Acute and chronic toxicity of endosulfan to two Australian cladocerans and their applicability in deriving water quality criteria

Abstract

The acute and chronic toxicity of endosulfan was determined in two Australian cladocerans, Ceriodaphnia dubia and Moinodaphnia macleayi. For C. dubia, the 48-h nominal EC50 (immobilization) was 490 μg/L and the chronic NOEC for reproductive impairment was 10 μg/L. For M. macleayi, the 48-h nominal EC50 (immobilization) was 215 μg/L, and the chronic NOEC was 20 μg/L. A water quality guideline for endosulfan based on cladoceran chronic toxicity may be estimated at 2 μg/L by using an application factor of 0.1 and the LOEC value for C. dubia of 20 μg/L. A much lower guideline of 4 ng/L may be obtained if the acute/chronic ratio calculated for C. dubia is applied to the lowest LC50 value determined for an Australian fish, 0.2 μg/L in the bony bream, Nematolosa erebi. This suggests that the concentration of endosulfan for Australian waters should be less than the level of 10 ng/L given in the Australian Water Quality guidelines for (fresh and marine waters) aquatic ecosystems. Factors which may modify these conclusions under site-specific conditions are discussed.