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Nitrogen transformations as inferred from the activities of key enzymes in the Arabian Sea oxygen minimum zone

DRS at CSIR-National Institute of Oceanography

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Title Nitrogen transformations as inferred from the activities of key enzymes in the Arabian Sea oxygen minimum zone
 
Creator Shailaja, M.S.
Narvekar, P.V.
Alagarsamy, R.
Naqvi, S.W.A.
 
Subject enzyme activities
oxygen minimum zone
nitrous oxide
 
Description Vertical distributions of the potential activities of some key enzymes mediating nitrification and denitrification were investigated within the oxygen (O2) minimum zone of the Arabian Sea at a number of locations between latitudes 17 and 21°N and longitudes 63 and 68°E so as to get an insight into the predominant biochemical mode(s) of production and consumption of nitrous oxide (N2O). Results revealed that the dissimilatory nitrate (NO3(super)-) reduction activity was generally very low or absent within the sigma theta range 26.6-26.8, which corresponds to the Persian Gulf Watermass (PGW). Depth profiles of nitrate reductase (NaR), nitrite reductase (NiR) and ammonia monooxygenase (AMO) activities were compared with those of O2, NO3(super)-, nitrite (NO2(super)-) and N2O, and it is concluded that nitrifier denitrification rather than heterotrophic denitrification is active within the core of PGW. The presence of multiple peaks of AMO activity coinciding with distinct maxima in the O2 profile and with a trend opposite to that of NaR activity indicates that the two processes, viz., classical and nitrifier denitrification, occur in discrete layers, probably determined by the variations in the ambient O2 concentrations at various depths surrounding the PGW core. Further, it appears that at the depths where nitrifier denitrification is active in the absence of heterotrophic denitrification, N2O builds up as its consumption may be inhibited by O2. Possible reasons for the occurrence of appreciable nitrate deficit within the core of PGW, where dissimilatory NO3(super)- reduction is lacking, are discussed.
 
Date 2006-12-11T10:49:02Z
2006-12-11T10:49:02Z
2006
 
Type Journal Article
 
Identifier Deep-Sea Research I, vol.53(6), 960-970p.
http://drs.nio.org/drs/handle/2264/533
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2006] Elsevier
 
Format 222305 bytes
application/pdf
 
Publisher Elsevier