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| Titel |
Fluctuations of sulfate, S-bearing amino acids and magnesium in a giant clam shell |
| VerfasserIn |
T. Yoshimura, Y. Tamenori, H. Kawahata, A. Suzuki |
| 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 ; 11, no. 14 ; Nr. 11, no. 14 (2014-07-24), S.3881-3886 |
| Datensatznummer |
250117523
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| Publikation (Nr.) |
 copernicus.org/bg-11-3881-2014.pdf |
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| Zusammenfassung |
| We used micro-X-ray fluorescence combined with X-ray photoabsorption
spectroscopy to investigate speciation-specific sulfur profiles in the inner
shell layer of a giant clam (Hippopus hippopus). The sulfate,
S-bearing amino acids, and total sulfur profiles indicated that inorganic
sulfate was the dominant component in the shell of this bivalve. Sulfur
profiles in the inner shell layer showed clear annual fluctuations that
varied by more than one order of magnitude, from < 50 to 1420 ppm, and
sulfate and total sulfur maxima became higher with age, whereas no
ontogenetic trend was noticeable in the profile of S-bearing amino acids. A
change in the carbonate ion concentration in the calcifying fluid would
suggest that an ontogenetic increase in the relative activity of sulfate ions
to carbonate ions in the calcifying fluid affects sulfate concentrations in
the shells. These results suggest that trace sulfur profiles in the shell of
the giant clam may reflect both cyclic shell growth related to environmental
factors such as insolation and temperature and ontogenetic changes of the
calcifying fluid chemistry mediated by physiological processes. The observed
S profile implies a clear change in calcifying fluid chemistry towards less
alkaline condition with age. Magnesium fluctuations suggested that Mg was
incorporated into the shells at high growth rates during warm seasons. The
spectrum of Mg K-edge X-ray absorption near edge structure (XANES) and comparison of Mg and S-bearing amino acids
profiles indicated that a pronounced effect of the organic fraction or
disordered phases were observed in aragonitic shell of H. hippopus
rather than regulated substitution into the aragonite crystal lattice. |
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