Denitrification and nitrous oxide production in a coastal marine ecosystem1

Abstract

Denitrification was measured directly as the flux of N₂ from sediment cores collected at various times of year at three stations in the Narragansett Bay, R.I., area. Rates of N₂ production ranged from about 10 to 115 µmol N·m^‒2·h^‒1, with lowest values at 2°C in winter and highest at 15°C in summer. Denitrification represents a major sink for fixed N in the bay; annually the N₂ production is equal to about 50% of the fixed inorganic N loading to the bay from rivers, land, and sewage. About 35% of the organic nitrogen mineralized in the sediments is removed from the ecosystem by denitrification.The percentage of organic nitrogen being mineralized in the sediments as N₂O relative to N₂ or NO₃^‒ + NO₂^‒ is higher in polluted sediments than in relatively unpolluted sediments, but in all cases is < 10%.