Chronic toxicity of chlordane to Daphnia magna and Ceriodaphnia dubia: a comparative study.

Chronic toxicity of chlordane, an organochlorine insecticide, was assessed on Ceriodaphnia dubia under standardized conditions of testing. Results were compared to Daphnia magna to determine the sensitivity of the two freshwater cladoceran species to this persistent organic pollutant (POP) and to explore the possibility of using the 7-day C. dubia test as an alternative to the 21-day D. magna test in chronic toxicity assessment of POPs. The NOEC-7d value of chlordane on reproduction of C. dubia (2.9 μg/L) was much higher than the NOEC-21d value of D. magna (0.18 μg/L), attesting that the 7-day test on C. dubia was less sensitive than the 21-day reproduction test on D. magna to chlordane. However, extending the period of exposure of C. dubia to chlordane from 7 to 14 days led to a NOEC-14d value similar to the NOEC-21d value in D. magna (0.18 μg/L). This study highlights the usefulness of prolonging the exposure time of the reproduction test in C. dubia from 7 to 14 days to increase the performances of the reproduction test on C. dubia for assessing chronic toxicity of POPs.