Changes of macrozoobenthos communities in the gradient of salinity in the rivers of the basin hypersaline lake Elton (2006-2013)

The highly mineralized rivers that flow into the hypergaline Lake El'ton represent a hydroecosystem of the unique natural and territorial complex of Priel'ton, which belongs to the inland reservoir of the Caspian Basin. At the salinity gradient of 4 to 41 g/l. bottom communities of mesohaline and polygaline rivers are characterized by interannual, spatial and seasonal dynamics of taxonomic, structural and quantitative indicators. There were identified 91 species and a macrozoobenthos taxon, which belong to 5 large systematic groups (Oligochaeta, Malacostraca, Branchiopoda, Insecta, Arachnida). According to the species richness, insects predominate - 68 species and taxa. Larvae of Diptera are represented by 41 taxa, 25 of which are species of the Chironomidae family. The formation of fauna of bottom communities is carried out by eurybiont halotolerant species having a different range of salinity resistance. In the 5 studied eutrophic, highly mineralized saline rivers, the following chironomidae predominate in different years: Cricotopus salinophilus, Chironomus salinarius, Chironomus aprilinus, Tanytarsus kharaensis, Microchironomus deribae, Glyptotendipes salinus (Diptera: Chironomidae), Culicoides (M.) riethi, Palpomyia schmidti (Diptera: Ceratopogonidae), Paranais simplex (Oligochaeta) and Ephydra sp. (Ephydridae). Saline rivers represent a complexly organized system in which the variability of macrozoobenthos communities is associated with habitat factors. The taxonomic composition and biodiversity of the macrozoobenthos closely correlate with water mineralization and other hydrochemical characteristic; the number and distribution of species in different years depend on a complex of hydrological and hydrophysical factors (depth, overgrowth, water temperature, pH, etc.).