Ocean Acidification: Physiological Mechanisms for CO2-sensing and Related Intracellular Signaling Pathways in Corals

过去200年来，作为现代工业化人类生活方式的副产品，二氧化碳在大气中迅速积累。这些过量二氧化碳的很大一部分溶解在海洋中，产生氢离子，降低了水的pH值，从而使水变得更酸。由于目前海洋酸化的速度比地质记录中记录的最快速度还要快，因此尚不清楚海洋生物是否能够生存并适应海洋化学的这些快速变化。珊瑚礁是最易受海洋酸化影响的生物之一，因为它们的碳酸钙骨架在酸性更强的ph值下溶解。此外，海洋酸化对珊瑚的有害影响还可能扩展到施肥、新陈代谢以及珊瑚与其共生藻类之间的基本关系。然而，由于缺乏关于基本珊瑚细胞生理学的资料，因此无法根据严格的化学和机械模型来预测海洋酸化的影响。我们对珊瑚基本生物学知识的限制反过来又限制了对这些重要海洋资源的政策制定和管理决策的有效性。这个项目将描述珊瑚用来感知二氧化碳、pH值和碳酸氢盐的分子和细胞机制，它们相关的信号转导途径，它们在调节生理方面的作用，以及它们对海洋酸化的反应。该项目将使用一套实验技术，包括重组蛋白的体外生化分析；珊瑚细胞培养的实时显微镜成像，以确定细胞内pH值、钙化和生物荧光的调节；用活珊瑚碎片做呼吸测量实验。因此，这项研究将在从分子到细胞到整个生物体的广谱范围内描述珊瑚对海洋酸化的生理反应。这项研究有可能产生机制模型来解释和预测海洋酸化对珊瑚的影响，从而补充正在进行和未来的生理学、转录组学和基因组学研究，同时也将珊瑚生理学的基础研究与珊瑚礁管理联系起来。这项研究的其他更广泛的影响包括指导处于职业生涯不同阶段的年轻科学家（几名志愿者，本科生和研究生以及一名博士后研究员）。该项目与校内、国家和国际实验室，特别是与摩纳哥科学中心的研究人员建立了跨学科研究合作。斯克里普斯的伯奇水族馆将举办一个博物馆展览，以提高公众对海洋酸化的认识。再加上一系列的公开讲座和在线资源，这些活动每年将吸引大约40万名参加伯奇水族馆的儿童和成人，以及数百万在线观众。

Carbon dioxide has been rapidly accumulating in the atmosphere over the past 200 years as a by-product of the modern industrialized human lifestyle. A large portion of this excess carbon dioxide is dissolving in the oceans, producing hydrogen ions that lower the pH of the water, thus making it more acidic. Because the current rate of ocean acidification is faster than the most rapid rates recorded in the geological record, it is unclear whether marine organisms will be able to survive and adapt to these rapid changes in ocean chemistry. Coral reefs are among the most vulnerable organisms to ocean acidification owing to their calcium carbonate skeleton that dissolves at more acidic pH. Moreover, the deleterious effects of ocean acidification on corals may also extend to fertilization, metabolism and to the essential relationship between corals and their symbiotic algae. However, the lack of information on basic coral cell physiology precludes predicting the effects of ocean acidification based on strict chemical and mechanistic models. The limits to our knowledge about the basic biology of corals in turn limits the effectiveness of policy-making and managerial decisions about these important marine resources. This project will characterize the molecular and cellular mechanisms used by corals to sense carbon dioxide, pH and bicarbonate, their associated signal transduction pathways, their roles in regulating physiology, and their responses to ocean acidification. This project will use a suite of experimental techniques, including in vitro biochemical assays with recombinant proteins; real-time microscopy imaging of coral cell cultures to determine regulation of intracellular pH, calcification and biofluorescence; and respirometry experiments with live coral fragments. Therefore, this study will characterize coral physiological responses to ocean acidification over the broad spectrum from molecules, to cells to whole organisms.This research has the potential to generate mechanistic models to explain and predict the effects of ocean acidification on corals, thereby complementing ongoing and future physiological, transcriptomic and genomic studies, while also bridging fundamental research on coral physiology with coral reef management. Other broader impacts of this research include mentoring of young scientists at various stages of their careers (several volunteers, undergraduate and graduate students and one postdoctoral researcher). The project establishes interdisciplinary research collaborations with intramural, national and international laboratories, particularly with researchers at Centre Scientifique de Monaco. A museum exhibit will be developed at the Birch Aquarium at Scripps to enhance public awareness of ocean acidification. Together with a series of public lectures and online resources, these activities will reach approximately 400,000 children and adults that attend the Birch Aquarium annually, and millions of online viewers.