Effect of natural iron fertilization on carbon sequestration in the Southern Ocean.
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.
Blain
Stéphane
S
Laboratoire d'Océanographie et de Biogéochimie, Centre Océanologique de Marseille, CNRS, Université de la Méditerranée, campus de Luminy, case 901, 13288 Marseille Cedex 09, France. stephane.blain@univmed.fr
Quéguiner
Bernard
B
Armand
Leanne
L
Belviso
Sauveur
S
Bombled
Bruno
B
Bopp
Laurent
L
Bowie
Andrew
A
Brunet
Christian
C
Brussaard
Corina
C
Carlotti
François
F
Christaki
Urania
U
Corbière
Antoine
A
Durand
Isabelle
I
Ebersbach
Frederike
F
Fuda
Jean-Luc
JL
Garcia
Nicole
N
Gerringa
Loes
L
Griffiths
Brian
B
Guigue
Catherine
C
Guillerm
Christophe
C
Jacquet
Stéphanie
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Jeandel
Catherine
C
Laan
Patrick
P
Lefèvre
Dominique
D
Lo Monaco
Claire
C
Malits
Andrea
A
Mosseri
Julie
J
Obernosterer
Ingrid
I
Park
Young-Hyang
YH
Picheral
Marc
M
Pondaven
Philippe
P
Remenyi
Thomas
T
Sandroni
Valérie
V
Sarthou
Géraldine
G
Savoye
Nicolas
N
Scouarnec
Lionel
L
Souhaut
Marc
M
Thuiller
Doris
D
Timmermans
Klaas
K
Trull
Thomas
T
Uitz
Julia
J
van Beek
Pieter
P
Veldhuis
Marcel
M
Vincent
Dorothée
D
Viollier
Eric
E
Vong
Lilita
L
Wagener
Thibaut
T
D001272:Atmosphere / Q000737:chemistry; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D004058:Diffusion; D005843:Geography; D007501:Iron / Q000378:metabolism*; D009792:Oceans and Seas; D010313:Partial Pressure; D010839:Phytoplankton / Q000378:metabolism*; D012623:Seawater / Q000737:chemistry*; D013997:Time Factors
D002734:Chlorophyll; D002245:Carbon Dioxide; D002244:Carbon; D007501:Iron; D000077194:Chlorophyll A