Taxonomic and Size–Morphological Groups of Bacterioplankton in Two Mongolian Reservoirs

The taxonomic and size-morphological structure of bacterioplankton has been studied in two large Mongolian reservoirs and the rivers on which they are built. Correlations between the taxonomic and size groups of bacteria and their main consumers, heterotrophic nanoflagellates, have been revealed. It has been shown that the protists consume large and active bacteria of classes Gammaproteobacteria and Bacteroidetes selectively, leaving small-sized Alphaproteobacteria and medium-sized Actinobacteria as dominants in the communities. The size–morphological structure of bacterioplankton formed by consumers is accompanied by spatial changes in the subdominants, probably performing similar functions in aquatic ecosystems.