Worldwide pharmaceutical usage has increased substantially over the past years and has resulted in a concomitant increase of pharmaceuticals detected in the environment. As pharmaceuticals are designed to cause biological effects, the impact they might have on aquatic organisms and ecosystems is a growing concern. Therefore, in this thesis, I used and developed a combination of tools to assess the ecological impacts of pharmaceuticals on aquatic ecosystems. Furthermore, the data described in this thesis contributes to the understanding of the effects of the antidepressant fluoxetine and the antibiotic sulfamethoxazole on aquatic organisms and ecosystems.