The relative influences of nitrogen and phosphorus on oceanic primary production

A simple model has the potential to resolve the long-running debate amongst oceanographers over whether nitrogen or phosphorus exerts overall control on oceanic primary production. A representation of the competition between nitrogen-fixing and other phytoplankton is inserted into a two-box global m odel of the oceanic nitrogen and phosphorus cycles. Homeostatic regulation of both nitrate and phosphate concentrations results, with surface waters m ore deficient in nitrate than phosphate in the steady state, but with exter nal phosphate inputs controlling longer-term primary production in the glob al ocean.