Co-contamination of metal (loid)s and antibiotics induced the enrichment of antibiotic resistance genes in the coastal industrial basin.

Sediment is the sink of antibiotic resistance genes (ARGs) in aquatic systems. The pollution of ARGs in sediments is becoming severe and complicated. However, the relationships between heavy metals/antibiotics with ARGs in sediments are unclear. Thus, we collected river sediment samples to investigate the effects of 18 antibiotics/8 heavy metal (loid)s on ARGs' contamination. Results showed that tetracycline, lipopeptide and sulfonamide were 100% detection, where tetracyclines were the most abundant, ranging from 44 ng/g to 408 ng/g dw. Meanwhile, arsenic, zinc, and cadmium were the most seriously contaminated with the concentrations of 4-812 mg/kg, 155-6158 mg/kg, 0.1-23 mg/kg, respectively. The abundance of ARGs (tetA, sul1, sul2, and qnrA) were not only closely with antibiotics, but also significantly positively correlated with heavy metals. What's more, the heavy metals had significant positive correlations with MGEs such as plasmids, integrons, and efflux pumps, suggesting that heavy metals could potentially drive the propagation of ARGs in sediments. The rand-forest model showed the heavy metal (loid)s contributed up to 70% to the ARGs pollution in sediments. This study extends our understanding of the correlation between ARGs and heavy metals/antibiotics and emphasizes the importance of considering co-existing heavy metals in the ARG pollution in coastal watersheds.