Abstract:

As the first, second and third trophic levels in the aquatic ecosystem, Chlorella vulgaris, Dqohnia magna, and Barchydanio rerio are important members of the simple aquatic food chain and participate in the material cycle and energy flow in the aquatic ecosystem. To elucidate the toxic effects of methomyl on aquatic organisms in different ecological niches along the food chain, the acute toxicity effects of methomyl on Chlorella vulgaris, Dqohnia magna, Barchydanio rerio had been done by using semi-static water contacting acute toxicity method. The results showed that the 96 h EC₅₀ of methomyl to Chlorella vulgaris was 6.76 mg/L. The 24 h LC₅₀, 48 h-LC₅₀ and 96 h-LC₅₀ of methomyl to Dqohnia magna were 57.37 μg/L, 22.23 μg/L and 12.58 μg/L, respectively. The 24 h LC₅₀, 48h-LC₅₀ and 96h-LC₅₀ of methomyl to Barchydanio rerio were 8.64 mg/L, 5.00 mg/L and 2.12 mg/L, respectively. According to the grading standard of toxicity assessment for pesticide, methomyl was middle toxic to Chlorella vulgaris, extremely high toxic to Dqohnia magna, and high toxic to Barchydanio rerio, respectively. And therefore methomyl could cause the acute poisoning death of Chlorella vulgaris, Dqohnia magna and Barchydanio rerio in the natural environment. The safe concentrations of methomyl to Chlorella vulgaris, Dqohnia magna and Barchydanio rerio were 0.676 mg/L, 1.26 μg/L and 0.212 mg/L, respectively. And the toxicity of methomyl to Chlorella vulgaris, Dqohnia magna, Barchydanio rerio followed the order of Dqohnia magna> Barchydanio rerio> Chlorella vulgaris.

Key words: methomyl, acute toxicity, aquatic food chain, Chlorella vulgaris, Dqohnia magna