United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA-600/S3-84-016 Mar 1984
&EPA Project Summary
The Nutritional
Ecology of Great Lakes
Cladophora glomerata
Gerald C. Gerloff and J. Vic Muth
Various bioassays, primarily plant
analyses, were utilized to evaluate
relative nutrient supplies and primary
growth limiting nutrients for Cladophora
glomerata growth in parts of Green Bay,
Lake Michigan, known to differ marked-
ly in degree of pollution. Preliminary
studies indicated that emphasis should
be placed on evaluations of five nutri-
ents: phosphorus, nitrogen, boron, sul-
fur, and vitamin B,. The bioassays in-
dicated that phosphorus very likely is
the critical nutrient in nuisance C.
glomerata growths and that at times
phosphorus supply actually is reduced
to growth-limiting concentrations.
However, the possibility that vitamin B,
may at times be critical for C. glomerata
cannot as yet be eliminated.
The bioassays employed (total P, hot-
water-extractable P, and alkaline
phosphatase activity) were in agree-
ment and consistent in indicating that
phosphorus availability limited C.
glomerata growth.
In further development of plant
analysis as a bioassay, nitrogen and
phosphorus critical concentrations were
demonstrated to be relatively constant
in C. glomerata of different ages and
grown under various environmental
conditions which would affect the rate
and amount of growth.
A requirement for vitamin B,2 and very
high requirements for sulfur and boron
were confirmed as unusual nutritional
features of C. glomerata. Comparisons
with the requirements for other green
and blue-green algae established the
uniqueness of the high sulfur require-
ment for C. glomerata. There was no in-
dication of sulfur deficiency in Clado-
phora sp. from the Great Lakes.
Data obtained from solution replace-
ment cultures indicated that, even when
adequate total phosphorus is available,
the growth of C. glomerata becomes
less than optimum at phosphorus solu-
tion concentrations of 0.014 ppm and
less, and at potassium and calcium con-
centrations below 0.18 and 0.24 ppm,
respectively. This supports the concept
of critical concentrations in the water
for optimum C. glomerata growth.
Trace element studies indicated that
C. glomerata requires an inorganic
nutrient not generally recognized as
essential for plant growth. The alga
responded positively and significantly to
a mixture of elements suspected to be
essential. However, systematic elimina-
tion of elements from the mixture failed
to identify one element as responsible
for the yield increases. The situation is
more complex than anticipated.
The culture and nutrition of Nitzschia
palea, a very common diatom in the
Great Lakes, was investigated. Silicon
concentrations well above those in
available media were essential for suc-
cessful laboratory growth of /V. palea.
Various algae, primarily from Lake
Michigan, failed to produce inhibitors of
C. glomerata growth to a degree that
would suggest they are important in the
ecology of C. glomerata in the Great
Lakes.
Laboratory studies were initiated on
the toxicity of heavy metals to C.
glomerata.
This report covers the period May 1,
1976 to September 30, 1978.
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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
The pollution of the Great Lakes with
municipal and industrial wastes has resulted
in increased growths of nuisance algae.
Filamentous green algae in the genus
Cladophora are among the most trou-
blesome of the nuisance organisms. The
development of measures for the reduction
of the Cladophora growths, based on
nutrient limitation, will be facilitated by an
understanding of the importance of specific
nutrients in the growth of Cladophora, i.e.,
the nutritional ecology of Cladophora. A
primary goal of this project has been to iden-
tify the nutrients, both inorganic and
organic, most likely to limit and control the
growth of C. glomerate in Lake Michigan.
A second goal was to continue experiments
on the nutrition of C. g/omerata. Plant
analysis was the diagnostic technique used
in the study.
For the bioassays, samples of C. g/o-
merata and of lake water were obtained
primarily at five Lake Michigan sites, four of
the sites on the Green Bay side of Door
County, and a fifth on the Lake Michigan
side. The sites were selected to represent a
range of pollution and fertility resulting from
the entry of the Fox River into lower Green
Bay.
C. g/omerata samples were obtained by
clipping filaments, indicated as healthy by
their green color, from heavy growths close
to rocks, the shore, or from rock-
breakwaters which extended out from the
shore. The algae samples were rinsed in
distilled water to remove contaminating
debris. Samples were hand-squeezed and
transported to the laboratory under refrigera-
tion. They were oven-dried and ground in a
Wiley mill. Analyses for N, P, S and B were
by generally accepted quantitative
techniques.
In the plant analysis bioassay, reduction
in the supply of an element to a growth con-
trolling level for a particular species at a par-
ticular site is indicated by a concentration of
the element in a sample of the species at or
below the critical concentration, the
minimum plant concentration which permits
optimum growth. A concentration above the
critical level indicates that the algae from the
site sampled were adequately supplied with
the element.
In the differential nutrient enrichment ex-
periments aliquots of lake water from specific
sites were enriched with the various
nutrients. Concentrations of added nutrients
were those in the synthetic culture medium
of Cladophora. One or several nutrients were
omitted in each treatment. After innocula-
tion with the C. glomerata, cultures were in-
cubated for 21 days under continuous
fluorescent light at a temperature of
23 ± 1 °C. Any element present in the lake
water in an amount adequate to support
50% of the yield in the complete medium in
lake water was considered unlikely to limit
algae growth under field conditions. Of the
nutrients tested, this eliminated calcium,
magnesium, manganese, molybdenum, zinc,
copper, boron, sulfur and vitamin B12 as
critical in C. g/omerata growth. Every enrich-
ment test indicated that four nutrients (N,
P, Fe and vitamin B,) were most likely to limit
growth of C. glomerata.
Yields of C. g/omerata in the enrichment
cultures were slightly better when nutrients
were added to lake water rather than distilled
water. This suggested that lake water con-
tains some unrecognized essential trace
nutrient, or that the ratios of nutrients in the
synthetic medium are not optimal.
Overall results indicated that phosphorus
is the key nutrient in nuisance growths of C.
g/omerata in Green Bay of Lake Michigan.
Conclusions
1. C. g/omerata becomes phosphorus defi-
cient in parts of Green Bay during late
summer. Phosphorus seems to be the
key nutrient in the development of
nuisance C. g/omerata growths.
2. There is a close correlation between
nutrient inputs to Green Bay and the
development of phosphorus deficie
in C. g/omerata.
3. C. g/omerata has extremely high ,
unique requirements for sulfur i
boron, but these elements are
critical in the nutritional ecology of
organism.
4. While phosphorus very likely is the I
factor in nuisance C. g/omer,
growths, the possibility that vitamin
is a critical nutrient cannot be elimina
at this time.
5. Relatively simple bioassays are availa
for evaluating nutrient supplies for
g/omerata.
6 Critical nitrogen and phosphorus cc
centrations, which are the basis
nutrient assays through plant analys
are relatively constant for C. glomen
under a variety of environmental cc
ditions and at various stages of grow
This is a critical point of support 1
plant analysis as a reliable nutrie
bioassay.
7. C. glomerata growth seems to be le
than optimal when the phosphor
solution concentration decreases
0.014 ppm and below.
8. Inhibitor production by common algi
probably is not a major factor in tl
ecology of C. glomerata.
9. An adequate supply of soluble silicon
a critical factor in the successf
laboratory culture of the diatom Nit
schia palea. Media commonly used fi
culturing blue-green and green alg<
contain inadequate silicon for optimui
growth of the diatom.
U S GOVERNMENT PRINTING OFFICE, 1984 — 759-015/76'
Gerald Gerloff and J. Vic Muth are with the University of Wisconsin, Madison, Wl
537O6.
Nelson A. Thomas is the EPA Project Officer (see below).
The complete report, entitled "The Nutritional Ecology of Great Lakes Cladophora
glomerata,"(Order No. PB 84-136 571; Cost: $16.00, 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
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