title: Sensitivity of coccolithophores to carbonate chemistry and ocean acidification.
abstract: About one-third of the carbon dioxide (CO(2)) released into the atmosphere as a result of human activity has been absorbed by the oceans, where it partitions into the constituent ions of carbonic acid. This leads to ocean acidification, one of the major threats to marine ecosystems and particularly to calcifying organisms such as corals, foraminifera and coccolithophores. Coccolithophores are abundant phytoplankton that are responsible for a large part of modern oceanic carbonate production. Culture experiments investigating the physiological response of coccolithophore calcification to increased CO(2) have yielded contradictory results between and even within species. Here we quantified the calcite mass of dominant coccolithophores in the present ocean and over the past forty thousand years, and found a marked pattern of decreasing calcification with increasing partial pressure of CO(2) and concomitant decreasing concentrations of CO(3)(2-). Our analyses revealed that differentially calcified species and morphotypes are distributed in the ocean according to carbonate chemistry. A substantial impact on the marine carbon cycle might be expected upon extrapolation of this correlation to predicted ocean acidification in the future. However, our discovery of a heavily calcified Emiliania huxleyi morphotype in modern waters with low pH highlights the complexity of assemblage-level responses to environmental forcing factors.
authors.affiliation: CEREGE, CNRS/Université Aix-Marseille, Avenue L. Philibert BP80, 13545 Aix-en-Provence, Cedex 4, France. beaufort@cerege.fr
authors.forename: L
authors.initials: L
authors.lastname: Beaufort
authors.forename: I
authors.initials: I
authors.lastname: Probert
authors.forename: T
authors.initials: T
authors.lastname: de Garidel-Thoron
authors.forename: E M
authors.initials: EM
authors.lastname: Bendif
authors.forename: D
authors.initials: D
authors.lastname: Ruiz-Pino
authors.forename: N
authors.initials: N
authors.lastname: Metzl
authors.forename: C
authors.initials: C
authors.lastname: Goyet
authors.forename: N
authors.initials: N
authors.lastname: Buchet
authors.forename: P
authors.initials: P
authors.lastname: Coupel
authors.forename: M
authors.initials: M
authors.lastname: Grelaud
authors.forename: B
authors.initials: B
authors.lastname: Rost
authors.forename: R E M
authors.initials: RE
authors.lastname: Rickaby
authors.forename: C
authors.initials: C
authors.lastname: de Vargas
mesh_terms: D059001:Aquatic Organisms / Q000737:chemistry / Q000378:metabolism; D001272:Atmosphere / Q000737:chemistry; D001835:Body Weight; D002113:Calcification, Physiologic; D002118:Calcium / Q000378:metabolism; D002119:Calcium Carbonate / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000032:analysis / Q000737:chemistry; D002255:Carbonic Acid / Q000032:analysis* / Q000737:chemistry; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry; D058087:Haptophyta / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009792:Oceans and Seas; D010140:Pacific Ocean; D010313:Partial Pressure; D010788:Photosynthesis; D010839:Phytoplankton / Q000737:chemistry / Q000378:metabolism*; D012623:Seawater / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide; D002255:Carbonic Acid; D002119:Calcium Carbonate; D002118:Calcium