Origin of the deep Bering Sea nitrate deficit : Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes
Moritz F. Lehmann,Moritz F. Lehmann,Daniel M. Sigman,Daniel C. McCorkle,Brigitte G. Brunelle,Sharon Hoffmann,Markus Kienast,Greg Cane,J. L. Clement +8 more
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In this paper, the authors measured water column nitrate 15N/14N and 18O/16O as integrative tracers of microbial denitrification, together with pore water-derived benthic nitrate fluxes in the deep Bering Sea basin, in order to gain new constraints on the mechanism of fixed nitrogen loss in the BS.Abstract:
[1] On the basis of the normalization to phosphate, a significant amount of nitrate is missing from the deep Bering Sea (BS). Benthic denitrification has been suggested previously to be the dominant cause for the BS nitrate deficit. We measured water column nitrate 15N/14N and 18O/16O as integrative tracers of microbial denitrification, together with pore water-derived benthic nitrate fluxes in the deep BS basin, in order to gain new constraints on the mechanism of fixed nitrogen loss in the BS. The lack of any nitrate isotope enrichment into the deep part of the BS supports the benthic denitrification hypothesis. On the basis of the nitrate deficit in the water column with respect to the adjacent North Pacific and a radiocarbon-derived ventilation age of ∼50 years, we calculate an average deep BS (>2000 m water depth) sedimentary denitrification rate of ∼230 μmol N m−2 d−1 (or 1.27 Tg N yr−1), more than 3 times higher than high-end estimates of the average global sedimentary denitrification rate for the same depth interval. Pore water-derived estimates of benthic denitrification were variable, and uncertainties in estimates were large. A very high denitrification rate measured from the base of the steep northern slope of the basin suggests that the elevated average sedimentary denitrification rate of the deep Bering calculated from the nitrate deficit is driven by organic matter supply to the base of the continental slope, owing to a combination of high primary productivity in the surface waters along the shelf break and efficient down-slope sediment focusing along the steep continental slopes that characterize the BS.read more
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Mesoscale iron enrichment experiments 1993-2005 : Synthesis and future directions
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Journal ArticleDOI
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References
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Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis
Philip N. Froelich,Gary P. Klinkhammer,Michael L. Bender,Nile A. Luedtke,G.R. Heath,Doug Cullen,Paul Dauphin,Doug Hammond,Blayne Hartman,Val Maynard +9 more
TL;DR: Pore water profiles of total CO 2, pH, PO 3−4, NO − 3 plus NO − 2, SO 2− 4, S 2−, Fe 2+ and Mn 2+ have been obtained in cores from pelagic sediments of the eastern equatorial Atlantic under waters of moderate to high productivity as mentioned in this paper.
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Denitrification in freshwater and coastal marine ecosystems: Ecological and geochemical significance
TL;DR: Denitrification occurs in essentially all river, lake, and coastal marine ecosystems that have been studied as discussed by the authors, and the major source of nitrate for denitrification in most river and lake sediments underlying an aerobic water column is nitrate produced in the sediments, not nitrate diffusing into the overlying water.
Journal ArticleDOI
A Bacterial Method for the Nitrogen Isotopic Analysis of Nitrate in Seawater and Freshwater
Daniel M. Sigman,Karen L. Casciotti,Muriel Andreani,Carol C. Barford,M. Galanter,John Karl Böhlke +5 more
TL;DR: The precision of the method is better than 0.2/1000 (1 SD) at concentrations of nitrate down to 1 microM, and the nitrogen isotopic differences among various standards and samples are accurately reproduced.
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