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) 837-850 841 Thus, both organic and inorganic pollutants, for which the Toxicological Harmfulness Value has been established, are found in the Volga River water. 4. Metals in fish as a reflection of water pollution The concentrations of metals in fish can reflect levels of pollution more accurately than the indices of contaminant content in water (Moore and Rammamoorthty, 1983; Spry and Wiener, 1991; Moiseenko and Kudryavtseva, 2002). A group of non-essential elements (Hg, Cd, and Pb) is most dangerous for living organisms. The concentrations of these metals in the environment is increasing steadily (Dirilgen and Dogan, 2002; Friedmann et al., 2002; Gochfeld, 2003; Moiseenko et al., 2006a, b). 4.2. Mercury The concentration of Hg in bream organs and tissues varied from less than 0.001 to 0.127 j.ig/g dry weight (Table 3). This metal accumulates most intensely in the liver, kidneys, and muscles, as confirmed by data presented in the scientific literature (Moore and Rammamoorthty, 1983; Friedmann et al., 2002; Gochfeld, 2003). The highest concentrations of Hg were revealed in bream caught in several sections of the Middle Volga, which is subject to the heaviest anthropogenic load. Comparison of the data obtained by the authors with those from other scientific papers showed that the limits within which the concentration of Hg in bream muscles and liver can vary are comparable with those determined for Lake Balaton (Farkas et al., 2003) and certain water bodies in the Czech Republic (Svobodova et al., 1999). Similar values were cited for certain freshwater and sea fish inhabiting water bodies of the USA (Watras et al., 1998). 4.2. Cadmium The literature cites a high degree of Cd accumulation in living organisms, which is indicative of environmental pollution on local and regional scales (Conto-Cinier et al., 1997). The most intense accumulation of Cd in all the physiological systems of fish was observed for those inhabiting the Lower Volga (Table 3). The accumulation of Cd in fish muscles testifies to long-term pollution of the body of water with this metal (McGeer et al., 2000). The maximum Cd concentration (up to 5.66 (-ig/g dry weight) was recorded in the kidney. Unfortunately, there are few studies devoted to the analysis of accumulation of this metal in fish kidneys. The concentration of Cd in fish kidneys closely correlates with its concentration in other systems of the fish organism, such as the liver (r = 0.78, p < 0.005), skeleton (r = 0.71, p<0.01), and gills (r = 0.56, p < 0.1), which demonstrates penetration of Cd into the fish from contaminated water. 4.3. Lead The maximum concentration of Pb in bream was observed in the Upper and Middle Volga (Table 3). Pb is most intensely accumulated by the kidneys, liver, and muscle (the respective concentrations were up to 1.3, 0.75, and 0.18 j.ig/g dry weight). It is difficult to explain why, under conditions of a higher concentra­ tion of Pb in the Lower Volga water, the maximum accumulation of this element was observed in fish inhabiting the Upper and Middle Volga. This is probably a manifestation of the cumulative effect of river contamination in previous years. In Lake Balaton, the concentration of Pb in bream muscles was higher: 1.6 j.ig/g dry weight (Farkas et al., 2003). 4.4. Aluminum According to data from Rosseland et al. (1990), a high concentration of Al in the environment (both in dissolved and suspended forms) ensures its intense accumulation in fish (espe­ cially in the gills). The maximum concentration of Al in the water and in organs and tissues of bream was observed in the Lower Volga (Tables 1 and 3). Accumulation of Al could be traced in all the body systems of fish, but the highest concentrations of this metal were observed in the gills and skeleton. Bioaccumulation of Al in these organs is demonstrated by the following regression equations: Algius = 0.072 Alwater + 22.4, r = 0.90, p < 0.001, ^ s k e l e to n —0.007 Alwater + 7.19, Г = 0.74, p<0.01. The close dependence of Al in fish gills on Al in water can be explained by the fact that, in the process of breathing, water is filtered through the gills of the fish, and Al settles onto the gill surface. Coagulation of Al on the surface of the gill epithelium, in addition to its inclusion in epithelial cells, has been demonstrated (Rosseland et al„ 1990). 4.5. Strontium This element participates in metabolic processes with Ca. Being more labile and active, Sr gradually disturbs the normal calcification of the skeleton and causes pathological disturbances in bone tissue (Chowdhuury et al., 2000). The highest concentration of Sr in bream inhabiting the Volga basin was found in the Lower Volga sections, where the concentration of Sr in the water was maximal (Table 3), reaching 1500 (.ig/g dry weight in fish skeleton and 1100 (-ig/g dry weight in the gills. Sr accumulates not only in fish bones but also in fish muscles, liver, and kidneys. The dependence of the Sr content of bream organs and tissues on its concentration in water can be approximated by the following equations: Srgiiis = 1.52 Srwater - 25.0, r = 0.99, pcO.OOl, SrmUscies = 0.026 Srwater + 2.98, r = 0.74, pcO.Ol, Srliver = 0.003 Srwater + 0.191, r = 0.79, p<0.005, Slkidneys = 0.006 S rwater + 0.672, r = 0.95, p < 0.001, Skeleton = 1-94 Srwater - 73.6, r = 0.98, p < 0.001. It should be emphasized that the Sr/Ca ratio in water varied along the river course; it was 1/289 in the Upper Volga, 1/186 in the Middle Volga, and 1/66 in the Lower Volga water. In addition to the increase in the absolute value of Sr concentration in the water from the Upper to the Lower Volga, its relative concentration in fish organisms increased even more, which testifies to the replacement of Ca by Sr in bream bones. For example, the Sr/Ca ratio in bream gills was 1/516 in the Upper; 1/266 in the Middle; and 1/83 in the Lower Volga. The respective values for bream skeleton were 1/798, 1/384, and 1/116. Thus, Sr features a high bioaccumulation capacity. 4.6. Nickel The concentration of this metal in the muscles and liver of bream inhabiting the Volga River did not exceed 0.60|jg/g dry weight; for kidneys, the value was somewhat higher (Table 3). Ni accumulates intensely in fish, mainly in the gills and kidneys