This book focuses on the topic of ecotoxicology of aquatic macrophytes and is wide ranging, including the use of macrophytes for remediation of contaminated sites. Many human activities are threats to the equilibrium of natural ecosystems. Pollution from point and non-point sources can be assessed using a variety of techniques, such as biomonitoring, biomarkers and biosensors. In aquatic ecosystems, biomonitoring of pollutants is mostly conducted by analysis of the tissues of invertebrates and fishes, and biomarker studies are also more widely applied to animals rather than in plants. Aquatic macrophytes occupy a key niche in aquatic ecosystems and provide a range of ecosystem services. In addition to their role in primary production, vegetation plays a key role in the cycling and retention of nutrients and generally acts as a sink for pollutants. Therefore, because of their importance to aquatic ecosystems, more attention should be paid to understanding the fate of pollutants and to developing methods to evaluate the health status of macrophytic plants in freshwater, marine and estuarine environments.