TEMPERATURE EFFECTS ON ACCUMULATION AND RETENTION OF RADIONUCLIDES INTHE SEA-STAR, ASTERIAS-FORBESI - IMPLICATIONS FOR CONTAMINATED NORTHERN WATERS

Radioactive waste disposal and nuclear testing concentrated in high la titudes in the northern hemisphere have resulted in the accumulation o f radionuclides in Arctic marine ecosystems, but little is known of th e consequences for marine biota in these waters. Under controlled labo ratory conditions in May through September 1994, we examined the bioac cumulation in sea stars, Asterias forbesi (Desor), of the radionuclide s Am-241, Co-57 and Cs-137, all of which are important components of d isposed radioactive wastes. Experiments at 2 and 12 degrees C determin ed the relative importance of food (the bivalve, Macoma balthica) and water as sources of radionuclides and assessed the influence of temper ature on radionuclide influx and efflux rates. The lower temperature g reatly increased the retention of radionuclides ingested with food; fo r instance, the biological half-life (tb(1/2)) of Am-241 in the sea st ars was 31 d at 12 degrees C, but was virtually infinite at 2 degrees C. Retention of ingested Co-57 was also increased at 2 degrees C (tb(1 /2) = 41 d). Cs-137 was not accumulated from food. Low temperature sig nificantly reduced net influx rates of Cs-137 from water, but did not affect net uptake of Am-241 or Co-57. Temperature had little effect on the retention of all three isotopes obtained from the dissolved phase . These experiments suggest that extrapolation of results of previous radioecological studies, conducted at warmer temperatures, to polar or temperate winter environments may be problematic, and that nuclear wa ste isotopes obtained through trophic transfer may be retained far mor e efficiently in high latitude marine biota than by fauna from warmer ecosystems.