Silver nanoparticles aggravated clothianidin-induced toxicity toward Limnodrilus hoffmeisteri

The extensive application of silver nanoparticles (AgNPs) has resulted in their significant release into aquatic environments, leading to a high likelihood of co-occurrence with other contaminants. Among these, pesticides represent one of the most prevalent groups in aquatic systems. However, the combined effects of AgNPs and pesticides on aquatic organisms, especially benthic species, remain poorly understood. This study comparatively assessed the joint toxicity of AgNPs and clothianidin (CLO), a widely used neonicotinoid insecticide, on Limnodrilus hoffmeisteri under 24-h acute exposure in a water-only system and 14-d subacute exposure in a sediment-water system. The results demonstrated that AgNPs and CLO demonstrated synergistic lethality toward L. hoffmeisteri under acute exposure, partially attributed to CLO-facilitated dissolution of AgNPs and exacerbated oxidative stress upon co-exposure. Transcriptomic analysis further revealed that CLO exposure upregulated the genes associated with cellular respiration and protein synthesis/degradation; however, these adaptive responses were suppressed by the presence of AgNPs, thereby weakening the worms' tolerance to CLO. Under subacute exposure, AgNPs alone exhibited negligible toxicity but enhanced CLO bioaccumulation in the worms, resulting in intensified oxidative stress and ultimately aggravating CLO-induced growth inhibition and neurotoxicity in L. hoffmeisteri. These results collectively revealed that AgNPs could synergistically amplify the toxicity of CLO toward L. hoffmeisteri in both water-only and water-sediment systems. The findings of this work contribute to a comprehensive understanding of the ecological risks associated with the co-occurrence of AgNPs and pesticides.