The use of biomarkers as early-warning signals to assess the impact of pollutants and other environmental stressors in coastal habitats has been internationally recognized as a useful tool in marine coastal monitoring. We propose a similar approach to verify the welfare of edible shellfish, Ruditapes philippinarum, thus exploiting its possible application as an effective tool to verify the origin of fishing/aquaculture products. A selected battery of biomarkers was chosen and applied to organisms from two different habitats in the Lagoon of Venice (a farming site and a natural area where fishing is currently banned, because of pollution problems) and from a local market. Biological responses were evaluated physiologically (survival in air test and condition index), behaviourally (reburrowing rate), and histochemically (quantification of neutral lipids and lipofuscin). Micropollutants (heavy metals, PCBs, and PAHs) were also determined in the soft tissues. Results indicated clams from the farming site were in the best condition with regard to both chemical and biological measurements. In contrast, the market sample contained the highest concentrations of PAHs. PCBs and heavy metals varied slightly and quite irregularly among the three samples. The worst values of the biomarkers were observed for clams collected at the polluted site, where, in particular, the lowest physiological and behavioural indexes and the highest accumulation of lipofuscin in the digestive tissue were recorded.
