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

Stéphane Blain*, Bernard Quéguiner, Leanne Armand, Sauveur Belviso, Bruno Bombled, Laurent Bopp, Andrew Bowie, Christian Brunet, Corina Brussaard, François Carlotti, Urania Christaki, Antoine Corbière, Isabelle Durand, Frederike Ebersbach, Jean Luc Fuda, Nicole Garcia, Loes Gerringa, Brian Griffiths, Catherine Guigue, Christophe GuillermStéphanie Jacquet, Catherine Jeandel, Patrick Laan, Dominique Lefèvre, Claire Lo Monaco, Andrea Malits, Julie Mosseri, Ingrid Obernosterer, Young Hyang Park, Marc Picheral, Philippe Pondaven, Thomas Remenyi, Valérie Sandroni, Géraldine Sarthou, Nicolas Savoye, Lionel Scouarnec, Marc Souhaut, Doris Thuiller, Klaas Timmermans, Thomas Trull, Julia Uitz, Pieter Van Beek, Marcel Veldhuis, Dorothée Vincent, Eric Viollier, Lilita Vong, Thibaut Wagener

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

522 Citations (Scopus)

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 cycles. To date, the role of iron in carbon cycling has largely been assessed using short-term iron-addition experiments. 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 timescales. 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 experiments. 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 palaeoclimatic and future climate change scenarios-may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

Original languageEnglish
Pages (from-to)1070-1074
Number of pages5
JournalNature
Volume446
Issue number7139
DOIs
Publication statusPublished - 26 Apr 2007
Externally publishedYes

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