Isotopic evidence for dew uptake by land snails from Bayesian modeling of body water δD and δ18O

Abstract

Land snail shells serve as valuable paleoclimate archives, with their isotopic compositions recording past changes in regional ecology and hydrology. To quantitatively reconstruct paleoclimate parameters such as the oxygen isotopic composition of precipitation (δ¹⁸O_p), a flux balance model targeting snail body fluid was developed by Balakrishnan and Yapp (2004). However, previous applications of the flux balance model based on modern observations have consistently reported offsets between modeled and observed δ¹⁸O_p values. In this study, I re-evaluated the model input parameters using a published high-resolution dataset and Bayesian inversion to refine estimates of the isotopic compositions of the snail's drinking water (δ¹⁸O_in, δD_in). The modeled δ¹⁸O_in and δD_in plot above the local meteoric water line, indicating substantial contributions of atmospheric vapor to the snail body water via dew uptake. Assuming that the ambient water vapor forms through evaporation of meteoric water, the updated flux balance model suggested that dew accounts for up to ∼50 % of snail's water intake in the study site. This finding highlights a critical oversight in previous paleoclimate reconstructions that ignored dew uptake, potentially leading to underestimation of δ¹⁸O_p.