SEDIMENT FEATURES AND HEAVY METAL LEVELS IN FOUR AREAS OF SARDINIA DEVOTED TO BIVALVE CULTURE

the lagoons of Marceddì, Calich and Porto Pozzo, and in the inner part of the Gulf of Olbia. Sediment of the zones examined were quite similar, except for the Calich lagoon that showed the higher content of total organic carbon. High values of Cd, Pb and Zn were detected in the sediments of the Marceddì lagoon, while remarkable levels of Cu and Mn were found in the Calich lagoon and in the Gulf of Olbia. Key-words: sediment pollution, heavy metals, mollusc culture, Mediterranean Sea. Introduction- Bivalve mollusc culture has greatly increased in Italy during the last years. Along the Sardinian coasts, besides natural bivalve populations of commercial interest, there are a number of areas historically devoted to the mussel (Mytilus galloprovincialis) culture (e.g. the Gulf of Olbia; Bussani, 1983), and several other zones in which the culture of other bivalve species has been tested (Rossi &amp