EN
The report presents the results of a study of phytoplankton primary and bacterial secondary production and enzymatic activities in surface lake water sampled from five lakes (Mazurian Lake District, Poland) of different degrees of eutrophication during summer stratification period.The rates of bacterial processes related to the tropic status of the lakes.The magnitude of bacterial production was strongly depended on bacterial enzymatic degradation of polymeric organic matter.Through the production of hydrolitic enzymes bacteria were capable of utilizing a variety of polymeric substrates, otherwise not utilizable, which predominated in lake water.The autors also propose and discuss a model of flow of organic matter in aquatic ecosystems and a role of bacteria and phages in this process.