The impact of ocean deoxygenation on iron release from continental margin sediments

Scholz, Florian, McManus, James, Mix, Alan C., Hensen, Christian and Schneider, Ralph (2014) The impact of ocean deoxygenation on iron release from continental margin sediments Nature Geoscience, 7 (6). pp. 433-437. DOI 10.1038/ngeo2162.

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Abstract

In the oceans’ high-nitrate–low-chlorophyll regions, such as the Peru/Humboldt Current system and the adjacent eastern equatorial Pacific1, primary productivity is limited by the micronutrient iron. Within the Peruvian upwelling area, bioavailable iron is released from the reducing continental margin sediments2. The magnitude of this seafloor source could change with fluctuations in the extension or intensity of the oxygen minimum zones3, 4. Here we show that measurements of molybdenum, uranium and iron concentrations can be used as a proxy for sedimentary iron release, and use this proxy to assess iron release from the sea floor beneath the Peru upwelling system during the past 140,000 years. We observe a coupling between levels of denitrification, as indicated by nitrogen isotopes, trace metal proxies for oxygenation, and sedimentary iron concentrations. Specifically, periods with poor upper ocean oxygenation are characterized by more efficient iron retention in the sediment and a diminished iron supply to the water column. We attribute efficient iron retention under more reducing conditions to widespread sulphidic conditions in the surface sediment and concomitant precipitation of iron sulphides. We argue that iron release from continental margin sediments is most effective in a narrow redox window where neither oxygen nor sulphide is present. We therefore suggest that future deoxygenation in the Peru upwelling area would be unlikely to result in increased iron availability, whereas in weaker oxygen minimum zones partial deoxygenation may enhance the iron supply.

Document Type: Article
Additional Information: WOS:000337164400015
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > SFB 754 > B5
OceanRep > SFB 754
OceanRep > SFB 754 > A6
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1038/ngeo2162
ISSN: 1752-0894
Projects: SFB754, BICYCLE, Future Ocean
Date Deposited: 07 Jul 2014 07:36
Last Modified: 03 Nov 2016 12:34
URI: http://eprints.uni-kiel.de/id/eprint/25230

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