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| Titel |
High-resolution Li/Mg in cold-water coral skeletons: metabolic processes involved |
| VerfasserIn |
Vincent Mouchi, Quentin G. Crowley |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133094
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| Publikation (Nr.) |
 EGU/EGU2016-13672.pdf |
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| Zusammenfassung |
| Skeletal Li/Mg has recently been presented as a vital-effect-devoid proxy for seawater
temperature in both coastal and deep-sea corals. Bulk analyses on multiple scleractinian
species appear to follow an exponential law when plotted against measured seawater
temperature. In situ coral wall micro-analyses of cold-water species, however display a
variability that cannot be solely inferred to relate to seawater temperature and must be
influenced by some other processes. High-resolution (i.e. seasonal and infra-annual)
reconstruction of palaeotemperatures using Li/Mg from cold-water carbonates is therefore
questionable from our current understanding of these processes.
In order to address this uncertainty we present LA-ICP-MS elemental maps of Li, Mg, Sr
and Li/Mg from the skeleton of the cold-water coral Lophelia pertusa. Fluctuations in
concentration of these elements are present in both radial and longitudinal axes of growth,
implying a potential bias in absolute values measured, depending on the position of an
analytical transect.
Microstructures of L. pertusa skeletons can provide some insight into the potential use of
elemental ratios as proxies for fluctuations in environmental conditions. Observation of
growth patterns permits a micro-textural definition for calibration of geochemical fluctuations
occurring over the course of a year or more. Two cycles of geochemical fluctuations are
observed per year, meaning that seasonal fluctuations cannot be solely responsible for these
variations. Moreover, high elemental concentrations in the coral wall correspond to large
growth increments, suggesting that certain elemental incorporation is dominantly ruled by
growth rates and thus kinetic processes. Growth rate fluctuations, which appear to occur
twice per year, are likely caused by interaction of physiological mechanisms and
local physicochemical conditions. Specifically for L. pertusa skeletons, further
characterization and discreet separation of these interactions need to be addressed
prior to interpretation of elemental fluctuations as reliable environmental proxies. |
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