New Rotifer Bioassays for Aquatic Toxicology

A standard protocol was developed for assessing acute toxicity using the freshwater rotifer Brachionus calyciflorus. This protocol has several advantages over existing methods in that test animals are obtained by hatching dormant cysts, the test is highly reproducible, it has a low failure rate, and has good sensitivity to a variety of common pollutants. Cyst age up to 18 months had no effect on test animal response to toxicants. LC50s for copper and pentachlorophenol (PCP) were lower at 10 deg C and 30 deg C than at 20 deg C. B. calyciflorus LC50s were a good predictor of Daphnia magna and fathead minnow LC50s for eight common toxicants. A standard protocol using B. calyciflorus for estimating chronic toxicity of compounds in freshwater has been developed. The rotifer chronic test has several advantages over existing tests including: test animals are obtained from cysts, the test takes only 48 hours to complete, a simple algal food is sufficient for good rotifer reproduction and algae is obtained from a petri dish, the test has good sensitivity to a wide variety of common toxicants. Acute and chronic toxicity of trinitrotoluene has been characterized. The LC50 is 9.1 mg.L-1, the chronic value is 3.3 mg.L-1 and the acute/chronic ratio is 2.8, suggesting that TNT is only weakly chronically toxic. The effects of temperature on rotifer chronic toxicity over the 20 deg-30 deg C range were small.