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

生态系统可能表现出“临界点”，即环境干扰将生态系统推入一种改变的状态，使其无法恢复，即使环境正常化也是如此。2012年，这种情况可能发生在佛罗里达州西北部的珍贵牡蛎礁上，当时干旱和河水流量低，使得捕食牡蛎的动物大量繁殖，几乎吃掉了所有的牡蛎。尽管随后几年的降雨量和河流流量正常，牡蛎仍然没有恢复，这表明生态系统可能已经越过了一个临界点。然而，飓风迈克尔(2018年)的干扰时间和强度可能已经将生态系统推向了最初的健康状态。在这个项目中，研究人员进行实地观察，以衡量捕食者和牡蛎对飓风迈克尔的反应，并进行实验室实验，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现场和实验室中观察到的影响是否会导致回到临界点之后。这是研究牡蛎生态系统如何从变化状态恢复到健康状态的难得机会。然而，在天气和海湾的季节性变化掩盖飓风影响之前，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，它将拓展生态临界点理论。其次，它可以支持阿巴拉契科拉湾牡蛎渔业的管理，例如洞察恢复工作可能取得的成功。为此，该小组与阿帕拉契科拉国家河口研究保护区进行了协调。最后，研究成果被纳入正在进行的公共教育和培训工作中。生态系统可以迅速从它们最初的高价值状态转变为一种新的、退化的状态。在许多生态系统中都观察到了这种转变，但有时很难确定使这种转变超越“临界点”的机制，以及--在更大程度上--可能调解向原始状态转变的机制。提高我们对临界点的理解和预测能力有赖于确定系统双向转变背后的机制。2012年，佛罗里达州阿巴拉契科拉湾的牡蛎礁突然变成了没有牡蛎的状态，因为长期的干旱和低流量使得海洋牡蛎捕食者大量繁殖。尽管随后几年的降雨量和流量正常，但没有出现回归变化，这表明这个生态系统可能已经进入了一种交替的稳定状态。这项工作的假设是，2018年飓风迈克尔提供了足够的扰动，使系统回到吸引盆地的原始状态(先前的观察支持这一预测)。该项目将现场观察和实验室实验与人口建模结合起来，以测试飓风迈克尔是否以及如何引发了逆转。在这个生态系统的季节性变化掩盖飓风影响之前，快速反应是必不可少的。该提案的学术价值基于其解决生态学一个核心目标的能力：识别和预测生态系统临界点。将经验观察和模型相结合是推进这一目标的一种有前途的方法，但尚未在该领域广泛应用，主要是因为研究人员在换班时不在适当的位置。迈克尔飓风为解决这一知识鸿沟提供了一个独特的机会。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.