Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone.

Kalvelage, Tim, Lavik, Gaute, Lam, Phyllis, Contreras, Sergio, Arteaga, Lionel, Löscher, Carolin R., Oschlies, Andreas , Paulmier, Aurélien, Stramma, Lothar and Kuypers, Marcel M. M. (2013) Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone. Nature Geoscience, 6 (3). pp. 228-234. DOI 10.1038/ngeo1739.

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Abstract

Oxygen minimum zones are expanding globally, and at present account for around 20–40% of oceanic nitrogen loss. Heterotrophic denitrification and anammox—anaerobic ammonium oxidation with nitrite—are responsible for most nitrogen loss in these low-oxygen waters. Anammox is particularly significant in the eastern tropical South Pacific, one of the largest oxygen minimum zones globally. However, the factors that regulate anammox-driven nitrogen loss have remained unclear. Here, we present a comprehensive nitrogen budget for the eastern tropical South Pacific oxygen minimum zone, using measurements of nutrient concentrations, experimentally determined rates of nitrogen transformation and a numerical model of export production. Anammox was the dominant mode of nitrogen loss at the time of sampling. Rates of anammox, and related nitrogen transformations, were greatest in the productive shelf waters, and tailed off with distance from the coast. Within the shelf region, anammox activity peaked in both upper and bottom waters. Overall, rates of nitrogen transformation, including anammox, were strongly correlated with the export of organic matter. We suggest that the sinking of organic matter, and thus the release of ammonium into the water column, together with benthic ammonium release, fuel nitrogen loss from oxygen minimum zones.

Document Type: Article
Additional Information: WOS:000316945800026
Keywords: oxygen minimum; zones, nitrogen cycling, organic matter export
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754 > B4
OceanRep > SFB 754
OceanRep > SFB 754 > A2
OceanRep > SFB 754 > A5
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > SFB 754 > B1
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1038/ngeo1739
ISSN: 1752-0894
Projects: SFB754, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 11 Mar 2013 09:38
Last Modified: 20 Feb 2017 14:20
URI: http://oceanrep.geomar.de/id/eprint/20682

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