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| Titel |
Factors controlling carbon isotopic composition of land snail shells estimated from lab culturing experiment |
| VerfasserIn |
Naizhong Zhang, Keita Yamada, Naohiro Yoshida |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250086483
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| Publikation (Nr.) |
 EGU/EGU2014-359.pdf |
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| Zusammenfassung |
| Carbon isotopic composition (δ13C) of land snail shell carbonate is widely applied in
reconstructing the C3/C4 vegetation distribution of paleo-environment, which is considered
to reflect variations of some environmental parameters [1][2][3]. Land snail shell
carbon has three potential sources: diet, atmospheric CO2 and ingested carbonate
(limestone) [4]. However, their relative contributions to shell carbonate have not been
understood well yet [4][5][6][7][8]. More researches are necessary before we could
apply this tool in paleo-environment reconstruction, especially inter-lab culturing
experiment.
A kind of land snail species, Acusta despecta sieboldiana, was collected at Yokohama,
Japan and cultured under suitable environment to lay eggs. The second generations were
growing up from eggs to adults around 6-12 months at the temperature of 20°,
25° and 30°, respectively. All of the snails at 25° and 30° and most of those at
20° were fed by cabbage (C3 plant) during their life span while others were fed
by corn (C4 plant). To investigate the effect of ingested carbonate, some of them
were fed by Ca3(PO4)2 powder while others were fed by CaCO3 powder. δ13C of
shells were analyzed by an Isotope Ratio Mass Spectrometry (Thermo Finnigan
MAT 253); δ13C of food and snail tissue were measured by a Cavity Ring-Down
Spectroscopy (Picarro G1121-i). At the same time, δ13C of eggshell and new born snails
were analyzed by a Continuous Flow Isotope Ratio Mass Spectrometry (GasBench
II).
We confirmed that diet, atmospheric CO2 and ingested limestone could be important
sources controlling shell δ13C values. And the temperature could affect shell carbonate δ13C
values, too. A simple but credible frame was raised to discuss the mechanism of how each
possible source and environmental parameter could affect shell carbonate δ13C values based
on previous works [4][6][8] and this study. According to this frame and some reasonable
assumptions, we have estimated the contribution of different carbon sources for each snail
individual: to cabbage (C3 plant) fed groups, the contributions of diet, atmospheric
CO2 and ingested limestone vary in a range of 66~80%, 16~24% and 0~13%,
respectively. And to corn (C4 plant) fed groups, because of the possible food stress (lower
consumption ability of C4 plant), they vary in 56~64%, 18~20% and 16~26%,
respectively. We will discuss how these results could be consistent to the observations,
which suggests our calculations are suitable and believable. In addition, we will
discuss the carbon isotope fractionation during egg laying and hatching of land snails,
too.
[1] Goodfriend, 1992, Quaternary Sciences Reviews. 11, 665-685
[2] Yanes et al. 2009. Geochimica et Cosmochimica Acta, 73, 4077-4099
[3] Yanes et al., 2013. Palaeogeography, Plaeoclimatology, Palaeoecology, 378,
91-102
[4] Goodfriend and Hood, 1983. Radiocarbon, 25, 810-830
[5] Goodfriend and Stipp, 1983. Geology, 11, 575-577
[6] Stott, 2002. Earth and Planetary Science Letters, 195, 249-259
[7] Metref et al., 2003. Earth and Planetary Science Letters, 211, 381-393
[8] Romaniello et al., 2008. Quaternary Geochronology, 3, 68-75 |
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