Large-scale distribution of Atlantic nitrogen fixation controlled by iron availability


Moore, C. Mark, Mills, Matthew M., Achterberg, Eric P., Geider, Richard J., LaRoche, Julie, Lucas, Mike I., McDonagh, Elaine L., Pan, Xi, Poulton, Alex J., Rijkenberg, Micha J.A., Suggett, David J., Ussher, Simon J. and Woodward, E. Malcolm S. (2009) Large-scale distribution of Atlantic nitrogen fixation controlled by iron availability. Nature Geoscience, 2, (12), 867-871. (doi:10.1038/NGEO667).

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Description/Abstract

Oceanic fixed-nitrogen concentrations are controlled by the balance between nitrogen fixation and denitrification1, 2, 3, 4. A number of factors, including iron limitation5, 6, 7, can restrict nitrogen fixation, introducing the potential for decoupling of nitrogen inputs and losses2, 5, 8. Such decoupling could significantly affect the oceanic fixed-nitrogen inventory and consequently the biological component of ocean carbon storage and hence air–sea partitioning of carbon dioxide2, 5, 8, 9. However, the extent to which nutrients limit nitrogen fixation in the global ocean is uncertain. Here, we examined rates of nitrogen fixation and nutrient concentrations in the surface waters of the Atlantic Ocean along a north–south 10,000 km transect during October and November 2005. We show that rates of nitrogen fixation were markedly higher in the North Atlantic compared with the South Atlantic Ocean. Across the two basins, nitrogen fixation was positively correlated with dissolved iron and negatively correlated with dissolved phosphorus concentrations. We conclude that inter-basin differences in nitrogen fixation are controlled by iron supply rather than phosphorus availability. Analysis of the nutrient content of deep waters suggests that the fixed nitrogen enters North Atlantic Deep Water. Our study thus supports the suggestion that iron significantly influences nitrogen fixation5, and that subsequent interactions with ocean circulation patterns contribute to the decoupling of nitrogen fixation and loss2, 4, 8.

Item Type: Article
ISSNs: 1752-0894 (print)
Related URLs:
Subjects: G Geography. Anthropology. Recreation > GC Oceanography
Divisions: University Structure - Pre August 2011 > School of Ocean & Earth Science (SOC/SOES)
University Structure - Pre August 2011 > National Oceanography Centre (NERC)
ePrint ID: 71613
Date Deposited: 15 Dec 2009
Last Modified: 27 Mar 2014 18:51
Projects:
The biophysical basis of iron-light co-limitation of phytoplankton photosynthesis
Funded by: NERC (NE/C518114/2)
Led by: Christopher Mark Moore
1 July 2007 to 31 December 2008
URI: http://eprints.soton.ac.uk/id/eprint/71613

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