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Wildland Fire Smoke Alters the Composition, Diversity, and Potential Atmospheric Function of Microbial Life in the Aerobiome
Citation:
Kobziar, L., D. Vuono, R. Moore, B. Christner, T. Dean, D. Betancourt, A. Watts, J. Aurell, AND B. Gullett. Wildland Fire Smoke Alters the Composition, Diversity, and Potential Atmospheric Function of Microbial Life in the Aerobiome. International Society for Microbial Ecology. Nature Publishing Group, London, Uk, , na, (2022).
Impact/Purpose:
Wildland fire is a newly recognized mechanism for dispersing microbes via the atmosphere and this study improves understanding of the microbial assemblages and bioaerosols mobilized by combustion processes . For the first time, unmanned aircraft systems were used to sample aerosols directly over high-intensity forest fires, allowing the identification of >1000 bacterial, archaeal, and fungal taxa unique to the smoke samples, where the vast majority of cells were inferred to be viable. The presence of bioaerosols in smoke that can serve as efficient freeze catalysts of cloud water implies that smoke could represent an important source of these aerosols. The inter- and intra-continental transport of viable microbial populations in wildfire smoke has broad implications to microbial biogeography, gene flow, the dispersal of plant, animal, and human pathogens, and meteorology.
Description:
The atmosphere contains a diverse reservoir of microbes but the sources contributing to the spatiotemporal variability of microbial assemblages have not been well constrained. To characterize wildland fire smoke as a microbial aerosol point source, we examined high-intensity forest fires in sub-alpine forests in Utah, USA. We used unmanned aircraft systems equipped with aerosol samplers to collect particulate and microbial aerosols up to 150 m directly above the combustion zone and within fresh smoke plumes. Our results show that smoke contained ~four-fold higher concentrations of DNA-containing cells (1.02±0.26 x 105 m-3) compared to air samples collected prior to ignition, with 78% of microbes in smoke inferred to be viable. Ice nucleating particle concentrations were also enriched by ~three-fold in smoke, implying that wildland fire is an important source of these meteorologically relevant aerosols. Molecular analysis of small-subunit rRNA genes showed three- and two-fold higher Hill diversities of bacterial and eukaryotic taxa, respectively, in smoke versus ambient air. The relative abundance of specific taxa also differed from those of previously documented local microbial source communities. Estimated to emit 3.71 x 1014 cells ha-1 under typical 90th percentile wildfire conditions in these forests, our results indicate that wildland biomass combustion provides a distinct, large-scale mechanism for microbial atmospheric transport. High intensity fires can eject smoke plumes that transport aerosolized microbes above the planetary boundary layer, challenging the limits of a wildfire’s biological impact perimeter and introducing the concept of smoke as a point-source for biological dispersal with global reach.
