Ecotoxicological assessment of water quality and ecosystem health: a case study of the Volga River.

A comprehensive assessment is presented of the ecotoxicological situation in the Volga River basin from the viewpoint of ecosystem health. Concentrations of organic and inorganic toxic substances in water are reported. Basic clinical and postmortem signs of fish intoxication are described; changes in the cellular structure of their organs and tissues, as well as disturbances in hemogenesis, developing under the effect of toxic agents, are characterized. The comparative characteristics of several microelements (Ni, Cu, Sr, Al, Zn, Co, Mn, Pb, Cd, Hg, As) found in fish are presented. The main disturbances to fish caused by the accumulation of microelements in their organs and tissues are also considered. Based on dose-effect dependencies calculated with respect to the total concentration of toxic substances, standardized to MPC, and fish health criteria, cases that exceed the critical levels of pollutants are demonstrated for the investigated river sections.