Short-term physiological responses to a severe acid stress in three macroinvertebrate species: a comparative study.

The present study focuses on the sensitivity among freshwater invertebrate species to acidic stress. Three common macroinvertebrate species in the Vosges Mountains (North-Eastern France), Gammarus fossarum (Amphipoda), Hydropsyche pellucidula (Trichoptera) and Dinocras cephalotes (Plecoptera) were exposed for 24, 72 and 120 h to natural acidified water (pH=4.73+/-0.08, [Ca2+]=39.1+/-0.6 micromol l(-1), [Al(tot)]=28.4+/-1 micromol l(-1)). Short-term exposure to acid stress caused significant decreases both in survival rate and haemolymph ions ([Cl-] and [Na+]). The relative sensitivity to a natural acidic stress slightly differed among the species and was in the following order: G. fossarum, as the most sensitive, then H. pellucidula and D. cephalotes. Results of this study confirm the interest of in situ tests to assess the toxicity of short-term acid exposure. Finally, our results reinforce the hypothesis that transient acidification can offset the recovery of sensitive species of macroinvertebrates in streams chemically recovering from acidification either through liming or declining deposition.