Flowing from the ashes: Environmental DNA reveals community recovery of aquatic ecosystems after a megafire event

Anthropogenic climate change is causing shifting weather patterns and extreme natural
disturbances worldwide. In the western United States, these changes are resulting in larger, more
frequent wildfires and extreme precipitation events. In the fall of 2018, the Pole Creek Megafire
burned 610 km2 in central Utah and was immediately followed by the remnants of Hurricane
Rosa sweeping across the state. The compounded impact of these two events caused massive
ecosystem disturbances throughout the Utah Lake watershed. Utilizing environmental DNA
(eDNA) to assess the change in aquatic macroinvertebrate and microbial communities, we
processed 340 samples in a relatively rapid and cost-efficient way. Using Faith’s phylogenetic
diversity as a proxy for ecosystem stability, we found that microbial communities were either
unchanged or recovered rapidly after the disturbance event, as we saw no distinct changes or
patterns in the communities once we began sampling. The macroinvertebrates in the burned sites,
however, saw a significant decrease in diversity during the first-year post-fire. By the second
year, the sites with less than 60% catchment area burned had fully recovered, but those with
more than 60% area burned maintained decreased diversity levels. Similarly, catchment areas
with high-severity burns remained affected two years post-burn. Using eDNA as a biomonitoring
tool allowed us to gather greater breadth and depth of information regarding the impacts of a
megadisturbance at the watershed level. We recommend this as an effective tool for
understanding how changing disturbance regimes will affect ecosystems and the biodiversity
they support.