RAPID: Collaborative Research: Are Eastern Tropical Pacific reefs becoming more resilient to ENSO?

预测的2014-2015年厄尔尼诺Niño南方涛动（ENSO）事件可能发展成为近代历史上最强的事件之一，为研究这种极端热异常对珊瑚礁生态系统恢复能力的影响提供了一个独特而紧迫的机会。根据在东热带太平洋（ETP）进行的40年研究的基线数据，这组研究人员独特地准备测试有关珊瑚礁对袭击该地区的第三次强烈事件的恢复能力的假设。生态弹性被定义为生态系统在压力下继续运作的能力，以及系统在受到干扰后“反弹”或恢复结构和功能的能力。该项目的指导思想是，许多ETP珊瑚礁在面对多种主要ENSO干扰时，由于适应过程而变得更有弹性。如果研究人员是正确的，珊瑚礁系统在遭受连续的热干扰时可以发展出更强的耐受性，并更快地恢复，这将极大地改变对未来100年气候变化中全球珊瑚礁生态系统命运的预测。该提案的更广泛影响包括指导、推广和教育。为了吸引更广泛的受众，所有参与者都将在项目的Facebook页面上发表文章，该页面将链接到一个博客网站，公众可以在那里与科学家互动。这项RAPID资助将提供一个前所未有的机会，使我们进一步了解对袭击ETP的第三次主要ENSO的抵抗力增强和早期恢复的潜力。研究人员已经提出了一些假设，这些假设可以在巴拿马（Uva, Saboga）和Galápagos （Darwin Floreana）珊瑚礁的ENSO之前，期间和之后的关键阶段通过有针对性的采样和实验进行测试。这些珊瑚礁跨越文石饱和度的梯度，为高二氧化碳世界中整个热带地区的预期条件提供了一个现实世界的模型系统。研究人员将评估的关键机制/假设可能会增加适应力，从而降低死亡率并限制ENSO之后生态系统功能的丧失，包括：(1)耐热共生体相对丰度的增加将导致所有深度的多种珊瑚物种存活率更高，恢复速度更快；(2)采收率将与二氧化碳分压成反比，并设定一个阈值水平，超过该阈值就不会发生采收率；(3)维持完整的草食群落自上而下的强控制将限制藻类的增殖；(4)加强浅水地区的营养限制将限制藻类的竞争能力，有助于珊瑚的恢复。在每个有回收记录的地点，研究小组将进行以下观察：(1)现场测量物理参数（温度、电导率、pH值、溶解氧、光合有效辐射、叶绿素、浊度、无机营养物质）；(2)碳酸盐化学和净生态系统代谢（钙化、生产）的原位测量；(3)就地测量珊瑚和珊瑚礁群落的反应，包括珊瑚白化和死亡，以及珊瑚动物、生物侵蚀动物、食草动物和底栖藻类覆盖的种群反应；(4)量化白化事件发生前、发生中和发生后主要珊瑚物种的共生群落，并与1997-98年白化事件的存档样本进行比较；(5)生物分析自上而下（草食）和自下而上（营养限制）效应的强度，这些效应可能促进具有临界极限的生态系统恢复力。为了进一步探索这些限制，在南部Galápagos缺乏恢复力的地方，调查小组将部署温度记录器，对残余珊瑚群落的漂白和死亡率进行调查，并对食草性和营养限制的强度进行生物分析。

The predicted 2014-2015 El Niño Southern Oscillation (ENSO) event may develop into one of the strongest in recent history, presenting a unique and urgent opportunity to investigate the impact of this extreme thermal anomaly on the resilience of coral reef ecosystems. Building on baseline data from 40 years of research in the Eastern Tropical Pacific (ETP), this team of researchers is uniquely poised to test hypotheses about coral reef resilience to the third strong event to hit this region. Ecological resilience is defined as both the ability of an ecosystem to continue functioning while under stress as well as the ability of a system to "bounce back" or restore structure and function following a disturbance. This project is guided by the overarching hypothesis that many ETP coral reefs are becoming more resilient in the face of multiple major ENSO disturbances as a result of adaptive processes. If the investigators are correct that reef systems can develop more tolerance and recover more rapidly when subjected to sequential thermal disturbances, this will drastically change predictions of the fate of global coral reef ecosystems over the next 100 years of climate change. The Broader Impacts of this proposal include mentoring, outreach, and education. To engage a broad audience, all participants will contribute to a project Facebook page, which will be linked to a blogging website where the public can interact with the scientists. This RAPID funding will provide an unprecedented opportunity to further our understanding of the potential for increased resistance to, and accelerated early recovery from, the third major ENSO to hit the ETP. The investigators have developed hypotheses that can be tested by targeted sampling and experiments in the critical stages before, during and after this ENSO on reefs in Panamá (Uva, Saboga) and Galápagos (Darwin Floreana). These reefs span a gradient in aragonite saturation that provides a real-world model system for conditions expected throughout the tropics in a high-CO2 world. Key mechanisms/hypotheses that the investigators will evaluate that may increase resilience, and therefore reduce mortality and limit the loss of ecosystem functioning following this ENSO, include: (1) increases in the relative abundance of thermotolerant symbionts will result in higher survival and faster recovery of multiple coral species across all depths; (2) recovery will be inversely rated to pCO2 with a threshold level beyond which recovery does not occur; (3) the maintenance of strong top-down control by intact herbivore communities will limit algal proliferation, and (4) the strengthening of nutrient-limitation in shallow regions will limit algal competitive abilities and aid coral recovery. At each site where there is a record of recovery the research team will make the following ovservations: (1) in situ measurement of physical parameters (temperature, conductivity, pH, dissolved oxygen, photosynthetically active radiation, chlorophyll, turbidity, inorganic nutrients); (2) in situ measurement of carbonate chemistry and net ecosystem metabolism (calcification, production); (3) In situ measurements of coral and reef community responses including coral bleaching and mortality and the population responses of corallivores, bioeroders, herbivores, and benthic algal cover; (4) quantification of symbiont communities in major coral species before, during and after the bleaching event to compare with archived samples from the 1997-98 event; (5) bioassays of the strength of top-down (herbivory) and bottom-up (nutrient limitation) effects that may promote ecosystem resilience with critical limits. To further explore these limits, in the southern Galápagos, where there is a lack of resilience, the investigative team will deploy temperature loggers, conduct surveys of bleaching and mortality of remnant coral communities, and conduct bioassays of the strength of herbivory and nutrient limitation.