A RELATIONSHIP BETWEEN GILL SILVER ACCUMULATION AND ACUTE SILVER TOXICITY IN THE FRESHWATER RAINBOW TROUT: SUPPORT FOR THE ACUTE SILVER BIOTIC LIGAND MODEL

摘要

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℃) 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.