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C and O isotopes in a deep-sea coral (Lophelia pertusa) related to skeletal microstructure
Blamart, D.; Rollion-Bard, C.; Cuif, J.P.; Juillet-Leclerc, A.; Lutringer, A.; van Weering, T.C.E.; Henriet, J.-P. (2005). C and O isotopes in a deep-sea coral (Lophelia pertusa) related to skeletal microstructure, in: Freiwald, A. et al. (Ed.) Cold-water corals and ecosystems. Erlangen Earth Conference Series, : pp. 1005-1020
In: Freiwald, A.; Roberts, J.M. (Ed.) (2005). Cold-water corals and ecosystems. Erlangen Earth Conference Series. Springer: Berlin. ISBN 3-540-24136. XXXII, 1243 pp., more
In: Freiwald, A. (Ed.) Erlangen Earth Conference Series. Springer: Berling, more

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Keywords
    Lophelia pertusa (Linnaeus, 1758) [WoRMS]; Marine
Author keywords
    Deep-sea corals; SIMS stable isotopes; isotopic disequilibrium; Lophelia pertusa

Authors  Top 
  • Blamart, D.
  • Rollion-Bard, C.
  • Cuif, J.P.
  • Juillet-Leclerc, A.
  • Lutringer, A.
  • van Weering, T.C.E., more
  • Henriet, J.-P., more

Abstract
    Lophelia pertusa is a deep-sea scleractinian coral (azooxanthellate) found on the continental margins of the major world oceans. Built of aragonite it can be precisely dated and measured for stable isotope composition (C-O) to reconstruct past oceanic conditions. However, the relation between stable isotope and skeleton microstructures, i.e. centres of calcification and surrounding fibres, is crucial for understanding the isotopic patterns. Values for d180 and d13C in Lophelia pertusa were determined at a micrometer scale using an ion microprobe (SIMS – Secondary Ion Mass Spectrometry). In this coral species, centres of calcification are large (50 µm) and arranged in lines. The centres of calcification have a restricted range of variation in d180 (-2.8 ± 0.3 ‰ (V-PDB)), and a larger range in d13C (14.3 to 10.9 ‰ (V-PDB)). Surrounding skeletal fibres exhibit large isotopic variation both for C and 0 (up to 12 ‰) and d13C and d180 are positively correlated. The C and 0 isotopic composition of the centres of calcification deviate from this linear trend at the lightest d180 values of the surrounding fibres. The fine-scaled variation of d180 is probably the result of two processes: (1) isotopic equilibrium calcification with at least 1 pH unit variation in the calcification fluid and (2) kinetic fractionation. The apparent d13C disequilibrium in Lophelia pertusa may be the result of mixing between depleted d13C metabolic CO2 (respiration) and DIC coming directly from seawater. This study underlines the close relationship between microstructure and stable isotopes in corals. This relationship must also be taken into consideration for major elements like Mg and trace elements (U-Sr-Ba) increasing the reliability of the geochemical tools used in paleoceanography.

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