Application of Lemna species in ecotoxicological studies of heavy metals and organic biocides

Abstract Owing to their small size and easy manipulation under aseptic conditions, duckweeds (Lemnaceae) provide good material for studying the effects of toxicants and organic biocides. Applying static acute ecotoxicological tests the responses of three duckweed species to different chemicals were compared. In each species the IC 50 values of copper and Bonion biocide reached 10 mg/1 and 15 mg/1, respectively. Comparing the two Lemna species L. minor proved to be more sensitive than L. gibba . Simultaneously with the measurement of the productivity the changes in the CO 2 and O 2 exchange were also determined during the static acute tests of biocide (methylene bisthiocyanate) by means of a gas analyser (Quadrupole MS) in special growth chambers. There were no correlations between the respiration of duckweds and the concentration of biocide. Differences were found in the intensity of the photosynthesis as a function of the biocide treatment.