Differences of Occurrence, Distribution, and Factors Influencing Antibiotic Resistance Genes Between Freshwater and Seawater in China

The accumulation of antibiotic resistance genes (ARGs) in aquatic systems jeopardizes public health and ecological environments. This study investigates ARGs dissemination in freshwater and seawater, focusing on the sources, prevalence and influencing factors. In freshwater, ARGs primarily originate from medical/pharmaceutical wastewaters, industrial operations, agriculture, and livestock sectors. By contrast, in addition to the above sources, seawater is contaminated by mariculture and terrestrial runoff. Comparative analysis indicates that fresh water hosts multidrug resistance, bacitracin resistance, sulfonamides, aminoglycosides, and beta-lactams, whereas seawater exhibits a wider range of ARGs encompassing sulfonamides, tetracyclines, aminoglycosides, beta-lactams, quinolones, macrolides, and chloramphenicol resistance genes. There was a stronger correlation between antibiotics and ARGs in seawater than in freshwater, especially in farmed waters. Human activities significantly contribute to ARGs pollution in both freshwater and seawater. Urbanization influences ARGs pollution in freshwater, while offshore distance and coastal economic development dictate ARGs selection pressure in seawater. This study shed lights on the current ARGs pollutant status in marine and freshwater ecosystems in China, providing a scientific foundation for water health preservation and ecosystem safeguarding measures.