Acute toxicity bioassay using Daphnia obtusa as a test organism

The introduction of the cladoceran Daphnia obtusa as a test organism in toxicity bioassays was considered. Development of bioassay included strain isolation, culture conditions, and toxicity test adaptation. Acute toxicity tests for Cr(VI), Mn(II), Cu(II), Cd(II), and Hg(II), phenol, sodium dodecyl sulfate, methanol, ethanol, and paraquat at 24 and 48 h of exposure show a sensitivity within the range reported for other cladocerans or fish. Sensitivity to carbaryl was higher than that found for fish. These results and the spread distribution of the species in the South of South America makes the bioassay a possible good option for the monitoring of toxicants in freshwater systems in the region. © 1996 by John Wiley & Sons, Inc.