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Item Effects of biological and technical factors on brain and muscle cholinesterases in Nile tilapia, Oreochromis niloticus: implications for biomonitoring neurotoxic contaminations(Springer-Verlag., 2008) Pathiratne, A.; Chandrasekera, L.W.H.U.; De Seram, P.K.C.Influence of body length, body weight, gender, sexual maturity, and tissue storage on brain and muscle cholinesterases (ChE) in Nile tilapia was evaluated considering its potential use in biomonitoring neurotoxic contaminations in tropical environments. Results show that ChE activities in both tissues decreased significantly with increased total length (4–24.5 cm) or body weight (1–186 g) of the fish and the relationships were curvilinear. Comparisons of the slopes and elevations of the regression lines of the logarithmic ChE and body size relationships of males with those of females indicated that gender had no significant effect on the body size-specific ChE activities. Response of the ChE of sexually mature males to chlorpyrifos exposure was similar to that of females. Gonadal maturity stage of this fish does not seem to influence ChE activities. Storage of tissues at –80°C for 28 days had no significant effect on ChE activities in the control fish and the fish exposed to carbofuran. However, a partial reactivation of brain ChE activities was observed in the fish exposed to carbosulfan after 28 days of storage. The results emphasize the importance of consideration of body size of the fish and storage time of the tissues in order to formulate accurate conclusions about the neurotoxic chemical exposure when ChE of the fish is used in biomonitoring programs.Item A preliminary study on the invasion of plankton into the west coast off Sri Lanka through ballast water(Sri Lanka Association for Fisheries and Aquatic Resources, 2009) Chandrasekera, L.W.H.U.; Fernando, M.A.S.T.Item Effects of Pyrene exposure on Xenobiotic metabolizing enzymes in Nile Tilapia, Oreochromis niloticus(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Chandrasekera, L.W.H.U.; Pathiratne, A.Item Effect of crowding, food quality and body size on food utilization of the exotic snail, Pomacea canaliculata (Lamarck), a potential pest of rice in Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 1999) Kumara, P.A.D.A.; Chandrasekera, L.W.H.U.; Costa, H.H.Item The spatial variation of macrobenthic community in the Negombo estuary in relation to physic-chemical parameters(Sri Lanka Association for Fisheries and Aquatic Resources, 2011) Chandrasekera, L.W.H.U.; Hettiarachchi, A.I.Item Accidental introduction of alien plankton into the Sri Lankan coastal zone through ballast water of cargo ships(Sri Lanka Association for Fisheries and Aquatic Resources, 2009) Chandrasekera, L.W.H.U.; Fernando, M.A.S.T.Accidental introduction of alien plankton through ballast water is a major ecological issue in many countries in the world. As there are no local studies addressing this problem, the present study was carried out to see whether alien plankton are introduced into Sri Lankan coastal zone through ballast water. Marine plankton occurring within ballast water holds of five cargo ships arrived at Colombo harbour and three local sites including Colombo inner harbour and two neighboring coastal sites were sampled. The physico-chemical parameters of water samples were also measured. Data on species abundance and physico-chemical parameters were analyzed using multivariate and univariate statistical tests as appropriate. Altogether 159 taxa of plankton were found in the samples. In the ballast water samples alone, there were 56 different taxa of which 50% of them were totally alien to the local coastal zone. The physico-chemical parameters of water samples between the four sites were not significantly different. However, multivariate statistical tests confirmed that the plankton community of the ballast water samples was significantly different from that of the three local sites. Considering the large number of ships calling annually at Colombo harbour, the great potential of accidental introduction of alien plankton into the Sri Lankan coastal zone should never be underestimated.Item Abundance and diversity of freshwater molluscs in some selected reservoirs of the Kala Oya river basin, Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2015) Weerakoon, S.N.; Chandrasekera, L.W.H.U.; Amarasinghe, U.S.Benthic macroinvertebrates such as molluscs are known to be possible bioindicators of aquatic ecosystems. We carried out a study to investigate how the abiotic factors affect the abundance and diversity of molluscan fauna at 10 irrigation reservoirs in the Kala Oya river basin during the dry season from August to November 2014. In each reservoir, three sampling sites were selected where at each site, a 50 m long perpendicular line transect was established running from its maximum water supply level towards the center of the reservoir. Three soil samples were collected at 10 m intervals each along each transect using a 0.5 dm3 soil corer. These samples were sieved in situ through a 1 mm sieve and the remains were preserved in 10% formalin solution containing Rose Bengal. Later the molluscs and other associated macrofauna were identified to the nearest possible taxonomic category using standard taxonomic keys and the fauna belonging to each taxon were enumerated separately. In addition, data related to vegetation cover, intensity of human disturbances, intensity of pollution, agrochemical inputs, soil texture and human settlements based on a modified scoring system were also collected. Altogether 4328 molluscs belonging to 11 genera were recorded. Molluscan genera such as Bellamya (45.9%), Melanoides (26.7 %) and Thiara (16.9 %) dominated the samples while the remainder (10.5%) belonged to less dominant genera consisting of Planorbis, Gyraulus, Indoplanorbis, Lamellidans, Planorbella, Lymnaea and Pila. The abundance of the molluscan genera varied significantly between the reservoirs (MANOVA; F (99, 899) = 4.300, P = 0.000; Wilk’s λ = 0.06515) and along the transect distances (MANOVA; F (44, 483) = 0.901, P = 0.654; Wilk’s λ = 0.73988). High diversity measures of molluscs were observed at Angamuwa wewa, Katiyawa wewa, Rajanganaya reservoir and Usgala-siyambalangamuwa wewa. Principal Component Analysis (PCA) for the mollusc abundance and the relationship between PC1 scores and Shannon–Wiener diversity index endorsed that Bellamya, Melanoides and Thiara were the highly contributing genera to the high diversity of the molluscs in the above reservoirs. Results of the PCA for abiotic factors revealed that both the abundance and species diversities were high at moderately sandy bottoms with high vegetation cover and agrochemical inputs. In contrast, the intensity of human disturbances, pollution, human settlement and shadiness showed a negative effect on the abundance and diversity of these molluscs. This study was carried out as part of a comprehensive study which investigates how the aspects related to biotic integrity and multiple uses of reservoirs could be used to develop effective management options for reservoir fisheries in Sri Lanka.Item Biological factors affecting brain and muscle acetylcholinesterases in Oreochromis niloticus (Nile tilapia): Implications in biological monitoring of aquatic pollution(Sri Lanka Association for the Advancement of Science, 2005) Chandrasekera, L.W.H.U.; Pathiratne, A.Item 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 monitoringItem Role of the gastropod Terebralia palustris (Linnaeus, 1767) in Rhizophora apiculata leaf litter decomposition(Sri Lanka Association for Fisheries and Aquatic Resources, 2004) Ponweera, N.I.; Chandrasekera, L.W.H.U.Macro-invertebrates play an important role in the breakdown of leaf litter in the mangrove ecosystems. Among them, the gastropod Terebralia palustris L., is considered to be an important species that significantly contribute to this process. The role of T. palustris on the leaf litter breakdown of Rhizophora apiculata, one of the commonest mangrove species in Sri Lanka, is assessed by a laboratory experiment where the loss of dry weights of R. apiculata leaf litter, increase of particulate organic matter and changes of the total reactive phosphate concentration in water at varying densities of T. palustris were measured at varying period of exposure. The distribution juvenile and adult T. palustris along the margin of the estuary from where the specimens were collected was also investigated in-situ using the belt transect method. Results showed that the loss of dry weight of leaves decreased significantly as a result of shredding by T. palustis. The total suspended particles were increased significantly with the period of exposure and the density of T. palustris. The total reactive phosphate concentration in water increased with the period of exposure, but this was not related to the density of T. palustris. The adult T. palustris were more abundant near the mangrove root system, while the juveniles were abundant in the open areas of the estuary. This study showed that T. palustris helps shredding large leaves into small litter particles and contributes immensely to the decomposition mangrove leaf litter. However, this process did not enhance the mineralization of phosphorus as the fragmented litter particles were not in critical size and the leaves were not exposed to an adequate period of time for leacheate loss.