Full life-cycle toxicity assessment using rotifer resting egg production: implications for ecological risk assessment

The majority of standardized toxicity tests incorporate only a fraction of the test organism's life-cycle. However, in natural ecosystems, organisms m ay be exposed at various times during their life-cycle or throughout their life-cycle. Thus, ecotoxicological data from standardized toxicity tests is of limited ecological relevance. Existing standardized toxicity tests usin g the freshwater rotifer Brachionus calyciflorus utilize 24-h survival or 4 8-h asexual reproduction as endpoints, despite evidence that sexual reprodu ction is more sensitive. A 96-h B. calyciflorus resting egg toxicity test w as developed and used to estimate the toxicity of penta-chlorophenol (PCP) and copper. Results were compared to a variety of acute and sublethal endpo ints for both toxicants. The B. calyciflorus 96-h resting egg production NO EC for PCP of 10 mug/l was 20 times lower than the 48-h asexual reproductio n no observed effect concentration (NOEC) and 120 times lower than the 24-h acute lethal concentration 50%. The 96-h resting egg production NOEC for c opper of 2.8 mug/l was 7 times lower than the 48-h asexual reproduction NOE C and nine times lower than the 24-h acute LC50. Resting egg production was a more sensitive indicator of toxicity than several other sublethal endpoi nts as well. These results indicate that partial life-cycle toxicity tests are not sufficiently sensitive to detect ecologically relevant adverse effe cts. (C) 2001 Elsevier Science Ltd. All rights reserved.