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）事件可能发展成为近代历史上最强的事件之一，为调查这一极端热异常对珊瑚礁生态系统复原力的影响提供了一个独特而紧迫的机会。基于在东热带太平洋（ETP）40年研究的基线数据，这支研究团队准备测试有关珊瑚礁对该地区第三次强烈事件的恢复能力的假设。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干扰后“反弹”或恢复结构和功能的能力。该项目以一个总体假设为指导，即由于适应过程，许多ETP珊瑚礁在面对多重重大厄尔尼诺/南方涛动干扰时变得更具复原力。如果研究人员是正确的，珊瑚礁系统在受到连续的热干扰时可以发展出更大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。为了吸引广大受众，所有参与者都将为一个项目Facebook页面做出贡献，该页面将链接到一个博客网站，公众可以在该网站上与科学家互动。这一快速资助将提供一个前所未有的机会，进一步加深我们对第三次重大ENSO袭击ETP的抵抗力增强和加速早期恢复的潜力的理解。调查人员提出了一些假设，这些假设可以在厄尔尼诺/南方涛动之前、期间和之后的关键阶段，在帕纳马（乌瓦、萨沃加）和加拉帕戈斯（达尔文弗洛雷阿纳）的珊瑚礁上进行有针对性的取样和实验加以检验。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能增加复原力的关键机制/假设，从而减少死亡率并限制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的生存率提高和恢复速度加快;（2）恢复将与pCO 2成反比，具有阈值水平，超过该阈值水平不会发生恢复;（3）完整的食草动物群落保持强有力的自上而下的控制将限制藻类的增殖，（4）浅水区营养盐限制的加强将限制藻类的竞争能力，有助于珊瑚的恢复。在每个有恢复记录的地点，研究小组将进行以下观察：（1）现场测量物理参数（2）原位测量碳酸盐化学和生态系统净代谢（3）对珊瑚和珊瑚礁群落的反应，包括珊瑚白化和死亡率以及珊瑚虫、生物侵蚀者、食草动物和底栖藻类覆盖的种群反应进行现场测量;（4）量化主要珊瑚品种在漂白事件发生前、发生期间及发生后的共生体群落数量，以与一九九七至九八年漂白事件的存档样本作比较;（5）对自上而下（食草动物）和自下而上（养分限制）效应的强度进行生物测定，这些效应可能促进生态系统在临界限度内的复原力。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，对残余珊瑚群落的漂白和死亡情况进行调查，并对食草动物的强度和营养限制进行生物测定。

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.