Metal concentrations in archaeological and contemporary mussel shells (Unionidae): Reconstruction of past environmental conditions and the present state.

Freshwater mussels are widely used in the monitoring of pollution because they are filter-feeding, long-lived animals that tend to accumulate metals in their shells. The temporal scale of such studies can reach thousands of years, since the composition of shells preserves them against decay. This allows us to reconstruct past environmental conditions and to compare current environmental conditions to those prevalent thousands of years ago. Here we assessed metal concentrations (Ca, Cd, Cr, Cu, Fe, Hg, Ni, Pb and Zn) in recently harvested mussel shells and mussel shells found by archaeologists, and tested the hypothesis that levels of some metals are higher in today's shells, reflecting increasing anthropogenic impact. We observed lower metal concentrations (with the exception of Cd) in shells found by archaeologists (n = 35) than in recently harvested mussel shells (n = 14) (Unio crassus, Unio pictorum, Unio tumidus) in the same water bodies. There were no significant differences in metal levels among species in shells found by archaeologists, while in recently harvested mussels almost all metals for which we tested were found in their highest levels in Unio crassus. The results suggest that metal concentrations in prehistoric times were lower than today, which probably reflects human impact, rather than changes in the geochemical structure of rocks. The results also revealed that metal transfer between mussel shells and surrounding deposits does not occur. We therefore suggest that they might be successfully used as independent bioindicators.

Levels of metals in kidney, liver and muscle tissue and their relation to the occurrence of parasites in the red fox in the Lower Silesian Forest in Europe.

Together with the occurrence of parasites, increased concentrations of xenobiotics, to which scavengers are greatly exposed, may significantly influence the physiology of red foxes. It is also suspected that these two factors interact. The accumulation of various metals (Ca, Cd, Cu, Fe, Hg, K, Mg, Ni, Pb, Zn) in kidney, liver and muscle tissue was investigated, as well as the occurrence of parasites, and the potential link to the presence of metals. Generally speaking, neither sex nor age influenced these concentrations. K, Mg and Fe were found in the highest concentrations and Hg was found in the lowest. Various relationships between the concentrations of metals were observed in the tissues. 34% of the specimens studied were hosts to parasites. No clear, significant connection between the concentrations and the occurrence of parasites was noted, but the discernible trend confirmed by the logistic regression, needs further study.

Levels of Total Mercury in Tissues of Mallard Drakes from Industrialized Wetlands Area.

The distribution of total mercury in the bodies of drake mallard ducks (Anas platyrhynchos) inhabiting an industrialized wetland area in southern Poland was studied. The median Hg concentration in tissue of various bones (0.017 µg/g w.w.) was statistically lower than the concentration found in muscle tissue (0.023 µg/g w.w.) and in internal organ tissue samples calculated across the whole range of organ types (0.036 µg/g w.w.). The median concentrations in muscle tissue and organ tissue were comparable. Significant differences within the examined bones were observed, with the beak accumulating the highest amount (0.105 µg/g w.w.). Concentrations were comparable in tissue from various muscles, whereas internal organ tissue displayed a significant variation. The highest median concentration was detected in the kidneys (0.109 µg/g w.w.). Correlations of Hg concentrations between major groups of tissue (i.e. bone, muscle and internal organs) were not statistically significant, but several significant relationships were noted between internal organs.