Biotests using aquatic organisms are employed in the fields of prospective chemical hazard assessment and testing of effluents and other environmental samples. Conduct of established and standardised biotests comprises test systems that represent different trophic levels (algae, daphnids, fish and bacteria). In international fora there is currently a debate as to whether unicellular algae as systematically and structurally simple organisms are a satisfactory representation of all autotrophic life forms. This paper therefore studies the sensitivity and specificity of a biotest with the duckweed Lemna minor.

The results presented demonstrate that for the establishment of a biotest with a higher aquatic plant, effect parameter and toxicological endpoints require particular reflection. With respect to the question of sensitivity and specificity of responses concentration response analysis was performed for selected herbicides. In comparison with well-established algal biotests Lemna shows significantly higher sensitivities for different herbicides with diverse modes of action. Finally, the responsiveness to environmental samples was studied for a transect along the river Neiße.

On the basis of the findings there is a clear recommendation to regard the presented biotest using Lemna minor as a suitable supplementation to algal biotests.