Browsing by Author "Weerasekara, K. A. W. S."

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    Cadmium and arsenic levels in edible fi shes, Oreochromis niloticus (Nile tilapia) and Ompok bimaculatus (butter catfi sh) from Padaviya Reservoir, Sri Lanka and human health risk assessment associated with their dietary exposure
    (2020) Weerasekara, K. A. W. S.; Pathiratne, A.; Kithsiri, H. M. P.
    Consumption of fi sh contaminated with toxic heavy metals is a threat to human health. Cadmium and arsenic are suspected as potential risk factors for chronic kidney disease of unknown aetiology (CKDu), which is highly prevalent in agricultural settlements in dry zone districts of Sri Lanka causing a severe public health crisis. Objectives of this study were (i) to determine cadmium and arsenic levels in muscle, liver and kidney of two edible fi shes (Nile tilapia and butter catfi sh) from the Padaviya reservoir located in the North Central Province, Sri Lanka where CKDu is highly prevalent and (ii) to assess the potential human health risks associated with the dietary exposure through edible muscle of these fi shes. Cadmium and arsenic levels of the tissues in the two fi sh species were determined using inductively coupled plasma mass spectrometry. In both fi sh species, highest cadmium levels were found in kidney (p < 0.05) whereas no signifi cant tissue specifi c diff erences (p > 0.05) were evident for arsenic. In the edible muscle, the maximum detected cadmium level in Nile tilapia was 0.1 mg/kg in wet weight. However, cadmium levels in the muscle of all Butter catfi sh were < 0.05 mg/kg. Arsenic levels in the muscle of all Nile tilapia and Butter catfi sh were < 0.05 mg/kg. Cadmium contents in muscle of most fi shes and arsenic contents in all fi shes (n = 60) were within the maximum permissible limits set by the international food standards regulatory authorities. Based on the estimated daily intake and target hazard quotients (< 1) for lifetime exposure, it is highly unlikely that cadmium and arsenic contents of the muscle meat of these fi shes would pose human health risks to moderate level consumers.
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    Plankton diversity in Bomburuella reservoir, Nuwara-Eliya: A preliminary survey
    (Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Hettige, N. D.; Weerasekara, K. A. W. S.; Chandrasiri, E. G. D. N.; Jayawardene, J. M. C. K.
    Bomburuella is a perennial reservoir located in the Nuwara-Eliya district. This reservoir is mainly used for fisheries, agriculture and drinking purposes. Although, a number of studies have been carried out to assess the water quality of this reservoir, there is a dearth of information on the plankton diversity. Therefore, a study was carried out to determine the species composition of zooplankton and phytoplankton in the reservoir. Plankton were collected using 55 µm open type nylon plankton net from 10 sampling locations in the reservoir over a four-month period from February to May in 2014. Plankton were identified to highest possible taxonomic levels using standard plankton identification guides. Average species richness and diversity of the plankton were also estimated. Dissolved Oxygen (Orion 830A), pH (Orion 260A), turbidity (Hatch 2100P), water temperature, conductivity, total dissolved solids and salinity (Hanna multi range conductivity meter, HI 8733) were determined in in situ using portable meters . In addition, water samples were analyzed for ammoniacal-N, nitrate-N, nitrite-N and orthophosphate at the laboratory using standard methods. Two replicates were analyzed for both plankton and water samples. The correlation between plankton species and water quality parameters were assessed using Pearson correlation coefficient using MINITAB 14.0 statistical software. A total of 28 phytoplankton taxa belonging to the five major divisions namely Chlorophyta, Cyanophyta, Dinoflagellata, Bacillariophyta and Ochrophyta were identified. Coscinodiscophyceae is the most abundant phytoplankton (32.84%) group followed by Melosira granulata (16.23%) and Rhizosolenia sp. (11.82%). Toxin producing Microcystis sp. was also recorded (7.58%). In addition to the above phytoplankton, a total of 21 zooplankton species belonging to Arthropoda (73%) and Rotifera (27%) were identified. Of them, Keratella cochlearis (70.46%) and Cyclops prasinus (10.92%) were the most abundant zooplankton species. The mean of the ShannonWiener diversity index (<2) of phytoplankton and zooplankton recorded were 1.55 ± 0.61 and 1.02 ± 0.62 respectively indicating high water pollution status of the reservoir. Only the correlation between number of phytoplankton and zooplankton species with nitrate - nitrogen showed a moderate (r=0.428) and strong (r=0.568) positive correlation respectively at 5% level of significance. The findings of the study can be used as a baseline study to estimate the pollution status of the Bomburuella reservoir. Further studies are recommended to investigate the plankton diversity and status of water pollution in the reservoir with seasonal variations.