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| Titel |
Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific Oxygen Minimum Zones |
| VerfasserIn |
E. Ryabenko, A. Kock, H. W. Bange, M. A. Altabet, D. W. R. Wallace |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 1 ; Nr. 9, no. 1 (2012-01-11), S.203-215 |
| Datensatznummer |
250006660
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| Publikation (Nr.) |
 copernicus.org/bg-9-203-2012.pdf |
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| Zusammenfassung |
| 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 δ15N distributions. Pacific
surface waters are marked by strongly positive values for δ15N-NO3–) reflecting
fractionation associated with subsurface N-loss and partial NO3– utilization.
This contrasts with negative values in NO3– depleted surface waters of the Atlantic
which are lower than can be explained by N supply via N2 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 N2O 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 (ϵd=11.4 ‰)
suggesting an effect of influence from denitrification in sediments. Identical
positive correlation of N2O vs. AOU for waters with oxygen concentrations ([O2] < 5 μmol l−1) in
both regions reflect a nitrification source. Sharp decrease in N2O concentrations
is observed in the Pacific OMZ due to denitrification under oxygen concentrations O2 < 5 μmol l−1. |
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