Botany
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Item Annual fluctuations in populations of sea urchin Stomopneustes variolaris (Lamarck. 1816) in two rocky shores of southern Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2012) Thilakarathna, R.M.G.N.; Jayakody, S.; Amarasinghe, M.D.Sea urchins play a key role in rocky shore habitats as grazers. They form urchin fronts and extensively graze on macro algae resulting in regions of barrens and restructuring the habitat. The population status of Stomopneustes var/alaris (Lamarck, 1816) of Phylum: Echinodermata Class: Echinoidea, the most abundant sea urchin species in intertidal zones of Sri Lanka was investigated from June 2008 to May 2009. The study evaluated the density of S. varialaris and the influences of macro algae cover in two rocky shore areas from Hikkaduwa (legally protected) and Ahangama (legally unprotected) in Southern Province. Three habitats (near shore, intermediate and splash) were selected in each site. Line transect and quadrate (50X50cm) sampling methods were used to measure macroalgae cover whilst S. variolaris density of each habitat was measured using belt transect method (10m X O.5m) every month. Mean percentage occurrence of algae and density of S. variolaris were analyzed using multivariate techniques and general linear models. Accordingly, Canonical Variate Analysis of flora confirmed the distinctiveness of the three habitats in relation to floral cover mainly due to differences in the dispersion of Hypnea pannasa and Graciaria sp. sp. in Hikkaduwa and due to Padina sp., Ulva lactuca and Jania ungulata in Ahangama. Ninety nine percent of the variation was explained by axes 1 and 2 in both Hikkaduwa and Ahangama. Mean densities of S. variolaris recorded for Hikkaduwa and Ahangama were 1.65:t0.46 m.l and 0.71 :t 0.22 m'l respectively and Hikkaduwa had a higher density compared to Ahangama (p< 0.05). In Hikkaduwa the highest mean density (3.56 :t 1.48 m'l) was recorded in splash zone (p < 0.05), whilst in Ahangama the highest mean density (1.42:t 0.53 m'l) was recorded in near shore habitat (p< 0.05). A non significant peak density was observed in the months of April and July in Hikkaduwa, and October in Ahangama. Results indicated S. variolaris inhabiting in higher numbers towards the sea in Hikkaduwa but in Ahangama near to coast, perhaps a response to greater disturbance in Hikkaduwa due to visitors.Item Bioconcentraton of metals in edible aquatic plants from a Sri Lankan freshwater wetland(Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Amarasinghe, M.D.; Nirbadha, K.G.S.; Liyanage, J.A.Item Can Avicennia marina produce substitutes for pneumatophores?(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Ambagahaduwa, I.M.; Amarasinghe, M.D.Item Carbon retention capacity of two mangrove species, Bruguiera gymnorrhiza (L.) Lamk. and Lumnitzera racemosa Willd. in Negombo estuary, Sri Lanka(Faculty of Graduate Studies, University of Kelaniya, 2012) Perera, K.A.R.S.; Sumanadasa, W.A.; Amarasinghe, M.D.Carbon accumulation/sequestration by plants is a major function that contributes to removal of carbon dioxide from the atmosphere and capacity to perform it depends on the plant species and environmental conditions under which they live. Carbon retention by natural ecosystems such as mangroves therefore‚ is considered a crucial ecological service‚ and valued highly under the current global context of continued increase in greenhouse gas emission and associated climate change, on which marginal effort has hitherto been spared over its quantification. The Present study was conducted to characterize two true Sri Lankan mangrove species, i.e. Bruguiera gymnorrhiza (L.) and Lumnitzera racemosa Willd.,. with respect to their carbon retention capacity, and to develop allometric relationships between biomass of plant components and stem diameter at breast height (dbh) of the two species with a view to assisting quantification of carbon-sink function of mangrove ecosystems. Fourteen trees of B. gymnorrhiza, and ten trees of L. racemosa that represented the range of dbh distribution in the mangrove area at Kadolkele in Negombo estuary were selected, harvested and dry weights (biomass) were obtained of the components based on wet:dry weight. Organic carbon in samples taken from each plant component of the two species was determined using dichromate oxidation and colorimetry using spectrophotometer. Partitioning of biomass between above (A) and below (B) ground components is approximately 3:1, revealing that the pattern resembles more of that of terrestrial plants (A/B = 3.9-4.5) than mangrove species in higher latitudes (A/B = 2-3). A positive correlation (p<0.01) and non-linear relationship (linear log-log relationship) was revealed between dbh and biomass (component and total) of the two species and allometric equations were derived that could be used to quantify carbon-sink function of mangrove ecosystems comprised of these species and the potential of mangroves in carbon mitigation programmes with financial incentives for mangrove conservation. The average amount of carbon retained by an individual was 9.16 kg per tree and thus the total organic carbon retained by L. racemosa in the mangrove ecosystem in Kadolkele was 9.44 t/ha while that of B. gymnorrhiza, was 5.6 t/ha, despite its greater capacity of individual carbon retention (13.76 kg per tree) due to its relatively low density and basal area. L. racemosa contains higher percentage of carbon in the stems, branches and roots than B. gymnorrhiza revealing its superior contribution to carbon-sink function of mangrove ecosystemsItem Coastal vegetation structure and resistance southern coast of Sri Lanka in the mitigation of tsunami impacts(Sri Lanka Association for the Advancement of Science, 2008) de Silva, K.H.W.L.; Amarasinghe, M.D.The present study is an attempt to investigate the relationship between coastal vegetation structure and its capacity to resist wave energy. Thickness of tsunami sand deposits at Rekawa, Kalametiya and Kirinda were measured and used as indicators of degree of resistance by vegetation against tsunami wave that passed through the mangrove vegetation at the respective localities. Belt transects of 30 -40 m long which were laid perpendicular to the lagoon/estuarine shoreline and parallel to each other and at 30-70 m distance from the shoreline were used to collect data on vegetation structure and each was divided into 10 m ×10 m plots. The locations of each tree, sapling, seedling and stump of trees and also girth and height of trees were measured. Moreover thickness of the sand deposited by tsunami wave was taken by digging 1` × 1` pits on the ground. Thus pits were made in each plot along seaward to landward gradient. The results suggest that mangroves and Pandanus odoratissimus communities of closely spaced trees with widely branching canopies, trees with intermediate diameter and greater forest width provide the greatest resistance against tsunami by reducing inundation distance inundation depth and flow velocity of tsunami waves, which explained that coastal forests lessen damage to property and reduce loss of life. Results further explained that wide crowns with prolific branching of Avicennia marina and P. odoratissimus with stilt/ prop roots and dense foliage exhibit the greatest drag resistance against the tsunami wave.Item Effect of vegetation structure on carbon assimilation capacity of mangrove ecosystems in the east coast of Sri Lanka(2014) Perera, K.A.R.S.; Amarasinghe, M.D.Item Growth and accumulation of NaCl of Avicennia marina seedlings under varying salinity conditions: implications on desalination potential(Sri Lanka Association for the Advancement of Science, 2009) de Silva, K.H.W.L.; Amarasinghe, M.D.Item Human influence on structure of mangrove vegetation in Negombo estuary(Sri Lanka Association for Fisheries and Aquatic Resources, 1999) Perera, K.A.R.S.; Amarasinghe, M.D.Item Mangrove vegetation structure and the abundance of shrimps in Chilaw lagoon, Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 1999) Jayasundera, J.W.K.K.; Amarasinghe, M.D.; Ranawana, K.B.Item Nitrate, phosphate and sulfate concentrations of well water in CKDu endemic areas and non-endemic areas and their relation to water hardness(Sri Lanka Association for the Advancement of Science, 2013) Fonseka, S.I.; Amarasinghe, M.D.; Paranagama, P.A.Item Phytoremediation capacity of selected Filicophytes ( Adiantum latifolium L., Christella hispidula and Pteris vittata L.) in improving quality of ground water through removing hardness(Sri Lanka Association for the Advancement of Science, 2014) Kannangara, D.P.B.; Amarasinghe, M.D.Item Preliminary investigations on the groundwater hardness in Polpithigama and use of selected plant parts for hardness reduction(Sri Lanka Association for the Advancement of Science, 2013) Jayasiri, U.D.S.C.; Amarasinghe, M.D.Item A preliminary study on impact of agrochemical-free rice cultivation on soil characteristics(Sri Lanka Association for the Advancement of Science, 2015) Gamage, P.G.I.J.; Amarasinghe, M.D.Item A preliminary study on nutritional quality of an indigenous rice variety (Kuruluthuda) and a hybrid rice variety (BG 358)(Institute of Biology, Sri Lanka, 2015) Gamage, P.G.I.J.; Amarasinghe, M.D.Item Structural complexity of strand vegetation and coastal erosion along the South, South West, and West coasts of Sri Lanka(Sri Lanka Association for the Advancement of Science, 2008) Gunawardena, D.T.; Amarasinghe, M.D.Structural complexity of coastal vegetation at eight different coastlines (Weligama, Unawatuna, Hikkaduwa, Ambalangoda, Induruwa, Kalutara, Moratuwa, and Uswetakeiyawa) was analyzed to determine the effect of structural complexity of coastal vegetation on coastal erosion. Vegetation samples were obtained along the belt transects laid perpendicular to the shoreline at each study site. Biomass, cover, density, basal area, diversity, and species richness of coastal vegetation were analyzed to determine the structural complexity of coastal vegetation. Coastal vegetation structure varied among different coastlines with varying erosion rates. An ordination was performed using principal component analysis to examine the relationship between coastal vegetation structure and erosion rates of different coastlines. Analysis revealed that there is a statistically significant relationship between erosion rate and the structural parameters of the coastal vegetation in the zone close to the shoreline (0-10 m). Which means erosion rates decreased with increasing values of structural parameters (indicating structural complexity) of coastal vegetation in the zone (0-10 m) close to the upper limit of the wave breaking area of the coast.Item Structure of macrophyte communities in a freshwater wetland and their relative capacity of Nitrogen retention(Sri Lanka Association for Fisheries and Aquatic Resources, 2003) Jayawardhana, W.M.P.; Amarasinghe, M.D.Item Substrate characteristics and species diversity of marine angiosperms in a micro-tidal basin estuary on the west coast of Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2007) de Silva, K.H.W.L.; Amarasinghe, M.D.Item Vegetation structure and potential gross primary productivity of mangroves at Kadolkele in Meegamuwa (Negombo) estuary, Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Jayakody, J.M.A.L.; Amarasinghe, M.D.; Pahalawattta Arachchi, V.; de Silva, K.H.W.L.Item Vegetative propagation of some selected mangrove species from Negombo estuary, Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2010) de Silva, K.H.W.L.; Amarasinghe, M.D.