Interactive toxic effect and distribution of heavy metals in phytoplankton

Abstract

Assessing the interactive toxic effect of chemicals in the environment is becoming a matter of increasing public focus on and concern with ecotoxicological aspects. The purpose of this study is to find the relationship between an interactive toxic effect and distribution of heavy metals in algal cells. The green alga Chlorella ellipsoidea Gernec(IAMC-27) was cultured for 6 days in the presence of cadmium and/or chromium. Algal cells were divided into 4 fractions by centrifugation after the cells were disrupted using a French press. The amounts of the metals in each fraction were determined. The interaction effect between the two metals on algal growth was investigated. The amount of one metal taken up in the cells and the growth inhibition rate increased with the concentration of metals in the medium. The amount of one metal in the cells was increased due to the presence of the other metal. Accordingly, the growth inhibition rate also increased. The amounts of Cd accumulated in the soluble fraction and in the membrane fraction of algal cells were 50 and 20%, respectively, of the total amount in the cells. The presence of Cr changed the Cd concentration in both fractions to 40%. The amount of Cr accumulated in each fraction was almost the same in the absence of Cd. The amount of Cr accumulated in the cell wall fraction rose to 90% after 3 days of exposure and it stayed as high as 50% even at the end of the six-day study period in the presence of Cd. It was assumed that the presence of one metal influenced the distribution of the other metal in the cells, which resulted in the synergistic toxic effect. © 1994 by John Wiley & Sons, Inc..