Collaborative Research: RAPID: lake ecosystem responses to fire along gradients of burn characteristics and hydrologic connectivity

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High-quality water is needed for sustaining all life on Earth. Different types of pollution, however, can reduce water quality and harm the plants, animals, and people that depend on water to live. Specifically, recent wildfires across the U.S. may reduce water quality in several ways. For example, ash from wildfires can end up in lakes and rivers, potentially harming aquatic organisms and drinking water supplies. In this project, a group of researchers will study water quality of northern Minnesota lakes after the 2021 Greenwood Fire. This wildfire burned a large part of Superior National Forest in fall 2021, including areas near 28 lakes. The researchers expect that after spring snowmelt or rain, ash and large pieces of burned plants will wash into these lakes and reduce water quality. They will visit lakes five times from spring to late summer of 2022 to document any water quality changes following the Greenwood Fire. Results of this study will help water managers in Minnesota and elsewhere predict how water quality in lakes and reservoirs may change after future wildfires. This project will also help people who live near lakes understand how the water activities they care about, such as fishing and boating, may be affected by future wildfires.Although wildfire activity is increasing across the U.S. and concern is mounting over fire effects on water resources, few studies have documented fire effects on lake ecosystems. At 10844 ha in size, the 2021 Greenwood Fire in Superior National Forest was the largest lightning-caused Minnesota wildfire in 10 years and covered all or parts of 28 lake watersheds through October 2021. This project assembled an integrative group of aquatic ecosystem, landscape, and fire ecologists to study the physical, chemical, and biological responses of northern Minnesota lakes to the Greenwood Fire. The researchers hypothesized that (1) lake responses will vary proportionally to the percent watershed burned and between drainage vs. isolated lakes and (2) post-fire temporal trajectories will vary according to major hydrologic events (e.g., snowmelt, precipitation). Both hypotheses are being tested using Bayesian approaches (i.e., information theoretic modeling and model choice procedures). Approximately 15 lakes are being sampled each in (1) burned and (2) unburned control watersheds beginning after spring snowmelt, a critical time for the delivery of nutrients and materials from the burned landscape to lakes, and throughout summer 2022.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.