Review: The Caspian Sea benthos: Unique fauna and community formed under strong grazing pressure

A quantitative comparison of the benthic distribution in the Middle and Southern Caspian Sea, using benthos distribution maps with previously published materials, showed that the benthic communities is stable and interrupted only by the introduction of new species. The bottom community is dominated by small-size organisms, mainly fry and young and the benthic biomass is low although its efficiency as prey for higher trophic levels is high even though carnivores are almost absent in the bottom community. At depths of c.100 m the benthos biomass and species diversity sharply decreases showing these features as a unique case of a bottom fauna and bottom community formed and modified under the influence of a severe grazing pressure by the sturgeon (Acipenser spp.) during very long periods. It is therefore suggested that grazing pressure has become the most important forcing function for the diversity and development of the bottom community.