Chronic toxicity of a laundry detergent to the freshwater flagellate Euglena gracilis

Chronic toxicity of the common laundry detergent Ariel on the freshwater alga Euglena gracilis was investigated by growing the alga in a medium containing the detergent for 7 days. Cell density, motility, swimming velocity, gravitactic orientation, cell shape, photosynthesis and concentration of light-harvesting pigments were used as end point parameters for the assessment of toxicity. Cell density was significantly reduced at a concentration of 1 mg l−1 or above. Among the other tested parameters, with the exception of cell shape, gravitaxis and chlorophyll b, all were adversely affected by the detergent at concentrations exceeding 1 mg l−1. It is concluded that long-term (7-days) exposure to the detergent caused significant toxicity to E. gracilis. Furthermore, long-term tests with E. gracilis can be used as sensitive indicator for the toxicity assessment of laundry detergents in aquatic environments.