Influence of hydrological regime changes on the state of biological communities of a lake in condition of eutrophication

According to the data of two years observations over an ecosystem of the mezotrophyc lake Krasnoe (Karelian Isthmus), typical for the Northwest of Russia influence of hydrological factors, first of all water level, and eutrophication on structure and abundance of the main biological communities has been estimated. Different reaction of planktonic and littoral communities to changes of water level and temperature is shown. Quantitative indices of planktonic communities were higher in warm 2016 abounding in water, but the level of development of littoral communities and their diversity were much lower. Expansion of an alien species of Potamogeton as a result of level fall, as well as intensive water bloom testify to the violation of ecosystem stability of the lake in the conditions of the proceeding eutrophication.