Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones
We present new data for the stable isotope ratio of inorganic nitrogen species from the contrasting oxygen minimum zones (OMZs) of the Eastern Tropical North Atlantic, south of Cape Verde, and the Eastern Tropical South Pacific off Peru. Differences in minimum oxygen concentration and corresponding...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2012-01-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/9/203/2012/bg-9-203-2012.pdf |
| _version_ | 1819241988539547648 |
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| author | E. Ryabenko A. Kock H. W. Bange M. A. Altabet D. W. R. Wallace |
| author_facet | E. Ryabenko A. Kock H. W. Bange M. A. Altabet D. W. R. Wallace |
| author_sort | E. Ryabenko |
| collection | DOAJ |
| description | We present new data for the stable isotope ratio of inorganic nitrogen species
from the contrasting oxygen minimum zones (OMZs) of the Eastern Tropical North
Atlantic, south of Cape Verde, and the Eastern Tropical South Pacific off Peru.
Differences in minimum oxygen concentration and corresponding N-cycle processes
for the two OMZs are reflected in strongly contrasting δ<sup>15</sup>N distributions. Pacific
surface waters are marked by strongly positive values for δ<sup>15</sup>N-NO<sub>3</sub><sup>–</sup>) reflecting
fractionation associated with subsurface N-loss and partial NO<sub>3</sub><sup>–</sup> utilization.
This contrasts with negative values in NO<sub>3</sub><sup>–</sup> depleted surface waters of the Atlantic
which are lower than can be explained by N supply via N<sub>2</sub> fixation. We suggest the
negative values reflect inputs of nitrate, possibly transient, associated with
deposition of Saharan dust. Strong signals of N-loss processes in the subsurface
Pacific OMZ are evident in the isotope and N<sub>2</sub>O data, both of which are compatible
with a contribution of canonical denitrification to overall N-loss. However the
apparent N isotope fractionation factor observed is relatively low (ϵ<sub>d</sub>=11.4 ‰)
suggesting an effect of influence from denitrification in sediments. Identical
positive correlation of N<sub>2</sub>O vs. AOU for waters with oxygen concentrations ([O<sub>2</sub>] < 5 μmol l<sup>−1</sup>) in
both regions reflect a nitrification source. Sharp decrease in N<sub>2</sub>O concentrations
is observed in the Pacific OMZ due to denitrification under oxygen concentrations O<sub>2</sub> < 5 μmol l<sup>−1</sup>. |
| first_indexed | 2024-12-23T14:32:39Z |
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| id | doaj.art-c20e940af6e04d4eb7578c4b52dde5ad |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-23T14:32:39Z |
| publishDate | 2012-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-c20e940af6e04d4eb7578c4b52dde5ad2022-12-21T17:43:27ZengCopernicus PublicationsBiogeosciences1726-41701726-41892012-01-019120321510.5194/bg-9-203-2012Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum ZonesE. Ryabenko0A. Kock1H. W. Bange2M. A. Altabet3D. W. R. Wallace4Leibniz-Institut für Meereswissenschaften an der Universität Kiel (IFM-GEOMAR), Forschungsbereich Marine Biogeochemie, Düsternbrooker Weg 20, Kiel, GermanyLeibniz-Institut für Meereswissenschaften an der Universität Kiel (IFM-GEOMAR), Forschungsbereich Marine Biogeochemie, Düsternbrooker Weg 20, Kiel, GermanyLeibniz-Institut für Meereswissenschaften an der Universität Kiel (IFM-GEOMAR), Forschungsbereich Marine Biogeochemie, Düsternbrooker Weg 20, Kiel, GermanySchool for Marine Science and Technology (SMAST), University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA, USAHalifax Marine Research Institute, Dalhousie University, 1355 Oxford Street, P.O.~Box 15000, Halifax, Nova Scotia B3H 4R2, CanadaWe present new data for the stable isotope ratio of inorganic nitrogen species from the contrasting oxygen minimum zones (OMZs) of the Eastern Tropical North Atlantic, south of Cape Verde, and the Eastern Tropical South Pacific off Peru. Differences in minimum oxygen concentration and corresponding N-cycle processes for the two OMZs are reflected in strongly contrasting δ<sup>15</sup>N distributions. Pacific surface waters are marked by strongly positive values for δ<sup>15</sup>N-NO<sub>3</sub><sup>–</sup>) reflecting fractionation associated with subsurface N-loss and partial NO<sub>3</sub><sup>–</sup> utilization. This contrasts with negative values in NO<sub>3</sub><sup>–</sup> depleted surface waters of the Atlantic which are lower than can be explained by N supply via N<sub>2</sub> fixation. We suggest the negative values reflect inputs of nitrate, possibly transient, associated with deposition of Saharan dust. Strong signals of N-loss processes in the subsurface Pacific OMZ are evident in the isotope and N<sub>2</sub>O data, both of which are compatible with a contribution of canonical denitrification to overall N-loss. However the apparent N isotope fractionation factor observed is relatively low (ϵ<sub>d</sub>=11.4 ‰) suggesting an effect of influence from denitrification in sediments. Identical positive correlation of N<sub>2</sub>O vs. AOU for waters with oxygen concentrations ([O<sub>2</sub>] < 5 μmol l<sup>−1</sup>) in both regions reflect a nitrification source. Sharp decrease in N<sub>2</sub>O concentrations is observed in the Pacific OMZ due to denitrification under oxygen concentrations O<sub>2</sub> < 5 μmol l<sup>−1</sup>.http://www.biogeosciences.net/9/203/2012/bg-9-203-2012.pdf |
| spellingShingle | E. Ryabenko A. Kock H. W. Bange M. A. Altabet D. W. R. Wallace Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones Biogeosciences |
| title | Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones |
| title_full | Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones |
| title_fullStr | Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones |
| title_full_unstemmed | Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones |
| title_short | Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones |
| title_sort | contrasting biogeochemistry of nitrogen in the atlantic and pacific oxygen minimum zones |
| url | http://www.biogeosciences.net/9/203/2012/bg-9-203-2012.pdf |
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