SHORT-TERM TOXICITY TEST BASED ON ALGAL UPTAKE BY CERIODAPHNIA-DUBIA

A Ceriodaphnia algal uptake suppression test (CAUST) was developed for short-term toxicity screening. The test is based on the feeding behav ior of C. dubia and requires as little as 1 hour contact time between C. dubia neonates and toxicant. Before the test, neonate digestive tra cts were cleared by feeding yeast to the daphnids. Neonates were then exposed to toxicant, followed by addition of Scenedesmus subspicatus t o the bioassay vessels. Daphnids were examined under bright-field micr oscopy for presence of algae (indicated by a green-colored digestive t ract) or absence of algae. Uptake indicated no toxic effect, whereas a bsence of uptake indicated toxic inhibition. Median effective concentr ations (EC50 values) were computed based on results over a range of do sed toxicant concentrations. Results for cadmium, zinc, copper, pentac hlorophenol, phenol, cyanide, rind selected pesticides showed that CAU ST was similar in sensitivity to the standard 48-hour C. dubia acute b ioassay and was as sensitive as or more sensitive than the 1-hour I.Q. test and 30-minute Microtox.