Role of non-enzymatic antioxidants on the bivalves' adaptation to environmental mercury: Organ-specificities and age effect in Scrobicularia plana inhabiting a contaminated lagoon

This study aimed to investigate the role of non-enzymatic antioxidants on adaptive skills over time in the bivalve Scrobicularia plana environmentally exposed to mercury. Inter-age (2+, 3+, 4+, 5+ year old) and organ-specific (gills, digestive gland) approaches were applied in bivalves collected from moderately and highly contaminated sites at Ria de Aveiro (Portugal). S. plana's adaptive skills were dependent on the contamination extent; under moderate contamination scenario, the intervention of the different antioxidants took place harmoniously, evidencing an adjustment capacity increasing with the age. Under higher contamination degree, S. plana failed to cope with mercury threat, showing an age-dependent deterioration of the defense abilities. In organ-specific approach, the differences were particularly evident for thiol-compounds, since only gills displayed the potential to respond to moderate levels by increasing non-protein thiols and total glutathione. Under high contamination degree, both organs were unable to increase thiol-compounds, which were compensated by the ascorbic acid elevation. - Highlights: ► Results demonstrated non-enzymatic antioxidants' importance on protecting bivalves. ► S. plana's adaptive skills over time depend on the contamination extent. ► Antioxidants intervention evidenced an adjustment capacity increasing with the age. ► Gills responded to mercury moderate levels by increasing thiols and glutathione. ► Ascorbic acid displayed a compensatory role where organs failed to increase thiols. - Results demonstrated the importance of non-enzymatic antioxidants on protecting S. plana from mercury pro-oxidant action, under environmentally realistic conditions.