Variation in delta13C and delta15N among different tissues of three estuarine bivalves: Implications for dietary reconstructions
2006
Yokoyama, H.(National Research Inst. of Aquaculture, Minami-Ise, Mie (Japan)) | Ishihi, Y.
The stable isotope approach to dietary reconstructions is based on the consistent isotopic fractionation between diet and consumer. Despite the rapidly increasing use of stable isotopes in studies on bivalves, classical fractionation values (0-1permille for deltasup(13)C and 3-4permille for deltasup(15)N) are used in the literature irrespective of the tissue analyzed and of the sample preparation method. We measured deltasup(13)C and deltasup(15)N for lipid-removed and lipid-containing tissues (adductor muscle, foot, mantle lobe, siphon, labial palp, gill lameila, midgut gland and male and female gonad) of three suspension feeding bivalves (Crassostrea gigas, Cyclina sinensis and Ruditapes philippinarum) to provide an essential calibration for the diet-tissue fractionation. There were similar tissue-specific patterns in the deltasup(13)C and deltasup(15)N, which rank adductor muscleother tissuesmidgut gland or female gonad. Removal of lipids raised the deltasup(13)C and deltasup(15)N for all tissues of the three species. Acid treatment of the total soft tissues of R. philippinarum had no significant effects on the isotopic compositions. Diet-tissue fractionations for R. philippinarum were estimated based on the known fractionation values for the lipid-containing total soft tissues. Lipid removal and associated rinsing raised not only the sup(13)C fractionation by 0.4-1.5permille but also the, sup(15)N fractionation by 0-0.8permille, resulting in large fractionation values outside of the range of currently accepted sup(13)C and sup(15)N fractionation. The present study demonstrates that isotopic analyses are affected by the choice of tissue type and sample preparation method.
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