Bacterioplankton of the north-western stretch of Lake Munozero (the Republic of Karelia)

During the growing season of 2018, planktonic microbocenosis of the north-western stretch of Lake Munozero (the Republic of Karelia) was studied. The total abundance, biomass, production, doubling time, as well as the number of heterotrophic bacteria were determined. The bacterial total abundance ranged from 0.6 to 1.2 mn cells ml-1 and biomass ranged from 0.12 to 0.355 g/m3. Average cell volumes of the bacteria ranged between 0.18 and 0.33 μm3. The maximum values of the total abundance and average volume of bacterioplankton cells were observed in spring, and the biomass reached the maximum values in autumn. Bacterial production varied between 0.01 and 0.33 mn cells ml-1. Specific growth rates (day-1) ranged around 0.01–0.45 day-1, giving doubling times of 37–1872 h. Vertical distribution of parameters of the heterotrophic bacterioplankton in the studied part of the lake was irregular and depended on stratification. During the research period, the abundance of saprophytic bacteria in the water was in the range of 14–294 CFU/ml, and the abundance of oligotrophic bacteria ranged from 150 to 1450 CFU/ml. The north-western stretch of Lake Munozero can be characterized as transitional from oligotrophic to mesotrophic.