A coastal pollution study: heavy metal content in marine bivalves from the Spanish Mediterranean coast

Levels of heavy metal pollution in coastal environment are increasing continuously due to human activities. The bivalve molluscs are the most widely used as indicators of heavy metal since they concentrate pollutants in their tissues and might provide a time-integrated picture of local contamination. In this study the heavy metal concentrations of both, mussels (Mytilus galloprovincialis) and clams (Donax trunculus) have been studied during a four-year period along the Comunidad Valenciana (Spain) coastline. The soft tissues of mussels and clams have been analyzed for zinc, copper, chromium, nickel, lead, cadmium and mercury. The heavy metal concentrations decrease following the next sequence Zn>Cu>Cr>Ni>Pb>Hg>Cd for the soft tissues of the clams and Zn>Cu>Ni>Cr>Pb>Cd>Hg for mussels. Spatial distribution of heavy metal depends on the kind of anthropogenic sources. Generally those coastal areas close to ports, that bears an intensive maritime traffic and areas with high tourist activity exhibit higher values of metals. Moreover the coastline it is also affected by the massive agriculture developed in the region and punctually industrial areas that discharge high amount of heavy metal to the environment.