ACCUMULATION AND SUBCELLULAR-DISTRIBUTION OF METALS (CU, FE, MN, PB AND ZN) IN THE MEDITERRANEAN MUSSEL MYTILUS-GALLOPROVINCIALIS DURING A FIELD TRANSPLANT EXPERIMENT

Marine mussels are generally used as biomonitors of heavy metal pollution in coastal areas. However, the time-integration capacity of these molluscs may vary from different metals and this fact should be considered when interpreting heavy metal concentrations in natural mussel populations. The aim of this work was to investigate the uptake-excretion kinetics and the subcellular distribution of metals in field conditions: the results were expected to provide useful information on the different time-integration capacities of mussels for various elements. Mussels from a clean site were transplanted to a heavy metal polluted environment where they acumulated Pb, Fe, and Mn. The accumulation was not linear but a steady state was reached after only 2 weeks, indicating that mussels can rapidly equilibrate with enhanced environmental levels of these pollutants. Copper and zinc were not accumulated by transplanted mussels, suggesting a similar bioavailability in the two environments or a certain regulation capability of molluscs for these essential elements. Polluted mussels, allowed to depurate in clean seawater, showed excretion rates which were different between elements. Moreover the subcellular distribution was characteristic for each metal but the patterns were similar in wild populations as well as in transplanted and depurating mussels, indicating that the same subcellular fractions are involved in the uptake, storage and excretion of metals. From the results, the different time-integration capacities of mussels for various elements appear to be related to the cellular mechanisms involved in their detoxification and/or excretion.