Co-Pollution Characteristics of Microplastics and Antibiotic Resistance Genes in the Haihe River Estuary and Bohai Sea Coastal Waters

The increasing co-occurrence of microplastics (MPs) and antibiotic resistance genes (ARGs) has led to growing ecological concerns. This study investigated the composition and spatial distribution of MPs, ARGs and microbial communities in the MP-containing membrane-retained particulate fraction of surface waters in the Haihe River estuary and Bohai Sea coastal waters, and examined their statistical correlations and co-occurrence patterns. The results showed MP abundances ranging from 150 to 1450 items/L, with pronounced hotspot accumulation in nearshore waters flanking the estuarine radial zone and polyvinyl chloride (PVC) as the dominant MP (51.95% of total MPs). The overall ARG profile remained compositionally stable, predominantly comprising peptide (8.97%), macrolide (8.92%), tetracycline (8.27%), and fluoroquinolone (8.01%) resistance genes, among which peptide ARGs exhibited a lower abundance in the estuarine radial zone and higher abundance in the nearshore waters. Correlation analysis revealed that Vulcanococcus (Cyanobacteria) positively correlated with both PVC (r = 0.73, p < 0.01) and peptide ARGs (r = 0.66, p < 0.05), suggesting a statistically significant co-occurrence pattern among PVC, Vulcanococcus, and peptide ARGs. Similarly, PA was positively correlated with Casp-actino8 and Pontimonas, which were also positively correlated with macrolide and penam ARGs. This study characterizes the co-pollution characteristics of MPs and ARGs in the Haihe estuary and Bohai coastal waters, and provides scientific evidence and dataset support for their ecological risk assessment.