Browsing by Author "Chandrasekera, W.U."

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Impacts of rubber factory effluents on the macrobenthic community in Gurugoda Oya, Ruwanwella
(Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Ranathunge, R.M.T.B.; Chandrasekera, W.U.
Rubber factory effluents contain a mixture of chemical compounds that bring about harmful impacts to fauna. With this view, the present study was carried out to investigate the changes in water and sediment quality parameters in a freshwater stream, and how the associated macrobenthic community responds upon receiving untreated effluents from a nearby raw rubber processing factory. This study was carried out in the Atala village section of the Gurugoda Oya, a shallow tributary of river Kelani in the Ruwanwella region. Three downstream sampling sites that are 50 m apart from each other from the point of discharge, a pristine control site that is SO m upstream from the point of discharge, and a sampling site within the effluent feeder canal were established for the study. The water flow velocity, temperature, conductivity, pH, DO, BOO" COD, total suspended solids, total dissolved solids, total sulphides, alkalinity and the concentration of Nao, KO, Ca'o, and Mg'O ions in the overlying water and organic matter content in the sediment and the abundance of the associated macrobenthic invertebrate faunas were measured in sufficient replication in each site twice during the dry season and twice during the wet season of the year 2010. The seasonal and site-wise variation of the physico-chemical parameters, abundance of major macrobenthic species and their community structure were analysed. Although the results revealed that the physico-chemical characteristics of water and sediment drastically altered upon receiving the effluents, they regained their ambient levels down in the stream most probably as a result of dilution in the water flow. The macrobenthic faunas in the stream too, responded accordingly where their species richness and diversity significantly (p
Spatial distribution of macrobenthos in the Negombo estuary: Is it governed by the physico-chemical characteristics of water and sediment or by the sea grass cover?
(Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Chathurangi, N.G.M.; Chandrasekera, W.U.
The present study was carried out to investigate whether the spatial variation of the macrobenthic community in Negombo estuary is governed by the physico-chemical parameters in the overlying water and sediment or by the density of seagrass cover. In this study, six study sites representing the mouth, body and the head of the estuary was selected and the physico-chemical parameters of the overlying water, i.e, salinity, pH, temperature, conductivity, DO and BOO, and the sediment salinity, temperature, pH, % of sand, silt. and clay and OMC were measured using standard methods. Further, the macrobenthic fauna and the flora inhabiting in each sample site were also sampled. The physico-chemical data and the abundance data between the six study sites were analysed using appropriate univariate and multivariate statistical tests. Results revealed that the physico-chemical parameters of the overlying water and sediment varied significantly between the six sites with an increasing trend of salinity, and sand % and decreasing trend of OMC and silt % towards the mouth of the estuary. The macrobenthos were abundantly found in the sites where the bottom is devoid of seagrasses. Further, the macrobenthic community structure in the Negombo estuary appeared to be correlated with these physicochemical parameters, but not with the density of seagrass cover. It is evident that the spatial distribution of macrobenthos in the Negombo estuary is governed by the physico-chemical parameters in the sediment and the overlying water but not by the density of seagrass cover.
Toxic effects of Trebon, a synthetic pyrethroid based insecticide formulation, on Oreochromis mossambicus (Family: Cichlidae)
(Sri Lanka Association for Fisheries and Aquatic Resources, 2016) Chandrasekera, W.U.; Premaratna, K.D.S.
Toxic Effects of Trebon, a Synthetic Pyrethroid on the Fingerlings of Tilapia Oreochromis mossambicus (Peters, 1852)
(Sri Lanka Association for Fisheries and Aquatic Resources, 2013) Premaratna, K.D.S.; Chandrasekera, W.U.
Trebon' (Generic name: Etofenprox) is a recently developed potential pyrethroid insecticide, and reported to bring about adverse effects to non-targeted organisms in agricultural fields and associated habitats. In the present investigation, toxic effects of Trebon' on the fingerlings of tilapia (Oreochromis mossambicuSi were studied under laboratory conditions following standard experimentation and analytical techniques. Results revealed that the 24-hr and 96-hr LCso of Trebon' were in low concentration Le. 0.0657 ml L-' and 0.0087 ml L-' respectively, which is well below its recommended field concentration of 1.5 ml L". As such Trebon' causes tilapia fingerlings mortality at 23 times and 172 times milder concentrations than the recommended field concentrations at 24-hr and 96-hr exposure periods. Gill hyperplasia, deformation and telangiectasis of secondary gill lamella, mucosal cell proliferation, lamella disorganization and fusion were observed in the test fishes. The liver tissues were also damaged with intracellular vacuolation, aggregation of melanomacrophages, blood congestion, and focal necrosis. The severity of these damages increased with the level of dosage and exposure period. The fingerlings suffered respiratory distress while the body colouration gradually changed into a pale hue upon exposure to Trebon*.