Abstract:

By following the guideline (GB/T 27859—2011) of “Spiking Sediment in Toxicity Test on Chironomus tepperi in Sediment?Water System”, tests were carried out using mortality, emergence rate, growth rate, time for emerging, sex ratio, and yield of eggrafts and hatchability as observation targets to study chronic toxic effect of spinosad residue in sediment on larvae and eggrafts of Chironomus tepperi. It was found that growth rate of larvae and average time for female adults to emerge were positively related to spinosad concentration spiked, while survival rate and emergence rate were negatively related and average time for male adults to emerge and sex ratio of adults were not related. The tests indicate that the 28 d LC₅₀ of spinosad for Chironomus tepperi was 1 626.96 μg•kg^-1, and the EC₅₀ (half maximal effective concentration) on emergence was 1 633.53 μg•kg^-1. When the concentrations of spiked spinosad were lower than 10 μg•kg^-1, advanced emergence and higher growth rate of Chironomus tepperi could be observed as compared with the control. Eggraft yield of Chironomus tepperi was not significantly affected by spinosad in the sediment, while the number of eggs in each eggraft and the number of first-instar larvaes hatched was significantly affected.

Key words: Chironomus tepperi, spinosad, sediment, chronic toxicity