Large-scale Patterns and Drivers of the Biological Carbon Pump: Insights from in situ Camera Observations across the Pacific Ocean

The ocean’s biological carbon pump plays an important role in global biogeochemistry and climate, yet our present understanding of this process is limited, in part due to the constraints of conventional observational approaches that have resulted in sparse and heterogeneous datasets on marine particle concentrations and fluxes. Using an in situ oceanographic imaging system integrated with the CTD rosette, we mapped the abundances and size distributions of marine particles (60 μm - 2.7 cm) across a full-depth latitudinal transect of the Pacific Ocean between French Polynesia and Alaska (P16N). These data reveal remarkable features including the widespread existence of a mesopelagic maximum in large particle abundance as well as distinct and coherent zones of elevated particle concentrations that extend from the surface all the way to the seafloor. We explore the drivers of these patterns including large-scale hydrography and biogeography, the role of zooplankton vertical migration, and the origin, properties, and dynamics of the particulate matter itself. Our results shed new light on the large-scale variability of the ocean’s biological carbon pump, its drivers, and biogeochemical implications.