Sea ice presence is linked to higher carbon export and vertical microbial connectivity in the Eurasian Arctic Ocean
Eduard Fadeev, Andreas Rogge, Simon Ramondenc, Eva‐Maria Nöthig, Claudia Wekerle, Christina Bienhold, Ian Salter, Anya M. Waite, Laura Hehemann, Antje Boëtius, Morten Hvitfeldt Iversen
Abstract
Arctic Ocean sea ice cover is shrinking due to warming. Long-term sediment trap data shows higher export efficiency of particulate organic carbon in regions with seasonal sea ice compared to regions without sea ice. To investigate this sea-ice enhanced export, we compared how different early summer phytoplankton communities in seasonally ice-free and ice-covered regions of the Fram Strait affect carbon export and vertical dispersal of microbes. In situ collected aggregates revealed two-fold higher carbon export of diatom-rich aggregates in ice-covered regions, compared to Phaeocystis aggregates in the ice-free region. Using microbial source tracking, we found that ice-covered regions were also associated with more surface-born microbial clades exported to the deep sea. Taken together, our results showed that ice-covered regions are responsible for high export efficiency and provide strong vertical microbial connectivity. Therefore, continuous sea-ice loss may decrease the vertical export efficiency, and thus the pelagic-benthic coupling, with potential repercussions for Arctic deep-sea ecosystems.