Temporal Dynamics of Bacterial and Fungal Community Composition in the Atmospheric Boundary Layer

Abstract:

There is increasing evidence for significant microbial influences on atmospheric chemistry, cloud condensation, and ice nuclei concentrations, with known health impacts, yet we have a limited understanding of the types, abundances, and spatiotemporal dynamics of bacteria and fungi in the atmosphere. Here we use culture-independent molecular approaches, including targeted gene sequencing and quantitative PCR, to characterize bacterial and fungal community composition and abundance in the atmospheric boundary layer. We present results from 32 air samples, collected via vacuum filtration at 10 m and 250 m on the Boulder Atmospheric Observatory tower (Erie, CO) between November 2013 and April 2014. Samples were collected at night, and each sample was integrated over consecutive nights for approximately two weeks. Significant temporal shifts in bacterial and fungal community composition were observed over the course of the study, corresponding to changing bacterial and fungal concentrations. Within the same sampling time periods, bacterial and fungal communities from the near-surface atmosphere (10 m) were generally similar to those aloft (250 m), although coupled temporal and altitudinal effects were observed in some cases, particularly for fungi. Overall, our results indicate that bacterial and fungal communities exhibit minimal vertical stratification throughout the nocturnal atmospheric boundary layer but show a high degree of variability on two-week timescales. This study paves the way for further research into the connections between boundary layer microbiology, atmospheric dynamics, emissions, and local meteorology.