ABSTRACT: Uptake and loss kinetics of Zn, Ag, Cd, ¹³⁴Cs, and ²⁴¹Am by the echinoid Paracentrotus lividus contaminated through either water or foodwere determined in controlled laboratory radiotracer experiments using low contaminant concentrations. The echinoid efficiently accumulated most of the elements from water. The only exception was ¹³⁴Cs (concentration factor at steady state = 2.7). With respect to relative metal bioavailability, concentrations in the different body compartments of P. lividus were generally ranked in the order: digestive wall > gonads >= body wall > Aristotle's lantern > coelomic fluid. However, for ²⁴¹Am, body wall uptake was as efficient as that of the digestive wall. The loss kinetics for Zn, Ag, and ¹³⁴Cs were described by a 2-component model whereas loss of Cd and ²⁴¹Am was linear during the time course of the experiment. Loss of the different elements was relatively slow, except for ¹³⁴Cs, whose long-lived loss component was characterized by a biological half-life of 6 d. Loss of the different elements ingested with food was described by a single-component model for Cd, ¹³⁴Cs, and ²⁴¹Am and by a 2-component model for Zn and Ag. Parameters of the kinetics indicate that all (for Cd, ¹³⁴Cs, and ²⁴¹Am) or most (for Zn and Ag) of the ingested amount of element is readily lost from the organism with the faeces. However, estimation of the assimilated fraction of elements ingested by the echinoids suggests that food could contribute significantly to the total body burden of Ag in P. lividus.

KEY WORDS: Metals · Radionuclides · Uptake · Loss · Paracentrotus lividus

Published in MEPS Vol. 141 (1996) on October 3
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996