Biological carbon pump efficiency enhanced by atmospheric dust deposition in the North Pacific Subtropical Gyre

We examine the flux and composition of sinking particles collected at 4500 m depth in the southeastern part of the North Pacific Subtropical Gyre (NPSG) from August 2011 to June 2012. Satellite-derived net primary production was higher in January-May 2012 compared with the rest of the study period. Both the biogenic and lithogenic particle fluxes were significantly higher in spring (March-May 2012) than at other times. The export efficiency via the transfer of produced organic carbon to the deep ocean interior (i.e., carbon sequestration) doubled during this time. Two prominent particle flux peaks were observed in March and May 2012, coinciding with the atmospheric dust-deposition peaks within the temporal resolution of the data. Coincident increases in the biogenic and lithogenic particle fluxes suggest that dust deposition in the NPSG enhances the biological carbon-pump efficiency. Strong coupling between the particulate organic carbon and biogenic opal fluxes implies that nutrient supply via atmospheric dust deposition stimulated diatom growth in this area. Dust deposition during the productive season therefore plays an important role in carbon sequestration.