Physiological Evidence of Acclimation to Acid/Aluminum Stress in Adult Brook Trout (Salvelinus fontinalis). 2. Blood Parameters by Cannulation

Abstract

Brook trout (Salvelinus fontinalis) exposed for 10 wk to sublethal acid (pH = 5.2) plus Al (150 .mu.g/L) in flowing soft water (Ca2+ = 25 .mu.equiv/L) did not exhibit chronic respiratory disturbance or elevated stress indices, as revealed by sampling of arterial blood gases, acid-base status, glucose, and cortisol via an indwelling catheter. Acclimation occurred, which prevented mortality and greatly attenuated the disturbances of respiratory, acid-base, and stress parameters normally seen upon challenge with more severe acid (pH=4.8) plus Al conditions (333 .mu.g/L) for 3 d. Ionoregulatory, fluid volume, and hematological disturbances were similarly reduced. Higher water Ca2+ (400 .mu.equiv/L) slightly delayed but did not prevent this suite of toxic responses in naive fish. These disturbances did not occur in naive fish challenged with acid alone (pH= 4.8). However, long-term adaptation to acid alone (pH = 5.2) resulted in elevated glucose and cortisol levels and offered no protection against the more severe acid plus Al challenge. Thus, the acclimation was to Al rather than to acidity itself, and low levels of Al may be beneficial to fish under chronic acid stress.