Effect of cyanobacterial bloom proliferation on antibiotic resistance genes in the sediments of a eutrophic lake.

Antibiotic resistance genes (ARGs) represent an emerging pollutant of increasing concern. In this study, we analyzed the composition and spatiotemporal variation of ARGs in the sediments of eutrophic Chaohu Lake, China, using a metagenomic method. A total of 22 ARGs and 199 ARGs subtypes were detected, with the most prevalent subtypes being multidrug (57.720 %) and rifamycin (21.781 %). A higher abundance of ARGs in Chaohu Lake was observed (p < 0.05) during winter and spring owing to multiple factors, including variations in seasonal inputs and hydraulic conditions, occurrence of cyanobacterial blooms, and changes in ARGs host bacterial communities. Spatially, a higher abundance of multidrug was observed in sediments near the Nanfei River outlet, which flows through urban areas; whereas higher levels of bacitracin were observed in sediments near the Zhao River outlet, which flows through agricultural areas. Cyanobacterial blooms and declines change the sediment physicochemical properties, endogenous phosphorus contents, microbial communities, and seasonal ARGs distribution. Correlation and collinearity analyses indicated that ARGs were transferred horizontally via mobile genetic elements (MGEs). High-risk ARGs in Chaohu Lake were observed at a very low proportion, although certain ARGs presented health risks in the western lake during spring. In this study, we highlight the interactions between cyanobacterial blooms and variations in ARGs in Chaohu Lake and provide novel insights into ARGs dynamics in eutrophic freshwater ecosystems.