Importance of coastal nutrient supply for global ocean biogeochemistry

The coastal ocean provides nutrients to the open ocean in accounts that are poorly quantified. We use an ocean biogeochemistry model to assess the importance of the coastal nutrient supply to global ocean biogeochemistry. The model includes full cycles of P, Si, and Fe, as well as the representation of two phytoplankton groups, two zooplankton groups, and two organic detritus pools. When coastal mixing is enhanced to reproduce the action of tides and storms, primary production and chlorophyll-a (Chla) concentrations show a large increase at the coast and a smaller increase in the open ocean. When coastal nutrient supply is enhanced to reproduce sediment resuspension or river supply, both the coastal ocean and the open ocean primary production and Chla concentration increase in comparable amounts. In agreement with the definition of nutrient limitation areas in the model, coastal export of P-excess impacts mainly the subtropical oligotrophic areas, Si-excess impacts the Arctic Ocean and some coastal areas, and Fe-excess impacts the east equatorial Pacific, North Atlantic and North Pacific, and the Southern Ocean. Modeled Chla is closest to observations when the input ratio of Fe to P and Si is enhanced.