In the western U.S., wildfires are a growing danger, largely due to climate change. They drastically change the microbial communities in our aquatic habitats, which threatens the health of ecosystems and our water supply. Courtney Gardner, assistant professor in the Maseeh Department of Civil, Architectural, and Environmental Engineering at The University of Texas at Austin, was the lead author on a recent study. This study sheds new light on how storms and disasters affect the largely unseen microbial world in our streams and rivers. Featured at ASM Microbe 2025, the study serves as a timely reminder of the enduring impact of wildfires on the health of ecosystems.
To connect initial composition of microbial communities to resilience, researchers were able to trace pre-established microbial communities in water samples collected over the course of 42 days. This participant observation was focused on gaining a better understanding of how these communities were responding to the chaos caused by the wildfires. Our results show that wildfires are not limited to terrestrial environments, but rather, catalyze deep shifts in aquatic ecosystems.
Impact on Microbial Communities
The new research run by Gardner examined what happens to microbial communities after wildfires. By sampling water before and after wildfires, the researchers were able to illustrate an increase in microbial diversity and abundance after the fires. These findings showed radical changes in the structural profiles of microbial communities.
Microbial ecosystems are responsible for many important ecosystem services, including nutrient cycling, organic matter decomposition, and water quality regulation. When wildfires happen, the influx of ash and other organic materials into water bodies can overwhelm these processes. When beneficial microbes lose ground, bad actors can run riot. This dramatic change, some say unprecedented in its scope, could have dire effects on our nation’s water quality.
Gardner’s research further emphasizes that these changes can have a domino effect on ecosystems at a much broader scale. Impaired microbial communities can severely impact fish species. These changes don’t just affect fish—other aquatic life that relies on consistent freshwater conditions to thrive are equally at risk. This study shows the importance of further exploration into these dynamics. We need to do more to really grasp the extensive effects of wildfires.
Threats to Ecosystem Balance
The implications of Gardner’s findings go way beyond microbial communities. Wildfires can drastically upset the fragile balance of entire ecosystems including fish and terrestrial habitats by changing their habitats and food webs. Microbial shifts can have dramatic impacts on water quality. This alteration may spur eutrophication, a harmful process in which excess nutrients feed algal blooms. These blooms have the potential to suck oxygen out of the water, putting fish and other aquatic life in jeopardy.
Additionally, given that wildfires are predicted to increase in frequency and intensity, their additive impacts may threaten the long-term resilience of our ecosystems. Healthy microbial populations are critical in keeping an ecosystem and the services it provides functioning stably, the researchers stress. Changes caused by wildfires may impair restoration efforts for harmed ecosystems.
The research underscores the importance of adaptive land management approaches. Importantly, these strategies should consider how terrestrial and aquatic ecosystems are connected. Wise planning will help prevent the destructive impacts of wildfires and foster resilience and recovery for both aquatic and terrestrial ecosystems.
Implications for Water Quality
Wildfires affect water quality both directly by introducing pollutants such as ash into the water supply and indirectly by altering microbial dynamics in aquatic systems. When ash and debris wash into water bodies, toxins are released. This dredging process only adds to the sedimentation and results in even more drastic declines in water quality. Gardner’s research shows that without tracking these shifts it will be impossible to manage our water resources smartly.
These findings are a further reminder of the complex connection between wildfires and aquatic ecosystems. By understanding how wildfires influence microbial communities, researchers can develop strategies to protect water quality during and after wildfire events.
This new study points to a real imperative for more proactive steps. These actions are important to impact ecosystem resiliency as the extent, intensity, and frequency of wildfires continues to increase. Meeting the challenges set forth by these increasingly frequent wildfires will take the continued efforts of engaged scientists, policymakers, and community stakeholders to build thriving, resilient ecosystems.
