Acute Toxicity of Dichlorvos to Carassius auratus and the Detoxification by Rhodobacter sphaeroides

Dichlorvos(DDVP)is one of the most widely used organophosphate insecticides, with high water-solubility and high risk to aquatic animals. In order to explore the detoxification of DDVP by degrading strain to poisoned fish, the acute toxicity of DDVP to Carassius auratus was determined, and the detoxifcation by a strain of Rhodobacter sphaeroides, which has high degradation capability to DDVP was investigated. Results showed that the half lethal concentration (LC50)of DDVP to C. auratus at 48, 72 and 96h were 45.1, 30.4 and 23.3mg·L-1, respectively. The safe concentration was 2.3mg·L-1. R. sphaeroides (5 ×107CFU·mL-1)could reduce the mortality of C. auratus significantly. Adding R. sphaeroides (5 ×107CFU·mL-1)to 20mg·L-1 and 35mg·L-1 DDVP treatments reduced C. auratus mortality significantly from 40% and 100% to 0 and 15%, respectively at 96h. The degradation of DDVP was detected by HPLC in fish water with and without R. sphaeroides, respectively. The result showed that the detoxification by R. sphaeroides was mainly due to the rapid degradation of DDVP by R. sphaeroides. There were no toxic degradation products in degradation process.