Heavy metal bioaccumulation trends in the shell of two Bivalve species: a comparative study.

Bivalves are extensively used in biomonitoring programmes because they’re known to be efficient accumulators of contaminants and ideal indicators organisms. Various species have been used for assess toxic metals levels in marine environment but the most favourite ones are filter feeding Bivalves such as mussels and oysters. In most cases the laboratory experiments are conducted to evaluate the metals concentration levels in soft tissues: few works concentrate their attention also in shell levels. In the optic of a more exhaustive comprehension of the mechanisms that undergo the transfer of inorganic contaminants to organism’s hard parts, it was decided to operate a comparison between two different bivalve species on their ability to accumulate a specific toxic metal. The tests were carried out with standard size organisms in strictly controlled experimental condition in order to assess the extent at which the physiological characteristics of the species affect the metal equilibrium in the organism. The metal concentrations in both shell and soft tissues are analytically determined and subsequently compared to highlight intraspecific correlations and develop a possible explanation of metal partitioning. In addiction it was determined the different species responses to bioaccumulation tests to achieve an indication about their ability in accumulate the selected toxic metal in the shell. This skill could be used in future applications concerning the comprehension and the following exploitation of Bivalves role in water basin self-purification mechanisms.