Zoobenthos cornmunities on stony beach of Lake Baikal

摘要

Five macrozoobenthos communities were found on stony beaches of southern Lake Baikal using the Vorob'ev approach. Amphipods were dominants in three communities, oligochaetes prevailed in two others; dominance of species is determined by sizes substratum pores. The Eulimnogammarus verrucosus community (24 g/m~2 biomass) is typicaf of the sediments composed of pebbles and boulders. The E. vittatus community (2-40 g/m ) occurs on grounds of medium and coarse pebbles, the E. cyaneus one (0.2-135 g/m~2) prefers grounds of fine and medium pebbles. The Mesenchytraeus bungei community (0.4-19 g/m~2) is formed on fine pebbles and gravel, the Propappus volki one (2 g/m~2)-on fine gravel-sandy grounds. The beach zone is ecotone for 2 communities, E. verrucosus and E. vittatus, which are formed here for a short period early in July. The rest communities are characteristic of the Baikal beach zone. Hydrodynamic effect is the main abiotic factor influencing a community. During periods of weak hedrodynamic stress (May-August) communities develop in the beach zone with appropriate grounds. While increasing the hydrodynamic effect on the beach (September-December). the communities migrate to the zones of weak hydrodynamic stress, but at the water edge they are absent.