Bioaccumulation and harmful effects of microcystin-LR in the aquatic plants Lemna minor and Wolffia arrhiza and the filamentous alga Chladophora fracta.

Although the toxic effects of cyanotoxins on animals have been examined extensively, little research has focused on their effects on higher plants and macroalgae, and the potential for bioaccumulation in the food web through plants. Two aquatic plants, Lemna minor and Wolffia arrhiza, and one filamentous alga, Chladophora fracta, were exposed to the cyanotoxin microcystin-LR. Growth of L. minor (as weight and frond number) and root length were significantly reduced and peroxidase activity was significantly increased after 5 days of exposure to concentrations of 10 and 20 microg mL(-1) microcystin-LR. Growth of W. arrhiza (as frond number) was significantly reduced after 5 days of exposure to 15 microg mL(-1) microcystin-LR. Growth and peroxidase activity of C. fracta were not affected by microcystin-LR at concentrations up to 10 microg mL(-1). L. minor also accumulated microcystin-LR up to a concentration of 0.288 +/- 0.009 ng mg(-1) wet wt. plant material over the 5 days of the experiment, equivalent to an accumulation rate of 0.058 ng mg(-1) day(-1). C. fracta accumulated a microcystin-LR concentration of 0.042 +/- 0.015 ng mg(-1) wet wt. plant material over the 5 days of the experiment, equivalent to an accumulation rate of 0.008 ng mg(-1) day(-1).