Effect of environmental conditions and skeletal ultrastructure on the Li isotopic composition of scleractinian corals

• Published in: Earth and Planetary Science Letters
• Main Authors: Rollion-Bard, Claire, Vigier, Nathalie, Meibom, Anders, Blamart, Dominique, Reynaud, Stephanie, Rodolfo-Metalpa, Riccardo, Martin, Sophie, Gattuso, Jean-Pierre
• Other Authors: Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'océanographie de Villefranche (LOV), Observatoire océanologique de Villefranche-sur-mer (OOVM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Museum of Natural History, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Biocomplexité des écosystèmes coralliens de l'Indo-Pacifique (CoReUS2), Institut de Recherche pour le Développement (IRD), Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Marine Environment Laboratories Monaco (IAEA-MEL), International Atomic Energy Agency Vienna (IAEA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2009
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Lophelia pertusa
• Online Access: https://hal.archives-ouvertes.fr/hal-03505012; https://doi.org/10.1016/j.epsl.2009.06.015

The lithium isotope compositions ((7)Li/(6)Li) and Li/Ca ratios of shallow-water and deep-sea corals (Porites lutea, Cladocora caespitosa, Lophelia pertusa and Desmophyllum cristagalli) were measured using a Cameca ims 1270 ion microprobe. The two C. caespitosa samples were grown under controlled conditions at CO(2) partial pressures (pCO(2)) of 416 +/- 29 mu atm and 729 +/- 30 mu atm, respectively. In situ analyses show that all samples are isotopically homogeneous (within analytical precision, +/- 1.1 parts per thousand, 1 sigma) and display significantly lower delta(7)Li values relative to seawater. indicating a significant isotope fractionation during aragonite formation. In contrast to all other elements analysed so far, there is no relationship between the Li isotopic compositions and the skeletal ultrastructure. However, Li/Ca does show variation correlated with ultrastructure, albeit with significant differences between species. This implies that the bio mineralization mechanisms, which are supposed to be different for the different skeletal components, do not influence the Li isotopic composition in corals. In particular, the model of Rayleigh fractionation in a semi-enclosed calcifying fluid is incompatible with the homogeneity of the Li isotope compositions at the micrometer scale We also. show that changes in pCO(2) (and pH) do not significantly affect the Li isotope signature. Nevertheless, a small but significant and systematic difference in Li isotopic composition is observed between deep-sea azooxanthellate and shallow-water zooxanthellate corals. The lack of dependence on pH and pCO(2) and on skeletal ultrastructure indicates that the U isotopic signature of corals could be used as a proxy for reconstructing the paleo-delta(7)Li of seawater and, potentially, for deconvolving past continental weathering rates. (C) 2009 Elsevier B.V. All rights reserved.