Microbial Community Characterization of Nine Korean Sponge Species from Gageodo Island

Marine sponges are known to be associated with diverse and functionally specialized microbial consortia that are implicated in host metabolism, biogeochemical cycling, and bioactive compounds production. The microbiome diversity and composition of nine sponge species from the remote waters of Gageodo Island, Korea, were evaluated via full-length 16S rRNA sequencing and bioinformatic analyses. Each sponge species harbored a distinct microbial community, with differences potentially influenced by ecological factors, evolutionary history, and host–symbiont associations. The dominant microbial phyla identified across the sponge samples include Pseudomonadota, Cyanobacteriota, Acidobacteriota, Planctomycetota, and Chloroflexota, which were widely distributed across samples. In addition, the classes Gammaproteobacteria, Acidobacteriae, and Anaerolineae appeared as characteristic groups, being particularly abundant in specific sponge samples. Community structures ranged from dominance by one or two abundant taxa to more taxonomically diverse and evenly distributed microbiomes. A notable proportion of sequences were unassignable to known taxa, suggesting the occurrence of previously uncharacterized microbial lineages in these sponges. By combining host species identification with microbiome profiling, this study provides new foundations on the microbial ecology of Korean sponge holobionts, providing higher-resolution taxonomic classification, improved diversity estimates, and enhanced characterization of evolutionary relationships among symbionts. These findings may support future investigations into host–microbe interactions, potential ecological functions, and the management of marine genetic resources.