Extractable substances (anionic surfactants) from membrane filters induce morphological changes in the green alga Scenedesmus obliquus (Chlorophyceae).

The effect of filtration of medium through different kinds of filters (glass fiber, mixed esters of cellulose and nitrocellulose) on the morphology in the green alga Scenedesmus obliquus was examined. Several compounds potentially released from membrane filters were further investigated, and among them, two anionic surfactants were found to be morphologically active. Exposure to the anionic surfactants resulted within 2 d in the transformation of unicellular populations of Scenedesmus in populations dominated by colonies. Growth rates between control and surfactant-exposed populations were identical, and the morphological effect occurred at surfactant concentrations far below the reported no-observed-effect concentration for growth inhibition, stressing the need for inclusion of morphological appearance of Scenedesmus in algal toxicity testing to improve the assessment of ecological risks.