DAO 61:113-121 (2004)  -  doi:10.3354/dao061113

ABSTRACT: The acid-sensitive amphipod Gammarus fossarum was exposed in situ for 24, 96 and 168 h to 18 streams (9 draining from granite and 9 draining from sandstone bedrock), selected in order to provide a wide range of acidification. After 24 h, exposure to slightly acidic (6.00 ¾ pH ¾ 5.50) and strongly acidic water (pH < 5.50) led to a severe and significant depletion in haemolymph [Na⁺] and [Cl^-] compared to organisms exposed in circumneutral water. Highly significant linear correlations between stream mean pH value and haemolymph [Na⁺] and [Cl^-] were observed for each exposure time on each bedrock. Organisms exposed to slightly acid streams draining granite bedrock (pH = 5.71, pH = 5.81) showed a physiological adaptation after 96 h of exposure, while animals in acidic sandstone streams did not. Results of this study indicate that haemolymph [Na⁺] and [Cl^-] in G. fossarum could be an effective ecophysiological marker for monitoring freshwater ecosystem acidification.

KEY WORDS: Gammarus fossarum · Haemolymph · Ion loss · Acid stress · In situ markers