The calculated NOEC was 0.1 microg/L for these taxa as well as for the community. The zooplankton community was considered to be recovered after 99 days post-application. The results of this experiment were similar to those derived from mesocosm/microcosm studies performed in temperate regions. This indicates that a chlorpyrifos concentration of 0.1 microg chlorpyrifos/L could be the appropriate safe level for zooplankton community in different climatic regions. However, at treatment level of 1.0 microg/L the time required for full recovery of the affected populations (particularly Cladocera) was longer than in the other experiments performed in temperate regions.