Effects of waterborne complexing agents on silver uptake and depuration in rainbow trout

Rainbow trout Oncorhynchus mykiss ( c . 60 g) were exposed for 1 week to 0·1 μM silver as AgNO₃ in ion poor water (Ca c . 150 μM, pH c . 8, water temperature 13° C) with or without waterborne organic matter (27 mg C l^?1 as Aldrich humic acid), thiosulphate (5 μM Na₂S₂O₃) or chloride (4 mM KCl). Organic matter decreased Ag accumulation by the gills initially, but did not decrease Ag accumulation by plasma or liver. Thiosulphate decreased the amount of Ag accumulated by the gills for the entire 1 week exposure but had no effect on Ag concentrations in the plasma, liver or bile. Chloride had no effect on Ag uptake in any of the tissues examined. All three complexing agents reduced the decreases in plasma Na and Cl concentrations caused by Ag. To study the effects of waterborne complexing agents on Ag depuration, rainbow trout were exposed to 0·1 μM AgNO₃ for 1 week then placed for 8 days in Ag‐free, ion poor water with or without waterborne organic matter (55 mg C l^?1) or thiosulphate (5 μM). These complexing agents did not alter depuration of Ag from the gills, plasma, liver or bile. Thus, once Ag has entered a fish, subsequent elimination of internal Ag is not affected by external complexing agents.