Bioaccumulation of ¹³⁷Cs and ⁵⁷Co by five marine phytoplankton species

Under controlled laboratory conditions, we have examined the bioaccumulation of ¹³⁷Cs and ⁵⁷Co in three prymnesiophytes, the coccolithophorid Emiliania huxleyi and the non-calcareous species Isochrysis galbana and Phaeocystis globosa, and two diatoms Skeletonema costatum and Thalassiosira pseudonana. We measured the uptake in growing and non-growing cells and determined concentration factors on both volume and dry weight bases. For uptake of ⁵⁷Co in non-growing cells, volume concentration factors (VCF) at equilibrium ranged from 0.2×10³ for E. huxleyi to 4×10³ for T. pseudonana. For uptake of ¹³⁷Cs in non-growing cells, the VCFs were low for all species and the uptake pattern seemed unsystematic. The results suggest that, in contrast to Co, the cycling and bioaccumulation of Cs in marine animals are unlikely to be affected by Cs accumulation in primary producers.