International Research Symposium on Pure and Applied Sciences (IRSPAS)

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    Microcystin -LR contamination status of Nile tilapia (Oreochromis niloticus) and biomarker response
    (4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Abeysiri, H. A. S. N.; Wanigasuriya, K.; Manage, P.M.
    Microcystin-LR (MC-LR) is a cyanotoxin derived from some cyanobacteria. Nile tilapia (Oreochromis niloticus) is the most popular freshwater fish among people in Sri Lanka. MC-LR accumulation in tilapia from thirteen reservoirs; Nallachchiya Wewa, Galkulama Wewa, Anakattiya Wewa, Padaviya Wewa, Nachchaduwa Wewa and Kalawewa in Anuradhapura District and from four reservoirs; Parakrama Samudraya, Halmilla Wewa, Kaudulla Wewa and Ambagas Wewa in Polonnaruwa District Muwapatigewela Wewa in Ampara District and Ulhitiya Wewa and Rathkinda Wewa in Badulla District was determined to evaluate the risk posed by the MC-LR contamination in fish on human health. Sample collection, transportation and analysis were followed according to the standard protocols and MC-LR was quantified by High Performance Liquid Chromatography. Fish skin, flesh and head were analyzed for MC-LR and Tolerable Daily Intake (TDI) values were calculated according to the WHO guidelines. MC-LR levels of fish in different reservoirs were compared with WHO standard of TDI (0.04 μg/kg/day). MC-LR level of fish skin (717.14 ± 0.82 μg/kg), flesh (105.11±0.08 μg/kg) and head (553.24±0.12 μg/kg) collected from Padaviya Wewa were recorded the highest mean concentrations of MC-LR. The mean concentrations of MC-LR in the skin and head of fish were significantly higher than that of flesh (p<0.05). The Average Daily Intake of MC-LR in the skin and head of all fish exceeded the provisional TDI set by WHO. Thus, the results of the present study revealed that consumption of head and skin of fish has a potential risk on accumulation of MC-LR in human body. Cyanobacterial toxins have been shown to affect aquatic organisms such as fish, resulting in oxidative stress. Among the antioxidant enzymes, glutathione peroxidase (GPx) plays an important role in the detoxification of MCs. Fish tissues such as head, flesh and skin were obtained for “GPx” gene expression analysis and results showed availability of detoxifying enzymes in fish skin and head collected from Parakrama Samudraya, Padaviya Wewa, Nallachchiya Wewa and Galkulama Wewa. MC-LR contamination in Galkulama Wewa showed a negative result. Therefore, previous exposure of fish for MC-LR shows indicator of the expression of gene of any detoxifying enzyme. Therefore, the results support the use of GPx in fish as a biomarker to assess the contamination by MC-LR
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    Cadmium and arsenic levels in edible fishes, Oreochromis niloticus (Nile tilapia) and Ompok bimaculatus (Pena walaya) from Padaviya reservoir of North Central Province, Sri Lanka
    (Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Weerasekara, K.A.W.S.; Pathiratne, A.; Kithsiri, H.M.P.
    Oreochromis niloticus (Nile tilapia) and Ompok bimaculatus (Pena walaya) are two edible fish species captured in the reservoirs in the North Central province. Objective of this study was to assess the cadmium and arsenic levels in muscle, liver and kidney tissues of O. niloticus and O. bimaculatus inhabiting the Padaviya reservoir to assess association of metal/metalloid levels in tissues with body weights, and total lengths of the fishes. The body weight (180-300g; 110-225g) and the total length (19.0-24.1cm; 24.0-34.0cm) of Nile Tilapia (n=30), and Pena walaya (n=30) respectively were recorded during three sampling events in 2018. The tissues were analyzed for cadmium and arsenic levels using Inductively Coupled Plasma Mass Spectrometry. Cadmium and arsenic contents of the muscle tissues were below the limit of detection (LOD) (<0.05 mg/kg wet weight) except cadmium in the muscle tissues of five Nile tilapia (0.05-0.10 mg/kg). Cadmium contents in the liver tissues of both Nile tilapia and Pena walaya, ranged from <0.05 to 0.14 mg/kg (wet weight) where cadmium levels of 67-70% of the fishes were below the LOD. Arsenic levels in liver tissues of Nile tilapia and Pena walaya were <0.05–0.10 mg/kg and <0.05–0.06 mg/kg respectively where arsenic levels in 83% of Nile tilapia and 97% of Pena walaya were below the LOD. Cadmium content in the kidney tissues of Nile tilapia and Pena walaya were <0.05-0.90 mg/kg and <0.05-0.40 mg/kg respectively where cadmium levels in 30% and 33% fishes were below the LOD. Arsenic was detected only in kidney tissues of 10% Nile tilapia (<0.050.46 mg/kg). Cadmium contents in liver tissues of Nile tilapia positively correlated (p <0.05) with the total length. No other significant associations were found between the metal/metalloid content in the tissues and the body size of the fishes. Results revealed that the cadmium and arsenic contents in the edible muscle tissues of most of these fishes were within the safe limits specified by the regulatory authorities for human consumption. Bioaccumulation pattern of cadmium in the tissues of both fishes followed the order: muscle < liver < kidney, showing greater cadmium bioaccumulative capacity in the kidney tissues. Periodic monitoring of metal/metalloid levels in edible fishes in Padaviya reservoir is recommended considering human safety. The data generated in this study can serve as baseline information for future monitoring and human health risk assessment programmes.