The biochemical and histopathological analyzes of accumulation of heavy metal on fish tissues in Lake Sapanca

The aim of this thesis is to determine biochemical and histological aspects of the toxic effects of heavy metal pollution on Lake Sapanca. For this reason, fish and water samples were taken by professional fisherman every month of the year 2015 from the Kırkpınar site of the lake. The common carp (Cyprinus carpio), wels catfish (Silurus glanis), rudd (Scardinius erythrophthalmus) and tench (Tinca tinca) were selected as fish species with an economic prescription in fish selection. Analyzes of heavy metals (Cu, Fe, Zn, Pb, and Cd) in water and fish tissues (muscle, liver, and gill) were determined by ICP-OES and compared with reference materials. In addition, catalase enzyme activity (CAT), total glutathione (GSH) and lipid peroxidation (MDA) levels, which are oxidative stress bioindicators in tissues, were measured by spectrophotometric methods. Histopathological findings in the liver and gill tissue were determined by hematoxylin & eosin staining. As a result, the heavy metal concentrations in the water were determined as Fe> Zn> Pb> Cu> Cd. However, the amount of Pb was observed to be higher than the specified standards. The accumulation of Cu, Fe, Pb and Cd in common carp and wels catfish; Cu, Fe, and Pb in rudd; Cu, Fe, Zn and Pb in tench liver>gill>muscle has been determined. The accumulation of Zn in common carp and wels catfish; Zn and Cd in rudd; Cd in tench gill>liver>muscle has been identified. The GSH level in tissues began to decrease in all tissues due to the heating of the air and reached the lowest levels in summer. The highest level of MDA in this study was determined during the summer months when the temperature increased, confirming the presence of significant contamination with low dissolved oxygen content. It has been determined that CAT activity reached its highest level in some winter months when it declined in the summer months. In the gill tissues of fish, general irregularities of lamellae, fusion, edema, and hyperplasia were observed. In the liver, blockage of sinusoids, increase in kupffer cells, and necrotic conditions such as karyolysis in hepatocytes have been observed. In general, the presence of biochemical and histopathological findings in fish tissues suggests that the lake is under the influence of not only heavy metals but also other sources of pollution. This study demonstrated that enzymatic and nonenzymatic antioxidants and histological analyses are useful methods for the biological monitoring of environmental pollution.