Spatial and seasonal variations of antibiotic resistance genes and antibiotics in the surface waters of Poyang Lake in China

Antibiotic resistance genes (ARGs) and antibiotics in the aquatic environment raise health concerns particularly on the dispersal and persistence of antibiotic resistance. Large lakes, which serve as catch basins of anthropogenic inputs provide an ideal environment for understanding the occurrence and accumulation of ARGs and antibiotics in freshwater environments. Here, the largest freshwater lake in China, Poyang Lake, located in the developing district of Yangtze valley was used to study the characterization of the spatial and seasonal variation of both ARGs and antibiotics. Results showed that twelve tested ARGs (sul1, sul2, sul3, tetA, tetB, tetC, tetH, tetW, tetO, tetM, qnrS, and qnrB) were detected in the surface waters of Poyang Lake, with a detection frequency ranging from 19.2% to 100%, and sul2 and tetA genes were identified as potential indicators of ARG pollution in this region. Among the 11 analyzed antibiotics, sulfonamides were the predominant antibiotics with a contribution of more than 50% to the total concentrations of tested antibiotics. The total concentrations of both ARGs and antibiotics were higher in the dry season than those in the wet season. Furthermore, ARGs and antibiotics in the surface waters also varied with sampling locations, being consistently at riverine tributaries. Positive correlations were also observed between the concentrations of ARGs and antibiotics, as well as the integron gene (intI1), indicating that antibiotics and intI1 may be playing important roles in the occurrence and dispersal of ARGs in the surface waters. Lastly, our results suggest that intensive anthropogenic activities related to antibiotic usage have substantially contributed to the occurrence and persistence of ARGs and antibiotics in Poyang Lake.