<b>Updates to instrumentation and protocols for isotopic analysis of nitrate by the denitrifier method</b>

Weigand, M. Alexandra; Foriel, Julien; Barnett, B. A.; Oleynik, Sergey; Sigman, Daniel M.

doi:10.1002/rcm.7570

Cited by 171 publications

(184 citation statements)

References 27 publications

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“…Individual analyses were referenced to injections from a laboratory standard N 2 O tank and calibrated using the NO 3 − reference materials IAEA ‐ N3 (4.7‰ vs. N 2 and 25.6‰ vs. VSMOW; Böhlke et al, ; Gonfiantini et al, ) and U.S. Geological Survey ‐ 34 (−1.8‰ vs. N 2 ; −27.9‰ vs. VSMOW; Böhlke et al, ), with monitoring of reproducibility by analysis of an internal seawater NO 3 − standard from the deep North Atlantic. NO 3 − standards in individual runs were diluted in nutrient‐free seawater to concentrations equivalent to those of samples to account for potential matrix effects on δ 18 O NO3 measurements (Weigand et al, ). In order to ensure measurement accuracy, samples were analyzed in duplicate within runs, for a minimum of three discrete runs, yielding average standard deviations of 0.2‰ for N and 0.3‰ for O, although with a lower precision averaging 0.4‰ for δ 18 O NO3 at lower NO 3 − concentrations (<10 μM).…”

Section: Methodsmentioning

confidence: 99%

On the Properties of the Arctic Halocline and Deep Water Masses of the Canada Basin from Nitrate Isotope Ratios

et al. 2018

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Nitrogen is a limiting nutrient for primary production in the western Arctic Ocean. Measurements of the nitrogen (15N/14N) and oxygen (18O/16O) isotope ratios of nitrate in the southeastern Beaufort Sea provide insight into biogeochemical cycling of nitrogen in the western Arctic Ocean. Nitrate O isotope ratios in the Pacific halocline evidence a highly regenerated reservoir. Coincident peaks in nutrient concentrations and reduced dissolved oxygen concentrations suggest that nitrate accrues from organic matter remineralization in bottom waters of the Chukchi shelf and that these ventilate the basin predominantly in summer, when isolated from the atmosphere. Preformed nitrate in Pacific Winter Water lacks 18O/16O elevation from nitrate assimilation, contrasting with preformed nitrate in other ocean regions. A reactive N deficit and elevated nitrate N isotope ratios in the Pacific halocline further indicate substantial N loss to coupled nitrification‐denitrification in shelf sediments upstream. In the Atlantic Water below, nitrate isotope ratios identify two distinct waters entering the Arctic at Fram Strait, from (1) the surface West Spitsbergen Current, bearing isotopic signatures akin to North Atlantic waters, and (2) deeper inflows of waters ventilated in the Nordic Seas, transporting nitrate O isotope ratios indicative of regenerated nitrate. Poorly ventilated Canada Basin Deep Water shows evidence of nominal accrual of remineralized products, and nitrate isotope ratios suggest an influence of slow benthic denitrification on the sea floor. The observations reveal that shelf processes have a disproportionate influence on tracer properties of the Pacific halocline, while those in Atlantic Water are dominated by processes in the Nordic Seas.

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Section: Methodsmentioning

confidence: 99%

On the Properties of the Arctic Halocline and Deep Water Masses of the Canada Basin from Nitrate Isotope Ratios

et al. 2018

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“…Each batch of samples intended for mass spectrometric analysis included

{NO}_{3}^{-}

reference materials that was also amended with sulfamic acid to ensure that no contamination originates from this treatment. As a concentration effect is reported for measurements of

{NO}_{3}^{-}

δ 18 O, nitrate reference materials were diluted with low‐nutrient Sargasso Sea surface water to generate concentrations that bracket the concentrations of the samples in each batch (Weigand et al ). We use any trends between the measured δ 18 O of the two references concentrations bracketing of the sample concentrations to generate a linear correction for this trend (Marconi et al ; Weigand et al ).…”

Section: Methodsmentioning

confidence: 99%

Influence of the bordering shelves on nutrient distribution in the Arctic halocline inferred from water column nitrate isotopes

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et al. 2018

Limnology & Oceanography

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The East Siberian Sea and contiguous western Arctic Ocean basin are characterized by a subsurface nutrient maximum in the halocline, generally attributed to both Pacific inflow and intensive remineralization in shelf bottom waters that are advected into the central basin. We report nitrogen and oxygen isotopic measurement of nitrate from the East Siberian Sea and western Eurasian Basin, in order to gain insight into how nitrate is processed by the microbial community and redistributed in the Arctic Ocean. A large decoupling between nitrate δ15N and δ18O is reported, increasing and decreasing upward from the Atlantic temperature maximum layer toward the surface, respectively. A correlation between water and nitrate δ18O indicates that most of the nitrate (> 60%) at the halocline has been regenerated within the Arctic Ocean. The increase in nitrate δ15N correlates with the fixed N deficit, indicating a causal link between the loss of fixed N and the 15N enrichment. This suggests that a significant share of benthic denitrification is driven by nitrate supplied by remineralization and partial nitrification, allowing residual 15N‐enriched ammonium to diffuse out of the sediments. By increasing nutrient concentrations and fixed N deficit in shelf bottom waters, this imprint is attenuated offshore following advection into the halocline by nitrate regeneration and mixing. Estimation of the sedimentary isotope effect related to benthic denitrification yields values in the range of 2.4–3.8‰, with its magnitude driven by both the degree of coupling between remineralization and nitrification, and fixed N concentrations in shelf bottom waters.

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“…Then, the skeleton powder was dissolved with HCl, and the released OM was oxidized into nitrate with alkaline persulfate oxidizing reagent. The concentration of the nitrate in the examined sample was analyzed by chemiluminescence ( 41 ), whereas δ 15 N of nitrate was measured by conversion into nitrous dioxide with the “denitrifier method” ( 42 ), followed by automated extraction, purification, and isotopic analysis of the N 2 O product ( 43 ). Two amino acid reference materials (USGS40 and USGS41) were included in each batch of analyses to correct for the reagent blank of the protocol and to reference the data to atmospheric N 2 , the universal reference.…”

Section: Methodsmentioning

confidence: 99%

Photosymbiosis and the expansion of shallow-water corals

et al. 2016

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Updates to instrumentation and protocols for isotopic analysis of nitrate by the denitrifier method

Cited by 171 publications

References 27 publications

On the Properties of the Arctic Halocline and Deep Water Masses of the Canada Basin from Nitrate Isotope Ratios

On the Properties of the Arctic Halocline and Deep Water Masses of the Canada Basin from Nitrate Isotope Ratios

Influence of the bordering shelves on nutrient distribution in the Arctic halocline inferred from water column nitrate isotopes

Photosymbiosis and the expansion of shallow-water corals

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