Communities of the bacterioplankton in South Baikal and Irkutsk reservoirs during the open water period of 2023

Reservoir ecosystems are different from river ecosystems, as a result of which they are regulated, and undergo natural changes over time. An important component of freshwater ecosystems, both in terms of taxonomic diversity and abundance, are unicellular eukaryotes (microeukaryotes). Microeukaryotes include various groups of phytoplankton (the main primary producers), protozoa (consumers of phytoplankton and bacteria), and fungi (parasites of microeukaryotes). A marker of the ecological state of freshwater ecosystems is the species composition and abundance of phytoplankton, indicator species are among diatoms, chrysophytes are sensitive to environmental changes. Different taxa of microeukaryotes in the aquatic environment form communities, which also include bacteria. The structure and dynamics of microbial communities as a whole is determined by the life cycles of individual species, interspecies interactions, local and seasonal physicochemical factors, and regional conditions. Basically, the assessment of the ecological state of water bodies is limited to the results of phytoplankton studies using light microscopy, which does not give a complete picture of the ecosystem. Electron microscopy makes it possible to more accurately identify diatom species and makes a wide range of other silicon-dependent microeukaryotes available for analysis. In the last couple of decades, high-throughput sequencing (HTS) methods have been actively introduced into the practice of analyzing taxonomic diversity and the structure of microbial communities. Analysis of the composition of communities using the HTS of total DNA isolated from natural samples reveals a significantly higher taxonomic diversity than traditional microscopy methods, which gives a more complete picture of the ecological state of the studied water body, and analysis of samples taken at certain intervals makes it possible to observe the dynamics of communities.