Heavy Metals and PAH Assessment Based on Mussel Caging in the North Coast of Tunisia (Mediterranean Sea)

In the framework of the Mytilos project (Interreg IIIB Medocc), international research cruises were carried out in 2006 in order to evaluate the level of Heavy metals and polycyclic aromatic hydrocarbons (PAH) along the coast of the western basin of the Mediterranean Sea. Caged mussels (Mytilus galloprovincialis) were placed in situ at six sites in the North coast of Tunisia. Results showed total PAH levels were in the range 45.6-241.6 ng/g dry weight (dw). The ranges of trace metals concentrations expressed in µg/gdw are: Hg (0.1- 0.2), Pb (0.4-0.7), Cd (0.9-2.9), Cu (2.9-3.9), Fe (117-248) and Zn (250-426). Higher concentrations were observed at Rades, La Galite and Tabarka which can be attributed to the industrial activities implanted in the coast of Algeria and in the city of Rades. Concentrations of PAH, Cd, Pb, Fe and Zn are generally different from initial concentrations (before caging), depending on the adaptability of transplanted mussels to be used as bio-indicator of contaminants. Yet bio-monitoring using mussels give information on compound bioavailability which depends on their ability to accumulate contaminants in its tissue.