Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)




Two eutrophic northern prairie lakes, Lake Cochrane and Lake Hendricks, were sampled regularly for chemical characteristics, temperature, transparency, phytoplankton and zooplankton populations. Primary production was determined by the "light" and "dark" bottle technique. Values for the 1971 summer study period ranged from a low of 59.l7 mg C fixed/m2/hr. to a high of 296,67 with a mean of 151.67 for Lake Cochrane. Values for Lake Hendricks ranged from 25.00 to 194.17 with a mean of 110.83. The possibilities of nutrient limitation were investigated through nutrient enrichment experiments in the field. Production was generally not enhanced and was sometimes inhibited by the addition of selected nutrients. Results of the production studies show highest correlation with turbidity and natural levels of available phosphates and nitrates. There was little correlation with changes in temperature, light or any of the other nutrients. This study measured planktonic primary production on 13 dates during two algal bloom seasons (June through September). Studies were also undertaken to determine if the addition of selected. inorganic nutrients would alter production rates. The nutrient enrichment experiments were run simultaneously with the production studies so that variations in production by date compared with possible nutrient enrichment effects. Water chemistry, turbidity, and temperature were also monitored on the sample dates. Biological data collected included phytoplankton counts, zooplankton counts, and chlorophyll "a" determinations. This information, along with the results of the production and nutrient enrichment studies, was analyzed statistically to show interaction patterns in each lake.

Library of Congress Subject Headings

Lake Cochrane (S.D.)
Lake Hendricks (Minn.)



Number of Pages



South Dakota State University