Calcium isotope fractionation during coccolith formation in Emiliania huxleyi : Independence of growth and calcification rate
Langer, Gerald (Alfred Wegener Institute Foundation for Polar and Marine Research)
Gussone, Nikolaus (University of Bremen. Research Centre Ocean Margins)
Nehrke, Gernot (Alfred Wegener Institute Foundation for Polar and Marine Research)
Riebesell, Ulf (Leibniz Institute for Marine Sciences)
Eisenhauer, Anton (Leibniz Institute for Marine Sciences)
Thoms, Silke (Alfred Wegener Institute Foundation for Polar and Marine Research)

Fecha:	2007
Resumen:	Recently, calcium isotope fractionation in the coccolithophore Emiliania huxleyi was shown to exhibit a significant temperature dependency. An important subsequent question in this context is whether the observed fractionation patterns are caused by temperature itself or related growth rate changes. In order to separate growth and calcification rate effects from direct temperature effects, batch culture experiments with the coccolithophore E. huxleyi were conducted under varying light intensities. Despite large changes in cellular growth and calcification rates, calcium isotope fractionation remained constant. Independence of calcium isotope fractionation on growth and calcification was also obtained in two additional sets of experiments in which growth rates changed in response to varying calcium concentration and seawater salinity. These experiments also showed no direct effects of calcium concentration and salinity on calcium isotope fractionation. Values for calcium isotope fractionation of E. huxleyi coccoliths fell within a range of -1. 0 to -1. 6 (1000 lna), confirming earlier results. This range is similar to that observed in several foraminiferal species and coccolith oozes, suggesting a rather homogeneous calcium isotopic composition in marine biogenic calcite. Our data further show that the calcium isotope fractionation does not change with changing isotopic composition of seawater. This is a basic requirement for reconstructing the calcium isotopic composition of the ocean over time.
Ayudas:	European Commission 980409
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Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Calcification rate ; Calcium isotopes ; Emiliania huxleyi ; SDG 14 - Life Below Water
Publicado en:	Geochemistry, geophysics, geosystems, Vol. 8, Issue 5 (May 2007) , art. Q05007, ISSN 1525-2027

DOI: 10.1029/2006GC001422

11 p, 485.4 KB

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