[Ecotoxicology and water quality].

Fundamental concepts of ecotoxicology are presented, making specific reference to the aquatic environment. As far as exposure to contaminants is concerned, the main properties of a substance that determine its presence in the various environmental compartments and matrices are illustrated and discussed. The crucial importance of the bioaccumulation potential is stressed, as it can be responsible for the level of substance reached in the biota, which can be much higher than that present in the external environment. It is also underlined the importance of bioavailability processes, which tune the chemical fraction available for absorption by organisms. The toxic effects on biota are illustrated at the different levels of biological organization they can be observed. Last, the role of the ecotoxicological investigation within an integrated approach to the water quality assessment is discussed along with the specific information provided.