摘要
There has been growing concern about the inflow of metals to the coastal areas because they can be toxic to aquatic and human life. Some studies have demonstrated the existence of species-specific differences in the metal concentrations of mollusks. We compared metal concentrations between Mytilus galloprovincialis, used as a water quality indicator, and two other bivalve species collected for human consumption (Venerupis pullastra and Cerastoderma edule) in different locations on the Galician coast (northwest Spain). M. galloprovincialis was found to be the best zinc and lead accumulator, whereas silver and arsenic were preferentially accumulated by V. pullastra and chromium and nickel by C. edule. Bivalve concentrations of mercury, cadmium, chromium, arsenic, silver, and zinc appeared to be linearly related to environmental concentrations, but this was not the case with copper, nickel, and lead in some species, which indicated that there is a nonlinear accumulation of these metals or an influence of the environmental conditions on species accumulation. The relationship between metal concentration in mussels and in the two other species varied with the metal and the species. In some cases the correlation was high, making it possible to use mussels as bioindicators for the other species. In other cases the correlation was moderate or low, therefore rendering mussels of little or no use in predicting the metal concentrations in the two other species. {texp}Commercial fisheries of bivalves are an important source of income to many coastal populations. Nevertheless, achieving compatibility between harvesting these resources and industrial development is a difficult task. Some industrial activities can produce significant heavy-metal contamination of mollusks as was evidenced by the mercury accidents in Japan, Sweden, Iraq, etc. (Mance 1987; Fergusson 1990). Consequently, the implementation of heavy-metal monitoring programs for shellfish is required to ensure the quality of the edible species. The European Union has dealt with this requirement through Council Directive 91/492/EC. Most national monitoring programs do not analyze the metal concentration in each harvested species and instead use the one or a few species that are assumed to be bioindicator species. Following this approach, metal concentrations in a bivalve species (usually mussels) are used to assess water quality, and it is assumed that all bivalves in good-quality water are safe for human consumption. This method does not hold when the metal accumulation characteristics of the target species are not similar to those of the bioindicator species, making the estimation of the risk incorrect. In Galicia, and in many other European areas, cockles (Cerastoderma edule) and clams (Venerupis pullastra) are species commercially important because of their high production and price. To prevent heavy-metal intoxication in these and other species, mussels (Mytilus galloprovincialis Lmk.) from the area were analyzed for heavy-metal content and used as bioindicators of metal contamination. However, the usefulness of M. galloprovincialis as an indicator of metal contamination in C. edule and V. pullastra has not been checked and—taking into account that several studies have demonstrated different bivalve species to differ substantially in their capability to accumulate various metals (Reinfelder et al. 1997; Wang and Fisher 1999; Chong and Wang 2000; Wang 2001)—it should be checked. Therefore, there is a need to evaluate both the usefulness of mussels as bioindicators and the actual concentrations of metals in these two species to guarantee their safety for consumption. In this study, we attempted to determine the how the metal concentrations of two poorly known species (V. pullastra and C. edule) compare with those of M. galloprovincialis in an area (the Galician coast) with diverse sources of metal pollution. We thus obtained an idea of the risk that these species represent as well as the usefulness of the concentrations found in mussels as an indicator for the other two species.