Transfer of trace elements from sand to trophic food chains in the Mediterranean coastal areas. A preliminary study, the case of the Calvi Bay, France

Supervisor: Sylvie Gobert (Univ. Liege)
Trace elements bioaccumulation of Al, V, Be, Mn, Co, As, Se, Mo, Ag, Sn, Sb, Bi, Hg as well as of Cr, Fe, Ni, Cu, Zn, Cd, and Pb in the invertebrate and vertebrates (fish) from the Mediterranean coastal areas of the Calvi Bay were analysed using DRC ICP-MS. Data of other compartments in the trophic food chain were collected from the previous doctoral study. The first thirteen trace elements have not been well studied and can be considered to be potential contaminants as a result of potentially increased levels resulting from anthropogenic activities. Considerable variations were observed in the concentration of trace elements among the different components of this ecosystem. The overall trace elements contamination was comparable with other clean to slightly contaminated Mediterranean coastal areas. Except for As and THg, there was no essential biomagnification in trace element concentrations corresponding to the increasing trophic levels. Moreover, the clear trace elements accumulation in primary producers including epiphytes suggesting their high rate of primary production as well as high uptake rates from the water column. High levels of some trace elements (e.g., Sn and Sb) in the primary consumers especially benthic invertebrates reveal the fact of their close contact with sediment particles and interstitial water could be the major source of Sn accumulation in those organisms. The levels of As found increased in the higher consumers, probably due to having biomagnification potential. The concentration of total mercury in the top-predator, generally consumed by human population was remarkably high thus above the EC recommended guideline of 0.5 μg.g-1WW. The calculation of trace elements cycling indicates an insignificant flow in the higher trophic levels of the ecosystem, suggesting a clear bio-dilution. Our findings additionally suggest that the trophic transfer of sediment and macrophyte-bound trace elements to the Calvi Bay coastal food chain is of relatively minor importance.