Effect of selenium on cadmium uptake in selected benthic invertebrates

Effect of selenium on uptake of cadmium in the benthic marine invertebrates Asterias rubens, Mytilus edulis, Littorina littorea, and Arenicola marina was investigated in a series of laboratory experiments. A. rubens exposed to 200 ~cg Cd 1-' alone took up cadmium in body wall, pyloric caeca, and tube feet at initial rates of 1 to 2 pg Cd g-' dry wt d-'; steady state concentrations of 10 to 30 pg Cd g-l were reached after 1 to 2 wk. Concurrent exposure to 141 pg Se-Se031-' increased cadmium uptake rates to 5 to 10 pg Cd g-' d-'; uptake proceeded linearly with time over 4 wk. Exposure to 200 pg Cd I-' did not affect uptake of selenium from 141 pg Se-Se0;I-'. Uptake of cadmium (from 200 pg Cd I-') in tube feet and body wall was augmented by 17 vg Se-Se0;I-', whereas higher selenite concentrations were required to augment cadmium uptake in pylonc caeca. In specimens exposed to radioactive cadmium for 2 wk, selenite concentrations at and above 75 @g Se-Se031-' augmented cadmium uptake. A. rubens exhibited concentration factors (expressed on dry weight basis) for cadmium of ca 800 for ambient cadmium concentrations up to 3 pg Cd 1 l ; between 3 and 400 pg Cd 1-', concentration factors decreased from 800 to 100. When exposed to 200 ~cg Cd 1-' alone, A4. edulis took up cadmium at inltlal rates of 9.3, 36, 7.7, 6.4, 24, and 0.8 ,ug Cd g' dry wt d-' in mantle, digestive gland, foot, adductor muscle, gills, and shell, respectively, L. littorea took up cadmium at 11 and 0.6 ,ug Cd g-' dry wt d-' in soft parts and shell, and A. marina took up cadm~um at 6.1 and 10.4 yg Cd g-' dry wt d-' in body wall and gut and 0.23 pg Cd ml-' d-l in blood Uptake proceeded linearly with time over 4 wk exposure in mantle, chgestive gland, foot, and adductor muscle of M. edulis, soft parts of L. littonna, and gut, body wall, and blood of A. marina. In the other tissues uptake rates declined after 1 to 2 wk of exposure. Exposure to an equimolar concentration (141 pg Se-Se03I-') of selenite did not affect cadmium uptake in these 3 species. Exposure to a 5-fold concentration of selenite (703 pg SeSe0;I-') augmented cadmium uptake in gills, mantle, and foot of M. edulis.