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Item 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-LRItem Photocatalytic degradation of microcystin-LR using nanostructured rutile and coir fibre(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Idroos, F. S.; Kottegoda, N.; Manage, P. M.Microcystins (MCs) are secondary metabolites of cyanobacteria, which tend to persist in the aquatic environment. Among 70 recorded analogues of MCs, Microcystin-LR (MC-LR) is the dominant and the most toxic cogener. Photocatalytic technology has been constantly recognized as a promising green approach in treating pollutants. The present study records the effective utilization of nanostructured rutile and coir fibre to treat MC-LR. Approximately 2 g of nanostructured rutile and coir fibre (100 nm) were coated in two separate glass slides and dipped in 100 µg/mL of filter sterilized lake water containing 50, 75 and 100 µg/mL of MC-LR. For both nanoparticles (rutile and coir fibre) at 50, 75 and 100 µg/mL of MC-LR concentrations, two experimental set ups (A-Exposed to sunlight, B-Exposed to 12 W UV light) and two control set ups (A1-Control exposed to sunlight, B1-Control exposed to 12 W UV light) were maintained. Sample aliquots of 1 mL was removed at every 30 minutes interval for a period of 3 hours. Subsequently, samples were subjected to freeze drying followed by reconstitution in 50% HPLC grade methanol and analyzed under PDA-HPLC to quantify the remaining MC-LR concentrations. Under the influence of UV light, nanostructured rutile showed, 100 % removal of MC-LR at 50 and 75 µg/mL within 1.5 hours and 2 hours respectively, whereas 87.4 ± 2.31% removal for 100 µg/mL of MC-LR was recorded at the end of 3 hours. When the same experiment was repeated by exposing to sunlight, MC-LR removal percentages were 77.29 ± 1.9 at 50 µg/mL, 36.4 ± 3.8 at 75 µg/mL and 19 ± 3.78 at 100 µg/mL. Moreover, when nanostructured coir fibre was used under 12W UV light, 100% removal of 50 µg/mL MC-LR, was evident at 2 hours, whereas 85.68 ± 9.4% for 75 µg/mL and 56.2 ± 4.37% for 100 µg/mL was observed at the end of 3 hours. At the exposure to sunlight, nanostructured coir particles showed 72.4 ± 2.3 at 50 µg/mL, 56.2 ± 8.2 at 75 µg/mL and 46.8 ± 6.98 at 100 µg/mL at the end of 3 hours. Two-way ANOVA confirmed that there is a significant difference in the MC-LR photocatalytic degradation ability of nanostructured rutile and coir fibre (P=0.02). Therefore, it could be concluded that nanostructured rutile is effective than coir fibre based nanoparticles in treating MC-LR contaminated water. Furthermore, UV exposure of both types of nanostructures can enhance photocatalytic degradation of MC-LR.