Bioaccumulation of heavy metals in water, sediments, and tissues and their histopathological effects on Unio tigridis (Bourguignat 1852)

The current study assessed the accumulation rate of four heavy metals (i.e., Cu, Zn, Cd, and Pb) in water, sediment, and tissues of the freshwater mussels Unio tigridis . The trace metal concentrations in water, sediment, and tissues showed the following decreasing trend: Zn (mean W: 31.08 mg/L; mean S: 10.495 mg/g; and mean T:4.925 mg/g) > Cu (mean W: 6.538 mg/L; mean S: 46.712 mg/g; and mean T: 17.127) > Pb (mean W: 31.08 mg/L; mean S: 10.495 mg/g; and mean T:4.925 mg/g) > Cd (mean W: 0.277 mg/L; mean S: 0.77 mg/g; and mean T: 0.674 mg/g), and the toxic metal concentrations exceeded the recommended acceptable limits. Necrosis, blood cell infiltration, atrophy, epithelium damage, brown cells, and fat agglomerates were the most common histological changes found in the digestive glands of mussels. These histopathological lesions can be considered reliable biomarkers in biomonitoring programs for heavy metal contamination in aquatic ecosystems.