Micropollutants in aquatic resources have raised global concerns regarding the conservation of ecosystems. Although they are usually found in the environment at trace concentrations to a maximum of several µg/L, it is still necessary to address the potential risks these pollutants may represent to organisms. A multifactor analysis was conducted using two algae as bioindicators. Four different pharmaceuticals were chosen based on their occurrence in domestic wastewaters and persistency after biological treatment processes ranging from 1/8th to four-fold representative environmental concentrations over 96 h exposure. The present multifactor analysis evaluated cell size, photosynthetic capacity and growth rate. These data were later combined into a simplified single entity: "the index effect". The results obtained showed that, even at concentrations below the environmentally relevant concentrations (ERC), the pharmaceuticals' residues (PRs), caused a cellular behavioural variation in both organisms. In addition, the algae cultures' response to exposure to these stressors was generally dependent on the concentration over time. By examining four different PR over three different characteristics of two types of algal bioindicators, this work covers significant and specific responses on the algae exposure cycle. This is unique research since most studies do not consider multiple parameters in the assessment of the environment risk for bioindicators.
Keywords: Chlorella vulgaris; Raphidocelis subcapitata; algae; ecotoxicity; micropollutants; multifactorial approach; pharmaceuticals.