Plecoptera response to acidification in several headwater streams in the Vosges Mountains (northeastern France)
Plecoptera are among the most threatened aquatic invertebrates in industrialised countries as they are very sensitive to many types of pollution. On the contrary, stoneflies are largely considered as tolerant to acidification in comparison with many other macroinvertebrate groups. However, an understanding of Plecoptera responses to acidification is lacking due firstly to thecomplexity of most Nemouroidea specific determinations at larval instars and secondly to the poor Plecoptera diversity in North European countries, where most studies on acidification impact were performed. In the present study, we assess the response of Plecoptera species and species assemblages to freshwater acidification by collecting adults, allowing specific determination. Significant relationships were observed between richness and several chemical parameters. The relative abundance of several species was also significantly correlated to pH and acid neutralizing capacity (ANC). The results highlight the importance of species determination to assess the effects of acidification. Direct effects, i.e. ecotoxicological effects, were not the only factor leading to the erosion of Plecoptera diversity. Finally, this study tends to demonstrate that this order of aquatic insects is more severely affected by freshwater acidification than commonly believed.