The influence of simulated immigration and chemical persistence on recovery of macroinvertebrates from cypermethrin and 3,4-dichloroaniline exposure in aquatic microcosms.

Background: Chemical dissipation and organism immigration are considered important factors that influence recovery potential from perturbation of aquatic macroinvertebrates. Experiments were conducted to investigate the effect of simulated immigration on recovery of aquatic macroinvertebrates exposed in outdoor microcosms to ecotoxicologically similar concentrations of the rapidly dissipating pyrethroid insecticide cypermethrin (70 ng L(-1)) or the more persistent herbicide intermediate and degradate 3,4-dichloroaniline (10 mg L(-1)). Microcosms were covered with light-permeable mesh to prevent recolonisation.