Production of Heterotrophic Bacterioplankton in a Large Meso-Eutrophic Reservoir: The Importance of Extracellular Organic Carbon Released by Phytoplankton

The spatial distribution and seasonal dynamics of heterotrophic bacterioplankton production have been studied and the value of autochthonous sources of substrates for bacteria has been evaluated in the pelagic zone of the meso-eutrophic Rybinsk Reservoir (the Upper Volga). During the vegetation period, the bacterial production ranges from 32 to 1352 (on average 444 ± 44) mg C/(m² × day). The total input of organic carbon from the processes of extracellular production of phytoplankton, viral lysis of prokaryotic cells, and feeding of protists provides 9–64% (32 ± 3% on average) of the daily carbon demand for heterotrophic bacterioplankton.