Uptake and depuration of cesium in the green mussel Perna viridis

The accumulation and depuration of Cs in the green mussels (Perna viridis) commonly found in the subtropical and tropical waters were studied under th e laboratory conditions using radiotracer techniques. Following an initial rapid sorption onto the mussel's tissues, uptake of Cs exhibited linear pat terns over a short exposure time (8 h) at different ambient Cs concentratio ns. The concentration factor was independent of ambient Cs concentration. T he calculated uptake rate and initial sorption constant of Cs were directly proportional to the ambient Cs concentration. The calculated uptake rate c onstant from the dissolved phase in the mussels was as low as 0.0261 g(-1) d(-1) Uptake rates of Cs in the mussels were inversely related to the ambie nt salinity. Uptake increased about twofold when the salinity was reduced f rom 33 to 15 ppt. The effect of sa linity on Cs uptake was primarily due to the change in ambient Kf concentration. The uptake rate decreased in a pow er function with increasing tissue dry weight of the mussels, although the initial sorption was not related to the mussel's body size. The efflux rate constant of Cs in the mussels was 0.15 to 0.18 d(-1), and was the highest recorded to date among different metals in marine bivalves. The efflux rate constant also decreased in a power function with increasing tissue dry wei ght of mussels. A simple kinetic model predicted that the bioconcentration factor of Cs in the green mussels was 145, which was higher than measuremen ts taken in their temperate counterparts. The bioconcentration factor also decreased in a power function with increasing tissue dry weight of mussels.