Undisturbed Mangroves Research Articles

Marine estuaries act as better sink for greenhouse gases during winter in undisturbed mangrove than degraded ones in Sundarban, India

The estuaries provide the key pathway for travelling carbon across the land-ocean interfaces and behave as both source and sink of greenhouse gases (GHGs) in water-atmosphere systems. The sink-source characteristics of estuaries for GHGs vary spatially. The primary driving factors are adjacent ecologies (agriculture, aquaculture, etc.) and proximities to the sea. To study the sink-source characteristics of estuaries for GHGs (methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2)), the water samples were collected from 53 different locations in the estuaries for estimation of dissolved GHGs concentration and air-water GHGs exchanges. The locations represent five zones (Zone I, II, III, IV and V) based on the type and degradation status of mangroves (degraded and undisturbed), anthropogenic activities, and distance from the sea. Zone I, III, V represents to the degraded mangroves far from sea, whereas, Zone II, IV surrounded by undisturbed mangroves and nearer to sea. The average dissolved CH4 concentrations were higher in the estuaries which were adjacent to degraded mangroves (154.4 nmol L−1) than undisturbed mangroves (81.7 nmol L−1). Further, the average dissolved N2O concentrations were 48% higher in the estuaries nearer to degraded mangroves than that of undisturbed ones. Among the degraded mangrove sites, the dissolved CO2 concentrations were higher at Zone I (30.1 μmol L−1) followed by Zone III and IV, whereas in undisturbed sites, it was higher in Zone IV (22.3 μmol L−1) than Zone II (17.6 μmol L−1). Among the 53 locations, 36, 51 and 33 locations acted as a sink (negative value of exchanges) for CH4, N2O and CO2, respectively. The higher sink potential for CH4 was recorded to those estuaries adjacent to undisturbed mangroves (−791.69 μmol m−2 d−1) than the degraded ones (−23.18 μmol m−2 d−1). Similarly, the average air-water N2O and CO2 exchanges were more negative in the estuaries which were nearer to undisturbed mangroves indicating higher sink potential. The pH, and salinity of the estuary water were negatively correlated with air-water CH4 and N2O exchanges, whereas those were positively correlated with CO2 exchanges. Significantly lower dissolved GHGs and air-water GHGs exchange was observed in the estuaries adjacent to the undisturbed mangrove as compared to the degraded mangrove. The reason behind higher sink behaviours of estuaries nearer to undisturbed mangroves are higher intrusion of seawater, less nutrient availability, higher salinity, low carbon contents and alkaline pH compared to estuaries adjacent to degraded mangroves and far from sea.

Carbon Stocks Assessment in a Disturbed and Undisturbed Mangrove Forest in Ghana

Mangroves and other blue carbon ecosystems have long been recognised for their carbon sink function, yet the organic carbon stocks of mangroves in many countries in Africa remain to be assessed. This study evaluates the impact of traditional forest conservation on long-term carbon sequestration in a non-degraded (Amanzule) and a degraded (Kakum) mangrove forest system in Ghana (West Africa). The amount of carbon stored in mangrove trees was estimated from diameter-based allometric equations. Tree (above- and below-ground) carbon was ~34-fold higher in the Amanzule forest (mean = 0.89 ± 0.10 t/ha) than in the Kakum forest (mean = 0.026 ± 0.019 t/ha). Soil carbon density was estimated as organic carbon and bulk density at specific depths in both forests. Soil organic carbon density was ~5-fold higher in the Amanzule forest (mean = 2935.79 ± 266 t/ha) than the Kakum forest (mean = 554.01 ± 83 t/ha). The variation in the vertical distribution of soil carbon was not significant in either forest (F = 0.57; p > 0.05). These findings underscore the role of traditional conservation on mangrove carbon stocks and the need to consider the governance of coastal ecosystems when estimating blue carbon.

Soil Metagenome Revealed Contrasting Anammox Bacterial Diversity in Coastal Mangrove and Rice Ecology

Anammox (anaerobic ammonium oxidation), an anoxic microbial process plays an important role in nitrogen-dynamics in wetland ecologies. Although, the role of anammox bacteria is fairly studied in mangroves and coastal rice ecologies (anthropogenic wetland), but their diversities and specific role are still poorly documented. In this study, we elucidate the anammox bacterial diversities in relation to physico-chemical properties and labile nitrogen-fractions in soils of mangroves (undisturbed and degraded) and rice through whole-genome metagenomic approach. The average reads of anammox bacteria were higher in rice (647) followed by degraded (256) and undisturbed mangrove (101). Four predominant genera of anammox bacteria (Candidatus Scalindua, Candidatus Brocadia, Candidatus Jettenia and Candidatus Kuenenia) were identified in both mangrove and rice ecology. Among the four genera, Candidatus Scalindua was dominant in mangroves, whereas Candidatus Brocadia was dominant in rice. On the species level, the Candidatus Scalindua japonica was dominant in degraded mangroves while Candidatus Scalindua rubra was dominant in undisturbed mangroves. The Shannon-Weaver index depicting species richness of C. Scalindua was higher in undisturbed mangrove than degraded mangrove and rice. However, the index of other genera of anammox bacteria like C. Brocadia, C. Jettenia and C. Kuenenia were more in rice than the mangroves. The correlation study revealed that labile nitrogen fractions were higher in rice and positively correlated with the anammox bacterial community. However, anammox bacteria were negatively correlated with soil pH, EC, and salinity. Relative activities of anammox and denitrification processes need to be studied further to chalk out nitrous oxide emission mitigation strategies in wetland ecology.

Elucidation of dominant energy metabolic pathways of methane, sulphur and nitrogen in respect to mangrove-degradation for climate change mitigation

Mangroves play a key role in ecosystem balancing and climate change mitigation. It acts as a source and sink of methane (CH4), a major greenhouse gas responsible for climate change. Energy metabolic pathways of methane production (methanogenesis) and oxidation (methanotrophy) are directly driven by sulphur (S) and nitrogen (N) metabolism and salinity in coastal wetlands. To investigate, how mangrove-degradations, affect the source-sink behaviour of CH4; the pathways of CH4, S and N were studied through whole-genome metagenomic approach. Soil samples were collected from degraded and undisturbed mangrove systems in Sundarban, India. Structural and functional microbial diversities (KEGG pathways) of CH4, S and N metabolism were analysed and correlated with labile carbon pools and physico-chemical properties of soil. Overall, the acetoclastic pathway of methanogenesis was dominant. However, the relative proportion of conversion of CO2 to CH4 was more in degraded mangroves. Methane oxidation was higher in undisturbed mangroves and the serine pathway was dominant. After serine, the ribulose monophosphate pathway of CH4 oxidation was dominant in degraded mangrove, while the xylulose monophosphate pathway was dominant in undisturbed site as it is more tolerant to salinity and higher pH. The assimilatory pathway (AMP) of S-metabolism was dominant in both systems. But in AMP pathway, adenosine triphosphate sulfurylase enzyme reads were higher in degraded mangrove, while NADPH-sulfite reductase abundance was higher in undisturbed mangrove due to higher salinity, and pH. In N-metabolism, the denitrification pathway was predominant in degraded sites, whereas the dissimilatory nitrate reduction pathway was dominant in undisturbed mangroves. The relative ratios of sulphur reducing bacteria (SRB): methanogens were higher in degraded mangrove; however, methanotrophs:methanogens was higher in undisturbed mangrove indicated lower source and greater sink capacity of CH4 in the system. Microbial manipulation in mangrove-rhizosphere for regulating major energy metabolic pathways of methane could open-up a new window of climate change mitigation in coastal wetlands.

Net loss statistics underestimate carbon emissions from mangrove land use and land cover change

Converting mangroves to other land cover types can induce large emissions of carbon dioxide, depending on the type of land use and land cover (LULC) change. However, mangroves may also recover their ecosystem carbon stocks rapidly following restoration, potentially offsetting carbon stock losses. While studies have quantified these tradeoffs at global scales using coarse metrics, fewer studies have quantified them at national scales at higher resolution. Here, we used high‐resolution data sets of LULC for mangroves in Thailand to quantify district‐level gross and net changes in mangrove carbon stocks from ~1960 to 2014. We found emissions based on gross gain and loss statistics (7.18 ± 0.24 million Mg C) to be greater than those associated with emissions based on net area change statistics (1.65 ± 0.26 million Mg C) by a factor of four. The difference in estimates arises from slower rates of carbon stock recovery following reforestation relative to carbon stock loss following LULC change. Overall, we found the greatest gains in mangrove carbon stocks to be from mangrove expansion in areas of accreting sediments, which were strongly correlated with district‐level extent of undisturbed mangroves. Our results show that net loss statistics may greatly underestimate emissions associated with LULC change in mangroves. Additionally, our findings suggest that gains in mangrove carbon stocks associated with natural establishment at the periphery of standing mangroves may offset substantial carbon stock losses at national scales.

Carbon stock of disturbed and undisturbed mangrove ecosystems in Klang Straits, Malaysia

Ecosystem carbon stocks were compared in three island mangrove forests, subjected to different anthropogenic stresses, close to Port Klang in Selangor State on the west coast of Peninsular Malaysia. Carbon stocks in living biomass, litter, deadwood and soil were quantified, and the carbon isotopic signature in mangrove soils was also measured, to estimate their carbon source. We hypothesize that carbon stock would be more readily available in undisturbed mangroves. The results indicated that, in general, soil organic carbon pool comprised the majority of the ecosystem carbon stock, while dead organic matter made a negligible contribution. The highest ecosystem carbon stock was measured in the permanent undisturbed mangrove reserve on Pulau Klang. Carbon isotope data revealed that disturbed mangroves in Pulau Ketam had a more enriched δ13C signature of soil samples compared to the other two sites. The soil organic carbon in Pulau Ketam was mostly derived from mangrove materials (92.8%). The results suggested that the organic carbon accumulated in the soils was not only regulated by the burial of mangrove-derived organic carbon, but also the site conditions.

Impact of Shrimp Ponds on Mangrove Blue Carbon Stocks in Ecuador

Mangrove forests play an important role in mitigating climate change but are threatened by aquaculture expansion. The inclusion of mangroves in climate change mitigation strategies requires measuring of carbon stocks and the emissions caused by land use change over time. This study provides a synthesis of carbon stocks in mangrove and shrimp ponds in the Gulf of Guayaquil. In this study area, we identified 134,064 ha of mangrove forest and 153,950 ha of shrimp farms. Two mangrove strata were identified according to their height and basal area: medium-statured mangrove (lower height and basal area) and tall mangrove (greater height and basal area). These strata showed statistical differences in aboveground carbon stocks. In both strata, the most abundant mangrove species was Rhizophora mangle. For both strata, trees had a maximum height (>30 m), and their density was greater than 827 ha−1. Total ecosystem level carbon stocks (measured to 1 m soil depth) were 320.9 Mg C ha−1 in medium-statured mangroves and 419.4 Mg C ha−1 in tall mangroves. The differences are attributable to higher basal area, soil organic carbon concentrations and salinity, tidal range, origin of allochthonous material, and herbivory patterns. Mangrove soils represented >80% of the total ecosystem carbon. Ecosystem carbon stocks were lower (81.9 Mg C ha−1) in the shrimp farms, 50% less than in undisturbed mangroves. Our results highlight mangroves as tropical ecosystems with extremely high carbon storage; therefore, they play an important role in mitigating climate change. This research provides a better understanding of how carbon stocks in this gulf are found and can be used for design strategies to protect global natural carbon sinks.

Effects of fragmented mangroves on macrozoobenthos: a case study of mangrove clearance for powerline right-of-way at Oproama Creek, Niger Delta, Nigeria

Mangroves are vulnerable to varying magnitudes of degrading impact by human activities. Despite the many benefits of mangrove ecosystems, mangroves in the Niger Delta region are often cleared for electric powerline and oil pipeline rights-of-way, recreation, road construction, housing and farming. The study assessed the impacts of mangrove clearance on physico-chemical parameters of interstitial water and macrozoobenthic primary community structure in Oproama Creek, Nigeria, from February to July 2016. Three stations were selected for the study: two stations in more natural and undisturbed mangroves and one station at a mangrove clearing (for a national grid powerline right-of-way). Species richness and diversity were slightly higher at the undisturbed mangrove sites than the cleared site. Removal of mangrove canopy shade alters microclimate temperature regime and other temperature-dependent parameters, imposing thermal stress on stenothermal taxa and ancillary stressors that compositely affected primary community structure indices. Deliberate loss of mangroves through clearing waterfront vegetation as a driver for improved visual monitoring and enhanced security in the Oproama Community in the Niger Delta is reported for the first time. The wider implications of mangrove clearance and fragmentation on ecosystem-based goods and services are discussed. Limiting mangrove spatial loss owing to construction of an electric tower cutline within coastal landscape is strongly recommended.

The collapse of mangrove litterfall production following a climate-related forest loss in Brazil

Drought periods may change mangrove litterfall production through water deprivation and increasing tree evapotranspiration, but these impacts have been rarely estimated. In Brazil, an intense drought and strong winds impacted mangrove forests leading to mass tree mortality in 2016, suggesting that forest productivity also declined rapidly. Fifteen months after the initial impact, we started to monitor and quantify litterfall production in paired transects from disturbed and undisturbed mangroves. The litterfall production of the undisturbed forests (575 ± 28 Kg C ha−1 y−1) was 31- to 3-fold higher than that at the disturbed mangrove forests (18 to 169 Kg C ha−1 y−1). The strong decline in litterfall production may have implications to the export of nutrients to estuarine ecosystems. Our baseline suggests that mangrove forests are greatly vulnerable to climate impacts and that the litterfall production collapse in dead mangrove forests may impair marine ecosystem food webs.

Potential short wave attenuation function of disturbed mangroves

Mangroves are able to protect coastal communities through their ability to attenuate incoming long and short waves. Evidence of wave attenuation function and the factors contributing to wave attenuation by mangroves are now well established, especially for undisturbed mangrove stands. However, as tropical coastlines continue to urbanize rapidly, there is interest in understanding the ability of mangroves in wave attenuation along such disturbed coastlines. This study models the potential wave attenuation capacity of disturbed mangroves along the urban coastline of Singapore. Short wave attenuation is estimated under both average and storm (elevated water level) conditions. The percentage of wave height reduction is higher under storm events compared to average conditions. Vegetation drag is the main mechanism of wave energy dissipation under both average and storm conditions, with additional wave dissipation caused by wave breaking under the latter. Mangrove density and width were found to be positively correlated to the percentage of wave height reduction during a storm event. Compared to trunks and canopies, mangrove roots contributed to a larger percentage of wave height reduction. No statistical differences in wave height reduction extent were found between mangrove types, incident wave heights, and water levels respectively. This study has illustrated the potential for the attenuation of short waves by disturbed mangroves, especially during elevated water levels associated with storm events. The findings imply the potential of disturbed mangroves in wave attenuation, and should encourage the stronger incorporation of mangroves into coastal management strategies designed to protect urban communities against coastal hazards.

Mangrove blue carbon stocks and dynamics are controlled by hydrogeomorphic settings and land‐use change

Globally, carbon‐rich mangrove forests are deforested and degraded due to land‐use and land‐cover change (LULCC). The impact of mangrove deforestation on carbon emissions has been reported on a global scale; however, uncertainty remains at subnational scales due to geographical variability and field data limitations. We present an assessment of blue carbon storage at five mangrove sites across West Papua Province, Indonesia, a region that supports 10% of the world's mangrove area. The sites are representative of contrasting hydrogeomorphic settings and also capture change over a 25‐years LULCC chronosequence. Field‐based assessments were conducted across 255 plots covering undisturbed and LULCC‐affected mangroves (0‐, 5‐, 10‐, 15‐ and 25‐year‐old post‐harvest or regenerating forests as well as 15‐year‐old aquaculture ponds). Undisturbed mangroves stored total ecosystem carbon stocks of 182–2,730 (mean ± SD: 1,087 ± 584) Mg C/ha, with the large variation driven by hydrogeomorphic settings. The highest carbon stocks were found in estuarine interior (EI) mangroves, followed by open coast interior, open coast fringe and EI forests. Forest harvesting did not significantly affect soil carbon stocks, despite an elevated dead wood density relative to undisturbed forests, but it did remove nearly all live biomass. Aquaculture conversion removed 60% of soil carbon stock and 85% of live biomass carbon stock, relative to reference sites. By contrast, mangroves left to regenerate for more than 25 years reached the same level of biomass carbon compared to undisturbed forests, with annual biomass accumulation rates of 3.6 ± 1.1 Mg C ha−1 year−1. This study shows that hydrogeomorphic setting controls natural dynamics of mangrove blue carbon stocks, while long‐term land‐use changes affect carbon loss and gain to a substantial degree. Therefore, current land‐based climate policies must incorporate landscape and land‐use characteristics, and their related carbon management consequences, for more effective emissions reduction targets and restoration outcomes.

The effect of mangrove restoration on avian assemblages of a coastal lagoon in southern Mexico.

BackgroundMangrove forests provide many ecosystem services, including the provision of habitat that supports avian biodiversity. However, hurricanes can knock down trees, alter hydrologic connectivity, and affect avian habitat. In 1995, Hurricanes Opal and Roxanne destroyed approximately 1,700 ha of mangrove forest in Laguna de Términos, Mexico. Since then, hydrological restoration has been implemented to protect the mangrove forest and its biodiversity.MethodsSince avian communities are often considered biological indicators of ecosystem quality, avian diversity and species relative abundance were evaluated as indicators of mangrove restoration success by comparing undisturbed mangrove patches with those affected by the hurricanes. Using bird surveys, similarity analyses, and generalized linear models, we evaluated the effects of water quality variables and forest structure on the relative abundance and diversity of the avian community in disturbed, restored, and undisturbed mangrove patches.ResultsHigher bird species richness and relative abundances were found in disturbed and restored sites compared to the undisturbed site. After restoration, values of frequency of flooding, water temperature, tree density, and the number of tree species were more similar to that of the undisturbed site than to the values of the disturbed one. Such variables influenced the relative abundance of bird guilds in the different habitat conditions. Furthermore, some insectivorous bird species, such as the Yellow Warbler and Tropical Kingbird, were found to be similarly abundant in both undisturbed and restored sites, but absent or very low in occurrence at the disturbed site.ConclusionsCollectively, our results strongly suggest that hydrologic restoration helps to enhance niche availability for different bird guilds, including water and canopy bird species. Our work can help inform management strategies that benefit avian communities in mangrove forests and wetland systems.

Ecological impact of salt farming in mangroves on the habitat and food sources of Austruca occidentalis and Littoraria subvittata

The impact of salt farming on the habitats and food sources of Austruca occidentalis and Littoraria subvittata was studied in mangroves along the coast of Tanzania using stable isotopes (13C and 15N) and sediment particle size analysis. The 13C and 15N stable isotope composition in mangrove leaves, sediments and invertebrate tissues, were used to evaluate whether there are differences in feeding ecology of the crab Austruca occidentalis and the snail Littoraria subvittata collected from natural mangroves and mangroves around the salt ponds. Organic C, total N content and particle size distribution in sediments were used to assess if there are differences in habitat characteristics of mangroves around the salt ponds. Mangrove leaves and sediments were found to be 13C enriched around salt ponds compared to those from natural mangroves. Likewise the macroinvertebrates collected from mangroves around salt ponds were found be enriched in 13C relative to undisturbed mangroves. In addition, mangrove sediments around salt ponds were poorer in organic carbon and nitrogen and had more sand content compared to sediments from natural mangroves. These results indicate that salt pond activities have contributed to the modification of the habitats of macroinvertebrates by causing δ13C stable isotopes enrichment and alteration of sediment characteristics in the ecosystem.

Methane Emission from Mangrove Wetland Soils Is Marginal but Can Be Stimulated Significantly by Anthropogenic Activities

Mangrove wetland soils have been considered as important sources for atmospheric CH4, but the magnitude of CH4 efflux in mangrove wetlands and its relative contribution to climate warming compared to CO2 efflux remains controversial. In this study, we measured both CH4 and CO2 effluxes from mangrove soils during low or no tide periods at three tidal zones of two mangrove ecosystems in Southeastern China and collected CH4 efflux data from literature for 24 sites of mangrove wetlands worldwide. The CH4 efflux was highly variable among our field sites due to the heterogeneity of mangrove soil environments. On average, undisturbed mangrove sites have very low CH4 efflux rates (ranging from 0.65 to 14.18 μmol m−2 h−1; median 2.57 μmol m−2 h−1), often less than 10% of the global warming potentials (GWP) caused by the soil CO2 efflux from the same sites (ranging from 0.94 to 9.50 mmol m−2 h−1; median 3.67 mmol m−2 h−1), even after considering that CH4 has 28 times more GWP over CO2. Plant species, study site, tidal position, sampling time, and soil characteristics all had no significant effect on mangrove soil CH4 efflux. Combining our field measurement results and literature data, we demonstrated that the CH4 efflux from undisturbed mangrove soils was marginal in comparison with the CO2 efflux in most cases, but nutrient inputs from anthropogenic activities including nutrient run-off and aquaculture activities significantly increased CH4 efflux from mangrove soils. Therefore, CH4 efflux from mangrove wetlands is strongly influenced by anthropogenic activities, and future inventories of CH4 efflux from mangrove wetlands on a regional or global scale should consider this phenomenon.

A seasonal source and sink of nitrous oxide in mangroves: Insights from concentration, isotope, and isotopomer measurements

Mangrove forests can be a source or a sink of nitrous oxide (N2O) to the atmosphere, but seasonal mangrove N2O dynamics are not well understood. We used continuous high-resolution N2O concentration data to construct seasonal budgets of N2O in two tropical mangrove-lined creeks for both the wet and dry seasons. Furthermore we used N stable isotope analysis to constrain the pathways of N2O production and consumption within these creeks. Calculated water-air fluxes were within a range typical of undisturbed mangroves, however obvious seasonal differences in N2O dynamics were observed at the two sites. The mangrove systems were a net source of N2O to the atmosphere during the dry season and a net sink during the wet season. In the wet season we propose that increased allochthonous carbon enhances N2O consumption by denitrification. Combining the seasonal fluxes, the Fitzroy mangrove system, which received a continual input of allochthonous nitrate (NO3−), was a net source of N2O, while the Burdekin mangrove system was close to a net N2O balance. Interpreted in the context of DIN and N2O concentrations, the N2O isotopic values observed in the dry season point to fungal denitrification as the most likely pathway of N2O production. This study shows that subtle shifts in seasonal nutrient supply regulate mangrove N2O production and consumption.

Status of the undisturbed mangroves at Brunei Bay, East Malaysia: a preliminary assessment based on remote sensing and ground-truth observations.

Brunei Bay, which receives freshwater discharge from four major rivers, namely Limbang, Sundar, Weston and Menumbok, hosts a luxuriant mangrove cover in East Malaysia. However, this relatively undisturbed mangrove forest has been less scientifically explored, especially in terms of vegetation structure, ecosystem services and functioning, and land-use/cover changes. In the present study, mangrove areal extent together with species composition and distribution at the four notified estuaries was evaluated through remote sensing (Advanced Land Observation Satellite—ALOS) and ground-truth (Point-Centred Quarter Method—PCQM) observations. As of 2010, the total mangrove cover was found to be ca. 35,183.74 ha, of which Weston and Menumbok occupied more than two-folds (58%), followed by Sundar (27%) and Limbang (15%). The medium resolution ALOS data were efficient for mapping dominant mangrove species such as Nypa fruticans, Rhizophora apiculata, Sonneratia caseolaris, S. alba and Xylocarpus granatum in the vicinity (accuracy: 80%). The PCQM estimates found a higher basal area at Limbang and Menumbok—suggestive of more mature vegetation, compared to Sundar and Weston. Mangrove stand structural complexity (derived from the complexity index) was also high in the order of Limbang > Menumbok > Sundar > Weston and supporting the perspective of less/undisturbed vegetation at two former locations. Both remote sensing and ground-truth observations have complementarily represented the distribution of Sonneratia spp. as pioneer vegetation at shallow river mouths, N. fruticans in the areas of strong freshwater discharge, R. apiculata in the areas of strong neritic incursion and X. granatum at interior/elevated grounds. The results from this study would be able to serve as strong baseline data for future mangrove investigations at Brunei Bay, including for monitoring and management purposes locally at present.

Distribution of Mangrove Species in the Islands of Jaffna Peninsula, Sri Lanka

Mangroves are a group of halophytic, evergreen, woody plants and shrubs that occupy the intertidal zone. The Jaffna peninsula has some of the major mangrove sites in Sri Lanka with large extents of undisturbed mangroves. As a result of the three-decade long armed conflict that prevailed in the entire northern part of the Island, mangrove diversity and distribution has never been evaluated since 1969. The objective of the present study was to identify the mangrove species and their distribution in the Jaffna peninsula. Five locations were selected based on the distribution of mangrove vegetation. These are Mandaitivu (East and West), Sirudivu, Kuruchidivu, Kurikadduwan, and Kaluthaipiddi. Random quadrat method was used to assess the abundance of mangrove species in the area. A total of 21 species of true mangrove plants have been recorded in Sri Lanka and the present study identified seven (07) species in the Jaffna peninsula. These are Bruguiera cylindrica, Avicennia marina, Avicennia officinalis, Rhizophora mucronata, Excoecaria agallocha, Lumnitzera racemosa, and Ceriops tagal. A mangrove associate, Acanthus ilicifolius was also recorded. Of these, Bruguiera cylindrica is a species with restricted distribution. In the present study it was recorded only from Sirudivu (density 169/km2). Avicennia marina is the dominant species on the Islands and Southern coastal line. The island of Mandaitivu had a high density of this species (293/km2 on East and 1208/km2 on West Mandaitivu). Kuruchidivu also had a higher density (2571/km2) of this species compared to other island areas. Avicennia officinalis was restricted to Sirudivu and Kuruchidivu (density 246/km2 and 100/km2 respectively). Mangroves are one of the most diverse ecosystems and they provide suitable habitats for a large number of migratory bird species and other aquatic species such as fishes, shrimps, crabs, etc. which are important to marine fisheries in Sri Lanka. They are one of the most productive ecosystems on the earth. The mangroves also protect the coasts from the impacts of storms. The study area has large extents of relatively undisturbed mangroves, found mainly on the Eastern side of the Jaffna peninsula along with the lagoon line and the Southern part of the peninsula along the coastal line. Hence the present area has a considerable conservation value. Keywords: True mangroves, Mangrove associates, Distribution, Islands, Jaffna Peninsula

Comparison of Water Quality Status of Disturbed and Undisturbed Mangrove Forest at Awat-Awat Lawas Sarawak

Water quality testing was compulsory for management of safe and reliable water sources. Various sources of pollution and destruction of mangrove forest decrease the quality of river water. Thus a study was conducted to determine the water quality status of mangrove forest river water of Awat-Awat Lawas Sarawak and compare the water quality status of disturbed and undisturbed mangrove forest river in that area. Samples from twelve sampling stations were collected from both mangrove forest river from October 2013 to March 2014. In-situ data collected (pH, temperature, dissolved oxygen (DO), salinity, turbidity, total dissolved solid (TDS), conductivity) and laboratory analysis (biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (AN), total suspended solid (TSS)) were conducted according to the Standard method of Examination of Water and Wastewater AHPA 2005. Six water parameters: pH, DO, BOD, COD, AN and TSS value were used in calculating the Water Quality Index (WQI). Mean values for disturbed area were follows, pH (7.07), temperature (29.93°C), salinity (15.64 PSU), turbidity (55.13 NTU), DO (4.59 mg/L), BOD (0.73 mg/L), COD (10.16 mg/L), AN (0.14 mg/L), TSS (53.92 mg/L), TDS (23.14 mg/L) and conductivity (2.61 ms/m). Undisturbed area results were, pH (6.84), temperature (28.32°C), salinity (14.65 PSU), turbidity (35.41 NTU), DO (2.39 mg/L), BOD (0.55 mg/L), COD (15.82 mg/L), AN (0.13 mg/L), TSS (53.23 mg/L), TDS (22.82 mg/L) and conductivity (2.34 ms/m). There were no significant differences between two locations except for DO. Both water qualities of disturbed and undisturbed mangrove forest river were found under Class III, which describe that the water bodies are in moderate quality status.

Rare Earth Elements As Biogeochemical Indicators In Mangrove Ecosystems (Pichavaram, Tamilnadu, India)

Abstract Mangrove forests are coastal wetland that can be sinks for material derived from terrestrial and marine settings. This study aims to establish the abundance, distribution, and enrichment of rare earth elements (REE) to track the sediment sources and infer biogeochemical processes occurring in the mangrove wetlands. Five sediment cores were collected throughout the Pichavaram mangroves in November 2010. The sampling sites were chosen based on vegetation cover, land-use pattern, and human interference. The vertical profile of the retrieved sediment cores were sub-sectioned, air dried, and homogenized into a powder before analysis. Higher REE concentration in Pichavaram sediments indicates dominance of input from the natural sources like weathering. Preferential REE enrichment was attributed to the alkaline pH (7–8.5) and reducing conditions prevailing in the mangrove environment allowing removal of MREE and LREE by adsorption and precipitation as Fe-Mn oxyhydroxides in sediments. Post Archean Australian Shale (PAAS)-normalized plots depicted convex subparallel shale-like patterns with similar enrichment. Pichavaram sediments showed strongly positive Eu anomalies, similar to that observed in Kaveri River sediments, validating the origin of REE in Pichavaram sediments as an outcome of natural weathering of post-Archean charnockitic and gneissic terrane. Also positive Eu anomalies indicated the prevalence of reducing conditions in Pichavaram. Cores near the estuarine mouth showed highly mixed vertical profile as compared to the undisturbed mangrove sites. Principal-component analysis delineated three main processes controlling REE distribution in Pichavaram, namely natural weathering, inherent physicochemical processes, and in situ biogeochemical processes occurring in this mangrove environment.

Elevated rates of organic carbon, nitrogen, and phosphorus accumulation in a highly impacted mangrove wetland

The effect of nutrient enrichment on mangrove sediment accretion and carbon accumulation rates is poorly understood. Here we quantify sediment accretion through radionuclide tracers to determine organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) accumulation rates during the previous 60 years in both a nutrient-enriched and a pristine mangrove forest within the same geomorphological region of southeastern Brazil. The forest receiving high nutrient loads has accumulated OC, TN, and TP at rates that are fourfold, twofold, and eightfold respectively, higher than those from the undisturbed mangrove. Organic carbon and TN stable isotopes (δ13C and δ15N) reflect an increased presence of organic matter (OM) originating with either phytoplankton, benthic algae, or another allochthonous source within the more rapidly accumulated sediments of the impacted mangrove. This suggests that the accumulation rate of OM in eutrophic mangrove systems may be enhanced through the addition of autochthonous and allochthonous nonmangrove material.