Negligible temperature dependence of calcium isotope fractionation in 12 species of planktonic foraminifera

• Published in: Earth and Planetary Science Letters
• Main Authors: Sime, N. G., de La Rocha, Christina, L., Galy, A.
• Other Authors: Department of Earth Sciences University of Cambridge, University of Cambridge UK (CAM), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences Cambridge, UK
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Indian; North Atlantic; Planktonic foraminifera
• Online Access: https://hal.univ-brest.fr/hal-00660828; https://doi.org/10.1016/j.epsl.2005.01.011

International audience The influence of temperature on calcium (Ca) isotope fractionation during biomineralization was investigated through the paired analyses of d44/42Ca (via MC-ICP-MS) and d18O on the calcite tests of 12 species of planktonic foraminifera from coretop sediments. Samples were collected from a suite of box-cores from sites between 608N and 308S in the North Atlantic and West Indian oceans, spanning a range in sea surface temperature of 9-27 8C. The d44/42CaSRM915a of the samples ranged from +0.21x to +0.81x over a range in the d18OVPDB of the foraminiferal calcite of between 2.3x and +2.1x. The bulk of the species investigated produced calcite with an average calcite-seawater Ca enrichment factor (e) of 0.65F0.08x (n=45). The globorotaliid species and a single Globigerina bulloides sample were confined to the upper 0.4x of the observed range in d44/42Ca values, with the globorotaliids displaying a lesser degree of fractionation of 0.56F0.23x (n=15), possibly as a result of physiological or metabolic processes such as the production of calcite crusts at depth, leading to the depletion of internal stores of Ca. No significant correlation between temperature and Ca enrichment factor was observed in any of the 12 species of foraminifera investigated. The influence of temperature on e was close to zero for the combined non-globorotaliid species, 0.07F0.10 K (e versus 1000/K; 0.0008F0.0012x 8C 1). The results suggest that the theoretically expected relationship between the Ca enrichment factor and temperature can be obscured by, as yet, unquantified metabolic and physiological processes in nature. These processes are particularly relevant to the globorotaliid species and G. bulloides in this core-top study. Consequently, their effects must be better understood before laboratory-determined temperature calibrations can be applied to downcore material with confidence. Provided that the effects of metabolic and physiological processes on e remain constant through time, Orbulina universa, ...