AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Seasonal Variability in Bacterial and Fungal Diversity of the Near-Surface Atmosphere across Urban and Rural Sites
ROBERT M. BOWERS, Nicholas Clements, Joanne B. Emerson, Christine Wiedinmyer, Michael Hannigan, Noah Fierer, University of Hawaii
Abstract Number: 177 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract Bacteria and fungi are present throughout Earth’s lower atmosphere. These airborne microbes are highly diverse and likely originate from a mixture of source environments. Microbial cells in the atmosphere are just beginning to be recognized as an important component of total atmospheric aerosol loads. Given that some airborne microbes may act as direct human pathogens while others likely trigger seasonal allergies and asthma, a better understanding of airborne microbial ecology will help us understand their roles in human health and atmospheric dynamics. To address these knowledge gaps, we performed a comprehensive analysis of airborne microbes across time, space and aerosol size fraction. We characterized total microbial abundances (via flow cytometry) and bacterial and fungal diversity (via high-throughput sequencing) at an urban and rural site in the Colorado Front Range over a one-year time period. Samples were collected at weekly intervals across the coarse (PM$_(10-2.5)) and fine (PM$_(2.5)) aerosol size fractions. Microbial concentrations were on average 1 x 10$^5 cells m$^(-3), showing little variability over time, city or aerosol size fraction. However, microbial community composition was much more dynamic. Fungal 18S rRNA relative abundances peaked in late spring to early summer especially in the coarse size fraction, and bacterial diversity peaked during the late summer, suggesting that a complex set of environmental factors including changes in atmospheric dynamics and available sources influences the composition of airborne microbial communities. To expand on this, we used a bacterial source tracking approach to determine likely sources of bacteria to the atmosphere. We tracked airborne bacteria to leaves and soils throughout most of the year, however cow fecal material was also an important source of airborne bacteria in the Greeley air samples during the fall and spring months. Taken together, airborne microbes are an important yet understudied component in aerosol research that should be integrated into future surveys of the atmosphere.