Zoology
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Item Diversity in the Diyawannawa wetland(Department of Zoology and Environmental Management,Faculty of Science, University of Kelaniya Srilanka, 2021) Nanayakkara, D.B.M.; Wijeyaratne, W.M.D.N.Item Monitoring of water quality variation trends in a tropical urban wetland system located within a Ramsar wetland city: A GIS and phytoplankton based assessment(Environmental Nanotechnology, Monitoring & Management, 2020) Wijeyaratne, W.M.D.N.; Nanayakkara, D.The present study, was conducted in an urban wetland system within a Ramsar wetland city in Sri Lanka to study the effectiveness of using the Geostatitical and multivariate statistical techniques together with phytoplankton based biological indices to assess the wetland ecological status. Seven sites were selected from the wetland and the water quality parameters and the diversity and abundance of phytoplankton at each site was assessed. Thirteen species of phytoplankton from Class Cyanophyceae, 18 species from Class Chlorophyceae and six species from class Bacillorphyceae were recorded during the study. There were significant spatial variation of water quality parameters and phytoplankton composition among the study sites. Principal component analysis for water quality and phytoplankton distribution was performed. Palmers index, percentage biological index and the limnological condition index was calculated based on water quality and phytoplankton data. According to the classification based on Palmers index the sites located in the northern portion ofthe wetland indicated high organic pollution, while otier sites indicated no or less less organic pollution. According to the limnological categorization based on pollution index, %BI and LICOI, the northern sites were categorized as sites with poor ecological quality and as severely contaminated sites. The sites in the southern portion of the wetland were categorized as moderately polluted sites with acceptable limnological conditions for the ecologicaI functions to occur within tolerable limits. Water quality prediction maps for the wetland was developed using geostatistical methods and the water quality trends also agreed with the results of the biological indices and the results of the multivariate statistics. The results indicated that the geostatisical and multivariate techniques together with the Palmers index, percentage biological index and the limnological condition index can serve as important tools for monitoring the water quality trends in tropical urban wetland ecosystems.Item 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.Item Application of pollution indices to quantify the pollution status of shallow sediments of the Bolgoda Lake, Sri Lanka(National Science Foundation of Sri Lanka, 2016) Wijeyaratne, W.M.D.N.The present study was conducted to assess the pollution status of the shallow sediments of the Bolgoda Lake in Sri Lanka using sediment pollution indices. Shallow sediment samples were collected as replicates from five sites with different land uses in the monsoonal and nonmonsoonal seasons in 2013. The samples were acid digested and analysed for Cd, Cr, Cu, Ni, Fe and Zn. The heavy metal concentrations were used to calculate: (1) contamination factor (Ci f ); (2) degree of contamination (Cd); (3) pollution loading index (PLI); (4) enrichment ratio (ER); (5) geoaccumulation index (Igeo) and (6) ecological risk factor (Eri ) of the shallow sediment samples. In addition, the quality of the sediments were also assessed by comparing with the numerical sediment quality guidelines (SQGs) and consensus-based sediment quality guidelines (CBSQGs). Significant spatial variations of element concentrations and sediment quality indices were identified in the study area. The pollution level of the study sites ranged from unpolluted to heavily polluted due to heavy metals. The contamination factors for all the heavy metals except Zn indicated moderate, considerable or very high level of pollution in both sampling sessions. The potential ecological risk factor for the heavy metals ranked as Cd > Ni > Cr > Cu > Zn for both sampling sessions indicating the highest potential ecological risk from Cd. The pollution load index for all the study sites except site E in both sampling sessions showed human associated pollution with a PLI higher than 1. All the samples were categorised into class 1 (unpolluted to moderately polluted status) with respect to Cr, Ni, Cu and Zn and to class 0 (unpolluted status) with respect to Cd. The concentrations of Zn and Cd in the present study were lower than the threshold effect concentration (TEC) level of CBSQGs and therefore, was indicated as unlikely to be causing toxicity to benthic organisms. The concentrations of Cr and Ni were higher than the probable effect concentration (PEC) level of CBSQGs and indicated a probable toxicity to benthic organisms.Item Spatial variation of microbenthic community in relation to water and sediment quality parameters in the Ja-Ela canal, Sri Lanka(The Institute of Biology, Sri Lanka, 2016) Kalaotuwawe, K.M.B.P.P.; Wijeyaratne, W.M.D.N.Item In vitro study on bio removal of cadmium (CD2+) by freshwater cyanobacterium Oscillatoria sp. And its isotherm(Department of Forestry and Environment Science, University of Sri Jayewardenepura, Sri Lanka., 2016) Wijesekara, W.A.M.A.; Wijeyaratne, W.M.D.N.; Manage, P.M.Item Gill leisions in Rasbora caverii (Class: Pisces, Family: Cyprinidae) inhabiting paddy field associated water bodies in Kaduwela area, Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Wijeyaratne, W.M.D.N.; Pathiratne, A.Item Evaluation of the effects of three commonly used pesticides on brain Acetyl cholinesterase activity of Rasbora caverii, a feral fish found in paddy field associated water bodies in Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Wijeyaratne, W.M.D.N.; Pathiratne, A.Item Spatiotemporal variation of benthic macroinvertebrates with respect to physicochemical characteristics of shallow sediments in Borala Wewa, Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2015) Jayanga, B.H.N.; Wijeyaratne, W.M.D.N.Benthic macroinvertebrates play a key role in freshwater ecosystems. Survival, distribution and abundance of benthic macroinvertebrates depend on the physicochemical characteristics of their environment. Responses of benthic macroinvertebrate communities to environmental changes are useful in assessing the impacts of different land uses and the impacts of addition of different types of pollutants to surface waters. This study assessed spatial and temporal variations in sediment quality and macroinvertebrate diversity at selected sites of Borala Wewa in Weligama. In ten selected sites in Borala Wewa, organic matter content, pH, percentage contents of sand, silt and clay in shallow sediments were measured. In addition, sediment samples were preserved using 5% Rose - Bengal solution and the diversity of the benthic macroinvertebates were assessed using Shannon Wiener diversity index and species richness values. Spatial and temporal variations of sediment quality parameters were compared using ANOVA followed by Tukey’s pairwise comparison. The correlation between sediment quality parameters and benthic macroinvertebrates species richness were assessed using Pearson’s correlation analysis. Altogether 14 benthic macroinvertebrate species belonging to 11 families were recorded during this study. Among them were 7 species of gastropods belonging to 5 families, 6 species of annelids belonging to 4 families and two larval forms of family Chironomidae and family Ceratopogonidae belonging to Phylum Arthropoda were identified. Site 6, which was a cattle bathing site, was characterized by presence of pollutant tolerant macroinvertebrates such as Faunus sp., Bithynia sp. and Chironomus sp. Sediment pH, organic matter content and percentage sand content showed significant spatial variations but did not show significant temporal variations. However, significant spatial and temporal variations of the percentage clay and silt contents were identified. A significant correlation found only between sediment pH and the species richness of the benthic macroinvertebrates. Further long-term studies with more frequent sampling and increased number of replicates are needed to identify the trends of spatial and temporal variation of sediment quality characteristics and to identify pollution indicator species in shallow sediments of the Borala Wewa.Item 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.