Present-day characteristics and trends of long-term changes in ecological and toxicological conditions of the Tsimlyansk Reservoir

The analysis of ecological and toxicological conditions of the Tsimlyansk Reservoir and of trends of long-term variations of hydrochemical, hydrobiological, and biotesting parameters is carried out on the basis of long-term data of Roshydromet regular observations (1984?C1991) and authors?? studies (1990, 2006?C2007). It is revealed that, according to the complex of chemical parameters, the water pollution level decreased by the end of the period and is relatively low at present, although the pollution is of stable nature and the toxic and carcinogenic compounds are discovered in the water and in bottom sediments. The most dangerous display of the reservoir eutrophication is a ??bloom?? of algae characterized by the prevalence of blue-green algae (Cyanophyta) amounting to 100% of the total biomass in some samples; the species being able to discharge the toxins to the water (Aphanisomenon flos-aquae, Microcystis aeruginosa, Anabaena flos-aquae) often prevail. During biotesting, the samples of water and bottom sediments in a number of cases exerted a toxic effect on the water organisms and, most likely, the toxicity increases with time. Although different parts of the reservoir differ considerably in ecological and toxicological parameters, an ecologically unfavorable situation emerged in the reservoir ecosystem due to the pollution, eutrophication, and toxicophication.