An Ecological Study of Benthic Organisms in Three Illinois River Flood Plain Lakes

Abstract

This paper is concerned largely with the dynamics and changes in the benthic populations of three flood plain lakes located along the Illinois River near Havana, Illinois. For a number of years these lakes have been affected by sewage and industrial pollution from the Illinois River. Prior to 1926 Richardson (1921a,b; 1925a,b; and 1928) studied the bottom fauna of the Illinois River and certain of its flood plain lakes. Two of the lakes included in Richardson's work were studied during the present investigation. Both the human population and industries along the Illinois River have nearly doubled since Richardson's (op. cit.) studies were made. In 1913-14 Richardson (1921a) found that benthic organisms in the river and lakes in the vicinity of Havana (Fig. 1) were those normally found in relatively clean waters. Between 1917 and 1920 there was an increase in pollution in the river which wiped out most of the former clean water species in the Havana area (Richardson, 1925b and 1928). By 1925 there had been only a mild improvement in sanitary conditions of the river. Improvements apparently have occurred in the sanitary conditions of the river since 1925. Sewage disposal plants built after 1925 in most urban areas along the river above Havana have helped to reduce pollution in the river. In the 1930's several large navigation dams vere constructed on the river, and they have tended to reduce the rate of flow of the river, thereby, allowing more time for a natural breakdown of certain pollutants. However, pollution in the form of silt has greatly increased in the river and its flood plain lakes since the time Richardson made his investigations.