EFFECTS OF ARCTIC TEMPERATURES ON DISTRIBUTION AND RETENTION OF THE NUCLEAR WASTE RADIONUCLIDES AM-241, CO-57, AND CS-137 IN THE BIOINDICATOR BIVALVE MACOMA-BALTHICA

The disposal of radioactive wastes in Arctic seas has made it importan t to understand the processes affecting the accumulation of radionucli des in food webs in coldwater ecosystems. We examined the effects of t emperature on radionuclide assimilation and retention by the bioindica tor bivalve Macoma balthica using three representative nuclear waste c omponents, Am-241, Co-57, and Cs-137. Experiments were designed to det ermine the kinetics of processes that control uptake from food and wat er, as well as kinetic constants of loss. Cs-137 was not accumulated i n soft tissue from water during short exposures, and was rapidly lost from shell with no thermal dependence. No effects of temperature on Co -57 assimilation or retention from food were observed. The only substa ntial effect of polar temperatures was that on the assimilation effici ency of Am-241 from food, where 10% was assimilated at 2 degrees C and 26% at 12 degrees C, For all three radionuclides, body distributions were correlated with source, with most radioactivity obtained from wat er found in the shell and food in the soft tissues. These results sugg est that in general Arctic conditions had relatively small effects on the biological processes which influence the bioaccumulation of radioa ctive wastes, and bivalve concentration factors may not be appreciably different between polar and temperate waters. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.