The interaction effects of toxic chemical combinations on <i>chlorella ellipsoidea</i>

Abstract

Abstract The hazardous chemicals that have been released into the aquatic environment may disturb the balance of the aquatic ecosystem. Chemicals do not exist in single pure form, but occur in mixtures in the environment. Consequently, their effects on organisms living in the aquatic environment are primarily due to the combined toxicities. In this study, the interaction effects between chemicals such as copper, cadmium, chromium and pentachlorophenol on the growth of green algae Chlorella ellipsoidea , were investigated using a batch culture. Growth rate was a more sensitive index than standing crop at a given time for detecting the toxicity of chemicals. The EC 50 values obtained from dry weight, were higher than those obtained from ATP, chlorophyll‐a, chlorophyll‐b, carotenoid as growth indices for algal density. The toxicity of each chemical was dependent on the test period. The inhibition rate of PCP and Cu in comparison with the control for the exposure time of 24 hours was higher than that for the exposure time of 48 hours. The inhibition rate of Cr and Cd for 48 hours was higher than that for 24 hours. The toxic intensity of chemicals was, in order, PCP, Cu, and Cr, without exception. The toxicity of Cd was changeable depending upon the indices used. The method modified by Stratton (1983) and the isobologram method were used to determine the modes of interaction effects of the chemical combinations. These two methods led to the same results, with three exceptions. A synergistic effect was observed for combinations between Cr and PCP, between Cu and Cd, and between Cu and Cr; while an antagonistic effect was observed for combinations between Cd and PCP, between Cu and PCP, and between Cd and Cr within some concentration ranges.