United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA-600/S3-83-075 Nov. 1983
x°/ERA Project Summary
Effects of Phosphorus Loading
on Phytoplankton Distribution
and Certain Aspects of
Cytology in Saginaw Bay, Lake
Huron
E.F. Stoermer, L Sicko-Goad, and LC. Frey
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 consti-
tuents, fauna and flora into, as well as
away from, the Bay. However, there
appears to be 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
biovolume that would support a model
of processes occurring in Saginaw
Bay. A method of estimating the actual
viable fraction of the cell volumes of
representatives of the various physio-
logical groups of phytoplankton found
in Saginaw Bay was developed, and
polyphosphate body formation was
studied. Results showed that substan-
tial phytoplankton 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 advective conditions,
however, phytoplankton were dis-
charged from the Bay either to the north
or directly offshore.
Cytological analysis showed that
many species sequestered phosphorus
in excess of their immediate physiologi-
cal 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 quanti-
ties of certain toxic metals, notably
lead, were incorporated into these
inclusions.
Analysis of the relationship of total
phytoplankton cell volume to proto-
plasmic constituent volume showed
that crude cell volume measurements
furnished a poor estimate of actual
living biomass in many populations. It
was concluded that more refined
techniques are required to correctly
convert estimates of cell number to
estimates of biomass.
This Project Summary was developed
by EPA's Environmental Research
Laboratory, Duluth. MN. to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Saginaw Bay has always been one of
the more productive regions within the
Great Lakes system. The productivity of
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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 industrial base. Once
cleared of its natural vegetation, much of
the land was found suitable for intensive
agricultural practices. Finally, the pres-
ence of subsurface resources, primarily
petroleum and salt, made possible the
establishment of one of the midwest's
centers of chemical industry. Unfortu-
nately, the development of the Saginaw-
Bay City-Mid I and industrial complex and
intensive regional agriculture proceeded
at the expense of 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. It should be pointed out that the
perturbation of primary producer com-
munities 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 phyto-
plankton and benthic algal flora also
reflects the effects of extreme conserva-
tive element loadings. Although these
loadings have apparently been decreased
to some degree in recent years, the flora
of the Bay still contains many elements
usually found in brackish water localities.
Finally, although not experimentally
documented, certain population distribu-
tions 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. 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. There appears to be considerable
selection among the population compo-
nents of the assemblage(s) being trans-
ported. 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 At the same time,
water masses from Lake Huron, containing
biological communities adapted to phys-
ical and chemical conditions found in the
open lake, are imported into the Bay. The
purpose of this large scale investigation
was to provide data on phytoplankton
biovolume which would support a model
of processes occurring in the Bay.
Biovolumes were estimated and poly-
phosphate bodies were examined in
many species.
Parts of this investigation were pre-
viously reported, namely: studies of
primary consumer organisms in Saginaw
Bay and southern Lake Huron (Gannon,
in prep; Stemberger et al. 1979), studies of
physical and chemical conditions in
Saginaw Bay (Smith et al. 1977), a study
of phytoplankton abundance and distri-
bution in southern Lake Huron (Stoermer
and Kreis, et al. 1980) a process oriented
model of Saginaw Bay (Biermann, et al.
1980). Although each of these studies
was the responsibility of a different
laboratory, common sampling techniques
were used. Pertinent data are reproduced
in this report, detailed methods are given
only for bivolume calculations and
polyphosphate body studies.
In most instances phytoplankton samples
were taken by submersible pump and
fixed immediately with 4%gluteraldehyde.
Samples were kept on ice in the dark until
they were processed into slides by the
membrane clearing technique. Sampling
cruises were conducted at approximately
monthly intervals over a 2-year period.
Population estimates were developed
from 1 mm strip counts of randomly
selected areas of the slide preparations.
Populations were enumerated and di-
mensions of the taxa recorded. The
volume data were converted to an
estimate of carbon biomass. Volume
density estimates of cell components (cell
wall, chloroplasts, vacuoles, storage
products, and remaining cytoplasmic
material) were obtained by electron
microscope morphometric methods.
Estimates of volume density were deter-
mined using both paper profile cut-and-
weigh and grid-point-counting techniques.
Eight taxa were selected for quantitative
stereological analysis, including repre-
sentatives from the classes Cyanophyceae,
Bacillariophyceae, Euglenophyceae, Cryp-
tophyceae, Dinophyceae, and Prymne-
siophyceae. Seventy-five micrographs
were examined for each taxon, except
where scarcity of a particular taxon in the
water samples necessitated a somewhai
reduced sample size. In all cases,
examination of coefficients of variation
and plots of cumulative means and
variances indicated adequate sampling ol
the material. A transparent 0.5-cm
square sampling lattice was superimposed
over the micrographs for quantitative
measurements.
Cell volume estimates were obtained
from light microscopic examination of
cells from the same assemblages used for
quantitative stereological analysis.
Both x-ray energy dispersive analysis
(to confirm the presence of phosphorus)
and light microscopy were used in the
examination of polyphosphate bodies.
The results of the study reported here
indicate that the problems associated
with biovolume estimates can be both
understood and, in many cases, minimized.
The inherent cellular organization of
some species contributes significantly to
the error of biomass calculations currently
in use. Corrected cellular volumes
determined from the morphometric data
by subtracting the volume of inert
structures from the total volumes were
found in this study. Table 1 indicates the
striking differences found in various taxa.
Table 1. Percent of Total Cellular Volume
Identified as "Metabolizing
Biovolume" for Selected Taxa
A. flos-aquae
S. binderanus
F. capucina
E. viridis
C. erosa
P. lindemann:
Haptophyte sp. #1
Haptophyte so. #2
64.1
29.9
43.5
44.6
67.7
58.6
58.3
81.9
Polyphosphate inclusion bodies were
widely found in diatoms and even in algae
in Saginaw Bay. The abundance of these
bodies corresponds to the usual pattern
of greatest total phytoplankton density,
and to the most probable area of excur-
sion of materials from the Bay.
Conclusions and
Recommendations
1. The use of electron microscopic
morphometric analysis leads to a
more accurate estimate of biovolume
than other methods presently in
use.
2. The ecological causes and conse-
quences of polyphosphate storage
in phytoplankton may be important
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in evaluating impact of areas such
as Saginaw Bay on the rest of the
Great Lakes system.
3. It was previously assumed that
polyphosphate body formation was
important only in prokaryotic or-
ganisms. The results of this study
suggest that the mechanism is
present in most of the major physio-
logical groups present in the Great
Lakes. Notable exceptions were the
Cryptomonads and Dinoflagellates.
Although induction was not attempted
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.
4. These results indicate that heavy
metals may be sequestered in
polyphosphate bodies.
5. Meteorological conditions have a
strong influence on the eventual
fate of materials entering the Bay,
and on the fate of phytoplankton
populations generated in the Bay.
Further research should be devoted
to the effects of conditions which
force strong advective events on
processes in Lake Huron.
chemical factors in Saginaw Bay (Lake
Huron). U.S. Environmental Protection
Agency, EPA-600/3-77-125. 143 pp.
Stemberger, R.S., Gannon, J.E. and
Bricker, F.J. 1979. Spatial and seasonal
structure of rotifer communities in
Lake Huron. U.S. Environmental Pro-
tection Agency, EPA-600/3-79-085.
160 pp.
Stoermer, E.F., and Kreis, R.G. 1980.
Phytoplankton composition and abun-
dance in southern Lake Huron. Univ.
Michigan, Great Lakes Research Divi-
sion, Special Report No. 65. 382 pp.
E. F. Stoermer, L Sicko-Goad, and L C. Frey are with the University of Michigan.
Ann Arbor. Ml 48109.
Nelson A. Thomas is the EPA Project Officer (see below).
The complete report, entitled "Effects of Phosphorus Loading on Phytoplankton
Distribution and Certain Aspects of Cytology in Saginaw Bay, Lake Huron,"
(Order No. PB 83-250 035; Cost: $14.50, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
6201 Congdon Blvd.
Duluth. MN 55804
A-US GOVERNMENT PRINTING OFFICE 1983-659-017/7222
References
Bierman, V.J., Dolan, D.M., Stoermer,
E.F., Gannon, J.E., and Smith, V.E.
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.
Gannon, J.E., Bricker, F.J. In preparation.
Spatial and seasonal structure of
crustacean zooplankton communities
in Lake Huron. U.S. Environmental
Protection Agency.
Schelske, C.L, Moll, R.A., and Simmons,
M.S. 1980. Limnological conditions in
southern Lake Huron, 1974 and 1975.
U.S. Environmental Protection Agency,
EPA-600/3-80-74. 178 pp.
Smith, V.E., Lee, K.W., Filkins, J.C.,
Hartwell, K.W., Rygwelski, K.R. and
Townsend, J.M. 1977. Survey of
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