State and pollution of freshwater ecosystems – Warning signals of a changing environment:
Inland waters are exposed to numerous natural and anthropogenic stress factors. Pollution by nutrients, harmful substances, and pathogens, the destruction of pristine habitats due to water way construction, changes in climate and invasion by non-indigenous species can lead to changes in biodiversity, a lowering of the self-cleaning capacity, and to serious restrictions in use.
Major problems are eutrophication, atmospheric and geogenic acidification, salinisation and contamination by a huge number of xenobiotics. Especially in eutrophic waters an impairment of aquatic organisms can also be induced by algogenic substances. Some substances influence the ’critical equilibrium’ of the sexual hormones of vertebrates, so that entire populations are threatened by the disturbance of reproduction.
Precautionary water conservation, use of measures to reduce external loading sources and the application of ecotechnologies may reduce or reverse the impairments of freshwater ecosystems.