Effects of water chemistry and temperature on radiocesium dynamics in rainbow trout,Oncorhynchus mykiss

We determined the effects of temperature (8 and 16 °C) and water 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 of137Cs in rainbow trout (Oncorhynchus mykiss). Trout were fed food labelled with137Cs, and137Cs retention was monitored by whole body gamma counting (70 d). Assimilation of137Cs 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 of137Cs was significantly affected by K+, with the elimination rate constant of trout held at the highest K+concentration (0.021 ± 0.001 d−1at K+of 3.4 mmol/L) roughly double that observed in trout at lower K+(0.011 ± 0.001 d−1at K+≤ 0.3 mmol/L). Elimination of137Cs was also significantly affected by temperature, with the increase in elimination rate over the range of 8 and 16 °C corresponding to a Q10of ≈1.7. Although the effect of K+on accumulation of137Cs in trout was statistically significant, this effect, by itself, can explain only a small fraction of the broad range of137Cs concentration ratios reported for wild fish.