Ecotoxicity of herbicide carfentrazone-ethyl towards earthworm Eisenia fetida in soil

Herbicides pose a potential threat to the soil biodiversity and health. Carfentrazone-ethyl (CE), a triazolinones herbicide, is increasingly used in agricultural production. Its non-target toxic effects on soil microorganisms and soil enzymes are reported recently. However, the sublethal toxicity of CE on soil invertebrates like earthworms is not yet known. Therefore, in this work, the sublethal toxic effects of CE (0.05, 0.5, and 5.0 mu g/g in soil) on the soil earthworm (Eisenia fetida) were evaluated using a battery of biomarkers including reactive oxygen species (ROS), enzyme (superoxide dismutase-SOD, catalase-CAT, peroxidase-POD, and glutathione S-transferase-GST) activities, malondialdehyde (MDA) contents, histopathological and DNA damage. Results indicated that CE increased ROS contents, enzyme activities, and MDA contents in the short-time (14 d), thus, causing a slight oxidative stress to E. fetida. However, the toxic effects of CE on earthworms gradually disappeared after 14 days. The CE did not cause histopathological and DNA damage in earthworms. Integrated Biological Response index (IBR) indicated that both concentration and exposure time of CE regulated its sublethal toxicity on earthworms. In conclusion, herbicide CE is safe to soil invertebrate earthworms when applied at the recommended doses. Our results contribute to the current understanding of CE effects on soil earthworms, and can be useful in developing soil health strategies under agrochemical use.