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.

846 T.I. Moiseenko et al. / Ecotoxicology and Environmental Safety 71 (2008) 837-850 Fig. 5. Pathological changes in kidneys of bream (arrowed), x320: a—normal structure; b—necrosis of the hematopoietic tissue; с—proliferative inflammation with fibrosis of the hematopoietic tissue; d—lipoid degeneration; e—interstitial inflammation; and f—hemorrhage. functioning tissue and preventing the proliferation of pathology; and the occurrence of interstitial substances in the kidney parenchyma (Fig. 5b), causing compression of healthy tissue, which, in the long run, can lead to the organ atrophy. 5.4. Gonads At the time of the examination, gonads were at stages II—III of development. In some cases, their form and texture were abnormal. Their growth was uneven. Some parts of gonads were replaced by non-functional connective tissue. Twisting of the gonads was typical, mostly in males. In females, uneven develop­ ment of fish eggs was observed. 5.5. Hematology Pathology developed simultaneously with disturbances in vitally important organs of the fish. The “ norm” of hematological indices is different for each fish species. According to the data presented by Zhiteneva et al. (1989), the concentration of hemoglobin in the blood of healthy bream varies from 92.0 to 101.0g/1. A 15-30% decrease in hemoglobin concentration is a signal of fish disease, which can be caused by both invasive and toxic agents. For bream inhabiting the Volga River basin, a value of 90 g/1 is adopted as the lower boundary o f the “ norm” of natural variability in hemoglobin concentration. The largest number of fish whose hemoglobin concentration was lower than the norm, was caught in a certain site of the Lower Volga and in the Gorkii Reservoir. Toxic substances affect not only hemoglobin concentration but also change the leukogram and red blood cell composition (Ivanova, 1976a, b; Zhiteneva et al., 1989). Studies have shown that, in different sites of the Volga River, the ratio between different forms of blood cells of bream changes. The highest percentage of immature forms of erythrocytes was found in blood smears of fish caught in the Lower Volga, which is in agreement with the low hemoglobin concentration in the blood. Changes in the leukogram of the bream manifested themselves in an increase in the relative amount of neutrophils and monocytes, especially in fish from certain sections of the Lower Volga and the Gorkii Reservoir (Table 4). In the blood smears, different pathological forms of erythrocytes (lacy erythrocytes, poikilocythemia, vacuo­ lization of the cytoplasm, pycnosis of the cell nuclei, amitosis of the cell nuclei, etc.) were found. The changes revealed in hematological parameters of the examined fish confirm the development of toxicoses in fish inhabiting the Volga River basin. Thus, fishes caught in the Volga basin had visible clinic and postmortem symptoms of intoxication. The degree of distur­ bances in their organs varied from hardly visible to pronounced deep degenerative changes, increasing the risk of death of the individual. 6. Discussion and conclusion Our results show that water quality and living conditions for aquatic species in the Volga River are unsatisfactory. Based on the prevalence of signs of intoxication in test-organism fish (A. brama (L.), we can conclude that the ecosystem health conditions are quite dramatic and give a clear signal of the need to decrease toxic pollution. The main question for environmental management is the level to which pollution loading must be reduced to achieve reference conditions and to preserve ecosystem health. To answer this question, we need to accomplish three tasks (Moiseenko et al., 2006a, b): 1. Determinate how hydro-chemical information on water qual­ ity can be interpreted in terms of a unified parameter, which could reflect the real impacts of the dose taking into account contaminant complexes (multipollution). 2. Assign criteria for ecosystem health that informatively reflect the impacts of pollution. 3. Determine critical levels of water pollution and required load reductions based on a dose-effect relationship.