The Ostracod Clumped-Isotope Thermometer: A Novel Tool to Accurately Quantify Continental Climate Changes

This study presents a methodological advancement in the field of clumped-isotope ( increment 47) thermometry, specifically tailored for application to freshwater ostracods. The novel ostracod clumped isotope approach enables quantitative temperature and hydrological reconstruction in lacustrine records. The relationship between increment 47 and the temperature at which ostracod shell mineralized is determined by measuring increment 47 on different species grown under controlled temperatures, ranging from 4 +/- 0.8 to 23 +/- 0.5oC. The excellent agreement between the presented increment 47 ostracod data and the monitored temperatures confirms that increment 47 can be applied to ostracod shells and that a vital effect is absent outside the uncertainty of measurements. Results are consistent with the carbonate clumped-isotope unified calibration (Anderson et al., 2021, ), therefore, an ostracod-specific calibration is not needed. The ostracod clumped-isotope thermometer represents a powerful tool for terrestrial paleoclimate studies all around the world, as lakes and ostracods are found in all climatic belts. In the framework of global warming, the reconstruction of past climatic conditions is important to understand the future evolution of climate and its impact. Lake sediments can be used as archives to quantify these effects. This study presents a novel paleo-thermometer based on the application of clumped-isotope technique (i.e., measurement of the number of 13C-18O bonds in carbonate minerals that depends on the temperature of carbonate precipitation) on carbonatic microcrustacea, named ostracods that commonly live in lakes. By using ostracods that formed their shells at known temperatures, we demonstrate that they can be easily used to reconstruct water temperature and hydrological conditions (precipitation/evaporation). The ostracod clumped-isotope thermometer represents a powerful tool for terrestrial paleoclimate studies around the world, as lakes and ostracods are located in all climatic belts. increment 47-ostracod signal accurately records the shell calcification temperature increment 47-ostracod signal is not affected by the so called "vital effect" The unified calibration of Anderson et al. (2021) can be used to convert the increment 47-ostracod signal into accurate temperatures