It has been investigated the ecological status of the cooling pond of Zaporizhzhya Nuclear Power Plant (NPP) on the hydrochemical and toxicological indicators. The ecological water quality by most hydrochemical and hydrophysical indices corresponds to the class II, category 3, and is characterized as "fairly clean". However, according to the BOD5 index, the water quality is "satisfactory" (class III, category 4). By the contents of both nitrogen of nitrates and phosphorus of phosphates the water quality belongs to the class IV, category 6, as "bad, dirty water". The main anthropogenic pollutants are copper, iron, zinc, and fluorides. The ecological characteristics by their concentrations in the water correspond to the class III, and categories 4–5 of quality, which are "poorly and moderately polluted" water. Accumulation of toxic metals in the surface layer of the reservoir bottom sediments depends on their types, the minimal content is found in sandy sediments, and maximal one is in muddy sediments. The possibility of significant secondary pollution of the water environment by toxic metals is small under the hydrophysical and hydrochemical conditions typical for the cooling pond of Zaporizhzhya NPP. According to the calculations, the value of the average chemical index of ecological quality is "2.5", which characterizes the water of the Zaporizhzhya NPP cooling pond as "good" and "clean".
It had been determined the contents of total protein, albumin, glucose, urea and activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), α-amylase in 4-years old individuals of both sexes of prussian carp (Carassius gibelio Bloch, 1782) and roach (Rutilus rutilus Linnaeus, 1758) in different parts of the Zaporozhian Reservoir (Ukraine). The level of biochemical parameters depended on the extent of anthropogenic impact on the aquatic environment. Comparing to the prussian carp, Zaporozhian Reservoir roach was established to have a higher vulnerability to the effects of pollutants, that is why it can serve as a kind of test bioindicator for testing hydroecological system ihtiotoxicity.
The research was held in terms of Zaporozhian Reservoir (Ukraine) from 2014 till 2015 year. It was established that prussian carp (Carassius gibelio Bloch, 1782) and roach (Rutilus rutilus Linnaeus, 1758) underyearlings accumulate essential elements more extensively, especially zinc, comparing to adults ones. The species characteristic of heavy metals accumulation in the carp fish body was observed. The intensity level of erythropoiesis occurrence was higher in young fish of both species of carp fish. The specific features of cytometric characteristics of fish erythrocytes were identified: the relative amount of mature red blood cells prevailed in roach, and the area of mature red blood cells was significantly higher in prussian carp. In addition, in the young roach among immature forms of red blood cells significantly higher percentage of polychromatophil normoblasts was revealed.