Abstract Number: 490 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract Tropospheric transport of airborne microorganisms plays an important role in microbial dispersal and has significant impacts on biological ecosystems, human life, and atmospheric processes in downwind areas. However, microbial communities in the troposphere have rarely been investigated because the direct collection of microbial cells at high altitude requires sophisticated sampling techniques. In this study, air samples at 800m and 3000 m over the Noto Peninsula in Japan were collected using a balloon and an aircraft, respectively, and that at 10m was also collected on the building of Suzu City located at north edge of he Noto Peninsula. During the sampling period at March 1, 2013, the tropospheric air mass came from Gobi desert area by westerly wind. The air samples collected at 3000m included aerosol particles significantly suggesting that winds carry aerosol particles from continental areas. After bacterial compositions were determined using 16S rDNA clone library techniques and pyrosequence analysis, bacterial communities were compared among different altitudes of 10 m, 1000 m and 3000 m. The 16S rDNA clone libraries revealed that bacterial communities at upper altitudes was mainly composed of marine species such as Cyanobacteria and Alpha-proteobacterium members, while that at lower altitudes consisted primarily of terrestrial bacterial species belonging to the phylum Firmicutes. Moreover, one phylotype of B. subtilis occupied lagers numbers of clones in the air sample at 3000 m than those at 1000m and 10m, suggesting that B. subtilis was possibly transported from continental areas. Pyrosequence analysis provided more than 8,000 sequences from each air samples. Bacterial compositions of pyrosequencing showed similar vertical-distributions of the clone libraries and included large number of minor bacterial species that have not detected from atmosphere. In summary, tropospheric air mass would contribute to the vertical dynamics of airborne bacterial communities in atmospheric column.