Viruses and viral infection of heterotrophic prokaryotes in shelf waters of the western part of the East Siberian Sea

Abstract

In September 2017, studies were conducted in the East Siberian Sea along the transect from a Indigirka delta to the ice edge at the outer shelf margin. The abundances of planktonic prokaryotes (NPR) and free viruses (NV), frequency of visibly infected prokaryotic cells (FVIC), and virus-mediated mortality of prokaryotes (VMPR) varied within (0.5–3.4) × 106 (on average (1.67 ± 0.69) × 106) cells/mL; (2.3–10.3) × 106 (on average (5.28 ± 1.91) × 106) viruses/mL; 0.6–2.5 (on average 1.1 ± 0.4) % of NPR; and 4.5–22.3 (on average 9.0 ± 3.8) % of the total prokaryotic production, respectively. The proportions of viruses attached to prokaryotic cells (NVPR) and suspended particles (NVP) were 1.9–26.3 (on average 8.0 ± 5.0) % of NV and 0.1–65.9 (on average 8.0 ± 13.3) % of NV, respectively. High concentrations of detrital and mineral particles, to which a significant number of viruses were attached and, as a result, loss of their activity were recorded in the river–sea water mixing zone. In such a situation, the number of virus attacks on prokaryotes and cases of their infection decreased. There was a negative relationship between the concentration of suspended particles 0.5–5.0 μm in size and the abundance of infected prokaryotic cells. Thus, we conclude that viruses played a substantial role in controlling the abundance and production of heterotrophic prokaryotic plankton in the low-productive East Siberian Sea at the beginning of autumn. Regional index terms: Russian Federation; East Siberian Sea. Geographic bounding coordinates: 70–78° N; 150–165° E.