Species composition and distribution of macrozoobenthos have been studied in the shallow water zone (0-20 m) of Southern Lake Baikal (Bolshiye Koty Bay). The amount of taxa recorded reached up to 244 species distributed among 16 distinctive communities of complex structure and high species diversity. The Shannon index of specific diversity was found to vary between 2.9 and 4.8 bits. Mosaic spatial distribution of communities is controlled by both biotic and abiotic factors. Trophic zones with respect to the bottom-dwellers are determined by two lithodynamic phenomena: washout and accumulation of thin deposits (fine to medium silt and mud). The bottom with coarse clastic material (pebbles and boulders), where fine sediments are eroded and resuspended, is dominated by immobile and mobile sestonophagous species as well as by the communities dominated by detrito- and phytophagous species. Areas with soft fine sediments are dominated by macro-invertebrates, which ingest the substrate indiscriminately.