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Peterson, Walter F. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume LX (1972)

Bartell, Steven; Richman, Sumner
Kinetics of orthophosphate uptake by phytoplankton populations in Lake Winnebago,   pp. 147-178 PDF (8.7 MB)


Page 147

 147KINETICS OF ORTHOPHOSP HATE UPTAKE 
BY PHYTOPLANKTO'N POPULATIONS IN LAKE WINNEBAGO 
St-even Bartell and Sumner Richman 
ABSTRACT 
 The growth of natural phytoplankton populations of Lake Winnebago was investigated
with regard to orthophosphate limitation. An ascorbic acid-antimony modification
of a standard molybdenum blue colonimetric test for orthophosphate showed
a concentration of 94.0 ~ liter—' in late November, 1970. This
concentration
steadily decreased, through the winter months to a minimum of 29.0 ~ liter—'
in early February, 1971. With the removal of ice cover and increased allochthanous
addition of phosphate associated with the spring thaw, the orthophosphate
concentration increased to 109.0 ~ liter—' in early April. 
 A standard acetone extraction procedure showed that chlorophyll concentrations
followed a similar trend in seasonal variation. The 2.2 mg~ m3 concentration
found in the January 9, 1971 sample decreased to a minimum of 0.4 mg . m3
for the January 24 sample. The chlorophyll concentration gradually increased
to 20.8 mg~ m3 by early April. 
 Primary productivity measured by a standard ' 4C technique, increase in
biovolume determined by the Model B Coulten Counter, and chlorophyll production
were used to study the kinetics of orthophosphate uptake in enrichment experiments
where varied amounts of orthophosphate, ranging from 20 to 200 ~g liter—',
were added to samples of Lake Winnebago water. 
 The resulting changes in the rates of these parameters suggest that uptake
followed the Michaeli's—Menten equation, modified for nutrient
limitation
theory, for enriched samples collected on February 2 and February 20, 1971.
This model may also apply to the November and April populations; however,
a limitation in experimental design prohibited the calculation of Vmax and
K~. 
 Orthophosphate was determined to be a limiting factor for productivity in
Lake Winnebago over the winter months. 
I. Introduction and Background 
 Eutrophication refers specifically to the natural or artificial addition
of nutrients to aquatic ecosystems. This term has been more broadly interpreted
to include the physical, chemical, and 


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