Effects of the insecticide Dursban 4E (active ingredient chlorpyrifos) in outdoor experimental ditches: II. invertebrate community responses and recovery

This paper describes long-term effects of chlorpyrifos on macro-invertebrates and zooplankton after a single application. Crustaceans and insects showed a rapid, concentration-dependent decrease in numbers after application (direct effects). A significant increase in gastropods and oligochaetes was found, suggesting indirect effects. The start of recovery of the invertebrate populations affected depended not only on the susceptibility of the taxa, but also on ecological characteristics, such as length of the life cycle. Safe concentrations, based on no observed short-term effect levels for some characteristic indigenous taxa susceptible to chlorpyrifos, also appeared to protect the total invertebrate community in the long term.