Bacterioplankton Status in the Lososinka River (Tributary of Lake Onego) and the Water Quality by Microbiological Indicators

Abstract—The results of a bacterioplankton study (total abundance; saprophytic, hydrocarbon oxidizing, and phenol resistant bacteria; total microbial count; and coliform bacteria) in an urbanized tributary of Lake Onego in 2015 are presented. The lower reaches of the Lososinka River flow over the territory of the city of Petrozavodsk (Karelia) and receive 14 untreated storm runoff streams from the municipal storm sewers. Differences in the temporal abundance dynamics of bacteria, which are indicators of oil pollution, the sanitary condition, and saprobity, were found between the reference and urban parts of the river. These variations are not related to the hydrological and thermal regime of the river and reflect the impact of the pollutant discharge from the urban area on the formation of the bacterial community of the river. The study revealed a significant increase in all the studied indicators of the quantitative development of bacterioplankton in the urban part of the river as compared to the reference part. The number of heterotrophic bacteria of various ecological–trophic groups decreases in the lake water by a factor of 8–16 already at a distance of 500 m from the mouth of the river due to dilution. A significant decrease in the numbers of hydrocarbon oxidizing bacteria in the river water and an increase in sanitary-indicative microorganisms are shown to have occurred over four years. Within the city limits of Petrozavodsk, the Lososinka River has been assessed as polluted with petroleum products, as well as organic substances of fecal origin and unfit for recreation based on the level of the indicator bacteria.