Blood Gases, Acid–Base Status, Ions, and Hematology in Adult Brook Trout (<i>Salvelinus fontinalis</i>) under Acid/Aluminum Exposure

Abstract

The relative importance of ionoregulatory and respiratory disturbances in brook trout (Salvelinus fontinalis) under acid/Al stress in soft water is dependent upon water pH and Ca 2+ levels. Trout acclimated to Ca 2+ = 25 or 400 μequiv/L were fitted with arterial catheters and exposed to acid/Al for 10 d under flow-through conditions. Parameters monitored included pHa, [Formula: see text], [Formula: see text], HCO 3 − , ΔH + m, Na + , Cl − , K + , Ca 2+ , protein, lactate, glucose, hemoglobin, and hematocrit. Exposure to pH = 4.8 (no Al) at Ca 2+ = 25 μequiv/L caused no mortality and negligible physiological disturbance. Addition of Al (333 μg/L or 12.3 μmol/L) resulted in &gt;80% mortality (LT50 = 39.0 h) preceded by a marked decrease of plasma Na + and Cl − , a moderate disturbance of blood gases, but no acidosis. At higher Ca 2+ (400 μequiv/L), this same exposure (pH = 4.8, Al = 333 μg/L) caused similar mortality (LT50 = 38.5 h) but smaller ionic disturbances, much larger decreases in blood O 2 , increases in blood CO 2 , and respiratory acidosis. Exposure to pH = 4.4 (no Al) at Ca 2+ = 25 μequiv/L caused 60% mortality (LT50 = 170.0) preceded by marked ionic disturbances and metabolic acidosis, but little change in blood gases. Addition of Al (333 μg/L) increased mortality to &gt;80% (LT50 = 78.2 h) with smaller ionic but greater respiratory disturbances.