Effects of altering freshwater chemistry on physiological responses of rainbow trout to silver exposure

Abstract

AbstractThe influence of different water Cl− (50–600 μM), Ca2+ (50–1, 500 μM), Na+ (50–1, 500 μM), or dissolved organic carbon (DOC, 0.31–5 mg/L) levels on silver‐induced physiological and biochemical perturbations of rainbow trout were investigated. Fish were acclimated to soft water (50 μM; Cl−, Ca2+, and Na+), then exposed to 3.7 μg/L Ag (as AgNO3) for 6 h, which resulted in a reduction in Na+ influx from the water, an inhibition of gill sodium‐ and potassium‐activated adenosine triphosphatase (Na+/K+‐ATPase) activity, and an accumulation of silver on the gills. Increasing the water Cl− or DOC levels ameliorated the silver toxicity. However, increasing water Ca2+ or Na+ concentration did not reduce the silver‐induced physiological and biochemical perturbations. The free silver ion (Ag+) concentrations (calculated from MINEQL+, a geochemical speciation computer program) showed a negative correlation with the Na+ influx rates and gill Na+/K+‐ATPase activity. However, gill silver levels did not correlate to Ag+ concentrations and no correlation was found between gill silver levels and either Na+ influx rates or gill Na+/K+‐ATPase activity. These results support the notion that the [Ag+] concentration is of major importance when assessing silver toxicity in fish, and that this should be taken into account in regulatory strategies for silver in the natural environment.