| Description |
Author Affiliation: Moreira RA ( Post-Graduate Program of Ecology and Natural Resources, Department of Ecology and Evolutionary Biology, Federal University of São Carlos, Rodovia Washington Luis, km 235, 13565-905, São Carlos, SP, Brazil. Electronic address: raquel.moreira87@yahoo.com.br.); Daam MA ( NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, Av. Trabalhador São Carlense, 400, 13.560-970 São Carlos, Brazil); Vieira BH ( NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, Av. Trabalhador São Carlense, 400, 13.560-970 São Carlos, Brazil.); Sanches AL ( NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, Av. Trabalhador São Carlense, 400, 13.560-970 São Carlos, Brazil.); Reghini MV ( NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, Av. Trabalhador São Carlense, 400, 13.560-970 São Carlos, Brazil.); da Silva Mansano A ( Post-Graduate Program of Ecology and Natural Resources, Department of Ecology and Evolutionary Biology, Federal University of São Carlos, Rodovia Washington Luis, km 235, 13565-905, São Carlos, SP, Brazil.); de Freitas EC ( Post-Graduate Program of Ecology and Natural Resources, Department of Ecology and Evolutionary Biology, Federal University of São Carlos, Rodovia Washington Luis, km 235, 13565-905, São Carlos, SP, Brazil.); Espindola EL ( NEEA/CRHEA/SHS, São Carlos Engineering School, University of São Paulo, Av. Trabalhador São Carlense, 400, 13.560-970 São Carlos, Brazil.); Rocha O ( Post-Graduate Program of Ecology and Natural Resources, Department of Ecology and Evolutionary Biology, Federal University of São Carlos, Rodovia Washington Luis, km 235, 13565-905, São Carlos, SP, Brazil.) |
| Abstract |
Aquatic risk assessments of pesticides in tropical countries have often been disputed for being largely based on risk evaluations conducted in temperate regions. Although pesticide sensitivity comparisons between temperate and tropical freshwater organisms have indeed not revealed consistent differences, risk assessments are currently still based on a relatively small tropical toxicity dataset. In addition, greater levels of runoff and spray drift may be expected in tropical than in temperate agroecosystems, indicating that aquatic life in edge-of-field water bodies is likely to be subjected to higher concentrations of pesticides and their mixtures. The aim of the present study was to evaluate the toxicity of Kraft 36 EC (a.i. abamectin), Score 250 EC (a.i. difenoconazole) and their mixture to the Neotropical cladoceran Macrothrix flabelligera. Laboratory toxicity tests with the individual formulated products indicated EC50-48h values of 3.1 and 659µg a.i./L given as nominal test concentrations, respectively. Mixtures of the two pesticides revealed a concentration-dependent deviation of the independent action model, with antagonism at low and synergism at high pesticide mixture concentrations. Laboratory toxicity tests were also conducted with microcosm water that was treated with the individual or mixtures through runoff or direct overspray. Microcosm tanks receiving runoff water from experimental soil plots applied with recommended doses of the individual pesticides did not show toxicity to the test organism. Microcosms that received runoff water containing the pesticide mixture, however, did cause a short-term effect on immobility. The microcosms that were treated by direct overspray of both pesticide formulations showed the most pronounced toxic effects. Study findings suggest a potential risk of these pesticides at environmentally relevant concentrations, especially when they are both present. |
