Ecosystem and human health assessment to define environmental management strategies: the case of long-term human impacts on an Arctic lake / Moiseenko T. I., Gashkina N. A., Voinov A. A. [et al.] // The Science of the Total Environment. - 2006. - Т. 369, № 1-3. - С. 1-20.

TI. Moiseenko et al. /Science o f the Total Environment 369 (2006) 1-20 11 contaminant-induced stress. Many organism groups can be used as indicators of environmental and ecological change (Cash, 1995; Whitfield and Elliott, 2002) . Numerous publications attest that fish (in situ) is a good indicator of environmental change and ecosystem health, especially in case of toxic water pollution (Adam and Ryon, 1994; Wong and Dixon, 1995; Simon, 2000) . Fish occupy the upper level in the trophic system of aquatic ecosystems. Pathologic changes in fish organ­ isms allow the determination of the degree of the aquatic environment toxicity and give an idea of the potential hazard presented by different substances finding their way to this water body, as well as of the cumulative effect of the substances in question on organisms during their lifetime. It is very important to reveal unfavorable water quality, based on studying fish organisms, because many physiological systems of fishes are similar to those of hematothermal animals, which allows us to predict the consequences of toxic substances occurrence in the aquatic environment for human organism as well. Our results show that water quality and conditions for water inhabitants have worsened in the period of intense pollution and they did not recover with decreasing inflows of contaminants. The main question for environmental management is to which level must pollution loads be decreased to achieve reference conditions and to preserve ecosystem health? To answer this question, we need to accomplish three tasks: 1. Assign criteria of estimation of ecosystem health, which could reflect effects o f impact more informatively; 2. Determinate the method of hydro-chemical informa­ tion compression to a unified parameter of water quality, which could reflect real impacts of the dose taking into account contaminant complexes (multi­ pollution); 3. Determine critical levels of water pollution and required level of its reduction based on this dose- effect relationship. Below is how we addressed these problems for Lake Imandra. Criteria o f fish condition assessment. Table 4 documents data about fish morbidity in different periods of Lake Imandra pollution. During the period of intensive stress the situation was quite dramatic and gave a clear signal about a need to decrease the toxic pollution. Diagnostics of fish health requires system studies, which combine extensive data with making exact diagnoses. A diagnostic system for fish state, suitable for practical monitoring, is presented elsewhere (Moi- seenko, 1999, 2005) . The macro-level examination of individuals involves diagnosing of diseases on the basis of a visual examination of numerous organisms. At this level, a preliminary diagnosis is made based on clinical and postmortem symptoms of intoxication. The micro­ level diagnostics include hemathologic, histologic, biochemical, instrumental, and other methods. These are labor-intensive and cannot be used widely used, however they are essential to refine the diagnosis and estimate the consequences of pathologic changes in fish organisms. The determination of the degree of disturbance in an individual organism is very important to diagnose the damage to fish organisms in the contaminated zone. For instance, up to 70% of individuals in the zones of contamination may be in the state close to the lethal threshold. If the concentration of toxic substances is not high, the percentage of affected individuals can be the same, but disturbances in fish organisms can be inconsiderable and will not be life threatening. In order to estimate the state of fish organism using the data of clinical and postmortem examination, experts suggest using different rating point systems. In the process of macro-diagnostics, three stages of the disease can be singled out (0 denotes healthy individuals): (1) Low disturbances, not threatening the life of the fish; (2) Medium-level disturbances, causing a critical state of the organism; (3) Distinct intoxication symptoms leading to inevi­ table death of the organism. The overall index of morbidity in fish in the given zone of contamination can be presented as: Z = (N 1 + 2 N 2 + 3N,)/Ntot. Here Z is the morbidity index for fish, O < Z < 3; N1, N 2, and N 3 are the number of fishes in the first, second, and third stages of the disease, respectively; N tot is the total number of the examined fishes in the local contamination zone, including healthy individuals. If all the fishes in the given water body do not demonstrate any intoxication symptoms, then Z =0. The value of Z will increase with an increase in both the number of sick fishes and the severeness of their diseases. Histopathological analyses of liver, kidney and gills alteration are used for the final diagnosis. Histological analysis of diseased liver of whitefish of Lake Imandra shows lipoid degeneration of liver cells, signs of necrosis and atrophy caused by the destruction of liver