Inter- and intra-specific variability in δ13C and δ18O values of freshwater gastropod shells from Lake Lednica, western Poland

Abstract

This study focuses on the inter- and intra-specific variability in δ¹³C and δ¹⁸O values of shells and opercula of gastropods sampled live from the littoral zone of Lake Lednica, western Poland. The δ¹³C and δ¹⁸O values were measured in individual opercula of Bithynia tentaculata and in shells of Bithynia tentaculata, Gyraulus albus, Gyraulus crista, Lymnaea sp., Physa fontinalis, Radix auricularia, Theodoxus fluviatilis and Valvata cristata. The gastropods selected for the study are among the species most commonly found in European Quaternary lacustrine sediments. The carbon isotope composition of the gastropod shells was species-specific and the same order of species from the most to the least ¹³C-depleted was observed at all sites sampled. Differences in shell δ¹³C values between species were similar at all sampling sites, thus the factors influencing shell isotopic composition were interpreted as species-specific. The δ¹⁸O values of shells were similar in all the species investigated. Significant intra-specific variability in shell δ¹³C and δ¹⁸O values was observed not only within the populations of Lake Lednica, which can be explained by heterogeneity of δ¹³C DIC, δ¹⁸O water and water temperature between the sites where macrophytes with snails attached were sampled, but also between individuals sampled from restricted areas of the lake’s bottom. The latter points to the importance of factors related to the ontogeny of individual gastropods.