Evaluation of alternative and standard toxicity assays for screening of environmental samples: Selection of an optimal test battery

Six muniaturized alternative assays (called microbiotests) and three standard toxicity tests were used for a comparative study based on the evaluation of acute toxicity of fifty environmental samples. The test species used in the alternative assays were microalga Raphidocelis subcapitata, crustaceans Thamnocephalus platyurus and Ceriodaphnia dubia, rotifer Brachionus calyciflorus,protozoan Spirostomum ambiguum and bacterium Vibrio fischeri. The standard toxicity tests utilized microalga Raphidocelis subcapitata, crustacean Daphnia magna, and fish Poecilia reticulata as the test organisms. The study compared the ability of bioassays to detect acute toxicity, relative sensitivity of the six microbiotests with regard to three standard toxicity tests, and similarity in their sensitivity to fifty samples. Algal bioassays were the most sensitive tests. Ceriodaphnia dubia and Spirostomum ambiguum detected acute toxicity in the majority of samples (in 62–72%). Vibrio fischeri showed a specific sensitivity pattern that was associated neither with algal nor with animal tests. The other species formed the least sensitive organisms, having similar sensitivities. A battery of three to four alternative assays was selected on the basis of the statistical analyses, sensitivity comparisons and general conditions for the selection of a test battery member like incorporation of different trophic levels or complementation of assays in a battery. Therefore, miniaturized algal assay, rotifer or crustacean microbiotest, bacterial test and possibly protozoan microbiotest could represent an optimal battery of alternative asaays for the toxicity evaluation of fifty environmental samples presented in this study.