Carbon-controlled nitrogen cycling in a marine 'macrocosm'- an ecosystem-scale model for managing cultural eutrophication

Both data whlch we present for Tomales Bay (California, USA) and general geochemical reasoning provide evidence to suggest that nearshore marine env~ronments tend to be net heterotrophic by a small margin, and that these systems oxidize on the order of 1 % of their primary production by denitrification. The rate of denitrification can be interpreted to be a simple stoichiometric function of the margin of heterotrophy. Carbon oxidation by denitrification is trivial to the total C budget, but fixed N loss is sufficient to cause apparent N-limitation of primary production in these systems. We suggest that heterotrophic C metabolism causes the apparent N limitation of primary production, and that control of the N cycle by C has important implications for environmental management.