INTERACTION EFFECT, FOOD EFFECT, AND BIOACCUMULATION OF CADMIUM AND CHROMIUM FOR THE SYSTEM DAPHNIA-MAGNA CHLORELLA-ELLIPSOIDEA

In this study Chlorella ellipsoidea was used as food for Daphnia magna in order to investigate the food effect on the toxicity. The effect w as found to vary depending on the toxicant used, on the concentration of the toxicant in the water, and on the duration of the exposure. We conducted acute mortality tests with a duration of 1-4 days. Cadmium a nd chromium were used as toxicants. The toxicity increase due to the p resence of food was more prominent for Cr than for Cd. We also investi gated the interaction effect of the two heavy metals on Daphnia in the absence of food. That effect was found to be either additive or antag onistic depending on the concentrations used. There were more cases of addition than antagonism. Finally we checked the toxicant content in the body of Daphnia after two days of exposure. It was found that the increased bioaccumulation lead to the death of the animals. The bioacc umulation experiments gave us data to support assumptions concerning t he food effect and the interaction effect. (c) 1993 John Wiley and Son s, Inc.