Denitrification and Nitrogen Fixation in Alaskan Continental Shelf Sediments

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Abstract
In some regions, rates of N fixation and denitrification appeared to be equal; in other areas, rates were significantly different. Potential rates of denitrification were limited primarily by the available nitrate substrate. Major regional differences in rates of denitrification were not statistically significant, but significant differences were found for N fixation rates in different regions of the Alaskan continental shelf. Estimated net losses of N from Bering Sea sediments were calculated as 1.8 .times. 1012 g of N/yr. Experimental exposure of continental shelf sediments to petroleum hydrocarbons reduced rates of N fixation and denitrification in some cases, but not others. Long-term exposure was necessary before a reduction in N fixation rates was observed; unamended rates of denitrification, but not potential denitrification rates (NO3- added), were depressed after exposure to hydrocarbons.