MS Environmental Biology Capstone Project

Wildfires can directly and indirectly alter freshwater aquatic ecosystems and their resident biota. A wide range of effects is possible depending on the characteristics of the fire, ecosystem, and species. As wildfires become more frequent and intense, specifically in the western United States, understanding the mechanisms that alter biological integrity and species diversity measures is increasingly important. Our study investigated the effects of the Marshall Fire on fish and macroinvertebrate assemblages and their in-stream and riparian habitat. We hypothesized that, because of the high intensity of the fire, riparian-zone burning, and the large burn area in the drainage basin, we expected a reduction in stream quality and significant alteration of macroinvertebrate and fish communities. We used a before-after-control-impact (BACI) study design to compare pre-fire conditions to post-fire conditions at reaches of Coal Creek that were directly burned and that were downstream of the burn. We found that fish species richness decreased significantly after the fire at our burned site but increased at the downstream site. Multimetric index scores at both sites decreased post-fire yet remained above attainment thresholds indicating maintenance of biological integrity. Bare ground was lower at both sites post-fire, but vegetation cover did not decrease. Furthermore, the proportion of fine sediment size in streams increased significantly after the fire. Our results illustrate both resistance and resilience in the Coal Creek biotic communities and habitat after experiencing an extreme wildfire disturbance. Future research should focus on understanding how the effects of winter fires differ from warm season fires.