Impact of combined effects of Ikva river pollution on cytogenetic homeostasis of fish fauna representatives

For the first time the author has received the data regarding the impact of hydro-chemical parameters on the formation of fish cytogenetic homeostasis in the Ikva River within the territory of Rivne Oblast, particularly in the sites experiencing human impact of varying intensity. The research provides the results of the environmental assessment of the river surface water quality according to hydro-chemical parameters which have consistently indicated "good" condition (class II) throughout 2011-2015 with a marked contribution of the trophy-saprobic block and specific toxic substances block to the quality class formation. The conducted erythrocyte micronucleus test with fish peripheral blood showed exceeding levels of spontaneous mutations in such species as roaches (from 5.59 ± 0.49 ‰ to 6.19 ± 0.36 ‰), bleaks (from 3.79 ± 0.40 ‰ to 4.81 ± 0.61 ‰) and perch (from 3.04 ± 0.39 ‰ to 4.37 ± 0.41 ‰). The older age groups for all analysed fish species demonstrated higher levels of micronucleus infringements (nuclear damages), compared with the young of the year that proves the existence of the factors destabilizing cytogenetic homeostasis in the surface waters of the river. According to the results of the regression analysis of the relationship of surface water quality parameters in line with 16 hydro-chemical indicators and encounter frequency of micronuclei in fish erythrocytes, the author established that different ecological groups of fish have their own specific complex and multifactorial process of cytogenetic homeostasis formation. Nevertheless, combined effect of such metals as copper, zinc and manganese is most severe against the unfavourable oxygen regime of water environment. After the comparison of the achieved results, the author came to the conclusion that there is a need to introduce biomonitoring methods which unlike traditional assessment of hydro-chemical parameters allow the researcher to see the impact of the combined effects of hydro-ecosystem pollution.