Comparative impacts of microplastics types on enrichment and transfer of antibiotic resistance genes in aquaculture: In situ evidence

Antibiotic resistance genes (ARGs) and microplastics have been two predominant emerging contaminants in aquaculture water. There is limited research on how different types of microplastics affect the enrichment and transfer of ARGs, which hinders the scientific assessment of ecological risks posed by the combined pollution of ARGs and microplastics in aquaculture. In this study, in situ experiments were conducted to investigate the enrichment and transfer potential of ARGs on different debris (PE debris from plastic bags, PVC debris from aquaculture floating balls, and wood debris). Results showed that ARGs (such as PBP1, msbA and PvrR) exhibited strong enrichment capabilities across all debris. ARGs relative abundance peaked on PVC in the first week (2.42 ± 0.12 %) and on PE in the second week (2.35 ± 0.05 %), both significantly higher than on wood and in water (p < 0.01). The abundance of mobile genetic elements (MGEs) coexisting with ARGs on all debris types was also significantly higher than in water (p < 0.01), indicating a higher risk of horizontal ARGs transfer. Notably, PVC exhibited peak MGEs abundance in the fourth week (346.11 ± 106.03 */Gb), including various MGEs such as transposase, recombinase and integrase. Additionally, human pathogenic bacteria (HPB) carrying ARGs were significantly enriched across all debris. PVC demonstrated particularly striking enrichment, exhibiting the highest HPB abundance (83.48 ± 4.33/Gb). Taxonomic analysis revealed that HPB community on PVC was dominated by Aeromonas veronii and Pseudomonas alcaligenes. These findings suggested that PVC from floating balls poses a higher ecological risk for ARGs enrichment and transfer compared to wood and PE.