Linking Fire, Food Webs, and Fish in Stream Ecosystems.

Area of Science:

• Ecology
• Environmental Science
• Aquatic Ecosystems

Background:

• Wildfire regimes are shifting, raising concerns for aquatic ecosystems and fish populations.
• Predicting fish responses to wildfires is complex due to multiple interacting pathways.
• Whole-ecosystem approaches, like food web modeling, are valuable for understanding these complex interactions.

Purpose of the Study:

• To apply a dynamic food web simulation model to assess wildfire impacts on stream ecosystems.
• To investigate how wildfire severity influences short- and long-term biomass dynamics of periphyton, invertebrates, and fish.
• To identify key factors driving aquatic ecosystem responses to wildfires in headwater streams.

Main Methods:

• Utilized a dynamic food web simulation model to link trophic dynamics with wildfire effects.
• Simulated wildfire impacts on periphyton, aquatic invertebrates, and fish biomass.
• Analyzed responses across different fire severities, time scales, and trophic levels in western Pacific Northwest streams.

Main Results:

• Wildfires often increased modeled periphyton, invertebrate, and fish biomass in the short and long term.
• Modeled responses varied significantly in direction, magnitude, and duration based on fire severity, time since fire, and trophic level.
• Water temperature, canopy cover, riparian shading, and turbidity were sensitive factors influencing response trajectories.

Conclusions:

• Wildfire impacts on aquatic ecosystems are complex and context-dependent, leading to diverse responses.
• Food web modeling is a useful heuristic tool for understanding fire-ecosystem-fish linkages.
• Identifying specific contexts where fires may negatively impact fish is crucial for resource management.