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Item Response of mangrove plant species to a saline gradient: Implications for ecological restoration(Acta Botanica Brasilica, 2021) De Silva, W.; Amarasinghe, M.Mangroves are salt tolerant plants that occur in tropical and sub-tropical sheltered coasts. Saltwater intrusions into terrestrial landscapes often occur due to either anthropogenic reasons or natural calamities such as tsunamis. We investigated the potential of using mangrove species for rehabilitation of high saline environments by revealing the capacities of species to remove salt from sediment. We established the salt retention capacity of common mangrove species in Sri Lanka i.e., Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal, and Avicennia marina through exsitu and in-situ measurements of NaCl content in plant tissue and soil samples, by titrating with 0.01 N AgNO3. The results revealed A. marina to be the most efficient in retaining salt within plant tissues while C. tagal is superior to R. mucronata but inferior to A. marina in performing this function. These findings were further confirmed by measuring salt uptake rates of hydroponically grown seedlings of the same species. Although R. mucronata is the most popular species used for restoration, A. marina appears the most suitable mangrove species not only for coastal mangrove restoration but also for rehabilitating salinity affected landscapes.Item Substrate characteristics and species diversity of marine angiosperms in a micro-tidal basin estuary on the west coast of Sri Lanka(Sri Lanka Journal of Aquatic Sciences, 2010) De Silva, K.; Amarasinghe, M.Diversity of marine angiosperm species (seagrasses) at Kadolkele in Meegamuwa (Negombo) estuary was studied with a view to understanding the effect of substrate characteristics on diversity. Seagrass samples were obtained along three line transects, laid perpendicular to the shoreline at 20 m intervals. Shannon-Wiener index was used to determine the species diversity of seagrasses in the study site at Kadolkele that was divided into three strata, demarcated by the distance, i.e. 0-10 m, 10-20 m and 20-30 m from the shoreline. Comparison of Shannon-Wiener index values indicated that the diversity of first stratum close to the shoreline was significantly different from that of the other two among which no significant difference was found to occur. Substrate pH, soil electrical conductivity, organic mater content and particle size distribution were measured from the substrate samples taken from each stratum. No statistically significant difference was observed with pH (3.92-6.82) and particle size distribution among the three strata. Soil electrical conductivity and organic matter content of stratum 3 however, was significantly different (p< 0.05) from the other two strata. Kadolkele seagrass bed consisted of two species and Halodule pinifolia (5822 shoots m-2) dominated over Halophila ovalis (1030 shoots m-2). The area adjacent (0-3 m) to the mangroves at the shoreline was devoid of seagrasses and H. ovalis was absent in stratum 1, indicating that substrate characteristics have a marginal effect on the species richness of the seagrasses. Although species richness was similar in the other two strata, higher (Shannon) evenness (0.231), despite the relatively low abundance in stratum 2, contributes to its higher species diversity. Present study therefore documents the subtle habitat partitioning of co-existing marine angiosperm species in a limited area in Meegamuwa estuary.Item Potential impact of predicted sea level rise on carbon sink function of mangrove ecosystems with special reference to Negombo estuary, Sri Lanka(Global and Planetary Change, 2018) Perera, K.; De Silva, K.; Amarasinghe, M.Unique location in the land-sea interface makes mangrove ecosystems most vulnerable to the impacts of predicted sea level rise due to increasing anthropogenic CO2 emissions. Among others, carbon sink function of these tropical ecosystems that contribute to reduce rising atmospheric CO2 and temperature, could potentially be affected most. Present study was undertaken to explore the extent of impact of the predicted sea level rise for the region on total organic carbon (TOC) pools of the mangrove ecosystems in Negombo estuary located on the west coast of Sri Lanka. Extents of the coastal inundations under minimum (0.09 m) and maximum (0.88 m) sea level rise scenarios of IPCC for 2100 and an intermediate level of 0.48 m were determined with GIS tools. Estimated total capacity of organic carbon retention by these mangrove areas was 499.45 Mg C ha− 1 of which 84% (418.98 Mg C ha− 1) sequestered in the mangrove soil and 16% (80.56 Mg C ha− 1) in the vegetation. Total extent of land area potentially affected by inundation under lowest sea level rise scenario was 218.9 ha, while it was 476.2 ha under intermediate rise and 696.0 ha with the predicted maximum sea level rise. Estimated rate of loss of carbon sink function due to inundation by the sea level rise of 0.09 m is 6.30 Mg C ha− 1 y− 1 while the intermediate sea level rise indicated a loss of 9.92 Mg C ha− 1 y− 1 and under maximum sea level rise scenario, this loss further increases up to 11.32 Mg C ha− 1 y− 1. Adaptation of mangrove plants to withstand inundation and landward migration along with escalated photosynthetic rates, augmented by changing rainfall patterns and availability of nutrients may contribute to reduce the rate of loss of carbon sink function of these mangrove ecosystems. Predictions over change in carbon sequestration function of mangroves in Negombo estuary reveals that it is not only affected by oceanographic and hydrological alterations associated with sea level rise but also by anthropogenic processes, therefore the impacts are site specific in terms of distribution and magnitude.Item Arsenic and hardness in ground water from Chronic Kidney Disease of Unknown Etiology (CKDU) prevalent areas and non-CKDU prevalent areas in Sri Lanka(Postgraduate Institute of Science, University of Peradeniya, 2012) Fonseka, S.; Jayasumana, C.; Jayalath, K.; Amarasinghe, M.; Senanayake, K.; Wijewardhane, C.; Samarasinghe, D.; Dahanayake, K.; Mahamithawa, P.; Paranagama, P.A.Increasing hardness and deteriorating quality of groundwater, the primary source of potable water, has been the general observation of inhabitants of areas where chronic kidney disease of unknown etiology (CKDu) is prevalent. Present study was conducted during 2011, to determine the groundwater hardness and presence of arsenic in Padavi- Sripura, Polpithigama, Moneragala, Thanamalwila in the dry climatic zone and in Pasagoda in the wet zone. Total hardness of the water samples collected from dug wells and tube wells was measured using EDTA titration (EPA 130.2) and arsenic content was measured using GF-AAS after filtration and acid digestion (EPA 7060A). Highest average groundwater hardness (466+34 mg l-1) was observed at Padavi-Sripura (n= 28) and the values ranged from 270+54 – 820+62 mg l-1). Arsenic content in water ranged from 21.07+3.54 to more than 100.91+12.31 !" #-1. The second most hardwater was found from Polpithigama area (n= 16) which ranged 90+8 – 615+47 mg l-1. Arsenic content in water ranged 2.49+0.61 – 60.55+7.21 !" #-1. The lowest hardness in groundwater among the test sites was observed at Moneragala (n=38), where the hardness ranged 10+2 – 340+31. The arsenic content ranged 2.14+0.84 – 52.47+6.71 !"#-1. Groundwater at Thanamalwila (n=19) recorded hardness value, i.e. 279+26 mg l- 1-with a range 170+8 - 500+24 mg l-1 and the arsenic content in water ranged 39.37+5.21- >100.42+9.45 !" #-1. Groundwater at Pasgoda, the control site of this study, was not hard (60+5 mg l-1) and arsenic was not detected. Statistical analyses reveal that a positive correlation exists between total hardness of groundwater and the arsenic content in it.Item Human dependence on mangrove resources and its implications on the management of mangrove ecosystems in Sri Lanka(Institute of Biology, Sri Lanka, 1999) Amarasinghe, M.Item Presence of arsenic in Sri Lankan rice(Springer, 2015) Jayasumana, C.; Paranagama, P.A.; Fonseka, S.; Amarasinghe, M.; Gunatilake, S.; Siribaddana, S.Background: Arsenic and heavy metals are implicated in causation of CKDu among farmers in dry zone of Sri Lanka. Rice has been identified as a major source of arsenic in research carried out in other countries. We analyzed 120 samples of new improved varieties (NIVs) and 50 samples of traditional varieties (TV) of rice for total arsenic content. Findings: Rice cultivated in Sri Lanka is contaminated with arsenic. Agrochemical dependent NIVs contain considerable amount (20.6 -540.4 μg/Kg) of arsenic. There is no difference between the arsenic content in NIV rice samples from areas where there is high or low prevalence of CKDu. TVs that are cultivated without using agrochemicals contain significantly less arsenic (11.6 - 64.2 μg/Kg). However, it is evident that the TVs also contain toxic metals if they are grown with fertilizers and pesticides. Conclusion: A high proportion of arsenic in rice exists in the inorganic form. Sri Lanka is a nation with high per capita consumption of rice. Codex Alimentarius recommends the maximum allowable limit for inorganic arsenic in rice as 200 μg/kg. Assuming that 70% of the total arsenic content exists in the inorganic form, this corresponds to a level of about 286 μg/kg of total arsenic. As such, 11.6% of the samples of NIVs exceeded this maximum recommended level in polished rice. Inorganic arsenic is a non-threshold carcinogen. Research should be focused on developing rice varieties that do not retain arsenic within the rice grain.Item Phosphate fertilizer is a main source of arsenic in areas affected with chronic kidney disease of unknown etiology in Sri Lanka(SpringerPlus, 2015) Jayasumana, C.; Fonseka, S.; Fernando, A.; Jayalath, K.; Amarasinghe, M.; Gunatilake, S.; Siribaddana, S.; Paranagama, P.A.Chronic Kidney Disease of unknown etiology (CKDu) has escalated into an epidemic in North Central Province (NCP) and adjacent farming areas in the dry zone of Sri Lanka. Studies have shown that this special type of CKD is a toxic nephropathy and arsenic may play a causative role along with a number of other heavy metals. We investigated the hypothesis that chemical fertilizers and pesticide could be a source of arsenic. 226 samples of Fertilizers and 273 samples of pesticides were collected and analyzed using atomic absorption spectrometry and inductively coupled plasma mass spectrometry for arsenic and other heavy metals in two university laboratories. Almost all the agrochemicals available to the farmers in the study area are contaminated with arsenic. The highest amount was in triple super phosphate (TSP) with a mean value of 31 mg/kg. Also TSP is a rich source of other nephrotoxic metals including Cr, Co, Ni, Pb and V. Annually more than 0.1 million tons of TSP is imported to Sri Lanka containing approximately 2100 kg of arsenic. The next highest concentration was seen in the rock phosphate obtained from an open pit mine in NCP (8.56 mg/kg). Organic fertilizer contained very low amounts of arsenic. Arsenic contamination in pesticides varied from 0.18 mg/kg to 2.53 mg/kg although arsenic containing pesticides are banned in Sri Lanka. Glyphosate the most widely used pesticide in Sri Lanka contains average of 1.9 mg/kg arsenic. Findings suggest that agrochemicals especially phosphate fertilizers are a major source of inorganic arsenic in CKDu endemic areas. Organic fertilizer available in Sri Lanka is comparatively very low in arsenic and hence the farmers in CKDu endemic areas in Sri Lanka should be encouraged to minimize the use of imported chemical fertilizer and use organic fertilizers instead.Item Presence of arsenic in agrochemicals and their association with the agricultural chronic kidney disease in Sri Lanka(The Journal of Toxicology and Health, 2014) Jayasumana, C.; Fonseka, S.; Fernando, A.; Jayalath, K.; Amarasinghe, M.; Paranagama, P.Chronic Kidney Disease of Agricultural origin (CKDa) formerly known as Chronic Kideny Disease of unknown etiology (CKDu) is one of the biggest health problems in Sri Lanka. In recent years, a significant increase in CKDa cases have been observed in North Central Province (NCP) in Sri Lanka. Since majority of CKDa patients are farmers with chronic arsenic toxicity, the present study was aimed to assess the source of the arsenic in CKDa patients in selected rice farming areas, Padaviya, Mahawilachchiya and Polpithigama and evaluate the amounts of arsenic present in agrochemicals used by these farmers. This study was concentrated on the analysis of agrochemicals; synthetic and natural fertilizers and pesticides which continuously affect the human health. Samples of synthetic fertilizer, organic fertilizer and pesticides (insecticides, weedicides and fungicides) collected from selected CKDa prevalence areas were analyzed using atomic absorption spectrometer using hydride generator and graphite furnace. The highest amount of arsenic contamination was reported from triple super phosphate (TSP) used in cultivation of rice and it was in the range from 25 mg/kg to 37 mg/kg. Since the consumption of TSP for cultivation in Sri Lanka in 2012 was approximately 108,000 MT, the amount of arsenic introduced to Sri Lankan agricultural soils through imported TSP was calculated to be about 2100 kg. On contrary, organic fertilizer prepared with plant organic matter contained very low amounts of arsenic. Investigations carried out to detect presence of arsenic in pesticides showed 0.18 ppm to 2.53 ppm concentration of As. Arsenic has already been identified as one of the major etiological factors for the rapidly spreading CKDa among paddy farmers in the dry zone of Sri Lanka. Since analysis of soil profiles in the endemic areas had previously confirmed that source of arsenic is not from the bed rock, findings of the present study suggest that agrochemicals are the major source of arsenic in CKDa endemic areas.