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| Titel |
A preliminary study of iron isotope fractionation in marine invertebrates (chitons, Mollusca) in near-shore environments |
| VerfasserIn |
S. Emmanuel, J. A. Schuessler, J. Vinther, A. Matthews, F. von Blanckenburg |
| 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. 19 ; Nr. 11, no. 19 (2014-10-08), S.5493-5502 |
| Datensatznummer |
250117630
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| Publikation (Nr.) |
 copernicus.org/bg-11-5493-2014.pdf |
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| Zusammenfassung |
Chitons (Mollusca) are marine invertebrates that produce radulae (teeth or
rasping tongues) containing high concentrations of biomineralized magnetite
and other iron-bearing minerals. As Fe isotope signatures are influenced by
redox processes and biological fractionation, Fe isotopes in chiton radulae
might be expected to provide an effective tracer of ambient oceanic
conditions and biogeochemical cycling. Here, in a pilot study to measure Fe
isotopes in marine invertebrates, we examine Fe isotopes in modern marine
chiton radulae collected from different locations in the Atlantic and Pacific
oceans to assess the range of isotopic values, and to test whether or not the
isotopic signatures reflect seawater values.
Values of δ56Fe (relative to IRMM-014) in chiton teeth range from
−1.90 to 0.00 ‰ (±0.05‰ (2σ) uncertainty in
δ56Fe), probably reflecting a combination of geographical control
and biological fractionation processes. Comparison with published local
surface seawater Fe isotope data shows a consistent negative offset of chiton
teeth Fe isotope compositions relative to seawater. Strikingly, two different
species from the same locality in the North Pacific (Puget Sound, Washington,
USA) have distinct isotopic signatures. Tonicella lineata, which feeds on red
algae in the sublittoral zone, has a mean δ56Fe of
−0.65 ± 0.26‰ (2σ, 3 specimens), while Mopalia
muscosa, which feeds on both green and red algae in the eulittoral zone,
shows lighter isotopic values with a mean δ56Fe of
−1.47 ± 0.98‰ (2σ, 5 specimens). Three possible
pathways are proposed to account for the different isotopic signatures: (i)
physiologically controlled processes within the chitons that lead to species-dependent fractionation; (ii) diet-controlled variability due to different Fe
isotope fractionation in the red and green algal food sources; and (iii)
environmentally controlled fractionation that causes variation in the
isotopic signatures of bioavailable Fe in the different tidal regions. Our
preliminary results suggest that while chitons are not simple recorders of
the ambient seawater Fe isotopic signature, Fe isotopes provide valuable
information concerning Fe biogeochemical cycling in near-shore environments,
and may potentially be used to probe sources of Fe recorded in different
organisms. |
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