STRUCTURE OF THE AUTOTROPHIC COMPONENT OF THE BIOLOGICAL CARBON PUMP IN THE WESTERN PERIPHERY OF THE CENTRAL ARCTIC BASIN IN THE SUMMER OF 2021

In the summer of 2021, during the 84th cruise of the R/V “Akademik Mstislav Keldysh”, unique data on the structure of the biological carbon pump in the near-surface ice zone and in the open water of the deep Arctic Ocean (Fram Strait and the southern Nansen Basin up to 82° N) were obtained. The interaction of cold Arctic and warm Atlantic water masses near the drifting ice edge forms a vertical thermohaline structure that determines the species composition and quantitative indicators of phytoplankton. A characteristic feature of the phytoplankton structure was the dominance of large diatom algae Rhizosolenia hebetata f. hebetata and Rhizosolenia styliformis rather than small celled species of spring bloom. It is shown for the first time that in the late summer period at most stations of the studied area the mixoplankton trophic strategy prevails in the formation of phytoplankton biomass. The main role in the transfer of organic matter from small forms (bacteria and phytoplankton) to large forms was played by the dinoflagellates Gyrodinium lachryma and the infusoria Mesodinium rubrum confined to the upper water layers (0–10 m). Large autotrophic diatoms, whose biomass correlated with nitrogen concentration (r = 0.44), accumulated near the lower boundary of the euphotic zone. As a consequence, the biological carbon pump in the western periphery of the Central Arctic Basin is vertically differentiated: in the upper layers it is a system with a high degree of organic matter transformation, while in the lower layers it is a system with high organic matter export.

biological carbon pump, phytoplankton, diatoms, dinoflagellates, mixoplankton trophic strategy, Arctic basin