The aquatic environment is very sensitive to the pertubations which may accompany the mining of metals. Slight alterations in the loading of chemicals in freshwater systems are frequently reflected in large changes in the transfer of contaminants to aquatic species because of the potential for bioconcentration. Bioconcentration of radionuclides by the biota is a source of interest to both environmental scientists and regulatory agencies, since aquatic plants may be potential indicators for aquatic pollution and could also be significant sources of contaminants for herbivorous wildlife near mines and mine tailings systems. The discovery of a significant uranium orebody in a region encompassing many small lakes in the Okanagan region of south-central British Columbia permitted the assessment of seasonal uptake of naturally occuring radionuclides of the uranium series by aquatic plants. The objectives of this study were to assess the potential for bioconcentration of naturally occuring radionuclides in yellow pond-lily (Nuphar lute a subspecies polysepala (Engelmann) Beal),and to determine if seasonal variation in accumulation occured. MATERIALS AND METHODS