RAPID: Effects of wildfires on lake productivity and oxygen deficits in the western U.S.

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Extreme wildfires now occur with increasing regularity in western North America and other parts of the world. These wildfires generate large plumes of smoke and ash that can travel thousands of miles and persist for weeks or longer in the atmosphere. These “smoke storms” block sunlight and deposit ash on surfaces. Lakes and ponds are affected by the reduced light and ash inputs from wildfires, but much about these potential impacts is unknown. Light and nutrients are both important factors that regulate the growth of plants and algae in aquatic ecosystems. Rates of primary production from plants and algae in turn determine how much food becomes available for other organisms, such as fish, and can affect many aspects of water quality. Thus, understanding how and why aquatic primary production is responding to wildfires is a critical research objective. This project will help develop a predictive understanding of how aquatic ecosystems respond to wildfire, serving the 29 National Forests, 14 National Parks, and numerous lands managed by the states of California and Oregon. The project will provide Science, Technology, Engineering, and Mathematics (STEM) training to undergraduate, graduate students, and post-doctoral scholars. Presentations of the results will be given to scientists, managers, and the general public through professional conferences and public lecture series hosted by the Tahoe Environmental Research Center, and through other state and federal agencies. This project will disentangle the interactive effects of reduced solar radiation, elevated presence of smoke and increased atmospheric deposition of particulates and ash on the ecosystem metabolism and dissolved oxygen dynamics of small lakes. The project will make use of a network of lakes in California and Oregon along ecologically relevant gradients. Satellite remote sensing data will be compiled, in combination with ground-based air quality monitoring data to quantify smoke and particulate deposition dynamics. Several ecosystem response variables have been measured prior to the 2020 wildfire season and this project will add important short-term knowledge about fire impacts from days to months. New measurements and instrumentation will be added to ongoing measurements from 23 aquatic ecosystems. By studying basic ecosystem functioning in lakes of varying size, water clarity, and productivity, the project will ascertain the effects of smoke and ash from wildfires. Ultimately, data from this project will help characterize the spatial linkages of smoke and ash deposition from large regional wildfires. The functioning of lakes will be determined through measurements of gross primary production, ecosystem respiration, and ecosystem oxygen dynamics, including cross-seasonal linkages between autumn and winter. This will lead to a mechanistic understanding of how interactions among drivers of ecosystem function affected by wildfires at landscape scales affect responses in individual aquatic ecosystems.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.