Ecotoxicological assessment of water quality and ecosystem health: a case study of the Volga river / Moiseenko T. I., Gashkina N. A., Sharova Yu. N., Kudryavtseva L. P. // Ecotoxicology and Environmental Safety. - 2008. - Т. 71, № 3. - С. 837-850.

T.I. Moiseenko et al. / Ecotoxicology and Environmental Safety 71 (2008) 837-850 843 Thus, the accumulation of Ni in fish organisms depends on its concentration in the water, but the concentration of this metal in the water and fish of the Volga River is low. 4.7. Manganese Mn is usually considered to be of low toxicity. According to Musibono and Day (1999), Mn reduces the toxicity of such elements as Cu and Al, i.e., Mn possesses antagonistic properties in multicomponent water contamination. Mn is irregularly distributed in the Volga River water: the concentration of Mn in the Upper Volga was much higher than in the Lower. The concentration of Mn in fish organisms changes similarly: the most intense accumulation of Mn was observed in bream inhabiting the Upper Volga, and the maximum amount of this metal was found in the bream gills and skeleton (Table 3). A significant correlation was revealed between the concentration of Mn in fish organisms and in the respective water (for gills: r=0.68, p<0.025; for muscles: r = 0.67, p<0.025; for liver: r = 0.61, p <0.05). A close correlation was also revealed between the values of Mn concentration in different tissues and organs of the same fish individual, which testifies to synchronous bioaccu­ mulation of this metal depending on its concentration in the water. 4.8. Zinc, chromium, copper, and cobalt These are essential elements. No distinct patterns could be traced in the distributions of Zn, Cr, and Co concentrations in the Volga River water. As a rule, Cu, Zn, and Co accumulate in fish liver, where active metabolic processes take place. Their max­ imum concentration was found in the livers of Lower Volga bream (Table 3). It is well established that the rate of metabolic processes in fish is determined by the ambient temperature. If the concentrations of microelements in the water are similar, the rate of their bioaccumulation can depend on the temperature conditions. The availability of essential elements to functionally vital organs of bream inhabiting the Lower Volga is probably affected by the intensification of metabolic processes in warmer water. A correlation was found between the concentrations of Cu, Zn, and Co in fish muscles and the sum of annual temperatures exceeding 10 °C (Fig. 2), whereas no such correlation could be established between the concentrations of the above elements in the fish organs and in water. 4.9. Multimetal penetration The accumulation of microelements in fish organs and tissues causes microelementoses, i.e., changes in the ratio of microele­ ment concentrations in fish organs and tissues. A high correlation was established between the concentrations of certain elements in the bream organs, which testifies to the effect of pollution on the increase in the concentrations of the investigated microele­ ments in fish gills: Sr -»• (r = 0.87,p < 0.001) -e- Cd -»• (r = 0.96,p < 0.001) Al -»• (r = 0.78,p<0.005) -e- Cr, and in fish kidneys: Cr -»• (r = 0.53,p<0.1) -e- Sr -»• (r = 0.75,pcO.Ol ) •e- Cd -»• (r = 0.55,p<0.1) -e- Ni (r = 0.72,p<0.05) -e- Co. This group of elements accumulates mainly in fish inhabiting the Lower Volga. Accumulation in fish liver of H g-> (r= 0.61)<-Zn is observed in the Middle Volga, whereas accumulation of Mn-> (r = 0.59) <-Pb in fish gills and liver is typical of the Upper Volga. Bone tissues in the investigated fish demonstrated a high degree of correlation between the concentrations of the following elements: Pb ^ (r = 0.66, p < 0.025) -e- Hg (r = 0.79, p < 0.005) -e- Ni. Cd ->• (r = 0.79,p <0.005) -e- Cu (r = 0.87,p<0.0015) -e- Sr. 4- (r = 0.76,pcO.Ol) -e- Zn The correlations established between the concentrations of essential and non-essential microelements prove their joint penetration into the fish organism as a result of multimetal pollution. Based on the analysis of the element distributions in bream and the joint penetration of certain microelements into them, Sr-Cd-Al-Cr-Ni anthropogenic hydrogeoformation can be singled out in the Lower Volga; Hg-Zn hydrogeoformation in the Middle Volga; and Mn-Pb hydrogeoformation in the Upper Volga. s o Xt>10°C Et>10°C £t>10°C Fig. 2. Dependence of essential element concentrations in muscles (^g per 1g of dry weight) on the sum of temperature values exceeding +10 °C (X)£>10oC).