Acute and chronic ecotoxicity of carbaryl with a battery of aquatic bioassays

The ecotoxic effects of carbaryl (carbamate insecticide) were investigated with a battery of four aquatic bioassays. The nominal effective concentrations immobilizing 50% of Daphnia magna (EC50) after 24 and 48h were 12.76 and 7.47 mu g L-1, respectively. After 21 days of exposure of D. magna, LOECs (lowest observed effect concentrations) for cumulative molts and the number of neonates per surviving adult were observed at carbaryl concentration of 0.4 mu g L-1. An increase of embryo deformities (curved or unextended shell spines) was observed at 1.8 and 3.7 mu g L-1, revealing that carbaryl could act as an endocrine disruptor in D. magna. Other bioassays of the tested battery were less sensitive: the IC50-72h and IC10-72h of the algae Pseudokirchneriella subcapitata were 5.96 and 2.87mg L-1, respectively. The LC50-6d of the ostracod Heterocypris incongruens was 4.84mg L-1. A growth inhibition of H. incongruens was registered after carbaryl exposure and the IC20-6d was 1.29mg L-1. Our results suggest that the daphnid test sensitivity was better than other used tests. Moreover, carbaryl has harmful and toxic effects on tested species because it acts at low concentrations on diverse life history traits of species and induce embryo deformities in crustaceans.