Evaluation of body size and temperature on ¹³⁷ Cs uptake in marine animals

¹³⁷ Cs bioaccumulation and retention in seven different marine animal species, including crustaceans, mollusc larvae, and fish larvae were compared under different temperature conditions (10 °C, 18 °C and 25 °C). Replicate animals were experimentally exposed to 0.5 nM ¹³⁷ Cs dissolved in filtered seawater for 3 days, and their ¹³⁷ Cs contents were periodically measured using gamma spectrometry. Among the seven species, ¹³⁷ Cs bioconcentration factors ranged from 14 to 239 at the end of the exposure periods. Following uptake, the ¹³⁷ Cs loss rate constants from the animals ranged from 5 to 50% d ⁻¹ and were unaffected by temperature or animal size. The ¹³⁷ Cs bioconcentration factors were directly related to animal size and hence their surface: volume ratios, consistent with the conclusion that Cs sorption from the aqueous phase is the principal uptake mechanism in these animals. With the exception of gastropods, temperature had no major influence on Cs uptake and efflux in the experimental species.