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Accumulation of Pb and Cd in the gills and liver of Vardar chub (Squalius vardarensis) from the mining impacted rivers in the north-eastern Macedonia

Active Pb-Zn mines in the north-eastern Macedonia, Zletovo and Toranica, are known to cause degradation of the environmental status of the regional rivers. As a consequence of the leaching from the mine tailings or direct input of the mine waste into the rivers, increased concentrations of several metals were found in the Zletovska and Kriva rivers compared to the reference area, downstream section of the Bregalnica River. Dissolved Cd was found increased in both Zletovska and Kriva rivers (0.27 µg L-1), whereas dissolved Pb was found increased only in the Kriva River (1.85 µg L-1). Both Pb and Cd are regarded as the priority toxic substances by the European Water Framework Directive, but only Cd has exceeded the European recommendations. The aim of this study was to assess if increased Pb and Cd concentrations in the river water have resulted with the increased bioaccumulation of these metals in two selected organs (gills and liver) of bioindicator organism, Vardar chub (Squalius vardarensis). In May/June 2012, 30 chub specimens were sampled in each river, and their gills and livers were dissected. Metal concentrations were measured in the soluble tissue fractions, i.e. in supernatants obtained after tissue homogenization and centrifugation at 50, 000×g, by high resolution inductively coupled plasma mass spectrometry. The comparison of metal concentrations in two organs indicated more pronounced Pb accumulation in the gills than liver, whereas higher accumulation in the liver was observed for Cd. Nevertheless, both organs revealed the same spatial pattern of metal bioaccumulation, which reflected metal contamination of the river water. Cytosolic Pb concentrations were the highest in the gills and the liver of the chub from the Kriva River, whereas cytosolic Cd concentrations were higher in the gills and the liver of the chub from both Kriva and Zletovska rivers compared to the least contaminated Bregalnica River. Furthermore, the association of metal bioaccumulation with several biometric parameters was analyzed, but no clear pattern was observed, except for the gender related differences. At higher level of metal exposure, such as observed in the Kriva and the Zletovska rivers, Pb and Cd were significantly higher in the liver of males than females, whereas opposite trend was observed for Cd in the gills. Our results pointed to possible use of cytosolic Pb and Cd concentrations in both gills and liver of Vardar chub as indicators of metal exposure in the river water.

active mines ; cadmium ; gills ; lead ; Vardar chub

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