Spatial heterogeneity of hydrochemical and trophic characteristics of the Kuibyshev reservoir in summer

Non-uniform distribution of water chemistry and plankton in water areas of big reservoirs occurs under intensive flow regulation that, generally, pre-defines their productivity, self-purification and trophic behavior. This article represents the results of hydro-chemical and trophic spatial non-uniformity studies in morphometrically different areas of the Kuybyshev reservoir in summer periods of 2015 and 2016 years. Chemical and trophic parameters of the reservoir ecosystem were compared in years with different water content. Observation data show increase in water temperature, pH and organics content, as well as decrease in water specific conductivity and mineral nitrogen and phosphor contents from north to south along the length of the reservoir. The biggest values of phytoplankton biomass, integral primary production and integral destruction are observed in lower and central parts of the reservoir, while the upper part is featured by lower values pf photosynthesis. It was found that in hot period daily phytoplankton production of the Kuybyshev reservoir twice exceeds daily ingress of allochthonic organic substance with water afflux. In the Kuibyshev reservoir, which receives an influx of allochthonous matter, the intensity of destruction processes is higher than that of production processes, which indicates a good ability to self-purify the Volga waters.