The quantitative growth and spatial dynamics of major ecotrophic groups of heterotrophic bacterioplankton in rivers Lososinka and Neglinka in Petrozavodsk(oligocarbophilic, saprophytic, phenol-resistant, hydrocarbon oxidizing, and total coliform) are shown. The effect of the hydrometeorological factor on the investigated groups of bacterioplankton was considered. Water pollution by labile organic matter, including fecal organic matter and oil products was indicated by the level of development of indicator groups of heterotrophic bacteria. The river water was classified into the β-, α-mesosaprobic class with signs of pollution and eutrophication in the studied period. The abundance of potentially pathogenic microorganisms in the water of these urban rivers excluded the possibility of their recreational use. The bioassay showed that water in the urban rivers had no toxic effect on standard test objects – the crustacean Ceriodaphnia affinis.