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High-intensity Forest Fires Emit High Concentrations of Diverse, Viable, and Ice-Nucleating Bioaerosols
LEDA KOBZIAR, David Vuono, Rachel Moore, Timothy Dean, Doris Betancourt, Adam Watts, Brent Christner, Johanna Aurell, Brian Gullett, Adam Kochanski, Ali Tohidi, University of Idaho College of Natural Resources
Abstract Number: 478
Working Group: Wildfire Aerosols
Abstract
The atmosphere is known to harbor diverse and active microorganisms. However, the contribution of wildfire smoke as a vector for bioaerosol dispersal is unknown. To address this knowledge gap, we conducted the first molecular and cellular characterization of wildland fire smoke from high-intensity forest fires at the Fire and Smoke Model Evaluation Experiment (FASMEE) in Fishlake National Forest, Utah. Using unmanned aerial systems (UAS) to sample bioaerosols directly above the forest combustion zone, our results show that fire aerosolizes diverse and viable assemblages of microorganisms that are distinct from background aerosols, and that have ice nucleating potential three-fold above background levels. Nearly four times as many DNA-containing cells were found in smoke compared to ambient air, with 79% inferred to be viable. Both total and biological ice nucleation potential were higher in smoke at temperatures -8 to -15 °C. Molecular reconstruction of microbial assemblages from 16S and 18S rRNA genes as well as fungal ITS sequences show that effective diversity of bacterial taxa was twice as high in smoke than in ambient air. Ordination techniques show that ambient and smoke bacterial assemblages differed significantly. Our results indicate that living microbes constitute a non-trivial portion of the aerosols in smoke produced by high intensity wildland fires, and therefore may have impacts on weather, atmospheric chemistry, and the dispersal of human or plant pathogens. Such fires are capable of ejecting smoke plumes above the planetary boundary layer, challenging the concept of a wildfire’s perimeter of impact and introducing the possibility of smoke as a biological dispersal agent with global reach.