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

预测的2014-2015年厄尔尼诺南方涛动(ENSO)事件可能发展为近年来最强烈的事件之一，为研究这种极端温度异常对珊瑚礁生态系统弹性的影响提供了一个独特而紧迫的机会。基于东热带太平洋(ETP)40年来研究的基线数据，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弹性的假设。生态复原力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，由于适应过程，许多ETP珊瑚礁在面对多个主要的ENSO扰动时正变得更具弹性。如果研究人员是正确的，即珊瑚礁系统在受到连续的热扰动时可以产生更多的耐受性，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。这项建议的更广泛影响包括指导、外展和教育。为了吸引广泛的受众，所有参与者都将参与一个Facebook项目页面，该页面将链接到一个博客网站，在那里公众可以与科学家互动。这一快速融资将提供一个前所未有的机会，进一步加深我们对第三次主要ENSO袭击ETP的阻力增加和加速早日恢复的可能性的了解。研究人员提出了一些假设，可以通过在这次ENSO之前、期间和之后在Panamá礁(Uva，Saboga)和加拉帕戈斯礁(Darwin Floreana)的关键阶段进行有针对性的抽样和实验来检验。这些珊瑚礁跨越了文石饱和度的梯度，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真实世界的模型系统。研究人员将评估的可提高复原力、从而降低死亡率和限制此次ENSO事件后生态系统功能损失的关键机制/假设包括：(1)耐热共生体相对丰度的增加将导致所有深度多种珊瑚物种更高的存活率和更快的恢复；(2)恢复程度将与二氧化碳浓度成反比，超过一个阈值水平将不会发生恢复；(3)完整的草食植物群落维持自上而下的强有力的控制将限制藻类繁殖；(4)浅水地区营养限制的加强将限制藻类的竞争能力和帮助珊瑚恢复。在每个有恢复记录的地点，研究小组将进行以下观测：(1)现场测量物理参数(温度、电导率、pH、溶解氧、光合作用有效辐射、叶绿素、浊度、无机营养物质)；(2)现场测量碳酸盐化学和净生态系统新陈代谢(钙化、生产)；(3)现场测量珊瑚和珊瑚礁群落反应，包括珊瑚漂白和死亡率以及珊瑚、生物爬行动物、草食动物和底栖藻类的种群反应；(4)在漂白事件之前、期间和之后对主要珊瑚物种中的共生体群落进行量化，以与1997-98年漂白事件的存档样本进行比较；(5)对自上而下(食草性)和自下而上(营养限制)效应的强度进行生物分析，以提高生态系统的弹性和临界极限。为了进一步探索这些限制，在缺乏复原力的加拉帕戈斯南部，调查小组将部署温度记录仪，对残存珊瑚群落的漂白和死亡率进行调查，并对草食强度和营养限制进行生物测试。

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.