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| Titel |
Light and temperature effects on δ11B and B / Ca ratios of the zooxanthellate coral Acropora sp.: results from culturing experiments |
| VerfasserIn |
D. Dissard, E. Douville, S. Reynaud, A. Juillet-Leclerc, P. Montagna, P. Louvat, M. McCulloch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-20), S.4589-4605 |
| Datensatznummer |
250007398
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| Publikation (Nr.) |
 copernicus.org/bg-9-4589-2012.pdf |
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| Zusammenfassung |
| The boron isotopic composition (δ11B) of marine carbonates (e.g.
corals) is increasingly utilised as a proxy for paleo-pH, with the strong
correlation between δ11B of marine calcifiers and seawater pH now
well documented. However, the potential roles of other environmental
parameters that may also influence both the boron isotopic composition and
boron concentration into coral aragonite are poorly known. To overcome this,
the tropical scleractinian coral Acropora sp. was cultured under 3
different temperatures (22, 25 and 28 °C) and two light conditions
(200 and 400 μmol photon m−2 s−1). The
δ11B indicates an increase in internal pH that is dependent on
the light conditions. Changes in light intensities from 200 to
400 μmol photon m−2 s−1 seem to indicate an apparent
decrease in pH at the site of calcification, contrary to what is expected in
most models of light-enhanced calcification. Thus, variations in light
conditions chosen to mimic average annual variations of the natural
environments where Acropora sp. colonies can be found could bias pH
reconstructions by about 0.05 units. For both light conditions, a significant
impact of temperature on δ11B can be observed between 22 and
25 °C, corresponding to an increase of about 0.02 pH-units, while no
further δ11B increase can be observed from 25 to 28 °C.
This non-linear temperature effect complicates the determination of a
correction factor. B / Ca ratios decrease with increasing light, consistent
with the decrease in pH at the site of calcification under enhanced light
intensities. When all the other parameters are constant, boron concentrations
in Acropora sp. increase with increasing temperatures and increasing
carbonate ion concentrations. These observations contradict previous studies
where B / Ca in corals was found to vary inversely with temperature,
suggesting that the controlling factors driving boron concentrations have not
yet been adequately identified and might be influenced by other environmental
variables and/or species-specific responses. |
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