Influence of antidepressants on stream microbiota: Consequences for leaf itter breakdown and nutrient cycling

As an emerging pollutant, antidepressants in wastewater have received extensive attention due to their metabolic stability and antimicrobial activity in aquatic systems. However, the scarcity of experimental data limits the validation of their potential impacts on ecosystem functionality. This study examined the effects of fluoxetine and amitriptyline (0–100 ng L −1 ) on microbial decomposers in stream ecosystems. These two antidepressants exhibited different effects on the process of leaf litter decomposition. Fluoxetine at 1 ng L −1 inhibited the dominance of functional bacteria ( Caulobacter and Flavobacterium ) and cellobiohydrolase activity, significantly reducing the leaf decomposition rate by 11.5%. Notably, amitriptyline at 10 ng L −1 promoting this ecological process by enhancing fungal biomass and most enzyme activities, and increasing the abundance of functional fungi ( Anguillospora and Setophaeosphaeria ). Nevertheless, when amitriptyline concentrations exceeded 10 ng L −1 , nitrogen-limitation was observed in microbial decomposers. These findings illustrate the complexity of the aquatic microbial community in responding to external factors, underscoring the importance of further research into the effects of antidepressants on the nutrient cycling and organic matter dynamics of ecosystems.