Collaborative Research: The physiology and ecology of widespread 'stress tolerant' coral endosymbionts: coral 'saviors' or opportunistic invaders?

海洋变暖正以多种方式影响着地球上的生命。高温可破坏甲藻(Symbioddium spp.)以及造礁珊瑚(即珊瑚漂白)，从而有可能使全球失去一个重要的海洋生态系统。珊瑚-甲藻共生体对全球气候变化带来的环境胁迫的生理、生态和进化响应是复杂的。某些类型的共生藻类的传播可能会提高珊瑚对热应激的耐受性，并帮助它们在较温暖的海洋中坚持下去，但或许不会在不牺牲珊瑚健康的情况下做到这一点。在加勒比海的众多珊瑚中，二鞭毛虫暂时被命名为共生体Trenchi已经变得越来越常见，但相对于其他共生体来说，它的丰度往往较低。虽然Trenchi在变暖期间和之后的数量可能会增加，但在恢复正常条件后，它通常会被其他共生体取代。遗传证据表明，S.Trenchi最近在加勒比海入侵和/或扩张，并与许多珊瑚建立了联系，相对于它与印度-太平洋珊瑚的共生环境，这些珊瑚似乎优化得很差，或适应不良。这个项目将调查来自大西洋和太平洋的珊瑚中Trenchi的共生、生态学和生理学。漂白实验将研究温度升高对碳从藻类转移到宿主珊瑚的影响(通过稳定的同位素标记)，以及与拥有其他共生线虫的群体相比，携带S.Trenchi的群体之间的光合作用和生长的影响。将调查基于漂白严重程度和恢复时间的共生体群落变化以及改变长期菌落生长的可能性。一项相互移植的研究将考察太平洋珊瑚之间的竞争相互作用和共生体的稳定性。这些研究将测试S.Trenchi的持续传播是否会影响加勒比海珊瑚的生长，以及如果环境条件恶化，它是否会在印度-太平洋地区表现出类似的行为。该项目的结果有可能提供关于广泛分布的共生藻类如何(或是否)可能影响造礁珊瑚的复原力及其生存潜力的变革性信息，预计气候变化导致的海洋变暖加剧。除了培训一名博士后学者和几名研究生外，该项目还将通过与帕劳国家水族馆、帕劳国际珊瑚礁中心和当地学校的几次外联努力，加强科学发现和代表不足群体的参与。将与当地几名高中教师和学生一起发展海洋共生和科学教育单位，并将为帕劳社区学院的学生提供独特的研究机会。同样，一个新的教育展示将被开发出来，并在特拉华大学的开放日上展示，展示全球气候可能如何影响珊瑚礁，并描述目前更好地了解珊瑚-藻类共生的生理学的研究。展览随后将捐赠给帕劳水族馆供未来使用。该奖项由国家科学基金会国际和综合活动办公室共同资助。

Ocean warming is affecting life on our planet in many ways. High temperature can disrupt the endosymbioses between dinoflagellate algae (Symbiodinium spp.) and reef-building corals (i.e. coral bleaching), thereby risking the global loss of a critical marine ecosystem. The physiological, ecological and evolutionary responses of coral-dinoflagellate symbioses to environmental stress brought on by global climate change are complex. The spread of certain types of symbiotic algae may increase the thermal stress tolerance among corals and help them persist in warmer oceans, but perhaps not without trade-offs to the health of the coral. The dinoflagellate tentatively named Symbiodinium trenchi has become increasingly more common in numerous corals throughout the Caribbean, but is often at low-abundance relative to other symbionts. While S. trenchi can increase in abundance during and after warming, it is often displaced by other symbionts following a return to normal conditions. Genetic evidence indicates that S. trenchi recently invaded and/or expanded in the Caribbean and has developed associations with many corals that seem to be poorly optimized, or mal-adapted, relative to the symbioses it maintains with corals in the Indo-Pacific. This project will investigate the symbiosis ecology and physiology of S. trenchi in corals from the Atlantic and Pacific Oceans. Bleaching experiments will examine the effects of increased temperature on transfer of carbon from the algae to the host coral (via stable isotopic tagging), as well as photosynthesis and growth among colonies harboring S. trenchi compared to colonies harboring other Symbiodinium spp. The potential for symbiont community shifts as well as altered long-term colony growth based on bleaching severity and recovery time will be investigated. A reciprocal transplant study will examine the competitive interaction and stability of symbionts among Pacific corals. These studies will test if the continued spread of S. trenchi will affect coral growth in the Caribbean and whether it might behave similarly in the Indo-Pacific if environmental conditions worsen. The results from this project have the potential to supply transformative information regarding how (or if) a widely distributed symbiotic algal species may influence the resilience of reef-building corals and their potential to survive projected increases in ocean warming due to climate change. In addition to training one postdoctoral scholar and several graduate students, this project will enhance scientific discovery and participation of underrepresented groups via several outreach efforts with the Palau National Aquarium, Palau International Coral Reef Center, and local schools. Educational units in marine symbioses and science will be developed with several local high school teachers and students, and unique research opportunities will be provided to students at the Palau Community College. Likewise, a new educational display addressing how global climate may impact coral reefs, and describing the current research to better understand the physiology of coral-algal symbioses, will be developed and presented at the University of Delaware open house "Coast Day." The display will be donated subsequently to the Palau Aquarium for future use.This award is co-funded by NSF's Office of International and Integrative Activities.