寒武纪第二世—苗岭世生物礁中钙化蓝细菌多样性演变及环境响应研究

寒武纪生物礁在第二世─苗岭世过渡期从微生物─古杯礁转变为石海绵─微生物礁，这一转变是否与大气CO2升高形成温室气候引起浅海贫氧─低氧有关，成为争论的焦点。然而，寒武纪大气CO2水平由于缺乏合适的约束指标而没有得到有效评估。近年来实验条件及地质记录均证实，蓝细菌钙化作用受控于大气CO2水平，地史时期钙化蓝细菌多样性和丰度分布样式的重建，可对大气CO2水平进行半定量的约束。钙化蓝细菌是寒武纪生物礁重要的组成部分，但是缺乏系统的研究。本项目拟以第二世—苗岭世生物礁中的钙化蓝细菌为研究对象，通过我国10个代表性生物礁剖面的详细研究，并结合全球文献的调研和评估，揭示其中钙化蓝细菌的属种类型、生态特征、造礁作用、多样性与丰度时空分布，通过沉积环境、生态环境、钙化幕强弱等控制因素的分析，探讨其多样性和丰度演变对大气CO2含量变化的响应。这对寒武纪生物礁生态系统及后生动物演化的环境因素有重要的启示意义。

The Cambrian reef occurred a changeover during the Series 2-Miaolingian transition from microbial-archaeocyathid reef to lithistid sponge-microbial reef. Whether that this changeover of reef was related to the dysoxia-hypoxia in shallow marine environments under the greenhouse conditions due to high atmosphere CO2 level is under debated. However, there is no effective evaluation for the Cambrian atmosphere CO2 level due to the lack of applicable proxy at present. Recently, it is evidenced by experiment conditions and geologic record that the calcification in vivo cyanobacteria sheath is closely related to the level of atmosphere CO2. The reconstruction of the diversity and abundance distribution pattern of cyanobacteria during the geological time can provide semiquantitative constraint on the level of atmosphere CO2. Calcified cyanobacteria were important components of the Cambrian reefs. However, there is lack of systematic study for these calcified cyanobacteria. Therefore, special studies about calcified cyanobacteria fossils in reefs from Series 2-Miaolingian will be carried on. Based on detailed study for 10 reef sections distributed in China and investigation and evaluation for the global literatures, their taxons, palaeoecological characteristics, roles in reef building, and diversity and abundance distribution in spatial and temporal will be revealed. Based on analysis of controlling factors, such as depositional and ecological environments and calcification episode, the diversity and abundance evolutionary pattern of cyanobacteria and its response to the atmosphere CO2 level during the Series 2-Miaolingian will be investigated. This study is of great significance in exploring the paleoenvironment factors of the evolutionary pattern of reef ecosystem and metazoans during the Cambrian.