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Deep carbon export from a Southern Ocean iron-fertilized diatom bloom

Nature volume 487, pages 313–319 (2012)Cite this article

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Abstract

Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence—although each with important uncertainties—lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.

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Figure 1: Experimental eddy and the fertilized patch.
Figure 2: Temporal evolution of chlorophyll and silicate concentrations.
Figure 3: Temporal evolution of dissolved and particulate elements.
Figure 4: Temporal evolution of particulate organic carbon stocks in successive depth layers.
Figure 5: Depth-integrated particulate organic carbon stocks.

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Acknowledgements

We thank C. Balt, K. Loquay, S. Mkatshwa, H. Prandke, H. Rohr, M. Thomas and I. Vöge for help on board. We are also grateful to U. Struck for POC and PON analyses. The altimeter products were produced by Ssalto/Duacs and distributed by Aviso with support from Cnes. We thank the captain and crew of RV Polarstern (cruise ANT XXI/3) for support throughout the cruise.

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Author notes

  1. Victor Smetacek and Christine Klaas: These authors contributed equally to this work.

Authors and Affiliations

  1. Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany,

    Victor Smetacek, Christine Klaas, Volker H. Strass, Philipp Assmy, Boris Cisewski, Ulrich Bathmann, Joachim Henjes, Martin Losch, Ilka Peeken, Oliver Sachs, Eberhard Sauter, Jill Schwarz, Anja Terbrüggen & Dieter Wolf-Gladrow

  2. National Institute of Oceanography, Dona Paula, Goa 403 004, India,

    Victor Smetacek

  3. Norwegian Polar Institute, Fram Centre, Hjalmar Johansens Gate 14, 9296 Tromsø, Norway,

    Philipp Assmy

  4. Ecology and Evolution of Plankton, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121-Napoli, Italy

    Marina Montresor

  5. Johann Heinrich von Thünen Institute, Institute of Sea Fisheries, Palmaille 9, 22767 Hamburg, Germany,

    Boris Cisewski

  6. Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium,

    Nicolas Savoye

  7. Univ. Bordeaux/CNRS, EPOC, UMR 5805, Station Marine d’Arcachon, 2 rue du Professeur Jolyet, F-33120 Arcachon, France,

    Nicolas Savoye

  8. Oceanography Department, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa,

    Adrian Webb

  9. LOCEAN-IPSL, CNRS/UPMC/IRD/MNHN, 4 Place Jussieu, 75252 Paris Cedex 5, France,

    Francesco d’Ovidio

  10. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands,

    Jesús M. Arrieta, Santiago Gonzalez & Gerhard J. Herndl

  11. Department of Global Change Research, Instituto Mediterraneo de Estudios Avanzados, CSIC-UIB, Miquel Marques 21, 07190 Esporles, Mallorca, Spain,

    Jesús M. Arrieta

  12. Leibniz Institute for Baltic Sea Research Warnemünde, Seestraße 15, 18119 Rostock, Germany,

    Ulrich Bathmann

  13. Bjerknes Centre for Climate Research, University of Bergen, Allegaten 55, N-5007 Bergen, Norway,

    Richard Bellerby & Craig Neill

  14. Norwegian Institute for Water Research, Thormøhlensgate 53 D, 5006 Bergen, Norway,

    Richard Bellerby

  15. Department of Environmental Earth System Science, Stanford University, Stanford, 94305, California, USA

    Gry Mine Berg & Matthew M. Mills

  16. Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany,

    Peter Croot & Linn J. Hoffmann

  17. Earth and Ocean Sciences, School of Natural Sciences, National University of Ireland, Galway, Quadrangle Building, University Road, Galway, Ireland

    Peter Croot

  18. Phytolutions GmbH, Campus Ring 1, Bremen, 28759, Germany

    Joachim Henjes

  19. Department of Marine Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria,

    Gerhard J. Herndl

  20. School of Environmental Sciences, University of Liverpool, Room 209 Nicholson Building, 4 Brownlow Street, Liverpool L69 3GP, UK,

    Harry Leach

  21. Wealth from Oceans Flagship, Commonwealth Scientific and Industrial Research Organisation, Castray Esplanade, Hobart, Tasmania 7000, Australia,

    Craig Neill

  22. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, D-28359 Bremen, Germany,

    Ilka Peeken

  23. Institute for Coastal Research, Helmholtz-Zentrum Geesthacht, Center for Materials and Coastal Research, Max-Planck-Strasse 1, 21502 Geesthacht, Germany,

    Rüdiger Röttgers

  24. Eberhard & Partner AG, General Guisan Strasse 2, 5000 Arau, Switzerland,

    Oliver Sachs

  25. Centre for Biomolecular Interactions Bremen, FB 2, University of Bremen, Postfach 33 04 40, 28359 Bremen, Germany,

    Maike M. Schmidt

  26. School of Marine Science & Engineering, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK,

    Jill Schwarz

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  1. Victor Smetacek
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Contributions

V.S. and C.K. wrote the manuscript. V.S. directed the experiment and C.K. carried out the budget calculations. V.H.S., P.A., M.M. and D.W.-G. contributed to the preparation of the manuscript. V.H.S., B.C., H.L. and M.L. contributed physical data on mixed-layer depth dynamics, eddy coherence, patch movement and transmissometer data. N.S. provided thorium data. A.W. provided nutrient data. P.A. and J.H. provided phytoplankton and BSi data. F.D. carried out the Lagrangian analysis based on delayed-time altimetry. J.M.A. and G.J.H. provided bacterial data. C.N. and R.B. provided inorganic carbon data. G.M.B., C.K. and M.M.M. provided POC and PON data. P.C. provided the iron data. S.G. and A.T. provided DOM data. I.P. and L.J.H. performed the 14C primary production measurements and provided high-pressure liquid chromatography data. R.R. provided data on photochemical efficiency (Fv/Fm). C.K., M.M.S. and A.T. provided Chl data. U.B., E.S., O.S. and J.S. provided data on the eddy core from a subsequent cruise and satellite Chl images.

Corresponding authors

Correspondence to Victor Smetacek or Christine Klaas.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information 1

This file contains Supplementary Text and Data 1-5 (see contents). Each section also includes Supplementary Figures, Supplementary Tables and additional references. (PDF 14229 kb)

Supplementary Information 2

This file contains Supplementary Methods, additional references, Supplementary Figures 1-7 and Supplementary Tables 1-3. This file was replaced on 20 July 2012, as the figures that appeared in the original file were incorrect. (PDF 6258 kb)

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Smetacek, V., Klaas, C., Strass, V. et al. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom. Nature 487, 313–319 (2012). https://doi.org/10.1038/nature11229

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