COMPARISON OF CILIATE COMMUNITIES IN THE ANOXIC HYPOLIMNIA OF 3 LAKES- GENERAL FEATURES AND THE INFLUENCE OF LAKE CHARACTERISTICS

The ciliate communities and their food sources were investigated in th e anoxic hypolimnia of three lakes with differing water chemistry. Bac terial biomass and, as a result, the biomass of bacterivorous ciliates were correlated with lake trophy. Additionally, high sulfate and sulf ide concentrations led to high bacterial biomass of sulfate reducers a nd anaerobic phototrophic and heterotrophic bacteria, which in turn su stained large ciliate populations. The anaerobic ciliate communities o f the lakes shared many characteristics. They were comprised of the sa me or closely related species: this was attributed to a low diversity of food sources. Ciliate to prey biomass ratios were 1.2-3.8% which is consistent with a low theoretical growth efficiency of anaerobic meta bolism. Grazing pressure on anaerobic ciliates by metazoa was insignif icant. In all three lakes, ciliate populations showed distinct vertica l non-random distribution patterns which were often correlated with th e distribution of the corresponding food sources. It is suggested that the microbial communities in anoxic water bodies are largely influenc ed by few common environmental conditions and are therefore often inha bited by similarly structured ciliate communities.