Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Gussone, N. Articles by Wefer, G. Search for Related Content GeoRef GeoRef Citation

Cellular calcium pathways and isotope fractionation in Emiliania huxleyi

¹ Research Centre Ocean Margins, University of Bremen, P.O. Box 330440, D-28334 Bremen, Germany
² Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
³ Leibniz Institute of Marine Sciences at the University of Kiel, Dienstgebäude Ostufer, Wischhofstraße 1-3, 24148 Kiel, Germany
⁴ Leibniz Institute of Marine Sciences at the University of Kiel, Dienstgebäude Westufer, Düsternbrooker Weg 20, 24105 Kiel, Germany
⁵ Research Centre Ocean Margins, University of Bremen, P.O. Box 330440, D-28334 Bremen, Germany

The marine calcifying algae Emiliania huxleyi (coccolitho phores) was grown in laboratory cultures under varying conditions with respect to the environmental parameters of temperature and carbonate ion concentration [CO₃^2–] concentration. The Ca isotope composition of E. huxleyi's coccoliths reveals new insights into fractionation processes during biomineralization. The temperature-dependent Ca isotope fractionation resembles previous calibrations of inorganic and biogenic calcite and aragonite. Unlike inorganically precipitated calcite, the [CO₃^2–] concentration of the medium has no significant effect on the Ca isotope composition of the coccoliths. These results indicate a decoupling of the chemical properties of the bulk medium and the calcifying vesicle. Cellular Ca pathways of E. huxleyi indicate that fractionation cannot occur at the crystal surface, as occurs during inorganic precipitation. The dominant processes leading to the observed Ca isotope fractionation pattern in E. huxleyi are most likely the dehydration of the Ca aquocomplex at the plasma membrane and the attachment of dissolved Ca to proteins of Ca channels. The independence of Ca isotope fractionation from [CO₃^2–] and the small temperature dependence of E. huxleyi are also important for defining the isotopic signature of the oceanic Ca sink. Since coccolithophores contribute to about half the global CaCO₃ production, a relatively uniform isotopic composition of the oceanic Ca sink is further supported.

Key Words: Emiliania huxleyi • calcium isotopes • coccolithophores • isotope fractionation