RETROSPECTIVE ASSESSMENT OF CHANGES IN THE STATE OF SEDIMENTS OF LAKE ONEGA UNDER THE INFLUENCE OF ANTHROPOGENIC FACTORS

Lake Onega is unique, coldwater, one of the largest lakes in Europe (S=9720 km², V=292 km³). The study is based on comparative analysis of original sedimentary chemistry data for the period of 1964-2010. The distribution of sediments in the lake area, they chemical composition and elements of biota, to a great extent, depend on the limnology heterogeneity. The irregular territorial distribution of the anthropogenic loads on the shores of the lake enlarges the heterogeneity, what is immediately reflected on the sediments. As direct results of anthropogenic effect on ecosystem of Lake Onega is the appearance of bottom zones, where the sediments have changed physically, chemically, biologically in polluted regions. The results of sediments state longtime researchers demonstrate great changes in chemical parameters of sediments in Kondopoga and Petrozavodsk bays. The main tendency, marked during the 1960-2000 years sediments researches was a constant extending of the polluted bottom area these bays. The distribution, the composition and the properties those sediments are good indicators of anthropogenic impact, and they can serve as a sign of degree of that influence on lake ecosystem. At present, the main direction of the ecosystem of Lake Onega is stabilizing after a period of intensive anthropogenic eutrophication in the early nineties.

The study was supported by the grant of the Russian science Foundation № 14-17-00766.