Browsing by Author "Silva, T.M.S.D.G."

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Assessment of invasion of Najas marina, Linnaeus 1753 in Madu Ganga estuary, Sri Lanka using ASTER data of Terra satellite
(Institute of Biology, Sri Lanka, 2015) Silva, T.M.S.D.G.; Dahanayaka, D.D.G.L.; Wijeyaratne, M.J.S.
Factors affecting the invasion of Najas marina, Linnaeus 1753 (Family Najadaceae) in the Ramsar Wetland of Madu Ganga Estuary, Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2015) Silva, T.M.S.D.G.; Wijeyaratne, M.J.S.
Najas marina is one of the nine invasive alien floral species that have been identified in the Ramsar wetland of Madu Ganga Estuary. This aquatic macrophyte is considered as a huge threat to the existing ecological balance of this ecosystem and also it is a nuisance to the tourism industry operated within the estuary. Present study was conducted from March to November 2014 to identify the physicochemical parameters that are important for the spatial and temporal distribution of Najas marina in this estuary. Five sampling sites where Najas marina was present and another five sampling sites where it was absent were selected to cover the entire estuary. The ranges of the physicochemical parameters during the study period were depth: 0.60 - 5.84 m; Secchi disc depth: 0.47 - 1.48 m; temperature: 27.05 - 34.92 ˚C; salinity: 0.86 - 21.57 ppt; pH: 5.04 - 8.80; Dissolved Oxygen (DO): 4.60 - 9.62 mg/L; Biological Oxygen Demand (BOD5): 0.25 - 2.89 mg/L; nitrate-N: 0.01 - 0.87 mg/L; total dissolved phosphorous: 0.03 - 0.26mg/L and total phosphorous concentration: 0.04 - 0.46mg/L. The distribution of N. marina in Madu Ganga Estuary was found to be determined by a combination of physicochemical parameters including depth, Secchi disc depth, DO, salinity, nitrate-N concentration and total phosphorous concentration. N. marina entirely disappeared from the estuary by May 2014 with decreasing salinity (8.55ppt) and again started to emerge by September 2014 at a bay region where water was stagnated. It was present in shallow sites with high nitrate and total phosphorous concentrations and low DO levels. The study showed that the entire estuary is under the threat of invasion by N. marina because when all physicochemical parameters were considered, the 10 sites were more or less similar to each other at 94.5% level. Although the invasion of N. marina is highly temporal and naturally controlled, the further spread of this species could be controlled by mechanical removal.
Management of coastal resources: Lessons learnt from two coastal communities occupying the west coast of Sri Lanka
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Kodituwakku, K.A.R.K.; Wazir, S.R.; Aththanayake, A.M.H.L.; Silva, T.M.S.D.G.; Malshani, E.M.S.; Partheepan, K.; Thevendran, K.; Udayanga, N.W.B.A.L.; Sumanapala, A.P.; Jayanga, B.H.N.; Chandrasekara, W.U.
The livelihood of the coastal communities is mostly dependent upon the natural coastal resources. Questionnaire based field surveys were carried out focusing on the communities in two coastal towns on the west coast of Sri Lanka, Negombo and Chilaw, with an objective of evaluating and assessing the governance and the sustainable utilization and management of coastal resources there. The survey was carried out in December 2013, and consisted of face-to-face interviews and gathering information from households along the beach border that were selected through systematic sampling approach and from randomly selected stake holders on the beach, to satisfy the questionnaire. The chief executive officers of local government authorities viz. regional office of the Coast Conservation and Coastal Resources Management Department, Municipal Councils, Police Stations, and where necessary the incumbent of the Catholic Church in the area, were also interviewed to evaluate their role over the governance and management of the coastal resources. The analysis of survey data revealed that the major resource based income generation activities in Negombo beach was tourism (68%) while in Chilaw it was fisheries (75%). The major environmental issues in Negombo beach were pollution (35%), littering the beach by local tourists (27%) and illegal building constructions (20%), while those in Chilaw were pollution (43%), illegal house constructions (25%) and coastal erosion (26%). Therefore, the Negombo beach was cleaner (76%) than the Chilaw beach (27%). Since the major income generation activity in Negombo beach was tourism, the local government authorities paid special attention in maintaining law and order, carrying out beach cleaning programmes, daily removal of litter and waste, carrying out community awareness programmes on the importance of beach on tourism and usage of soft and hard engineering techniques to prevent coastal erosion. In addition, every tourist hotel was found to clean the beach façades under their purview, and beach vendors also supported these programmes. In fisheries dominated Chilaw, the inputs by the local government authorities were minimum except the Urban Council collecting household waste on weekly basis from the roadside bins. However, the village has a very strong community based management strategy led by the Catholic Church. The church plays a pivotal role in harmonizing the village, educating villagers on the proper disposal of garbage, preventing sand mining and use of harmful fishing practices, and coordinating the local government authorities to maintain proper sanitation as well as law, order and peace in the area. In contrast, the tourism dominated coastal zone in Negombo is managed by a strong co-management strategy that involves the contribution of the local government authorities and major stakeholders on the beach such as tourist hotels and the local community on the governess and sustainable management of the coastal zone.
Trophic condition of Madu Ganga Estuary, a Ramsar Wetland in Sri Lanka
(2017) Silva, T.M.S.D.G.; Wijeyaratne, M.J.S.
Madu Ganga Estuary, which extends for 915 ha is a Ramsar wetland in the south- western coastal region of Sri Lanka. This slow flowing water body is rich in biodiversity with 248 vertebrate species which include 20 endemics and 303 plant species. About 10% of the 111 species of birds are winter migrants. Cinnamon and paddy cultivations form the dominant land use type in the surrounding area and at present, a nature based tourism industry is also developing rapidly at the estuary due to its ecological and aesthetic significance. In addition, resident traditional fishermen are involved in commercial fishing activities using traditional gear such as Kraals. The present study aimed to figure out the trophic condition of this important wetland. During the study period from March to November 2014, the mean values for physicochemical parameters were found to be as follows; Depth: 1.89 m; Secchi Depth (SD): 0.91 m; Temperature: 30.8 ˚C; Total Dissolved Solids (TDS): 8.8 g/L; Salinity: 8.29 g/L; pH: 7.2; Dissolved Oxygen (DO): 6.79 mg/L; Biological Oxygen Demand (BOD 5 ): 1.40 mg/L; Nitrate-N: 0.2 mg/L; Total dissolved phosphorous: 0.09 mg/L and Total Phosphorous (TP): 0.17 mg/L. The TP values suggest that the trophic condition of this highly ecologically and economically important wetland is eutrophic. Excess and indiscriminate use of fertilizer in the watershed area and soil erosion appear to be the major reasons for this condition, which may be controlled by educating farmers on repercussions of applying excess amounts of fertilizer and ensuring that only the recommended levels are applied. Remote Sensing methods can also be used in nearby agricultural fields to detect the areas where deficiency symptoms are present and fertilizer can be applied only to those regions. In addition, erosion control methods can also be applied to retain the fertilizer within the agricultural fields without being washed into the estuary with storm water.