Abstract
Microorganisms are essential constituents of ecosystems. To improve our understanding of how various factors shape microbial diversity and composition in nature it is important to study how microorganisms vary in space and time. Factors shaping microbial communities in ground level air have been surveyed in a limited number of studies, indicating that geographic location, season and local climate influence the microbial communities. However, few have surveyed more than one location, at high latitude or continuously over more than a year. We surveyed the airborne microbial communities over two full consecutive years in Kiruna, in the Arctic boreal zone, and Ljungbyhed, in the Southern nemoral zone of Sweden, by using a unique collection of archived air filters. We mapped both geographic and seasonal differences in bacterial and fungal communities and evaluated environmental factors that may contribute to these differences and found that location, season and weather influence the airborne communities. Location had stronger influence on the bacterial community composition compared to season, while location and season had equal influence on the fungal community composition. However, the airborne bacterial and fungal diversity showed overall the same trend over the seasons, regardless of location, with a peak during the warmer parts of the year, except for the fungal seasonal trend in Ljungbyhed, which fluctuated more within season. Interestingly, the diversity and evenness of the airborne communities were generally lower in Ljungbyhed. In addition, both bacterial and fungal communities varied significantly within and between locations, where orders like Rhizobiales, Rhodospirillales and Agaricales dominated in Kiruna, whereas Bacillales, Clostridiales and Sordariales dominated in Ljungbyhed. These differences are a likely reflection of the landscape surrounding the sampling sites where the landscape in Ljungbyhed is more homogenous and predominantly characterized by artificial and agricultural surroundings. Our results further indicate that local landscape, as well as seasonal variation, shapes microbial communities in air.
Highlights
IntroductionSpatial and temporal variation influence the composition and abundance of microorganisms in the environment (Bardgett et al, 1999; De Vries et al, 2012; Tedersoo et al, 2014; Van der Gucht et al, 2007)
Spatial and temporal variation influence the composition and abundance of microorganisms in the environment (Bardgett et al, 1999; De Vries et al, 2012; Tedersoo et al, 2014; Van der Gucht et al, 2007). Microorganisms adapting to these variations have allowed multiple species to coexist over time, resulting in species having different abundancies over seasonal cycles; exemplified in soil where seasonal fluctuations in available resources influence fungal and bacterial community composition (Bardgett et al, 2005; Bardgett et al, 1999)
Over the two locations and the two years studied, we observed a large number of taxa (230 bacterial, 136 fungal and 84 plant orders) (Table S3, File S1), suggesting that the air filters have stored information on a large diversity of organisms
Summary
Spatial and temporal variation influence the composition and abundance of microorganisms in the environment (Bardgett et al, 1999; De Vries et al, 2012; Tedersoo et al, 2014; Van der Gucht et al, 2007). Microorganisms adapting to these variations have allowed multiple species to coexist over time, resulting in species having different abundancies over seasonal cycles; exemplified in soil where seasonal fluctuations in available resources influence fungal and bacterial community composition (Bardgett et al, 2005; Bardgett et al, 1999). Studying how local environmental and temporal variation affect airborne microbial communities is challenging. Microorganisms may disperse over very long distances (Barberan et al, 2015; Smith et al, 2013), which may further complicate the analysis of local effects
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