We report the evaluation of changes in water quality, increasing pollution level, of a section of Suquía River basin (Córdoba, Argentina) by using Myriophyllum quitense as bioindicator in addition to the measurement of chemical parameters, combined with chemometrics (ANOVA, Cluster and Discriminant Analysis). Myriophyllum quitense was collected upstream from Córdoba city at an unpolluted site of Suquía River basin. After collection plants were transplanted to different sites with different pollution levels. Subsequent to transplantation plants were weekly collected from the original site as well as from transplantation stations. Water quality was evaluated throughout the transplantation experiment, while the use of this macrophyte as bioindicator was verified through the activation of its antioxidant defenses and biotransformation system. Myriophyllum quitense reacts to the pollution stress increasing the activity of glutathione-S-transferases (CDNB and Fluorodifen), glutathione reductase (GR) and peroxidase (POD). Elevated enzyme activities agreed to different pollution levels, especially inorganic nitrogen loads combined with elevated lead and aluminum concentrations, all of them originated by anthropogenic activities, thus presenting Myriophyllum quitense as a good biomonitor for assessment of water quality in this polluted aquatic ecosystem.