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Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions

Citation

Scholz, F and Loscher, CR and Fiskal, A and Sommer, S and Hensen, C and Lomnitz, U and Wuttig, K and Gottlicher, J and Kossel, E and Steininger, R and Canfield, DE, Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions, Earth and Planetary Science Letters, 454 pp. 272-281. ISSN 0012-821X (2016) [Refereed Article]

Copyright Statement

2016 Elsevier

DOI: doi:10.1016/j.epsl.2016.09.025

Abstract

Iron is an essential element for life on Earth and limits primary production in large parts of the ocean. Oxygen-free continental margin sediments represent an important source of bioavailable iron to the ocean, yet little of the iron released from the seabed reaches the productive sea surface. Even in the anoxic water of oxygen minimum zones, where iron solubility should be enhanced, most of the iron is rapidly re-precipitated. To constrain the mechanism(s) of iron removal in anoxic ocean regions we explored the sediment and water in the oxygen minimum zone off Peru. During our sampling campaign the water column featured two distinct redox boundaries separating oxic from nitrate-reducing (i.e., nitrogenous) water and nitrogenous from weakly sulfidic water. The sulfidic water mass in contact with the shelf sediment contained elevated iron concentrations >300 nM. At the boundary between sulfidic and nitrogenous conditions, iron concentrations dropped sharply to <20 nM coincident with a maximum in particulate iron concentration. Within the iron gradient, we found an increased expression of the key functional marker gene for nitrate reduction (narG). Part of this upregulation was related to the activity of known iron-oxidizing bacteria. Collectively, our data suggest that iron oxidation and removal is induced by nitrate-reducing microbes, either enzymatically through anaerobic iron oxidation or by providing nitrite for an abiotic reaction. Given the important role that iron plays in nitrogen fixation, photosynthesis and respiration, nitrate-dependent iron oxidation likely represents a key-link between the marine biogeochemical cycles of nitrogen, oxygen and carbon.

Item Details

Item Type:Refereed Article
Keywords:iron (II) oxidation, nitrate reduction, oxygen minimum zone, anoxic marine sediment, X-ray absorption spectroscopy
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical Oceanography
Objective Division:Environment
Objective Group:Physical and Chemical Conditions of Water
Objective Field:Physical and Chemical Conditions of Water not elsewhere classified
Author:Wuttig, K (Dr Kathrin Wuttig)
ID Code:112847
Year Published:2016
Web of Science® Times Cited:5
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2016-11-30
Last Modified:2017-04-27
Downloads:0

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