南海不同种类砗磲内、外层壳体的δ13C变化特征及其对气候环境的指示意义

海洋生物碳酸盐（如珊瑚、贝壳、有孔虫等）的碳同位素（δ13C）通常受海水碳库δ13C和生物“生命效应”等因素共同影响，是研究海洋碳循环和气候变化的常用指标。砗磲是海洋中最大的双壳类，其碳酸盐壳体生长速率快，通常具有较清晰的年生长纹层，是一种优良高分辨率古气候研究载体。目前关于砗磲壳体δ13C的研究较少，δ13C影响因素及其在古气候古环境研究中的潜力也不清晰。本项目拟对南海西沙群岛3种6个砗磲的内、外层壳体进行高分辨率碳氧稳定同位素测试，研究不同取样路径下砗磲内、外层壳体δ13C的变化规律，查明砗磲δ13C在壳体内的分布特征；对比同种类不同个体、不同种类砗磲内、外层壳体δ13C的异同，分析砗磲内、外层壳体δ13C的种内和种间差异；将砗磲δ13C与气候环境指标进行对比，研究砗磲δ13C的环境指示意义，探讨利用砗磲δ13C重建海水碳库、气候变化等的潜力。

The marine biogenic carbonate carbon isotope composition (δ13C) is influenced by the ocean carbon pool δ13C and the “vital effect”, and thus, has been served as a proxy for the marine carbon cycle and the climate change. The marine bivalve, Tridacna spp., is the largest bivalve species. The carbonate shells of Tridacna grow at a fast rate and have clear annual bands, therefore have been treated as an excellent material for the high-resolution paleoclimate reconstruction. In consideration of a small number of the studies on Tridacna δ13C, the influencing factors of δ13C and its potential in paleoclimate reconstruction are not clear. In this study, the high-resolution oxygen and carbon isotopes of inner and outer shell layer δ13C of modern Tridacnae in different species from the South China Sea will be determined. The study firstly aims to figure out the intra-shell variations of Tridacnae δ13C by analyzing the inner and outer shell δ13C with different sampling paths. The within-species and inter-specific differences of the Tridacnae inner and outer shell layer δ13C will be investigated by comparing the shell δ13C of different individual and of different species. Furthermore, the environmental implications of Tridacnae δ13C will be tested by comparing the Tridacnae δ13C with the climatic and environmental indices.