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

Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone
Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone
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.
1752-0894
228-234
Kalvelage, Tim
216fac21-892d-46d7-995d-5e959962bc06
Lavik, Gaute
29014780-d97c-41c0-8b59-a230bdfcdb37
Lam, Phyllis
996aef80-a15d-4827-aed8-1b97b378f6ad
Contreras, Sergio
7faae1cd-7a96-4023-9996-f6b19ea6627c
Arteaga, Lionel
ea096fe1-1774-4675-b450-c01e6f3c6cc2
Löscher, Carolin R.
5bb36dee-bcea-4703-a16d-43af486a8daf
Oschlies, Andreas
75e18f55-3134-44a2-82ba-71334397727f
Paulmier, Aurélien
b7592678-0e73-4384-b36f-846c06a978da
Stramma, Lothar
90bb48f0-5d94-4302-873e-2101b4c6974f
Kuypers, Marcel M.M.
b6288cfb-42bc-469c-93fe-8fbb40d97bec
Kalvelage, Tim
216fac21-892d-46d7-995d-5e959962bc06
Lavik, Gaute
29014780-d97c-41c0-8b59-a230bdfcdb37
Lam, Phyllis
996aef80-a15d-4827-aed8-1b97b378f6ad
Contreras, Sergio
7faae1cd-7a96-4023-9996-f6b19ea6627c
Arteaga, Lionel
ea096fe1-1774-4675-b450-c01e6f3c6cc2
Löscher, Carolin R.
5bb36dee-bcea-4703-a16d-43af486a8daf
Oschlies, Andreas
75e18f55-3134-44a2-82ba-71334397727f
Paulmier, Aurélien
b7592678-0e73-4384-b36f-846c06a978da
Stramma, Lothar
90bb48f0-5d94-4302-873e-2101b4c6974f
Kuypers, Marcel M.M.
b6288cfb-42bc-469c-93fe-8fbb40d97bec

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), 228-234. (doi:10.1038/ngeo1739).

Record type: Article

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.

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More information

e-pub ahead of print date: 24 February 2013
Published date: 2013
Organisations: Ocean Biochemistry & Ecosystems

Identifiers

Local EPrints ID: 349907
URI: http://eprints.soton.ac.uk/id/eprint/349907
ISSN: 1752-0894
PURE UUID: b5479898-79d3-4271-b254-3d1179f74151
ORCID for Phyllis Lam: ORCID iD orcid.org/0000-0003-2067-171X

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Date deposited: 13 Mar 2013 13:12
Last modified: 15 Mar 2024 03:47

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Contributors

Author: Tim Kalvelage
Author: Gaute Lavik
Author: Phyllis Lam ORCID iD
Author: Sergio Contreras
Author: Lionel Arteaga
Author: Carolin R. Löscher
Author: Andreas Oschlies
Author: Aurélien Paulmier
Author: Lothar Stramma
Author: Marcel M.M. Kuypers

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