SURVIVAL, SUBLETHAL RESPONSES, AND TISSUE RESIDUES OF ATLANTIC SALMONEXPOSED TO ACIDIC PH AND ALUMINUM

Early life stages of Atlantic salmon (Sabno salar) were continuously e xposed to pHs ranging from 4.5 to 7.2 in one study, and to A1 concentr ations ranging from 33 to 264 mu g/l at pH 5.5 in a second study. The tests were begun with eyed eggs and conducted until 60 d post-hatch. T he exposure water contained about 3.0 mg/l calcium and was representat ive of acid-sensitive surface waters with low acid-neutralizing capaci ty. Hatching success, mortality, growth, behavior, and tissue residues of aluminum were determined during the tests. Egg hatching and the gr owth of larvae were reduced significantly al pH 4.5 and 5.0, and larva l mortality increased at pH 4.5. Larval feeding and swimming behavior were impaired at pH 6.5 and lower. Hatching was not affected at pH 5.5 in the presence of Al; however, larvae exposed to 124 mu g Al/l at pH 5.5 incurred significant increases in mortality. The inhibition of fe eding observed among fish exposed to pH 5.5 was intensified at all con centrations of Al tested. At pH 5.5, reduced growth occurred among lar vae exposed to 71 mu g Al/l and higher. Concentrations of Al in whole- body tissue ranged from 3 mu g/g for fish exposed to 33 mu g Al/l to 9 6 mu g/g for those exposed to 264 mu g Al/l. At 60 d of exposure, bioc oncentration factors ranged from 76 to 190 and were directly related t o exposure concentration. Sublethal exposure of Atlantic salmon to aci dic pH alone, and in combination with Al, may significantly reduce the ir fitness and may also play a significant role in recruitment failure in some acid-sensitive waters in the northeastern United States.