Mercury bioaccumulation and decontamination kinetics in the edible cockle Cerastoderma edule

Mercury bioaccumulation and decontamination kinetics in the edible cockle Cerastoderma edule were studied through a mesocosms experiment after a medium-term exposure to the metal.The results revealed that the bivalve presented distinct bioaccumulation kinetics according to the different tissues. While the gills showed a linear accumulation pattern, the digestive gland and the entire organism presented a saturation model, with higher accumulation during the first 7d of exposure and lower during the rest of the time. In addition, the bioaccumulation rate was not proportional to the Hg concentration, since the organisms under lower contamination presented higher bioconcentration factors than the ones under higher contamination. Gills were the tissues with higher mercury accumulation capability.Concerning the decontamination phase, C. edule lost approximately 80% of the mercury after 24 h exposure in clean seawater. Nevertheless, never reached the original condition, showing in the final (20 d detox), Hg levels (>0.5 ppm) higher than those allowed by the legislation regulating human food consumption. This represents a matter of concern for Human health.

► Cerastoderma edule presented distinct bioaccumulation kinetics according to the different tissues. ► Gills showed linear model of accumulation while the digestive gland and the entire organism presented a saturation model. ► Organisms under lower contamination presented higher bioconcentration factors than the ones under higher contamination. ► C. edule recorded huge Hg losses (≈80%) after 24 h exposure in clean seawater. ► After 20 d detoxification, the organisms never reached the original condition.