Capacity for Denitrification and Reduction of Nitrate to Ammonia in a Coastal Marine Sediment

Abstract

The capacity for dissimilatory reduction of NO 3 − to N 2 (N 2 O) and NH 4 + was measured in 15 NO 3 − -amended marine sediment. Incubation with acetylene (7 � 10 −3 atmospheres [normal]) caused accumulation of N 2 O in the sediment. The rate of N 2 O production equaled the rate of N 2 production in samples without acetylene. Complete inhibition of the reduction of N 2 O to N 2 suggests that the “acetylene blockage technique” is applicable to assays for denitrification in marine sediments. The capacity for reduction of NO 3 − by denitrification decreased rapidly with depth in the sediment, whereas the capacity for reduction of NO 3 − to NH 4 + was significant also in deeper layers. The data suggested that the latter process may be equally as significant as denitrification in the turnover of NO 3 − in marine sediments.