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| Titel |
Sclerochronology of Holocene oyster shells (Crassostrea gigas) from the West Coast of Bohai Sea, China |
| VerfasserIn |
C. Fan, P. Koeniger, H. Wang, M. Frechen |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030062
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| Zusammenfassung |
| Sclerochronology, the study of periodic increments in skeletal organisms, can decipher the
life history and environmental records preserved in fossil shells. Although there have
been a number of studies that apply isotopic analyses to shells in open ocean and
fresh water, investigations for brackish environments are rare. One of the common
inhabitants in estuaries is the Crassostrea oyster. Kirby et al. (1998) demonstrated a close
correspondence between the ligamental increments of convex and concave bands and yearly
δ18O cycles; Andrus and Crowe (2000) found a close correspondence between
translucent growth bands on the cross-section of the hinge and yearly δ18O cycles.
They conclude that the morphological features on hinge and growth bands on the
cross-section are formed annually and can be used to determine accurately age and
growth rate in this species. However, Surge et al. (2001) could not find that these
morphologic features have seasonal significance in the C. virginica shells. Therefore,
these concave ridges are not reliable independent proxies of seasonality. These
studies were carried out with C. virginica shells; none was studied with nature C.
gigas, which was widely distributed along the Pacific coastal area. C. gigas has been
introduced from its native home to all over the world, ranging from North America to
Australia and Europe; it has become an important commercial harvest in many of these
places.
Buried Holocene oyster shells of C. gigas were sampled from a huge buried oyster reef on the
West of Bohai Sea, China. One of these shells was selected for high resolution
micro-sampling and stable isotope analyses testing the assumption that C. gigas ligamental
increments are annual in nature. We analyzed 236 consecutive samples from the shell to show
that morphologic features both on hinge and cross-section are annual by comparing them to
the δ18O profiles. We tested the assumption that the morphologic features of C.gigas are
delineated by convex tops and concave bottoms on hinge and corresponding translucent
growth bands on cross-section. The shell has 13.5 ligamental increments, based on
13.5 convex bands and 13 concave bottoms on hinge. Convex tops correspond to
δ18O minima (summers), whereas concave bottoms correspond to δ18O maxima,
which were formed during the low temperature of winter in the study area. We
demonstrate that the ligamental increments of convex tops, concave bottoms and
translucent growth bands in the studied C. gigas shell are suitable indicators of
annual growth increments. The life spans, growth rates, and the timing of death can
be determined from the ligament increments and isotope profiles of buried oyster
shells. |
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