STRUCTURAL CHARACTERISTICS OF THE BIOLOGICAL COMMUNITIES OF ECOSYSTEMS OF THE LAKES WITH DIFFERENT DEGREES OF MINERALIZATION (REPUBLIC OF KHAKASSIA)
Lakes (Itkul', Matarak, Shunet, Vlas'evo, Bele) with varying degrees of salinity (from fresh to brackish), located in the steppe zone of the Republic of Khakassia were investigated. Reservoirs have fishery value, widely known among tourists and contain a large number of therapeutic muds. However, hydro-biological characteristics and ecological condition of the lakes is underinvestigated. Fieldwork was carried out in summer 2014 and are aimed at long-term monitoring of ecosystems of lakes. At this stage, material for bacterio-, phytoplankton and littoral zoobenthos was collected; temperature, pH, BOD<sub>5</sub>, the oxygen content, suspended mineral and dissolved organic matter, the concentration of chlorophyll «a» were measured in water. Selection and processing of samples was performed by standard methods. Despite belonging to a single geographical and climatic conditions, the ecosystem of lakes differed on some physico-chemical and biological indicators. Most salt lake Bele is characterized by minimum values of suspended mineral and dissolved organic matter, concentration of chlorophyll «a», BOD5 and density of phytoplankton and zoobenthos. With the growth of salinity depletion of the species composition of zoobenthos, increasing the share of blue-green algae in algocoenosis and amphipods in bentocenoses of the lakes were observed. The quality of water in all the lakes corresponded to the 3rd class «satisfactory purity». The trophic status of the most salty lake is assessed as oligotrophic, the rest belong to the class of mesotrophic in the transition to a eutrophic.