The combined pollution of imidacloprid and glufosinate-ammonium aggravates toxicity on Hydrilla verticillata and epiphytic microbial community.

The combined effects of imidacloprid (ICD) and glufosinate-ammonium (GLAM) on submerged plants and epiphytic microbial community remains unclear, despite the frequent co-occurrence of these pesticides in aquatic environments. In this study, a 24-day experiment was conducted to examine changes in water quality, plant physiology, and epiphytic microbial communities in Hydrilla verticillate-dominated wetlands under ICD alone or together with GLAM. Results showed that GLAM+ICD induced greater oxidative stress and a stronger antioxidant response in H. verticillata compared ICD alone, demonstrating that the mixtures exacerbated ecotoxicological effects on plant. Compared to ICD, many micro-biomarkers were obtained in ICD+GLAM, including Bacteroidota, Comamonadaceae, Proteobacteria and Cocconeis. Redundancy analysis indicated that the ICD concentration was correlated positively to Stigeoclonium, Closterium and Cocconeis, but negatively related with Oedogonium and Chloromonas, GLAM is opposite to ICD. More complex interkingdom interactions among bacteria and eukaryotes were observed in high concentration MIX treatment group compared to others. Co-occurrence networks analysis further demonstrated that GLAM and ICD changed microbial interactions within epiphytic biofilm, and impaired the stability and function of the microbial communities. These results underscore that the combined presence of ICD and GLAM poses a significant ecological risk to Hydrilla verticillate-biofilm system in agricultural regions.