Collaborative Research: RAPID: Quantifying mechanisms by which Hurricane Michael facilitates a stable-state reversal on oyster reefs

生态系统可以表现出“临界点”，即环境干扰将生态系统推向一种改变状态，即使在环境恢复正常的情况下也无法恢复。这可能发生在2012年佛罗里达州西北部宝贵的牡蛎礁上，当时干旱和河水流量低，牡蛎的捕食者大量繁殖，几乎吃掉了所有的牡蛎。尽管随后几年的降雨和河水流量正常，牡蛎却没有恢复，这表明生态系统可能已经越过了一个临界点。然而，迈克尔飓风（2018年）造成的干扰的时间和程度可能已经将生态系统推向了原始的健康状态。在这个项目中，研究人员进行了实地观察，以评估捕食者和牡蛎对飓风迈克尔的反应，并进行了实验室实验，以测试捕食者和牡蛎对飓风降雨条件的反应。此外，他们使用数学模型来预测在野外和实验室观察到的影响是否会导致回到临界点。这是一个难得的机会来研究牡蛎生态系统如何从被改变的状态恢复到健康状态。然而，在天气和海湾的季节性变化掩盖飓风的影响之前，快速反应是必不可少的。这项研究有几个更广泛的影响。首先，它将扩展临界点的生态理论。其次，它可以支持对阿巴拉契科拉湾牡蛎渔业的管理，比如对恢复工作可能成功的洞察。为此，该小组与阿巴拉契科拉国家河口研究保护区进行协调。最后，将研究成果纳入正在进行的公共教育和培训工作。生态系统可以迅速从原来的高价值状态转变为新的退化状态。在许多生态系统中都观察到这样的变化，但有时很难确定调节超过“临界点”的变化的机制，以及在更大程度上调节回归原始状态的机制。提高我们对临界点的理解和预测能力取决于确定双向系统转移背后的机制。2012年，佛罗里达州阿巴拉契科拉湾（Apalachicola Bay）的牡蛎礁突然变成了一个牡蛎数量减少的状态，因为长期干旱和河水流量低，使得海洋牡蛎捕食者大量繁殖。尽管随后几年的降雨和流量正常，但没有出现回归转移，这表明这个生态系统可能已经进入了另一种稳定状态。这项工作的假设是，2018年飓风迈克尔提供了一个足够的扰动，使系统回到吸引盆地的原始状态（先前的观测支持这一预测）。该项目将实地观察和实验室实验与人口模型相结合，以测试飓风迈克尔是否以及如何引发逆转转变。在这个生态系统的季节性变化掩盖飓风的影响之前，快速反应是至关重要的。该提案的智力价值在于它能够解决生态学的一个核心目标：识别和预测生态系统的临界点。结合经验观察和模型是推进这一目标的一种有希望的方法，但尚未在该领域得到广泛应用，主要是因为研究人员在转变时没有到位。“迈克尔”飓风为解决这一知识鸿沟提供了一个独特的机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ecosystems can exhibit "tipping points" whereby an environmental disturbance pushes an ecosystem into an altered state from which it does not recover, even when the environment normalizes. This may have happened to valuable oyster reefs in Northwest Florida in 2012, when drought and low river flow allowed predators of oysters to flourish and consume nearly all the oysters. Despite subsequent years of normal rainfall and river flow, oysters have not recovered, suggesting the ecosystem may have crossed a tipping point. However, the timing and magnitude of the disturbance from Hurricane Michael (2018) may have pushed the ecosystem back towards its original, healthy state. In this project, investigators make field observations to gauge how predators and oysters are responding to Hurricane Michael and conduct lab experiments to test how predators and oysters respond to hurricane rainfall conditions. Additionally, they use mathematical models to predict whether effects observed in the field and lab could lead to a shift back past the tipping point. This is a rare opportunity to study how oyster ecosystems can shift back from altered to healthy states. However, a rapid response is essential before seasonal changes in the weather and bay obscure hurricane impacts. This research has several broader impacts. First, it will expand the ecological theory of tipping points. Second, it can support the management of the Apalachicola Bay oyster fishery, such as insight into the likely success of restoration efforts. The team coordinates with the Apalachicola National Estuarine Research Reserve to this end. Finally, research outputs are incorporated into ongoing public education and training efforts.Ecosystems can rapidly shift from their original, high-value state to a new, degraded one. Such shifts have been observed in many ecosystems, but it is sometimes difficult to identify the mechanisms that mediate the shift beyond a "tipping point" and - to a greater extent - those that could mediate a shift back to the original state. Improving our understanding and predictive capability of tipping points depends on identifying the mechanisms that underlie bi-directional system shifts. In 2012, the oyster reefs of Apalachicola Bay, FL abruptly shifted into an oyster-less state when prolonged drought and low river flow allowed marine oyster predators to flourish. Despite subsequent years of normal rainfall and flow, there has not been a return shift, suggesting this ecosystem may have entered an alternate stable state. The hypothesis of this work is that in 2018 Hurricane Michael provided a sufficient disturbance to shift the system back into the attracting basin for its original state (prior observations support this prediction). This project couples field observations and lab experiments with population modeling to test whether and how Hurricane Michael initiated a reversal shift. A rapid response is essential before seasonal variability in this ecosystem obscures hurricane effects. The proposal's intellectual merit is based on its ability to address a central goal in ecology: identifying and predicting ecosystem tipping points. Combining empirical observations and models is a promising approach to advance this goal, but has not been widely applied in the field, mainly because researchers are not in place at the time of a shift. Hurricane Michael provides a unique opportunity to address this knowledge gap.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.