PB83-250035
                                    EPA-600/3-83-075
                                    August 1983
      EFFECTS OF PHOSPHORUS LOADING
      ON PHYTOPLANKTON DISTRIBUTION
     AND CERTAIN ASPECTS OF CYTOLOGY
        IN  SAGINAW BAY,  LAKE  HURON

                    by

             E. F. Stoermer,
            L.  Sicko-Goad,  and
                L.  C.  Frey

      Great Lakes Research Division
        The University of Michigan
        Ann Arbor, Michigan 48109
             Grant No.  802780
             Project Officer
             Nelson A.  Thomas
     Great Lakes Research Laboratory
Environmental Research Laboratory - Duluth
        Grosse lie, Michigan 48138
ENVIRONMENTAL RESEARCH LABORATORY - DULUTH
    OFFICE OF RESEARCH AND DEVELOPMENT
   U.S. ENVIRONMENTAL PROTECTION AGENCY
          DULUTH, MINNESOTA  55804

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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 or recommendation for use.
                        11

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                                  ABSTRACT
     Phytoplankton abundance and species composition in Saginaw Bay reflects
very high nutrient and conservative ion loadings.  Typical of nutrient
stressed systems, seasonal succession and areal distribution are highly
variable, and large abundance and composition   changes may be generated by
local meteorological events.  Spring flora  are dominated by diatoms such as
Fragilaria capucina and Stephanodiscus binderanus, which are associated with
the most eutrophied regions in the Great Lakes.  Atypically large numbers of
benthic diatoms occur in Saginaw Bay plankton.  Following the spring diatom
bloom, assemblages become dominated by blue-green and green algae, apparently
due to rapid silica depletion.  Nuisance populations such as Aphanizomenon
flos-aquae and Anacystis cyanea are common.  In late summer there is a second
increase in diatom abundance, apparently due to regeneration and recircula-
tion of silica from the sediments.  This secondary diatom bloom is composed
of species such as Actinocyclus normanii var. subsalsa and Melosira granulata.
     Our results show substantial export of phytoplankton populations from
the bay to Lake Huron.  Under average wind conditions, most export occurs
along the southern coast and these populations are then entrained in the
general Lake Huron circulation and spread down the Michigan coast southward
from the bay.  Under certain advective conditions, however, phytoplankton may
be discharged from the bay either northward or directly offshore.

     Cytological analysis shows that many of the species present sequester
phosphorus in excess of their immediate physiological needs in the form of
polyphosphate bodies.  Polyphosphate body formation may be triggered by
conditions which interfere with normal phosphorus metabolism.  These include
phosphorus starvation followed by excess resupply, deficiencies in other
essential nutrients, or toxic effects which limit growth but not phosphorus
uptake.  All of  these conditions may occur in Saginaw Bay.  Our analysis
further shows that populations exported from the bay contain excess
phosphorus and this biologically entrained loading may affect other areas of
southern Lake Huron.
     Analysis of polyphosphate bodies also shows that significant quantities
of certain toxic trace metals, notably Pb, are incorporated into these
inclusions.  The ultimate fate of this material has not been demonstrated,
but  it may represent a previously unrecognized type of biological
incorporation and  transport  important in some areas of the Great Lakes.

     We  also investigated the relationship of total phytoplankton cell vol-
ume  to  protoplasmic constituent volume using quantitative morphometric
techniques.  This  analysis  shows that crude cell volume furnishes a poor
estimate of  actual  living biomass in many populations, and indicates that
more  refined techniques are  necessary to correctly convert estimates of cell
number  to estimates of biomass.

                                      ill

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                                   CONTENTS
Abstract 	

Figures 	    vi

Tables 	    ix

Introduction 	     1
   Major Components of this Project 	     4

Section 1 	     5
   Distribution of Major Phytoplankton Groups  	     5
   Materials and Methods 	     5
   Discussion  	    55
   References  	    62

Section 2 	    64
   Biomass Estimates  	    64
   Introduction 	    64
   Materials and Methods 	    64
      Quantitative Stereological Methods  	    65
   Results and Discussion  	    69
      Descriptive Electron Microscopy  	    69
         Anabaena flos-aquae (Cyanophyceae)  	    69
            Cell Wall -- 	    69
            "Pseudovacuole" —  	    69
            Nitrogen  Storage —  	    72
            Phosphate Storage — 	    72
         Stephanodiscus binderanus and Fragilaria capucina
           (Bacilliarophyceae)  TTT	    72
            Frustule  — 	    72
            Vacuole —  	    75
            Storage Products —  	    75
            Chloroplast — 	    75
            Cytoplasm — 	    75
         Euglena viridis (Euglenophyceae)  	    75
            Cell Wall — 	    75
            Vacuole —	    77
            Storage Products —  	    77
            Chloroplast — 	    77
            Cytoplasm — 	    77

                                       iv

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        Cryptomonas erosa  (Cryptophyceae)  	     77
           Cell Wall —	     77
           Vacuole —  	     79
           Storage Product —  	     79
           Chloroplasts  — 	     79
           Cytoplasm —  	     79
        Peridinium lindemanni  (Dinophyceae)  	     79
           Cell Wall --	     79
           Vacuole —  	     79
           Storage Products — 	     81
           Chloroplast —  		     81
           Cytoplasm —  	     81
        Prymnesiophycean Algae -  Two  Undetermined  Species  	     81
           Cell Wall —	     83
           Vacuole —  	     83
           Storage Products — 	     83
           Chloroplasts  — 	     83
           Cytoplasm —  	     83
      Quantitative Electron Microscopy 	     83
         Sample Size Determination —  	     83
      Filament Analysis 	     84
      General Descriptive Measures 	     84
        Anabaena  flos-aquae 	     87
         Stephanodiscus binderanus and Fragilaria capucina	      87
         Euglena viridis  	     87
         Cryptomonas  erosa  	     90
         Peridinium lindemanni  	     90
            Prymnesiophycean Algal Species 1  and 2  	     90
   Discussion	     90
   References 	     95

Section 3  	    100
   Luxury  Consumption,  Storage, and Transport of Phosphorus
     in Saginaw Bay 	    100
   Introduction 	    100
   Materials  and Methods 	    101
      Light Microscopy  	    101
      X-Ray Energy Dispersive Analysis 	    101
      Phosphate Uptake  in Diatoma E1ongatum 	    101
   Results	    102
   Discussion 	    105
   References 	    109

Appendix 1.  Phytoplankton of Saginaw Bay (Lake Huron), 1974-1976	    112

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                                   FIGURES
Number

Section 1

  1     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 25 March 1974	
  2     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 6 April 1974	
  3     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 28 April 1974	
  4     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 13 May 1974	
  5     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 3 June 1974	
  6     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 17 June 1974	
  7     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 8 July 1974	
  8     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 24 July 1974	
  9     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 25 August 1974	
 10     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 18 September 1974	
 11     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 6 October, 1974	
 12     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 11 November 1974	
 13     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 16 December 1974	
 14     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 20 February 1975	
 15     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 8 April 1975	
 16     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 28 April 1975	
 17     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 20 May 1975	
 18     Distribution of major phytoplankton groups in Saginaw Bay for
          cruise beginning 5 June 1975	
 6

 8

 9

10

11

12

14

15

16

17

19

20

21

22

24

25

26

27
                                      VI

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19     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 25 June 1975	
20     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 11 July 1975	
21     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 29 July 1975	
22     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 18 August 1975	
23     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 3 September 1975	
24     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 23 September 1975	
25     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 9 October 1975	
26     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 27 October 1975	
27     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 16 November 1975	
28     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 16 December 1975	
29     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 27 January 1976	
30     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 11 March 1976	
31     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 27 April 1976	
32     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 12 May 1976	
33     Distribution of major phytoplankton groups in Saginaw Bay for
 v       cruise beginning 1 June 1976	
34     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 18 June  1976	
35     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 8 July 1976	
36     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 28 July  1976	
37     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 11 August  1976	
38     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 31 August  1976	
39     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 18 September  1976	
40     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 7 October  1976	
41     Distribution of major phytoplankton groups in Saginaw Bay for
         cruise beginning 10 November 1976	
28

30

31

32

34

35

36

37

39

40

41

43

44

45

46

48

49

50

52

53

54

56

57
                                     VII

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Section 2

        Key to Figure Legends 	    70
 1      Anabaena flos-aquae X250	    71
 2      Anabaena flos-aquae X8600	    71
 3      Anabaena flos-aquae XI8,800	    71
 4      Anabaena flos-aquae X27,300	    71
 5      Stephanodiscus binderanus X980	    73
 6      Stephanodiscus binderanus X10,000	    73
 7      Stephanodiscus binderanus XIO.OOO	    73
 8      Stephanodiscus binderanus X9050	    73
 9      Fragilaria capucina X750	    74
10      Fragilaria capucina X8250	    74
11      Fragilaria capucina XI8,200	    74
12      Euglena veridis X1060	    76
13      Euglena veridis X5280	    76
14      Euglena veridis X12,100	    76
15      Cryptomonas erosa X2130	    78
16      Cryptomonas erosa X12,300	    78
17      Cryptomonas erosa X22,900	    78
18      Peridinium lindemanni X810	    80
19      Peridinium lindemanni X6960	    80
20      Peridinium lindemanni X6540	    80
21      Haptophyte #1 X25.700	    82
22      Haptophyte #2 X31,500	    82
23      Cumulative mean (percent volume) as a function of sample size
          (number of micrographs) for five cytoplasmic components of
          P_.  lindemanni and Hap. 1	    85


Section 3

  1      An undetermined small blue-green alga with large polyphosphate
          (PP) bodies in both electron lucent and electron dense regions
          of  the cell	   104
  2      Anacystis sp. with polyphosphate bodies (PP)	     104
  3      Fragilaria capucina with small polyphosphate bodies (pp)
          in  the vacuole (V), which is surrounded by the chloroplasts  (C)
          and other cellular organelles....	   104
  4      Scenedesmus sp. with large polyphosphate bodies in the vacuole    104
  5      Marginal region of the  Diatoma tenue var. elongatum cell show-
          ing chloroplast (C),  mitochondria (M), and the vacuole (V)...   106
  6      Vacuolar (V)  region of  Diatoma tenue var. elongatum cell	   106
  7      X-ray spectrum of Diatoma tenue var. elongatum
          polyphosphate bodies	   106
                                     Vlll

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                                    TABLES
Number

Section 2

  1     Sampling scheme employed for morphometric analysis	    66
  2     Cell volume estimates for the eight phytoplankton
          spec ies examined	    68
  3     Analysis of variance (ANOVA) of between and within
          filament variance	    86
  4     Percent volumes of cytoplasmic compartments in eight
          phytoplankton species	    88
  5     Absolute volumes of defined areas in the algae	....    89
Section 3
        Distribution of polyphosphate bodies in naturally-occurring
          phytoplankton in Saginaw Bay	   103
                                      IX

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                                INTRODUCTION
     Saginaw Bay has probably always been one of the more productive regions
within the Great Lakes system.  The productivity of the fishery resource was
undoubtedly one of the factors attracting early settlement in the area.
Other natural resources of the drainage basin provided the incentive for
early settlement and substantial economic growth in the region.  The timber
resources of the Saginaw River and its tributaries were rich and easily
accessible which led to early development of the area and the establishment
of an early industrial base.  Once cleared of its natural vegetation, much of
the land was found suitable for intensive agricultural practices.  Finally,
the presence of subsurface resources, primarily petroleum and salt, made
possible the establishment of one of the midwest's centers of chemical
industry.  Unfortunately, the development of the Saginaw-Bay City-Midland
industrial complex and intensive regional agriculture proceeded at the
expense of severe deterioration of water quality within Saginaw Bay.  At the
present time it is one of the most seriously modified parts of the Great
Lakes system.  During the past few decades Saginaw Bay has been beset with
water quality problems including obnoxious algal blooms, taste and odor
problems in municipal water supplies, and fish flesh tainting.  The history
of these problems and the context of the present investigation have been
outlined by the International Joint Commission (1976).  The literature
pertaining to pollution problems in Saginaw Bay has been reviewed by Freedman
(1974) and need not be extensively recapitulated here.  It should be pointed
out, however, that the perturbation of primary producer communities in this
region reflects the effects of many factors.  The most obvious of these are
the effects of excessive nutrient loadings.  At the present time the waters
of Saginaw Bay are probably the most productive in the entire Great Lakes
system.  The composition of the phytoplankton and benthic algal flora also
reflects the effects of extreme conservative element loadings.  Although
these loadings have apparently been decreased to some degree in recent years
(Smith et al., 1977), the flora of the bay still contains many elements
usually  found in brackish water localities.  Finally, although not
experimentally documented, certain population distributions within the bay
can most plausibly be explained by direct toxic effects.

     Saginaw Bay is also an extremely dynamic system.  There are strong
gradients in almost all  factors of physiological interest between the  lower
bay and  the open waters of Lake Huron.  As might be expected,  these gradients
are reflected in the population and community responses of the phytoplankton
 flora.   This situation is complicated by the physical dynamics of the  system
 (Richardson, 1974).  Idealized dilution gradients are grossly modified by
mass  transport of water masses and their entrained chemical constituents,
 fauna, and  flora into and away from the bay.  Schelske et al.  (1974) have
demonstrated the transport of populations developed in Saginaw Bay into  the

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open waters of Lake Huron.  One of the most interesting aspects of this study
is the fact that there appears to be considerable selection among the
population components of the assemblage being transported.  Certain
populations, primarily blue-green algae, appear to be conserved, in the sense
that their abundance is highly correlated with the concentration of
biologically conservative chemical elements being discharged from the bay.
Other populations, primarily diatoms, are apparently subjected to much
greater losses during transport.  Because of the different physical
characteristics of the populations involved, it is attractive to attribute
such losses to sinking.  Without further direct evidence, however, other
possible losses, such as predation or direct cell death and lysis, cannot be
excluded.  Equally interesting, conservation of mass demands that transient
mass flow export of water from Saginaw Bay be compensated by import of water
masses from Lake Huron.  Such water masses contain biological communities
adapted to physical and chemical conditions found in the open lake.  As they
are diluted with, and enriched by, Saginaw Bay water such populations might
be expected to undergo variable responses ranging from death to growth
stimulation depending on both their own physiological requirements and the
degree and rate of mixing.

     A meaningful analysis of such a dynamic system requires either extremely
intensive sampling, both areally and timewise, or recourse to simulation of
the system from a more limited measurement base.  Since a sampling program of
the density demanded is probably beyond the available regional resources, and
the simulation approach offers the additional advantage of making more
reasonable forecast and hindcast projections, the primary emphasis in this
project was directed toward  facilitating this type of analysis.  A number of
types of information regarding phytoplankton are necessary.  Since any
assemblage is likely to contain representatives of several major
physiological groups with differing absolute or relative nutrient
requirements, it is necessary that qualitative information be retained in the
model data input.  It  is also necessary that the input be in some uniform
measure.  Since phytoplankton cells vary considerably in size, even within a
given species, it is highly  attractive  to rely upon some secondary estimate
of biomass such as total carbon or extracted chlorophyll.

     Unfortunately this approach, although the one generally utilized in such
studies, is subject to a number of difficulties and the correlation between
such measures and independent estimates of phytoplankton biomass  for
assemblages occurring  in the Great Lakes is often surprisingly low
(Vollenweider et al.,  1974).  Although  considerably more laborious, direct
enumeration of the cells present and subsequent reduction of this  information
to some  standard unit  appears to offer  a desirable alternative, especially
since qualitative  information can be preserved in the resultant data set.
Although perhaps the most desirable approach, this method is not without its
own significant difficulties.  The most generally utilized approach is to
estimate the volume of the cells present, then to directly convert the
volumetric estimate to mass.  As may be easily appreciated, precise estimates
of volume  are difficult to obtain because of the complex  form of many species
and the  degree of variability present  in many populations.  A fundamentally
more  serious problem  is the  variation  in cytologic structure and  composition
between  the major physiological groups  of phytoplankton or, in some cases,

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within members of a single division.  It has long been recognized (Lohmann,
1908) that relatively large proportions of the total volume of the cells of
certain phytoplankton species are constituted by their vacuoles.  If the
fractional volume constituted by metabolically inert wall materials is added
to this, it is easy to see that direct conversions from cell volume to
estimates of biomass are difficult to interpret precisely.  It is indeed
unfortunate that estimates of phytoplankton abundance in the current
literature are reported in units of "biovolume" since this neither provides
an unambiguous estimate of biomass nor preserves individual population
abundance information.  Perhaps the most commonly utilized method of
converting phytoplankton abundance estimates to estimates of biomass is
regression of cell volume or plasma volume estimates on independent estimates
of cell carbon content (Strathmann, 1967).  While this method may be
applicable when dealing with relatively homogeneous oceanic phytoplankton
assemblages, it is somewhat questionable in a situation such as Saginaw Bay
which has exceedingly diverse assemblages containing many pseudoplanktonic or
tychoplanktonic populations.

     These considerations make  it evident that determination of precise
estimates of phytoplankton composition and biomass within the Saginaw Bay
system  is a considerable challenge within the inevitable constraints of
available resources.  Additional constraints are introduced by consideration
of the  overall project objectives.  The entire investigation involved the
first really large scale investigation on the Lake Huron system and consisted
of several components.  Although each of the components was the prime
responsibility of a separate laboratory, they are linked to the project
reported here through a common  sampling base.  In some cases the data
generated by this project have  been incorporated into the results of other
projects.  The major projects interfacing with this one are the following:

      1.  A study of physical and chemical conditions in Saginaw Bay reported
by Smith et al. (1977).

      2.  Construction of a process  oriented model of Saginaw Bay reported  by
Biermann et al. (1980).  One of the major efforts in the  present
investigation was the generation of phytoplankton volume/abundance estimates
which provided a major input to the above study.  The synthesized results  of
this  effort are reported there.

      3.  Studies of the distribution of primary consumer  organisms in Saginaw
Bay  and southern Lake Huron  (Gannon, in prep., Stemberger et al. (1979).

      4.  Studies of physical and chemical conditions and  biological
productivity  in southern Lake Huron by Schelske et  al.  (1980).

      5.  A study of phytoplankton  abundance and distribution  in southern Lake
Huron  by Stoermer and Kreis (1980).

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MAJOR COMPONENTS OF THIS PROJECT

     The major effort in this investigation was to provide data on
phytoplankton biovolume to support a model of processes in Saginaw Bay.  This
information has been reported by Beirmann et al. (1980).  For purposes of  the
model, the data were summarized in categories representing the major
physiological groups of phytoplankton which occupy the base.  It was  felt
that the actual numbers of organisms and the time sequence of development  are
also important in interpreting trends within the bay.  This information  is
reported in the first section of the present report.

     The interpretation of cell volumes in terms of biotnass, although
demonstrably preferable to traditional methods  of biomass estimation,
contains certain problems which have not been adequately addressed.  As  part
of this study, we undertook research directed to developing a method of
estimating the actual viable fraction of the cell volumes of representatives
of the various physiological groups of phytoplankton  found in Saginaw Bay.
The results of this study are presented in Section 2  of this report.

     Relatively early in the project it became  apparent that at least certain
populations generated within Saginaw Bay exhibit delayed response  to
phosphorus enrichment, or at least thrive far beyond  the zones of  the bay
most directly affected by high phosphorus loadings.   Since some blue-green
algal populations contained polyphosphate bodies apparent at the light
microscope level, we undertook further research to  investigate several
questions:

     1.  Are polyphosphate bodies quantitatively important in some of the
more abundant potential nuisance organisms, particularly species of
blue—green algae?

     2.  Are the bodies present in populations  advected from the bay  in
sufficient quantitatives to allow further growth of potential nuisance
organisms  in southern Lake Huron?

     3.  Are the eukaryotic organisms which display distribution patterns
similar to thse blue-green algal populations also capable of storing  excess
phosphorus in areas of high loading and subsequently  metabolizing  it  after
being advected  into areas not receiving direct  loadings?

     The results of this study are reported in  Section  3 of this report.
Also, as part of this study, we discovered that appreciable quantities of
certain heavy metals, particularly Pb, are also sequestered in polyphosphate
bodies  in  Saginaw Bay phytoplankton.  These observations have been separately
published  (Stoermer et al., 1980).

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                                 SECTION 1

                 DISTRIBUTION OF MAJOR PHYTOPLANKTON GROUPS

                           MATERIALS AND METHODS
     The samples utilized in this study were taken in conjunction with water
chemistry and zooplankton samples as part of the combined study discussed
above.  The general sampling strategy employed has been discussed by Smith
et al. (1977) and will not be recapitulated here.

     In most instances phytoplankton samples were taken by submersible pump.
In some cases either Niskin or Van Dorn bottles were used due to mechanical
failures of the pumping system.  In all cases the phytoplankton samples were
taken in 125 ml polyethylene bottles and fixed with 4% (vol./vol.)
glutaraldehyde immediately upon collection.  Samples were kept on ice in
darkness until they were processed into slides.

     Material was prepared for analysis by the membrane clearing technique
(Schelske et al., 1976).  In most instances 50 ml of the original fixed
sample was prepared.  Due to the extremely dense phytoplankton assemblages
encountered at some stations, it was necessary to reduce the volume filtered
in some preparations to either 25 or 12.5 ml.

     Population estimates were developed from replicate 1 mm strip counts of
randomly selected areas of the slide preparations.  Populations present were
enumerated and the mean dimensions of the taxa were recorded.  Estimates of
the volume of the phytoplankton present were developed from calculations
based on approximate shape formulae of the species present.  The volume data
were converted to an estimate of carbon biomass (Bierman et al., 1980).

     Material fixed according to the schedule used for preparation for
electron microscopy (see Section 2) was used for verification of
identifications in some instances, since this procedure finishes superior
preservation of cellular structure.

     The first sampling cruise took place 25 March.  Relatively few stations
were actually sampled due to adverse weather conditions.  Diatoms were
dominant in the samples taken, with very large populations  present at cne
station in the southeastern sector (Fig. 1).  The abundance of diatoms at
this  station dominated  the total abundance pattern, since other stations had
much  smaller phytoplankton densities.  Other groups were of minor  importance.
Green and blue-green algae were noted at scattered stations, but heterocyst
forming blue-greens were totally absent.  Flagellates were  present at all
stations, but did not approach diatoms in total numbers.

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Figure 1.  Distribution of major phytoplankton groups  in  Saginaw Bay for cruise
                             beginning  25  March 1974.

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     Much more complete sampling, particularly of the lower bay, was
accomplished during the second cruise which began 16 April (Fig. 2).
Although no station achieved the very high total phytoplankton density noted
during the previous cruise, there was an increase in the average
phytoplankton abundance at the stations sampled.  Diatoms again were the most
abundant group, although the abundance of other groups increased
significantly.  Isolated large populations of green and blue-green algae were
found, although heterocyst-forming blue-greens were still essentially absent.
The distribution of flagellates was interesting.  Largest abundances were
found in the western half of the bay, which was opposite the trend of diatom
abundance.

     The fourth cruise began 28 April (Fig. 3).  Total phytoplankton
abundance continued to increase, with the largest proportional  increases
occurring in the flagellate groups.  As had been true during the previous
sampling period, there appeared to be an inverse relationship between the
abundance of diatoms and flagellates.  Green algae began to appear in
significant abundance at stations in and near the Saginaw River.  The
abundance of blue-green algae remained relatively low, and heterocyst-forming
taxa were still essentially absent.

     The fifth cruise was started 13 May (Fig. 4).  Overall phytoplankton
abundance continued to increase and extremely large abundances  were noted  at
stations near  the mouth of the Saginaw River.  All of the major  phytoplankton
groups were abundant at one or more stations in this region.  Flagellates
were  less abundant at most stations than during the previous cruise, but
green and blue-green algae continued to increase.  Relatively large
populations of heterocyst-forming blue-green algae were  found for  the first
time, particularly at shoreward stations.

     The sixth cruise was begun 3 June (Fig. 5).  During this cruise, a
distinct change in the distribution and abundance of major phytoplankton
groups became  apparent.  Diatoms remained abundant at stations  in  the
vicinity of the Saginaw River, but were generally reduced in abundance at
stations in other parts of the bay.  It appeared that populations  were
maintained  in  this region as a direct result of nutrient resupply  from the
Saginaw River, while populations in other regions of the bay were  becoming
nutrient limited.  Green and blue-green algae became more important elements
of  assemblages, particularly at  stations in the southern and eastern  sectors
of  the bay.   The distributions noted are probably indicative of incipient
secondary  silica and nitrogen limitation and transport of excess phosphorus
along the  eastern coast of the bay.

      The next  cruise was undertaken 17 June (Fig, 6).  Sampling during  this
period  showed  a substantially different trend  in phytoplankton  abundance  and
distribution  than  the  previous sampling round.  Phytoplankton abundance
generally  declined and  the distribution of major groups  was more erratic  than
 it  had  been during the  previous  sampling.  Relatively  large  abundances of
 total phytoplankton and particularly diatoms and green algae were  found  at
 stations  in the southeastern  sector of  the outer bay.  It appeared that
during  this  period these populations were being advected  from  the  bay  to  Lake

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00
                 Figure  2.   Distribution  of major phytoplankton groups in Saginaw Bay  for  cruise
                                              beginning 6 April  1974.

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Figure 3.   Distribution of major phytoplankton groups  in Saginaw Bay for cruise
                             beginning 28 April 1974.

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Figure A.  Distribution of major phytoplankton  groups  in Saginaw Bay for cruise
                              beginning  13  May  1974.

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Figure 5.   Distribution of major phytoplankton groups in Saginaw Bay for
                              beginning 3  June 1974.
cruise

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Figure 6.  Distribution of major phytoplankton  groups  in  Saginaw Bay  for  cruise
                             beginning 17 June 1974.

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Huron along the southeastern shore.  One of the unusual features of this
sample set was the extreme abundance of total phytoplankton and all of the
major groups at Station 44, near Oak Point.  The reason for the atypical
abundance at this particular station is not apparent.

     Cruise 8 was begun 8 July (Fig. 7).  Phytoplankton distribution at this
time was quite different than during the previous sampling period.  Total
phytoplankton abundance declined, and high population densities were
restricted mostly to stations in the lower bay and stations along the
southeastern shore.  The abundance of diatoms declined sharply except at
stations in the Saginaw River and immediately adjacent to its mouth.  Green
and blue-green algae remained relatively abundant, but heterocyst-forming
blue-green algae were restricted to stations in the southeastern segment of
the area sampled.  Relatively low abundance of flagellates was noted at all
stations sampled.  The most unusual feature of the results from this cruise
is the extremely low abundance of phytoplankton in segment 4 of the sampling
array.  As was the case in the previous set, it appeared that phytoplankton
from the lower bay was being transported along the southeastern coast of
Saginaw Bay and into Lake Huron.

     The next sampling round was undertaken 24 July (Fig. 8).  Phytoplankton
distribution during this sampling period was again markedly different than it
had been during the previous sampling  interval.  Total abundance increased
somewhat, but abundance consistently declined along the long axis of the bay
and there was no evidence of particularly high abundance along the southern
shore, as there had been previously.   Stations along the Lake Huron interface
and most stations in segment 5 had very low phytoplankton abundance.  Large
populations of diatoms and heterocyst-forming blue-green algae were
restricted  to stations near the mouth  of the Saginaw River.  Large
populations of diatoms were found at stations in the river, but blue-greens
were not particularly abundant except  in the bay.

     The next sampling cruise began 25 August (Fig. 9).  By this time the
total  abundance of  phytoplankton had generally decreased.  Assemblages were
dominated by blue-green algae, although the abundance of diatoms had
recovered slightly  from the levels observed during  the previous cruise.
Population  distributions of all groups was rather uniform, with a decrease  in
abundance from the  lower bay to the Lake Huron interface.  During  this
cruise,  greatest  phytoplankton abundance occurred at Station 50, the central
station  on  the Lake Huron  interface, rather than at  shoreward  stations as had
been  the general  case previously.  Flagellate numbers were very low during
this cruise and  the largest populations were found  in  the  lower bay.

     A further decline in  peak phytoplankton abundance was noted during  the
next  sampling cruise, which began  18 September (Fig. 10).  Relatively high
levels of  total  phytoplankton standing crop extended further  toward the  Lake
Huron  interface  however, particularly  at stations along  the southeastern
shore.   The flora was dominated by blue-green algae, particularly  taxa which
do not form heterocysts.   Significant  populations of heterocyst-forming
species  were  restricted to  stations  immediately  along  the  southeast shore.
Diatoms  were most  abundant  in the  Saginaw  River, but significant  populations
were  present  at  most  stations sampled.  Diatoms  increased  in  abundance at

                                      13

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Figure 7.  Distribution of major phytoplankton groups  in Saginaw Bay for cruise
                              beginning 8  July 1974.

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Figure 8.   Distribution of major phytoplankton groups in Saginaw Bay for  cruise
                             beginning 24 July 1974.

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Figure 9.   Distribution of major  phytoplankton  groups  in  Saginaw Bay for  cruise
                            beginning 25 August 1974.

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Figure 10.  Distribution of major phytoplankton groups  in Saginaw Bay for cruise
                           beginning 18 September 1974.

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stations in the Lake Huron interface, but the assemblage in this region
contained a completely different suite of populations than was present in the
Saginaw River or in the lower bay.  Green algae were a relatively important
part of assemblages sampled at most stations.  Unusually high numbers of
diatoms, green algae, and flagellates occurred at Stations 47 and 48 in
Tawas Bay.

     The next sampling cruise was delayed until 6 October (Fig. 11).  By this
time the general level of phytoplankton standing crop had increased somewhat
in most areas of the bay.  Blue-green algae remained the dominant element of
the flora,  but diatoms had increased significantly in abundance, particularly
at nearshore stations.  Heterocyst-forming blue-green algae were less
abundant than during the previous sampling period, but populations were
present at most stations sampled.  Green algae remained important at most
stations sampled and they, together with diatoms and flagellates, were the
most important components of the Saginaw River flora as it entered the bay.
The relative abundance of flagellates was also high at stations in the Lake
Huron interface, although a different suite of species was present there than
in the river and lower bay.

     The next samples were taken 11 November  (Fig. 12).  Although less than
complete sampling was achieved, a reasonably  complete reconstruction of
phytoplankton distribution within the bay can be made.  Total phytoplankton
standing crop decreased significantly from levels of the previous month.
Diatoms were the dominant element at most stations sampled, although
blue-green algae remained abundant, particularly at nearshore stations and
stations in  the lower bay.  The abundance of  heterocyst-forming taxa was much
reduced and  only small populations were  found at scattered stations.  Green
algae and  flagellates were relatively minor  elements of assemblages at
stations sampled.   In the lower bay there appeared to be an inverse
relationship between the abundance of these  two groups.

     Only  a  very limited number of stations  in the lower bay  and in the
Saginaw River were  sampled on  16 December (Fig. 13).  Somewhat  surprisingly,
the total  abundance of phytoplankton at  the  stations sampled  was relatively
high.  The flora was dominated by diatoms, with a minor and approximately
equal contribution  of blue-green  algae and flagellates.  Unlike previous
samples, flagellates were most abundant  in samples from the Saginaw River.
Green algae  were present, in low  abundance,  at most stations  sampled, but
heterocyst-forming  blue-green  taxa were  not  noted in this set of samples.

     A  similarly small number  of  stations in  the  lower bay were sampled on
20 February  1975 (Fig. 14).  Surprisingly high total phytoplankton abundance
was  found  at a  series of stations  in  the western half of segment 1.  Diatoms
dominated  the  flora in this  region and in total.  Flagellates were relatively
abundant at  a number of  nearshore  stations sampled.  Significant quantities
of green algae  were found only at  Station 59, although a  few  specimens of
species  in this group were noted  at most stations sampled.  Blue-green algae
were virtually  absent, although  a  small  population of Oscillatoria was found
at Station 14.
                                      18

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Figure 11.  Distribution of major phytoplankton groups in Saginaw Bay for cruise
                            beginning 6 October 1974.

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Figure 12.  Distribution of major phytoplankton  groups  in  Saginaw Bay for cruise
                           beginning 11 November 1974.

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Figure 13.   Distribution of major phytoplankton  groups  in  Saginaw  Bay  for  cruise
                           beginning 16 December 1974.

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Figure 14.  Distribution of major phytoplankton  groups  in  Saginaw Bay for cruise
                           beginning 20 February 1975.

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     A more comprehensive set of samples was obtained on a cruise beginning
8 April (Fig. 15).  Although the maximum abundance was significantly reduced
from the levels noted during the previous sampling period, relatively high
levels of phytoplankton standing crop were found at stations in the inner
bay.  During this period the flora was completely dominated by diatoms,
although green algae and flagellates were found in most assemblages sampled.
Blue-green algae were not present in significant abundance except at
Station 30.

     The next cruise in the sequence was undertaken 28 April (Fig. 16).
Total phytoplankton abundance had increased from levels of the previous
month.  The  flora was still dominated by diatoms, but increasing quantities
of green and blue-green algae were present, particularly at stations in the
lower bay and along the eastern shore.  Heterocyst-forming blue-greens were
still virtually absent at all stations sampled.  Flagellates were present  in
moderate abundance and representatives of this group were generally
distributed  at the stations sampled.

     By the  time  the next cruise was undertaken on 20 May (Fig. 17), maximum
levels of phytoplankton abundance in the bay had decreased somewhat.  Unlike
the previous month, however, relatively high levels of abundance were found
at  shoreward stations in the Lake Huron interface area.  This  increase was
accounted for mostly by diatoms, which remained the most abundant component
of  the  flora.  Diatoms were abundant in the Saginaw River and  at most
stations in  the bay.  Green and blue-green algae, on the other hand, were
abundant only at  stations in the inner bay.  Green algae were  particularly
abundant at  a series of stations just off the mouth of the Saginaw River.
Somewhat atypically, flagellates were abundant in the Saginaw  River and
adjacent stations, although certain populations were present at all stations
sampled.

     The number of stations sampled was reduced during the next cruise, which
began 5 June (Fig. 18).  At this time there was an extreme variance in
phytoplankton abundance among the stations sampled.  This was  exemplified  by
a very  high  abundance of blue-green algae at Station 34  in Wild Fowl Bay.
Diatoms remained, overall,  the most abundant of the major groups.  Their
abundance at the  stations sampled was quite variable.  Atypically high
abundance was  found  at Station 36, near the mouth of the Au Gres River.
Green and  blue-green algae  continued to increase  in abundance, particularly
at  stations  in  segments 1 and 3 of  the  sampling array.   Representatives  of
 the flagellate  groups remained most abundant at stations  in the lower bay.

     The next  sampling cruise began 25 June (Fig.  19).   By  this time  total
 phytoplankton  abundance had been somewhat reduced at most open-water
 stations,  although high total numbers were  found  at a number of nearshore
 stations.   The  abundance of diatoms was much reduced, except at stations  in
 and near  the Saginaw River  and at nearshore Stations 36  and 53.  Green  and
 blue-green  algae  were abundant at most  stations  in  the  lower bay and  a
 particularly high abundance of this group was  again noted at Station  34,  in
 Wild Fowl  Bay.   Flagellates remained abundant  and were  somewhat more
 generally  distributed  than  was  the  case  in  the  previous  cruise.
                                       23

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hJ
-p-
                 Figure 15.  Distribution of major phytoplankton groups in Saginaw Bay for cruise

                                               beginning 8 April  1975.

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S3
Ln
                 Figure  16.   Distribution  of major  phytoplankton  groups  in Saginaw Bay for cruise
                                              beginning  28  April  1975.

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Figure 17.  Distribution of major phytoplankton groups  in Saginaw Bay  for  cruise
                              beginning  20 May 1975.

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Figure 18.   Distribution of major phytoplankton  groups  in  Saginaw  Bay  for  cruise
                              beginning 5  June 1975.

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NJ
OO
                 Figure 19.  Distribution of major phytoplankton groups in Saginaw Bay for cruise
                                              beginning 25 June  1975.

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     During the next cruise, which began 11 July, there was a rather striking
floristic differentiation between the inner and outer segments of the bay
(Fig. 20).  During this sampling period total phytoplankton abundance was
markedly lower at stations southwest of Charity Island than in the outer bay.
This trend is accentuated in some of the major phytoplankton groups.  Diatoms
were a relatively minor element of the flora during this cruise and there are
two regions of greatest abundance.  One is in the Saginaw River and
immediately adjacent stations.  The other is in the outer bay.  The species
composition of these two regions is almost entirely different.  In the other
major groups high abundance is restricted to stations in the lower bay.
Green algae are abundant during this sampling period and are generally
distributed at stations in the lower bay.  The blue-green algae were the
dominant element of the flora in terms of peak abundance, but high numbers,
particularly of heterocyst-forming taxa, were more restricted to nearshore
areas.  The occurrence of blue-green algae at Stations 44 and 53, along  the
southern coast, indicates that these populations may have been transported
toward Lake Huron by shoreline drift.  With the exception of one station, the
flagellates constitute a relatively minor fraction of the flora and the
populations present are largely restricted to the lower bay.

     The next series of samples was taken beginning 29 July (Fig. 21).
Although total phytoplankton abundance had increased substantially by  the
time these samples were taken, distribution of the major groups was somewhat
similar to that observed during the previous cruise.  The abundance and
distribution of diatoms was even more strikingly disjunct than it had  been
the  previous month.  Relatively high abundance was found in the Saginaw  River
and  at stations in segment 4, but the abundance of this group was low  in the
rest of the bay.  As was the case the previous month, different species
occupied  the two regions of maximum abundance.  Although green algae were not
as abundant as diatoms, significant populations were present at most stations
in the lower bay and at Stations 43 and 44 and 52 and 53 along the  southern
shore of  the outer bay.  The distribution of blue-green algae was somewhat
irregular during this  sampling period, but very  large abundances were  found
at some stations.  Their distribution followed the same general pattern  as
the  green  algae, although large populations of heterocyst-forming species
were  found only at shoreward stations along the  southern coast of the  bay.
Flagellates were present  in relatively low abundance and the populations
present were remarkably evenly distributed.  Relatively high abundance of
organisms  in this group was found at stations  in  the Saginaw River.

     The  next  cruise  in this sequence began 18 August  (Fig. 22).  Maximum
total  phytoplankton abundance declined from levels observed during  the pre-
vious  sampling  period.  Greatest  total phytoplankton density as  found  at sta-
tions  in  segments 3 and 5,  along  the southeastern coast of  the bay.
Blue-green algae were  the dominant  element of  the flora at  this  time  and were
particularly abundant  in  this region.  The distribution of  green  algae was
somewhat  more  uniform, and  sizable  populations of representatives of  this
group  were  found  at most  stations  in the  lower bay.  Highest green  algal
abundance  occurred  at  stations just off  the mouth of  the Saginaw  River.   The
abundance  of diatoms  was more uniform  than  it  had been  the  previous month,
but  there  was  still a  large difference  in  the  species  composition of
different  areas.  Populations  in  the outer bay were mostly  oligotrophic

                                       29

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Figure 20.   Distribution of major phytoplankton groups  in Saginaw Bay for cruise
                             beginning 11 July 1975.

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Figure 21
Distribution of major phytoplankton groups in Saginaw Bay for cruise
                 beginning 29 July  1975.

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Figure 22.  Distribution of major  phytoplankton  groups  in Saginaw  Bay  for  cruise
                            beginning 18 August  1975.

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species common in the Lake Huron flora.  Populations in the inner bay were
mostly species which thrive under eutrophic conditions and the populations in
the Saginaw River were taxa tolerant of extreme eutrophication and elevated
salinity.  As had been the case during the previous sampling, flagellates
were a relatively minor constituent of the total phytoplankton assemblage and
largest populations were found at stations near the mouth of the Saginaw
River.

     The next sampling was undertaken beginning 3 September (Fig. 23).
Maximum total phytoplankton abundance again increased and the flora was
dominated by extremely large concentrations of green and blue-green algae,
particularly at a series of stations in the vicinity of Sand Point.  The
distribution of diatoms was essentially opposite that of the green and
blue-green algae, with greatest abundance of this group occurring at stations
along  the northern coast of the bay.  Some diatom populations were present at
all stations sampled, but there again was a large qualitative difference  in
the diatom floras of different parts of the bay.

     Only a very limited number of  stations were sampled during  the next
cruise, which began 23 September (Fig. 24), due to  adverse weather
conditions.  The stations sampled were all in the northern half  of the bay,
in segments 1, 2, and 4.  Based on  this subset, total phytoplankton abundance
appeared to decline.  Diatoms were  most abundant, although significant
populations of blue-green algae were present at stations in the  inner bay.
The abundance of green algae was much reduced and large populations were
noted  only at Station 30.  Flagellates were a minor element of most
assemblages sampled.  They were most abundant at stations in the Saginaw
River  and, as was also the case with the diatoms, different populations were
present  in the river and lower bay  than in the outer bay.

     During the next sampling cruise, which began 9 October (Fig. 25),
phytoplankton distribution in the bay was atypical, compared to  other months
sampled.  Total phytoplankton abundance increased,  and green algae were  the
dominant element of  the  flora at most  stations sampled.  Large populations
were  present  in the  Saginaw River and  at shoreward  stations along the
southern coast and  this  group was atypically abundant at all stations sampled
except for three stations in the Tawas Bay area.  Blue-green algae were  also
relatively abundant  in the lower bay and significant populations occurred
even  at  the outermost line of stations sampled.  During this sampling period
the  total abundance  of diatoms was  relatively uniform throughout the bay, but
different species occupied different regions within the bay.  Large
populations of species usually associated with more oligotrophic or open  lake
conditions were noted in the Tawas  Bay area.

      During  the next  sampling period,  which began 27 October (Fig. 26),
several  stations  in  segment 3, which usually have high  levels of
phytoplankton  standing crop, were not  sampled.  The omission of  these
stations was  particularly unfortunate  in  this case  because  the highest
abundance of  total  phytoplankton was found at stations  bordering the area
which  was not  sampled, and  it  is  quite likely that  the  highest  levels of
phytoplankton  abundance  in  the entire  bay  actually  occurred  in  the area
represented  by  the  missing  stations.   This  supposition  is  supported,  to  a

                                       33

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Figure 23.  Distribution of major phytoplankton  groups  in  Saginaw Bay for cruise
                           beginning 3 September 1975.

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u>
Ol
                                                                                                    0 L
                 Figure  24.   Distribution of major  phytoplankton groups  in  Saginaw Bay for cruise

                                           beginning 23  September  1975.

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UJ
                 Figure 25.  Distribution of major phytoplankton groups in Saginaw Bay for cruise
                                             beginning 9 October 1975.

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Co
                Figure 26.  Distribution of major phytoplankton groups in Saginaw Bay for cruise
                                            beginning 27 October 1975.

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certain extent, by the distribution of the major phytoplankton groups.  Green
and blue-green algae are atypically abundant at Stations 42, 43, and 44,
which may indicate that these populations are being generated in the
unsampled area along the southern coast, as was the case in several previous
cruises, and then transported to these stations.  The trend in diatom
abundance at these stations is opposite that of the heterocyst-forming
blue-green algae.  Diatoms are relatively evenly distributed at the stations
sampled, compared to other groups of phytoplankton, but different species
were present in the outer bay than in the inner bay.  Conditions at Stations
42, 43, and 44 are apparently less conducive to the growth of diatom species
occurring in the lower bay than to the green and blue-green algae.  The
distribution of flagellates during this sampling period is highly atypical.
Large populations occur in the Saginaw River, but they are a minor component
of phytoplankton assemblages in the rest of the bay.

     More complete sampling was achieved during the next cruise, which began
16 November, although some stations along the southeastern shore of the bay
were again omitted (Fig. 27).  By this time, total phytoplankton abundance
had increased  somewhat at the stations sampled, and the abundance of
phytoplankton  was remarkably uniform throughout the bay.  The distribution of
major groups during this period was unusual.  Green algae were unusually
abundant at this time and very large populations were present at stations in
the outer bay, including some stations in the Saginaw Bay-Lake Huron
interface region.  Relatively low abundance of  this group was found at
stations in the lower bay, particularly those in the immediate vicinity of
the Saginaw River discharge.  The trend in distribution of  this group  is thus
essentially opposite  that observed during most  other cruises.  The
distribution of blue-green algae was somewhat similar, although the
occurrence of  representatives of this group were so scattered that any  trend
is somewhat obscured.  The abundance of diatoms was again fairly uniform
throughout the bay but different populations were characteristic of different
areas of the bay.  Flagellates remained abundant in the Saginaw River,  but
were relatively more  abundant at other stations than they had been the
previous month.  As was the  case with the diatoms, different species occurred
in the  river than in  the rest of the bay, and there was further differ-
entiation between stations in the inner bay and stations  in the Lake Huron
interface region.

     The next  sampling  cruise began  16 December (Fig. 28).  Due to adverse
weather conditions only a  limited number of stations were sampled, all  in the
inner bay.  Total phytoplankton abundance at the stations sampled was
drastically reduced  from levels observed the previous month.  Diatoms  were
the dominant element  of the  flora, although significant populations of green
and blue-green algae  were  found at some stations.  Not enough stations  were
sampled to establish  regional trends.

     A  similar limited  array of stations was sampled during the next  cruise,
which began 27 January  1976  (Fig. 29).  Total phytoplankton abundance  was
further reduced, but  there was a trend  for  highest  total  phytoplankton
abundance  to occur  at stations  in segment 3.  The main group contributing to
this  pattern was  the  green algae which  were  the dominant  element  of the flora
during  this period.   Blue-green algae without heterocysts and  flagellates had

                                       38

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Figure 27.   Distribution of major  phytoplankton  groups  in  Saginaw Bay  for  cruise
                           beginning 16 November 1975.

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Figure 28.  Distribution of major phytoplankton  groups  in  Saginaw Bay for cruise
                           beginning 16 December 1975.

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Figure 29.  Distribution of major phytoplankton  groups  in Saginaw Bay for cruise
                            beginning 27 January 1976.

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similar distribution patterns to the green algae, although they were minor
components of the flora at this time.  Heterocyst-forming blue-green algae
were very rare.  Diatoms were the second most abundant of the major groups
and the trend in abundance of this group was opposite the others.

     Seasonal low in total phytoplankton abundance was found on the next
cruise, which began 11 March 1976 (Fig. 30).  The abundance of total
phytoplankton was low at all stations sampled and abundance was fairly
uniform.  The same series of stations was sampled as in the previous month.
Only scattered populations of green and blue-green algae were noted, with
most occurrences at nearshore stations.  Heterocyst-forming blue-green algae
were not noted in any of the samples from this cruise.

     During the next cruise, which began 27 April (Fig. 31), and  in
subsequent cruises in the sequence, the array of stations sampled  in the
project was reduced.  Fewer stations were sampled in the lower bay and
intermediate lines of stations in the outer bay were eliminated.   This
reduction in station density, and particularly the elimination of  stations  in
the transitional zone between the lower bay and the Lake Huron interface,
considerably reduced resolution in detecting trends in phytoplankton
abundance.  During the 27 April cruise total phytoplankton abundance
increased with highest total abundance occurring at stations in mid-bay.  The
flora was dominated by diatoms but green algae were an important  element of
assemblages at several stations in the lower bay.  Flagellates were widely
distributed, but their abundance was less than diatoms or green algae and,  as
had been the case in several previous cruises, the trend in abundance of
flagellates tended to be opposite the trend in abundance of diatoms at
stations in the lower bay.  At stations in the Lake Huron interface region
the abundance  trends of  these two groups were similar.

     There was a very striking difference in the abundance and species
composition of phytoplankton assemblages collected at  stations in the Lake
Huron  interface region versus other  stations sampled  in the bay during the
next cruise, which began 12 May (Fig. 32).  The apparent difference was
enhanced by the fact that the intermediate line of stations was not sampled,
as  it had been in previous years.  The differences in  abundance and species
composition were, however, larger than had been observed in previous spring
sampling periods.  Diatoms were the  dominant element  of the flora at most
stations sampled, although green algae were very abundant at a few mid-bay
stations.  Highest numbers of flagellates and blue-green algae were found at
a  line  of stations southwest of Charity Island.  Although the  flagellate
groups  were considerably more abundant than blue-greens, the similarity  in
distribution was striking.

     Only a limited number of stations were sampled on the next cruise,  which
began  1 June (Fig. 33),  due  to adverse weather conditions.  All of the
stations sampled were  in the lower bay.  Total phytoplankton abundance
increased at these stations, and extremely dense populations of green algae
were noted at  stations  in the vicinity of the Saginaw River mouth.  Diatoms
remained relatively abundant as did  flagellates, and  atypically  large
populations of flagellates were  found  at stations  in  the Saginaw  River.
Blue-green algae were a  fairly minor component of  the  flora and  their


                                      42

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Figure 30.  Distribution of major phytoplankton groups in Saginaw Bay for cruise
                             beginning 11  March 1976.

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Figure 31.  Distribution of major phytoplankton  groups  in  Saginaw  Bay  for  cruise
                             beginning  27 April  1976.

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Figure 32.  Distribution of major phytoplankton groups  in  Saginaw Bay  for cruise
                              beginning  12 May  1976.

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Figure 33.  Distribution of major  phytoplankton groups in Saginaw Bay  for  cruise
                              beginning 1 June 1976.

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distribution was scattered.  Highest numbers of heterocyst-forming blue-
greens were found at stations near the Saginaw River mouth which had highest
total phytoplankton abundance and highest abundance of green algae.

     More complete sampling was obtained on the next cruise, which began
18 June (Fig. 34).  Maximum total phytoplankton abundance was reduced from
the extreme levels noted the previous month.  Diatoms remained an important
element of assemblages at most stations sampled, although their abundance
relative to other groups was reduced.  Highest numbers of diatoms were found
at a station in the Saginaw River.  As had been the case in most previous
sampling periods, the species composition of the river station was
substantially different from stations in the bay.  Green algae, flagellates,
and blue-green algae all increased in importance.  Greens and blue-greens
tended to be most abundant at stations along the southern coast of the bay
while the flagellate groups tended to be most abundant at stations in the
northern sector of the lower bay.  During this sampling period many
populations of green and blue-green algae characteristic of eutrophic water
and generally abundant at  stations in lower Saginaw Bay were found at the
most southerly station in  the Lake Huron interface.  It appeared that these
populations were being advected out of the bay along the southern shore as
had been the case in several other summer cruises.

     During  the next cruise, which began 8 July (Fig. 35), much higher total
phytoplankton abundance was observed, particularly at stations in the lower
bay.  Blue-green algae were the dominant component of the flora in the lower
bay.  Heterocyst-forming species were a relatively minor fraction of the
total blue-green algae observed, but  they were fairly abundant at Stations
13, 24, and  33.  Green algae were also very abundant in the lower bay.
Numbers of diatoms reduced at roost stations sampled but large populations
were present in the Saginaw River and at Station 13 near the mouth of the
river.  The  species present at these  stations were mostly small Gentries
tolerant of  high conservative ion levels and extremely eutrophic conditions.
During this  sampling period there was little evidence of dispersal of
populations  generated in the lower bay into Lake Huron.  Green algal
abundance was higher at Station 52 than at other stations in the Lake Huron
interface, but other groups did not show this distribution  pattern.

     During  the next cruise, which began 28 July (Fig. 36), the same general
pattern of distribution was observed.  Total phytoplankton  abundance
continued  to increase in the lower bay, and there was an extreme difference
in both abundance and species composition between stations  in the  lower bay
and stations in  the Lake Huron interface region.  Blue-green algae continued
to be  the  dominant element of assemblages at stations in the lower bay,
particularly at  stations in the southeastern quadrants.  Green algae
increased  in relative and  absolute abundance and the distribution  pattern  of
this  group was  similar  to  that of the blue-green algae.  The abundance of
diatoms  and  flagellates  increased somwhat at stations in the open  bay  from
 levels observed  during  the previous  sampling period.  The abundance  patterns
 for these  groups  were opposite those  of  the green and blue-green algae.  As
had been  the case  previously, diatom  abundance was highest  in  the  Saginaw
River, but  the  species  composition at  this  station was strikingly  different
 from that  found  at  stations  in the open waters of the bay.  Populations

                                      47

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/ '

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Figure 35.  Distribution of major phytoplankton groups  in Saginaw Bay for cruise
                              beginning 8  July  1976.

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Figure 36.  Distribution of major phytoplankton groups  in  Saginaw Bay for cruise
                             beginning 28 July 1976.

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present at stations in the Lake Huron interface region were different from
those found at stations in the lower bay.

     This situation had changed somewhat by the time the next sampling cruise
was undertaken, beginning 11 August (Fig. 37).  Average total abundance of
phytoplankton declined, but there was a marked increase in abundance at
stations in the Lake Huron interface region.  Unlike previous cruises,
highest total phytoplankton abundance was found at stations on the northern
end of the outer transect.  Assemblages in the lower bay continued to be
dominated by blue-green and green algae, but  the abundance of diatoms
increased, particularly at stations in the central segment of the bay.  There
was more similarity in assemblage composition between stations in the lower
bay and those in the Lake Huron interface region than was the case in most
cruises.  Heterocyst-forming blue-green algae were much more abundant at
stations in the lower bay, but small populations of the same species were
found at stations  in the Lake Huron interface.  The same situation was
typical of other groups as well.  The diatom  and green algal flora of the
Saginaw River remained distinct, but there was an unusual degree of
similarity in species composition at all other stations sampled.  Although
the same suite of  species was present, abundance of the flagellate groups
tended to run counter to the trend of the other major groups.  The inverse
relationship between the abundance of green algae and flagellates was
particularly notable.

     A somewhat more typical pattern was observed during the next sampling
period, which began 31 August (Fig. 38).  Total phytoplankton abundance
increased at stations in the lower bay, but decreased slightly at stations  in
the Lake Huron interface region.  Although there was some overlap of
populations between the two regions, differences were much greater than  they
had been earlier in the month.  Blue-green algae continued to dominate the
flora at  stations  in the lower bay, and green algae were an  important
component of assemblages sampled in this region.  Limited numbers of greens
and blue-greens were found  in samples from the outer line of stations, and
highest abundance  was noted at the northernmost and southernmost shoreward
stations on this transect.  Although this type of pattern might be expected
to occur  routinely, this was one of the  few instances in which it was
observed during the period  in which we  sampled the bay.  The abundance of
diatoms generally  decreased, but their  total  abundance was more uniform  than
it was during  the  previous  sampling period.   Distinct suites of populations
were again present at stations in the Saginaw River, the lower bay,  and  the
Lake Huron interface region.  Flagellates were most abundant at stations  on
the  north  side of  the bay and the general pattern of abundance of this group
tended  to  be  opposite  the abundance pattern of diatoms.

     The  next  cruise  in the sequence began  18 September  (Fig. 39).   Total
phytoplankton  abundance was reduced slightly, although high  numbers  were
present  at most stations  in the  lower bay.  The  flora of the lower bay
continued  to  be dominated by blue-green and green algae.  The abundance  of
diatoms was  remarkably uniform throughout the bay, but very  high numbers  were
present  at the  station sampled  in  the Saginaw River.  Although numbers were
similar,  the  species  composition of assemblages  in the river, the  lower  bay,
and  the  Lake  Huron interface region was  greatly  different.   During  this


                                      51

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Figure 37.   Distribution of  major phytoplankton groups in Saginaw Bay for cruise
                            beginning 11 August  1976.

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Ol
1-0
                 Figure 38.  Distribution of major phytoplankton groups in Saginaw Bay for  eruise
                                              beginning  31  August  1976.

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Ul
-p-
                 Figure 39.   Distribution of major phytoplankton groups in Saginaw Bay for cruise

                                            beginning  18 September 1976.

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sampling period the abundance trends in the flagellate groups were similar to
those of the green and blue-green algae but the difference in species
composition in different regions was similar to that found in the diatoms.

     Although some stations were omitted from the next sampling round, which
began 7 October (Fig. 40), a reasonable coverage of the bay was obtained.  On
the basis of these samples, phytoplankton distribution within the bay was
substantially similar to the case observed the previous month.  Total
phytoplankton abundance was slightly reduced, but very high total abundance
was noted at several stations in the inner bay.  Blue-green and green algae
continued to dominate the flora, although population distribution was even
more erratic than had been the case previously.  Diatoms were again most
abundant in the Saginaw River, with relatively uniform numbers throughout the
open waters of the bay.  The marked distinction in the species composition of
assemblages found in the river, the lower bay, and the Lake Huron interface
stations was maintained.  A larger proportion of species tolerant of
hypereutrophic conditions, which were usually found at stations in the inner
bay, occurred at Stations 51 and 52 on the southeastern end of the outer
transect of stations.  These stations also contained a higher proportion of
blue-green and green algae than the other stations on this transect, which is
probably indicative of transport of water masses derived from the lower bay
along  the southern shore.

     The final cruise in the project began 10 November (Fig. 41).  Due to
weather conditions at this time of year, a limited number of stations were
sampled, mostly in the inner bay.  Total phytoplankton abundance declined
slightly at the stations sampled, and the distribution of major phytoplankton
groups  in the inner bay was quite unusual.  Extreme abundance of green algae
was noted at Station 56, north of Fish Point.  Although representatives of
this group were present at the other stations sampled, population densities
did not approach those found at Station 56.  The next highest abundance of
green  algae was found at stations near the mouth of the Saginaw River.
Similar species were present at these stations and it is possible that the
very high abundance of green algae at Station 56 is related  to the output of
the Saginaw River.  Blue-green algae, on the other hand, were much more
abundant at stations in the northern sector of the lower bay.  Blue-green
populations consisted of mostly non-heterocyst-forming species, although
relatively  low levels of species with heterocysts were  found  at stations  in
the  inner bay.  During this sampling period the distribution of diatoms ran
counter  to  the trend observed  for the blue-green algae.  The highest
population  levels  observed were found in the Saginaw  River,  but nearly equal
population  densities were  found at stations  in the inner bay.  The highest
abundance of diatoms occurred  at stations  in the southern  sector of  the  lower
bay.   During this  sampling period flagellates were present  in minimal
abundance and  total  abundance  of the group was quite  similar  at all  stations
in  the inner bay.
                                 DISCUSSION

      Taken  in  its  entirety,  the  phytoplankton  flora  of  Saginaw Bay is
 extremely diverse  (Appendix  l).  The  species encountered  in the bay span the

                                      55

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Ln
cr>
                Figure 40.   Distribution of major phytoplankton  groups  in  Saginaw Bay for cruise
                                             beginning 7 October 1976.

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Ol
--J
                 Figure 41.  Distribution of major phytoplankton groups in Saginaw Bay for cruise
                                            beginning  10 November 1976.

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entire range of ecological adaptations found in the modern Great Lakes, with
the exception of populations specifically adapted to very oligotrophic
conditions.  Part of this variability results from the large number of
quasidiscrete habitats present within the bay.  There are a large number of
shallow, very productive areas which may produce local blooms of particular
species which are later entrained into the general water mass and physically
mixed with other populations.  There are a number of examples of intense
local blooms of particular populations at a particular station or at a  few
stations within a local region.  This type of occurrence is most visible in
the earlier sampling rounds which included more stations and particularly
more stations relatively near to shore.  The high productivity potential,
particularly in the inner bay, can lead to extreme local differences in both
the numbers and kinds of phytoplankton present.  This extreme regional
patchiness is one of the outstanding characteristics of phytoplankton
distribution within the bay.

     The overall diversity of the flora also partially results from the fact
that the flora of the bay at any given point in time may be a composite of
populations developed under different conditions.  The most obvious source of
atypical populations is Lake Huron.  Under certain conditions it appears that
the Lake Huron water mass extends a considerable distance into the bay.
Apparent cases of this situation occurred in April, June, and September 1974
and July and October 1975.  In these cases it appeared that a "wedge" of Lake
Huron water extended into the bay.  In other cases disjunct populations of
species usually associated with the offshore waters of Lake Huron were  noted
at mid-bay stations.  The only apparent explanation for such occurrences is
that these populations were entrained  in a deep-running counter current of
Lake Huron water which entered the bay and subsequently welled up in the
mid-bay region.

     Another source of populations adapted to conditions at the other end of
the spectrum of chemical conditions is the Saginaw River.  In most cases
studied, the flora of the river was dominated by species tolerant of highly
eutrophic  conditions and extremely high conservative  ion concentrations.  The
most characteristic populations were several  species  of small centric
diatoms, including Cyclotella atomus, £. cryptica, Sceletonema potomos, and
J5. subsalsa.  The flora of  the river was generally distinct from  that of the
open bay.  It appears that  populations in the river are rarely, if ever,
nutrient limited.  Large diatom populations were maintained throughout  the
summer  and heterocyst forming blue-green algae were rarely abundant at
stations in  the river.  In  some instances, populations usually associated
with the river were major dominants at stations  in the vicinity of the  river
mouth  and  smaller numbers of  these populations were occasionally  found  at
stations throughout the lower bay.

     A third source of assemblage heterogeneity  particularly  important  in
Saginaw Bay  is  the periodic  entrainment of benthic populations.   Although
this mechanism  is less well  documented,  it  is quite probably  an  important
factor  in  the ecology of  the  region because  it  furnishes a direct linkage
between the  sediment  sink  for nutrients and  toxicants and planktonic  food
webs.   Several  distinctive  types of populations  are involved.  The most
conspicuous  elements  of this  flora are large  pennate  diatoms.  Some of  the


                                      58

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characteristic populations are Calone is amphisbaena, Nitzschia sigma,
N. sigmoidea, and several members of the _N. tryblionella complex, Surirella
angusta, _S_. ovalis,  and several members of the j^. ovata complex.  Although
these species are rarely numerical dominants, they are large cells and they
may constitute an appreciable fraction of the biovolume at stations  in the
inner bay.  They are all apparently tolerant of highly eutrophic conditions
and high levels of conservative ion contamination.  Although there is
admittedly little direct evidence to demonstrate it, we also suspect that at
least some of the filamentous green and blue-green algal populations which
are dominant populations in the bay may be derived from benthic habitats.
These populations occasionally have very erratic distribution patterns,
especially early or late in the season.  They also often contain abundant
polyphosphate bodies, indicating growth under high nutrient and/or stress
conditions.

     Another group of organisms important in Saginaw Bay, with a similar type
of meroplanktonic growth cycle, are several species of diatoms which have
become noted indicators of eutrophication in the Great Lakes.  Included  in
this group are species such as Actinocyclus normanii fo. subsalsa and
Melosira granulata.  These species are planktonic in the sense that  they have
no apparent special adaptation to benthic existence.  They, however, are very
heavy-walled forms.  They also apparently have a relatively high temperature
requirement  in that they are generally most abundant in the summer and  fall.
Such species are usually not successful  in the offshore waters of the Great
Lakes because they are very susceptible  to sinking  losses, and nutrient
supply  is  limited during summer stratification.  They do become dominant
populations  in areas such as Saginaw Bay, lower Green Bay, and western  Lake
Erie.   In  these  relatively shallow areas wind-induced mixing can furnish
sufficient turbulence to resuspend populations and  at the same time  reentrain
nutrients  from the near bottom waters.   Although it has not been widely
reported  in  the  literature, our results  indicate that such populations  may be
able to  store internal phosphorus, in  the  form of polyphosphate  bodies,  far
in excess  of  their immediate requirements.  The  clearest evidence for  this  is
found in Fragilaria capucina, another meroplanktonic species which  is  often  a
dominant  form in highly enriched  regions of  the  Great Lakes.   It differs  from
the  species  discussed above  in the fact  that  it  is  apparently  tolerant  of  low
temperatures  and is usually most  abundant during spring mixing.  As  discussed
later,  this  species has a much larger  fraction of its cellular volume  in
silica  frustule  than is the case  with  species  such  as Stephanodiscus
binderanus and other euplanktonic  forms  which  bloom under eutrophied
conditions.  Although Fragilaria  capucina  can  store excess phosphate,  its
dispersion is limited by  large sinking  losses, except under  ideal conditions.
On the  basis  of  our data,  it appears  that  the  dispersion of  populations such
as Actinocyclus  normanii  fo. subsalsa  and Melosira  granulata  is  even more
limited,  although they may be dominant  populations  in the bay  under  ideal
conditions.

     All  of  the  above  factors  tend to  modify  phytoplankton responses to the
overriding factor of extreme nutrient  loading  to  the bay.  It  is clear  that
excessive  phosphorus loads lead  to silica  limitation and  consequent  reduction
in diatom growth during  the  summer.   It  is  also  clear that at  least  transient
nitrogen limitation  occurs,  favoring  the growth  of  heterocyst  forming


                                      59

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blue-green algae.  On the basis of our results, however, it is apparent that
physical events can act to de-couple nutrient loads from the directly
expected physiological response of phytoplankton within the bay.

     The general pattern of phytoplankton succession in the bay is less well
defined than it is in more stable systems, but the following sequence appears
to be characteristic.  Phytoplankton assemblages in the bay are dominated by
diatoms and flagellates during the winter circulation.  Occasional
populations of green and blue-green algae are noted, but these groups are
generally a minor component of the total assemblage.  With increased
insolation during the spring, total phytoplankton abundance increases,
forming the strong spring bloom characteristic of eutrophic systems.  The
timing of the maximum spring bloom appears to be variable from year to year
and is undoubtedly controlled by the extent of ice cover in the bay and
turbidity immediately following break-up of the seasonal ice cover.  As soon
as the water column begins to stabilize, the spring dominant diatom
populations rapidly become silica limited, allowing increasing abundance of
phytoplankton groups which do not require silica for reproduction.
Phytoplankton succession then proceeds along the path from dominance by green
algae and non-heterocyst-forming blue-green algae toward large populations of
nitrogen-fixing blue-greens.  It should be emphasized, however, that the
timing of this sequence and the absolute "switch-over" of physiological
groups characteristic of smaller hypereutrophic lakes is not so clear-cut in
Saginaw Bay.  In Saginaw Bay the normal course of events appears  to be a
return to a more mixed  flora in the late summer and early fall.   During this
period three distinctive thermophilic diatom associations may develop in
different regions of the bay.  The Saginaw River and stations directly under
the influence of its plume develop an association characterized by
Thalassiosira, Stephanodiscus, and Cyclotella species tolerant of high
temperature, high nutrient and conservative ion levels, and relatively high
turbidity.  The extent  of penetration of these populations into the open
waters of the bay is highly variable, but some species are commonly found at
stations  throughout  the lower bay.  The lower and mid-reaches of  the bay
develop a substantially different association, dominated by species of
Actinocyclus and Melosira, as discussed earlier.  In several instances late
summer diatom blooms were also noted at stations in the Lake Huron  interface
region.  Although assemblages  in this region may contain some of  the species
found  further down  in  the bay, they are generally dominated by blooms of
Cyclotella  comensis.  This species has recently become much more  abundant in
the upper Great Lakes.  In recent years massive, auxospore forming, summer
blooms of this species  have been noted in the Saginaw Bay  interface and other
relatively  heavy-nutrient-load localities (e.g., Thunder Bay).  The species
has not been widely  reported from the United States, but it apparently has a
high nitrogen  requirement and  is especially efficient at uptake of  silica at
low concentrations.

     The  most  plausible explanation  for  this somewhat atypical  temporal
sequence  of major physiological groups is recycling of nutrients,
particularly silica, which were earlier  sequestered during the  spring bloom.
This explanation  is  supported  by the results of Smith et al. (1977), which
show a detectable  increase  in  soluble reactive Si02 during late summer and
early  fall.  Direct  measurements of  silica recycle  from Saginaw Bay sediments


                                     60

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(J. A. Robbins, personal communication) show rates which are consistent with
the hypothesis of substantial silica resupply during this period.  It is
interesting to note that this apparent nutrient resupply affects both the
composition of the Saginaw Bay flora and the growth potential of populations
more characteristic of open lake conditions which occur in the Saginaw Bay
interface region.

     One of the most crucial points in this investigation is the degree and
intensity of effect on Lake Huron resulting from loadings and biological
processes in Saginaw Bay.  Our results indicate that substantial effects are
present, but that the region and intensity of effect is highly variable.

     In the average case it appears that the southern coast of Saginaw Bay is
most strongly  impacted and that export of phytoplankton populations
associated with highly eutrophic conditions usually occurs through the region
represented by the shoreward stations  in region 5.  This is the case which
would be expected from consideration of circulation in the bay under average
wind conditions (Allender, 1975; Danek and Saylor, 1977).  As Danek and
Saylor (1977)  emphasized, actual circulation patterns within the bay are
highly variable and show rapid response to both variations to forcing by
ambient wind fields and the general circulation of Lake Huron.  This
instability is reflected by phytoplankton distribution.  It is quite clear
that meteorological conditions can have a strong influence on the eventual
fate of materials entering the bay and on the fate of phytoplankton
populations generated by nutrient loadings.  In this context, further
research should be devoted to the effects of conditions which force strong
advective events on processes in Lake  Huron.  The results of Stoermer and
Kreis  (1980) are in agreement with our observations of typical distribution
patterns in the Saginaw Bay-Lake Huron interface region.  Their  results show
a  general pattern of effects southward along the Michigan coast with large
variations in  the area of Lake Huron showing floristic similarities to
Saginaw Bay.   In one instance this general pattern is reversed with materials
advected from  Saginaw Bay apparently being dispersed northward.  Their
results also show that, under certain  conditions, populations such as
Aphanizomenon  flos-aquae which were most probably generated  in Saginaw Bay
may be  transported into the  international waters of Lake Huron.
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                    INTRODUCTION AND  SECTION  1 REFERENCES
Allender, J. H.  1975.  Numerical simulation of circulation and advection-
     diffusion processes in Saginaw Bay, Michigan.  Ph.D. Dissertation,
     University of Michigan, Ann Arbor.

Bierman, V. J., D. M. Dolan, E. F. Stoermer, J. E. Gannon, and V. E. Smith.
     1980.  The development and calibration of a spatially-simplified
     multi-class phytoplankton model for Saginaw Bay, Lake Huron.
     Great Lakes Environmental Planning Study Contribution No. 33, 126 pp.
     Great Lakes Basin Commission, Ann Arbor, Michigan.

Danek, L. J., and J. H. Saylor.  1977.  Measurements of the summer currents
     in Saginaw Bay, Michigan.  J. Great Lakes Res. 3: 65-71.

Freedman, P. L.  1974.  Saginaw Bay:  An evaluation of existing and histori-
     cal conditions.  U.S. Environmental Protection Agency, Region V,
     Enforcement Division.  137 pp.

Gannon, J. E., F. J. Bricker, and K. Bricker.  In preparation.  Spatial and
     seasonal structure of crustacean zooplankton communities  in Lake Huron.
     U.S. Environmental Protection Agency, Ecological Research Series.

International Joint Commission.  1976.  The waters of Lake Huron and Lake
     Superior.  Vol. I.  Summary and recommendations.  International Joint
     Commission, Windsor, Ontario.  236 pp.

Lohmann, H.  1908.  Untersuchungen zur Festellung des vollstandigen Gehaltes
     des Meeres an Plankton.  Wiss. Meeresuntersuch.  Abt. Kiel, N.F.,
     10:  131-370.

Richardson, W. L.  1974.  Modeling chloride distribution  in Saginaw Bay.
     Proc. Seventh Conf. Great Lakes Res.  International  Association for
     Great Lakes Research.  pp. 462-470.

Schelske, C. L., L. E. Feldt, M. S. Simmons, and E. F. Stoermer.  1974.
     Storm  induced relationships among chemical conditions and phytoplankton
     in  Saginaw Bay and western Lake Huron.  Proc. Seventeenth Conf. Great
     Lakes Res., International Association  for Great Lakes Research.
     pp.  78-91.
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                 E. F. Stoermer, J. E. Gannon, and M. S. Simmons.  1976.
     Biological, chemical and physical relationships in the Straits
     of Mackinac.  U.S. Environmental Protection Agency, Ecological Research
     Series EPA-600/3-76-095.  U.S. Environmental Protection Agency,
     Duluth, Minnesota.  267 pp.

	, R. A. Moll, and M. S. Simmons.  1980.  Limnological condi-
     tions in southern Lake Huron, 1974 and 1975.  U.S. Environmental Pro-
     tection Agency, Ecological Research Series.  EPA 600/3-80-74.  178 pp.

Smith, V. E., K. W. Lee, J. C. Filkins, K. W. Hartwell, K. R. Rygwelski and
     J. M. Townsend.   1977.  Survey of chemical  factors in Saginaw Bay (Lake
     Huron).  U.S. Environmental Protection Agency, Ecological Research
     Series EPA-600/3-77-125.  143 pp.

Stemberger, R. S., J.  E. Gannon, and F. J. Bricker,  1979.  Spatial and
     seasonal structure of rotifer communities in Lake Huron.  U.S.
     Environmental Protection Agency, Research Reporting Series
     EPA-600/3-79-085.  160 pp.

Stoermer, E. F., and R. G. Kreis.  1980.  Phytoplankton composition and
     abundance in southern Lake Huron.  Univ. Michigan, Great Lakes Res.
     Div., Spec. Rep.  No. 65.  382 pp.

	, L. Sicko-Goad, and D. Lazinsky.   1980.  Synergistic ef-
     fects of phosphorus and trace metal  loadings on Great Lakes  phyto-
     plankton.   pp. 171-186.  Proc. Symposium on the Theoretical  Aspects of
     Aquatic Toxicology.  Borok, Jaroslav., USSR.  U.S. Environmental
     Protection  Agency, Research Reporting Series.  EPA 600/9-80-034.

Strathmann, R. R.   1967.  Estimating  the  organic carbon content of  phyto-
     plankton from  cell volume or plasma volume.  Limnol. Oceanogr.
     12: 411-418.

Vollenweider, R. A., M. Munawar, and P. Stadelmann.  1974.  A comparative
     review of phytoplankton and primary  production in the Laurentian
     Great Lakes.   J.  Fish.  Res. Board Can. 31:  739-762.
                                     63

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                                 SECTION 2

                             BIOMASS ESTIMATES

                                INTRODUCTION
     Meaningful and reproducible estimation of phytoplankton biomass remains
a remarkably complex problem.  In the past few years, several investigators
have returned to estimates of biovolume in an attempt to escape limitations
of traditional secondary measurement techniques.  Biovolume estimates based
on species composition, number, and estimated volume have three inherent
problems:  (1) There is a lack of accuracy in measuring and computing volumes
of microscopic, irregularly-shaped, complex forms;  (2) There are differing
amounts of metabolizing cytoplasm, vacular "dead" volume, and resistant wall
materials found in different divisions of organisms commonly found in
phytoplankton assemblages as well as in different species in any particular
division; and  (3) The physiological state of the cell (as a direct result of
environmental conditions such as light, temperature, and nutrients, as well
as the cell cycle of each organism) may affect both cell size and relative
volumes of cytoplasmic constituents within the cell.

     Electron microscopic morphometric methods are based on mathematical
developments that consider the probability of obtaining certain
two-dimensional profiles from three-dimensional structures by randomly
cutting those structures.  These methods are commonly used to detect
quantitative differences in  tissues and cells as an alternative to
qualitative differences that might be noted during routine observation.
During a study of phytoplankton populations from Saginaw Bay, it became
evident that morphometric methods could be successfully applied to some
members of the assemblage in order to arrive at volume estimates of
components of ecological significance such as carbon-containing cytoplasm,
chloroplast, and "inert" structures.  We have utilized these methods to
estimate the volume density  of cellular components such as cell wall,
chloroplast, vacuole (areas  devoid of any discernible cytoplasmic components,
including gullet, reservoirs, or furrows), storage products, and the
remaining cytoplasmic  components.  The results of the study  indicate that the
problems associated with biovolume estimates can be both understood and, in
many cases, minimized.
                            MATERIALS AND METHODS

     All organisms  examined  in  the morphometric  analyses were obtained from
nearshore  Saginaw Bay  field  samples.  Samples of Anabaena flos-aquae were
collected  from a surface bloom  on 9  June  1975 at Station 18 (Lat. 43°44.5'N,

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Long. 83°46.4'W) approximately 8 mi from the western shore.  All other
samples were obtained from collections at Station 56 (Lat. 43°43.8'N, Long.
83°37.7'W) on 10 April 1975, approximately 4.5 mi offshore, and at Station 12
(Lat. 43°38.4'N, Long. 83°39.7'W) on 3 May 1975, approximately 2 mi
offshore.  Water chemistry values and phytoplankton species composition were
similar for the two stations during the sampling periods in question.  These
samples were particularly well-suited for morphometric analysis since the
major algal divisions were well represented in the samples and many of the
taxa had high standing crops.  Water was pumped from a depth of 1 m into
1-liter polyethylene bottles and was fixed immediately by adding sufficient
glutaraldehyde (50%, biological grade) and sodium cacodylate to give a final
concentration of 3% glutaraldehyde and O.lM cacodylate at pH 7.2.

     Samples were stored on ice and returned to the laboratory within 24 hr
for  further processing.  Samples were then concentrated by gentle
centrifugation and rinsed four times in O.lM cacodylate buffer, pH 7.2.  The
concentrated cells were post-fixed with 1% Os04 in O.lM cacodylate buffer  for
1 hr at 4°C.  Cells were then dehydrated in a graded ethanol-propylene oxide
series and embedded in Epon (Luft, 1961).  Thin sections for electron
microscopy were cut with a diamond knife, collected on 300-mesh copper grids,
and  stained with uranyl acetate (Stempak and Ward, 1964) and lead citrate
(Reynolds, 1963).  Organisms were examined at a standard magnification of
either 4,500X or 8,400X, depending on taxon cell size, using a Zeiss EM 9S-2
electron microscope.  Magnification calibrations of the microscope were made
by use of a replica grating to determine the stability of the standard
magnifications.  The variation was usually less than 2%.  Specimens  for total
cell volume determination were fixed and dehydrated as outlined above,
mounted  in Epon on glass slides, and viewed using a Leitz Ortholux microscope
equipped with a 95X oil-immersion objective, NA 1.30 or greater.
QUANTITATIVE STEREOLOGICAL METHODS

     Eight  taxa,  including representatives  from  the  classes  Cyanophyceae,
Bacillariophyceae, Euglenophyceae, Cryptophyceae, Dinophyceae,  and
Prymnesiophyceae  (Hibberd, 1976), were selected  for  quantitative  analysis.
The  sampling scheme employed was as outlined  in  Table  1.   Seventy-five
micrographs were  examined for each taxon, except where  scarcity of  a
particular  taxon  in the water samples necessitated a somewhat  reduced sample
size.   In all  cases, examination of coefficients of  variation  and plots  of
cumulative means  and variances  indicated  adequate sampling of  the material.
A transparent  0.5-cm square sampling  lattice  was superimposed  over  the
micrographs  for quantitative measurements.

     The  first identifiable occurrence of each taxon on a  grid was
photographed.   Identification or selection  of organisms was  not based on the
presence  or  absence of  particular cellular  organelles.   However,  small
grazing sections  may be slightly undervalued  in  the  samples  due to  problems
associated  with species identification.   Blocks  were retrimmed after  each
series  of sections was  cut, in  order  to  avoid repeated  sampling of  adjacent
material  within the same  organism.  For  filamentous  taxa (eg.  j?.  capucina, S_.
binderanus, A^ f los-aquae), a single  cell was randomly  selected from  each

                                     65

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TABLE 1.   SAMPLING SCHEME EMPLOYED FOR MORPHOMETRIC ANALYSIS

A.
f los-aquae
Number of
Photos Examined 50
Final
Magnification 25,100
Scope
Magnification 8400X
Photographic
Enlargement 3. OX
Average No.
Pts/Photo 450
Total Pts
Counted 23,194
S. F. E. C. P.
binderanus capucina viridis erosa lindemanni Hap 1 Hap 2
46 75 50 75 75 75 75
13,600 25,100 13,600 25,100 13,600 25,100 25,100
4500X 84000 4500X 8400X 4500X 8400X 8400X
3. OX 3. OX 3. OX 3. OX 3. OX 3. OX 3. OX
650 450 750 700 1500 450 250
30,745 33,263 38,448 54,076 111,881 32,715 20,249

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filament.  The largest cross-sectional area of several of the taxa examined
exceeded the photographic field of view at the standard magnification
chosen.  In these cases subsamples of the largest encountered cross-sections
were photographed, using the upper left portion of the first such cell, the
upper right portion of the next, the  lower left, then  the lower  right, etc.

     Estimates of volume density, i.e. the fractional  volume of  a cellular
component related to  its containing volume, were obtained using  both  the
paper profile cut-and-weigh (Delesse, 1847) and grid point-counting
(Glagoleff, 1933; Chalkley, 1943) techniques.  Although both methods  were
found to yield similar estimates of volume density, point-counting was found
to be easier and  faster  to implement.  Except where specifically indicated,
reported morphometric results will be those derived from the point-counting
technique.

     The point-counting  method  is an  extension of the  Delesse principle which
states  that the areal density of profiles on  "two-dimensional" sections is an
unbiased estimate of  the volume density of the corresponding structures
within  the  tissue (Delesse, 1847 cited in Weibel and Bolender, 1973), i.e.

                      V£       Ai      Pi
                      _   =   _   =  _                                  (!)
                      VT       AT      PT

where Vj =  volume of  a component  i, Aj =  area of i  in  section, P^ =  number of
points  falling within the boundary of i,  V-j- = total containing volume, etc.
(Notation and definitions are those of Weibel and Bolender,  1973).   Thus, by
counting points of a  sampling grid striking component  i, or  by weighing the
area of _i on  a two-dimensional  section and comparing  that quantity with a
containing  area measured in the same  units, an unbiased estimate of  the
volume  fraction of component _i  in the original tissue  can be obtained.
Additional  information concerning the more theoretical aspects of stereology
can be  found  in one of the several excellent  reviews  on  the  subject  (Loud,
1968;  Underwood,  1970; Weibel and Bolender, 1973).

     Actual cell  volume  estimates (jjm^) were  obtained  from  light microscopic
examination of cells  obtained  from the same assemblages  as  those used for  the
quantitative  stereological analysis.  Estimates  are based on 10  independent
measurements  for  each taxon, and  assume a regular geometric  shape for the
taxon  (Table  2).  Specific geometric  formulae used  in  the volume calculations
are also presented there.

     Statistical  analyses were  performed  with the assistance of  the  MIDAS
statistical routines  available  through the computing  facilities  at  the
University  of Michigan.   Parameter estimates  are reported as the mean _+  1
 standard error unless specifically designated otherwise.
                                     67

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TABLE 2.  CELL VOLUME ESTIMATES FOR THE EIGHT PHYTOPLANKTON SPECIES EXAMINED
             b - breadth, 1 =  length, h = height, d = diameter

TAXON
Anabaena flos-aquae
Stephanodiscus binderanus
Fragilaria capucina
Euglena viridis
Cryptomonas erosa
Peridinium lindemanni
Haptophyte 1
Haptophyte 2
Volume ynH
80
830
400
3100
1300
11000
100
70
(SE) Formula
(9) l/^d2h
(92) l/b-nd2h
(37) blh
(450) l/6irZ £> + l/4TrZ7Z?9
(250) l/6vlb2
(2100) l/87rZZ?2t
(20) l/4ird h
(7) l/4ir<5 h

*Euglena was assumed to be a composite geometric shape consisting of a
 rotation ellipsoid with major axis of rotation I, and minor axis b,
 and a smaller cylinder of height 1~ and average diameter of b~.

 Peridinium was assumed to be intermediate in volume between a  rotation
 ellipsoid with major axis of rotation 1 and a composite shape  consisting
 of two cones each of height 1/2.
                                     68

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                           RESULTS AND DISCUSSION

DESCRIPTIVE ELECTRON MICROSCOPY

     The following is a brief description of each of the organisms involved
in this study, with detailed information presented on the ultrastructure of
the organism and how this information can be correlated with physiological
evidence.


Anabaena flos-aquae (Cyanophyceae)

     The blue-green alga, Anabaena flos-aquae, was selected to be a
representative nitrogen-fixing organism.  The organism was collected as a
surface bloom with the cells forming tangled masses (Fig. l).  The cells are
cylindrical co spherical; the heterocysts are usually terminal (Fig. 2).

     Blue-green algae are quite distinct, cytologically, from other algal
groups.  This is due to the fact that they are prokaryotic, and hence, more
closely aligned with bacteria both in structure and physiology.  At the light
microscope level, the structural features that can be observed in the
blue-green algae are the centroplasm or nucleoplasm, the central portion of
the cell which is rich in nucleic acids, and the chromatoplasm, the
peripheral portion of the cell that contains the photosynthetic pigments and
several types of granules.  With the aid of the electron microscope (Figs.
3, 4), greater resolution of these features is achieved.  The categories of
cellular compartments in the blue-green algae that were  included in
quantitative  electron microscopy were as follows:

Cell Wall —
     This consists of four  layers, including the peptidoglycan (including
muramic and diaminapimelic  acids).  Dunn et al. (1971) have estimated  that  10
- 20% of the  dry weight of  Anabaena cylindrica is wall material (exclusive  of
mucilage or sheath).  For the present study, mucilage was not included  in
cell wall volume determinations, since very little was present.

"Pseudovacuole"—
     The category pseudovacuole in this study collectively refers to both
areas of intrathylakoidal spaces as well as areas of collapsed gas vacuoles.
The intrathylakoidal spaces may be either fixation artifacts  (since the cells
were fixed in glutaraldehyde, not the method of choice for prokaryotes) or
real spaces,  as these areas can form under certain nutrient conditions
(Jensen and Sicko, 1974; Sicko, 1974).  At best, the estimation of vacuolar
space  in the  blue-green alga is an approximation, since  the vesicles were
collapsed.  Van Baalen and  Brown  (1969) and Smith and Peat (1967) have  shown
that gas vacuoles may take  up as much as 60-70% of the total  cell volume.
Gas vacuoles  have been demonstrated to be formed when the algae are subjected
to  ionic deficiency  (Waaland and Branton, 1969).  In addition to regulating
buoyancy and  consequently environmental conditions, gas  vacuoles may also  be
a means  for concentrating ions within cells by decreasing intracellular
solution volume.
                                      69

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                           KEY TO FIGURE LEGENDS
c  - cyanophycin granule
cl - chloroplast
cy - cytoplasm
cw - cell wall

e  - ejectosome

f  - frustule

g  - golgi body
gb - girdle band
gu - gullet
gv - gas vacuole

h  - heterocyst
ha - haptonema

1  - lipid

m  - mitochonchia
mt - microtubules

n  - nucleus

p  - polyphosphate body
ph - polyhedial body
pa - paramylon
pe - pellicle
Py ~ pyrenoid

s  - storage body
su - sulcus
st - suture
sr - starch

t  - trichocyst
tp - thecal plate

v  - valve
vac- vacuole
                                      70

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Figures 1-4.  Anabaena flos-aquae
        1
        2.
        3.
        4.
X250
X8.600
X18.800
X27.300
              71

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Nitrogen Storage—
     Cyanophycin granules or structured granules are present in both
vegetative cells and akinetes of blue-green algae.  They consist of high
molecular weight copolymers of aspartic acid and arginine (1:1, mol/mol).
This extremely unusual composition reveals them as particularly well suited
to serve as a nitrogen reserve (Simon, 1971a).  Simon (1971b)  isolated these
granules from nitrate-grown vegetative cells of Anabaena cylindrica, where
they account for up to 10% of the dry weight.

Phosphate Storage—
     Polyphosphate bodies are present in limited numbers in blue-green algae
unless the algae are subjected to adverse nutrient conditions.  Any type of
nutrient imbalance can induce their formation, whether  it be the presence of
excess or absence of a particular nutrient.  The polyphosphate bodies encoun-
tered in A., flos-aquae were limited in number and, for  the most part,
appeared extracted.  This again is most likely a result of inappropriate
fixation.

Cytoplasm—
     The remaining components in the blue-green algae were collectively
counted as cytoplasm.  These include the nuclear area,  ribosomes,  "ground
substance," polyhedral bodies, and thylakoids.  No attempt was made to
estimate the thylakoid volume as a separate category comparable to
chloroplast.


Stephanodiscus binderanus and Fragilaria capucina (Bacilliarophyceae)

     Fragilaria capucina  is primarily benthic in habitat preference, but  it
is also a successful  facultative plankton.  In samples  analyzed, j?. capucina
(Figs. 9-11) was one  of the most abundant organisms.  Stephanodiscus
binderanus (Figs. 5-8) is a euplanktonic species; it was not as abundant  as
_F. capucina in the samples examined.

     The diatoms are  most distinct at the ultrastructural  level.   This is due
to the siliceous wall or  frustule.  This same feature (i.e., the siliceous
frustule) also makes  diatoms one of the most difficult  algal groups to study
at the ultrastructural level because  the frustule is very hard, making thin
sectioning difficult.  In general, each cell contains two or more
chloroplasts, a nucleus,  either a central or two  polar  vacuoles,
mitochondria, golgi,  ribosomes, and endoplasmic reticulum.  The  following
celular categories were  included in the diatom morphometric analysis:

Frustule—
     The  frustules of the two diatoms examined differed significantly  in
thickness  (Figs. 7, 8, 11).  The frustule  is easily  identified in  electron
micrographs as electron dense material, platelike in nature,  immediately
outside  the plasma membrane.  Lewin and Guillard  (1963) point  out  that the
variation  in  frustule thickness is both intraspecific and  interspecific,
ranging generally  between 4  and 50%.  Because of  this variation, estimates of
organic constituents  on  a dry weight  basis  from total cell volume  estimates
are  of doubtful value, and not easily compared with  other  algal groups.

                                      72

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Figures 5-8.
        5.
        6.
        7.
        8.
Stephanodiscus binderanus
X980
X10,000
X10,000
X9.050
             7 )

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Figures 9-11.
        9.
       10.
       11.
Fragilaria capucina
X750
X8.250
X18.200

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Vacuole—
     Vacuoles in diatoms are variable.  In S. binderanus (Figs. 7, 8) the
large central vacuole restricts cytoplasmic organelles to the periphery of
the cell.  This situation is not common in diatoms, having only been reported
in Melosira varians (Crawford, 1973).  In J\ capucina, the vacuolar
arrangement is similar to other naviculoid diatoms, in that the cytoplasm is
H-shaped, with parietal chloroplasts and a central cytoplasmic bridge
(Stoermer et al., 1965; Drum, 1963; Dawson, 1973).  Storage products, usually
lipids, are often found within the vacuolar membrane (tonoplast).

Storage Products—
     The storage product most commonly encountered in both diatoms appeared
to be lipid, located mainly in the vacuoles (Figs. 8, 11).  As with many
other algae, storage products accumulate in older cells (Crawford, 1973;
Lewin and Guillard, 1963).  It has been demonstrated that, in young diatom
cultures, lipids constitute 5-15% of the dry weight, whereas in N-deficient
cultures it may increase to 40-50%.

Chloroplast—
     The chloroplasts  in both diatom species examined here are similar
structurally to those  described in other diatoms.  The plastids are bounded
by an envelope composed of two membranes, which  in turn is surrounded by a
membrane of endoplasmic reticulum (ER).  The plastids contain pyrenoids which
are  traversed by a single lamella, composed of three thylakoids.  In the
morphometric analysis, the pyrenoid was counted  in two categories, total
chloroplast and chloroplast storage.  In the final analysis, the  pyrenoid
point totals were added to the total storage, since it is believed to be
involved in the conversion and translocation of  early photosynthate  in
chloroplasts (Griffith, 1970).  This function would more closely  align  it
with storage than with chlorophyll content.

Cytoplasm—
     Other eukaryotic  cell organelles included in  this category and  in  none
of those previously mentioned  include nucleus, golgi, ribosomes,
mitochondria, and "ground substance."
Euglena viridis  (Euglenophyceae)

Cell  Wall-
      In E^igLena  (Fig.  12),  the  cell  covering  is  a  unique  structure termed the
pellicle  (Figs.  13,  14).  The pellicle  is  believed to  consist  of  several  com-
ponents:   1.   plasma membrane,  2.  protein layers  beneath and  parallel to the
plasma membrane,  3.  microtubules, and  4.   an endoplasmic reticulum cis-
terna.  It has been  demonstrated  (Barras  and  Stone,  1965) that the pellicle
is  composed  of approximately 80%  protein.   Silverman and  Hikida (1976) demon-
strated that the  pellicle of _E. gracilis  was  highly resistant  to  disruptive
treatment, and speculate  that the  proteins and microtubules  in the distinct
pellicle  ridges  (Fig.  14) perform a  cytoskeletal role.  For  the purpose of
this  study,  the  area counted in the  "wall" category included the  points


                                      75

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12
  14
                 pe
                Figures  12-14.
                        12.
                        13.
                        14.
Euglena veridis
XI,060
X5.280
X12.100
                             76

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between the ER cisterna and the external surface of the cell.  This area
constitutes the easily identifiable ridge.

Vacuole—
     The structures in Euglena which, perhaps, are most closely aligned with
the vacuole in the other algae examined are the anterior canal, reservoir,
and contractile vacuole (Fig. 14).  The subapical anterior invagination of
the cell from which the flagella emerge is the anterior canal; the flagella
have their bases in the reservoir.  The contractile vacuole  is located
adjacent to the reservo*ir on the side opposite the eyespot.  Since Euglena is
a naked cell, in fresh water it is subject to continuous uptake of water by
osmosis.  To prevent the cell from bursting and to enable it to maintain its
normal size and shape, water must be discharged.  At discharge, the membrane
between the contractile vacuole and reservoir breaks down, with the water
from the contractile vacuole emptying into the reservoir.  This entire area
is surrounded by microtubules, believed to function in closing the canal
(Leedale et al., 1965).  Since this area  is obviously osmo-regulatory  in
function, and contains no discernible organic components within the membranes
(disregarding the  flagella), it was counted in a category comparable to
vacuole in other organisms.

Storage Products—
     The reserve polysaccharide of Euglena is paramylon.  It consists  solely
of g(l ->• 3) linked D-glucose residues and occurs as water insoluble single
membrane-bound inclusions (Craigie, 1974).  Carbon starvation  of Euglena
results in the rapid disappearance of paramylon; restoration of a carbon
source  leads to a  complete reversal to normal morphology  (Malkoff and  Buetow,
1964; Leedale and  Buetow, 1970).  The degradation of paramylon is
photoregulated (Schwartzbach et al., 1975).   In the presence of sufficient
nutrients and no light, carbon is used for cell growth.  When  light is the
major energy source and no external carbon is supplied, paramylon  is
degraded.  This degradation ensures sufficient carbon and energy for plastid
development when the cells are exposed to light.

Chloroplast—
     Euglena generally contains numerous  chloroplasts.  The  chloroplasts
contain thylakoids which are not  arranged as  grana; pyrenoids  are  absent.

Cytoplasm—
     Other organelles  included in  this category were nucleus,  golgi,
mitochondria, endoplasmic reticulum, ribsomes, and eyespot  (adjacent to  the
reservoir).
 Cryptomonas  erosa  (Cryptophyceae)

 Cell  Wall—
      The  cells  of  Cryptomonas  (Figs.  15-17)  are  bounded by a single membrane
 which is  regularly indented.   The  foldings or  indentations on the surface are
 a  result  of  the periplastial  trichocysts  (Gantt,  1971).  The trichocysts
 themselves are  contained  within  single membrane-bound vesicles and are not
                                      77

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Figures 15-17.
        15.
        16.
        17.
Cryptomonas erosa
X2,130
X12,300
X22,900
              78

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generally considered part of the periplast.  Since the wall is essentially a
membrane, no estimation was made of its volume component.

Vacuole—
     The area included in the morphometric analysis as vacuole in Cryptomonas
roughly corresponds to similar structures in Euglena, namely, an anterior
furrow from which the flagella emerge (Figs. 15,16), a gullet (Fig. 17)
comparable to, but not identical with, the reservoir, and a contractile
vacuole or a series of small vacuoles of unknown function.  Since these areas
do not appear to contain any organelles or inclusions, the area point totals
were equated with vacuole in other algae.

Storage Product—
     The main storage product in Cryptomonas is starch.  The starch generally
occupies a position between the chloroplast envelope and the endoplasmic
reticulum which encloses the chloroplast (Fig. 17).  It appears as a
polysaccharide cap around the pyrenoid, but is not actually part of the
chloroplast (Dodge, 1969; 1973).

Chloroplast—
     Cryptomonas contains two parietal chloroplasts.  These chloroplasts
contain many lamellae which consist of two thylakoids.  The pyrenoid is most
often not large, and  is of the stalked variety (Dodge, 1973).

Cytoplasm—
     The remaining cytoplasmic components  in this category include golgi,
mitochondria, ribosomes, "ground substance," and ejectosomes.


Peridinium lindemanni (Dinophyceae)

     Peridinium lindemanni (Figs.  18—20) was found  in large numbers in  the
April station selected for analysis.  It also proved to be fairly abundant,
though not in as large numbers in  the May  sample.  The cellular components
analyzed were the  following:

Cell Wall—
     The dinoflagellates possess a complex cell covering  termed the theca or
amphiesma (Loeblich,  1970).  The theca consists of an outer membrane,
flattened vesicles or thecal plates,  and an inner membrane (Fig. 20).   There
are often subthecal microtubules which are sometimes evenly dispersed and
arranged in pairs  (Dodge, 1971).   The thecal plates are organic in nature;
thick microfibrils appear to be the main component and show random
orientation (Dodge, 1965).  At division, dinoflagellates  share old plates,
then synthesize new plates to complete their theca.  Thus, it  is possible  to
differentiate between newly divided and more mature cells  (Dodge, 1971).

Vacuole—
     Two types of  vacuole or vacuole-like  areas are commonly  found  in
dinoflagellates, food vacuoles, and the pusule.  Food vacuoles, either  empty
or with  recognizable  substances, have been described  in Ceratium (Dodge and
Crawford, 1970) and Oxyrrhis (Dodge and Crawford, 1974).   The  pusule is a


                                      79

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Figures 18-20.
        18.
        19.
        20.
                                   st
Peridinium lindemanni
X810
X6.960
X6,540
                80

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unique osmo-regulatory organelle found in all freshwater dinoflagellate
species examined (Dodge, 1972).   It consists of vesicles, collecting
chambers, and canals, and is more highly organized than contractile vacuoles
of other common phytoplankton organisms.  In J\ lindemanni, the cells were
highly vacuolated (Fig. 20), although the exact nature of the vacuoles was
not determined.

Storage Products—
     The main storage products (Fig. 20) of dinoflagellates are fats or oils,
stored in the form of droplets,  and starch grains (Dodge, 1973).  The storage
products are particularly abundant in organisms that have been fixed from a
natural habitat in which the conditions were very favorable for
photosynthesis (Dodge and Crawford, 1970).

Chloroplast—
     The dinoflagellate chloroplast is  typically bounded by a three membrane
envelope which does not normally have any connections with other cellular
constituents.  The lamellae are made of stacks of three  thylakoids, but there
is some variability in  the arrangement of the lamellae.  As with other
Peridinium species (Dodge, 1975), the chloroplasts in P. lindemanni are
discoid (lens-like) in  shape, have a radial orientation, are numerous, and
are scattered throughout the cell (Fig. 20).  The pryenoids encountered in
Peridinium were small and not easily distinguished due to their location  in
the chloroplast lamellae.  Consequently no attempt was made to quantitate
their relative volume.

Cytoplasm—
     Other organelles included in the cytoplasm category were nucleus,
eyespot, trichocysts, mitochondria, golgi, ER, ribosomes, and "ground
substance."
Prymnesiophycean Algae - Two Undetermined Species

     A  large number of small flagellates were encountered  in  the  two  stations
selected for analysis.  Although their  identification  is still undetermined,
we have concluded that they are prymnesiophycean (haptophycean) algae based
on several ultrastructural observations, all of which  are  characteristic  of
this group (Leadbeater, 1971; Manton and Peterfi, 1969; Hibberd,  1976).

     1. Oftentimes, sections were taken through three  flagella-like basal
        body areas.

     2. Haptonemas were encountered  in  cross section  in several pictures
        (a haptonema  is a  flagellar-like appendage, consisting of six or
        seven  (Fig. 22) microtubles, and endoplasmic  reticulum [Manton,
        1964]).

     3. The golgi apparatus is extensive, with dilated cisternae  and  numer-
        ous "hairy" vesicles.
                                      81

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21
           Figure 21.   Haptophyte #1 X25.700
                                     \
           Figure  22.  Haptophyte #2 X31.500




                         82

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     4.  At least one of the species (Fig.  21) has unmineralized scales
        (confirmed by X-ray energy dispersive analysis).  The scales are
        obvious in all sections taken through the organisms.  There is also a
        slight suggestion that the other species might also possess scales,
        although the freqency of such observations was considerably less.
        When scales were found externally, it was also possible to observe
        scales developing in the golgi.

     5.  Hexagonal arrays of microtubules were also found in sections near the
        flagellar apparatus and in close association with the chloroplast at
        the apical end of the cell, opposite the nucleus.

     The two algae were selected for analysis because they represent both
naked and scaled forms of the group.  The following areas were defined for
the morphometric analysis.

Cell Wall—
     The cell wall was defined as the area outside the plasma membrane.  For
species #1 (Fig. 21), this consisted of the unmineralized scales, and dense
osmiophilic bodies.  The nature of these bodies is unknown.  Since species #2
(Fig. 20) was naked, no wall points were counted.

Vacuole—
     Clear areas devoid of cytoplasm were usually encountered in  the cellular
region adjacent to the flagellar apparatus.  The amount of vacuole observed
was highly dependent on section angle, indicating a small, polar  vacuole.

Storage Products—
     Chrysophycean algae store fat and chrysolaminarin, a 6(1 + 3)  linked
glucan.  These products have not been identified with any certainty in the
Prymnesiophyceae (Hibberd, 1976).  Thus for  the purpose of analysis,
lipid-like inclusions were counted as storage products.

Chloroplasts—
     The  two prymnesiophycean algae have  two parietal chloroplasts  per cell.
The pyrenoid is embedded in the chloroplast with no thylakoid lamellae
penetration.  The  lamellae have three thylakoids.

Cytoplasm—
     Other organelles included in this category were  ribsomes, endoplasmic
reticulum, mitochondria, "ground substance," nucleus, flagellar apparatus,
and the extensive  golgi system and vesicles.
Quantitative Electron Microscopy

Sample Size Determination—
     Plots of  the cumulative mean and variance as a  function  of  the  number  of
micrographs examined were used to evaluate the adequacy of  the micrograph
sample size used  in the morphometric analysis (Chalkley,  1943).   The order  of
micrographs was randomized prior to mean calculation  and  plotting.
Micrographs were  then re-randomized and plotted  a second  time to check  that

                                     83

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the plateau observed for the mean or variance was in fact stable and not a
function of the order of micrographs.  The cumulative means for the largest
organism studied, P. lindemanni, and the smallest, Haptophyte sp#l, are
presented in Fig. 23.  Such plots demonstrate that the apparent requisite
sample size will differ from organism to organism and from component to
component within a given organism.  Components that tend to be highly
oriented, such as the Haptophyte chloroplast or vacuole, require a large
number of random sections to characterize their volume fraction; components
that tend to be more uniformly dispersed throughout the cell, e.g., the
dinoflagellate chloroplast, seem to stabilize rather quickly.  Most cellular
components for the organisms examined in this study were adequately
characterized by 30-50 random micrographs.
Filament Analysis

     A preliminary pilot survey utilizing stereological cut-and-weigh
techniques was undertaken to evaluate the bias introduced by sampling more
than one cell from a given filament.  Two factors suggest a possible bias in
selecting cells from the same filament:  (l)  cells in a given filament are
genetically and developmentally related; and (2)  since cells in the same
filament have been sectioned at the same angle, the primary stereological
assumption of randomness of sectioning angle has been violated.  However,
since ease of sampling favors multiple samples from a single filament, the
question was examined statistically.

     Fifty-two electron micrographs — representing 13 filaments of the
diatom _£. capucina, with four adjacent cells sampled per filament — were
measured using the stereological cut-and-weigh technique.  The volume
fractions obtained for frustule, storage, and cytoplasm for each of the
thirteen filaments were compared using a one-way univariate analysis of
variance (four replicates per ANOVA cell).  The results are summarized in
Table 3.  All three analyses indicate that  the between-filament variance is
significantly larger than within-filament variance.  Examination of mean
cellular volume fractions for the 52 micrographs compared with means obtained
from a sample of  13 micrographs, one randomly chosen from each filament,
shows little difference between the two parameter estimates.  Therefore,
preliminary evidence seems to indicate that multiple samples from a single
filament do not substantially improve volume estimates for the given filament
and may potentially bias the population estimate if differing numbers of
cells are sampled per filament.


General Descriptive Measures

      The quantitative results presented in this study describe both physical
and physiological "compartments" of the cell.  In general, the following
categories and their limits have been utilized:

      *1.  WALL/FRUSTULE = area outside of  the plasma membrane.
                                     84

-------
0.21
QJ5
009
021
0.15
009
039
033
•
027
009
003
039
033

0.27
Hap. spec. 1
wal 1
j yvj^-X^^—^--^
r

vacuolc
I/

chloroplcst
|
1
LV,
-V-/-WX.
storage

/ 	
I cytoplasm
pV

i
i
0 20 40 60 8
Figure 23. Cumulat
function of sample
five cytoplasmic co
018
Q,2
006
0.18
0.12
006
0.27
021
0.15
Q3O
0.24
0.18
039
0.33

027
0
ive mean (perce
size (number of
mponents of P.
2- lindemonni
wal 1
/— "W-~

vacuole
Vs.

chloroplasr
fv--^^-^-^__
1
. storage
1
cytoplasm
J ^*sJ



0 20 40 ' 60 8lC
nt volume) as a
micrographs) for
lindemanni
and Hap. 1
                        85

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        TABLE 3.   ANALYSIS  OF VARIANCE (ANOVA)  OF BETWEEN AND WITHIN
                             FILAMENT VARIANCE

SOURCE
Anova — Frustule fraction
Between filaments
Within filaments
Anova — Storage fraction
Between filaments
Within filaments
Anova — Cytoplasmic fraction
Between filaments
Within filaments
DF

12
39

12
39

12
39
SUM OF SQUARES

.11900
.036417

1.0297
.037337

1.3666
.15117
MEAN SQUARE

.0099167
.0093377

.085811
.00095737

.11388
.0038762
F-STAT

10.620*

89.631*

29.381*

*Significant at .001 level
      *2.  VACUOLE = vacuole  area  of  the  cell  bounded  by  the  vacuolar
           membrane (tonoplast).   This  category may  also  include  storage
           located in  this  region.

      2a.  VACUOLE STORAGE  =  that  portion of  the  total vacuole  volume  which
           is  storage  (generally lipids in the diatoms).

      2b.  "EMPTY" VACUOLE  =  total vacuole -  vacuole storage.

      *3.  CHLOROPLAST =  chloroplast  volume;  also includes  any  pyrenoid  and
           chloroplast storage  products such  as  lipids and  starch,  if  they
           are present.

      3a.  CHLOROPLAST STORAGE  = storage within  the  chloroplast;  pyrenoid
           plus starch.

      3b.  TOTAL CHLOROPLAST  -  CHLOROPLAST STORAGE.

      *4.  CYTOPLASMIC STORAGE  = storage material (starch,  lipids,  oils,
           paramylon,  etc.) located in  the cytoplasm.   Does not include
           vacuole or  chloroplast  storage.
                                      86

-------
      *5.   CYTOPLASM = all cellular components not included in one of the
           above categories (includes organelles such as golgi, nucleus,
           ejectosomes, mitochondria, etc.).

*The sum of the starred components should be 100%.

      6.  TOTAL STORAGE = sum of 2a, 3a, and 4.

      7.  TOTAL CARBON-CONTAINING CYTOPLASM = storage + cytoplasm +
          chloroplast (3b +5+6); does not include vacuole or wall.

      8.  "METABOLIZING" BIOVOLUME = cellular components that are active
          metabolically; cytoplasm plus chloroplast (does not include
          vacuole, wall, or storage).

      Summaries of the quantitative results are presented in Tables 4 and 5.
The following points were noted for the individual species:


Anabaena flos-aquae

      Inappropriate  field fixation and  the  resultant collapse of  individual
gas vesicles probably has led to an underestimation of  the relative volume of
the "pseudovacuole"  category.  No attempt was made to select for  cyanophycin
granules or polyphosphate bodies in the micrographs; therefore the values
obtained should be an unbiased estimate of  the occurrence of these inclusions
within  the field  population.  The extremely low volume  fractions  may be
indicative of the environmental conditions  at  the time  of sampling.
Stephanodiscus binderanus and Fragilaria capucina

      As might be expected, the volume  fraction of  frustule was higher  in _F.
capucina than  in JS. binderanus.  Both diatoms have  a  large volume  fraction  of
vacuole as well as  lipid in the vacuole.  Another common  feature between the
diatoms is the percentage of carbon-containing cytoplasm, which is  slightly
larger than 50%.


Euglena viridis

      The most noticeable feature encountered in Euglena  was  the high
percentage of  storage products  (paramylon).  The reservoir (vacuole) and the
contractile vacuole accounted  for a higher volume fraction than was expected
(16%).  The pellicular  ridges  also occupied  approximately the  same  volume
fraction as the frustule in Stephanodiscus and the  cell wall  in Anabaena.
                                      87

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TABLE 4.   PERCENT VOLUMES OF CYTOPLASMIC COMPARTMENTS IN EIGHT PHYTOPLANKTON SPECIES
                       VALUES REPORTED ARE THE MEAN + 1 S.E.


1. Cell Wall
2. Total Vacuole
A. Vac. Storage
B. "Empty" Vac.
3. Total Chloroplast
CO
00
A. Chlor. Storage
B. Chi. -Chi. Stor.
4. Cytoplasmic Stor.
5. Cytoplasm
6. Total Storage
(Carbon)
7. Carbon-Containing
Cytoplasm
8. "Metabolizing"
Biovolume
A. flos-aquae
5.5 +_ 0.27
28.5 ± 1.12
-0-
28.5 +_ 1.12
-0-
1.4 i 0.28 (N)
0.5 ^ 0.13 (F)
64.1 +_ 1.16
-0-
65.5 +. 1.21
64.1 + 1.16
S. binderanus
6.
61.
20.
41.
14.
1.
12.
-0-
17.
22.
51.
29.
8 ^
6 _+
3 +_
3 +_
3 +_
6 +_
6 +

2 jt
0 ^
8 +_
9 +
1.25
2.89
2.30
3.25
1.36
0.26
1.27

2.04
2.32
3.15
2.41
F. capucina
20.3 +_
35.9 1
12.9 i
23.0 +_
18.9 +_
0.4 i
18.5 +_
-0-
24.9 +_
13.3 +_
56.8 +,
43.5 +
0.69
1.91
2.01
1.62
1.53
0.11
1.51

1.27
2.00
1.86
1.98
E. viridis
5.9 ' +_ 0.90
15.8 +_ 1.53
-0-
15.8 _+ 1.53
22.3 +_ 1.61
-0-
-0-
33.6 +_ 2.44
22.4 +_ 1.27
33.6 ^ 2.44
78.3 +_ 1.90
44.6 + 1.93
C. erosa
-0-
8.0 +_ 0.94
-0-
8.0 + 0.94
46.5 *_ 1.82
24.3 +_ 1.56
22.2 _+ 1.19
-0-
45.5 +_ 1.55
24.3 ^ 1.56
92.0 *_ 0.94
67.7 + 1.59
P. lindemanni
11.5 +^1.23
10.2 + 0.84
-0-
10.2 +_ 0.84
18.9 +_ 0.85
-0-
18.9 +_ 0.85
19.7 +_ 1.53
39.7 + 1.57
19.7 +_ 1.53
78.3 + 1.56
58.6 + 1.62
Hap. 1
13.
21.
-0-
21.
26.
3.
23.
3.
35.
7.
65.
58.
3
2

2
7
6
1
6
2
1
5
3
± °
*_ 1

i 1
+_ 1
± °
+_ 1
± °
+ 1
± °
+_ 1
+ 1
.55
.46

.46
.36
.75
.18
.37
.41
.75
.55
.60
Hap. 2
-0-
2.2
-0-
2.2
36.3
8.3
28.0
7.6
53.8
15.9
97.8
81.9

+ 0.23

+ 0.23
*_ 1.10
_+ 0.73
+ 0.86
_+ 0.65
+_ 1.18
_+ 0.94
i 0.23
+ 0.91

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                        TABLE 5.  ABSOLUTE VOLUMES OF DEFINED AREAS IN THE ALGAE
                 NUMBERS WERE CALCULATED USING THE MORPHOMETRICALLY-DERIVED PERCENTAGES
                    FOUND IN TABLE 4 FOR THESE COMPONENTS, AND THE ABSOLUTE VOLUMES
              OF THE ORGANISMS CALCULATED BY ASSUMING A REGULAR GEOMETRIC FIGURE (TABLE 2)
                   A.           S.          F.         E.          C.            P.
               flos-aquae   binderanus   capucina   viridis     erosa      lindemanni   Hap 1      Hap 2
oo
VO


Total Carbon-
containing
Cytoplasm 52


430 230 2400 1200 8600 66 68
Metabolizing
Biovolume
51
250
170
1400
880
6400
58
57
Naked
Colorplast
            100
             74
           690
             290
            2100
           23
           20

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Cryptomonas erosa

      The three major divisions of cellular compartments accounting for 92%
of the volume of Cryptomonas were cytoplasm, chloroplast, and storage
products.  The remaining 8% of the volume was the anterior furrow and
gullet.  Consequently, Cryptomonas had one of the highest carbon-containing
cytoplasm values.
Peridinium lindemanni

      JP. lindemanni had a total storage volume percent that was near the
middle of the range across all eight species.  This was not obvious from the
pictures; the dinoflagellates had many small starch grains and lipid droplets.


Prymnesiophycean Algal Species 1 and 2

      The differences between these species were as great as the differences
between the diatoms examined.  Total vacuole differed by a factor of 10; the
wall volume percents were 13.3 +_ 0.55 and nil; the total storage differed by
a factor of 2.
                                 DISCUSSION

      The fact that environmental factors affect the cytology and
morphological placticity of cells is easily documented  in the literature.
Studies of morphological and cytological variations are most easily
accomplished by the use of synchronized cultures.  The  information derived
from culture studies, supplemented with studies of naturally-occurring
species, can be used to morphologically characterize algal species occurring
in phytoplankton.

      One of the most extensive reviews relating cytology to cultural con-
ditions was made by Wilkinson and Duguid (1960) with bacteria.  The authors
stress the importance of synchronized cultures for morphological studies
since the cytology is greatly dependent upon the life cycle stage.  In addi-
tion, culture conditions, such as excess or absence of  nutrients, modify  the
cytology, the degree of modification being dependent upon the particular  life
cycle.  Other examples of cytological modification are  abundant.  Clear-cut
modifications relating to environmental conditions are  most easily demon-
strated in both bacteria and blue-green algae.  This is due inherently to the
fact that they are prokaryotes, and have a relatively simple cell organiza-
tion.  No organelles are present and a number of storage inclusion bodies can
be present depending on the immediate environment of the cell (Jensen and
Sicko, 1971; 1973; 1974; Sicko, 1974; Sicko-Goad and Jensen, 1976).

      Cytological and morphological variation, as a manifestation of changing
environmental conditions, is also evident in organisms  that possess more
complex cellular organization (eukaryotes).  However, as the cellular
complexity increases, the number of sites that can be affected  in the cells


                                     90

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also increases.  Along with the increase in complexity, there is generally an
increase in cell size.  Consequently the effects can be more diverse, and are
located in a much larger volume.

      Collyer and Fogg (1955) demonstrated that different species of algae
tend to have similar relative amounts of protein, fats, and carbohydrates
when grown under similar environmental conditions.  Fogg (1966) stated that
differences between algal classes in respect to their percent composition
tend to be small when compared to the differences a single algal species may
show during the course of growth in culture.  This demonstrates that both the
environment and the growth cycle of the cell are important in determining the
biochemical composition of the cell.

      The effects of changes in light intensity on algae have been studied
more extensively than any other parameter.  Sorokin and Krauss (1958, 1965)
found that, in  five green algae, increasing light intensity during growth
initially favors cell division.  After the optimum light intensity is
reached, further increases are inhibitory to cell division.

      Brown and Richardson (1968) studied the effects of different growth
light intensities on various physiological processes in a variety of algae.
They found that the volume of both cells and chloroplasts decreased with
increasing light intensity.  In most cases, the pigment content varied
directly with chloroplast size.  Unlike most studies of light effects, this
study also demonstrates a number of other morphological changes as a result
of varying growth illumination.  The most notable of these effects were:

      1.  Cell  vacuolization increased with increasing  light intensity in
           Amphidinium and Cryptomonas ovata var. palustris.

      2.  A cell volume maximum was dependent on growth light intensity  in
          Chlorella.

      3.  Some  species such as Euglena gracilis exhibited a steady
          growth increase with  increasing illumination, whereas in Nitzschia
          closteriutn, growth was light-dependent only at low intensities.

      Morphological changes also occur as a result of cell cycle and
nutrients.  Messer  and Ben-Shaul (1972) demonstrated that,  in Peridiniutn,
cell size and  chlorophyll content increased during early growth and  decreased
with culture age.   Aged chloroplasts were narrower, had fewer thylakoids, and
also had a greater  association with endoplasmic reticulum and cytoplasmic
ribosomes.  They also found that the  large number of chloroplasts per cell
correlated with a high chlorophyll content.  Holmes  (1966) demonstrated  that,
in  four marine  diatoms, nitrate, silicate, and  phosphate deficiency  resulted
in  both a reduction in chlorophyll _a and a concomitant  decrease in the number
of  chromatophores.  The nutrient deficiencies caused a  cessation of
chlorophyll synthesis whereas  the reduction in  chromatophore number  was  a
result  of division  failure rather than degeneration.

      Atkinson  et al. (1974) first utilized electron microscopic morphometric
methods to determine  the volume  fraction of certain  cellular compartments  in

                                     91

-------
Chlorella.  They demonstrated that cellular organelles were able to grow
continuously throughout the cell cycle.  Consequently, the average volume
percents were 40% for chloroplast, 3% for the mitochondrion, and 10% for
vacuoles and nucleus throughout the cycle.  The components that were of
particular interest were the vacuole, starch, and pyrenoid.  Because
Chlorella contains no large central vacuole, it had previously been assumed
that the area of the tonoplast was insignificant.  The authors confirmed that
the tonoplast has an area equal to at least a third of the plasmalemma area.
This indicates that the small vacuoles randomly scattered  throughout the
cytoplasm do contribute significantly to both the total cell volume as well
as to the tonoplast area, which is also believed to contribute to solute
absorption in plant cells (Laties, 1969; Humphreys, 1973).

      Atkinson et al. (1974) also correlated starch reserves to respiratory
activity of the cell.  Starch appeared to function as a reserve material that
sustained cytokinesis in the absence of photosynthesis.  The onset of
photosynthesis resulted in a recovery of starch reserves that were depleted
during cytokinesis in the dark phase of cell synchronization.  Consequently,
starch reserves were quite dependent on both the photosynthetic and
respiratory activities of the cell.

      Both the qualitative and quantitative results presented  in these few
examples  indicate that morphological characterization of all algal species  is
highly dependent upon a wide variety of parameters.  Although  these
parameters can be easily regulated in a culture situation, the effects
produced  in culture studies are not easily  applied to natural  assemblages
where a wide variety of parameters may be changing simultaneously.  Biovolume
estimates are used to assess the  importance of algal  species since
phytoplankton standing crop  is often converted into biomass through cell
volume determinations (Nalewajko,  1966).  Cell volume data are also used to
extrapolate to organic carbon content, ash-free dry weight, and chlorophyll
(Paasche, 1960; Mullin et al., 1966; Strathmann, 1967).

      We  feel that our results  indicate that the inherent  cellular
organization of some species contributes  significantly to  the  error of such
biomass calculations.  This  problem was first recognized by Lohmann (1908)
who  indicated that only a small proportion  of a large diatom is occupied by
chloroplasts and cytoplasm,  with  the remainder of  the cell being vacuole.
Lohmann (1908) suggested  that  this should be taken into account when
comparing the productive  capacity  of cells  and their  cell  volumes, since the
cytoplasm may form only a layer of 2 m around the  cell periphery.  Paasche
(I960)  and Strathmann  (1967) have  both used  such correction factors and  found
that  cell carbon,  in many instances, correlates better with surface area than
cell  volume  for diatoms.  These techniques  have also  been  utilized recently
by Bellinger (1974).

      The morphometric methods  utilized  in  the present study demonstrate that
both  cell vacuole  and  cell wall play an  important  role as  "inert" structures
in all  the  algal  species  examined, not only the diatoms.   In Table 5, we have
calculated  the corrected  cellular  volumes of carbon-containing structures  in
the  cell, metabolizing  biovolume  (that  portion of  the cell other  than  inert
structures  such  as  cell wall  and  vacuole, and storage products),  and

                                     92

-------
chloroplast volume.  When one does not include cell wall or vacuole in the
volume estimates, the carbon-containing cytoplasm percentage drops
significantly.  Consequently, correction factors are not only applicable to
large diatoms.  Small vacuoles scattered throughout the cytoplasm may
significantly alter biomass and cell carbon estimates.

      One of the most important features of the morphometric study is that
the eight algal species were all taken from water masses with similar
chemical and physical properties.  Consequently, the number of environmental
parameters that have been demonstrated in the literature to affect the
cytology of a variety of organisms is reduced.  Although we are not sure that
all algal species were growing under optimal conditions, it is likely that
the results presented here more closely resemble the percentages that would
be found in a naturally-occurring assemblage during the spring quarter than
would cultured algal species.  In this respect, the corrected biovolume
estimates as presented are better than those derived by use of geometrical
formulae alone.

      The most obvious example of corrected biovolume estimates from our data
.is the case of the two diatoms, S. binderanus and F. capucina.  The
quantitative results show that, in both species of diatom, over 40% of the
cell  is occupied by  frustule and vacuole.  These two taxa also exhibit large
significant differences  in both frustule and vacuole relative volumes, even
though they belong to the same "physiological" group.  Such data suggest that
cell  volumes derived from geometrical formulae may differ significantly from
the real quantity being  sought, such as mg cellular carbon or metabolizing
biomass, and the correction  factor is probably not a constant for  a given
class of algae.  Since,  of all the groups examined in this study,  wall and
vacuole categories attain their largest cellular fractions in diatoms, errors
in cell volume calculations  based on shape will be particularly large in
systems such as  the  Great Lakes where diatoms comprise a significant part of
the assemblage.

      Only a small fraction  of the total storage in both diatom species is
associated with  the  chloroplast.  The remaining storage products,  13-20% of
total cellular volume, were  localized within  the vacuole; approximately half
of the vacuolar  area in  both taxa was occupied by storage.  Since  storage
products are known to accumulate  in  senescent cells, percent  storage may be a
useful indicator of  cell growth conditions.

      We feel  that this  study of  cell volume  components is important for
several reasons:

      1.   The  chemical composition across algal phyla varies.  This  is
           especially significant  in  species that possess non-metabolizable
           mineralized scales or walls, which  make up a considerable
           percentage of  the  total cell volume.

      2.   The  cytological characteristics of  the numerous algal species also
           vary.  Consequently, the percentage of various components, such as
           vacuole, is not consistent either between  phyla or  between similar
           species.

                                     93

-------
Cytological compartments or volumes are subject to change with
changing environmental parameters.   Certain features,  such as the
presence of large amounts of storage products, are indicative of
senescent cells.   The use of morphometric methods allows one to
detect morphological changes that might otherwise go undetected.
One does not have to rely solely on gross morphological changes to
detect significant differences between cells.
                            94

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	, and 	.  1974.  Phosphate metabolism in blue-
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Laties, G. G.  1969.  Dual mechanisms of salt uptake  in relation  to
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Leadbeater, B. S. C.  1971.  Observations on  the life history of  the
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Leedale, G. F.,  and D. E.  Buetow.  1970.  Observations on the mitochondrial
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    •	,  B. J. D. Meeuse, and  E. G. Pringsheim.  1965.  Structure
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 Lewin,  J.  C.,  and R.  Guillard.   1963.   Diatoms.  Ann.  Rev.  Microbiol.
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 Loeblich,  A.  R.   1970.  The  amphiesma  or  dinoflagellate  cell  covering.
       Proc. N. Am.  Paleont.  Conv.   1969.   G:867-929.

 Lohmann, H.   1908.  Untersuchungen  zur Festellung  des  vollstandigen
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 Loud,  A. V.   1968.  A quantitative  stereological description  of the
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       37:27-45.

 Luft,  J. H.   1961.  Improvements in epoxy resin  embedding methods.   J.
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 Malkoff, D. B.,  and D. E.  Buetow.   1964.   Ultrastructural changes during
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 Manton, I. 1964.  Further observations on the fine  structure of the
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           . and  L.  S. Peterfi.   1969.   Observations  on the fine structure
       of coccoliths,  scales  and  the protoplast of a freshwater
       coccolithophorid,  Hymenomonas roseola Stein, with supplementary
       observations on the  protoplast of Cricosphaera carterae.  Proc. Roy.
       Soc.  B.  172:1-15.

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Messer, G., and Y. Ben-Shaul.  1972.  Changes in chloroplast structure
      during culture growth of Peridinium cinctum fo. Westii (Dinophyceae).
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Mullin, M. M., P. R. Sloan, and P. W. Eppley.  1966.  Relationship between
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Nalewajko, C.  1966.  Dry weight, ash, and volume data for some freshwater
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Paasche, E.  1960.  On the relationship between primary production and
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Reynolds, E. S.   1963.  The use of  lead citrate at high pH as an electron
      opaque stain  in electron microscopy.  J. Cell Biol. 17:208-212.

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Sicko, L. M.  1974.  Physiological  and cytological aspects of phosphate
      metabolism  in  the blue-green  alga, Plectonema boryanum.  Ph.D.
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Sicko-Goad, L., and  T. E. Jensen.   1976.  Phosphate metabolism in
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      starvation  and the  "polyphosphate overplus" phenomenon  in Plectonema
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Simon, R. D.   1971a.   Cynaophycin granules  from the blue-green alga
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 Smith,  R. V.,  and  A. Peat.   1967.  Comparative  structure of gas-vacuoles of
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 Sorokin,  C., and R. W. Krauss.   1958.  The  effect  of light intensity on the
       growth rates of green algae.  Plant Physiol. 33:109-113.

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                                      98

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Stempak, J.  F.,  and R.  T.  Ward.   1964.   An improved staining method for
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Strathmann,  R. R.  1967.  Estimating the organic carbon content of phyto-
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van Baalen,  C., and R.  M.  Brown.   1969.   The ultrastructure of the marine
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Waaland, J.  R., and D.  Branton.  1969.   Gas vacuole development in a blue-
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                                     99

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                                 SECTION 3

      LUXURY CONSUMPTION, STORAGE,  AND TRANSPORT OF PHOSPHORUS IN SAGINAW BAY

                                INTRODUCTION
      Polyphosphates are linear condensed phosphates with an elementary
formula of Mn+2Pn03n+j.  They may range in size from a chain length of 2
(Pyrophosphate) to Kurrol's and Maddrell's salts of chain length of around
10^ (Harold, 1966).  Polyphosphates are stable in alkali, bul: acid-labile.

      Lower plants (Keck and Stich, 1957), bacteria (Harold, 1966),
blue-green algae (Sicko, 1974), and a variety of other organisms are known to
accumulate and store large quantities of polyphosphate when j;rown under
conditions of unlimited available phosphorus.  This phenomenon is amplified
when the organisms are grown under conditions of phosphate limitation and
then placed under conditions of available phosphate (Mackerel:h, 1953; Liss
and Langen, 1962; Shapiro, 1967; Sicko-Goad and Jensen, 1976).  This type of
storage has been termed "luxury storage" (Shapiro, 1968) and has also been
referred to as the polyphosphate "overplus" phenomenon (Voels; et al., 1966).

      The physiological roles of phosphagen (Kornberg, 1957; Winder and
Denneny, 1955; Suzuki et al., 1972) and phosphorus reserve (Voelz et al.,
1966; Harold, 1966; Kaltwasser, 1962) have been ascribed to polyphosphate.
The occurrence of polyphosphate has most often been related to several
physiological conditions:

      1.  Nutrient imbalance other than phosphate,

      2.  Restoration of phosphorus supply following phosphorus starvation,
          and

      3.  Nucleic acid  imbalance.

      The ecological significance of polyphosphate in algal cells is not well
understood.  Although  its  presence has most often been related to nutrient
imbalance,  the presence of polyphosphate as a phosphorus storage form in
naturally-occurring species has not been well documented.

      During a study of phytoplankton populations from Sagins.w Bay, algal
cells were  routinely examined by a variety of microscopic techniques for the
presence of polyphosphate  bodies.  The results of the survey are presented  in
this report.
                                     100

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                           MATERIALS AND METHODS

      Most samples were collected and fixed during the routine cruises
according to the schedule outlined in the previous section.  Exception to
this schedule was made in several cases where shoreline samples were obtained
in addition to the routine sampling periods.  In these cases., plankton tows
were also fixed by placing the algae in veronal acetate buffer at pH 6.2 for
3 hours at room temperature (Pankratz and Bowen, 1963).  The algae were then
dehydrated and embedded in the routine manner.
LIGHT MICROSCOPY

      Algal suspensions were stained for polyphosphates by the method of Ebel
et al. (1958) and Jensen (1968).  This staining procedure employs the ability
of lead salts to complex with polyphosphate and remain stable at low pH
values.  The algae were initially fixed in 3% glutaraldehyde in O.lM
cacodylate buffer adjusted to pH 7.2 for a period of 1 hour t
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without phosphate salts, but containing 0.5% soil extract).  The cells were
then resuspended in the low phosphate Chu-14 and incubated in a growth
chamber at 20°C with a 16-hour light, 8-hour dark cycle for 68 hours.  At the
end of this limited phosphate period, during the 4th hour of the light cycle,
the cells were packed by gentle centrifugation and suspended in medium
containing 7.49 mgP/1.  At the end of a 3-hour incubation under the original
light and temperature conditions, the cells were harvested by centrifugation
and fixed for electron microscopy as previously described.  The supernatant
culture medium was also analyzed for total phosphorus content.
                                   RESULTS

      A survey of both light and electron microscope preparations revealed
that polyphosphate bodies were located  in a variety of organisms in  all
segments of Saginaw Bay except segment  IV.  The dates and  locations  of  the
organisms containing polyphosphate bodies are  found in Table  1.  No  samples
were obtained during the  first quarter.

      In general, the light microscopic  techniques involving  lead sulfide
precipitation were difficult to utilize  for these samples  on  a  routine
basis.  Polyphosphate bodies, when they  were present, were very small and
difficult to resolve with the light microscope.  This was  especially apparent
in  the granular blue-green algae.  Examination with the  electron microscope
of  the samples suspected  to contain these inclusions proved that the
assumption about  their small size was correct.

      The electron micrographs (Figs. 1-4) demonstrate that the polyphosphate
bodies encountered were morphologically  similar to the inclusions described
by  other authors.  Most notably, the  inclusions are electron  dense  and
exhibit sublimation pockets when exposed to the electron beam for a  short
period of time.   The polyphosphate bodies were found in  a  variety of
organisms, but most often in bacteria,  green and blue-green iilgae,  and  in
diatoms.  The  inclusions  were of special interest in the diatoms because  they
were most commonly  found  in the large central  vacuoles and w€?re sometimes
found  in association with polysome-like  inclusions.

       Since  the morphological characteristics  of polyphosphate  bodies are  not
well known  for algal species other than blue-green algae,  experiments were
undertaken  to  induce their  formation  and study their morphological
variability.   Cells of Diatoma tenue  var. elongatum  from an exponential
culture were  transferred  to a phosphate-limiting culture medium for  a period
of  approximately  3  days  to  induce  several cell divisions and  subsequent
phosphate limitation.  The  cells were then transferred to  Chu-14 medium
containing  normal phosphate levels.   After 3 hours of  incubation  in  this
medium,  the  cells contained what appeared to be numerous small  polyphosphate
bodies,  located  in  the central vacuole.   The inclusions  were  often  found
associated  with  the polysome-like  inclusions present in  the vacuole. X-ray
energy dispersive analysis  of the  vacuolar region demonstrated  that  this
region contained  quantities of both phosphorus and silicon in addition  to
lower  levels  of  other background elements.  During the 3-hour incubation
period,  the  phosphorus content of  the medium dropped to  6.61  mgP/1.   Since

                                     102

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TABLE 1.  DISTRIBUTION OF POLYPHOSPHATE BODIES IN
 NATURALLY-OCCURRING PHYTOPLANKTON IN SAGINAW BAY

Date Collected
5/3/75
5/3/75
6/9/75

6/27/75
6/27/75
5/14/76
6/17/76
7/16/75
7/16/75
7/31/75
7/31/75
8/19/75
7/8/76
7/7/76
8/5/76
9/1/76
8/30/76
10/5/76
10/5/76
10/8/76
10/7/76
10/7/76
10/8/76
Station
12
52
18

56
12
26
26
12
18
26
52
52
Caseville
7
Port Austin
26
35
7
22
26
51
52
56
Depth
1 m
1 m
surface bloom
(Anabaena)
1 m
1 m
1 m
1 m
1 m
1 m
1 m
1 m
1 M
surface tow
1 m
surface tow
1 m
1 m
1 m
1 m
1 m
1 m
1 m
1 m
Segment
I
V
II

III
I
III
III
I
II
III
V
V
V
I
V
III
II
I
II
III
V
V
III
                        103

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Figures 1-4.  Electron micrographs of polyphosphate bodies  in  species
of phytoplankton from Saginaw Bay.  Magnifications are indicated by bar
in upper left of each figure.  Figure 1. An undetermined small
blue-green alga with large polyphosphate (PP) bodies in boi:h electron
lucent and electron dense regions of the cell.  Figure 2. Anacystis sp.
with polyphosphate bodies (PP).  Figure 3.  Fragilaria capucina with
small polyphosphate bodies (pp) in the vacuole (V), which :Ls surrounded
by the chloroplasts (c) and other cellular organelles.  Figure 4.
Scenedesmus sp. with large polyphosphate bodies in the vacuole.
                                  104

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the morphological characteristics were similar to the polyphosphate bodies
found in the diatoms collected from natural assemblages, the
naturally-occurring polyphosphate bodies were analyzed in a similar fashion.
The results of these analyses are presented in Figures 5-7.
                                 DISCUSSION

      Although the sampling was limited, we found that polyphosphate bodies
were present in a variety of organisms  in Saginaw Bay in all segments except
segment IV.  The use of lead sulfide precipitation to detect their presence
can be somewhat misleading because the  polyphosphate bodies found  in these
organisms were quite small and difficult to resolve with the light
microscope.  The use of the electron microscope and related techniques were
necessary to confirm their presence.

      Additional shoreline samples were obtained during July and August,
1976.  This was necessitated by the fact that the routine method of  fixation
employing glutaraldehyde in the field changed the morphology of the
polyphosphate bodies, especially in the prokaryotes.  Since this was expected
(Jensen et al., 1977), and since a number of extracted polyphosphate bodies
were encountered, especially in Anabaena, shoreline tows were made and the
cells were also fixed in modified osmium, using no glutaraldehyde.   This
method of fixation proved to be superior for the prokaryotes.

      When inclusions were encountered  that were suspected  to be
polyphosphate bodies, x-ray energy dispersive analysis was  usud to confirm
the presence of phosphorus.  This technique was useful when either there  was
a large number of bodies located in one central area or the polyphosphate
bodies were large.  A few small bodies  generally did not provide enough x-ray
emission above background to prove conclusively that phosphorus was  present.
Consequently, Table 1 includes only those stations where the presence of
polyphosphate was confirmed and not merely suspected.

      The most interesting results of the study were obtained both with
Fragilaria capucina, collected from a natural assemblage, and Diatoma tenue
var. elongatum, a cultured species.  _F. capucina had numerous small
polyphosphate bodies located in its vacuole, and often in association with
polysome-like inclusions.  The x-ray spectrum of the vacuolar region
demonstrated that phosphorus, osmium, and silicon were present:  in  this
region.  Although the osmium can be accounted for, as a resull:  of  the
 fixative,  the silicon remains somewhat  puzzling.  Since the morphology of the
 polyphosphate bodies was not what was expected  and  since  it h.js not  been
 adequately described  in diatoms, attempts were made  to  induce  polyphosphate
 body  formation  in a  cultured diatom  through  phosphate  imbalance.   The  results
 of  the  experiment demonstrated the polyphosphate bodies encountered  were
 quite  similar  to  those  found  in  the  naturally-occurring  species.   The  size
 range,  location,  and x-ray  spectrum were  all  similar.   In  addition,  the
 association with  polysome-like  inclusions was  even more  frequent.   This   is
 not surprising  in view  of  the  literature.
                                      105

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                                       1H'
Figures 5-7.  Polyphosphate bodies in Diatoma tenue var. e^.ongatum.
Magnifications of electron micrographs indicated by scale bar in upper
left of figures.  Figure 5. Marginal region of the cell showing
chloroplast (C), mitochondria (M), and the vacuole (V).  Electron dense
structures in the right of the figure are elements of the siliceous
wall.  Figure 6. Vacuolar (V) region of cell.  Polyphosphate (PP)
bodies appear to be formed in linear arrays of polysome-like (PI)
bodies.  Figure 7. X-ray spectrum of polyphosphate bodies shown in
Figure 6.   Phosphorus peak (P) is indicated.
                                  106

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      Jensen (1969) demonstrated that, in Plectonema boryanum, polyphosphate
bodies frequently developed in the ribosoraal areas of the cytoplasm.  Sicko
(1974) found that, under conditions of phosphate imbalance, polyphosphate
bodies developed in association with strands of DNA in the nuclear area of ]?.
boryanum.  It was postulated that the DNA strands, along with short chained
polyphosphates, could serve as primers for the polymerization of the longer
chained acid-insoluble polyphosphates.

      The relationship between nucleic acids and polyphosphate is further
complicated by studies which indicate that ribonucleic acid and polyphosphate
may exist as a complex in several organisms.  This complex was first
postulated by MacFarlane (1936).  RNA-polyphosphate has been demonstrated by
Kulaev and Belozerskii (1958) in Aspergillus niger, by Chayen et al. (1955)
in Torulopsis utilis, by Winder and Denneny (1957) in Mycobacteria, by Ebel
et al. (1958, 1962) in yeast, by Correll and Tolbert (1962, ii964) and by
Correll (1965) in Anabaena and Chlorella.  Correll and Tolbert (1962, 1964)
found that, in Anabaena, the complex accounted for 25-35% of the total
phosphorus, and a major portion of the alga's RNA.  However, there was an
additional 40-50% of the total phosphorus present as uncomploxed
polyphosphate.  The polyphosphate-RNA complex in Chlorella was more variable;
the relative amounts of the complex varied with respect to the synchronized
growth cycle.

      The ecological causes and consequences of polyphosphati; storage in
phytoplankton may be important in evaluating the impact areas, such as
Saginaw Bay, on the rest of the Great Lakes system.  Although this
preliminary study does not provide sufficient basis to fully determine the
importance of the process, a number of points are evident.

      On the basis of the literature and the number of experiments carried
out with phytoplankton species native to the Great Lakes,  it is evident that
the accumulation of phosphorus in the form of polyphosphate bodies may be
triggered by any one of a number of mechanisms which interfere with normal
cellular growth processes.  In a sense, the process provides a mechanism
whereby organisms may protect their ability to sequester  the crucial limiting
nutrient phosphorus even in the presence of other growth  limitations.  The
most  commonly observed condition inducing polyphosphate body formation is
phosphorus limitation followed by resupply of the nutrient af: concentrations
above the immediate growth needs.or capabilities of the cells.  The process
may also be induced by conditions where adequate phosphorus supplies are
present, but growth is limited by concentration of some other nutrient or
factor.  Polyphosphate body formation may also apparently  be initiated by  low
level toxic stress on the cells, sufficient to restrict maxinum growth rates.

      The observed distribution of phytoplankton populations containing
polyphosphate bodies is consistent with any one, or a combination of, these
mechanisms.  On the basis of our limited observations, populations containing
polyphosphate bodies are frequent in  segments 1, 3, and 5, rare in segment 2,
and not  present in segment 4.  These  results imply that exposure to factors
inducing polyphosphate body formation is probably greatest in segment 1, and
affected populations are then entrained  in  the normal circulation pattern  of
the bay.  It  is particularly  interesting that the abundance of polyphosphate

                                     107

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bodies corresponds to the usual pattern of greatest total phytoplankton
density and to the most probable area of excursion of materials from the bay.
Within this area the relative abundance of cells containing polyphosphate
bodies appears to be quite uniform.

      The most probable consequence of polyphosphate body formation is a
temporal separation of phosphorus uptake from eventual resultant growth.  In
some cases cells which have sequestered phosphorus in excess of their
immediate needs may perish before utilizing the reserve.  The population, as
a whole, however could be expected to exhibit a delayed growth response.
This phenomenon may account, in part at least, for the persistent pattern of
high phytoplankton abundance at stations along the southern coast of Saginaw
Bay.  In a system like Saginaw Bay which has dynamic circulation patterns,
the delayed response also implies responses in areas some distance removed
from the primary source of phosphorus enrichment.  This is probably the most
important aspect of the problem in the general case of the Great Lakes.
Potentially obnoxious populations developed in areas of high nutrient  loading
could exit the immediate area of effect carrying with them the potential  for
growth, even under phosphorus-limited conditions.  The largest potential
expression of the effect would be expected to occur in the blue-green  algae,
which are apparently subjected to minimal sinking and predation losses.  We
regard this mechanism as a probable explanation for the extreme dispersal of
certain blue-green algal populations from Saginaw Bay into Lake Huron
observed by Schelske et al. (1974) and Stoermer and Kreis (1980).

      We had previously assumed that polyphosphate body formation was
important only in prokaryotic organisms.  The results of this study suggest
that the mechanism is present in most of the major physiological groups
present in the Great Lakes.  Notable exeptions seem to be the Cryptomonads
and Dinoflagellates.  Although we have not attempted induction in species of
these groups under experimental conditions, none of the wild populations
examined contained polyphosphate bodies.  Representatives of all of the other
major algal physiological groups did.  Most of the species examined in the
study are usually associated with eutrophied conditions in the Great Lakes
and it  is possible that luxury consumption of phosphorus is one of the
factors which confers competitive  advantage on these populations.  Further
research will be needed to answer  this question.

      Our results also  indicate that heavy metals may also be sequestered  in
polyphosphate bodies.  This mechanism  is physiologically plausible and may be
important in biological transport  of toxic materials.  We are investigating
this problem at  the present time.
                                      108

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      Hass. J. Exp. Bot. 4:296-313.

Pankratz, H. S., and C. C.  Bowen.  1963.  Cytology of  the blue-green algae.
      I.  The cells of  Symploca muscorum.  Amer. J. Bot. 50:387-399.

Schelske, C. L., L. E.  Feldt, M. S. Simmons, and E. F.  Stoerner.   1974.
      Storm induced relationships among chemical conditions and phytoplankton
      in Saginaw Bay and western Lake Huron.  Proc. l7tn Conf. Great Lakes
      Res.  pp. 78-91.  Internat. Assoc. Great Lakes Res.

Shapiro, J.  1967.  Induced rapid release and uptake of phosphate  by micro-
      organisms.   Science 155:1269-1271.

	.  1968.  Studies on the natural  factors affecting phosphate ab-
       sorption  and  its  utilization  by  algae.  Water  Res.  2:21-23.

 Sicko, L. M.  1974.   Physiological  and cytological aspects  of  phosphate
       metabolism  in  the blue-green  algal, Plectonema boryanum.   Ph.D.
       Dissertation,  The City University of New York,  New  York.

 Sicko-Goad,  L., and  T.  E.  Jensen.   1976.  Phosphate  metabolism in  blue-green
       algae.  II.   Changes in  phosphate distribution during starvation  and
       the "polyphosphate overplus"  phenomenon  in  Plectonema boryanum.
       Amer.  J.  Bot.  63:183-188.

 Stoermer, E.  F.,  and R. Kreis.   1980.   Phytoplankton composition and
       abundance in  southern Lake Huron.   Univ. Michigan,  Great Lakes  Res.
       Div.,  Spec. Rep.  No. 65.   382 pp.

 Suzuki,  H.,  T.  Kaneko,  and Y.  Ikeda.   1972.  Properties of  polyphosphate
       kinase prepared from Mycobacterium smegmatis.   Biochim.  Biophys.  Acta.
       268:381-390.
                                     110

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Voelz, H., U. Voelz, and R. 0. Ortigoza.  1966.  The "polyphosphate overplus"
      phenomenon in Myxococcus xanthus and its influence on  the  architecture
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Winder, F. G., and J. M. Denneny.  1955.  Utilization of metciphosphate  for
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               and 	.  1957.  The metabolism of  inorganic  poly-
      phosphate in Mycobacteria.  J. Gen. Microbiol.  l-7:573-!>85.
                                      Ill

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      APPENDIX 1.  PHYTOPLANKTON OF SAGINAW BAY (LAKE HURON)., 1974-1976



BACILLARIOPHYTA

Achnanthes affinis Grun.
Achnanthes biasolettiana (Kiitz.) Grun.
Achnanthes bioreti Germain
Achnanthes clevei Grun.
Achnanthes clevei var. rostrata Hust.
Achnanthes exigua Grun.
Achnanthes exigua var. heterovalva Krasske
Achnanthes flexella (Kutz.) Brun
Achnanthes flexella var. alpestris Brun
Achnanthes hungarica (Grun.) Grun.
Achnanthes lanceolata (Breb.) Grun.
Achnanthes lanceolata var. dubia Grun.
Achnanthes lanceolata var. omissa Reim.
Achnanthes lapponica (Hust.) Hust.
Achnanthes lapponica var. ninckei (Guerm. and Mang.) Reim.
Achnanthes linearis (W. Sm.) Grun.
Achnanthes microcephala (Kiitz.) Grun.
Achnanthes minutissima Kiitz.
Achnanthes minutissima var. cryptocephala Grun.
Achnanthes oestrupii var. lanceolata Hust.
Actinocyclus normanii fo. subsalsa (Juhl.- Dannf.) Hust.
Amphipleura pellucida (Kiitz.) Kiitz.
Amphora cruciferoides Stoerm. and Yang
Amphora ovalis (Kiitz.) Kiitz.
Amphora ovalis var. affinis (Kiitz.) V.H.
Amphora ovalis var. pediculus (Kiitz.) V.H.
Amphora perpusilla (Grun.) Grun.
Amphora subcostulata Stoerm. and Yang
Amphora veneta var. capitata Haworth
Anomoeoneis vitrea (Grun.) Ross
Asterionella formosa Hass.
Caloneis  alpestris (Grun.) Cl.
Caloneis  bacillum (Grun.) Cl.
Caloneis  bacillum var. lancettula (Schulz) Hust.
Caloneis  sp. #3
Caloneis  ventricosa var. #1
Cocconeis diminuta Pant.
Cocconeis fluviatilis Wallace
Cocconeis pediculus Ehr.
Cocconeis placentula Ehr.
Cocconeis placentula var. euglypta (Ehr.) Grun.
Cocconeis placentula var. lineata (Ehr.) V.H.
Cocconeis sp.#2
Cocconeis thumensis A. Mayer

(continued).
                                        112

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APPENDIX 1.  (continued).
Cyclotella antiqua W. Sm.
Cyclotella atomus Hust.
Cyclotella comensis Grun.
Cyclotella comta~(₯hr.) Kiitz.
Cyclotella cryptica Reimann, Lewin and Guillard
Cyclotella kuetzingiana Thw.
Cyclotella kuetzingiana auxospore
Cyclotella meneghiniana Kiitz.
Cyclotella meneghiniana var. jplana Fricke
Cyclotella michiganiana Skv.
Cyclotella ocellata Pant.
Cyclotella operculata ( Ag . ) Kiitz.
Cyclotella sp. auxospore
Cyclotella stelligera (Cl.  and Grun.) V.H.
Cyclotella stelligera auxospore
Cyclotella temperei M. Perag. and Herib.
Cymatopleura elliptica (Breb. and Godey) W. Sm.
Cymatopleura solea (Breb. and Godey) W. Sm.
Cymatopleura solea var. apiculata (W. Sm.) Ralfs
Cymbella affinis Kiitz.
Cymbella amphicephala Nag.
Cymbella cesatii (Rabh.) Grun.
Cymbella cistula (Ehr.) Kirchn.
Cymbella cuspidata Kiitz.
Cymbella delicatula Kiitz.
Cymbella hybrida Grun.
Cymbella leptoceros var. rostrata Hust.
Cymbella microcephala Grun.
Cymbella microcephala var.  crassa Reim.
Cymbella minuta Hilse
Cymbella minuta var.  silesiaca (Bleisch) Reim.
Cymbella minuta fo. latens  (Krasske) Reim.
Cymbella muelleri fo. ventricosa (Temp, and Perag.) Reim.
Cymbella obtusiuscula Kiitz.
Cymbella parvula Krasske
Cymbella prostrata (Berk.)  Cl.
Cymbella prostrata var. auerswaldii (Rabh.) Reim.
Cymbella sinuata Greg.
Cymbella sp. #1
Cymbella sp. #6
Cymbella sp. #10
Cymbella subventricosa Choln.
Cymbella triangulum (Ehr.)  Cl.
Cymbella tumida (Breb.) V.H.
Cymbella turgida var. pseudogracilis Choln.
Cymbella ventricosa Ag.

(continued).
                                       113

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APPENDIX 1.  (continued).
Denticula tenuis var. crassula (Nag.) W. and G.S. West
Diatoma tenue Ag.
Diatoma tenue var. elongatum Lyngb.
Diatoma tenue var. pachycephala Grun.
Diatoma vulgare Bory
Diploneis boldtiana Cl.
Diploneis oculata (Breb.) Cl.
Diploneis parma Cl.
Entomoneis ornata (J.W. Bail.) Reim.
Epithemia intermedia Fricke
Epithemia sorex Kiitz.
Epithemia turgida (Ehr.) Kiitz.
Fragilaria brevistriata Grun.
Fragilaria brevistriata var. inflata (Pant.) Bust.
Fragilaria capucina Desm.
Fragilaria capucina var. lanceolata Grun.
Fragilaria capucina var. mesolepta Rabh.
Fragilaria construens (Ehr.) Grun.
Fragilaria construens var. binodis (Ehr.) Grun.
Fragilaria construens var. minuta Temp, and M. Perag.
Fragilaria construens var. pumila Grun.
Fragilaria construens var. venter (Ehr.) Grun.
Fragilaria crotonensis Kitton
Fragilaria crotonensis var.  oregona Sov.
Fragilaria intermedia Grun.
Fragilaria intermedia var. fallax (Grun.) A. Cl.
Fragilaria leptostauron (Ehr.) Hust.
Fragilaria leptostauron var. dubia (Grun.) Hust.
Fragilaria pantocsekii var.  binodis (Pant.) A. Cl.
Fragilaria pinnata Ehr.
Fragilaria pinnata var. intercedens (Grun.) Hust.
Fragilaria pinnata var. lancettula (Schum.) Hust.
Fragilaria vaucheriae (Ktitz.) Peters.
Frustulia vulgaris (Thw.) Del.
Gomphonema acuminatum Ehr.
Gomphonema angustatum  (Kiitz.) Rabh.
Gomphonema angustatum var. producta Grun.
Gomphonema intricatum Kiitz.
Gomphonema intricatum var. pumila Grun.
Gomphonema olivaceum (Lyngb.) Kiitz.
Gomphonema parvulum  (Kiitz.)  Kiitz.
Gomphonema parvulum  var. lagenula (Kiitz.) Freng.
Gomphonema subclavata var. mustela (Ehr.) Cl.
Gomphonema sp.  #3
Gomphonema truncatum Ehr.
Gyrosigma acuminatum (Kiitz.) Rabh.

(continued).
                                       114

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APPENDIX 1.  (continued).
Gyrosigma attenuatum (Kiitz.) Rabh.
Gyrosigma scalproides (Rabh.) Cl.
Gyrosigma spencerii (Sulliv. and Wormley) Cl.
Gyrosigma spencerii var. curvula (Grun.) Reim.
Hantzschia amphioxys (Ehr.) Grun.
Mastogloia smithii Thw.
Melosira distans var. alpigena Grun.
Melosira granulata (Ehr.) Ralfs
Melosira granulata var. angustissima 0. Mull.
Melosira islandica 0. Mull.
Melosira italica subsp. subarctica 0. Mull.
Melosira varians Ag.
Meridion circulare (Grev.) Ag.
Meridion circulare var. constrictum (Ralfs) V.H.
Navicula acceptata Hust.
Navicula anglica var. subsalsa (Grun.) Cl.
Navicula aurora Sov.
Navicula bacillum Ehr.
Navicula capitata Ehr.
Navicula capitata var. hungarica (Grun.) Ross
Navicula capitata var. luneburgensis (Grun.) Patr,
Navicula capitata var. #1
Navicula dementis Grun.
Navicula cocconeiformis Greg.
Navicula confervacea (K'utz.) Grun.
Navicula costula'ta Cl. and Grun.
Navicula cryptocephala K'utz.
Navicula cryptocephala var.  intermedia V.H.
Navicula cryptocephala var.  veneta (K'utz.) Rabh.
Navicula cuspidata (Kvitz.) Kutz.
Navicula decussis 0str.
Navicula exigua var. capitata Patr.
Navicula explanata Hust.
Navicula gastrum (Ehr.) Kiitz.
Navicula gottlandica Grun.
Navicula gregaria Donk.
Navicula heufleri var. leptocephala (Breb.) Patr.
Navicula integra (W. Sm.) Ralfs
Navicula jaernefeltii Hust.
Navicula lacustris Greg.
Navicula lanceolata (Ag.) Kiitz.
Navicula latens Krasske
Navicula menisculus Schuin.
Navicula'menisculus var. obtusa Hust.
Navicula menisculus var. upsaliensis Grun.
Navicula minima Grun.
 (continued).
                                        115

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APPENDIX 1.  (continued).
Navicula minuscula Grun.
Navicula mutica K'utz.
Navicula mutica var. cohnii (Hilse) Grun.
Navicula nyassensis fo. minor 0. Mull.
Navicula odiosa Wallace
Navicula ordinaria Bust.
Navicula peregrina (Ehr.) KUtz.
Navicula placentula (Ehr.) K'utz.
Navicula protracta (Grun.) Cl.
Navicula protracta fo. subcapitata (Wisl. and Por.) Hust.
Navicula pupula Klitz.
Navicula pupula var. rectangularis (Greg.) Grun.
Navicula pygmaea KUt z.
Navicula radiosa KUtz.
Navicula radiosa var. tenella (Breb.) Cl. and Moll.
Navicula reinhardtii Grun.
Navicula rhynchocephala Klitz.
Navicula rotunda Hust.
Navicula scutelliodes W. Sm.
Navicula sp. #7
Navicula sp. #35
Navicula sp. #43
Navicula sp. #44
Navicula sp. #55
Navicula sp. #78
Navicula spp.
Navicula stroemii Hust.
Navicula stroesii (0str.) A. Cl.
Navicula subseminulum Hust.
Navicula terminata Hust.
Navicula tripunctata (O.F. Mull) Bory
Navicula tripunctata var. cuneata  (Lauby) Stoerm. and Yang
Navicula tripunctata var. schizoneiuoides (V.H.) Patr.
Navicula tuscula Ehr.
Navicula tuscula fo. obtusa (Hust.) Hust.
Navicula vanheurck.il Patr.
Navicula viridula (Kiitz.) Ehr.
Navicula viridula var. linearis Hust.
Navicula viridula var. rostellata  (Kiitz.) Cl.
Navicula viridula var. #2
Neidium dubium (Ehr.) Cl.
Neidium dubium fo. constrictum  (Hust.) Hust.
Neidium dubium var. #1
Nitzschia  acicularioides Hust.
Nitzschia  acicularis (KUtz.) W. Sm.
Nitzschia  actinastroides  (Lemm.) Van Goor

(continued).


                                       116

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APPENDIX 1.  (continued).
Nitzschia acula Hantz.
Nitzschia amphibia Grun.
Nitzschia angustata var. acuta Grun.
Nitzschia apiculata (Greg.) Grun.
Nitzschia bacata Hust.
Nitzschia capitellata Hust.
Nitzschia commutata Grun.
Nitzschia confinis Hust.
Nitzschia denticula Grun.
Nitzschia diserta Hust.
Nitzschia dissipata (Kiitz.) Grun.
Nitzschia dissipata var. borneensis Hust.
Nitzschia dissipata var. media (Hantz.) Grun.
Nitzschia filiformis  (W. Sm.) Schutt
Nitzschia fonticola Grun.
Nitzschia fonticola var. pelagica Hust.
Nitzschia frustulum (Kiitz.) Grun.
Nitzschia frustulum var. perminuta Grun.
Nitzschia frustulum var. subsalina Hust.
Nitzschia frustulum var. #1
Nitzschia gracilis Hantz.
Nitzschia holsatica Hust.
Nitzschia hungarica Grun.
Nitzschia insecta Hust.
Nitzschia interrupta  (Reich.) Hust.
Nitzschia kuetzingiana  Hilse
Nitzschia linearis (Ag.) W. Sm.
Nitzschia linearis var.  tenuis (Kiitz.) Grun.
Nitzschia longissima  fo. parva Grun.
Nitzschia longissima  var. reversa Grun.
Nitzschia palea (Kiitz.) W. Sm.
Nitzschia palea var.  tenuirostris Grun.
Nitzschia paleacea Grun.
Nitzschia recta Hantz.
Nitzschia sigma (Kiitz.) W. Sm.
Nitzschia sigmoidea (Nitz.) W. Sm.
Nitzschia sp. #1
Nitzschia sp. #2
Nitzschia sp. #5
Nitzschia sp. #6
Nitzschia sp. #8
Nitzschia sp. #9
Nitzschia sp. #10
Nitzschia sp. #11
Nitzschia sp. #17
Nitzschia sp. #18
 (continued).
                                       117

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APPENDIX 1.  (continued).
Nitzschia sp. #19
Nitzschia sp. #22
Nitzschia sp. #26
Nitzschia spiculoides Hust.
Nitzschia subamphioxoides Hust.
Nitzschia sublinearis Hust.
Nitzschia thermalis (Ehr.) Auersw.
Nitzschia thermalis var. minor Hilse
Nitzschia tryblionella Hantz.
Nitzschia tryblionella var. debilis (Arn.) A. Mayer
Nitzschia tryblionella var. levidensis (W. Sm.) Grun.
Opephora martyi Herib.
Pinnularia brebissonii (Ku'tz.) Rabh.
Pinnularia globiceps Greg.
Pinnularia viridis (Nitz.) Ehr.
Plagiotropis lepidoptera var. proboscidea (Cl.) Reim.
Rhizosolenia eriensis H.L. Sm.
Rhizosolenia gracilis H.L. Sm.
Rhoicosphlenia curvata (Ku'tz.) Grun.
Skeletonema potamos (Weber) Hasle
Skeletonema subsalsum (A. Cl.) Bethge
Stauroneis acutiuscula M. Perag. and Herib.
Stauroneis dilatata Ehr.
Stephanodiscus alpinus Hust.
Stephanodiscus astraea (Ehr.) Grun.
Stephanodiscus binderanus (Kiitz.) Kreig.
Stephanodiscus hantzschii Grun.
Stephanodiscus minutus Grun.
Stephanodiscus niagarae Ehr.
S tephanodiscus sp. auxospore
Stephanodiscus subtilis (Van Goor) A. Cl.
S tephanodiscus tenuis Hust.
Stephanodiscus transilvanicus Pant.
Surirella angusta Ku'tz.
Surirella birostrata Hust.
Surirella biserlata var.  diminuta A. Cl.
Surirella linearis var. constricta (Ehr.) Grun.
Surirella ovata Ku'tz.
Surirella ovata var. pinnata (W. Sm.) Rabh.
Surirella ovata var. salina (W. Sm.) Rabh.
Surirella ovata var. #1
Surirella sp. #4
Synedra acus Ku'tz.
Synedra capitata Ehr.
Synedra cyclopum Brutschy
Synedra delicatissima W.  Sm.

(continued).


                                     118

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APPENDIX 1.  (continued).
Synedra delicatissima var. angustissima Grun.
Synedra filiformis Grun.
Synedra minuscula Grun.
Synedra montana Krasske
Synedra ostenfeldii (Kreig.) A. Cl.
Synedra parasitica (W. Sm.) Hust.
Synedra rumpens Kiitz.
Synedra rumpens var. familiaris (Ku'tz.) Hust.
Synedra tenera W. Sm.
Synedra ulna (Nitz.) Ehr.
Synedra ulna var. chaseana Thomas
Synedra ulna var. claviceps Hust.
Synedra ulna var. danica (Kutz.) V.H.
Synedra ulna var. spathulifera (Grun.) V.H.
Tabellaria fenestrata (Lyngb.) Kutz.
Tabellaria fenestrata var. geniculata A. Cl.
Tabellaria flocculosa (Roth) Kutz.
Tabellaria flocculosa var. linearis Koppen
Thalassiosira pseudonana Hasle and Heim.
Thalassiosira weissflogii (Grun.) Fryxell and Hasle

CHRYSOPHYTA

Chrysochromulina parva Lackey
Chrysochromulina sp. #1
Chrysosphaerella longispina Lautb.
Dinobryon cylindricum Imhof
Dinobryon cylindricum cysts
Dinobryon divergens Imhof
Dinobryon sociale Ehr.
Dinobryon cysts
Hymenomonas roseola Stein
Mallomonas caudata Iwanoff
Mallomonas elongata Reverdin
Mallomonas fastigata Zach.
Mallomonas litomesa Stokes
Mallomonas producta (Zach.) Iwanoff
Mallomonas pseudocoronata Presc.
Mallomonas sp. #1
Mallomonas sp. #3
Mallomonas tonsurata var. alpina  (Pasch. and Ruttn.) Kreig.
Mallomonas cysts
Ochromonas sp. #1
Spiniferomonas trioralis Takahashi
Synura uvella Ehr.
Uroglenopsis americana  (Calk.) Lemm.

(continued).

                                       119

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APPENDIX 1.  (continued).
CRYPTOPHYTA

Cryptomonas erosa Ehr.
Cryptomonas marssonni Skuja
Cryptomonas ovata Ehr.
Cryptomonas sp. //I
Cryptomonas cyst
Chroomonas nordstedtii Hansg.
Rhodomonas minuta Skuja
Rhodomonas minuta var. nannoplanctica Skuja
Undetermined cyst
Undetermined flagellate sp. #1
Undetermined flagellate sp. #2
Undetermined flagellate spp.
CHLOROPHYTA

Actinastrum gracilimum G.M. Sm.
Actinastrum hantzschii Lagerh.
Actinastrum hantzschii var. fluviatile Schroed.
Ankistrodesmus braunii (Nag.) Brunnth.
Ankistrodesmus falcatus (Corda) Ralfs
Ankistrodesmus falcatus var. mirabilis (West and West) G.S. West
Ankistrodesmus gelifactum  (Chod.) Bourr.
Ankistrodesmus setigerus (Schroed.) G.S. West
Ankistrodesmus sp. #1
Ankistrodesmus sp. #3
Ankistrodesmus sp. #4
Binuclearia eriensis Tiffany
Borodinella polytetras Miller
Botryococcus braunii Ku'tz.
Cerasterias sp. #1
Characium  curvatum G.M. Sm.
Chlamydomonas sp. //I
Chlorella  sp. #1
Chodatella ciliata (Lagerh.) Chod.
Cladophora sp. #1
Closteriopsis sp. #1
Closterium aciculare T. West
Coccomyxa  minor Skuja
Coelastrum microporum Nag.
Coelastrum proboscideum Bohlin
Coelastrum reticulatum (Dang.) Senn.

(continued).
                                      120

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APPENDIX 1.  (continued).
Cosmarium botrytis Menegh.
Cosmarium depressum (Nag.) Lundell
Cosmarium sp. #1
Crucigenia quadrata Morren
Dictyochlorella sp. #1
Dictyosphaerium ehrenbergianum Nag.
Dictyosphaerium pulchellum Wood
Dimorphococcus sp. //I
Elaktothrix gelatinosa Wille
Eudorina elegans Ehr.
Eutetramorus sp. //I
Franceia droescheri (Lennn.) G.M. Sm.
Gloeocystis planctonica (West and West) Lemm.
Gloeocystis sp. #1
Gplenkinia paucispina West and G.S.  West
Golenkinia radiata (Chod.) Wille
Gonium pectorale Mull.
Kirchneriella lunaris (Kirch.) Moebius
Kirchneriella obesa var. major (Bernard) G.M. Sm.
Lagerheimia subsalsa Lemm.
Lobocystis sp. #1
Micractinium pusillum Fresenius
Mougeotia sp. #1
Nephrocytium agardhianum Nag.
Nephrocytium limneticum (G.M. Sm.) G.M. Sm.
Oedogonium sp. #1
Oocystis borgei Snow
Oocystis parva West and West
Oocystis solitaria Wittr.
Oocystis spp.
Palmodictyon sp. //I
Pediastrum boryanum (Turp.) Menegh.
Pediastrum duplex Meyen
Pediastrum duplex var. clathratum (A. Braun) Lagerh.
Pediastrum duplex var. cohaerens Bohl.
Pediastrum tetras (Ehr.) Ralfs.
Pedinomomas sp. #1
Phacotus lenticularis (Ehr.) Stein
Planctonema lauterbornii Schmidle
Quadrigula lacustris (Chod.) G.M. Sm.
Saturnella sp. #1
Scenedesmus abundans var. brevicauda G.M. Sm.
Scenedesmus acutiformis Schroed.
Scenedesmus arcuatus var. platydisca G.M. Sm.
Scenedesmus armatus (Chod.) G.M. Sm.
Scenedesmus bicellularis Chod.

(continued).
                                       121

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APPENDIX 1.  (continued).
Scenedesmus bijuga (Turp.) Lagerh.
Scenedesmus bijuga var. alternans (Reinsch) Hansg.
Scenedesmus corallinus Chod.
Scenedesmus denticulatus var. australis Playfair
Scenedesmus denticulatus Lagerh.
Scenedesmus dimorphus Kiitz.
Scenedesmus falcatus Chod.
Scenedesmus granulatus West and West
Scenedesmus hystrix Lagerh.
Scenedesmus incrassatulus Bohl.
Scenedesmus intermedius Chod.
Scenedesmus jovis Chod.
Scenedesmus lefervii Defl.
Scenedesmus longus Meyen
Scenedesmus quadricauda (Turp.) Breb.
Scenedesmus quadricauda var. longispina (Chod.) G.M. Sm.
Scenedesmus quadricauda var. maximus West and West
Scenedesmus quadricauda var. parvus G.M. Sm.
Scenedesmus quadricauda var. quadrispina (Chod.) G.M. Sm.
Scenedesmus sempervirens Chod.
Scenedesmus serratus (Corda) Bohl.
Scenedesmus tetradesmiformis (Woloszynska) Chod.
Schroederia setigera (Schroed.) Lemm.
Selenastrum bibraianum Reinsch
Selenastrum westii G.M. Sm.
Selenastrum gracile Reinsch
Sestosoma  sp. //I
Siderocystopsis sp. #1
Sorastrum  sp. #1
Sphaerocystis schroeteri Chod.
Staurastrum paradoxum  Meyen
Tetraedron caudatum (Corda)  Hansg,
Tetraedron hastatum (Reinsch) Hansg.
Tetraedron minimum (A. Br.)  Hansg.
Tetraedron trigonum (Nag.) Hansg.
Tetraedron trigonum var. setigerum (Archer) Lemm.
Tetrastrum staurogeniaeforme (Schroed.) Lemm.
Trochiscia sp. #1
Ulothrix subconstricta G.S.  West
Ulothrix sp. //I
Undetermined green colony  sp. //I
Undetermined green colony  sp. #2
Undetermined green colony  sp. #3
Undetermined green filament  sp. //I
Undetermined green filament  sp. #4
Undetermined green filament  sp. #5

(continued).
                                       122

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APPENDIX 1.  (continued).
Westella linearis G.M. Sm.
Xanthidium antilopaeum var. depauperatum West and West
CYANOPHYTA

Agmenellum quadruplicatum (Menegh.) Breb.
Anabaena flos-aquae (Lyngb.) Breb.
Anabaena spiroides var. crassa Lemm.
Anabaena subcylindrica Borge
Anabaena zinserlingii Kossinskaja
Anabaena sp. #2
Anacystis cyanea (Kiitz.) Dr. and Daily
Anacystis dimidiata (Kiitz.) Dr. and Daily
Anacystis incerta (Lemm.) Dr. and Daily
Anacystis thermalis (Menegh) Dr. and Daily
Aphanizomenon flos-aquae (Lyngb.) Bre"b.
Chroococcus dispersus (Keissl.) Lemm.
Coccochloris sp. #1
Dactylococcopsis acicularis Lemm.
Gomphosphaeria aponina Ku'tz.
Gomphosphaeria lacustris Chod.
Gomphosphaeria wichurae (Hilse) Dr. and Daily
Microcoleus vaginatus (Vauch.) Com.
Oscillatoria bornetii Zukal
Oscillatoria limnetica Lemm.
Oscillatoria retzii Ag.
Oscillatoria sp. #1
Oscillatoria sp. #2
Plectonema sp. #1
Schizothrix calcicola (Ag.) Com.
Undetermined blue-green filament #1
Undetermined blue-green filament #2


PYRRHOPHYTA

Ceratium hirundinella (O.F. Mull.) Shrank
Glenodimium sp. #1
Gymnodinium helveticum Penard
Gymnodinium sp. #1
Hemidinium sp. #1
Peridinium aciculiferum (Lemm.) Lemm.
Peridinium cinctum (Mull.) Ehr.
Peridinium lindemanii Lef.
Peridinium sp. #1
Peridinium sp. #2

 (continued).

                                        123

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APPENDIX 1.  (continued).
EUGLENOPHYTA

Euglena allorgei Defl.
Euglena acus Ehr.
Euglena viridis Ehr.
Lepocinclis sp. #1
Phacus sp. //I
Tracholomonas lacustris Drezep.
Tracholomonas volvocina Ehr.
Trachelomonas sp. #1
SCHIZOPHYTA

Beggiatoa alba (Vauch.) Trev.
                                      124

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                                         TECHNICAL REPORT DATA
                                 (Fttatt read irutrucriom on i>u rrrtnt
1. REPORT NO.
     EPA-600/3-83-0.75
                                   2.
                                                                         RECI'I
      'OBW-tCCESaiON NO.
      PBF.S     25&035
4. TITL1 AND 3UST1TLI
 Effects  of Phosphorus Loading  on  Phytoplankton Distri-
 bution and Certain  Aspects of  Cytology  in  Saginaw Bay,
 Lake  Huron
  REPORT DATB
    August 1983
•.PERFORMING ORGANIZATION CODE
 . AUTHOR(S)'                                 ~
 E.  F. Stoermer,  L.  Sicko-Goad,  and L.  C.  Frey
  PERFORMING ORGANIZATION REPORT NO.
 . PERFORMING ORGANIZATION NAMI AND ADORES*
 Great Lakes  Research  Division
 The University of  Michigan
 Ann Arbor, Michigan   48109
                                                                       10. PROGRAM ELEMENT NO.
11. CONTRAC
 12. SPONSORING AGENCY NAME AND ADDRESS
   Environmental  Research  Laboratory
   Office of Research  and  Development
   U.S.  Environmental  Protection Agency
   Duluth.  MM 5580.4
 13. TYPE Of REPORT AND PERIOD COVERED
 14. SPONSORING AGENCY CODE

     EPA/60C703
 IS. SUPPLEMENTARY NOTES
 16
                .
  Saginaw Bay has always  been one of the more productive regions of the Great Lakes  system.  At the present
  time, It Is also one of the most modified.  Excessive nutrient and conservative  element  loadings are
  factors which have led  to  severe perturbation  of  primary producer communities In the region.  Because of
  the physical dynamics of the bay region,  Idealized dilution gradients are grossly  modified by transport of
  water masses and their  entrained chemical  constituents, fauna and flora Into, as well as away from, the   ;
  bay.  However, there appears to ba considerable  selection among population components of the assemblages
  transported.  For example, blue-green algae appear to be conserved In the bay while diatoms are subjected  :
  to great losses.                                                                      '                 !

  The major, effort In this  Investigation was to  provide data on phytoplankton blovolume which would support
  a model of processes occurring  In Saginaw  Bay.  A method of estimating the actual  vlaole fraction of the
  cell volumes of representatives of the various physiological groups of phytoplankton found  in Saginaw Bay
  was developed, and polyphosphate body formation  was  studied..  Results showed that  substantial
  phytopl ankto'n populations  were  exported from the bay to Lake Huron.  Under average wind  conditions, most
  export occurred along the  southern coast.   These populations were then entrained .In the  general Lake Huron
  circulation and were spread down the Michigan  coast  southward from the bay.  Under certain advectlve
  conditions, however, phytoplankton were discharged from the bay either to the north or' directly offshore.

  Cytologlcal analysis showed that many species  sequestered phosphorus  In excess of  their  immediate        >
  physiological needs, In the form of polyphosphate bodies.  Populations exported  from the bay also
  contained .these polyphosphate bodies.  Analysis  of the polyphosphate  bodies showed that  significant
  quantities of certain toxic metals, notably lead,  were  Incorporated  into these Inclusions.

  Analysis of the relationship of total phytoplankton  cell volume to protoplasmic  constituent volume showed
  that crude cell volume  measurements furnished  a  poor estimate of actual I I vlng blomass  |n many
  populations.  It was concluded  that more refined techniques are required to correctly convert estimates of
       number to BStlnmtre nf hlnmasi.
                                       KIY WORDS AND DOCUMENT ANALYSIS
                       DESCRIPTORS
                                                        b.lOENTIPlERS/OPEN ENDED TERMJI
                 c.  COSATi Field/Croup
  It. DISTRIBUTION STATEMENT
   JRFLEASE 10 PUBLIC
                                                         It. SECURITY CLASS (This Riport)
                                                         UNCLASSIFIED
                  21. NO. OP PAO«f
                        135
                                                         20. SECURITY CLAM (T*il p*f«)
                                                          UNCLASSIFIED
                                                                                        22. PRICI
  EPA Pm 7HO-1 (Re*. 4-77)   PMIVIOUI COITION 11 O«»OI_«T«

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