Coastal winds alter the continental airborne bacterial diversity and pathogenicity over Chulkati Island in Sundarban, India.

Sundarban experiences diurnal offshore-onshore wind circulation that facilitates enhanced airborne bacterial loading in polluted continental air, originating from densely populated and highly polluted Indo-Gangetic Plain (IGP) through offshore wind, and reduces their abundance in onshore wind. Total suspended airborne samples are collected under offshore and onshore wind conditions, and airborne bacterial community, pathogenicity, and functional profiles are characterized using non-culture-based 16S rRNA gene amplicon sequencing. Coastal airborne bacterial loading in offshore wind (1.5 ± 0.3 × 105 m-3) is reduced by half compared to that in onshore wind (0.8 ± 0.2 × 105 m-3). Sundarban coastal winds are responsible for one-third of the variation in airborne bacterial diversity, with a higher Shannon's diversity index of 3.3 ± 0.2 in offshore winds than 2.6 ± 0.6 in onshore wind, indicating a substantial decline in airborne bacterial diversity under marine influence. Airborne pathogens associated with human, animal, and plant infections are predominant in offshore wind, whereas their abundance declines by more than threefold in onshore winds, suggesting a significant reduction in airborne bacterial diversity under marine atmospheric stressors, such as higher salinity and reflected solar radiation by the sea surface. The present study reveals that continental airborne pathogens present in polluted offshore wind, dominated by taurine and hypotaurine metabolism gene, have potential to survive in a harsh marine atmosphere and return with relatively cleaner onshore wind to the IGP via Sundarban, which has a significant impact on public health in India.