Trace metal contamination is often quantified chemically as the environmental or bioaccumulated concentrations. However, they could not explicitly reflect the biological effects associated to the respective metal contamination. In the present study, we adopted a variety of biomarkers of different biological relevance to investigate biological changes under metal exposure in oyster Saccostrea cucullata and Crassostrea hongkongensis in two contrasting metal contaminated system, the Hong Kong coastal waters and the nearby Pearl River Estuary. In the Hong Kong coastal waters, we observed elevated Cd, Cu and Zn bioaccumulation under the influence of the seasonal Pearl River discharge. Biomarkers related to disturbed oxidative balance, as induced lipid peroxidation and depleted glutathione, w...[ Read more ]

Trace metal contamination is often quantified chemically as the environmental or bioaccumulated concentrations. However, they could not explicitly reflect the biological effects associated to the respective metal contamination. In the present study, we adopted a variety of biomarkers of different biological relevance to investigate biological changes under metal exposure in oyster Saccostrea cucullata and Crassostrea hongkongensis in two contrasting metal contaminated system, the Hong Kong coastal waters and the nearby Pearl River Estuary. In the Hong Kong coastal waters, we observed elevated Cd, Cu and Zn bioaccumulation under the influence of the seasonal Pearl River discharge. Biomarkers related to disturbed oxidative balance, as induced lipid peroxidation and depleted glutathione, were significantly correlated to Cu bioaccumulation in oysters. As Cu may potentiate biological impacts even at low concentration, the elevated dissolved Cu concentration reported in this study could also cause Cu-mediated stress to other biota in the Hong Kong coastal environment. Situated at the western side of Hong Kong, the metal-contaminated Pearl River Estuary has shifted metal contamination profile with significant reduced Cr and Ni concentrations whereas Cu and Zn contamination were still evident. In the biomarker responses, biological impacts were slightly alleviated, yet, oxidative stress damages were still prominent in oxidizing lipids and disrupting lysosomal membrane stability. And the responses in metallohionein and oxidative stress could generally explain the up-downstream pattern along the estuary. Despite with contrasting Cu bioaccumulation in oysters from both field studies, there were strong oxidative stress responses in lipids potentially mediated by Cu accumulation. Therefore, we further investigated the link between Cu and lipids, especially on Cu resilience in oyster digestive gland. From the lipidomic perspective, we suggested that efficient Cu sequestration to subcellular compartments, rapid inflammatory responses and phospholipid remodeling in repairing oxidative damages were possible strategies in conferring Cu resilience in Cu-exposed oysters.