.
2
0.073
0.001
Achnanthes lanceolata var. elliptica CI.
*
0.008
0.000
Achnanthes lanceolata var. omissa Reim.
0.008
0.000
Achnanthes lanceolata var. ninckei
(Guerm. 6 Mang.) Reim.
5
0.086
0.003
Achnanthes lapponica Hust.
1
0.008
0.000
Achnanthes 1auenburqiana Hust.
1
0.016
0.000
Achnanthes lemmermanni Hust.
2
0.073
0.001
Achnanthes linearis (W. Smith) Grun.
2
0.016
0.000
Achnanthes linearis fo. curta H. L. Smith
1
0.016
0.001
Achnanthes microcephala (KUtz.) Grun.
1
0.008
0.000
Achnanthes minutissima var. cryptocepha1 a KUtz.
20
0.711
0.016
Achnanthes minutissima Grun.
*~3
1.213
0.034
Achnanthes sp. #1
l
0.016
0.000
Achnanthes sp. #10
l
0.008
0.000
Achnanthes sp. #12
1
0.008
0.000
Achnanthes spp.
32
0.879
0.015
191
-------
APPENDIX 1. (rontinued)
Act i nocyc1 us norman i i fo. subsaIsa
(Juh1in-Dannfe1t) Hust.
Amph i pleura pe1 1 uc i da (KUtz.) KUtz.
Ampho'-a ova 1 i s var . af f i n i s (KUtz.) V. H.
Amphora ova 1i s var. ped i cu1 us (KUt2.) V. H.
Amphora ovg i s (KUtz.) KUtz.
Amphora perpus ilia Grun.
Amphora s i ber i ca Skv. £ Meyer
Amphora spp.
Amphora subcostulata Stoermer £ Yc.ng
Amphora thumens i s (Mayer) A. Cl.-E.
Anomoeone i s spp.
Anomoeone I s vi trea (Grun.) Rose
Aster i one 11 a formosa Hass.
Coccone i s d i m i nut? Pant.
Coccone i s ped icu1 us Ehrenb.
Coccone i s piacentula var. euq1vpta
(Ehrenb.) C1 .
Coccone i s p1acentu1 a var. 1ineata
(Ehrenb.N V. H.
Cocconei s .p. #2
Cocconei s spp.
Cyclotel1 a ant i qua W. Smith
Cyc1ote1 la atomus Hust.
Cyc 1 ote 1 la ccmens i s G-'un.
Cvc 1 ote 1 la com'.a (Ehrenb.) KUtz.
Cyc1ote1 la crypt ica Re i mann, Lew i n £ Gu i i1ard
Cyclotella kutz i nqi ana Thwaites
Cyc1ote11 a meneqh i n i ana KUtz.
Cyc1ote1 a mi ch i qan i ana Skv.
Cyclotel a oce11ata Pant.
Cyc1ote11 a operculata (Ag.) KUtz.
Cyclotel1 a pseudoste11i qera Hust.
CycIote11 a sp. #6
Cyc1ote11 a sp. auxospore
Cyc1ote11 a spp.
Cyc1otella stelIiqera (CI. £ Grun.) V. H.
Cyc1ote11 a stel 1 iqera auxospore
Cymatopleura el 1 i p t i ca (Brib £ Godey) W. Smith
Cymatopleura solea (Br6b £ Godey) W. Smith
Cymbe11 a c i stu1 a (Ehrenb.) Kirch.
Cymbe1 I a i naequa1i s Ross
Cymbe11 a microcepha1 a Grun.
Cymbe1 la mi nuta Hilse
number average
slides density £ % pop.
48
6.891
0.029
6
0.055
0.002
2
0.^24
0.001
18
0.605
0.009
7
0.095
0.002
42
1 .662
0.026
1
0.065
0.001
15
0.538
0.006
l
0.008
0.000
1
0.016
0.001
1
0.023
0.000
3
0.031
0.001
178
42.233
1 .022
1
0.016
0.000
1
0.008
0.000
2
0.016
0.001
1
O.O65
0.000
6
0.127
0.002
1
0.016
0.001
2
0.023
0.000
3^
36.952
0.158
252
S17.C17
10.71c
72
2.611
0.065
6
1 .5JU8
0.007
8
0.070
0.002
66
131 -049
0.44b
'¦*7
l .068
0.027
10
5.717
0.246
t
0.103
0.003
117
38 .604
0.248
2
0.319
0.008
29
0.393
0.01 1
21
l -?i.7
0.015
122
8.224
0.247
1
0.008
0.000
7
0.192
0.001
16
0.227
0.006
1
0.008
0.000
1
0.016
0.000
59
1.462
0.040
7
0.17*
0.003
192
-------
APPENDIX ' . (fjont i nued) .
number average
slides density I % pop.
Cymbe1 1 a mi nuta var. s i1es i aca
(Bleisch 6 Rabh.) R^im.
1
0.008
0.000
Cvmbella parvula Krasske
1
0.031
0.000
Cyrribella prostrata var. auerswaldii
(Rabh.) Reim.
4
0.064
0.001
Cymbella prostrata (Berk.) CI.
1
0.008
0.000
Cymbe11 a spp.
1 1
0.302
0.004
Dtnticula spp.
1
0.016
0.000
Denticula tenuis var. crassula
(Naeg. £ KUtz.) West & West
7
0.086
0.002
Diatoma ehrenberqii Klltr.
1
0.016
0.000
Ciatoma spp.
2
0.016
0.001
Diatoma tenue Aq.
5
0.120
0.005
Diatoma tenue var. elonqatum Lynqb.
71
22.650
0.397
Diatoma vulgare Bory
3
0.138
0.003
Diploneis boldtiana CI.
1
0.016
0.000
D i pionei s parma C1 .
2
0.016
0.000
Cipi one is spp.
1
0.031
0.001
Entomoneis ornata (J. W. Bail.) Reim.
10
0.231
0.003
Eucocconeis spp.
5
0.^70
0.002
Fraqilaria brevistriata Grun.
i»8
7.870
0.059
Fraqilaria brevistriata var. inflata
(Pant.) Hust.
3^
4.805
0.023
Fraqilaria capucina Desm.
21:
.797.731
14.135
Fraqilaria construens (Ehrenb.) Grun.
116
37-4U
0.346
Fraqilaria construens var. bincdis
(Ehrenb.) Grun.
2
0.039
0.000
Fraqilaria construens var. minuta Temp.
&
Per
^5
2.002
0.029
Fraq'laria construens var. subsalina Hust
l
0.202
0.003
Fraqilaria construens var. venter
(Ehrenb.) Grun.
63
16.120
0.070
Fraqilaria crotonensis Kitton
219
154.444
2.234
Fraqilaria intermedia Grun.
k
0.335
0.010
Fraqilaria intermedia var. fallax (Grun
)
A. CI .
5
0.319
0.008
Fraqi'aria leptostauron (Ehrenb.) Hust.
15
1-398
0.033
Fraqilaria pinnata var. intercedens
(Grun.) Hust.
2
0.693
0.015
Fraqilaria pinnata var. lancettula
(Schum.) Hust.
9
0.445
0.005
Fragilarla pinnata Ehrenb.
159
36.044
0.403
Fraqi1 ar ia sp. #18
2
0.023
0.000
F rag i1ar i a sp. #2
1
0.008
0.001
F rag i1ar i a spp.
^3
3.058
0.052
Fraqilaria vaucheriae (KUt2.) Peters
33
1.117
0.019
193
-------
APPENDIX 1. (continued).
number average
slides density I % pop.
F rag i 1 ar i a "aucher i ae var. capi teI lata
(Grun.) Patr.
9
2.883
0.005
Fraailaria vaucheriae var. lanceolata
A. Mayer
3
0.550
0.001
Fraqilaria vaucheriae var. truncata
(Grev.) Grun.
?
0.032
0.002
Gomohonema anqustatum (KUtz.) Rabh.
1
0.016
0.001
Gomphonema olivaceum (Lynqb.) KUtz.
h
0.01*0
0.002
Gomphonema parvulum (KUtz.) KUtz.
2
0.073
0.001
Gomphonema spp.
3
0.039
0.001
Gyrosiqma acuminatum (KUtz.) Rabh.
1
0.016
0.000
Gyrosiqms sciotense (Sullivant 6 Wormley) CI.
2
0.016
0.000
Melosira distans var. alpiqena Grun.
33
^-778
0.028
Melosira qranulata fo. spiralis Grun.
1
o. 195
0.000
Meiosira qranulata var. anqustissima
C. MU11 .
8
*•175
0.035
Melos:ra qranulata (Ehrenb.) Ralfs
113
73-796
0.395
Melosira islandica 0. MU11.
31
2.005
0.061)
Melosira italica subsp. subarctica 0.
MUI 1 .
12
0.U13
o.ou
Melosira varians Aq.
2
0.389
0.002
Meridion c^rculare (Grev.) Aq.
1
0.0*«9
0.005
Navicula acceptata Hust.
1
0.008
0.00c
Navicula ariqlica var. subsalsa (Grun.
) CI .
1
0.008
0.000
Navicula aurora Sov.
1
0.008
0.000
Navicula bacillum Ehrenb.
1
0 008
0.000
Navicula capitata Ehrenb.
3
0.032
0.002
Navicula capitata var. 'uneburqensis
(Grun.) Paf.
1
0.065
0.001
Navicula cryptocepi.a 1 a var. intermedia Grun.
3
O.089
0.002
Navicula cryptocepha1 a var. veneta (KUtz.) Rabb.
15
0.1*67
0.006
Navicula cryptocepha1 a KUtz.
10
0.1*91
0.003
Navicula exiquiformis Hust.
1
0.008
0.000
Navicula qraciloides A. Mayer
1
0.032
0.000
Navicula qreqaria Donk.
13
1.092
0.010
Navicula heufleri var. leptocephala
(Br6b) Patr.
1
0.032
0.000
Navicula lanceolata (Aq.) KUtz.
3
0.021*
0.002
Navicula luzonensis Hust.
2
0.097
0.001
Navicula menisculus var. upsaliensis
Grun.
1
0.008
0.000
Navicula minima Grun.
1
0.016
0.000
Navicula monoculata Hust.
1
0.008
0.000
Navicula paludosa Hust.
2
0.065
0.000
Navicula pelliculosa (Br6b) Hilse
1
0.065
0.000
Navicula pupula KUtz.
5
0.063
0.002
Navicula radiosa var. tenella (Br6b)
Grun.
16
0.391
0.001*
Navi-ula radiosa KUtz.
5
0.070
0.000
194
-------
APPENDIX 1. (continued).
number average
s 1 i des
density &
% pop.
Navicula salinarum Grun.
1
0.008
0.001
Navicula scutelloides W. Smith
2
0.097
0.001
Navicula seminuloides Hust.
2
0.080
0.001
Navicula seminulum Grun.
2
0.02b
0.001
Navicula sp. #81
1
0.065
0.000
Navicula sp. #82
2
0.039
0.000
Navicula sp. #8U
1
0.016
0.000
Navicula spp.
50
2.352
0.036
Navicula tripunctata var. cuneata
(Lauby)
Stoerm. & Yang
2
0.073
0.0c
Navicula tripunctata (0. MU11.) Bory
3
0.138
0.001
Navicula ventralis fo. simplex (Hust.)
Hust.
l
0.016
0.001
Navicula viridula var. avenacea (Brtb.)
V. H.
2
o. 130
0.001
N
tzsch i a
acicu1arioides Arch.
3
0.170
0.001
N
t2sch i a
acicularis (KUtz.) W. Smith
Ub
3.908
0.036
N
tzsch i a
acidoclinata Lange-Bfrta1ot
1
0.130
0.001
N
tzsch i a
acuta Hantz.
8
0.09*4
0.00b
N
tzsch i a
amphibia Grun.
3
0.089
0.001
N
tzsch i a
anqustata (W. Smith) Grun.
5
0.186
0.000
N
tzsch i a
anqustata var. acuta Grun.
17
0.673
0.005
N
tzsch i a
brevirostris Hust.
1
0.008
0.000
N
tzsch i a
capi tellata Hust.
5
0.169
0.001
N
tzsch i a
confini Hust.
S
0.172
0.005
N
tzsch i a
dissipata (KUtz.) Grun.
18
0.352
0.009
N
tzsch i a
dissipata var. media (Hantz.)
Grun.
b
0.087
0.003
N
tzsch i a
fonticola Grun.
2b
0.739
0.009
N
tzsch i a
fcnticola var. pelaaica Hust.
1
0.032
0.000
N
tzsch i a
frustulum var. tenella Grun.
ex V. H.
5
0. 186
0.001
N
tzsc h i a
qraci1 ifo-mis Lanqe-Berta1ot
1
S i monsen
7
0.11«9
0.005
N
tzsch i a
arac i1i s Hantz.
UO
1.051
0.025
N
tzsrh i a
holsatica Hust.
2
0.300
0.001
N
tzsch i a
kutz i nq i ana H i1se
69
2.1+25
0.037
N
tzsch ia
1auenbergiana Hust.
1
0.008
0.000
N
tzsch i a
lonqissima var. reversa G.un.
2
0.195
0.000
N
tzsch i a
palea (KUtz.) W. Smith
32
.0.758
0.022
N
tzsch i a
palea var. deb Mis (KUt2.) Grun.
16
1.7^0
0.006
N
tzsch i a
palea var. tenuirostris Hust.
3
0.178
0.000
N
tzsch i a
paleacea Grun.
l»
0.031
0.001
N
tzsch i a
planctonica Hust.
1
0.031
0.000
N
tzsch i a
pumi1 a Hust.
2
0.162
0.001
N
tzschia
pura Hust.
16
0.706
0.0H
N
tzsch i a
recta Hantz.
1;
0.056
0.001
N
tzsch i a
romana Grun.
3
0.258
0.002
19S
-------
APPENDIX 1. (continued)
number average
s1i des
dens i ty &
1 pop.
Nitzschia sinuata var. tabe i!ar i a {Grun.) Grun.
1
0.031
0.000
N i tzsch ia sp. #1
19
0.733
0.004
N i tzsch ia sp. #10
5
0.241
0.002
Nit2schia sp. #If*
r
c
1 .071
0.005
Ni tzschia sp. #1?
1
0.065
0.000
Nitzschia sp. #2
1
0.016
0.000
N tzsch i a sp. #32
13
0.210
0.010
Nitzschia sp. #38
1
0.008
0.000
Nitzschia sp. #40
136
11.866
0. 144
Nitzschia sp. #6
3
0.160
0.003
Nitzschia sp. #7
1
0.130
0.000
Nitzschia sp. #9
u
0.409
0.003
Nitzschia spiculoides Hust.
22
1 .000
0.012
Nitzschia spiculum Hust.
1
0.041
0.001
N i t2sch i a spp.
182
19-026
0.252
Nitzschia subacicuiaris Hust.
7
0.376
0.003
Nitzschia subcapite11ata Hust.
3
0.130
0.000
Nitzschia sub 1 i near i s Hust.
5
0.364
0.002
Nitzschia tryb1i one 11 a var. debilis
(Arnott) Mayer
9
0.222
0.004
Opephora mar ty i Herib.
2
0.080
0.000
Rhizosolenia eriensis H. L. Smith
125
7.049
0.183
Rh i zosolen i a gracilis H. L. Smith
96
6.956
0.225
Rhizosolenia spp.
47
3-818
0.034
Rh i 2oso1 en i a statospore
1
0.032
0.000
P.ho i cosDhen i a curvata (KU*z.) Grun.
\
0.105
0.001
Rhoicosphenia sp.
1
0.008
0.000
Ske1etonema potamos (Weber! Hasle
31
20.958
0.123
Skeletonema spp.
5
0.994
0.007
Stephanod i scus alpinus Hust.
134
11.882
0.197
Stephanod i scus b i nderanus (KUtz.) Kr i eo.
65
27-412
0.435
Stephanodiscus hantzsch i i Grun.
86
13. 198
0.253
Stephanodiscus minutus Grun. ex CI. & Mdl 1 .
94
10.722
0.099
Stephanodiscus niaqarae Ehrenb.
82
3.195
0.032
Stephanodiscus sp. #10
42
4.496
0.031
Stephanodiscus sp. #5
10
0.395
0.006
Stephanodiscus spp.
67
19.386
0.118
StephanodIscus subtil is (Van Goor) A. CI.
160
82.658
0.769
Stephanodiscus tenuis Hust.
96
66.465
0.534
Surirella anqusta KUtz.
3
0.031
0.001
Sur i re 11 a ovata KUtz.
17
0.454
0.012
Surirella ovata var. pinnata (W. Smith) Hust.
16
0.552
0.013
Sur i re 1 I a spp.
11
0.208
0,003
Surirella suecica Grun. ex V. H.
10
0.574
0.003
1%
-------
APPENDIX 1. (continued)
Syneara eye Iopum Brutschy
Synedra de I i cat i ss i ma var. anqusti ss ima Grun.
Synedra f i Ii form i s var. ex i1i s A. CI.
Svnetira f i 1i formi s Grun.
Synedra mi nuscuI a Grun.
Svneara os tenfeId i i u. rieger) A. CI.
Synedra paras i t i ca (W. Smith) Hust.
Synedra rumpens KUtz.
Synedra rumpens var. fami Ii ar i s (KUtz.) Hust.
Synedra rumpens var. f raq iIar i o i des
Grun . ex V. H.
Synedra spp.
Synear a uIna var. chaseana Thomas
Synedra uIna (Nitz.) Ehrenb.
T abe Maria fenestrate (Lyngb.) KUtz.
T abe1 Iar i a f1occu1osa var. geii culata
(CI.-E.) Knudson
Tabe11ar i a flocculosa (Roth) KUtz.
Tabe11ar i a fIoccuIosa var. 1i near i s Koppen
Tha1 ass i os i ra spp.
Undetermined centric diatom spp.
Undetermined pennate diatom
total diatoms ( 2k~J categories)
Chrysophyta
Arachnoch1 or i s ret i cuI a ta (Pasch.) Bourr.
rhr vs i d i astrum ca tenatum Itb.
Chrysococcus dok idophorus Pasch.
Chrysococcus rufescens Klebs
Chrysococcus spp.
Chrysophycean cyst
Chrysosphaere11 a longi spi na Ltb.
D i nobryon cy1i ndr i cum Imh.
D i nobryon cyst
D i nobryon d i vernens Imh.
Di nobryon soc i a 1e Ehrenb.
Di nobryon spp.
Kephyr i on spi raIe (Lack.) Conr.
Ma 1)omonas a 1 pi na Pasch.
Ma 11omcnas eIonqata Rev.
Mai 1omonas pseudocoronata Prescott
Mai 1 omonas sp. ft3
number average
s1i des
dens i ty 6
1 pop.
7
0.078
0.002
*3
0.895
0.023
25
0.928
0.025
180
^9•287
O.76I4
20
0.616
0.020
61
2.131
0.059
2
0.078
0.001
1
0.016
0.000
1
0.023
0.001
3
0.m3£
. . r ;
UU
2.770
0.C'30
10
0.133
0.005
7
0.291
0.0014
91
15.W3
0.51^
1
0.101
0.010
9
0.1409
0.023
1U9
30.801*
0.7^2
7
2.790
0.013
73
15.836
0.106
13
0.1*10
0.001.
38143.911
38.056
1
0.016
0.000
1
0.008
0.000
38
0.811
0.037
20
O.I4IO
0.013
19
1.81 1
0.0145
65
2.090
0.0142
A1
7-^5
0. 136
9
2.912
0. 1 Oil
62
2.916
0.080
12
l .760
0.01*8
6
2.1478
0.015
1U
32.585
0.833
2
0.080
0.001
102
^ - 525
0.0146
9
0.103
0.003
^9
1.557
0.016
l
0.008
0.000
197
-------
APPENDIX 1. (continued).
number average
slides density 6 % pop.
Ma 1 1omonas spp.
15
0.357
0.014
Mallomonas statospore
17
0.244
0.006
Monochrvsis aphanaster Skuia
186
H-557
0.255
Ochromonas sp. #3
2
0.078
0.001
Ochromonas spp.
260
247•193
3.183
Rhizochrysis limnetica G. M. Smith
1
0.0)6
0.000
Spiniferomonas spp.
171
16.262
0.355
Synura spp.
1
0.311
0.003
Synura uvella Ehrenb.
4
0.358
0.010
Tribonema spp.
11
1 .361
0.016
Tribonema subti1issimum Pasch.
3
0.171
0.003
Undetermined colonial chrysophyte
1
0.973
0.002
Undetermined individual chrysophyte
6
0.240
0.003
total chrysophytes ( 30 categories)
3^0.871
5.271
Cryptophyta
Chroomonas spp.
265
126.813
2.C ' l
Cryptomonas erosa Ehrenb.
31
2.674
0.02.;
Cryptomonas qracilis Skuia
7
0.407
0.004
Cryptomonas marssonii Skuia
57
3.007
0.038
Cryptomonas ovata Ehrenb.
214
38.607
0.368
Crvctomonas oyrenoidifera Geitler
'9
0.889
0.012
Cryptomonas rostratiformis Skuja
^5
1 .792
0.014
Cryptomonas sp. Pi
118
14.938
0. 12C
Cryptomonas spp.
198
34.478
0.417
Rhodomonas minuta Skuia
260
231-573
3.041
Rhodomonas spp.
W
14.1*60
0.152
total cryptomonads ( 10 categories)
469.232
6.217
Pyrrhophyta
Ceratium hirundinella (MU11.) Shrank
27
0.631
0.005
D i nof 1 age 11 ate cyst
8
0.165
0.002
Glenodinium bernardinense Chod. 6 Zend.
5
0.243
0.006
Gymnodinium helveticum Penard
13
0. 188
0.005
Gymnodinium ordinatum Skuia
50
1 .460
0.026
Gymnodinium spp.
*~5
1-737
0.031
Peridinium achromaticum Levander
10
1 .012
0.013
Peridinium spp.
23
0.503
0.013
Unidentified dinof1 age 11 ate spp.
168
8.842
0.132
1 98
-------
APPENDIX 1. (continued)
number average
slides density I % pop.
total dinof1agellates
( 10 categor i es)
U.789
0.2314
Eug1enophyta
Euqlena acus Ehrenb.
1
o. 130
0.001
Euglena spp.
5
0.213
0.002
Phacus spp.
1
0.032
0.000
total euglenoids
( 3 categories)
0.376
0.003
199
------- |