Trophic relationships between planktonic bacteria, heterotrophic nanoflagellates and viruses in a mesoeutrophic reservoir

Abstract

The abundance, biomass, and production (РВ) of bacrerioplankton; the taxonomic composition, abundance, biomass of heterotrophic nanoflagellates (HNF) and the rate of consumption of bacteria by HNFs; and the abundance of virioplankton, frequency of visibly infected bacterial cells, virus-induced mortality of bacterioplankton, and viral production were estimated in the mesoeutrophic Rybinsk Reservoir. The rate of bacterial mortality due to viral lysis (7.8–34.1%, on average 17.2 ± 2.0% of daily РВ) was lower than the consumption of bacteria by the HNF community (15.4–61.3%, on average 32.0 ± 4.2% of daily РВ). While consuming bacteria, HNFs simultaneously absorbed a significant number of viruses residing on the surface and inside the bacterial cells.