LAUSR

Antidepressants may influence the food web and alter the nitrogen cycle through top-down forces. However, the effect of antidepressants on the key nitrogen-using species in the benthic microbial food web remains unclear, particularly the resulting changes in the nitrogen transformation process within the microecosystems. Therefore, in this study, we employed DNA stable-isotope probing to detect nitrogen-converting organisms at various trophic levels and quantify the nitrogen transformation process for the first time. The input of sertraline greatly increased nitrogen-transforming microorganisms and promoted more species to participate in the nitrogen transformation process. 100 μg/L sertraline was observed to stimulate the predation of bacteria via protozoa and metazoan, increasing the total nitrogen flow flux through the microbial food web to 31.50 %, 1.32 times that of the natural condition. The results confirm that at sertraline concentrations close to the lowest observable effect concentration in the meiobenthos (100 μg/L), key components in the microbial food web were largely interfered and exerted a long-term interference on the nutrient cycle in the river sediment ecosystem. These findings confirm that sertraline has negative effects on river ecosystems from the perspective of microbial food webs and open a new line of inquiry into assessing ecological risks of antidepressants.