Структура летнего фитопланктона реки Олёкмы (Восточная Сибирь) и среда его обитания

The first results of the study of phytoplankton and chemical composition of water of the middle and lower Olyokma River (Eastern Siberia, Lena River basin) were reported. The study revealed spatial structure of phytoplankton communities of river sections with various hydrologic conditions. The available information on the species diversity of the river was significantly replenished. Main factors that limit phytoplankton density and biomass were found. Formation of chemical composition and physical parameters of waters of the river Olyokma occurs under the influence of natural factors connected, mainly, with the influence of permanently frozen soils. Water quality was estimated from phytoplanktic bioindicators and water chemical characteristics.