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MEPS 261:111-122 (2003)
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Abstract
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Response of coccolithophorid Emiliania huxleyi to elevated partial pressure of CO2 under nitrogen limitation
Antoine Sciandra1,*, Jérome Harlay2, Dominique Lefèvre3, Rodolphe Lemée1, Peguy Rimmelin3, Michel Denis3, Jean-Pierre Gattuso1
1Laboratoire d'Océanographie, Université Mixte de Recherche (UMR) 7093, Centre National de la Recherche Scientifique- Université Pierre et Marie Curie (CNRS-UPMC), BP 28, 06234 Villefranche-sur-mer Cedex, France
2Service d'Océanographie Chimique et Géochimie des Eaux, Université Libre de Bruxelles, Campus Plaine, CP 208, Boulevard du Triomphe, 1050 Brussels, Belgium
3Laboratoire d'Océanographie et de Biogéochimie, Centre d'Océanologie de Marseille, Université Mixte de Recherche (UMR) 6535, Centre National de la Recherche Scientifique (CNRS)-Université de la Méditerranée, Case 901, 13288 Marseille Cedex 9,
France
*Email: sciandra@obs-vlfr.fr
ABSTRACT: Precipitation of calcium carbonate by phytoplankton in the photic oceanic layer is an important process regulating the carbon cycling and the exchange of CO2 at the ocean-atmosphere interface. Previous experiments have demonstrated
that, under nutrient-sufficient conditions, doubling the partial pressure of CO2 (pCO2) in seawater--a likely scenario for the end of the century--can significantly decrease both the rate of calcification by coccolithophorids and the
ratio of inorganic to organic carbon production. The present work investigates the effects of high pCO2 on calcification by the coccolithophore Emiliania huxleyi (Strain TW1) grown under nitrogen-limiting conditions, a situation that can
also prevail in the ocean. Nitrogen limitation was achieved in NO3-limited continuous cultures renewed at the rate of 0.5 d-1 and exposed to a saturating light level. pCO2 was increased from 400 to 700 ppm and controlled
by bubbling CO2-rich or CO2-free air into the cultures. The pCO2 shift has a rapid effect on cell physiology that occurs within 2 cell divisions subsequent to the perturbation. Net calcification rate (C) decreased
by 25% and, in contrast to previous studies with N-replete cultures, gross community production (GCP) and dark community respiration (DCR) also decreased. These results suggest that increasing pCO2 has no noticeable effect on the
calcification/photosynthesis ratio (C/P) when cells of E. huxleyi are NO3-limited.
KEY WORDS: Calcification · Carbon fixation · Coccolith · Emiliania huxleyi · Nitrate · Alkalinity · CO2
Full text in pdf format
Published in MEPS Vol.
261
(2003) on October 17
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2003
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