Precipitation δ18O paced the seasonal δ18O variations of terrestrial snail body water and shells in the East Asian monsoon region

High‐Resolution Intrashell Oxygen Isotope Studies of Cathaica fasciola and Bradybaena ravida Land Snails and Their Environmental Implications

“…All the δ 18 O s sequences for the nonadult C. fasciola shells sampled in August and September showed similar variations, that is, the δ 18 O s values are more negative for the shell mouth and apex parts than for those in between (Figure 2). According to our previous work and the abovementioned results, shells with positive δ 18 O s values were likely formed in spring, and the apex parts with negative δ 18 O s values were likely formed in the last summer (Zong et al, 2023). Moreover, when drawn on the same y-axis, the amplitudes of variation in δ 18 O s values are similar for shells collected on the same dates (Figures S2a-S2c in Supporting Information S1).…”

“…In other words, the decrease in δ 18 O P accompanied by high temperature in summer will cause negative δ 18 O s values in snail shells, and this will occur in the opposite direction in spring. Given the results of previous works, we suggest that δ 18 O P may still dominate the changes in δ 18 O s and Δ 18 O (maximum minus minimum δ 18 O s values) in snail shells on the seasonal scale (Ghosh et al, 2017;Goodfriend et al, 1989;Lécolle, 1985;Prendergast et al, 2015;Sun et al, 2009;Zong et al, 2023).…”

“…In addition, Yapp (1979) reported that the theoretically calculated δ 18 O BW values are more enriched than δ 18 O P values. This difference is attributed to the evaporative enrichment of recent work further demonstrated that δ 18 O P is the first-order control on the seasonal variations in δ 18 O BW and δ 18 O s , while RH plays a role during nonprecipitation periods (Zong et al, 2023). This provides direct evidence to reconcile the different interpretations of δ 18 O s in previous studies.…”

“…This difference is attributed to the evaporative enrichment of 18 O in snail body water, which appears to be correlated with the reciprocal of the local RH (Yapp, 1979). Our recent work further demonstrated that δ 18 O P is the first‐order control on the seasonal variations in δ 18 O BW and δ 18 O s , while RH plays a role during nonprecipitation periods (Zong et al., 2023). This provides direct evidence to reconcile the different interpretations of δ 18 O s in previous studies.…”

“…The high-resolution intrashell δ 18 O s data from different species presented here may serve as a powerful tool for exploring this issue. Microenvironments (e.g., temperature, RH) fundamentally affect the oxygen isotope composition of snail body water, which is subsequently transferred into snail shells, although precipitation is the ultimate water source for different species (Zong et al, 2023). According to the discussion in Section 4.3, the intrashell δ 18 O s sequences clearly reflected the microenvironmental differences between C. fasciola and B. ravida species.…”