Microbial community responses to ceramic amendment in coastal sediments of a seasonally hypoxic bay

Eutrophication-driven sediment deterioration is a critical issue in enclosed coastal bays. A ceramic material composed of humic organic acids and calcium carbonate mesoscopic crystals has been developed for in-situ sediment remediation, generating high-alkaline environments that promote oxidative degradation of organic matter. Although its physicochemical effects have been verified through the Environmental Technology Verification (ETV) program, its influence on sediment microbial communities remains unknown. This study investigated the impact of ceramic treatment on bacterial community structure in coastal sediments of Omura Bay, Japan, a seasonally hypoxic enclosed bay, through comparison with untreated control sediments using 16 S rRNA gene amplicon sequencing. A significant increase in alpha diversity was observed in ceramic-treated sediments relative to controls, and PERMANOVA indicated significant differences in microbial community composition between the two areas. Ceramic-treated sediments were enriched in aerobic to facultatively anaerobic organic matter–degrading genera (e.g., Lutimonas , Actibacter , Aureibaculum , Saccharicrinis ) together with the concurrent enrichment of the sulfate reducer Desulfofustis and the sulfur oxidizer Thiolapillus . The concurrent enrichment of these metabolically distinct groups suggests the potential coexistence of oxidative and reductive processes within heterogeneous sediment microenvironments. In contrast, control sediments were characterized by the denitrifier Nitrogeniibacter and several uncultivated GTDB MAG-derived lineages. PICRUSt2-based functional prediction indicated higher predicted relative functional potential for sulfur metabolism, environmental sensing, and biofilm formation pathways in ceramic-treated sediments, whereas control sediments showed greater representation of central carbon metabolism pathways. These findings indicate that ceramic-treated sediments support a more diverse microbial community with distinct taxonomic and predicted functional profiles, including microbial groups associated with both oxidative and reductive processes, providing insights into the potential of ceramic materials for sediment remediation.