造礁石珊瑚对富营养化和高温胁迫的响应机制及适应潜力

海水富营养化会抑制珊瑚对其内共生藻种群生长的控制能力，引起共生藻过度增殖、共生体自养能力下降，导致珊瑚在高温胁迫时更容易发生白化。珊瑚体内存在“最佳”的共生藻密度使珊瑚自养能力最大化、白化抵抗力增强。目前国际上关于珊瑚“最佳”共生藻密度的研究非常有限，富营养化影响珊瑚热白化的生理机制仍不清楚。本项目拟以块状、叶片状和枝状造礁石珊瑚（热白化敏感性依次增高）为研究对象，通过野外调查——考察其在自然环境下的生理动态变化特征，以及室内模拟实验——系统研究富营养化条件下不同热白化敏感性珊瑚种类由健康→热白化→恢复/死亡的生理动态变化过程，从而揭示敏感性不同的珊瑚种类抵抗白化的“最佳”共生藻密度和发生热白化的关键生理阈值，阐明富营养化对珊瑚热白化的影响机制，评估热胁迫结束后珊瑚种类的恢复潜力。研究结果可为量化珊瑚礁白化的水质富营养化阈值提供数据支持，为珊瑚礁白化预警、珊瑚礁保护和管理提供科学依据。

Although it is well established that nutrient enrichment can increase the susceptibility of reef corals to bleaching, the mechanism(s) underpinning this etiology have not been well attributed. Enrichment of seawater results in an enlarged, fast‐growing symbiont population that is ultimately a net carbon sink for the energetic resources of the coral, which increase the susceptibility of corals to bleaching. While reef corals exist ‘optimum’ Symbiodinium density maximizing autotrophic capacity (P:R) to resist thermal stress. However, lack of mechanistic understanding limits the identification of biologically‐relevant, eutrophication thresholds that are needed for the region‐specific design of effective management strategies. In this project, massive, plating and branching corals across five dominant coral species are investigated seasonally at Luhuitou fringing reef in Sanya, Hainan Island, northern South China Sea (SCS), and their physiological indicators are measured to evaluate species‐specific ‘optimum’ Symbiodinium density in northern SCS. On the basis of this field investigation, experimental study is designed to disentangle the effects of eutrophication on the physiological response of species‐specific corals subject to normal and to a short-term temperature increase (Coral health→Coral Bleaching→Recovery/Death). Additionally, three different inorganic nutrient ratios are tested to assess the influence of nutrient stoichiometry on coral physiology, and to explore physiological thresholds of coral bleaching, as well as to assess the resilience of corals.