| 研究実績の概要 |
Seawater and aerosol samples were collected in the western North Pacific (WNP) during the KH23-3 cruise of RV Hakuho-maru in July 2023. We firstly analyzed the samples collected over the Bay of Bengal (BOB) and the southern Indian Ocean (SIO) during KH18-6 cruise to test methodological feasibility. To this date, rather sparse observations exist on bacterial characterization in the marine aerosols from the pelagic oceans, as is the case for WNP, BOB and SIO. Towards this, we conducted bacterial profiling in coarse and fine mode (<2.5 um cutoff) aerosol samples from the BoB and the SIO during late autumn. Over the BoB, Firmicutes dominated the abundance in coarse particles and are influenced by the terrestrial inputs from the Southeast Asia (i.e., evident from the back trajectories). Furthermore, bacterial communities over the SIO were found to be of marine origin and dominant phyla were totally different from those over the BoB. Alpha diversity revealed that bacterial communities in the coarse particles are somewhat complex than those in the fine mode. Notably, the beta diversity of the bacterial communities in the coarse and fine particles varied with the latitude. Our results highlight that prevailing terrestrial winds lead to the dominance of land derived bacteria which creates the regional differences in the long-range microbial exchange, especially in the coarse particles over the remote marine atmosphere.
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