La exposición crónica al herbicida paraquat produce cambios en la sensibilidad y la demografía de Scenedesmus quadricauda.

Herbicides used in agricultural practices are a group of substances of particular interest in evaluating phytotoxicity on algal groups due to the similarity of their action mechanisms on higher plants, which are the target organisms of these chemical substances. They are also a fundamental component in assessing ecological risk. In this study, we evaluated growth, sensitivity, and demographic changes of Scenedesmus quadricauda after chronic exposure to sublethal concentrations of the herbicide paraquat. To achieve this, algal populations were incubated at different sublethal concentrations of paraquat for four months. Subsequently, toxicity tests were conducted with each of these populations, revealing changes in sensitivity to the herbicide, as demonstrated by higher toxicity indices corresponding to higher pre-exposure concentrations. Experiments performed with the various pre-exposed populations in the absence of the herbicide allowed us to observe modifications in the logistic growth models suggesting a permanent nature of the changes observed. The environmental implications of this adaptation on freshwater phytoplankton communities are discussed in relation to the impact of herbicide use in agricultural practices.