Collaborative Research: NSFDEB-NERC: Warming's silver lining? Thermal compensation at multiple levels of organization may promote stream ecosystem stability in response to drought

人类活动和相关的温室气体排放正在导致全球气温上升和干旱等极端气候事件的增加。这一美英合作项目的重点是了解持续变暖和日益干旱将如何结合在一起影响溪流和河流生物(即细菌、藻类和动物)的组成和活动。目前，普遍的观点是，气温变暖和干旱共同产生的生态后果将比单独由这两种压力中的任何一种造成的更极端。然而，该项目研究了一个相反的假设，即生物体和群落可能会在很长一段时间内‘适应’气候变暖，使它们在未来不太容易受到极端干旱事件的影响。从本质上讲，这个项目测试了这样一种假设，即河流群落弥补了持续变暖的影响，因此在未来干旱日益加剧的情况下，将能够更好地维持和发挥作用。这项研究对于预测和减轻气候变暖和干旱将如何影响淡水生物多样性，以及河流中许多重要的生态过程，如养分去除和食物生产，造福人类至关重要。该项目将为研究生和本科生提供培训、教育和职业发展机会。该项目利用了两个独特的研究环境：(1)冰岛的自然溪流温度梯度；(2)英国伯明翰大学最先进的实验溪流设施，以测试长期变暖在多大程度上提高了溪流生态系统的稳定性(包括抗旱性和弹性)，以应对干旱事件。第一个目标侧重于个体层面，调查对气候变暖的生理适应是否可以弥补高温下无脊椎动物碳利用效率的下降，从而加速干旱后的生长和能量转移(即，恢复力)。第二个目标量化了整个无脊椎动物群落及其生物量在自然和实验温度梯度上对干旱的抵抗力和复原力。最后一个目标是通过研究气候变暖引起的初级生产者群落和养分供应的变化如何影响生态系统新陈代谢的稳定性和应对干旱的氮素吸收，来探讨生态系统层面补偿性反应的潜力。综合起来，这些目标将使人们更广泛地了解多个生物组织(即从个体到生态系统)对气候变暖的补偿反应，并将有助于淡水生态系统的管理。该项目由环境生物学分部的人口和社区生态集群和已建立的激励竞争研究计划(EPSCoR)共同资助。该项目的英国合作者将通过UK-NERC计划获得资金。该奖项反映了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。

Human activities and associated greenhouse gas emissions are causing a rise in global temperatures and an increase in extreme climatic events such as droughts. This collaborative USA-UK project is focused on understanding how continued warming and increasing drought will combine to influence the composition and activity of stream and river organisms (i.e., bacteria, algae, and animals). At present, the prevailing view is that warming temperatures and drought will together produce more extreme ecological consequences than would result from either of these stressors alone. However, this project examines a contrary hypothesis that organisms and communities may ‘adjust’ to warming over long periods of time, making them much less susceptible to extreme drought events in the future. In essence, this project tests the hypothesis that stream communities compensate for continued warming and thus will be better able to persist and function in the face of increasing future drought. This research is critical for predicting and mitigating how warming and drought will influence freshwater biodiversity, as well the many important ecological processes in streams, such as nutrient removal and food production, that benefit humanity. This project will provide training, education and professional development opportunities to graduate and undergraduate students.This project takes advantage of two unique research settings: (1) a natural stream thermal gradient in Iceland; and (2) a state-of-the-art experimental stream facility at the University of Birmingham, UK to test the degree to which long-term warming enhances stream ecosystem stability (both resistance and resilience) in response to drought events. The first objective, focused at the individual level, investigates whether physiological adaptations to warming can compensate for reduced invertebrate carbon use efficiencies at high temperatures, thus accelerating growth and energy transfer (i.e., resilience) following drought. The second objective quantifies resistance and resilience of entire invertebrate communities and their biomass production to drought across natural and experimental thermal gradients. The final objective explores the potential for ecosystem-level compensatory responses by examining how warming-induced shifts in primary producer communities and nutrient supply influence stability of ecosystem metabolism and nitrogen uptake in response to drought. Together, these objectives will provide a broader understanding of compensatory responses to warming across multiple levels of biological organization (i.e., individuals to ecosystems), and will help to inform management of freshwater ecosystems. This project is jointly funded by the Population and Community Ecology Cluster in the Division of Environmental Biology and the Established Program to Stimulate Competitive Research (EPSCoR). The UK collaborators on this project will be funded through the UK-NERC program.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.