Estimation of primary production in the ocean using a physical–biological coupled ocean carbon cycle model

A lower-trophic marine ecosystem model that takes into account both the grazing food web and the microbial food web has been developed to investigate the ocean carbon cycle. The ecosystem model was coupled to an oceanic general circulation model and a simulation was performed to examine the temporal and spatial distribution of primary production in the world ocean. Numerical results revealed that the total amount of annual net primary production reaches nearly 61.2 GtC, showing fair agreement with the recent estimates based on the satellite image analysis. The annual flux of particulate organic carbon toward the subsurface layer, viz., the export flux, was evaluated as 5.5 GtC. The model results reproduced the general tendency that the regions of low latitude are characterized by high primary productivity as well as low export flux, and suggested a dominant role for the microbial food web in the oceanic carbon cycle.