A relationship between gill silver accumulation and acute silver toxicity in the freshwater rainbow trout: Support for the acute silver biotic ligand model

Rainbow trout were exposed to a range of silver concentrations (as AgNO 3 ) in flowing synthetic soft water (0.05 mM Na + , 0.05 mM Cl − , 0.05 mM Ca 2+ , 0.02 mM Mg 2+ , 0.02 mM K + , pH 7.0, approximately 0.7 mg C/L dissolved organic carbon, 10 mg CaCO 3 /L, 10 ± 2°C) to investigate a possible relationship between short‐term gill silver accumulation (3 h or 24 h) and acute silver toxicity (96‐h mortality). We also investigated potential relationships between gill silver accumulation and inhibition of Na + uptake plus inhibition of gill Na + K + ‐adenosine triphosphatase (ATPase) activity. The 96‐h median lethal concentration (LC50) values were 13.3 μg total Ag L −1 and 3.3 μg dissolved Ag L −1 . A relationship was demonstrated between 3‐h and 24‐h gill silver accumulation and 96‐h mortality. A relationship also was demonstrated between gill silver accumulation and inhibition of Na + uptake at 24 h of exposure. No relationship between gill silver accumulation and inhibition of gill Na + K + ‐ATPase activity was found. The 96‐h median lethal gill accumulation (LA50) values of 129 (at 3 h) and 191 ng g −1 (at 24 h) and a conditional equilibrium binding constant of 8.0 for Ag + binding to the gills were calculated. These observations support use of the silver biotic ligand model (BLM) as a regulatory tool to predict acute silver toxicity.