Nitrate Deficits by Denitrification and Partial Nitrification Processes in the Pacific Ocean

The model to separate the nitrate deficits produced by the denitrification (dN") and by partial nitrification processes (dN; Li et al, 2006) was applied to the Pacific WOCE data from the cruises P19 and P21E, which traversed the oxygen minimum zones north and south of the eastern equatorial Pacific Ocean. Results are consistent with those obtained from the Arabian Sea. Two dN" maxima coincide with two nitrite maxima and two O2 minima in the north-south cross sections of those parameters. Two dN maxima coincide with nitrate or phosphate maxima, and lie within the lower oxycline below the oxygen minimum zones. The dN production within the upper oxycline is appreciable, but not as prominent as in the lower oxycline. The dN" and dN maxima are in direct contact with the continental shelf and slope sediments, indicating some nitrate deficit inputs from sediments. The nitrate deficit in the bottom water of the Bering Sea is confirmed to be sediment inputs.