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A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization

Nature volume 407, pages 695–702 (2000)Cite this article

Abstract

Changes in iron supply to oceanic plankton are thought to have a significant effect on concentrations of atmospheric carbon dioxide by altering rates of carbon sequestration, a theory known as the ‘iron hypothesis’. For this reason, it is important to understand the response of pelagic biota to increased iron supply. Here we report the results of a mesoscale iron fertilization experiment in the polar Southern Ocean, where the potential to sequester iron-elevated algal carbon is probably greatest. Increased iron supply led to elevated phytoplankton biomass and rates of photosynthesis in surface waters, causing a large drawdown of carbon dioxide and macronutrients, and elevated dimethyl sulphide levels after 13 days. This drawdown was mostly due to the proliferation of diatom stocks. But downward export of biogenic carbon was not increased. Moreover, satellite observations of this massive bloom 30 days later, suggest that a sufficient proportion of the added iron was retained in surface waters. Our findings demonstrate that iron supply controls phytoplankton growth and community composition during summer in these polar Southern Ocean waters, but the fate of algal carbon remains unknown and depends on the interplay between the processes controlling export, remineralisation and timescales of water mass subduction.

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Figure 1: Site selection, pre-release survey and water-column structure.
Figure 2: Temporal evolution of physical, chemical and biological properties during SOIREE.
Figure 3: Time-series measurements made during SOIREE.
Figure 4: A vertical section (from the southeast to the northwest) through the iron-enriched patch on the night of 22 February.
Figure 5: Changes in chlorophyll a levels with time during an on-deck iron/light perturbation experiment.

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Acknowledgements

We thank the officers and crew of the RV Tangaroa, and the management and staff of the NIWA Vessel Management Company. We also acknowledge the provision of physical oceanographic data by J. Church, M. Morris, V. Strass, RV Astrolab, and J. Barth and T. Cowles. We also thank M. Walkington (CTD calibration), J. Aiken (instrument loan), P. Nightingale (argos reception for tracking buoys), S. Groom (near-time high resolution Ocean Color satellite images), NASA (SeaWiFS images), and the companies CEFIC (UK) and BHP (Australia) for their support. We acknowledge two grants from the UK NERC to S.T. (Advanced Fellowship Award), and to A.J.W. and C.S.L. (SOIREE). K.O.B. and M.C. were funded by the US NSF. M.T.M. was funded by the NSERC Canada and the Center for Environmental Bioinorganic Chemistry, Princeton, USA. P.C., A.J.W. and D.C.E.B. received a grant within CARUSO from the European Union. New Zealand scientists were funded by the Government PGSF fund for Antarctic Research. J. Cullen, K. Hunter and C. Hurd provided comments and advice that improved this manuscript.

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Author notes

  1. Maria T. Maldonado

    Present address: School of Marine Sciences, University of Maine, Orono, Maine, 04469, USA

Authors and Affiliations

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

    Philip W. Boyd

  2. School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK

    Andrew J. Watson, Dorothee C. E. Bakker, Kim Tanneberger & Suzanne Turner

  3. Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH , Devon, UK

    Cliff S. Law, Andrew R. Bowie, Greg Jameson, Malcolm Liddicoat & Roger Ling

  4. National Institute of Water and Atmosphere, Greta Point, PO Box 14-901, Wellington, New Zealand

    Edward R. Abraham, Rob Murdoch, Hoe Chang, Ken Downing, Mark Hadfield, Mike Harvey, Scott Nodder & Philip Sutton

  5. Antarctic Co-operative Research Centre, University of Tasmania, GPO Box 252-80, Hobart, 7001, Tasmania, Australia

    Thomas Trull

  6. Department of Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK

    Andrew R. Bowie

  7. Department of Marine Chemistry and Geochemistry MS25 Woods Hole Oceanographic Institute, Woods Hole, 02543, Massachusetts , USA

    K. O. Buesseler & Matthew Charette

  8. Department of Marine Chemistry and Geology, Netherlands Institute for Sea Research (NIOZ), Postbus 59, Den Burg – Texel, 1790 AB, The Netherlands

    Peter Croot

  9. Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand

    Russell Frew

  10. National Institute of Water and Atmosphere, Christchurch , PO Box 8602, Christchurch, New Zealand

    Mark Gall & John Zeldis

  11. National Institute of Water and Atmosphere, Hamilton , Box 11-115, Hamilton, New Zealand

    Julie Hall, Stu Pickmere, Rick Pridmore & Karl Safi

  12. Institut fuer Meereskunde, Universitaet Kiel, Duesternbrooker Weg 20, Kiel, D-24105, Germany

    Julie LaRoche

  13. Biology Department, McGill University, 1205 Avenue, Dr. Penfield, Montreal, PQ H2T 2V8, Canada

    Maria T. Maldonado

  14. Department of Biological Sciences, Bowling Green State University, Bowling Green, 43403, Ohio, USA

    R. Michael McKay

  15. CSIRO Division of Marine Research, GPO Box 1538, Hobart, 7001, Tasmania, Australia

    Steve Rintoul

  16. Departments of Botany and Oceanography, University of British Columbia, 6270 University Boulevard, Vancouver, V6T 1Z4, BC, Canada

    Robert Strzepek

  17. Department of Environmental Engineering, Centre for Water Research, University of Western Australia, Nedlands, 6907, Western Australia, Australia

    Anya Waite

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Correspondence to Philip W. Boyd.

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Boyd, P., Watson, A., Law, C. et al. A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization. Nature 407, 695–702 (2000). https://doi.org/10.1038/35037500

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