Ecology of Estuarine Basins of Southern Baikal Small Rivers According to Springtime Chemical and Microbiological Investigation

In March 2018, we analyzed water, ice, and snow cover in the estuaries and estuarine basins of the rivers of the southeastern and southwestern parts of Lake Baikal, as well as in two reference stations in the lake pelagic zone. The parameters determined in melted ice cores and estuarine waters were chemical composition, total microbial counts (TMC), dark CO2 assimilation (DCA) as well as the overall abundance of organotrophs and bacteria of sanitary importance. Our results indicated ice acidification in the basins of the Rivers Pereemnaya, Krestovka, and Bolshaya Cheremshanaya due to the effect of atmospheric precipitation enriched with the exhaust of nearby coal power plants and the river bottom. These processes had no negative effects on TMC, the abundance of organotrophic bacteria, and production characteristics. DCA measurements revealed the higher activity of ice microbial communities in the rivers and estuarine basins of the southeastern part of the lake (0.43 µg C L–1 day–1) compared to those of southwestern Baikal (0.26 µg C L–1 day–1). Microbiological parameters of the water samples exhibited a correlation with the levels of biogenic elements, total ions, and dissolved organic matter; a positive correlation was also observed between TMC and pH (r = 0.66). Low activity of microbial communities observed at high TMC at the estuaries of Lake Baikal rivers could result from the anthropogenic impact on microbial productive potential.