Fast examination of water quality using the automatic biotest ECOTOX based on the movement behavior of a freshwater flagellate

An early warning system, called ECOTOX, for monitoring the quality of water has been developed using different movement parameters of the motile unicellular flagellate Euglena gracilis as end points. The ability of orienting in the gravity field, the motility and the velocity of the cells were found to be sensitive to a number of toxic compounds. The biomonitor is controlled by a real time image analysis system which quantifies the movement parameters. Statistically significant changes in the measured parameters indicate a change in the tested water quality. The biomonitoring system works fully automatically and in a very short time. One cycle including a sample and control measurement takes between 6 to 10 min (depending on the software settings). For a number of toxins EC50 values have been calculated using the most sensitive end point, which is usually the gravitactic orientation. The toxic potential of a seepage water from an industrial waste deposit has been tested. G-values (lowest dilution factor of the tested water, where no significant toxic influence can be measured) have been determined. ECOTOX can be employed to detect quality changes in effluents and aquatic ecosystems and to indicate whether aquatic life may be endangered.