| Abstrakt: |
Chemical residues from aquaculture, especially heavy metals, are harmful to environment. The present study assessed the seasonal dynamics and potential toxic effects of heavy metal accumulation (Cr, Cu, Zn, and Pb) in lake sediments within the impact zone of the trout cage farm (Lake Ladoga, Russia). The tasks included the layer-by-layer analysis of total content of the heavy metals and their labile forms in sediment cores collected in the winter and autumn seasons. Four sites located directly next to the cages and three reference sites (150, 600, and 1,000 m from the farm) were studied. Sediments cores collected using gravity corer were analyzed for total content analysis, where sediment samples were decomposed with strong acids (HClO4, HF, HCl, and HNO3), and the labile forms were extracted by ammonium acetate. The results showed that sediments under fish cages were significantly polluted by Zn and Cu especially towards the end of the active feeding period (autumn), thus potentially increasing sediment toxicity. Therefore, Zn and Cu can be utilized as geochemical markers for assessing the thickness of the accumulated contaminated sediment layer in the impact zone of cage farms. Pollution of the sediments by heavy metals is local and limited to the studied bay. Hence, there is no risk of secondary pollution of the water column according to the RAC index. However, the absolute content (mg·kg-1) of labile Zn is much higher under the cage than at reference sites. [ABSTRACT FROM AUTHOR] |
