Coccolithophore blooms boost particle fluxes in the Nordic Seas

The biological gravitational pump is the primary mechanism exporting particulate organic carbon from the sunlit surface to the deep ocean, particularly inhigh-latitude regions. However, mesopelagic carbon budget deficits indicate additional, unaccounted-for mechanisms that enhance particle export. One hypothesis suggests that biominerals produced by coccolithophores—calcifying phytoplankton—increase the density and sinking speed of marine snow aggregates, thereby boosting carbon export. Yet, the extent of this effect remains unclear, due to limited in situ observations of the associated particle fluxes. Here, we use autonomous BioGeoChemical-Argo float and satellite observations to assess, at a basin scale, how coccolithophore blooms influence carbon export in the Nordic Seas. Our findings reveal that coccolithophore bloom intensity correlates with increased particle export and deep fluxes, with important implications for oceanic carbon sequestration.