[Seasonal trends in transformation of organic matter forms and enzyme activities in aquatic environment in winter in the Russian Arctic seas by the example of Yenisey Estuary].

Time variations in the main hydrochemical indices of water, organic matter forms, and hydrolytic enzyme activities in aquatic environment have been studied in winter in the southeastern Kara Sea (Yenisey Estuary with depths from 29 to 31 m). The abundance of some components of microproducer (pico-, nano-, and microphytoplankton) and bacterial plankton communities has been analyzed. High functional activity of microcommunities has been demonstrated in winter hydrobiological period. The hydrological, hydrochemical, biochemical, and biological indices of aquatic environment considerably varied in time while their stratification remained stable. The total resources of biologically accessible dissolved organic matter was evaluated by splitting the biological oxygen demand curves obtained under standard conditions (at 22 degrees C).