Carbonate Beaches of the Eastern Part of the Sea of Azov under Anthropogenic Impact

A characteristic peculiarity of mineral composition of bottom sediments in the Sea of Azov is their high carbonate content. The sea has features characteristic to weakly mineralized basins both of arid and humid zones. Accumulation of calcium carbonate in bottom sediments of the Sea of Azov is characterized by spatial irregularity of its distribution. A study of chemical composition of bottom sediments and CaCo₃ content in them has confirmed the absence of connection between the general amount of calcium carbonate and granulometric composition of sediments. CaCo₃ percentage in surface layer of bottom sediments varies from 1 to 90%. But its natural increase is observed in the regions with the highest benthos biomass. An intensity of biogenic carbonate accumulation in the Sea of Azov is not a constant, and it is an integral reflection of the mollusks' productivity. As the research has shown, removal of continental run-off and, as a consequence, increase of sea water mineralization, promotes an essential change of structure and productivity of benthos biocenosis. As a whole, carbonate accumulation in the Sea of Azov is characterized by an extraordinary dynamics. A supply of carbonate matter of benthos organisms to the sea bottom is determined first of all by ecological criteria. Hence, before considering hydrodynamic conditions under which shells of mollusks and other carbonate-forming organisms are carried out of the area of habitation, we must ascertain reasons of their death. Since the 60-ies till now the Sea of Azov basin and its carbonate beaches suffer from a great anthropogenic impact. It is in the discharge into rivers of different pollutants including rather toxic ones for hydrobionts; erection of water storage basins and hydroengineering complexes on large rivers; construction of ports, jetties and other hydraulic systems in the nearshore zone. The influence of these factors resulted in increasing of sea water salinity and in reducing of solid run-off. As a result, here occurs dislodgment of biocenosis from the usual zones of their habitation, which is accompanied by the death of a part of mollusks. The process of the coastal erosion began, living conditions for hydrobionts became worse, the fish-productivity of the basin fell in tens times. On the whole, this region is a good example of an irrational use of natural resources.