Coastal versus open-ocean denitrification in the Arabian Sea
Open Access
- 14 December 2006
- journal article
- Published by Copernicus GmbH in Biogeosciences (online)
- Vol. 3 (4), 621-633
- https://doi.org/10.5194/bg-3-621-2006
Abstract
The Arabian Sea contains one of the three major open-ocean denitrification zones in the world. In addition, pelagic denitrification also occurs over the inner and mid-shelf off the west coast of India. The major differences between the two environments are highlighted using the available data. The perennial open-ocean system occupies two orders of magnitude larger volume than the seasonal coastal system, however, the latter offers more extreme conditions (greater nitrate consumption leading to complete anoxia). Unlike the open-ocean system, the coastal system seems to have undergone a change (i.e., it has intensified) over the past few decades presumably due to enhanced nutrient loading from land. The two systems also differ from each other with regard to the modes of nitrous oxide (N2O) production: In the open-ocean suboxic zone, an accumulation of secondary nitrite (NO2−) is invariably accompanied by depletion of N2O whereas in the coastal suboxic zone high NO2− and very high N2O concentrations frequently co-occur, indicating, respectively, net consumption and net production of N2O by denitrifiers. The extents of heavier isotope enrichment in the combined nitrate and nitrite (NO3−+NO2−) pool and in N2O in reducing waters appear to be considerably smaller in the coastal region, reflecting more varied sources/sinks and/or different isotopic fractionation factors.Keywords
This publication has 58 references indexed in Scilit:
- Annual ecosystem variability in the tropical Indian Ocean: Results of a coupled bio-physical ocean general circulation modelDeep Sea Research Part II: Topical Studies in Oceanography, 2006
- Iodine chemistry reflects productivity and denitrification in the Arabian Sea: evidence for flux of dissolved species from sediments of western India into the OMZDeep Sea Research Part II: Topical Studies in Oceanography, 2002
- Northern Arabian Sea variability from TOPEX/Poseidon altimetry data: an extension of the US JGOFS/ONR shipboard ADCP studyDeep Sea Research Part II: Topical Studies in Oceanography, 2001
- The oxygen minimum zone in the Arabian Sea during 1995Deep Sea Research Part II: Topical Studies in Oceanography, 1999
- Nano- and microplankton in the northern Arabian Sea during the Southwest Monsoon, August–September 1995 A US–JGOFS studyDeep Sea Research Part II: Topical Studies in Oceanography, 1998
- Upper ocean currents in the northern Arabian Sea from shipboard ADCP measurements collected during the 1994–1996 U.S. JGOFS and ONR programsDeep Sea Research Part II: Topical Studies in Oceanography, 1998
- Seasonal variation of hydrographic and nutrient fields during the US JGOFS Arabian Sea Process StudyDeep Sea Research Part II: Topical Studies in Oceanography, 1998
- Sub-surface iodide maxima: evidence for biologically catalyzed redox cycling in Arabian Sea OMZ during the SW intermonsoonDeep Sea Research Part II: Topical Studies in Oceanography, 1997
- Activity of the respiratory electron transport system and respiration rates within the oxygen minimum layer of the Arabian SeaDeep Sea Research Part II: Topical Studies in Oceanography, 1993
- Nitrogen biogeochemical cycling in the northwestern Indian OceanDeep Sea Research Part II: Topical Studies in Oceanography, 1993