Inter-Research
Aquatic Microbial Ecology

ABSTRACT: Direct measurements of dinitrogen efflux from continental shelf sediments indicated that denitrification (mean 3.2 mmol N m^-2 d^-1) was very important in nitrogen cycling. Most dinitrogen came from sediment-nitrate. All ammonium produced in these sediments was probably nitrified and then denitrified. In a closed incubation, the linear production of dinitrogen, as oxygen decreased, was unexpected as was the low ratio of oxygen consumption to denitrification (3.6:1). Simulation modelling suggests the following explanation: Most carbon is oxidised anoxically, but nitrogen (ammonium) diffuses to the oxygen zone relatively deep in the sediment, where high rates of coupled nitrification-denitrification result. As oxygen decreases, the zones of nitrification and denitrification move upward. The nitrate initially present in the enclosed overlying water decreases, but due to the decreasing diffusional path to the zone of denitrification, its rate of denitrification remains constant. The concentration of nitrate from sediment nitrification increases in the overlying water, but due to the decreasing rates of sediment nitrification, its rate of denitrification is also constant.

KEY WORDS: Nitrification . Denitrification . Model . Diffusion . Nitrate . Ammonium

Published in AME Vol. 10, No. 2 (1996) on May 9
Print ISSN: 0948-3055; Online ISSN: 1616-1564. Copyright © Inter-Research, Oldendorf/Luhe, 1996