Heavy metal presences in benthic fauna as monitoring tool in the establishment of protected marine areas.

Heavy metals can be considered among major marine pollutants, presenting toxicological and accumulation problems in different environmental compartments. Even if they are present in all living organisms, their passage from one level to the other of the trophic chain is till now little or no studied. In present work we wanted to evaluate the transfer intensity of heavy metals (As, Cd, Co, Cr, Cu, Fe, Hg, Ni. Pb, Se) along a short, 4 steps trophic chain, composed by benthic and pelagic species, ending with bottlenose dolphin (Tursiops truncatus) as top predator. Samples (n= 30) from 3 species belonging to trophic level (TL) 1, 7 from TL 2, 5 from TL 3 and finally from tissues of stranded bottlenose dolphins were collected in Romagna area (Italy). Samples were microwave digested and analyzed with ICP-OES technique. Analytical results were used to calculate the biomagnification factor (BMF), as ratio between the upper level and the lower level specie concentration (BMF= Cn/Cn-1). When bottlenose tissue were considered, the BMF was calculated for each single tissue, to identify the “marker” tissue for each metal. Obtained results underline how contamination levels are to be considered as low for all of the species and all of the metals, with the only exception of Natica hebraea and Hinia reticulate, presenting very high levels of arsenic. Notable is the data concerning BMF calculation, that showed to be extremely variable not only depending on species, but also on different trophic level. Indeed, BMF for all toxic metals is lower than 1 in higher and lower levels, while it is always higher than 1 in intermediate level. This data is indicative of a strong concentration of toxicant in this trophic level. As concerns essential metals, BMF is always higher than 1, as expected considering their physiological role, thus indicating an active absorption and accumulation. Such an accumulation profile is to our knowledge not so common and presents interesting aspects concerning contaminants transfer, as it seems to underline, at least in the short food-chain we considered, a basic and “amplifying” role for intermediate predators in toxicant accumulation. It should anyway remembered that the contribution of each of the species considered to the contaminant burden of the species at upper level is influenced by the percent these species represent in total diet of their predators