Abstract |
Water samples and samples of plankton were collected from Lake Herman and Enemy Swim Lake, both located in eastern South Dakota, from July, 1967 through June, 1970. All samples were analyzed for selected chemical characteristics and for phytoplankton population. Results indicated that both lakes are eutrophic but Lake Herman is considerably more productive than Enemy Swim. Concentrations of most ions were from 50 per cent to 100 per cent greater in Lake Herman than in Enemy Swim and phytoplankton populations were often 100 times more dense in Lake Herman. Relative abundance of major ions were similar in both lakes except that sulfate was the dominant anion in Lake Herman and bicarbonate - carbonate in Enemy Swim. Both lakes showed uniform chemical conditions from one sampling station to another and similar annual dynamics marked by a sharp increase to peak levels of all major ions under ice cover. Phytoplankton populations were dominated by blue-green algae in Lake Herman, and by diatoms in Enemy Swim. Numbers and kinds of algae varied from season-to-season and from year-to-year indicating that intensive long term sampling is necessary in any study of plankton dynamics in these lakes. The greater eutrophication of Lake Herman appears related to the intensive cultivation of its watershed. (Author) |