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Effect of natural iron fertilization on carbon sequestration in the Southern Ocean

Abstract

The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an important role in the carbon cycle, and changes in its supply to the surface ocean may have had a significant effect on atmospheric carbon dioxide concentrations over glacial–interglacial cycles1,2,3,4,5. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments6,7. It is difficult, however, to reliably assess the magnitude of carbon export to the ocean interior using such methods, and the short observational periods preclude extrapolation of the results to longer timescales8. Here we report observations of a phytoplankton bloom induced by natural iron fertilization—an approach that offers the opportunity to overcome some of the limitations of short-term experiments. We found that a large phytoplankton bloom over the Kerguelen plateau in the Southern Ocean was sustained by the supply of iron and major nutrients to surface waters from iron-rich deep water below. The efficiency of fertilization, defined as the ratio of the carbon export to the amount of iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments7. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting that changes in iron supply from below—as invoked in some palaeoclimatic9,10 and future climate change scenarios11—may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

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Figure 1: Location of the study sites, temporal evolution of the bloom and surface water properties.
Figure 2: Iron fertilization above the plateau.
Figure 3: Carbon export at A3 and C11.

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References

  1. Martin, J. H. Glacial-interglacial CO2 change: The iron hypothesis. Paleoceanography 5, 1–13 (1990)

    Article  ADS  Google Scholar 

  2. Brzezinsky, M. A. et al. A switch from Si(OH)4 to NO3- depletion in the glacial Southern Ocean. Geophys. Res. Lett. 29 doi: 10.1029/2001GL014349 (2002)

  3. Sigman, D. M. & Boyle, E. A. Glacial/interglacial variations in atmospheric carbon dioxide. Science 407, 859–869 (2000)

    CAS  Google Scholar 

  4. Bopp, L., Kohfeld, K. E., Le Quéré, C. & Aumont, O. Dust impact on marine biota and atmospheric CO2 during glacial periods. Paleoceanography 18 doi: 10.1029/2002PA000810 (2003)

  5. Watson, A. J., Bakker, D. C. E., Ridgwell, A. J., Boyd, P. W. & Law, C. Effect of iron supply on Southern Ocean CO2 uptake and implications for glacial atmospheric CO2 . Nature 407, 730–733 (2000)

    Article  ADS  CAS  Google Scholar 

  6. Boyd, P. W. et al. Mesoscale iron enrichment experiments 1993–2005: Synthesis and future directions. Science 315, 612–617 (2007)

    Article  ADS  CAS  Google Scholar 

  7. De Baar, H. J. W. et al. Synthesis of iron fertilization experiments: from the iron age in the age of enlightenment. J. Geophys. Res. 110 doi: 10.1029/2004JC002601 (2005)

  8. Boyd, P. W., Jackson, G. A. & Waite, A. M. Are mesoscale perturbation experiments in polar waters prone to physical artefacts? Evidence from algal aggregation modelling studies. Geophys. Res. Lett. 20 doi: 10.1029/2001GL014210 (2002)

  9. Ridgwell, A. J. & Watson, A. Feedback between aeolian dust, climate, and atmospheric CO2 in glacial time. Paleoceanogr. 17 1059 doi: 10.1029/2001PA000729 (2002)

    Article  ADS  Google Scholar 

  10. Latimer, J. C. & Filipelli, G. M. Terrigenous input and paleoproductivity in the Southern Ocean. Paleoceanography 16, 627–643 (2001)

    Article  ADS  Google Scholar 

  11. Jickells, T. D. et al. Global iron connections between desert dust, ocean biogeochemistry, and climate. Science 308, 67–71 (2005)

    Article  ADS  CAS  Google Scholar 

  12. Sarmiento, J. L., Hughes, C. W., Stouffer, R. J. & Manabe, S. Simulated response of the ocean carbon cycle to anthropogenic climate warming. Nature 393, 245–249 (1998)

    Article  ADS  CAS  Google Scholar 

  13. Marinov, I., Gnanadesikan, A., Toggweiler, J. R. & Sarmiento, J. L. The Southern Ocean biogeochemical divide. Nature 441, 964–967 (2006)

    Article  ADS  CAS  Google Scholar 

  14. Coale, K. H. et al. Southern Ocean iron enrichment experiment: Carbon cycling in high- and low-Si waters. Science 304, 408–414 (2004)

    Article  ADS  CAS  Google Scholar 

  15. Boyd, P. W. et al. A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization. Nature 407, 695–702 (2000)

    Article  ADS  CAS  Google Scholar 

  16. Gervais, F., Riebesell, U. & Gorbunov, M. Y. Change in primary productivity and chlorophyll a response to iron fertilization in the Southern Polar Frontal Zone. Limnol. Oceanogr. 47, 1324–1335 (2002)

    Article  ADS  CAS  Google Scholar 

  17. Hart, T. J. Phytoplankton periodicity in Antarctic surface water. Discov. Rep. VIII, 1–268 (1942)

    Google Scholar 

  18. Sullivan, C. W., Arrigo, K. R., McClain, C. R., Comiso, J. C. & Firestone, J. Distribution of phytoplankton blooms in the Southern Ocean. Science 262, 1832–1837 (1993)

    Article  ADS  CAS  Google Scholar 

  19. Tyrell, T. et al. Effect of seafloor depth and phytoplankton blooms in high nitrate low chlorophyll (HNLC) regions. J. Geophys. Res. 110 doi: 10.1029/2005JG000041 (2005)

  20. Blain, S. et al. A biogeochemical study of the island mass effect in the context of the iron hypothesis: Kerguelen Islands, Southern Ocean. Deep-sea Res. I 48, 163–187 (2001)

    Article  CAS  Google Scholar 

  21. Measures, C. I. & Vink, S. Dissolved Fe in the upper waters of the Pacific sector of the Southern Ocean. Deep-sea Res. II 48, 3913–3941 (2001)

    Article  ADS  CAS  Google Scholar 

  22. Timmermans, K. R. et al. Growth rates of large and small Southern Ocean diatoms in relation to availability of iron in natural seawater. Limnol. Oceanogr. 46, 260–266 (2001)

    Article  ADS  Google Scholar 

  23. Law, C., Abraham, E. R., Watson, A. & Liddicoat, M. Vertical eddy diffusion and nutrient supply to the surface mixed layer of the Antarctic Circumpolar Current. J. Geophys. Res. 108 doi: 10.1029/2002JC001604 (2003)

  24. Boyd, P. W. et al. FeCycle: attempting an iron biogeochemical budget from a mesoscale SF6 tracer experiment in unperturbated low iron waters. Glob. Biochem. Cycles 19 doi: 10.1029/2005GB002494 (2005)

  25. Rutgers Van Der Loeff, M. M., Buesseler, K. O., Bathmann, U., Hense, I. & Andrews, J. Comparison of carbon and opal export rates between summer and spring bloom in the region of the Antarctic Polar Front, SE Atlantic. Deep-sea Res. II 49, 3849–3869 (2002)

    Article  ADS  CAS  Google Scholar 

  26. Buesseler, K. O., Andrews, J. E., Pike, S. M. & Charette, M. A. The effects of iron fertilization on carbon sequestration in the Southern Ocean. Science 304, 414–417 (2004)

    Article  ADS  CAS  Google Scholar 

  27. Bowie, A. R. et al. The fate of added iron during a mesoscale fertilisation experiment in the Southern Ocean. Deep-sea Res. II 48, 2703–2743 (2001)

    Article  ADS  CAS  Google Scholar 

  28. Gnanadesikan, A., Sarmiento, J. L. & Slater, R. D. Effects of patchy ocean fertilization on atmospheric carbon dioxide and biological production. Glob. Biochem. Cycles 17 doi: 10.1029/2002GB001940 (2003)

  29. Buesseler, K. O. & Boyd, P. W. Will ocean fertilization work? Science 300, 67–68 (2003)

    Article  CAS  Google Scholar 

  30. Chisholm, S. W., Falkowski, P. G. & Cullen, J. J. Dis-crediting ocean fertilization. Science 294, 309–310 (2001)

    Article  CAS  Google Scholar 

  31. Wanninkhof, R. H. & McGillis, W. R. A cubic relationship between air-sea exchange and wind speed. Geophys. Res. Lett. 26, 1889–1892 (1999)

    Article  ADS  CAS  Google Scholar 

  32. Nightingale, P. et al. In situ elevation of the sea-air gas exchange parameterisations using novel conservative and volatile tracers. Glob. Biochem. Cycles 14, 373–387 (2000)

    Article  ADS  CAS  Google Scholar 

  33. Jabaud, A., Metzl, N., Brunet, C., Poisson, A. & Schauer, B. Interannual variability of the carbon dioxide system in the Southern Indian Ocean (20°S-60°S): the impact of a warm anomaly in austral summer. Glob. Biochem. Cycles 18 doi: 10.1029/2002GB002017 (2004)

  34. Osborn, T. R. Estimate of vertical diffusion from dissipation measurements. J. Phys. Oceanogr. 10, 83–89 (1980)

    Article  ADS  Google Scholar 

  35. Dillon, T. M. Vertical overturns: a comparison of Thorpe and Ozmidov length scales. J. Geophys. Res. 85, 9601–9613 (1982)

    Article  ADS  Google Scholar 

  36. Sarthou, G. et al. Atmospheric iron deposition and sea-surface dissolved iron concentrations in the eastern Atlantic Ocean. Deep-Sea Res. I 50, 1339–1352 (2003)

    Article  CAS  Google Scholar 

  37. Croot, P. & Johansson, M. Determination of iron speciation by cathodic stripping voltammetry in seawater using the competing ligand 2-(2-thiazolylazo-p-cresol (TAC). Electroanalysis 12, 565–576 (2000)

    Article  CAS  Google Scholar 

  38. Johnson, K. S. et al. Sampling and analysis of Fe: The SAFE iron intercomparison cruise. Eos Trans. AGU 87(36), Ocean Sci. Meet. Suppl. (2006)

  39. Cullen, J. T. & Sherrel, M. Techniques for determination of trace metal in small samples of size-fractionated particulate matter: phytoplankton metals off central California. Mar. Chem. 67, 233–247 (1999)

    Article  CAS  Google Scholar 

  40. Wedepohl, K. H. The composition of continental crust. Geochim. Cosmochim. Acta 59, 1217–1232 (1995)

    Article  ADS  CAS  Google Scholar 

  41. Fernandez, C., Raimbault, P., Caniaux, Y., Garcia, N. & Rimmelin, P. An estimation of annual new production and carbon budget in the northeast Atlantic Ocean during 2001. J. Geophys. Res. 110 doi: 10.1029/2004JC002621 (2005)

  42. Pike, S. M., Buesseler, K. O., Andrews, J. & Savoye, N. Quantification of 234Th recovery in small volume of sea water samples by inductively coupled plasma-mass spectrometry. J. Radioanal. Nucl. Chem. 263, 355–360 (2005)

    Article  CAS  Google Scholar 

  43. Robinson, C. & Williams, P. J. I. Plankton net community production and dark respiration in the Arabian Sea during September 1994. Deep-Sea Res. II 46, 745–765 (1999)

    Article  ADS  CAS  Google Scholar 

  44. Savoye, N. et al. 234Th sorption and export models in the water column: a review. Mar. Chem. 100, 234–249 (2006)

    Article  CAS  Google Scholar 

Download references

Acknowledgements

We thank the captain and the crew of the RV Marion Dufresne. This work was supported by the Institut National des Sciences de L’Univers (INSU) and the Centre National de la Recherche Scientifique (CNRS), l’Institut Paul Emile Victor (IPEV), French-Australian Science and Technology (FAST), the Australian Commonwealth Cooperative Research Centre programme through the Antarctic Climate and Ecosystem CRC, and Belgian Science Policy (BELSPO). The project benefited from collaboration with N. Metzl, leader of Ocean Indien Service d’Observation (OISO) supported by INSU, IPEV and Institut Pierre Simon Laplace (IPSL). We acknowledge the contributions of V. Barthaux, P. Catala, J. Caparros and J. Raz (technical assistance), and M.P. Jouandet (computation of the seasonal carbon budget).

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Correspondence to Stéphane Blain.

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Supplementary Information

This file contains Supplementary Discussion which includes description of the ecosystem structure; Supplementary Table 1 illustrating uncertainties of the basics terms of the DFe and Carbon budgets; Supplementary Table 2 with carbon biomass of major components of the plankton community; Supplementary Table 3 showing contribution of major diatom species at A3 and C11; Supplementary Figure 1 illustrating mean vertical profiles of nitrate, silicic acid and phosphate at A3 and C11 and additional references. (PDF 317 kb)

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Blain, S., Quéguiner, B., Armand, L. et al. Effect of natural iron fertilization on carbon sequestration in the Southern Ocean. Nature 446, 1070–1074 (2007). https://doi.org/10.1038/nature05700

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