As a typical example, BLI changes of V. fischeri in the presence of CuSO4 or Ziram were shown in Figures 2 a or 2b, respectively. Their reductive effects on the BLI values of V. fischeri were enhanced with an increase of incubation time. Toxic effects by different concentrations of CuSO4 and Ziram were recognized after 20-30 min of incubations in the presence of 0.20 and 0.27 mgl_1, respectively, from which the authors selected 30 min of incubation to judge the BLI changes of V. fischeri in the later sections due to the clearer difference of toxicity than that of 20 min or less. From the different reduction rates of BLI between samples and controls, they calculated the EC50 values for each single chemical (Table 1). Based on the EC50 values of respective antifouling chemicals, the authors classified them into three groups. The first group is highly toxic with low EC50 values (<0.75mgl -1), and is as follows: tributyltin chloride (TBT-Cl), Zn-pt, Cu-pt, CuSO4, Ziram, SEA-NINE 211, and TPBP. The second one shows medium toxicity, with EC50 values ranging from 8.5 to 12.8 mglfor IPBC and Diuron. The third group consists of DCF and Irgarol 1051 with low toxicity (>30mglof EC50 values). Among highly toxic chemicals, it is interesting to note that most of them contain the metal elements in their respective molecular structures. On the other hand, toxicity ranking of these chemicals detected in the present assay is consistent with the previous data reported through the analyses of various kinds of bioassay systems, which certifies that the present assay system possesses high reliability and sufficient sensitivity to detect the toxi-city of organic chemicals.
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