Abstract
The purpose of this study was to ascertain an availability of acute toxicity tests on marine phytoplankton, zooplankton and fish according to the guidelines for the toxicity tests on marine organisms described by the Fisheries Agency of Japan. The effect of Cr6+ in form of K2Cr2O7 was analyzed. The 96h-EC50 for Pavlova lutheri was 7.5 mg/L（95% confidencelimits 6.5-8.6 mg/L）and for Chaetoceros gracilis was 6.0 mg/L（95% confidence limits 5.1-7.1 mg/L）. The 24h-EC50 for nauplii of Tigriopus japonicus was 42.5±5.5 mg/L. The 96h-LC50 for Sillago japonica was 12.7±0.84 mg/L. As these effects values were at the same level as reported values, employed testing methods in this study were considered to be available for testing marine organisms. Required research work for the future was discussed and it was suggested that the data accumulation on acute and chronic effects would be essential for marine organisms for reliable estimation of PNEC（Predicted No-Effect Concentration）.
