[Effects of Wastewater Discharge on Antibiotic Resistance Genes and Microbial Community in a Coastal Area]

Wastewater treatment plants (WWTPs) are important sources of antibiotic resistance genes (ARGs) in aquatic environments. Mobile genetic elements (MGEs) and microbial communities are key factors that affect the proliferation of ARGs. To reveal the effects of WWTPs effluent discharge on the ARGs and microbial community in a coastal area, the structure and distribution of ARGs, MGEs, and microbial community in Shangyu (SY) and Jiaxing (JX) effluent receiving areas (ERAs) and the offshore area of Hangzhou Bay (HB) were investigated via high-throughput quantitative PCR and 16S rRNA high-throughput sequencing. The results showed that multidrug resistance genes were the most abundant ARGs across all the sampling sites. The diversity and abundance of ARGs and MGEs in the ERAs were much higher than those in the HB. Additionally, the diversities of the microbial community in the JX-ERA were higher than those in the SY-ERA and HB. PCoA showed that the distribution of ARGs, MGEs, and microbial communities in the ERAs and HB were significantly different, indicating that the long-term wastewater discharge could alter the distribution of ARGs, MGEs, and microbial communities in the coastal area. The co-occurrence pattern among ARGs, MGEs, and microbial communities revealed that 12 bacterial genera, such as Psychrobacter, Pseudomonas, Sulfitobacter, Pseudoalteromonas, and Bacillus, showed strong positive correlations with ARGs and MGEs. Most potential hosts carried multidrug and β-lactamase resistance genes.