Response Of Stable Isotope Changes To Climate And Environment In Meng 's Snail

For lake creatures and their shells, the response on the lake environment change is sensitive and rapid, contains annual or seasonal climate change information, which has become one of the most popular research topic in paleoenvironment and paleolake area. The composition feature of creature shell isotope is an effective indicator to recognize paleoenvironment and paleoclimate, which has been widely used in lake research. For studying the environment feature represented by isotope,it’s of great significance to choose a same kind of creature shell.Taking the lakes in central Yunnan province, including Dianchi Lake, Fuxian Lake, Xingyun Lake, Qilu lake and Yilong lake as research object, through the isotope composition measurement of Margarya mansuyi Dautzenberg et H. Fischer shells and its living lake water, combined with multivariate analysis methods, we discussed the influence which food has on the biological shell stable isotope fractionation and elements changes, and analyzed the relationship between the isotopic composition of modern biological shell and the water quality parameters of lake, thus discussed the response mechanism which Margarya mansuyi Dautzenberg et H. Fischer shells respond on regional climate environmental indicators, such as temperature, precipitation. In this paper, we have the following conclusions:1 The result show that the oxygen isotopic composition change of lake water is related with the composition of precipitation isotope and temperature. For Margarya mansuyi Dautzenberg et H. Fischer shells in the lake of central Yunnan, the values ofδ¹³C and δ¹⁸O is positive in summer and passive in winter, by analysis of growing layers, we can get, margarya layer > body margarya layer >shells layer. The stable isotopic difference of Margarya mansuyi Dautzenberg et H. Fischer shells between Yilong lake and Qilu lake is influenced comprehensively by the climate, water environment, food, etc.2 The influence which shells stable isotope put on their living water environment is embodied in the response of Margarya mansuyi Dautzenberg et H. Fischer shellsδ¹³C isotope to conductivity, salinity and other environmental information. There exists obvious negative phase relationship between them. But it doesn’t response obviously to such parameter index of water environment as water temperature, pH,water depth, dissolved oxygen, chlorophyll, etc. We don’t find Margarya mansuyi Dautzenberg et H. Fischer shells stable oxygen isotope has good reflect and record on the indicators of its lake environment parameters.3 The impact of Food（i.e., Aquatic plants stable isotopes） on the Margarya mansuyi Dautzenberg et H. Fischer shells stable isotope is mainly embodied in the influence which aquatic plants δ¹³C put on the Margarya mansuyi Dautzenberg et H.Fischer shells oxygen isotopes, the influence which aquatic plants δ¹⁵N put on the Margarya mansuyi Dautzenberg et H. Fischer shells oxygen isotopes and the influence which C/N ratio put on the Margarya mansuyi Dautzenberg et H. Fischer shells carbon and oxygen isotopes. Wet Ratio of aquatic plants, the carbon content and the nitrogen content doesn’t have obvious correlation with Margarya mansuyi Dautzenberg et H. Fischer shells isotope. Thus, it shows these index doesn’t influence much on creature shells.4 Regional precipitation and the composition of precipitation isotopic influence the compostion and the fractionation of lake water isotope directly, Margarya mansuyi Dautzenberg et H. Fischer shells respond sensitively and are highly relevant to aquatic plants stable isotope; on the other hand, temperature controls the evaporation balance of the water and lake water level by adjusting the water cycle of lake basin. When temperature rises, the lake water collects heavy isotopes.