Viruses in bottom sediments of a Mesotrophic Reservoir (Rybinsk Reservoir, Upper Volga)

The total number and morphological and size composition of viriobenthos, number of bacteria infected by viruses, and burst size, as well as virus-induced mortality, abundance, and production of bacteriobenthos, have been estimated in bottom sediments of the Rybinsk Reservoir. The total number of viriobenthos in the reservoir varies within (1.1–10.9) × 109 (on average, (5.9 ± 0.6) × 109) particles/cm3; the total number of virus-to-bacteria ratio ranges within 0.2–2.1 (on average 0.9 ± 0.3). A weak positive correlation is found between the abundance of benthic viruses and the abundance and production of benthic bacteria. In most surveyed parts of the reservoir, infected benthic bacteria were not found or the portion of visibly infected bacterial cells (FVIC) did not exceed 0.5% of the total abundance of bacteriobenthos (NB). A comparatively high infection of bacteria by viruses was recorded in bottom sediments only at one deep-water station, where FVIC was 2.5 of NB.