The Structure of a Macroinvertebrate Community in a Northern German Lake Outlet (Lake Belau,Schleswig-Holstein) with Special Emphasis on Abundance,Biomass and Secondary Production

The structure of macroinvertebrate communities was studied at I I sampling sites of the outlet of Lake Belau in the lowlands of northern Germany. To describe the structures of macrobenthic animal communities three different units were examined: abundance, biomass, and secondary production. 112 taxa were collected from the entire stream. The numbers of species ranged from 31 (fine sand) to 70 (submerged macrophytes). For the stream, average macroinvertebrate density was 18.400 ind. M^?1. Density was highest at the macrophytes amounting to 35,630 individuals per m², and lowest in the pure sand with only 3,900 ind. M^?2. Average biomass (dry mass) was 194 g DM m^?2 varying from 9.8 (peat) to 381 g DM m^?2 (gravel with mollusk shells near the upstream lake). For the stream, average annual production was 129 g DM m^?2 varying from 15 (peat) to 286 g DM m^?2 (macrophytes). The highest values for each unit were found in stream sections with gravel and submerged macrophytes. Lower values occured in sections that contained peat and sand. Usually, a single structure of the macroinvertebrate community was dominated by less than ten taxa, which varied at each sampling site depending on the units observed.