海草及其根际微生物协同适应西沙岛礁寡营养环境的生态策略研究

西沙岛礁是我国最完整最具有代表性的大洋型岛礁，在生物多样性保护和生态资源供给方面发挥着重要作用。海草能够促进珊瑚的钙化、减缓珊瑚礁的衰退并加速其生态系统的恢复。本项目拟从海草及其根际微生物同步响应和适应的角度出发，研究海草及其根际微生物协同适应西沙岛礁寡营养环境的生态策略。通过将野外监测和模拟实验相结合，应用基因芯片、高通量测序和荧光定量等技术对根际微生物的群落结构与功能进行研究，探讨海草生长状态与根际微生物的关系并识别对海草适应岛礁环境起关键作用的微生物类群；利用氮同位素技术明确生物固氮对海草的氮素营养贡献及其在海草体内的分配特性；开展氮添加实验，分析海草在生理生态水平上和氮循环重要的微生物类群(固氮、氨氧化和反硝化)在DNA、RNA水平的同步响应与适应特征，揭示海草及其根际微生物的氮素反馈调节机制。本研究将对我国南海自然珊瑚岛礁和人工吹填岛礁的稳固发展和生态功能的维持有重要的指导意义。

Xisha Islands is the complete and most distinctive ecosystem, which play an crucial role in protecting biodiversity and ecological resources. Seagrass can promote the calcification of coral reef, slow the degradation of coral reef and accelerate the restoration coral reef ecosystems. This project aims at investigating the ecological coadaptation strategies of Seagrass and its rhizospheric microbes in tropical Coral Reef Islands basing on the prospective of the synchronous and real-time responses and adaptation seagrasses and their rhizospheric microbes. This study consists of both field investigation and simulation experiment. Molecular techniques including Geochip, high-throughput sequencing and real-time PCR are involved to investigate exploring the relationship between the growth status of seagrasses and structure and function of rhizospheric microbe community, and identifying the microbial species which exert the crucial role in helping seagrasses living in the coral reef ecosystems. Result of the nitrogen isotope experiment will reveal the contribution of fixed nitrogen by microbe to the seagrasses growth and their allocation in plants. One of the most important aspects of this project is to study the synchronous and real-time response of the seagrasses and their rhizospheric microbes by nitrogen-addtion experiment. The physiological and ecological parameters of seagrass will be measured. At the same time, the abundance, diversity and real-time expression of key enzymes (nitrogen fixation, ammonia oxidation and denitrification) involved in nitrogen cycles at DNA and RNA level will be analyzed. It will elucidate the nitrogen feedback regulation mechanism of seagrasses and their rhizospheric microorganisms.　The results of this project will contribute to sustain the stable development and ecological function of both the natural and artificial coral reef Islands in South China Sea.