Macroinvertebrate community loss as a result of headwater stream acidification in the Vosges Mountains (N-E France)

The relationships between water chemistry and aquatic macroinvertebrate com munities of 41 headwater streams were studied in the Vosges Mountains (N-E of France) in an attempt to assess the impact of acidification on macroinve rtebrate diversity. The taxa richness of macroinvertebrates decreased drast ically in headwater streams which were characterized by low pH, low calcium and high aluminum content. All taxonomic groups were affected, but Mollusc ans, Crustaceans and Ephemeroptera disappeared totally from strongly acidif ied streams. Simple indices based on taxa richness such as the coefficient of community loss may provide accurate tools to quickly assess the impact o f acidification on macroinvertebrate communities. Despite the reduction of atmospheric SO2 emissions, acidification of freshwater in the Vosges Mounta ins continues to affect streams which were believed in the past to constitu te refuge biotopes for numerous species. Consequently, acidification repres ents a real threat for numerous invertebrates. This study arises the questi on of the evolution in the future of headwater stream ecosystems. Urgent de cisions and interventions are required to preserve non-acidified streams an d to restore impacted ecosystems while awaiting spontaneous recovery.