Stable Carbon and Oxygen Isotopes in Shell Carbonates of modern Land Snails in China and Their Relation to Environment Variables.

Stable isotopes of land snail fossil shell carbonates (δ13Cshell and δ18Oshell) provide the opportunity to decipher paleodietary and paleoenvironmental changes. However, the environmental meanings of δ13Cshell and δ18Oshell remain elusive especially in the monsoonal climate region. To elucidate this, δ13Cshell and δ18Oshell of the two most common land snails in China, Cathaica and Bradybaena, were analyzed in this study. Results show that Bradybaena has a wider distribution than Cathaica and provides considerable potential for use in paleoenvironmental reconstruction. In addition, δ13Cshell of Bradybaena increases with altitude and temperature, decreases with mean annual precipitation, and reflects the isotopic signal of C3 plants. In contrast, Cathaica δ13Cshell documents a C3/C4 mixing signal and exhibits only a strong altitude effect. δ18Oshell of Bradybaena decreases with mean annual precipitation in the Indian monsoon and westerlies regions but increases with mean annual temperature in the East Asian monsoon region; as a strong correlation exists between the two variables, they could thus potentially be used to reconstruct paleotemperatures. However, uncertainties should be recognized due to the complexity of the land‐snails' ecophysiological responses to environmental changes. Cathaica has slightly lower δ18Oshell than Bradybaena, which suggests that the two land snails have different ecophysiological traits, and the δ18Oshell of Cathaica follows mean annual temperature in northeast China. This study lays a ground for explaining land snail stable isotopes in paleorecord in China and reasserts the importance of different ecophysiological traits of land snails in paleoclimatic research. Key Points: Stable isotopes and snail shell‐dimension studies suggest Bradybaena and Cathaica have different ecophysiological traitsδ13Cshell is a tracer of dietary vegetation and can be used to monitor rainfall in the region dominated by C3 plantsδ18Oshell of Bradybaena rises with temperature in East Asia monsoon region but declines with rainfall in Indian monsoon and westerlies areas [ABSTRACT FROM AUTHOR]