EN: Przemysław Nowacki, Jarosław Kobak: Impact of several artificial diets on the attachment strength of adult zebra mussels (Dreissena polymorpha); Tomasz Kakareko, Janusz Żbikowski: A tentative assesment of the influence of common bream Abramis brama (L.) on the prey populations and water chemistry in the Włocławek Reservoir in the Lower Vistula; Joanna Kowalska, Marta Luścińska: Phytoplankton of Lake Raduń; Maria Swiontek Brzezińska, Wojciech Donderski: Participation of planktonic and benthic bacteria in degradation of chitin; Aleksandra Burkowska, Wojciech Donderski: Influence of pH on the development of heterotrophic bacteria in presence of humic substances; Maciej Walczak, Wojciech Donderski: Effect of treatment plant operation on microbiological pollutions of rivers water; Marta Małecka, Iwona Wilk, Wojciech Donderski: The bacteria of the nitrogen cycle in the water of the river Brda within the town of Bydgoszc