Browsing by Author "Amarasinghe, M.D."

Now showing 1 - 20 of 35

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.
Anti-oxidant activity of selected endo lichenic fungi (ELF) in mangrove ecosystem of Puttalam lagoon.
(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Maduranga, H.A.K.; Attanayake, R.N.; Amarasinghe, M.D.; Weerakoon, G.; Paranagama, P.A.
Natural products based drug development has become an attractive area of research since there are limited options available to treat certain non-infectious diseases such as diabetes. Among these natural products, it has been reported that secondary metabolites of endolichenic fungi (ELF), have the ability to produce promising bioactive compounds. The objectives of this research were to isolate and identify ELF inhabiting mangroves in Puttalam lagoon, Sri Lanka using classical and DNA barcoding approach and to determine anti-oxidant activity of their secondary metabolites. Lichen hosts were collected from Puttalam lagoon in two different sites near, Athathale and around the NARA institute. The ELF were isolated following a standard procedure: a small piece of the thallus was surface sterilized, cut into pieces and dried on sterilized filter papers and then placed on malt extract agar in Petri dishes and incubated at room temperature (28 ⁰C – 30 ⁰C ) . Once pure cultures were obtained, seven isolates were randomly selected for DNA extraction following standard procedures. Quality of DNA was checked by agarose gel electrophoresis. Fungal internal transcribed spacer (ITS) region was amplified using polymerase chain reaction (PCR) with universal ITS 1 and ITS 4 primers and PCR products were sequenced using Sanger dideoxy chain-termination technology. DNA sequences were edited using BioEdit software and compared with the available sequences in the GenBank using Basic Local Sequence Alignment Search Tool (BLAST). In addition, morphological characterization of each fungal isolate was also carried out. Secondary metabolites from each isolate were extracted with ethylacetate separately and the solvent was evaporated under reduced pressure to obtain the crude extract. Free radical scavenging activity of the extracts were evaluated using 2, 2-diphenyl-1-picrylhydrdrazyl (DPPH) assay. Based on the highest sequence similarity to the GenBank sequences, isolates were identified as Diaporthe arengae (98 %), Neurospora crassa (100%), Lasiodiplodia theobromae (100 %), Schizophyllum commune (98 %), Diaporthe musigena (98 %), Hypoxylon anthochroum (98 %) and Nigrospora sphaerica (98%). IC50 values of extracts of Diaporthe arengae, Neurospora crassa and Lasiodiplodia theobromae were 375.9± 0.062μg/mL, 304.9±0.057 μg/mL and 211.2± 0.086 μg/mL respectively. Since percent inhibitions of the rest of the isolates were less than 50 % in the test doses, IC50 values were not calculated. All of the values were compared with standard Butylated Hydroxy Toluene (BHT) (IC50=108.0±0.072). Out of the seven ELF tested, L. theobromae showed the highest DPPH radical scavenging activity. Further testing of the rest of the isolates are being carried out and ELF may provide a good source of antioxidants for biotechnological applications.
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.
Can Avicennia marina produce substitutes for pneumatophores?
(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Ambagahaduwa, I.M.; Amarasinghe, M.D.
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 ecosystems
Chronic arsenic toxicity among patients of Chronic Kidney Disease of unknown etiology (CKDu) in North Central Province, Sri Lanka
(University of Kelaniya, 2011) Jayasumana, M.A.C.S.; Paranagama, P.A.; Fonseka, S.I.; Amarasinghe, M.D.; Rajakaruna, L.; Wijewardena, C.
In recent years, a significant increase in patients of Chronic Kidney Disease of unknown etiology (CKDu) has been observed in some parts of Sri Lanka, especially in North Central Province. Uniqueness of this disease is that its victims do not share the same history as other kidney patients who have had it either due to diabetes, high blood pressure or glomerulonephritis. A reconnaissance survey was conducted in the 12 CKDu endemic villages, followed by a door-to-door visit for clinical assessment and biological sample collection of CKDu patients among the villagers (n=125). Control group (n=180) were selected from those individuals from the study area who had not been diagnosed to have CKDu and some of them were selected randomly from family members of CKDu patients. Hair and urine samples were collected from both CKDu patients and controls. The clinical assessment of patients and some individuals from control group had shown dermal manifestations of chronic arsenic (As) poisoning (CAP). 44.8% and 39.2%of the CKDu patients and 18.8% and 14.4% of the control group had hyper pigmentation of palms and soles respectively. 23.2% of the CKDu patients and 10.5% of the controls have shown keratosis of palms. In soles it was 17.6% and 8.3% respectively. Hair and urine samples from CKDu patients have shown presence of high amounts of As which exceed the toxic level. Generalized body weakness, headache, burning of eyes, nausea, mild to moderate hepatomegaly, epigastric pain and parasthesia, the other clinical symptoms of CAP were also observed among a significant proportion of CKDu patients in the sample but to a lesser extent among the individuals of the control group. Findings of the present study reveal that 52% of the CKDu patients and 14.4% of the subjects in the control group have shown symptoms required to be diagnosed CAP. Percentage CKDu patients who fulfill the requirements for CAP were greater than that among the control group. Observable CAP symptoms among individuals of the control group indicate that being inhabitants of the same area, consuming the same As-contaminated water, majority of the population has already bio-accumulated arsenic, nevertheless to a lesser extent than those who have been diagnosed as CKDu patients. This also implies that these individuals are of high risk in acquiring CKDu in the near future.
Chronic Kidney Disease of Unknown Etiology (CKDu) and Arsenic in Groundwater in Sri Lanka
(Water Resources Board, Colombo, 2011) Jayasumana, C.; Paranagama, P.A.; Amarasinghe, M.D.
In recent years a significant increase in patients of Chronic Kidney Disease of unknown etiology (CKDu) has been observed in some parts of Sri Lanka, especially in Medawachchiya, Padaviya, Kebitigolawa, Medirigiriya (North Central Province), Nikawewa (North Western Province), Dehiattakandiya (Eastern Province) and Giradurukotte (Uva Province). Uniqueness of this disease is that its victims do not share the same history as other kidney patients who have had it either due to diabetes, high blood pressure, past snake bites or urinary tract infections. Etiology of this disease has since been attributed to a range of causes, including presence of the heavy metal cadmium in water that would potentially have introduced to water from inorganic fertilizer used in paddy fields, presence of excessive amounts of fluoride in drinking water and prevalent use of low quality aluminum utensils, presence of toxins produced by microorganisms such as cynobacteria in water. Despite the effort of about 60 researchers including those who were funded by WHO (World Health Organization) over the last decade, none of these hypotheses have been supported with evidence; in fact, the data available prove them not to be the cause. The causative factors and etiology of this chronic kidney disease therefore is still considered uncertain or unknown and abbreviated as CKDu with recommendations of the National Research Programme for CKD of the Ministry of Health in Sri Lanka.
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.
Determination of Arsenic Content in Synthetic and Organic Manure Based Fertilizers Available in Sri Lanka
(International Conference on Chemical Sciences, 2012) Fernando, A.; Paranagama, P.A.; Jayalath, K.; Fonseka, S.; Amarasinghe, M.D.; Senanayake, K.; Jayasumana, C.; Mahamithawa, P.; Wijewardhane, C.; Samarasinghe, D.; Dahanayake, K.S.
Development of allometric equations to determine above and below ground biomass and organic carbon content in Bruguiera gymnorrhiza and Lumnitzera racemosa
(University of Kelaniya, 2011) Perera, K.A.R.S.; Saparamadu, M.D.J.S.; Amarasinghe, M.D.
Bruguiera gymnorrhiza and Lumnitzera racemosa are two species of true mangroves commonly found in Sri Lankan mangrove areas. Determination of amount of carbon assimilated by these two species therefore, is of considerable importance to estimate the carbon fixing capacity of Sri Lankan mangrove areas. Objective of the present study therefore, is to develop allometric relationships between biomass of stems, leaves, below and above ground roots with easily measured variables such as girth/ diameter at breast height (gbh/dbh) that can be used in estimating the carbon assimilation capacity of Sri Lankan mangrove ecosystems. The below ground biomass of trees of the two mangrove species accounted for 20 – 44 % of the total biomass of the plants. The ratio (A/B) between above (A) to below (B) ground biomass of Lumnitzera racemosa ranged 1.4 – 3.9 and that for Bruguiera gymnorhiza was 1.2 – 4.4, indicating relatively greater amount of biomass in the below ground root systems.Data on dry weight of plant components were analyzed with SPSS ver.16 and a strong positive correlation (p<0.01) and non-leaner relationship (r2 >0.80) were revealed for stems, roots, above ground and total biomass of plants with dbh of individuals of the two species. Four allometric equations were derived between biomass of different components with dbh of Bruguiera gymnorrhiza ; biomass of stem= 0.115 (dbh)2.386, biomass of root = 0.100 (dbh)2.364, above ground biomass =0.289 (dbh)2.327 and total biomass (above +below)= 0.405 (dbh)2.320 . Four other allometric equations were derived between biomass of different components with dbh of Lumnitzera racemosa; biomass of trunk= 0.098 (dbh)2.244, biomass of root = 0.118 (dbh)2.063, above ground biomass =0.114 (dbh)2.523 and total biomass (above +below)= 0.220 (dbh)2.376 . Using the organic carbon content embodied in biomass of the components of the plants of the two species, equations were altered to represent the relationship between organic carbon present and the dbh. Organic carbon content in Bruguiera gymnorhiza stem=0.0631 (dbh)2.386 and root = 0.0529 (dbh)2.364 and organic carbon content Lumnitzera racemosa trunk = 0.0546 (dbh)2.244 and root= 0.0624 (dbh)2.063 . These allometric relationships are required to estimate the amount of carbon accumulated in the plants of these mangrove species and thus the carbon assimilation capacity of the mangrove stands that comprise these mangrove species.
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.
Effect of vegetation structure on potential gross primary productivity of mangrove ecosystems in Negombo estuary, Sri Lanka
(Research Symposium 2010 - Faculty of Graduate Studies, University of Kelaniya, 2010) Perera, K.A.R.S.; Amarasinghe, M.D.; Pahalawathaarachchi, V.
Photosynthetically active radiation (PAR) absorbed by the plant canopies/ leaves gives a reliable measure of its gross primary production. The potential gross primary productivity of two mangrove stands, i.e. Kadolkele (70 11’42.18” - 7011’50.48” N; 790 50’32.08” – 790 50’47.50” E) a relatively undisturbed natural mangrove area and a cultivated and selectively harvested stand at Wedikanda (70 11’18.29” – 70 11’29.09” N; 790 49’56.37” – 790 50’04.96” E) located at northern part of the Negombo estuary were studied in relation to mangrove vegetation structure which was characterized with species richness, plant density, basal area and stand height. Amount of PAR absorbed by the canopies of two mangrove stands were estimated by calculating leaf area index (LAI) values obtained from the relationship between incident PAR and PAR under the canopy that were measured using LI-191SA line Quantum sensor during wet (raining) and dry seasons. Natural mangrove stands at Kadolkele were revealed to be structurally more complex/ superior with a complexity index value of 42.36, in comparison to that of Wedikanda which recorded a value of 22.48. LAI in both study areas recorded higher values for the zone near the estuarine shoreline and it decreased towards inland. LAI recorded higher values in wet season ( Kadolkele 7.336 and Wedikanda 6.157) than in the dry period (Kadolkele 6.693 and Wedikanda 5.896). Gross primary productivity too showed a similar trend as structural diversity, along the estuary-land gradient and it was manifested in both the mangrove stands. Kadolkele recorded relatively a high average potential gross primary productivity, i.e. 24.541 t/ha/yr than Wedikanda that recorded 21.011 t/ha/yr. Artificial selection of mangrove species for planting and periodic harvesting of mangrove branches to construct a traditional fishing device known as “brush parks” may contribute to the lower gross primary productivity value of the cultivated mangrove stands at Wedikanda.
Effect of vegetation structure on primary productivity of mangroves at Kadolkele in Negombo lagoon
(Sri Lanka Association for Fisheries and Aquatic Resources, 2006) Jayakodi, J.M.A.L.; Amarasinghe, M.D.; Pahalawattaarachchi, V.
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.
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.
In-vitro and in-vivo Seed Germination Percentage of Typha angustifolia
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Madushani, K.P.K.; Amarasinghe, M.D.; Ratnayake, R.M.C.S.; Dahanayaka, D.D.G.L.
Typha is a cosmopolitan genus and T. angustifolia is considered an alien invasive plant species in Sri Lanka. Extensive distribution of T.angustifolia is observed in Bundala wetland complex during the recent past. Seed germination is an important process that contributes to plant distribution and invasiveness. Therefore, this study aimed to investigate the in-vitro and in-vivo seed germination of T.angustifolia seeds to evaluate the percentatge seed germination of Typha seeds. Typha seeds were collected from Bundala wetland complex, Hambantota, Sri Lanka (6°12′50″N; 81°13′30″E) during the South West monsoon windy season (seed dispersing period). Typha seeds were cleaned with distilled water and settled in distilled water to select the most viable seeds, which sink to the bottom of the container, whereas non-viable seeds float. Seed viability was tested by placing 50 seeds on cavity slides with 3% 2,3,5-triphenyltetrazolium chloride (TTC) solution and percentage seed viability was calculated after incubating in dark for 8 hours. For the seed germination test, 50 seeds were placed on a layer of Whatman grade no. 1 filter paper (pH 7) in 90mm petri dishes and watered weekly. Seed was counted as germinated when the radical reached 2 mm. For seedling emergence test, 50 seeds were sown in lagoon soil in trays at 0.5 cm depth, which were collected from Bundala wetland complex and they were weekly irrigated with distilled water. A seedling was considered emerged when the hypocotyl was fully erect. All tests were replicated 5 times. Finally the percentage seed germination and percentage seedling emergence were calculated. Results indicate that there is a significant difference (p<0.05) between seed viability in TTC test and seed germination in petri dishes/ seedling emergence in soil trays. TTC test resulted in 87.2±7.2% seed viability, but only 51.2±2% of seedlings germinated in soil trays. Seedlings were emerged after 2 to 3 weeks of sowing. However radicals were failed to appear in petri dishes. Therefore, results conclude that even though T.angustifolia bear numerous viable seeds they show moderate percentage seed germination in wetland soils. It may be due to seed dormancy and further investigations are recommended to evaluate the effect of seed dormancy on distribution of T. angustifolia.
Investigation of the Negombo estuary (Sri Lanka) brush park fishery, with an emphasis on community-based management
(Fisheries Management and Ecology, 2002) Amarasinghe, U.S.; Amarasinghe, M.D.; Nissanka, C.
The Negombo estuary brush park fishery in Sri Lanka was investigated from June 1998 to March 1999. The mean fish yield (all species) in the fishery was 12.46 t ha?1 yr?1. Fin fish species formed about 91% of the yield and the rest was formed by penaeid shrimps and crabs. Fish yield and the twig density in the brush park exhibited a second order polynomial relationship indicating a minimum yield at an intermediate value of twig density in the brush parks. The relationship between fish yield and duration of implantation of brush parks showed an optimal period of 30?40 days for high fish yields. Income levels of fishermen, availability of construction material and suitable sites for implantation of brush parks are some of the factors determining size and number of brush parks per fisherman and duration of installation. Indigenous knowledge within the fishing community about the effect of salinity variations, twig density and mangrove species used on the harvests greatly contribute to effective operation of this fishing practice. Cultivation of mangroves to obtain twigs and branches is a unique feature in this estuary. Indigenous knowledge on mangroves has led to the adoption of sound silvicultural practices. Although cultivating mono-specific mangrove stands may not increase diversity of mangrove forests, it reduces denudation of naturally occurring mangrove forests because of brush park construction, and retains habitats for other organisms. Mangrove management plans in the Negombo estuary should therefore be viewed and treated in an integrated manner that takes into account both resource and social components.
Mangrove soils are superior carbon sinks: Evidence from Sri Lankan mangrove ecosystems
(Sri Lanka Association for Fisheries and Aquatic Resources, 2015) Perera, K.A.R.S.; Amarasinghe, M.D.
Mangroves are among the most carbon rich ecosystems in the tropics. Inundation with tides and land-based surface runoff leads to anaerobic soil conditions that are conducive for accumulation of partially decomposed organic carbon. Present study was conducted to assess quantitatively the capacity of mangrove soils in retaining organic carbon. Distribution of total organic carbon (TOC) in soils of mangrove ecosystems in Negombo, Chilaw, Kala Oya, Malwathu Oya, Uppar, Batticaloa and Rekawa lagoons/estuaries, that represent western eastern and southern coasts as well as wet and dry climatic zones of Sri Lanka, was determined by using soil samples taken along the water-land gradient at 0-15 cm, 15-30 cm and 30-45 cm depths. Dichromate oxidation followed by colorimetric measurements were used to determine the percentage TOC and TOC densities were calculated using bulk density and % TOC values. Except for Batticaloa and Uppar lagoons in the dry zone, relatively a high soil TOC contents were observed in the surface soil layers (0-15 cm depth). By and large, the area between 10-30 m from the shoreline retained the highest average TOC in all mangrove areas. The highest percentage TOC in Sri Lankan mangrove soils is found not at the surface layer (4.92 - 15.1 % at the surface – 15 cm depth), but the layer below it down to a depth of 30 m (5.31 – 9.87 % at 16 – 30 cm depth). Soil beneath 30 cm contained the lowest amount (3.05 – 8.34 % at 31 -45 cm depth). Average TOC density of surface soil was 0.066 - 0.145 g cm-3 and in it was higher in mangroves of wet and intermediate climatic zones than those in the dry zone. The carbon retention capacity of Sri Lankan mangrove soils therefore was calculated to range between 313 – 492 t ha-1 and the highest was found to occur in the wet zone while it was 414 t ha-1in the intermediate zone. Soils of mangroves in the dry zone retained approximately 361 t ha-1 .of organic carbon up to a depth of 45 cm. The TOC retained by the soils of mangrove areas in Sri Lanka can be estimated as 5816 x 103 t. Inundation frequencies and durations as well as other bio-physical factors may affect the magnitude of TOC in mangrove soils.
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.
Net photosynthetic production and potential carbon assimilation capacity of mangroves of Kadolkele in Negombo estuary, Sri Lanka
(University of Kelaniya, 2011) Perera, K.A.R.S.; Saparamadu, M.D.J.S.; Amarasinghe, M.D.
Mangroves are considered as highly productive ecosystems that have considerable potential to serve as efficient sinks of carbon, both on short and long time scales. Magnitude of mangrove primary productivity is highly variable in space and time and it depends on factors such as tidal flushing, latitude, temperature, salinity and nutrient regimes as well as substrate characteristics. Net primary production is represented by above and below ground biomass, litter production and the rate of grazing by herbivores. Since results of very few studies on primary productivity of Sri Lankan mangroves are available, the present study was conducted with the objective of understanding the net primary productivity and magnitude of net carbon assimilation capacity of mangrove ecosystem at Kadolkele. The study was conducted at Kadolkele (7011‟42.18”- 7011‟50.48” N; 790 50‟32.08”– 790 50‟47.50” E), a relatively undisturbed natural mangrove stand extending over 13.5ha, at the northern end of Negombo estuary. Data on biomass increment and litterfall during study period were gathered from twenty 10 m x10 m permanent study plots of three belt transect of 10 m wide laid perpendicular to the shoreline. Annual increment of above and below ground biomass was calculated by girth (gbh) increment, using allometric relationships developed between gbh and biomass of mangrove trees. Biomass loss through herbivory was assumed to be negligible due to high tannin content in mangrove plant parts and thus their low palatability. Organic carbon content of each component of mangrove trees was determined by Walkey and Black wet oxidation without external heating procedure followed by colorimetric method to determine absorbance at 600 nm, using a UV- visible spectrophotometer. Annual organic carbon accumulation was calculated from NPP and organic carbon content. Relatively high values of NPP were recorded from the water-front areas of the mangrove stand and it decreased towards inland. Annual total organic carbon increment was recorded to be 1232.17 + 9.23 g m-2y-1 of which 682.80 + 7.51 g m-2y-1 was found deposited in the above ground woody parts while 396.46 + 4.65 g m-2y-1 was in the plant litter and 152.91 + 1.94 g m-2y-1 in the roots. Potential capacity of Kadolkele mangroves in assimilating and accumulating carbon is 166.66 t y-1 and this amount is equivalent to the amount of carbon emitted as CO2 by combustion of 272,694 (nearly quarter of a million) liters of diesel in motor vehicles. Assuming a motor car consumes 1200 liters of diesel per year, this mangrove stand at Kadolkele with an extent of 13.5 ha can remove atmospheric carbon produced by 227 cars during one year.