Comparison of theCeriodaphnia dubia and MicrotoxR inhibition tests for toxicity assessment of industrial and municipal wastewaters

Toxicity tests on effluents from industrial production facilities, municipal and industrial wastewater treatment plants, and stormwater runoff were conducted with the freshwater invertebrate, Ceriodaphnia dubia, and the marine luminescent bacterium, Vibrio fischeri in the MicrotoxR test system (Microtox is a registered trademark of AZUR Environmental, Carlsbad, CA.). Percent mortalities of C. dubia in whole effluent, generated in 24- and 48-h exposure periods during the conductance of static-renewal acute and chronic tests were compared with percent reductions in light output by V. fischeri after 15-min exposure periods in the Microtox Inhibition test. A total of 16 effluent and stormwater samples from seven sources were used in tests conducted over a 3-month period. Results of the Microtox Inhibition tests correctly predicted the results of C. dubia tests for all eight nontoxic samples after both 24- and 48-h exposure periods. Of three samples that were toxic to C. dubia within 24 h, the Microtox test also detected toxicity in two of those samples. Results from tests on the remaining five samples showed that while the Microtox Inhibition test indicated the presence of toxic components after 15 min exposure, C. dubia required exposure to potentially toxic samples for 48 h before producing a toxic response.