Seasonal Variability in the Sedimentary Matter Flux on the Shelf of the Northern Kara Sea

Sedimentation rates in the northern Kara Sea between September 2019 and July 2020 were calculated from integrated monthly values for sedimentary matter, organic carbon, nitrogen, total silica, aluminum, fecal pellets, and phytoplankton using a multicup sediment trap moored at a depth of 110 m. The seasonal dynamics of the total flux and its components was characterized by three pronounced maxima, observed not only in the ice-free season in September, but also under ice in February and April. The flux of total matter and particulate organic carbon (POC) during these periods was 400–600 mg m–2 day–1 and 8–14 mgC m–2 d–1, respectively. The increase in the flux in winter and early spring was most likely due to the formation of polynyas. The contribution of the biogenic POC flux was 30% of the total POC flux in the winter months, 50% in the autumn, and up to 80% in May–June. The maximum flux of fecal pellets and larvacean “houses” (0.2 mgC m–2 d–1) was observed in autumn and did not exceed 0.02 mgC m–2 d–1 the rest of the year. The phytoplankton flux was about 0.05 mgC m–2 d–1 in autumn, and it decreased to <0.01 mgC m–2 d–1 in winter. An increase in the phytoplankton flux in May–June to its maximum values (0.2 mgC m–2 d–1) indicated the development of plankton algae long before ice melting. The calculated annual flux for total matter and POC (75 g m–2 yr–1 and 2 gC m–2 yr–1) was significantly lower than the published values for the Kara Sea shelf influenced by river runoff.