Oligochaeta and Aphanoneura in two Northern German hardwater lakes of different trophic state

Abstract

Lake Haus and Lake Stechlin are well-characterized and intensely studied hardwater lakes located in the Baltic Lake District of Northern Germany. The former is classified as highly eutrophic, the latter is an oligotrophic hardwater lake. The way in which Oligochaeta and Aphanoneura species assemblages reflected the different trophic states of the lakes was investigated by a programme of qualitative and quantitative sampling over one year. This paper gives an account of the species occurrence in the two lakes. There were more species in the oligotrophic Lake Stechlin (56) than in the eutrophic Lake Haus (41), the number in the latter, however, is large for eutrophic lakes. The profundal of Lake Haus was devoid of any zoobenthos, probably because of anoxia, the profundal of Lake Stechlin exhibited an annelid species assemblage not found in other comparable oligotrophic lakes. In the littoral zone, species distribution patterns differ considerably between sites. At one site in Lake Stechlin, Potamodrilus fluviatilis was found, this being the first record of the species in inland lakes.