Metals and As content in the sediments and Manila clam Ruditapes philippinarum in the Tagus estuary (Portugal): impacts and risk for human consumption

The Manila clam is emerging as a relevant species for the Portuguese market. The present work was conducted in the Tagus estuary to evaluate 1) the metals and As content in the sediments of the Tagus estuary, especially on those areas subjected to Manila clam harvesting 2) the metals and As content in clams, and the risk associated with their consumption 3) the physiological and biochemical responses of the clam to metals and As contamination, and its possible role as a pollution bioindicator in the estuarine environment. The most contaminated sediments were identified nearby industrial areas, nevertheless clams collected in low contaminated areas showed high metals and As concentrations. The condition index, glycogen content, membrane oxidative damage, biotransformation enzymes and metallothioneins showed consistent responses to metals and As content in clams. Results emphasize the need for the development of a management plan for the species exploitation in the Tagus estuary.