Role of Microorganisms and Viruses in the Vertical Flux in the East Siberian and Laptev Seas

Abstract— The contribution of bacteria (BAC), heterotrophic nanoflagellates (HNF), and viruses (VIR) to vertical matter fluxes on the shelves of the East Siberian Sea (ESS) and Laptev Sea (LS) was studied using sediment traps deployed at buoy stations at depths of 18–55 m for 4–19 days. The value of the total organic carbon flux (TOC) contained in the cells of bacteria (BAC), heterotrophic nanoflagellates (HNF), and virus particles (VIR) in the ESS varied from 0.5 to 2.4 mgC m⁻² day⁻¹ and was 1.1–4.9% of the total TOC flux; in the LS, it varied from 0.7 to 5.2 mgC m⁻² day⁻¹ and was 1.1–6.2% of the total TOC flux. The maximum flux values were measured near the Lena River delta and the mouths of the Khatanga and Indigirka rivers. The contribution of BAC, GNF, and VIR to the total biomass of the microbial community attached to sinking particles was, on average, 59 ± 11%, and 28 ± 8%, 13 ± 9% for ESS and LS, respectively.