Abstract: The study on the phototactic behavior of Daphnia carinata clone Dc42 as an indicator of chromium biotoxicity showed that the phototaxis inhibition ratio (Rpi) of D.carinata could better indicate the chromium status in water.There was a negative linear correlation between phototactic index (Ip) and Cr⁶⁺ concentration in standardized K₂Cr₂O₇ solutions (R²=0.8089,P<0.001).The detection limit of Cr⁶⁺ by Ip was 0.056 mg·L^-1,much lower than that of LC₅₀ or EC₅₀,and the mean precision index for detection reached up to 5.46%,which suggested the sensitivity,precision and reliability of this method in monitoring chemicals biotoxicity.

Key words: Acer truncatum, Flushing method, Hydraulic character