Phototactic behavior in Daphnia magna Straus as an indicator of toxicants in the aquatic environment.

In this study, the phototactic behavior of Daphnia magna was investigated as a possible bioindicator for the following 11 chemicals commonly found in the aquatic environment: benzo(b)fluoranthene, mercury (II) chloride, dimethoate, lindane, linuron, MCPA, TBTO, carbon tetrachloride, thiram, 2,4,6-trichlorophenol and arsenic trioxide. Phototactic response was monitored as the movement of 7 to 8 day-old D. magna individuals. The analysis was carried out using glass test tubes divided radially into two zones, with increasing distance from a light source. For each of the compounds, different concentrations and exposure times were analyzed, and the behavior of the D. magna in each of the treatments compared to the controls in which the chemicals were not added. Using the experimental model described here, all of the 11 chemicals could be detected following exposure times of between 15 min and 48 h. The lowest concentrations detected using this technique were between 2 and 43 times lower than the LC(50) and EC(50) values reported for D. magna. The results of this study show that the analysis of phototactism is a useful method for detecting the presence of a wide range of potentially toxic chemicals found in the aquatic environment.