Toxicities of antifouling chemicals and natural marine samples were evaluated by three assays, among which bioluminescence assay using freshly incubated Vibrio fischeri (V. fischeri) cells (NZ assay) and MicroTox were regarded as short-term assays, and growth inhibition assay was conducted as long-term assay. Short-term toxicity levels evaluated by NZ assay were in good agreement with those by MicroTox assay for all of the samples examined. Based on the EC 50 values of each chemical by

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... e assay, NZ assay showed prior reproducibility and similar levels of sensitivity when compared with those of MicroTox assay. On the other hand, growth inhibition assay showed lower sensitivity and reproducibility than NZ and MicroTox assays. Four kinds of antifouling chemicals, Irgarol 1051, Diuron, thiabendazole (TBDZ), and N-dichlorofluoromethylthio-N′ ′ ′ ′ ′,N′ ′ ′ ′ ′-dimethyl-Nphenylsulfamide (DCF), were detected to possess delayed toxicity from the judgments on the difference of short-term and long-term toxicities. Four out of 16 seawater samples collected in Japan showed remarkable toxicity in NZ assay, suggesting that they were contaminated by several types of antifouling chemicals. Considering time consumed, facility for operation, cost, and requirements, NZ assay was proved to be efficient for toxicity evaluations for artificial and natural samples.