EFFECTS OF WATER CHEMISTRY AND TEMPERATURE ON RADIOCESIUM DYNAMICS INRAINBOW-TROUT, ONCORHYNCHUS-MYKISS

We determined the effects of temperature (8 and 16 degrees C) and wate r concentrations of potassium (0.01-3.4 mmol/L), sodium (0.4-3.0 mmol/ L), and calcium (0.3-2.9 mmol/L) on the dynamics of Cs-137 in rainbow trout (Oncorhynchus mykiss). Trout were fed food labelled with Cs-137 and Cs-137 retention was monitored by whole body gamma counting (70 d) . Assimilation of Cs-137 did not vary significantly over the range of concentrations of K+, Na+, and Ca2+ employed, with an average value of 65 +/- 3% (mean +/- SE). The elimination of Cs-137 Was significantly affected by K+, with the elimination rate constant of trout held at th e highest K+ concentration (0.011 + 0.001 d(-1) at K+ of 3.4 mmol/L) r oughly double that observed in trout at lower Kt (0.011 +/- 0.001 d(-1 ) at K+ less than or equal to 0.3 mmol/L). Elimination of Cs-137 was a lso significantly affected by temperature, with the increase in elimin ation rate over the range of 8 and 16 degrees C corresponding to a Q(1 0) of approximate to 1.7. Although the effect of K+ on accumulation of Cs-137 in trout was statistically significant, this effect, by itself , can explain only a small fraction of the broad range of Cs-137 conce ntration ratios reported for wild fish.