Airborne microbes as drivers of microbial diversity on Icelandic Lava Rocks

Microbes are aerosolized into the atmosphere by wind and stochastic events and their deposition site may be up to thousands of kilometers away from the emission source. In this study, we assessed and compared the atmospheric and lithospheric microbial diversity with 16S rRNA amplicon sequencing at two geographically different Icelandic volcanic sites: a small volcanic island Surtsey and a volcanic highland Fimmvörðuháls. Around 50,000 filtered ASVs were recovered from a total of 179 samples. Analysis of the alpha and beta diversity revealed significant differences between the microbial communities of the air and the lava rocks. Airborne communities were similar between sites, but differences were found for the 1-year-old lava rocks of different compositions. The microbial communities were similar in the lava rocks of Fimmvörðuháls after 1 to 9 years of exposure. We could establish that 83% of the ASVs in the lava rocks after 1 year of exposure at Surtsey originated from surrounding local sources and 17% of the AVSs remain from unknown sources. The most abundant genera found in common between the 1-year-old lava rocks and the potential sources possess stress-resistant properties that might have helped their survival during air transportation and facilitated their colonization of the rocks.