Microorganisms Contributing to the Biological Pump in the Western Arctic Ocean During Late Summer

Marine particles can be classified into sinking and suspended particles, and recent studies have revealed that the microbial communities associated with each particle are distinct. The western Arctic Ocean has undergone significant environmental changes due to sea ice loss in recent years, which may impact the biological pump. While microbial communities on suspended particles in this region have been studied, those on sinking particles remain largely unexplored. We analyzed the eukaryotic and prokaryotic community structures of suspended and sinking particles collected from subsurface chlorophyll maximum layers in the western Arctic Ocean during late summer 2021 using a marine snow catcher. A significant difference between the two particle types in overall eukaryotic community structures was observed, while differences in prokaryotic communities were evident at more specific taxonomic levels. Carbon sinking flux ranged from 68.7 to 774 mg C m⁻² d⁻¹ and showed a significant positive correlation with chlorophyll a concentrations. Correlation network analysis identified microbial modules, including diatoms, parasites in Syndiniales and Peronosporomycetes as well as Desulfobacterota, which positively correlated with carbon sinking flux. Our findings highlight previously unrecognized microbial contributors to the biological pump in the western Arctic Ocean, and these organisms maybe key to elucidating biogeochemical cycles in the changing Arctic Ocean.