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Document Type

Thesis - University Access Only

Award Date

1990

Degree Name

Master of Science (MS)

Department

Biology

Abstract

For many people, the major factors thought to determine lake water quality are algal bloom density and water transparency. Excessive algal densities may result in anoxic conditions within a lake which may produce a fish-kill. Recreational and lake front property values are also decreased when annual blooms of algae produce a "scum" that may clog motor inlets and cause unfavorable swimming conditions. An unpleasant odor also often accompanies algal bloom decomposition. Algae and water transparency are influenced by chemical nutrient loads held by the water, solar radiation available to the phytoplankton for photosynthesis, wind velocity, water temperature, basin size and depth, and predation by planktonic animals. This thesis is part of the Oakwood Lakes System Study (OLSS). That study is dedicated to identifying factors which may be contributing to the hypertrophy (excessive nutrients loads held by the water) of the Oakwood Lakes. It is necessary to evaluate which factors are influencing the system in order to objectively determine an appropriate lake restoration process. Lake restoration is usually performed on lakes to increase that body's value for a particular purpose. This purpose may range from commercial use such as fishing to recreational use. The extent to which those restoration processes are deemed. successful will not be judged by the same criteria. A management process aimed at increasing fish yield may not be concerned about the lake water's clarity but only that the fish populations be increased. Conversely, a management process dedicated to increasing the recreational and lake front property values of a particular lake may not concern itself with fish populations but instead with water transparency and algal bloom density. Many desires may be realized in the same lake restoration process. However, some bodies of water may not be good candidates for some restoration goals. Methods used in lake restoration range from direct restructuring of fish populations (biomanipulation), to changing the methods of managing the lands that are included in the watershed, such as Best Management Practices (BMP's). All lake restoration steps are based on underlying beliefs. Biomanipulation would be used to reorganize the species interactions found in a particular lake. This restoration technique is based on the belief that water quality is primarily controlled by the biota found within the lake itself. BMP's are implemented to reduce the nutrients carried into the lake water from run-off and ground water. This restoration technique is based on the belief that water quality and algal bloom intensity are limited by nutrients loads found in the water body. Before beginning [sic] a restoration process, a study must be conducted to identify [sic] the controlling factors which govern a water body and thus determine which restoration steps, if any, are appropriate. The objectives of this study are: (1) To determine the distribution and abundance of the major algal and zooplankton species in the Oakwood Lakes. (2) To evaluate the relative importance of nutrient levels, other plankton species present, and physical factors in explaining the variations in the abundance of algal species. (3) To evaluate the relative importance of other plankton species and physical factors in explaining variations in zooplankton species abundance. (4) To evaluate the relative importance of other plankton species and physical factors in explaining variations in water transparency. (5) To compare seasonal changes in the Oakwood Lakes system with the seasonal changes in other lakes.

Library of Congress Subject Headings

Phytoplankton -- Oakwood Lakes (S.D.) -- Measurement
Zooplankton -- Oakwood Lakes (S.D.) -- Measurement
Water quality -- Oakwood Lakes (S.D.) -- Measurement

Format

application/pdf

Number of Pages

124

Publisher

South Dakota State University

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