COASTAL METABOLISM AND THE OCEANIC ORGANIC-CARBON BALANCE

Net organic metabolism (that is, the difference between primary produc tion and respiration of organic matter) in the coastal ocean may be a significant term in the oceanic carbon budget. Historical change in th e rate of this net metabolism determines the importance of the coastal ocean relative to anthropogenic perturbations of the global carbon cy cle. Consideration of long-term rates of river loading of organic carb on, organic burial, chemical reactivity of land-derived organic matter , and rates of community metabolism in the coastal zone leads us to es timate that the coastal zone oxidizes about 7 x 10(12) moles C/yr. The open ocean is apparently also a site of net organic oxidation (approx imately 16 x 10(12) moles C/yr). Thus organic metabolism in the ocean appears to be a source Of CO2 release to the atmosphere rather than be ing a sink for atmospheric carbon dioxide. The small area of the coast al ocean accounts for about 30% of the net oceanic oxidation. Oxidatio n in the coastal zone (especially in bays and estuaries) takes on part icular importance, because the input rate is likely to have been alter ed substantially by human activities on land.