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| Titel |
Growth increment periodicity in the shell of the razor clam Ensis directus using stable isotopes as a method to validate age |
| VerfasserIn |
J. F. M. F. Cardoso, G. Nieuwland, R. Witbaard, H. W. Veer, J. P. Machado |
| 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 ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-15), S.4741-4750 |
| Datensatznummer |
250018341
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| Publikation (Nr.) |
 copernicus.org/bg-10-4741-2013.pdf |
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| Zusammenfassung |
To evaluate the role of the razor clam Ensis directus in Dutch coastal waters,
understanding its population dynamics is important. As such, the age
structure of the population forms a key parameter. Accurate age
determination in bivalve shells is not always straightforward due to the
difficulty of interpreting externally visible growth lines. In the present
paper, we aimed at validating the seasonality in growth line formation using
visual techniques in combination with stable oxygen and carbon isotope
analyses (δ18O and δ13C).
High δ18O values in the shell coincided with growth marks on
the external surface of the valve and in acetate peels of the shell's cross
section. Most shell δ18O samples were assigned to the months from
June to September. From November to March no samples were
retrieved,
indicating that the shell did not grow. The lowest reconstructed temperature
(6.3 °C) suggests that ~ 6 °C may be the
threshold temperature for growth. Nevertheless, most of the reconstructed
values fell above 14.5 °C, indicating that growth occurred mainly
in the summer at relatively high temperatures. Shell δ13C
profiles followed a more or less seasonal cycle, but no direct relationship
could be made between δ13C values and annual growth lines.
Although counting external annual growth lines led to a correct estimation
of age and consequently of growth rates, we recommend analysing acetate
peels of cross sections to support the distinction between annual lines and
disturbance lines. |
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