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Montagna P., McCulloch M., Douville E., Correa M. L., Trotter J., Rodolfo-Metalpa Riccardo, Dissard Delphine, Ferrier-Pages C., Frank N., Freiwald A., Goldstein S., Mazzoli C., Reynaud S., Ruggeberg A., Russo S., Taviani M. (2014). Li/Mg systematics in scleractinian corals : calibration of the thermometer. Geochimica et Cosmochimica Acta, 132, 288-310. ISSN 0016-7037

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Lien direct chez l'éditeur doi:10.1016/j.gca.2014.02.005

Titre
Li/Mg systematics in scleractinian corals : calibration of the thermometer
Année de publication2014
Type de documentArticle référencé dans le Web of Science WOS:000334832100017
AuteursMontagna P., McCulloch M., Douville E., Correa M. L., Trotter J., Rodolfo-Metalpa Riccardo, Dissard Delphine, Ferrier-Pages C., Frank N., Freiwald A., Goldstein S., Mazzoli C., Reynaud S., Ruggeberg A., Russo S., Taviani M.
SourceGeochimica et Cosmochimica Acta, 2014, 132, p. 288-310. ISSN 0016-7037
RésuméWe show that the Li/Mg systematics of a large suite of aragonitic coral skeletons, representing a wide range of species inhabiting disparate environments, provides a robust proxy for ambient seawater temperature. The corals encompass both zooxanthellate and azooxanthellate species (Acropora sp., Porites sp., Cladocora caespitosa, Lophelia pertusa, Madrepora oculata and Flabellum impensum) collected from shallow, intermediate, and deep-water habitats, as well as specimens cultured in tanks under temperature-controlled conditions. The Li/Mg ratios observed in corals from these diverse tropical, temperate, and deep-water environments are shown to be highly correlated with temperature, giving an exponential temperature relationship of: Li/Mg (mmol/mol) = 5.41 exp (-0.049 * T) (r(2) = 0.975, n = 49). Based on the standard error of the Li/Mg versus temperature correlation, we obtain a typical precision of +/- 0.9 degrees C for the wide range of species analysed, similar or better than that of other less robust coral temperature proxies such as Sr/Ca ratios. The robustness and species independent character of the Li/Mg temperature proxy is shown to be the result of the normalization of Li to Mg, effectively eliminating the precipitation efficiency component such that temperature remains as the main controller of coral Li/Mg compositions. This is inferred from analysis of corresponding Li/Ca and Mg/Ca ratios with both ratios showing strong microstructure-related co-variations between the fibrous aragonite and centres of calcification, a characteristic that we attribute to varying physiological controls on growth rate. Furthermore, Li/Ca ratios show an offset between more rapidly growing zooxanthellate and azooxanthellate corals, and hence only an approximately inverse relationship to seawater temperature. Mg/Ca ratios show very strong physiological controls on growth rate but no significant dependence with temperature, except possibly for Acropora sp. and Porites sp. A strong positive correlation is nevertheless found between Li/Ca and Mg/Ca ratios at similar temperatures, indicating that both Li and Mg are subject to control by similar growth mechanisms, specifically the mass fraction of aragonite precipitated during calcification, which is shown to be consistent with a Rayleigh-based elemental fractionation model. The highly coherent array defined by Li/Mg versus temperature is thus largely independent of coral calcification mechanisms, with the strong temperature dependence reflecting the greater sensitivity of the Kd Li/Ca partition coefficient relative to Kd Mg/Ca. Accordingly, Li/Mg ratios exhibit a highly coherent exponential correlation with temperature, thereby providing a more robust tool for reconstructing paleo-seawater temperatures.
Plan de classementLimnologie physique / Océanographie physique [032] ; Ecologie, systèmes aquatiques [036]
Descr. géo.MEDITERRANEE ; ATLANTIQUE ; PACIFIQUE ; OCEAN AUSTRAL
LocalisationFonds IRD [F B010061965]
Identifiant IRDfdi:010061965
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010061965

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