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Denitrification in the Arabian Sea: a 3D ecosystem modelling study

Anderson, T.A.; Ryabchenko, V.A.; Fasham, M.J.R.; Gorchakov, V.A.. 2007 Denitrification in the Arabian Sea: a 3D ecosystem modelling study. Deep-Sea Research I, 54 (12). 2082-2119. 10.1016/j.dsr.2007.09.005

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Abstract/Summary

A three-dimensional hydrodynamic-ecosystem model was used to examine the factors determining the spatio-temporal distribution of denitrification in the Arabian Sea. The ecosystem model includes carbon and nitrogen as currencies, cycling of organic matter via detritus and dissolved organic matter, and both remineralization and denitrification as sinks for material exported below the euphotic zone. Model results captured the marked seasonality in plankton dynamics of the region, with characteristic blooms of chlorophyll in the coastal upwelling regions and central Arabian Sea during the southwest monsoon, and also in the northern Arabian Sea during the northeast monsoon as the mixed layer shoals. Predicted denitrification was 26.2 Tg N yr−1,the greatest seasonal contribution being during the northeast monsoon when primary production is co-located with the zone of anoxia. Detritus was the primary organic substrate consumed in denitrification (97%), with a small (3%) contribution by dissolved organic matter. Denitrification in the oxygen minimum zone was predicted to be fuelled almost entirely by organic matter supplied by particles sinking vertically from the euphotic zone above (0.73 mmol N m−2 d−1) rather than from lateral transport of organic matter from elsewhere in the Arabian Sea (less than 0.01 mmol N m−2 d−1). Analysis of the carbon budget in the zone of denitrification (north of 10°N and east of 55°E) indicates that the modelled vertical export flux of detritus, which is similar in magnitude to estimates from field data based on the 234Th method, is sufficient to account for measured bacterial production below the euphotic zone in the Arabian Sea.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.dsr.2007.09.005
ISSN: 0967-0637
Additional Keywords: Denitrification; Biogeochemical cycles; Ecosystem modelling; Detritus; Export flux; Arabian Sea
Date made live: 30 Nov 2007 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/149781

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