Seasonal Variability of Bacterioplankton of the Yenisei Estuary

Materials collected in different seasons in the region of the Yenisei estuary, as well as previously published data, were used to analyze the scale and patterns of the seasonal variability of microbial communities. In all seasons concerned, three zones could be distinguished in the estuarine area based on the salinity values. The abundance and activity of bacterioplankton in these zones varied by an order of magnitude. In waters with salinities less than 2.5 PSU, the mean bacterial abundance values were 254 × 103, (2741 ± 394) × 103, and (2069 ± 185) × 103 cells/mL in spring, summer, and fall, respectively. At salinities greater than 18 PSU, the bacterial abundance in the same seasons was (196 ± 50) × 103, (683 ± 184) × 103, and (125 ± 24) × 103 cells/mL, respectively. Similar patterns were observed in the biomass distribution. Production and activity characteristics were unstable, with maximum values observed in the summer period. Within the zones identified by salinity indices, the distribution of bacterial abundance was apparently associated with small-scale patchiness in the distribution of organic matter, phytoplankton, and SPM. The contribution of the heterotrophic component of the microbial community was dominant in early spring. Despite the observed correlations between bacterial abundance and activity, phytoplankton, and organic carbon, their distribution patterns differed along the salinity gradient.