title: Population-level toxicity of the insecticide, spinosad and the nonylphenol polyethoxylate, R-11, to the cladoceran species Ceriodaphnia dubia Richard.
abstract: The effects of the natural insecticide, spinosad, and the agricultural adjuvant, R-11, were evaluated on populations of the water flea, Ceriodaphnia dubia after chronic 8-day exposures. The number of individuals used to start the chronic exposure studies (founders) and the number of offspring/surviving female were significantly reduced after exposure to spinosad concentrations ≥ 2.5 μg/L. The final number of individuals was significantly reduced after exposure to spinosad concentrations ≥ 1.0 μg/L. Population growth rate was significantly reduced after exposure to spinosad concentrations ≥ 1 μg/L. Extinction occurred (defined as negative population growth rate) after exposure to spinosad concentrations of 10 μg/L. Therefore, negative effects were observed in C. dubia after exposure to spinosad at a concentration near the chronic expected environmental concentration (EEC) of 2.3 μg/L. R-11 was much less toxic to C. dubia than spinosad. The number of founders was not significantly reduced until C. dubia were exposed to 12,000 μg/L. The number of offspring/surviving female, final number of individuals, and population growth rate were significantly reduced after exposure to R-11 concentrations ≥ 5,000 μg/L. Extinction occurred after exposure to R-11 concentrations of 12,000 μg/L which was above the EEC of 790 μg/L. These results indicate that spinosad and R-11 both have lethal and sublethal effects on C. dubia. However, spinosad appears to affect C. dubia at or near the EEC while R-11 does not negatively affect this species until concentrations are much higher than the EEC.
authors.affiliation: Department of Entomology, Washington State University, Puyallup, Washington, USA.
authors.forename: Angela D
authors.initials: AD
authors.lastname: Deardorff
authors.forename: John D
authors.initials: JD
authors.lastname: Stark
mesh_terms: D000818:Animals; D033361:Cladocera / Q000187:drug effects* / Q000254:growth & development; D004338:Drug Combinations; D005260:Female; D007306:Insecticides / Q000633:toxicity; D018942:Macrolides / Q000633:toxicity*; D010574:Pesticide Synergists / Q000633:toxicity; D011092:Polyethylene Glycols / Q000633:toxicity*; D011158:Population Growth; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D004338:Drug Combinations; D007306:Insecticides; D018942:Macrolides; D010574:Pesticide Synergists; D014874:Water Pollutants, Chemical; D011092:Polyethylene Glycols; C415329:spinosad