John Wiley & Sons, Ltd.

Depuration of metals by the green‐colored oyster Crassostrea sikamea

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Green‐colored oysters are now found in Chinese estuaries due to their accumulation of metals (especially copper). In this study, we specifically quantified the depuration of eight metals (Ag, Cd, Co, Cr, Cu, Ni, Pb, and Zn) in green‐colored oysters (Crassostrea sikamea) collected from an estuary heavily contaminated by metals due to industrial effluent releases. The oysters were depurated under laboratory conditions for 4 months; the accumulated concentrations as well as the subcellular distribution of metals were measured at different time intervals. Results showed that the green color of oysters faded to light yellow (nearly normal) after four months of depuration. Depuration of metals could be described by a first‐order kinetic process. The calculated overall depuration rate constants of metals were in the range of 0.008–0.024 d−1, with a biological retention half‐life of 30–70 days. The depuration rates of green‐colored contaminated oysters were significantly higher for Cd, Cu, Cr, and Ni than those from a less contaminated site, whereas the depuration rates of Ag, Co, Pb and Zn were comparable between the two populations. When corrected for the change of oyster tissue weight, the actual efflux rate constants of the metals (0.0708–0.1014 d−1) were much higher than the overall depuration rate constants. Cellular debris and metallothionein‐like proteins were the important fractions binding with the metals in the oysters. Significant changes in metal subcellular distribution were observed during the 4‐month depuration for Ag, Cd, Cu, and Zn. Metallothionein‐like protein became more important in sequestering the metals during the depuration period, with concomitant decrease of metals associated with the cellular debris fraction. Environ Toxicol Chem © 2014 SETAC

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