Synergistic sub-lethal effects of a biocide mixture on the springtail Folsomia fimetaria

- Toxicity of esfenvalerate, picoxystrobin and triclosan to Folsomia fimetaria was assessed.
- Both, the single biocides and the mixture affected recruitment stronger than survival.
- Concentration addition and independent action predictions were almost identical.
- Inhibition of recruitment after mixture exposure was stronger than predicted.
- Comparison with an earthworm study showed that responses are species-specific.

The toxicity of three biocides, esfenvalerate, picoxystrobin and triclosan, on adult survival and recruitment of juveniles was studied in the springtail Folsomia fimetaria, both in single and mixture experiments. Recruitment of juveniles was more sensitive to biocide exposure than adult survival. The concepts of concentration addition and independent action returned almost identical toxicity predictions, though both models failed to predict the observed toxicity due to synergistic deviations at high exposure concentrations. A comparison with a similar study on earthworms showed that response-patterns were species-specific. Consequently, there is no single reference concept which is applicable for all species of one ecosystem, which in turn questions the usefulness of such mixture prediction concepts in ecological risk assessment.