The influence of viruses on bacterioplankton of the offshore and coastal parts of the Barents Sea

The viral and bacterioplankton communities of the Barents Sea were investigated using a combination of methods of electron and epifluorescence microscopy for the first time. The quantitative composition of the communities and the nature of their interactions were also determined. Our study showed that during the summer the abundance and biomass of bacterioplankton reached 0.4–4.0 × 10⁶ cells/mL and 25.09–84.21 mg/m³ in offshore waters and 0.4–1.8 × 10⁶ cells/mL and 19.63–100.19 mg/m³ in coastal waters, respectively. In both regions, the number of viruses (1.7–35.8 × 10⁶ and 14.5–32.4 × 10⁶ particles/mL) exceeded the number of bacteria by 2–31 and 13–60 times, respectively; the average viral production was 0.7510⁶ and 1.74 × 10⁶ particles/mL/day, respectively. The proportion of infected cells in the total bacterioplankton (7% on average) and virus-induced mortality of bacteria (8%) were much lower in offshore than in coastal waters (14 and 20%, respectively).