EXPERIMENTAL CADMIUM CONTAMINATION OF ASTERIAS-RUBENS (ECHINODERMATA)

Asteroids Asterias rubens (Linneaus, 1758) were exposed in the field t o various concentrations of waterborne or dietary Cd (from contaminate d mussels). Cadmium uptake, and subsequent loss, kinetics were studied for 45 d for each. Dietary (110 mu g Cd g(-1) dry wt of the prey) and waterborne (5 and 20 mu g Cd l(-1)) Cd was significantly accumulated in the 3 measured body compartments: pyloric caeca, body wall, and ske leton. Waterborne Cd (1 mu g Cd l(-1)) was also significantly accumula ted in the body wall but not in the pyloric caeca or the skeleton. Die tary Cd accumulation occurred in all body compartments. In the pyloric caeca, a steady state equilibrium was reached within 20 d, the concen tration at steady state ranging from 3 to 9 mu g Cd g(-1) dry wt accor ding to the exposure mode. The body wall and the skeleton accumulated Cd Linearly during the exposure period at a rate of 0.07 to 0.25 mu g Cd g(-1) dry wt d(-1) according to the exposure mode. Cadmium loss kin etics were fitted by inverse exponential functions to all body compart ments, except to the skeleton where the loss was generally nonsignific ant. Results indicate that there is a Cd flux through the asteroid bod y from the digestive system to the body wall where Cd is slowly incorp orated to the skeleton. Concentration factors calculated for the pylor ic caeca fit the range of values previously reported from laboratory e xperiments and thus validate them in field conditions. Thus A. rubens may be considered a valuable bioindicator of Cd contamination.