温度胁迫对珊瑚生态系统固氮的影响——现生环境与历史记录反演

Coral reefs are referred as “oases” in an otherwise oceanic desert due to their high productivity and biodiversity. Nitrogen fixation provides the "new" N for the oligotrophic coral reef ecosystem and thus plays an important role in flourishing productivity. Recent evidence shows diazotrophic community in coral system changed significantly under elevating ocean temperature in short time, which in turn could affect nutrient condition and health condition of coral systems. However, the variation of nitrogen rate and long-term adaptation of diazotroph under thermal stress remains unclear. By using isotope labeling techniques and temperature control culture in mesocosm system, this study aims to quantify change of nitrogen fixation rate of coral reef system under thermal stress. Meanwhile, molecular biological techniques are also applied to show responses of different diazotroph in coral reef ecosystems. Results are expected to disclose the short-term response of nitrogen fixing under thermal stress. Further, by combining temperature records of giant clam and its shell-bound nitrogen isotope signals, this study also tried to build potential relationship between temperature and N-fixation in coral reefs. Results are expected to depict the long-term adaptation and mechanism of N-fixation under different thermal conditions for lasts decades and to provide scientific basis for nitrogen-fixing effect prediction under global climate change.

珊瑚礁系统因其高生产力及生物多样性被喻为海洋中的“沙漠绿洲”，固氮能够为寡营养的珊瑚礁提供“新”氮，对系统生产力的维持具有重要作用。温度上升可在短期内改变珊瑚生态系统固氮生物的群落组成，从而可能影响珊瑚礁系统的营养盐状况和健康程度，但是温度胁迫对于珊瑚礁系统固氮速率的改变以及固氮生物对于温度变化的长期适应尚未清晰。针对这一科学问题，本研究拟采取实验室内温度操控培养和野外人工同位素标记技术，定量热胁迫下珊瑚礁系统的固氮速率变化，结合分子生物学技术，分离不同类型微生物的固氮信号，以揭示珊瑚礁生态系统固氮对热胁迫的短期响应方式和过程机理。进一步，本研究试图利用珊瑚礁系统砗磲的壳体中环境温度记录信息，及其壳体有机氮同位素信号，首次建立珊瑚礁温度和固氮之间的关系指标和模型，从而揭示近几十年温度变化对珊瑚礁系统固氮的影响和系统对于温度胁迫的长期适应机制，为全球变化下珊瑚礁固氮影响预测提供科学依据。

珊瑚礁系统因其高生产力及生物多样性被喻为海洋中的“沙漠绿洲”，固氮能够为寡营养的珊瑚礁提供“新”氮，对系统生产力的维持具有重要作用。温度上升可在短期内改变珊瑚生态系统固氮生物的群落组成，从而可能影响珊瑚礁系统的营养盐状况和健康程度，但是温度胁迫对于珊瑚礁系统固氮速率的改变以及固氮生物对于温度变化的长期适应尚未清晰。本项目通过实验室内温度操控培养和野外人工同位素标记技术，定量热胁迫下珊瑚礁系统的固氮速率变化，结合分子生物学技术，识别珊瑚系统中的固氮热点，以揭示热胁迫对珊瑚礁生态系统固氮的影响。进一步，本研究建立了痕量砗磲壳体氮同位素检测技术，识别了砗磲氮同位素与ENSO事件的耦合关系，从而将气候变化与珊瑚礁区氮循环以及固氮相联系，为全球变化下珊瑚礁固氮影响预测提供科学依据。.