Looking Backward to the Problem of the Deep-Sea Caspian Fauna

Abstract

The causes of strong decrease of biomass, number and species diversity of the benthos at the depth 60-100 m and absent of specific deep-sea fauna in Caspian are represented below. The reason of this phenomenon is complex of factors: unstable oxygen conditions in deep-sea valleys, worse trophic conditions than on shelf and formation of bottom fauna under strong grazing pressure of sturgeons. Due to constant grazing pressure there is always place for the juveniles that decrease or even eliminate intraspecific competition for the place. In conditions of weak competition species have no cause to colonize new place that stopped formation of deep-sea species.

Keywords

• Caspian
• benthos
• vertical distribution
• deep-sea fauna
• sturgeon's grazing pressure