干旱区生态环境知识资源中心

Asian dust (Rosa) events transport airborne microorganisms that significantly impact biological ecosystems, human health, and ice-cloud formation in downwind areas. However, the composition and population dynamics of airborne bacteria have rarely been investigated in downwind areas during Kosa events. In this study, air samplings were sequentially performed at the top of a 10-m high building within the Rosa event arrival area (Kanazawa City, Japan) from May 1 to May 7, 2011, during a Rosa event. The particle concentrations of bacterial cells and mineral particles were ten-fold higher during the Rosa event than on non-Rosa event days. A 16S ribosomal DNA clone library prepared from the air samples primarily contained sequences from three phyla: Cyanobacteria, Firmicutes, and Alphaproteobacteria. The clones from Cyanobacteria were mainly from a marine type of Synechococcus species that was dominant during the first phase of the Rosa event and was continuously detected throughout the Rosa event. The clones from Alphaproteobacteria were mainly detected at the initial and final periods of the Rosa event, and phylogenetic analysis showed that their sequences clustered with those from a marine bacterial clade (the SAR clade) and Sphingomonas spp. During the middle of the Rosa event, the Firmicutes species Bacillus subtilis and Bacillus pumilus were predominant; these species are known to be predominant in the atmosphere above the Chinese desert, which is the source of the dust during Rosa events. The clones obtained after the Rosa event had finished were mainly from Bacillus megaterium, which is thought to originate from local terrestrial areas. Our results suggest that airborne bacterial communities at the ground level in areas affected by Rosa events change their species compositions during a Rosa event toward those containing terrestrial and pelagic bacteria transported from the Sea of Japan and the continental area of China by the Rosa event. (C) 2014 Elsevier B.V. All rights reserved.