Effects of Low pH and Aluminum on Ventilation in the Brook Trout (Salvelinus fontinalis)

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Abstract
Brook trout (Salvelinus fontinalis) (acclimated to pH = 6.5, Ca2+ = 400 .mu.equiv .cntdot. L-1), when exposed to acid (pH = 4.8, Ca2+ = 400 .mu.equiv .cntdot. L-1) and Al (333 .mu.g .cntdot. L-1), responded with a twofold increase in ventilation volume within the first 4 h of the challenge period (100 h). Increased ventilation stroke volume accounted for most of the change in ventilatory response; rate increased slightly. Although ventilation volume returned to prechallenge values by 6 h, coughing (flow reversal) and increased mucus production at the gills were notable throughout the challenge period. There were no significant changes in oxygen consumption or PaO2, but hemoglobin oxygen content (micromoles per gram of hemoglobin) decreased by 20%. Arterial pH decreased as a result of both respiratory and metabolic disturbances. Exposure to acid (pH = 4.8, Ca2+ = 400 .mu.equiv .cntdot. L-1) in the absence of Al resulted in similar initial changes in ventilation and blood acid-base status; however, ventilation remained elevated above the prechallenge values throughout the experiment (24 h). The transient increase and subsequent return of ventilation to prechallenge levels in the acid/Al-exposed fish suggests that Al interfered with the mechanism controlling the ventilatory responses.