Collaborative Research: RAPID: Quantifying the response of stream ecosystems to a punctuated cold-stress disturbance across a semi-arid to sub-humid gradient

合作研究：RAPID：量化河流生态系统对半干旱到半湿润梯度间断冷应激干扰的响应

• 批准号: 2128281
• 负责人: Christopher Patrick
• 金额: $ 3.65万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-05-15 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2128281&HistoricalAwards=false
• 关键词: Collaborative; Research; RAPID; Quantifying; response

Climate change is expected to result in increased global mean temperatures that will lead to movement of tropical and sub-tropical species toward the poles, a process known as “tropicalization”. Changes in precipitation patterns are predicted to be spatially variable, with some regions becoming drier and others wetter. The ecology and health of stream ecosystems are particularly susceptible to changes in rainfall and temperature. Simultaneously, the frequency and intensity of extreme weather events are expected to increase, and it is unknown how these extreme events will interact with gradual changes in temperature and precipitation to affect stream ecosystems. This research evaluates how a recent extreme event, the February 2021 “polar vortex” in Texas, interacts with changing mean climate conditions to predict how climate change will impact the structure and function of U.S. stream ecosystems in the coming decades. The research leverages a steep, natural rainfall gradient that features an abrupt shift in stream community composition and ecosystem functioning between semi-arid and mesic ecosystems. Repeated field measurements are being made for one year after the polar vortex and these data compared to prior data collected from these streams over the last 4 years. This work greatly increases our understanding of how climate change will affect sub-tropical stream ecosystems and their biota. Training of undergraduates (including minority) and graduate students along with community outreach via an established K–12 program contribute to the project’s broader impacts for society.The goals of this research are to characterize the direct and indirect impacts of an extreme cold event (ECE) on stream ecosystem structure and function and to examine the role of organism traits and local environmental features that drive these effects. Punctuated low temperatures below an organism’s thermal limits can result in physiological, behavioral, and fitness consequences. These events are particularly important in the context of understanding tropicalization. Warm-adapted species are expanding poleward but lack adaptations for cold conditions, and thus may be more vulnerable to ECEs, driving mass mortality events. The impact of mass mortality events on ecosystem functioning may last for months to years and result in population declines, changes to community composition, and the contribution of dead individuals to the organic matter pool. The following hypotheses are being tested: 1) mesic streams will have greater thermal buffering capacity than semi-arid sites due to their greater discharge per unit watershed and greater tree canopy that creates a microclimate above the water surface; 2) taxa in semi-arid streams will have greater cold tolerance because many of them have adaptations to cope with harsh conditions; 3) taxa with neotropical ancestry will have lower cold tolerance due to a lack of adaptions for cold stress; 4) fish and invertebrate mortality will indirectly affect the abundance of algae and benthic organic matter, impacting stream metabolism. Because ECEs may become more common in the future, studying this historically rare event may help us understand how ECEs may interact with “tropicalization”. Furthermore, the utilization of a steep rainfall gradient provides an exceptional opportunity to study the interaction between extreme disturbance and long-term climate conditions.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.

预计气候变化会导致全球平均温度升高，从而导致热带和亚热带物种向极点运动，这一过程称为“热带化”。预计精确模式的变化在空间上会发生变化，有些地区变成驱动因素，而另一些区域则更湿。流生态系统的生态和健康特别容易受降雨和温度的变化。同时，预期极端天气事件的频率和强度将增加，尚不清楚这些极端事件将如何与温度变化和精度相互作用以影响流生态系统。这项研究评估了最近的极端事件，即德克萨斯州的2021年2月的“极地涡流”如何与变化的平均气候条件相互作用，以预测气候变化将如何影响未来几十年中美国流生态系统的结构和功能。该研究利用了陡峭的自然降雨梯度，其河流社区组成和半干旱和中介生态系统之间的生态系统的突然转变。在极地涡流之后，与从过去四年中从这些流中收集的先前数据相比，进行了重复的现场测量和这些数据。这项工作大大增加了我们对气候变化将如何影响亚热带生态系统及其生物群的理解。通过既定的K – 12计划对本科生（包括少数民族）和研究生的培训以及社区宣传，对该项目对社会的广泛影响做出了更大的影响。这项研究的目标是表征极端寒冷事件（ECE）对流生态系统结构和功能的直接和间接影响，并检查有机体和当地环境特征的作用以及这些效果的作用。在生物体的热限制下方的低温处点状高温会导致生理，行为和适应性后果。这些事件在理解热带化的背景下尤为重要。温暖适应的物种正在向极向扩展，但缺乏适应寒冷条件，因此可能更容易受到ECES的影响，驱动大规模死亡事件。大规模死亡事件对生态系统功能的影响可能会持续数月至数年，并导致人口下降，社区组成的变化以及死者对有机物库的贡献。正在测试以下假设：1）中介溪的热缓冲能力比半干旱地点具有更大的热缓冲能力，因为它们的每单位流水和更大的树冠层更大，从而在水面上方产生了微气候。 2）半干旱流中的分类单元将具有更大的寒冷容忍度，因为其中许多人具有应对危害条件的适应性； 3）由于缺乏对冷应激的适应性，新热带血统的分类单元将具有较低的冷耐受性； 4）鱼类和无脊椎动物死亡率将间接影响藻类和底栖有机物的抽象，从而影响溪流代谢。由于ECE在将来可能会变得越来越普遍，因此研究这一历史罕见的事件可能有助于我们了解ECES如何与“热带化”相互作用。此外，钢降雨梯度的利用提供了一个极好的机会来研究极端灾难与长期气候条件之间的相互作用。该奖项反映了NSF的法定任务，并通过使用该基金会的知识分子优点和更广泛的影响来审查标准，通过评估来诚实地支持支持。