Coastal upwelling enhances abundance of a symbiotic diazotroph (UCYN-A) and its haptophyte host in the Arctic Ocean

The apparently obligate symbiosis between the diazotroph Candidatus Atelocyanobacterium thalassa (UCYN-A) and its haptophyte host, Braarudosphaera bigelowii , has recently been found to fix dinitrogen (N 2 ) in polar waters at rates (per cell) comparable those observed tropical/subtropical oligotrophic ocean basins. This study presents novel observation that this increased abundance during a wind-driven upwelling event along Alaskan Beaufort shelfbreak. As relaxed, relative of B. among eukaryotic phytoplankton most significantly over upper slope. host’s nitrogen demands are believed be supplied primarily by UCYN-A, response suggests may enhance N fixation as displaced coastal advected offshore, potentially extending duration upwelling-induced blooms. Given such events projected increase intensity number with warming, upwelling-driven feedback on climate merits investigation.