Bioaccumulation of tritiated water in phytoplankton and trophic transfer of organically bound tritium to the blue mussel, Mytilus edulis

► Tritium was bioaccumulated into organic tritium in phytoplankton cells. ► Green algae incorporated more tritium than the cyanobacteria. ► Organic tritium was transferred from phytoplankton to blue mussels when ingested. ► Linear uptake of tritium into mussels indicates a potential for biomagnification. ► Current legislation may underestimate accumulation of tritium in the environment.