Early warning tools for ecotoxicity assessment based on Phaeodactylum tricornutum

Phaeodactylum tricornutum was exposed to various toxic substances (zinc, copper or dodecylben- zenesulfonic acid sodium salt) in accordance with the Al- galToxkit protocol based on the UNI EN ISO 10253 method in order to quantitatively compare the responses obtained by traditional growth-rate inhibition tests with morphological (biovolume) and physiological (chloro- phyll-a, phaeophytin ratio) endpoints. A novel approach is proposed for detecting early and sub-lethal effects based on biovolume quantification using confocal microscopy cou- pled with an image analysis system. The results showed that effects on both biovolume and the photosynthetic complex are sensitive and powerful early warning tools for evaluating sub-lethal effects of exposure. Specifically, biovolume showed significant sensitive and early responses for the tested surfactant. Qualitatively, we also observed structural anomalies and effects on natural auto-fluores- cence in exposed cells that also represent potentially useful tools for ecotoxicological studies.