Browsing by Author "Pathiratne, A."

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A comparative study of the effects of benzene, toluene and xylenes on their in vitro metabolism and drug metabolizing enzymes in rat liver
(Toxicology and Applied Pharmacology, 1986) Pathiratne, A.; Puyear, R.L.; Brammer, J.D.
Accumulation of lead, cadmium and copper in brackishwater clam, Meretrix casta from selected estuaries in Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2009) Amarasekara, E.A.K.K.; Pathiratne, A.; Wanninayake, W.M.T.B.
Accumulation of Lead, Cadmium and Copper in food fish, Oreochromis mossambicus in Beira Lake, Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2002) Anil, K.A.; Pathiratne, A.
Acetylcholinesterase inhibition and gill lesions in Rasbora caverii, an indigenous fish inhabiting rice field associated waterbodies in Sri Lanka
(Kluwer Academic Publishers-Plenum Publishers., 2006) Wijeyaratne, W.M.D.N.; Pathiratne, A.
The present study was aimed at applying condition factor (CF), brain acetylcholinesterase (AChE) and gill histology as biomarkers for detecting possible exposure/effect induced by pesticides in fish residing rice field associated waterbodies in Sri Lanka. Biomarkers of an indigenous fish, Rasbora caverii collected from five sampling sites including canals near rice fields, a river and a reservoir (the reference site) were evaluated at four sampling stages covering pesticide application periods during rice cultivation season in 2004. Results indicated that CF of the fish did not show significant alterations regardless of the sampling sites or sampling stages. Site specific differences in AChE activities of the fish were not evident either prior to application of pesticides or at 7 days after Paraquat application to the rice fields. Two days after the application of a mixture of Fenthion and Phenthoate to the rice fields, AChE activity of the fish collected from canals near rice fields was significantly depressed (65–75%) compared to the fish in the reference site. The activities remain depressed to 50–56% even at 65 days after the insecticides application. Laboratory studies showed that prior exposure of R. caverii to Paraquat (2 μg l−1, 7 days) enhanced the extent of inhibition of brain AChE activity induced by Fenthion (3 μg l−1) or a mixture of Fenthion (3 μg l−1) and Phenthoate (5 μg l−1). Gills of fish collected from canals near rice fields exhibited abnormal multiple divisions at the tips of some secondary lamellae in addition to hyperplasia, hypertrophy and club shaped deformities. Results indicate that application of pesticides in rice culture could manifest a threat to native fish populations residing rice field associated waterbodies. The response of brain AChE and histological changes in the gills of R. caverii allowed differentiating sampling sites after insecticide applications to the rice fields. Hence, R. caverii may be considered as a surrogate species in ecotoxicological risk evaluation of agrochemicals in the region.
Acetylcholinesterase inhibition in Nile tilapia, Oreochromis niloticus following exposure to low concentrations of Chlorpyrifos and Carbosulfan: exposure– response relationships in fry, fingerlings and sub-adults
(Sri Lanka Association for Fisheries and Aquatic Resources, 2004) Chandrasekera, L.W.H.U.; Pathiratne, A.
Acetylcholinesterase (AChE) inhibition is considered as a specific biomarker of exposure and effect for organophosphorous and carbamate pesticides. Oreochromis niloticus, which is an abundant food fish in inland water bodies is a potential sentinel species in monitoring biological effects of pollutants in aquatic environments in Sri Lanka. In the present study, pesticide exposure and AChE inhibition relationships in different size groups of O. niloticus were assessed under laboratory conditions following exposure to an organophosphate, Chlorpyrifos and a carbamate, Carbosulfan, to evaluate the influence of body size on exposure-response relationships. Fry (0.9-2.0 g, 3.2-4.8 cm), fingerlings (3.0-9.7 g, 5.9-8.5 cm) and sub-adults (11-40 g, 9.2-15.0 cm) of fish were continuously exposed to a series of environmentally relevant concentrations of Chlorpyrifos (0.5 –12 g l-1) or Carbosulfan (1 –10 g l-1) for 14 days in a static system and brain AChE activities on 2, 6, 10, 14 days post exposure were determined using the standard spectrophotometeric method. Comparable size groups of fish maintained in aged tap water under similar laboratory conditions served as controls. Results showed that AChE activities in all groups of fish were inhibited following exposure to the insecticides tested in a concentration dependent manner. Exposure-response relationships indicated that fry stages were more sensitive to the pesticide exposure in comparison to the fingerlings and sub-adults. AChE activity of fingerlings and sub-adults exposed to 1 g l-1 Chlorpyrifos or Carbosulfan restored to near normal levels in 14 days post exposure whereas the activities of the fish exposed to other concentrations remained significantly inhibited even after 14 days. The results suggest that brain AChE activity in O. niloticus could be used as a sensitive molecular biomarker in monitoring organophosphorus and carbamate pollution in aquatic environments. However, the size groups of the fish should be taken into consideration when this fish is used in environmental monitoring
Acetylcholinesterse inhibition and gill lesions in Rasboracaverii, an indegeneous fish inhabiting rice field associated waterbodies in Sri Lanka
(Ecotoxicology, 2006) Wijeyaratne, W.M.D.N.; Pathiratne, A.
Activation of C14 toluene to covalently binding metabolites by rat liver microsomes
(Drug Metabolism and Disposition, 1986) Pathiratne, A.; Puyear, R.L.; Brammer, J.D.
Analysis of bile fluorescence profiles of feral Nile tilapia as biomarkers of exposure to polycyclic aromatic hydrocarbons: associations with the rainfall
(Sri Lanka Journal of Aquatic Sciences, 2011) Hemachandra, C.K.; Pathiratne, A.
The present study was conducted to evaluate the potential use of bile fluorescence patterns of feral Nile tilapia (Oreochromis niloticus) as biomarkers of exposure to polycyclic aromatic hydrocarbon (PAH) contaminations in tropical waters. Bile fluorescence profiles of the fish inhabiting two water bodies with different levels of PAH pollution (Weras Ganga and Bathalagoda reservoir) were investigated at regular intervals over two years (September 2007 to July 2009) using fixed wavelength fluorescence and synchronous fluorescence spectrometry. Despite temporal variability of the bile fluorescence patterns, the fluorescence signals corresponding to naphthalene-, phenanthrene-, pyrene- and benzo(a)pyrene- type metabolites were consistently higher in the fish from Weras Ganga compared to the fish from Bathalagoda reservoir and the laboratory maintained control fish indicating that the fish inhabiting Weras Ganga had been continuously exposed to higher levels of PAHs. Summated fluorescence for the four types of PAH metabolites and fluorescence signals corresponding to naphthalene- and pyrene- type metabolites in the fish from Weras Ganga were positively correlated (P < 0.05) with the rainfall pattern indicating more PAH inputs associated with the rainfall. Despite slight temporal variations, no significant associations were found between the biliary fluorescence signals in the fish from Bathalagoda reservoir and the rainfall pattern. This field study supports the use of bile fluorescence patterns in feral Nile tilapia as a simple and rapid method for screening contamination and bioavailability of PAH in tropical freshwater bodies.
Analysis of elemental profiles in selected industrial effluents reaching Kelani River using inductively coupled plasma spectrometry
(Sri Lanka Association for the Advancement of Science, 2013) Pathiratne, K.A.S.; Pathiratne, A.; Hemachandra, C.K.; de Silva, N.
Application of cytogenetic model Allium cepa for screening potential cytogenotoxicity of herbal-based hair dyes
(Journal of Environmental Science and Health, 2020) Nawalage, K. S.; Pathiratne, A.
Plant models may be useful as test organisms for initial screening of potential toxicity of personal care products. The objective of the present study was to assess the efficacy of the Allium cepa (common onion) test system as a bioanalytical tool for screening potential cytotoxicity and genotoxicity of herbal-based hair dye formulations. Exposure of black hair dye formulations for 48 hours resulted in root growth retardation and mitosis suppression in the root meristems of A. cepa bulbs indicating concentration dependent cytotoxicity. At the 72 hour post exposure, cytotoxic effects on the roots were reduced but not recovered completely signifying prolong toxic action of the hair dyes. The condensed nuclei was the most frequent nuclear abnormality found in the dye exposed root meristematic cells indicating the cell death process. Induction of micronuclei and chromosomal aberrations in the root meristematic cells even at the post exposure stage indicates persistent genotoxicity of the hair dyes which may be attributed to the interactive effects of chemical mixtures present in the commercial hair dye formulations. The results revealed that A. cepa test system is an effective bioanalytical tool for screening cytogenotoxicity of commercial hair dye formulations.
Assessing neurotoxic potential of titanium dioxide nanoparticles and bulk form using the fish model, Nile tilapia (Oreochromis niloticus)
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Samanthika, A.L.C.; Pathiratne, A.
Titanium dioxide nanoparticles (nano TiO2) and bulk TiO2 are widely used worldwide in various sectors. Hence they can be released inevitably into the inland water bodies posing health threats to the aquatic ecosystems. Cholinesterase (ChE) activity can be used as a biomarker for screening neurotoxicity in organisms exposed to the environmental contaminants. The objective of the present study was to evaluate the neurotoxic potential of environmentally relevant concentrations of nano and bulk TiO2 using Nile tilapia as the tropical fish model. Groups of fish which had been acclimated to the laboratory conditions for two weeks were exposed continuously to relatively low concentrations (50 and 100 μg/L) of nano or bulk TiO2 for 7 or 14 days (n= 7). The control fish were exposed only to aged tap water. The experimental design also included 7 day nano or bulk TiO2 exposure groups which had been transferred to aged tap water for another 7 days to evaluate potential recovery of the toxicity. Neurotoxic potential was assessed using ChE activity measurements in the brain, gill and liver tissues by a standard spectrophotometric method. ChE activities (mean±SEM in nmol/min/mg protein) in gills were elevated significantly(P <0.05) in the fish exposed to 50 and 100 μg/L bulk TiO2 for 7 days (102±9 and 105±7 respectively) compared to those of the control fish (71 ± 5) whereas brain ChE activities were not affected. Liver ChE activities were significantly elevated at 100 μg/L continuous exposure to bulk TiO2 for 7 and 14 days (279±15 and 315±15 nmol/min/mg protein respectively) compared to those of the control fish (155±12) and were not restored to normal levels after 7 days post exposure. A consistent ChE activity stimulation pattern was not evident with respect to bulk and nanoTiO2 exposures. In the fish exposed to both concentrations of nano TiO2, ChE activities in brain and gill tissues were not significantly different from those of the control fish. However ChE activity in liver tissues of the fish exposed to 100 μg/L of nano TiO2 was elevated significantly (P < 0.05) at 7 days exposure and post exposure periods. The results revealed that environmentally relevant concentrations of nano and bulk TiO2 may pose neurotoxic risks to the fish populations inhabiting the contaminated water bodies and the bulk form of TiO2 is not ecotoxicologically inert as previously assumed
Assessing potential biological hazards associated with Kelani River water using Nile tilapia (Oreochromis niloticus) as an aquatic model species
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Ruvinda, K.M.S.; Pathiratne, A.
Kelani River receives complex mixtures of pollutants from diverse sources which include waste from industries, agriculture, domestic and municipal sources. However, scientifically based evidences on biological impacts associated with the Kelani River water are limited. Nile tilapia (Oreochromis niloticus) is a practically feasible aquatic model for toxicological assessments under tropical conditions. The present study assessed erythrocytic nuclear abnormalities (ENA), hepatic ethoxyresorufin O-deethylase (EROD) and hepatic glutathione S-transferase (GSTs) activities of Nile tilapia following exposure to selected surface water samples collected from the Kelani River and its tributaries in order to assess the potential biological impacts. Fingerlings of fish were exposed to surface water samples from an industrial effluent receiving canal (Menikagara ela; Site B), canal confluent (Site M), downstream of Kelani river at Sedawatta (contaminated with oil installation complex effluents and house hold waste; Site S) and up stream of Kelani river at Ruwanwella (reference site; Site R) and aged tap water (as controls) for 10 days under static renewal conditions. Physico-chemical parameters of exposed water were measured using standard analytical methods. Blood and liver samples of the exposed fish were collected from each treatment after 5 and 10 days of exposure, and ENA and EROD and GST tests were performed using standard methods. Water quality parameters indicated high levels of chemical oxygen demand, biochemical oxygen demand, total dissolved solid, salinity and conductivity and elevated levels of total phosphate content, nitrate content, heavy metal Cr, Cu and Pb levels in the water collected from the Sites B, M and S compared to tap water (P <0.05). Frequencies of total ENA were significantly higher in the fish exposed to water from the sites B, M and S compared those of the fish exposed to the tap water for 5 and 10 days. Blebbed and notched nuclei contributed mainly to the induction of total ENA than micronuclei and nuclear buds. Total number of nuclear abnormalities was elevated by the 10th day of exposure. Hepatic EROD and GST activities of the fish exposed to polluted water were not significantly different (P >0.05) from those of the fish exposed to tap water, but the enzyme activities were increased in each treatment at 10th day of exposure. Comparison of nuclear abnormalities and hepatic EROD & GST activities of O. niloticus together with physico-chemical analysis revealed that Sites B, M and S of Kelani River are contaminated with organic and inorganic xenobiotics, which may pose harmful cyto-genotoxic impacts on the feral fish populations.
Assessing Potential Genotoxic Effects of Nano-Titanium Dioxide on Nile Tilapia (Oreochromis Niloticus)
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) de Silva, P.; Pathiratne, A.
Due to widespread use of titanium dioxide nanoparticles (nano-TiO2) in many industrial applications, significant release of nano-TiO2 to the environment can occur which may eventually reach aquatic ecosystems. Hence biological impacts of nano-TiO2 to the aquatic fauna especially fish under chronic exposure need to be explored. Nile tilapia, Oreochromis niloticus is used as a bioindicator for evaluating toxic effects to environmental substances in tropical waters. The aim of the present study was to assess the potential genotoxic effects of water-borne nano-TiO2 on Nile tilapia under chronic exposure conditions. Fish were exposed to a range of nano-TiO2 (<25 nm, anatase) concentrations viz 0.1 mg/L, 0.5 mg/L and 1.0 mg/L along with the controls for 21 days and genotoxic effects were evaluated weekly by micronucleus assay and Comet assay using peripheral erythrocytes. Even though micronuclei induction in the erythrocytes was higher in the fish exposed to the lowest nano-TiO2 concentration (0.1 mg/L) at 7 and 21 days of exposure, a statistically significant concentrationresponse pattern was not observed (P > 0.05). Comet assay revealed that DNA damage in erythrocytes of Nile tilapia could be induced by nano-TiO2 even at 0.1 mg/L level (P < 0.05) by 21 days of exposure. Compared to micronucleus assay, Comet assay was more effective in detecting genotoxic effects on Nile tilapia. The results indicate that nano-TiO2 exposure could lead to genotoxic hazards to the fish populations in the contaminated water bodies.
Assessing toxicity of copper, cadmium and chromium levels relevant to discharge limits of industrial effluents into inland surface waters using common onion, Allium cepa bioassay
(Springer US., 2015) Hemachandra, C.K.; Pathiratne, A.
Toxicity of copper, cadmium and chromium relevant to established tolerance limits for the discharge of industrial effluents into inland surface waters was evaluated by Alliumcepa bioassay. The roots of A. cepa bulbs exposed to Cu2+ (3 mg L−1) individually or in mixtures with Cd2+ (0.1 mg L−1) or/and Cr6+ (0.1 mg L−1) exhibited the highest growth inhibition, mitotic index depression and nuclear abnormalities. Root tip cells exposed to Cr6+ or Cd2+ alone or in mixture displayed significant chromosomal aberrations in comparison to the controls. EC50s for root growth inhibition followed the order Cu2+ < Cd2+ < Cr6+ indicating greater toxicity of copper. The results show that the industrial effluent discharge regulatory limits for these metals need to be reviewed considering potential cyto-genotoxicity to biological systems.
Assessing toxicity of inland surface waters impacted by industrial wastewater released from an export processing zone located near Kelani river basin using physic-chemical analysis and plant based bioassay
(Sri Lanka Association for Fisheries and Aquatic Resources, 2016) Kuruppuarachchi, H.D.; Pathiratne, A.
Assessing toxicity of selected textile industry effluents reaching Kelani River using a plant based bioassay
(Faculty of Graduate Studies, University of Kelaniya, 2015) Hemachandra, C.K.; Pathiratne, A.
Textile industry effluents that are discharged in high volumes into inland waters may contain complex mixtures of toxic substances that could pose health impacts to biota inhabiting receiving waters. Conventional effluent quality assessments such as physico-chemical characterization may not be adequate to evaluate their biological effects. In the present study, potential toxicity of selected textile industry effluents discharged into Kelani River were assessed by a plant based bioassay using Allium cepa (onion) as the test organism. Effluents were collected from the discharging points of two textile industries in three sampling occasions covering mostly dry periods. Onion bulbs were exposed to the effluents under undiluted and diluted (1:8) conditions using aged tap water as the dilution media. Toxicity endpoints were root growth, mitotic index, occurrence of chromosomal aberrations and nuclear abnormalities. A. cepa root tip cells exposed to undiluted effluents from both industries caused significant (p<0.05) root growth inhibition, mitotic depression compared to that of the controls along with a significant (p<0.05) induction in the occurrence of condensed nuclei at each sampling occasion indicating cytotoxic effects. Moreover, undiluted effluents significantly (p<0.05) induced chromosomal abnormalities with further induction in micronuclei in the root tip cells indicating genotoxicity. Exposure of onion bulbs to the 1:8 diluted effluents also showed significant alterations of toxicity end points depending on the effluent type and sampling occasion. The results revealed that 1:8 dilution was not adequate to eliminate the cytotoxicity/genotoxicity induced by the effluents completely. Physicochemical characterization of the effluents showed that heavy metal levels generally comply with the national tolerance limits for effluent discharge into surface waters. However, color measurements and chemical oxygen demand levels did not comply with the tolerance limits in most of the cases indicating that highly oxidizable organics including textile dyes might have contributed to the observed toxicity. Present study showed the necessity of incorporating bioassays into effluent monitoring programs for more realistic effluent quality assessments, considering ecosystem and public health. This study was funded by the National Research Council research grant 11-11 and National Science Foundation equipment grant RG/2011/EQ/16.
Assessing toxicity of two industrial zone effluents reaching Kelani River,Sri Lanka
(Journal of national science foundation Sri Lanka, 2018) Hemachandral, C.K.; Pathiratne, A.
Evaluation of the effcaey of waste treatment technologies of industnal waste is a major challenge for sustainable industrial development world-wide. Hence, new strategies are needed to assess interactive toxic effects of all substances present in the treated waste. This study assessed potential toxic hazards of treated effluents discharged from common wastewater treatment plants of two mclustrlal zones located in the Kelani River basin using Allium cepa (common onion) test system. The results showed that the final effluents of both industrial zones under undiluted and diluted (1 IS v/v) conditions mduced cytotoxrcity on all occasions, with evidence of significant (p < 0.05) mlto-depression In the root meristem and retardation of root growth in A. cepa. Genotoxlc hazard of the effuents was evident by frequent mcrease of nuclear and chromosomal abnormalltles, and occasional development of micronuclei in the root merlstem. Dilution of the effluents to 1 reduced the genotoxic effects generated in A. cepa roots by the final effuents_ The results revealed that waste treatment technologies m these two mdustnal zones need to be upgraded m order to ehmmate cytotoxlc and genotoxrc hazards associated with the treated effuents_ The results highlight the importance of incorporatmg practically feasible bioanalytical tools such as A. cepa root based test system on a regular basis for evaluating the efficacy of waste treatment technologies.
Assessment of Bile Fluorescence Patterns in a Tropical Fish, Nile tilapia (Oreochromisniloticus) exposed to Naphthalene, Phenanthrene, Pyrene and Chrysene using Fixed Wavelength Fluorescence and Synchronous Fluorescence Spectrometry
(Bulletin of Environmental Contamination and Toxicology, 2010) Pathiratne, A.; Hemachandra, C.K.; Pathiratne, K.A.S.
Bile fluorescence patterns in Nile tilapia, a potential fish for biomonitoring tropical water pollution were assessed following exposure to selected polycyclic aromatic hydrocarbons (PAHs): naphthalene, phenanthrene, pyrene and chrysene. Non-normalized fixed wavelength fluorescence signals in the fish exposed to these PAHs reflected dose and/or time response relationships of their metabolism. Normalizing signals to biliverdin introduced deviations to these response patterns. The optimal wavelength pairs (excitation/emission) for synchronous fluorescence scanning measurements of bile metabolites of naphthalene, phenanthrene, pyrene and chrysene were identified as 284/326, 252/357, 340/382 and 273/382 respectively. This study supports the use of bile fluorescence in Nile tilapia by fixed wavelength fluorescence and synchronous fluorescence spectrometry with non-normalized data as a simple method for screening bioavailability of these PAHs.
Assessment of Bio Available Polycyclic Aromatic Hydrocarbons and Induction of Erythrocytic Nuclear Abnormalities Associated with Petroleum Refinery Wastewater Exposure Using Fish Models
(Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Rukmalee, W.N.; Pathiratne, A.
Petroleum refinery wastewater may contain different chemicals including polycyclic aromatic hydrocarbons (PAHs) some of which are genotoxie. Release of the refinery wastewater to the aquatic environments may pose a threat to the aquatic fauna especially fish populations. Biological effects associated with wastewater can be assessed using biomarkers as early warning signals. The objective of the present study was to assess biological effects associated with wastewaters of Petroleum Refinery, Sri Lanka using a selected PAH indicative biomarker (bile fluorescent PAH metabolite patterns) and a genotoxic biomarker (erythrocytic micronuclei in the blood) using fish models. The fish species used in the study were Oreochromis niloticus for controlled laboratory exposure and Trichogaster pectoralis and Puntius filamentosus, inhabiting water canals located near the Petroleum refinery (Pattiwila canal and Heiyanthuduwa canal) for exposure assessments under natural conditions. A less polluted water body was selected as the control site for field studies (Bathalagoda reservoir). Bile fluorescence patterns of the fish were assessed using fixed fluorescence and synchronous fluorescence spectrometry. Erythrocytic nuclear abnormalities in the blood (micronuclei, binuclei and other nuclear abnormalities) were examined using cytogenetic tests. The results showed that several PAHs metabolites (Napthalene-, Phenanthrene-, Fluoranthene-, Chrysene- and Benzo(a)pyrenetype) accumulate in bile of 0. niloticus as a result of being exposed to the Petroleum refinery wastewater under laboratory conditions. Bile of T. pectoralis and P. fjlamentosus collected from the nearby canals also displayed PAH exposure in comparison to the fish collected from the control site. Erythrocytic micronuclei in the blood were highly induced in the fish species examined under laboratory (upto 20 fold) and field conditions (upto 26 folds) in comparison to the comparable controls. The present study revealed that tested petroleum refinery wastewater contains micronuclei inducible contaminants including PAHs.
Assessment of biological effects of pollutants in a hyper eutrophic tropical water body, lake Beira, Sri Lanka using multiple biomarker responses of resident fish, Nile tilapia
(Ecotoxicology, 2010) Pathiratne, A.; Pathiratne, K.A.S.; de Seram, P.K.C.
Biomarkers measured at the molecular and cellular level in fish have been proposed as sensitive ?early warning? tools for biological effect measurements in environmental quality assessments. Lake Beira is a hypertrophic urban water body with a complex mixture of pollutants including polycyclic aromatic hydrocarbons (PAHs) and Microcystins. In this study, a suite of biomarker responses viz. biliary fluorescent aromatic compounds (FACs), hepatic ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST), brain and muscle cholinesterases (ChE), serum sorbitol dehydrogenase (SDH), and liver histology of Oreochromis niloticus, the dominant fish inhabiting this tropical Lake were evaluated to assess the pollution exposure and biological effects. Some fish sampled in the dry periods demonstrated prominent structural abnormalities in the liver and concomitant increase in serum SDH and reduction in hepatic GST activities in comparison to the control fish and the fish sampled in the rainy periods. The resident fish with apparently normal liver demonstrated induction of hepatic EROD and GST activities and increase in biliary FACs irrespective of the sampling period indicating bioavailability of PAHs. Muscle ChE activities of the resident fish were depressed significantly indicating exposure to anticholinesterase substances. The results revealed that fish populations residing in this Lake is under threat due to the pollution stress. Hepatic abnormalities in the fish may be mainly associated with the pollution stress due to recurrent exposure to PAHs and toxigenic Microcystis blooms in the Lake.