Abstract:[Background] Extreme weather events, such as typhoons, bring transient and lasting effects on aquatic ecosystems due to strong winds and precipitation. However, very few studies have focused on the effects of typhoons on aquatic microbial communities and antibiotic resistance genes (ARGs). [Objective] To understand the effect of extreme weather on freshwater ecosystem, we analyzed the microbial communities and ARGs in urban freshwater before and after typhoon. [Methods] Water samples were collected from four sites before and after the typhoon. The effects of Lekima on the microbial communities and ARGs in recreational waters in Wenzhou were examined by metagenomic analysis in summer, 2019. In addition to the aquatic microbial communities and ARGs, the physical and chemical parameters of water samples from each sampling site were analyzed, including temperature, pH, dissolved oxygen, chlorophyll a, soluble active phosphorus, nitrate, nitrite, andammonium. [Results] The pH, dissolved oxygen, and chlorophyll a at most sites increased after the typhoon, and the typhoon had a weaker effect on Jiushan Lake than on Sanyang Wetland. The relative abundances of Proteobacteria, Cyanobacteria, and Bacteroidetes increased, while that of Actinobacteria decreased after the typhoon. At the genus level, Limnohabitans showcased significantly increased diversity and relative abundance after the typhoon. Among all the environmental factors, ammonium was the key environmental factor affecting microbial community structure. In addition, 35 opportunistic pathogen taxa were detected in all samples. The relative abundance of Pseudomonas aeruginosa, an important opportunistic pathogen, increased after the typhoon. The ARGs showed spatial (among sampling sites) and temporal (before and after the typhoon) variation. A redundancy analysis showed that water total inorganic nitrogen was the main environmental factor affecting the distribution of ARGs.[Conclusion] These findings provide new insights into how extreme weather (e.g., typhoons) influences microbial communities and ARGs in freshwater system. Typhoon landing increases the public safety risk of urban freshwater system. Therefore, the testing and quarantine should be carried out in advance to strengthen the evaluation and analysis of environmental health and safety, which will help to reduce the risk of antibiotic resistance and pathogen diffusion.
