Large-scale geographical variation in prokaryotic abundance and production in meso- and bathypelagic zones of the central Pacific and Southern Ocean

Heterotrophic production and abundance of prokaryotes (i.e., Bacteria and Archaea) in meso- (200-1000 m) and bathypelagic (> 1000 m) zones were measured at 31 stations along meridional transects of the central Pacific and Pacific sector of the Southern Ocean, covering a latitudinal range from 67.5 degrees S to 53.6 degrees N. Prokaryotic production and biomass in the mesopelagic zone displayed strong regional variation, generally consistent with model-based estimates of sinking particulate organic carbon (POC) flux patterns. In the bathypelagic zone, the prokaryotic abundance distributions reflected sinking POC flux patterns, whereas the prokaryotic production distributions were complex and unrelated to sinking POC fluxes. In general, the prokaryotic carbon consumption (PCC) was accounted for by the POC flux, within a factor of three, except in the bathypelagic zone of the subtropical region, where PCC exceeded the POC flux at 1000 m by up to seven times. Our results generally support the notion that prokaryote abundance and production distributions in the ocean's interior display consistent vertical patterns among distant locations and generally reflect the POC flux regime over a large scale, although complex prokaryotic production distributions in the bathypelagic zone might indicate the presence of links between regional hydrographic features and organic carbon delivery in deep waters.