How wildfire affected aquatic invertebrates in Yellowstone National Park, Wyoming

Bish, Cody
Tronstad, Lusha
Wildfire severity is predicted to increase with global climate change. Wildfire may affect stream fisheries by altering their main food source, aquatic invertebrates. We were able to investigate how the density and biomass of aquatic invertebrates changed after wildfire, because a wildfire unexpectedly started after collecting samples for 1 year. Therefore, we collected invertebrates one summer before the wildfire, and two summers post wildfire. We used a Hess sampler to collect invertebrates every 2 to 4 weeks in Cub and Little Cub Creeks, Yellowstone National Park. The samples were sorted, counted, measured, and identified under a dissecting microscope. The summers after the wildfire, invertebrate density (30,000 ind/m2) decreased compared to pre fire density (52,000 ind/m2). Invertebrate density may have decreased post fire due to flooding that occurred, because the lack of primary producers decreased water storage in the watershed. The second summer after the wildfire, Plecoptera (2x) and Ephemeroptera (1.5x) increased densities, while Diptera densities decreased. Conversely, biomass increased both years post fire (500 mg/m2 before fire vs. 860 mg/m2 after fire). Despite densities decreasing post fire, higher invertebrate biomass may be available for fish to consume.
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