New insights into the response of reef corals to climate change using the symbiont to host cell ratio as a metric of bleaching susceptibility

珊瑚礁生态系统的长期未来取决于珊瑚作为重要栖息地建设者的持续存在。全球珊瑚礁面临的环境威胁包括慢性和急性热应激(可能导致？珊瑚白化（这是共生藻类被驱逐的结果）、二氧化碳增加和营养物污染。本项目将使用一种新的基于分子的技术来评估这些压力源的独立和相互作用，表明珊瑚白化的敏感性取决于珊瑚组织中共生体：宿主（S:H）细胞的比例。较高比例（更多共生体）的珊瑚预计更容易受到热应激的影响，这表明影响共生体密度的非生物因素可以直接影响耐热性。这种新的共生密度度量具有生理相关性，并且已经揭示了与目前使用的度量不同的模式，从而为这些共生的动态提供了新的见解。该项目还将继续发展和应用这些方法，以进一步了解珊瑚-藻类共生的生态学，同时帮助阐明这些关键的生态系统工程师对环境复杂变化的反应。拟议的活动将帮助我们了解共生伙伴的调节如何权衡对环境的反应，以及与珊瑚对环境压力的不同敏感性有关。量化共生体丰度的分子分析的发展代表了一种技术资源，将有助于推动珊瑚生态学领域的发展。该项目将培训一名博士后研究员和几名学生（研究生和本科生），帮助扩大一个新的先进的海水实验室，建立一个新的珊瑚苗圃作为教育资源，并将纳入正在进行的K-12外展活动和参与大众媒体以扩大公众外展活动。

The long-term future of reef ecosystems depends on the continued persistence of corals as essential habitat builders. Environmental threats facing coral reefs globally include chronic and acute thermal stress (which can result in ?coral bleaching" as a result of the expulsion of their symbiotic algae), increasing CO2, and nutrient pollution. This project will assess the independent and interactive effects of these stressors using a new molecular based technique showing that coral bleaching susceptibility depends on the symbiont:host (S:H) cell ratio in coral tissues. Corals with higher ratios (more symbionts) are predicted to be more susceptible to thermal stress, suggesting that abiotic factors that affect symbiont densities can directly influence thermal tolerance. This new metric of symbiont density is of physiological relevance and has already revealed patterns that differ from currently used metrics, thus providing new insights into the dynamics of these symbioses. This project will also continue the development and application of these methods to further our understanding of the ecology of coral-algal symbioses, while helping to elucidate the responses of these critical ecosystem engineers to complex changes in their environment. The proposed activities will help us understand how tradeoffs in the regulation of symbiotic partners respond to the environment and relate to the differential susceptibility of corals to environmental stress.The development of molecular assays to quantify symbiont abundance represents a technical resource that will help advance the field of coral ecology. This project will train a postdoctoral researcher and several students (graduate and undergraduate), helps expand a new state-of-the-science running seawater laboratory, establishes a new coral nursery as an educational resource, and will be incorporated into ongoing activities in K-12 outreach and involvement with mass media for broader public outreach.