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Atmospheric transport is critical to dispersal of microorganisms between habitats, and this underpins resilience in terrestrial and marine ecosystems globally. A key unresolved question is whether microorganisms assemble to form a taxonomically distinct, geographically variable, and functionally adapted atmospheric microbiota. This question is made more complex by the unique challenges of separating potential contaminants from atmospheric signal, particularly given the ultra-low biomass of air and the long durations of sampling where contamination may occur. Here we adopted a comprehensive data filtering approach to mitigate contamination and characterise inter-continental patterns of microbial taxonomic and functional diversity in air within and above the atmospheric boundary layer and in underlying soils for 596 globally sourced samples. Bacterial and fungal assemblages in air were taxonomically structured and deviated significantly from purely stochastic assembly. Patterns differed with location and reflected climate, underlying surface cover and environmental filtering. Source-tracking indicated a complex recruitment process involving local soils plus globally distributed inputs from drylands and the phyllosphere. Assemblages displayed stress-response and metabolic traits relevant to survival in air, and taxonomic and functional diversity were correlated with macroclimate and atmospheric variables. Our findings highlight complexity in the atmospheric microbiota that is key to understanding regional and global ecosystem connectivity.

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and mixing. While the 134 Cs and 137 Cs concentrations of highly contaminated surface seawater samples around the FDNPP have been studied extensively (Tsumune et al., 2012; Honda et al., 2012), relatively little information is available on radionuclide concentrations in seawater for other sea areas around the Japanese Archipelago. We previously reported low levels of 134 Cs and 137 Cs concentrations in surface water samples from the Pacific Ocean side of northeastern Japan, the Japan Sea, and the southwestern Okhotsk Sea before and after the FDNPP accident; however, the scope of these studies was somewhat cursory (Inoue et al., 2012a, b). Nonetheless, these studies illustrated the need for more extensive temporal and spatial investigations to assess the oceanic behaviors and fate of Fukushima-derived radionuclides around the Japanese Islands. We therefore used low-background γ-spectrometry to characterize the lateral variations of 134 Cs and 137 Cs concentrations in surface waters around the Japanese Archipelago in June and October 2011. These data were combined with 134 Cs deposition data (Ministry of Education,