Concentrations of metallothionein in the bivalve molluscs Anodonta spp. And Unio spp. from Latvian lakes with different anthropogenic pressure

Concentrations of metallothioneins (MT) were analysed in bivalve molluscs Anodonta spp. and Unio spp. from 6 lakes and watercourses of Latvia with different anthropogenic pressure. The aim of the study was to find the relationship between MT in molluscs and concentrations of heavy metals in sediments. Unio spp. and Anodonta spp. showed no significant differences in the concentrations of MT. High concentrations of heavy metals (Cd, Pb, Hg, Cu, Zn) were detected in the deepest parts of polluted water bodies, however their concentrations significantly decreased in near shore sediments inhabited by molluscs. Only Zn tends to accumulate in the molluscs, reaching 2-7 times higher concentrations in organisms than in sediments. There was statistically significant correlation between MT and Hg due to high affinity of Hg to MT-complex. Concentrations of Hg and MT in molluscs were related also to condition index of molluscs, suggesting that accumulation of heavy metals in molluscs depends on their physiological status.