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The biogeochemical cycle of iron in the ocean

Nature Geoscience volume 3, pages 675–682 (2010)Cite this article

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Abstract

Advances in iron biogeochemistry have transformed our understanding of the oceanic iron cycle over the past three decades: multiple sources of iron to the ocean were discovered, including dust, coastal and shallow sediments, sea ice and hydrothermal fluids. This new iron is rapidly recycled in the upper ocean by a range of organisms; up to 50% of the total soluble iron pool is turned over weekly in this way in some ocean regions. For example, bacteria dissolve particulate iron and at the same time release compounds — iron-binding ligands — that complex with iron and therefore help to keep it in solution. Sinking particles, on the other hand, also scavenge iron from solution. The balance between these supply and removal processes determines the concentration of dissolved iron in the ocean. Whether this balance, and many other facets of the biogeochemical cycle, will change as the climate warms remains to be seen.

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Figure 1: Dissolved iron vertical profiles illustrating aspects of supply and removal processes.
Figure 2: Size-partitioning of iron and iron-binding ligands with depth.
Figure 3: Modification of aerosol iron upon entering surface waters.
Figure 4: Multiple sources of new iron to the Southern Ocean.
Figure 5: Biological iron recycling in the upper ocean.
Figure 6: The influence of particle scavenging and remineralization on dissolved iron concentrations in three zones (0–250 m (blue), 250–1,000 m (orange) and >1,000 m (grey)) denoted in panels a–c.

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Acknowledgements

We thank A. Bowie (Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania) for providing unpublished dissolved iron data from the Southern Ocean (Fig. 1a), and L. Bucke (Department of Chemistry, University of Otago) for help with the graphics. We thank S. Solokov and S. Rintoul (CSIRO, Hobart, Tasmania) and G. Jackson (Texas A&M) for providing personal communications regarding bottom pressure torque and vertical changes in particle surface area, respectively.

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  1. Department of Chemistry, National Institute of Water and Atmosphere Centre of Chemical and Physical Oceanography, University of Otago, Dunedin, New Zealand

    P. W. Boyd

  2. Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

    M. J. Ellwood

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Boyd, P., Ellwood, M. The biogeochemical cycle of iron in the ocean. Nature Geosci 3, 675–682 (2010). https://doi.org/10.1038/ngeo964

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