Uptake and loss of technetium-95m in the crab Pachygrapsus marmoratus

The uptake and loss kinetics of sup(95m)Tc in seawater have been investigated in the crab Pachygrapsus marmoratus. Both the uptake and loss kinetics can be represented as the sum of two exponential functions, one short-term (tbsub(1/2)=16 d) and one long-term (tbsub(1/2)=63 d), tbsub(1/2) being the biological half-time. The predicted steady state concentration factor was estimated to be about 18. No significant linear correlation between Tc uptake rate and animal weight was found during the accumulation phase. At the end of this phase, 77% of the Tc was found to be distributed in the digestive system and particularly in the hepatopancreas (56%); this organ also appeared to lose the radionuclide most quickly. During the loss phase, 90% of the incorporated radioactivity was eliminated in about three months. Therefore P. marmoratus does not appear to be a good bioindicator of Tc in the marine environment nor an important pathway for Tc contamination along marine food chains. (author)