SRP488848 PRJNA1074519 Short-term exposure to triclocarban alters microbial community composition and metabolite profiles in freshwater biofilms Triclocarban (TCC), an emerging contaminant in water environments, threatens aquatic ecosystems, yet its impacts remain insufficiently elucidated. This study investigates the effects of TCC exposure on mature freshwater biofilms. TCC was found to inhibit biofilm activity by examining the surface morphology and identifying live/dead cells of biofilms. The responses of the biofilm microbial community and metabolites to TCC were investigated. The results indicate that the biofilm bacterial community structure was altered upon TCC exposure at both concentrations. Notably, functionally bacterial groups associated with carbon cycling were compromised, whereas the relative abundance of bacterial groups involved in nitrogen cycling was increased. Metabolomic analysis highlights significant disruptions in carbon metabolism-related pathways induced by TCC. Despite acute toxicity, biofilms exhibit regulatory responses by shaping amino acid and lipid metabolism to mitigate environmental stresses. Overall, short-term exposure to TCC produced acute toxicity to biofilms, but biofilms were able to regulate community structure and metabolic levels to maintain oxidative homeostasis and retain activity. Importantly, different TCC concentrations induce diverse toxicity mechanisms and detoxification strategies in biofilms. This study provides a better understanding of risk assessment and policy control of TCC in water environments.