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Denitrification as the dominant nitrogen loss process in the Arabian Sea

DRS at CSIR-National Institute of Oceanography

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Title Denitrification as the dominant nitrogen loss process in the Arabian Sea
 
Creator Ward, B.B.
Devol, A.H.
Rich, J.J.
Chang, B.X.
Bulow, S.E.
Naik, H.
Pratihary, A.K.
Jayakumar, A.
 
Subject Denitrification
Primary production
oxygen minimum zones
anammox
 
Description Primary production in over half of the world’s oceans is limited by fixed nitrogen availability. The main loss term from the fixed nitrogen inventory is the production of dinitrogen gas (N sub(2)) by heterotrophic denitrification or the more recently discovered autotrophic process, anaerobic ammonia oxidation (anammox). Oceanic oxygen minimum zones (OMZ) are responsible for about 35% of oceanic N sub(2) production and up to half of that occurs in the Arabian Sea. Although denitrification was long thought to be the only loss term, it has recently been argued that anammox alone is responsible for fixed nitrogen loss in the OMZs. Here we measure denitrification and anammox rates and quantify the abundance of denitrifying and anammox bacteria in the OMZ regions of the Eastern Tropical South Pacific and the Arabian Sea. It is found that denitrification rather than anammox dominates the N sub(2) loss term in the Arabian Sea, the largest and most intense OMZ in the world ocean. In seven of eight experiments in the Arabian Sea denitrification is responsible for 87-99% of the total N sub(2) production. The dominance of denitrification is reproducible using two independent isotope incubation methods. In contrast, anammox is dominant in the Eastern Tropical South Pacific OMZ, as detected using one of the isotope incubation methods, as previously reported. The abundance of denitrifying bacteria always exceeded that of anammox bacteria by up to 7- and 19-fold in the Eastern Tropical South Pacific and Arabian Sea, respectively. Geographic and temporal variability in carbon supply may be responsible for the different contributions of denitrification and anammox in these two OMZs. The large contribution of denitrification to N sub(2) loss in the Arabian Sea indicates the global significance of denitrification to the oceanic nitrogen budget
 
Date 2009-11-17T11:48:50Z
2009-11-17T11:48:50Z
2009
 
Type Journal Article
 
Identifier Nature, vol.461(8276); 78-82
www.nature.com/doifinder/10.1038/nature08276
http://drs.nio.org/drs/handle/2264/3443
 
Language en
 
Rights An edited version of this paper was published by Nature Publishing Group. Copyright [2009] Nature Publishing Group.
 
Publisher Nature Publishing Group