The use of biomarkers in Daphnia magna toxicity testing. III. Rapid toxicity testing of pure chemicals and sediment pore waters using ingestion and digestive enzyme activity.

In this study, 4 rapid (90 min) toxicity tests were developed using ingestion and digestive enzyme activity of Daphnia magna juveniles. Ingestion activity was assessed using fluorescent labelled latex micro-beads and digestive enzyme activity (trypsin, beta-galactosidase and esterase) was measured in homogenates using chromogenic (N-benzoyl-L-arginine-4-nitroanilide) and fluorogenic (4-methylumbelliferyl-B-D-galactoside and fluorescein diacetate) substrates. All assays and toxicity endpoints were evaluated for their potential use as routine toxicity testing tools for pure chemicals and sediment pore waters. The observed high correlation coefficients (r(2)>0.9) between the short-term toxicity values and the acute toxicity endpoint (24h EC(50)) for pure chemicals suggests that these biomarker-based assays are good predictors of acute toxicity levels to D. magna. In the sediment pore water toxicity tests, ingestion activity was generally more sensitive than the conventional endpoint, while the enzymatic endpoints were less sensitive than the 24h immobility criterion. The use and limitations of the developed toxicity tests are discussed in the light of their application in ecotoxicity monitoring programmes. (C) 1998 Elsevier Science Ltd. Air rights reserved.