On the biological productivity of the Azov Sea took first place in the world most developed phytoplankton and benthos. Phytoplankton consists of (in%): of diatoms - 55, peridian - 41,2, and blue-green algae - 2,2. Among the biomass of benthic mollusks dominate. Their skeletal remains provided by calcium carbonate, have considerable weight in shaping the modern sediment accumulation and surface bodies.
Hydrochemical characteristics of the Azov Sea are formed primarily under the influence of abundant inflow of river water (up to 12% of the volume of water) and hindered water exchange with the Black Sea.
The salinity of the sea to the regulation of the Don was three times less than the average salinity of the ocean. Its value at the surface varied from 1 ppm at the mouth of the Don to 10.5 per cent in the central part of the sea and 11.5 ppm in the Kerch Strait. After you create Tsimlyansk hydroelectric saltiness of the sea began to increase (up to 13 ppm in the central part). The average seasonal salinity values rarely reach 1-2 per cent.
The water contains very little salt in the northern part of the Azov Sea. For this reason, the sea freezes easily, so until it was navigable by icebreakers from December to mid-April. The southern part of the sea does not freeze and remains a moderate temperature.
During the XX century almost all more or less large rivers flowing into the Sea of Azov, were blocked by dams to create reservoirs. This led to a significant reduction in discharge of fresh water and silt into the sea.