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dc.contributor.authorBrandes, J.A.
dc.contributor.authorDevol, A.H.
dc.contributor.authorYoshinari, T.
dc.contributor.authorJayakumar, D.A.
dc.contributor.authorNaqvi, S.W.A.
dc.date.accessioned2009-01-11T11:53:54Z
dc.date.available2009-01-11T11:53:54Z
dc.date.issued1998
dc.identifier.citationLimnology and Oceanography, Vol.43; 1680-1689p.
dc.identifier.urihttp://drs.nio.org/drs/handle/2264/1911
dc.description.abstractThe delta sup(15)N composition of nitrate and N sub(2) gas was measured in the eastern tropical North Pacific (ETNP) and central Arabian Sea (AS) suboxic regions. The delta sup(15)N of nitrate increased from 6 ppt at 2,500 m to 15 ppt at 250-350 m in both regions, while the delta sup(15)N of N sub(2) concurrently decreased from 0.6 ppt to 0.25 ppt. The denitrification isotopic fractionation factor ( epsilon sub(denit)) for each region was estimated using both advection-reaction and diffusion-reaction models. Values for epsilon sub(denit) in the ETNP ranged from 25 plus or minus 2 (advection-reaction) to 30 plus or minus 3 (diffusion-reaction). Values for epsilon sub(denit) in the central AS varied from 22 plus or minus 3 (advection-diffusion) to 25 plus or minus 4 (reaction-diffusion) using a starting nitrate isotopic composition of 6 ppt but were indistinguishable from calculated values from the ETNP when an initial value of 5 ppt was employed. Based upon the model results, an average global epsilon sub(denit) of 27 plus or minus 3 is proposed for marine suboxic water columns. Isotopic enrichment of nitrate in oxic waters beneath the active denitrification regions was observed and indicates the presence of significant cross-isopycnal ventilation at depth. The isotopic composition of nitrate decreased above 250 m to approx 80 m, and this pattern is hypothesized to be caused by the input of isotopically light nitrogen from nitrogen fixation in the euphotic zone. A simple isotopic mass balance indicates that a significant percentage of primary productivity in the central AS may be fueled by nitrogen fixation
dc.language.isoen
dc.publisherAmerican Society of Limnology and Oceanography
dc.rightsCopyright [1998]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
dc.subjectnitrates
dc.subjectnitrogen cycle
dc.subjectdenitrification
dc.subjectisotope fractionation
dc.subjectadvection
dc.subjectdiffusion
dc.subjectoxic conditions
dc.subjectnitrogen fixation
dc.titleIsotopic composition of nitrate in the central Arabian Sea and eastern tropical North Pacific: A tracer for mixing and nitrogen cycles
dc.typeJournal Article


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