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

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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.