Interactive accumulation of mercury and selenium in the sea starAsterias rubens

Abstract

Interactions between mercury and selenium accumulation and subcellular binding inAsterias rubens (L.), collected in 1987 from Lille Bælt at Middelfart, Funen, Denmark, were investigated in laboratory experiments. Sea stars exposed to 10µg Hg l⁻¹ for 30 d accumulated mercury in body wall, tube feet and stomach linearly with time at 1.2, 1.2 and 0.5µg Hg g⁻¹ dry wt d⁻¹, respectively. Mercury was accumulated in pyloric caeca and coelomic fluid initially at 1.4µg Hg g⁻¹ dry wt d⁻¹ and 9.4 ng Hg ml⁻¹ d⁻¹, respectively; after 10 d uptake rates decreased. Sea stars exposed to 75µg Se-SeO ^{- -}₃ l⁻¹ accumulated selenium linearly with time over 30 d in the stomach, pyloric caeca, tube feet and body wall at 2.0, 1.2, 1.2 and 0.6µg Se g⁻¹ dry wt d⁻¹. Sea stars exposed to 75µg Se-SeO ^{- -}₄ l⁻¹ maintained selenium levels in the coelomic fluid at 75µg Se l⁻¹ over 30 d. Exposure to selenate did not alter the selenium concentrations in the tissues. Sea stars exposed concurrently to 75µg Se-SeO ^{- -}₃ and 10µg Hg l⁻¹ accumulated more mercury and selenium in tube feet and body wall than did sea stars exposed to the two elements alone. In pyloric caeca and stomach concurrent exposure reduced accumulation of both elements. Mercury was bound predominantly in the insoluble fraction of the tissues, and soluble mercury was bound in proteins of high (> 70 kilodaltons) or very low (< 6000 daltons) molecular weight. Ca. half of the selenium recovered was bound in the insoluble fraction, and soluble selenium was bound in proteins of high (> 70 kilodaltons) or very low (< 6000 daltons) molecular weight. Interaction between the two elements was exerted predominantly in the insoluble fraction of the tissues.