Cadmium in freshwater ecosystems

Abstract

From an ecotoxicological point of view any substance which substantially modifies population and community characteristics must be considered dangerous. It is evident that a toxic substance may influence the biota if its concentration in the environment is over a certain level. Indeed, some heavy metals, dangerous at high concentrations, are essential to the biota at low concentrations. Unfortunately, it is often difficult to establish this level. Legislation concerning environmental protection is based on these concepts and maximum permissible concentrations are established essentially on the conclusions drawn from short-term experiments carried out under standard conditions. On the other hand, difficulties arising when results from different authors are compared and the great unreliability of extrapolating conclusions from laboratory studies to natural environment are well known. From these considerations it is clear that the ecotoxicological study of a metal must take into account the fate of the metal from its source to its uptake by organisms and its effects on individuals, populations and communities.