Mixture effects of the nonylphenyl polyethoxylate, R-11 and the insecticide, imidacloprid on population growth rate and other parameters of the crustacean, Ceriodaphnia dubia.
The toxicity of the nonylphenol polyethoxylate, R-11 and the neonicotinoid insecticide, imidacloprid were evaluated on the crustacean, Ceriodaphnia dubia Richard. These compounds were evaluated separately and as a mixture because they are applied for pest control and may exist as a binary mixture in surface water. Acute mortality estimates (48h) were developed followed by population-level studies after chronic exposure. LC50s and 95% CL for R-11 and imidacloprid were 9241 (8521-9842)microg/l and 2.1 (1.1-3.4)microg/l, respectively. In the population study, C. dubia were exposed to concentrations equivalent to the acute LC25 for R-11 (8090microg/l) and imidacloprid (0.3microg/l) separately and as a mixture for 8d. The results of the chronic study indicated that R-11 had a greater impact on population parameters than imidacloprid and the mixture had a greater impact than either compound alone. For example, the total number of individuals at the end of the chronic study was 73%, 19%, and 6% of the control for imidacloprid, R-11, and the binary mixture, respectively. Additionally, exposure to R-11, imidacloprid, and the mixture resulted in 52%, 10%, and 91% reductions in population growth rate compared to the control, respectively. The results of this study indicate that when combined, R-11 and imidacloprid act in a more than additive manner. Therefore, it is important that their potential effects on aquatic organisms be evaluated together.
Chen
Xue Dong
XD
Ecotoxicology Program, Department of Entomology, Washington State University, Puyallup Research and Extension Center, Puyallup, WA 98371, USA.
Culbert
Elizabeth
E
Hebert
Vince
V
Stark
John D
JD
D000818:Animals; D033361:Cladocera / Q000187:drug effects* / Q000254:growth & development; D004305:Dose-Response Relationship, Drug; D004784:Environmental Monitoring; D007093:Imidazoles / Q000633:toxicity; D007306:Insecticides / Q000633:toxicity*; D007928:Lethal Dose 50; D009026:Mortality; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000633:toxicity; D017137:Nonoxynol / Q000633:toxicity*; D011158:Population Growth; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D014874:Water Pollutants, Chemical; D017137:Nonoxynol; C082359:imidacloprid