Clumped Isotopic Characteristics In The Modern Aquatic Gastropod Radix And Temperature Reconstruction

Lake shells are sensitive to regional climate change,and are important carriers for palaeoclimate research.Among them,the shells of the gastropoda Radix(Lymnaeidae)are high resolution materials for climate reconstruction that can record environmental and climate change information at seasonal and even monthly scales.Carbonate clumped isotope as a new temperature measurement technology is an important tool for the determination of palaeotemperature and has been successfully applied to palaeotemperature reconstruction.However,the relationship between growth of biological shell and environment is more complex,it is not clear whether there are differences in the clumped isotopic characteristics of the same species in different environmental gradients and life cycles,and whether there are individual differences in the temperature reflected by different shells in the same lake.Therefore,further understanding of clumped isotopic characteristics of biological shells is of great significance to improve the accuracy of temperature reconstruction using clumped isotope of lake biological shells.This study take the modern Radix shell which sampling from the Tibaten plateau lake(Namtso,Yamdrok and Bangong Co),Yunnan lakes(Fuxian lake and Yilong lake)and the Tai lake as the research object,based on the stable isotope center clumped isotope laboratory of Fujian normal university,measure the stable carbon and oxygen isotope and clumped isotope of varying size shell from different lakes to obtain the environmental and temperature information of the shells.Here are main conclusion:1.The stable carbon and oxygen isotopes of the shell of Radix mainly reflect the?¹³C and?¹⁸O in lake.The?¹³C and?¹⁸O of the shell are gradually more positive with the increase of the altitude.2.In this study,the isotopic information of large,medium and small shells is closely related to their life cycle.There is a phenomenon that the size of shell is smaller,the?¹³C and?¹⁸O of shell more positive.The annual carbon and oxygen isotope variation of Radix showed a U-shaped pattern.In this paper,we infer that small group of shell growth mainly in August to Octobor,the life cycle is short,is located at the right end of"U"type curve.The main growth period of the large group is summer or the whole year,which is in the middle of the"U"curve,while the middle group is between small and large group.3.There was a positive correlation between T₄₇(the temperature calculated by?₄₇of shells)of shell and the average annual water temperature.The water temperature recorded by the shell was between the average annual water temperature and the average water temperature in warm season.The higher the altitude was,the T₄₇ of shell was closer to the summer water temperature.By comparing T₄₇ of shell with water temperature,we detrmine the main growing season of each lake shell is from April to October.Due to the short growth period,the water temperature recorded by small shells is only part of the time,so T₄₇ of shell fluctuates greatly.On the contrary,the clumped isotope temperature of the large group is the most stable.4.Based on the average T₄₇ of each lake shell,the reconstructed average annual temperature is similar to the actual temperature of each lake,and the temperature difference is between 0.4-3.4?by using the transfer function of water temperature to average annual air temperature from April to October by Hren et al.(2012).Based on the large,medium and small shells of each lake,the reconstructed average annual temperature by using the same water-temperature transfer function shows that the reconstructed temperature with large group is more accurate and reliable.Therefore,it is suggested to reconstruct the temperature with large shells(shell height>1.6 cm).