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

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.

人类活动和相关的温室气体排放导致全球温度的升高，并在极端气候事件（例如干旱）中增加。这个协作的美国-UK项目的重点是了解如何持续变暖和干旱将如何结合起来，以影响溪流和河流生物的组成和活动（即细菌，藻类和动物）。目前，普遍的观点是，温暖的温度和干旱将共同产生比仅此两种压力源中的任何一个都会产生更多的极端生态后果。但是，该项目研究了一个对比假设，即生物和社区可能会“适应”长时间的变暖，从而使它们在未来不易受到极端干旱事件的影响。从本质上讲，该项目检验了以下假设：流群社区弥补了持续的变暖，因此面对不断增加的干旱，将能够更好地持续和运作。这项研究对于预测和减轻变暖和干旱将如何影响淡水生物多样性以及溪流中许多重要的生态过程，例如营养消除和食品生产，对人类有益的许多重要生态过程至关重要。该项目将为毕业和本科生提供培训，教育和专业发展机会。该项目利用了两个独特的研究环境：（1）冰岛的自然流热梯度； （2）英国伯明翰大学的最先进的实验溪流设施，以测试长期变暖对响应干旱事件响应的河流生态系统稳定性（耐药性和阻力）的程度。第一个目标集中在个体水平上，它调查了对温暖的身体适应是否可以补偿高温下无脊椎动物碳的使用效率的降低，从而加速了干旱后的生长和能量转移（即弹性）。第二个目标量化了整个无脊椎动物群落及其生物量生产的抵抗力和弹性，以跨天然和实验热梯度进行干旱。最终目标通过研究了温暖诱导的主要生产者社区的转变和营养供应如何影响生态系统代谢和氮摄取的稳定性，从而探讨了生态系统级补偿性反应的潜力。这些目标共同将对跨多个生物组织（即个人对生态系统）进行变暖的补偿性反应提供更广泛的理解，并有助于告知淡水生态系统的管理。该项目由环境生物学系和启发竞争性研究的既定计划（EPSCOR）共同资助。英国合作者在该项目上的合作者将通过UK-NERC计划资助。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响评估标准，认为通过评估被认为是珍贵的支持。