The 12th International Conference on Water Resource and Environment (WRE 2026)

Abstract: Microplastics are persistent marine contaminants that provide substrates for microbial colonization, potentially altering coastal microbial communities and posing health risks in aquaculture systems. This study examined harmful microbiota associated with microplastic biofilms and assessed the intestinal effects of environmentally relevant exposure to polyester microplastics in fish. Biofilms developed during 21-day field incubations in marine waters exhibited high taxonomic diversity and marked spatiotemporal variation, despite generally low abundances of potentially pathogenic microorganisms. Community composition was primarily governed by polymer type and further influenced by local water-use conditions. Histological assessment and multi-omics profiling revealed reduced intestinal mucus secretion and time-dependent host–microbiome responses following exposure. On day 3, host transcriptomes indicated increased energy metabolism and suppression of detoxification-associated pathways. By day 7, epithelial maintenance and anti-inflammatory responses were disrupted. Exposure also transiently enriched potential pathobionts and activated microbial antioxidant biosynthesis pathways, suggesting both exploitative and cooperative host–microbe interactions under particulate stress. Although overall dysbiosis was limited, impaired gut barrier function and disrupted homeostatic regulation suggest greater vulnerability during prolonged exposure. These findings highlight the importance of considering both plastisphere microbial communities and host intestinal responses when evaluating microplastic risks in marine aquaculture, while identifying priorities for longer-term research into fish health and aquaculture sustainability.