Вириопланктон и вирусная инфекция бактерий северо-восточной части Карского моря в районе архипелага Северная Земля (Арктика)

Abstract

The study of the virioplankton structure and virus-induced mortality of bacteria in the northeastern Kara Sea was carried out during the cruise of the R/V Professor Molchanov within the framework of the Arctic Archipelagoes-2019 program. The material was obtained from August 22 to September 7, 2019 in the area of the Severnaya Zemlya archipelago, the middle shelf section between Vize Island and Ushakov Island and in the outer shelf continental slope section. In the studied waters, the number of bacteria (N_B) and the number of free viruses (N_VF) fluctuated within the range of (0.24–5.15) × 10⁵ cells ml⁻¹ and (15.41–64.72) × 10⁵ viruses ml⁻¹, respectively. The N_B/N_VF ratio varied from 6.9 to 89.7, averaging 14.6±6.2 in the coastal waters of the Severnaya Zemlya archipelago and 56.9±23.3 in the open waters of the shelf and continental slope. A strong positive correlation was observed between N_VF and N_B (R = 0.72, n = 23, p <0.05). In all studied waters, tailless viruses predominated among free viruses. In the waters adjacent to the Severnaya Zemlya archipelago, the average diameter of virus capsids (42±5 nm) was lower than that in open waters (50±5 nm). In addition to free viruses, virioplankton contained viruses attached to bacterial cells and to the smallest suspended particles. Free viruses predominated in all water samples, but their share in the total virioplankton abundance in coastal waters (86.4±9.3%) was lower than that in open waters (94.3±5.0%). The frequency of visible virus-infected bacterial cells (FVIC), i.e. the share of cells containing mature phages in the total bacterial abundance, varied from 0.8% N_B to 3.9% N_B, averaging 1.6±0.7% N_B for all samples studied. A strong positive correlation was found between FVIC and bacterial production (R = 0.69, n = 23, p <0.05). Bacterial mortality due to viral lysis ranged from 6.1–39.2% of bacterial production, averaging 13.8±7.9% of bacterial production for the studied area of the Kara Sea. The study showed that in the coastal and open waters of the north-eastern Kara Sea, in autumn, viruses are an important component of the planktonic microbial community, and viral lysis significantly affects the mortality of planktonic bacteria.

Keywords: virioplankton, viral infection, virus-induced mortality of bacteria, bacterioplankton, Kara Sea, Arctic