Effects of depuration on metal levels and health status of bivalve molluscs

- Depuration of elements is affected by the duration of the process and by species.
- Depuration enabled Pb decrease in Scrobicularia plana to permissible levels.
- Effective depuration of Fe and Pb occurred regardless of species.
- S. plana could only withstand 2 days of depuration in good condition.
- Glycogen has proven to be a suitable biomarker of health status of bivalve species.

Depuration has been mandatory to eliminate microorganisms in bivalve molluscs, but not to eliminate toxic chemicals, since there is still shortage of scientific evidence about the efficacy of depuration to decrease the levels of toxic chemicals in bivalves. This study aims to assess the effects of depuration on the levels of toxic, macro and trace elements in three bivalve species (Ruditapes philippinarum-RP, Mytilus galloprovincialis-MG and Scrobicularia plana-SP), taking into account their condition. During depuration, a significant reduction of elements occurred in RP (Fe, Pb, Cu, Rb, Br, Hg, Cd and As), MG (Cl, Sr, Fe, Pb and Br) and SP (Fe, Pb, Cu and Rb), while an increase was registered for other elements in RP (Cl and Sr), MG (S and Zn) and SP (Cl, Zn, Br and Sr). After two days of depuration, Pb in SP had decreased to levels below the permissible limits, thus allowing this species to be acceptable for human consumption as far as toxic elements are concerned. SP revealed the highest glycogen levels compared to the other species indicating different physiological requirements. However, in this species glycogen levels significantly decreased after two days of depuration and mortality increased. In contrast, in MG and RP glycogen and mortality did not vary significantly during depuration. Therefore, SP should be only depurated for a maximum period of two days. Overall, the results of this study are particularly useful to retailers to ensure high quality bivalve products for consumers. Additionally, glycogen can be used as a suitable biomarker of healthy status of bivalve species during depuration.