Bioassessment of Riparian Ecosystems After Megafire in Northern Utah

Wildfire frequency and burn area in the Western United States has doubled since 1980, in some measure due to climate change. In 2018, a 610-km² megafire complex and residual storms following Hurricane Rosa triggered flash flooding and debris flows throughout the Spanish Fork River (Utah) watershed. This resulted in increased runoff, deposited sediment, and altered water chemistry. Aquatic macroinvertebrates are important in riparian and terrestrial food webs and can indicate changes in ecosystem health. To understand how increasing wildfire occurrence influences macroinvertebrate richness, we compare multiple biomonitoring metrics acquired from data collected from 6 sites in 3-month increments between August 2019 and August 2020. Three sites are burned and 3 sites are unburned. The size of the megafire allows for the testing of multiple hypotheses about ecosystem recovery across elevational diversity and vegetation gradients. We compare macroinvertebrate richness among these sites via morphological classification of subsampled D-net kick samples. We use these data to generate a new understanding of freshwater ecosystem disturbances resulting from large fire complexes and inform watershed management by quantifying the rate of recolonization of burned streams with linkage between riparian ecosystem health and macroinvertebrate abundance.