Spatial and Seasonal Structuring of Bacterial Communities and Putative Pathogen‐Associated Bacterial Taxa at Four Korean Coastal Locations

ABSTRACT

Coastal marine environments are dynamic transition zones where offshore water masses and terrestrial inputs shape microbial community structure. However, standardized comparisons of bacterial communities across geographically distinct Korean coastal waters remain limited, constraining the development of microbial baselines for long‐term monitoring. Surface seawater bacterial communities from four Korean coastal locations were analysed using 16S rRNA gene amplicon sequencing. Total bacterial communities and putative pathogen‐associated bacterial taxa (PPB) assemblages differed among the four sampled locations and between the March and September sampling periods. PERMANOVA revealed significant effects of sampling location, sampling period and their interaction on community composition. Although Pseudomonadota dominated across all sampled locations, class‐ and genus‐level community compositions differed markedly among sites. Vibrio was a major component of PPB assemblages, while SIMPER analysis indicated that compositional differences among the sampled locations were associated with variation in combinations of co‐occurring taxa. Putative species‐level assignments further suggested location‐associated distribution patterns among dominant PPB taxa. Despite the absence of concurrent environmental metadata, these findings provide preliminary location‐specific baseline data for future coastal microbial monitoring and studies of environmental change.