Effects of ambient water chemistry on the assimilation and elimination of cesium-137 by rainbow trout

The present study investigated the effects of water chemistry on the assimilation and elimination of dietary cesium-137 ({dollar}sp{lcub}137{rcub}{dollar}Cs) by rainbow trout (Onchorhyncus mykiss). Trout were fed {dollar}sp{lcub}137{rcub}{dollar}Cs labelled diet and the retention of {dollar}sp{lcub}137{rcub}{dollar}Cs was monitored over a 70 day period by whole body gamma counting. Apparent assimilation of {dollar}sp{lcub}137{rcub}{dollar}Cs was not significantly affected by varying ambient concentrations of potassium (0.5-120 mg{dollar}cdot{dollar}L{dollar}sp{lcub}-1{rcub}),{dollar} sodium (10-68 mg{dollar}cdot{dollar}L{dollar}sp{lcub}-1{rcub}),{dollar} calcium (10-123 mg{dollar}cdot{dollar}L{dollar}sp{lcub}-1{rcub}),{dollar} or total hardness (45-400 mg{dollar}cdot{dollar}L{dollar}sp{lcub}-1{rcub}{dollar} as CaCO{dollar}sb3{dollar}). The overall mean ({dollar}pm{dollar}SE) assimilation of {dollar}sp{lcub}137{rcub}{dollar}Cs was 65 {dollar}pm{dollar} 3%. The elimination of {dollar}sp{lcub}137{rcub}{dollar}Cs was affected by K{dollar}sp+{dollar} with significant increases in the elimination rate constant (0.021 {dollar}pm{dollar} 0.001 d{dollar}sp{lcub}-1{rcub}{dollar}) for trout held at the highest K{dollar}sp+{dollar} concentration (120 mg{dollar}cdot{dollar}L{dollar}sp{lcub}-1{rcub}).{dollar} Temperature over the range of 8 and 16{dollar}spcirc{dollar}C also increased elimination of {dollar}sp{lcub}137{rcub}{dollar}Cs with a Q{dollar}sb{lcub}10{rcub}{dollar} of 1.7. Ambient K{dollar}sp+{dollar} modifies accumulation of {dollar}sp{lcub}137{rcub}{dollar}Cs in fish by affecting elimination rather than assimilation; however, the effect was not of sufficient magnitude to fully explain the broad range in concentration ratios observed in the field.