Validation of duckweed microbiological test for assessing hazardous substances

For this study, we used modified EN ISO 20079. The modificationconsists in application of polystyrene macroplates, with the advantageof requiring low sample volumes for the test (10 ml). Lemna minorwas cultivated as a monoculture by various dosesof chemicals for seven days. The aim of our work was to compare theacute toxicity (168hEC50) obtained from conventional testing (100 ml)and from microbiological tests (10 ml) using reference toxicants:potassium chloride and 3.5 – dichlorphenol. The resulting value168hEC50 for potassium chloride using conventional test was 9.78 g.l-1 and for 3.5 – dichlorphenol it was 5.71 mg.l-1. The resulting valuesfrom microbiological tests were 8.69 g.l-1 and 4.24 mg.l-1,respectively. The comparison of measured values of acute toxicityfrom conventional tests and microbiological tests indicates thatmicrobiological tests are an appropriate alternative to todaycommonly used ecotoxicological biotests, for measuring andassessing of biological effects of toxic substances in the aquaticenvironment.