Sundarbans Research Articles

Bangladesh Sundarbans: Present Status of the Environment and Biota

Bangladesh Sundarbans: Present Status of the Environment and Biota

Mangroves in India: A Unique Marine Ecosystem

India has a long tradition of mangrove forest management. The Sundarbans mangroves, located in the Bay of Bengal (partly in India and partly in Bangladesh), were the first mangroves in the world to be put under scientific management. The area's first management plan was implemented in 1892. Recognizing the importance of mangroves, the Government of India set up the National Mangrove Committee in the Ministry of Environment and Forests in 1976 to advise the government about mangrove conservation and development. In its first meeting, the panel, which consists of scientists, research scholars and experts on the mangrove ecosystem, emphasized the need to conduct a survey of the extent of existing mangrove areas within the country.

Mangroves in India: A Unique Marine Ecosystem

India has a long tradition of mangrove forest management. The Sundarbans mangroves, located in the Bay of Bengal (partly in India and partly in Bangladesh), were the first mangroves in the world to be put under scientific management. The area's first management plan was implemented in 1892. Recognizing the importance of mangroves, the Government of India set up the National Mangrove Committee in the Ministry of Environment and Forests in 1976 to advise the government about mangrove conservation and development. In its first meeting, the panel, which consists of scientists, research scholars and experts on the mangrove ecosystem, emphasized the need to conduct a survey of the extent of existing mangrove areas within the country.

An annotated checklist of the vascular plants of Sundarban Mangrove Forest of Bangladesh

The study revealed the occurrence of 528 species of vascular plants belonging to 356 genera and 111 families in the Sundarban Mangrove Forest of Bangladesh. Among these species, 24 were pteridophytes and the rest were angiosperms, of which only 24 were true mangroves and 70 were mangrove associates. Magnoliopsida and Liliopsida were represented by 373 and 131 species, respectively. These species belonged to 345 herbs, 89 shrubs and 94 trees. Sixty-four species were climbers, 14 were epiphytes, 6 were parasites, and 7 were palms. The species number per family varied from 1 to 42. In pteridophytes, Pteridaceae with 4 genera and 5 species was the largest family. In angiosperms, Fabaceae with 24 genera and 42 species and Poaceae with 27 genera and 42 species were the largest families, respectively, in Magnoliopsida and Liliopsida. Most of the species included in this checklist were found in oligohaline zone, Sarankhola range and the forest margins, and recognized as economically important. Eleven species categorized as threatened in Bangladesh were found to occur in this mangrove forest.Bangladesh J. Plant Taxon. 22(1): 17–41, 2015 (June)

Natural and traditional defense mechanisms to reduce climate risks in coastal zones of Bangladesh

Substantially resourceful and densely populated coastal zones of Bangladesh experience numerous extreme events linked to hydro-meteorological processes viz. cyclones, tidal surges, floods, salinity intrusion and erosion etc. These hazards give rise to extensive damage to property and loss of lives every year. Further, anthropogenic activities in the coastal zones are accentuating environmental degradation causing widespread suffering. Cyclones and tornadoes in particular damage infrastructures and crops every year affecting the economy of the country negatively. Some naturally adapted plants as well as landscapes usually reduce the speed of cyclones and tornadoes and thus, protect the coastal zones. However, human activities have destroyed many of the forests and landscapes. Sundarbans and Chokoria Sundarbans mangrove forests of Bangladesh are under a great threat of extinction due to illicit logging and agricultural expansion. At least 34 plant species of tropical forest are on the verge of extinction. Many animals e.g., cats, bears, porcupines, wild boars, pythons and anteaters are in the process of being wiped out from the coastal areas. Among the marine and coastal species, Red crabs, jelly-fish, sharks, and dolphins are also rare but these were the major species prior to 1980s. This study revealed that during the recent decades there has been massive plantations and construction of embankment and polderization but these and other measures have been found to be impractical and ineffective in reducing disasters in coastal areas. There is a need for integration of traditional coping practices and wisdoms with modern approaches. Available knowledge on some of these traditional practices has been documented for establishing a sustainable policy for management of coastal zones of Bangladesh. By combining traditional and scientific management of coastal ecosystem with mangroves and other plants following triple-tier mechanism and habitat, it is possible to reduce the effects of natural and climate change-induced disasters. Under such a management system, the entire coastal zone can be made more productive and sustainable.

Thalassiosira sundarbana sp. nov. (Bacillariophyta), an estuarine diatom from Sundarbans mangrove ecoregion based on morphology and molecular phylogeny

SummaryA new species of diatom, Thalassiosira sundarbana, is described based on light and scanning electron microscopy along with molecular phylogeny. The specimen was collected from Chemaguri creek of the Indian part of Sundarbans mangroves, and subsequently a clonal culture was established. Thalassiosira sundarbana possess variable numbers of occluded processes, and one labiate process on the valve face. Valve margin is ribbed and areolae are fasciculated on the valve face. Two rings of strutted processes are present on valve face. Strutted processes are also scattered on the valve face apart from the presence of two rings. Valvocopula and copula have rows of pore, and pleurae are hyaline. Bayesian analyses of nuclear encoded small subunit (SSU) rDNA and plastid encoded rbcL gene confirmed that T. sundarbana is phylogenetically novel. Salinity tolerance experiment with the clonal culture of T. sundarbana showed that this isolate can grow in salinity ranging from 10–35 psu. The maximum growth rate was observed in 15 psu salinity (0.5 divisions 24 h−1). On the basis of morphological features and molecular phylogeny, this clonal isolate is considered as a new estuarine species of Thalassiosira.

Spatial distribution and population structure of fiddler crabs in an Indian Sundarban mangrove

Brachyuran crabs constitute the most abundant faunal component of mangrove ecosystems and support a wide range of ecosystem services. In the present study, seasonal variation of population density and biomass along with demographic categories and sex ratios of four species of fiddler crabs (Uca rosea, Uca triangularis, Uca dussumieri and Uca vocans) from Jhorkhali Island in the Sundarban mangrove were studied in relation to some major environmental parameters (salinity, nutrient content, soil organic carbon, dissolved oxygen, total dissolved solute, etc.) during bimonthly sampling for three consecutive years (2010-2012). Maximum population density and biomass of the ocypodid crabs were recorded during the pre-monsoonal month and minimum values during the monsoon. Different peaks in reproductive activity were observed among seasonal breeders (U. triangularis, U. dussumieri). For U. vocans, the sex ratio peaks declined during the ovigerous period. All four populations were characterized by significantly more males than females. Multiple regression analysis suggested a cumulative effect of several ecological parameters on seasonal fluctuations of the crab population. Breeding periodicity might be controlled by a combination of factors, including temperature, quality of the substratum, food availability for the adult and larval stages, and intertidal zonations.

An empirical analysis of conservation practices, management and sustainability in the Sundarbans Mangrove Forest, Bangladesh

This article examines the factors that influence conservation practices in the world's largest mangrove forest, the Sundarbans in Bangladesh. It explores the relationship between tree density reductions and management practices. 412 households in forest-dependent communities (FDCs) were interviewed. Their overwhelming view is that the Sundarbans is being over exploited through overharvesting. Results show that FDCs who engage in resource harvesting under the current property rights regime have less participation in and lower motivation for the conservation of forest resources. Current management by the forest department results in lower commitment by the community to conservation. Conservation of resources could be achieved by the allocation of expanded property rights to give management roles to communities. With the granting of these rights they would engage in conservation practices. The results suggest that constructing effective strategies to promote mangrove conservation require these two factors to be addressed to achieve sustainable forest management.

Economic Assessment for Harvesting Artisanal Giant Freshwater Prawn from the Sundarban Mangrove Ecosystem in Bangladesh

Harvesting Giant Freshwater Prawn, Golda (Macrobrachium rosenbergii de Man 1879) in the Sundarnbans mangrove forest plays an important role in the economy of the country as well as the livelihood of local community. The study focused the economic assessment of small-scale artisanal Golda fishery. Overall the Hookline gear showed the best performance in terms of economic return. However, it was found to withstand a shock from 20% decrease in market prices or 30% fall in catch rate in terms of Return on investment, payback period and Benefit-cost ratio. Operating cost and fixed cost for Hookline fishery was the lowest and Khathijal was the highest. No significant variation (P<0.05) observed in the mean catch rate per trip boat-1 among the gears studied. Total revenue earned after completion a trip varied considerably between BDT 1,307 to 1,562. Yearly, total net revenue reached at the maximum by Hookline (BDT 38,506), followed by Chandijal (BDT 38,377) and the minimum by Khalpata (BDT 33,885). The findings of this study are supposed to be helpful for policy makers in improving the current status of Golda fishery and relevant human livelihood as well as conserving the Sundarbans Mangrove Ecosystem.

Arylamine N-acetyl Transferase (NAT) in the blue secretion of Telescopium telescopium: xenobiotic metabolizing enzyme as a biomarker for detection of environmental pollution.

Telescopium telescopium, a marine mollusc collected from Sundarban mangrove, belongs to the largest mollusca phylum in the world and exudes a blue secretion when stimulated mechanically. The blue secretion was found to metabolize (preferentially) para-amino benzoic acid, a substrate for N-acetyl transferase (NAT), thereby indicating acetyl transferase like activity of the secretion. Attempts were also made to characterise bioactive fraction of the blue secretion and to further use this as a biomarker for monitoring of marine pollution. NAT like enzyme from marine mollusc is a potential candidate for detoxification of different harmful chemicals. A partially purified extract of blue secretion was obtained by fractional precipitation with (NH4)2SO4. From different fractions obtained by precipitation, the 0–30% fraction (30S) displayed NAT like activity (using para amino benzoic acid as a substrate with para nitrophenyl phosphate or acetyl coenzyme A as acetyl group donors). Maximum NAT like enzyme activity was attained at 25°C and at a pH of 6. The enzyme activity was found to be inhibited by 5 mM phenyl methyl sulfonyl fluoride. The divalent metal ions reduced NAT like activity of 30S. Moreover, Cu2+ and Zn2+ (at concentration of 1 mM) completely inhibited NAT activity. The thermal stability and bench-top stability studies were performed and it was found that the enzyme was stable at room temperature for more than 24 hours. Results from the present study further indicate that heavy metal content in blue secretion gradually decreased from pre-monsoon to post-monsoon season, which also corresponded to the change in NAT like activity. Therefore, this article stresses the importance of biomarker research for monitoring pollution.

Spatiotemporal analysis of bacterial diversity in sediments of Sundarbans using parallel 16S rRNA gene tag sequencing.

The influence of temporal and spatial variations on the microbial community composition was assessed in the unique coastal mangrove of Sundarbans using parallel 16S rRNA gene pyrosequencing. The total sediment DNA was extracted and subjected to the 16S rRNA gene pyrosequencing, which resulted in 117Mbp of data from three experimental stations. The taxonomic analysis of the pyrosequencing data was grouped into 24 different phyla. In general, Proteobacteria were the most dominant phyla with predominance of Deltaproteobacteria, Alphaproteobacteria, and Gammaproteobacteria within the sediments. Besides Proteobacteria, there are a number of sequences affiliated to the following major phyla detected in all three stations in both the sampling seasons: Actinobacteria, Bacteroidetes, Planctomycetes, Acidobacteria, Chloroflexi, Cyanobacteria, Nitrospira, and Firmicutes. Further taxonomic analysis revealed abundance of micro-aerophilic and anaerobic microbial population in the surface layers, suggesting anaerobic nature of the sediments in Sundarbans. The results of this study add valuable information about the composition of microbial communities in Sundarbans mangrove and shed light on possible transformations promoted by bacterial communities in the sediments.

Temporal changes in brachyuran crab diversity along heterogeneous habitat in a mangrove ecosystem of Indian Sundarbans

The present study investigates the effect of different habitat attributes on brachyuran crab diversity in two different study sites in the Sundarban mangrove, India. The two sites differ in the level of anthropogenic intrusion and in the age of the mangrove forest. Seasonal changes in the environment and in brachyuran faunal abundance were recorded for three years. Species composition varied between the two habitats irrespective of season. The habitat heterogeneity and the recorded crab community was analysed by several univariate and multivariate statistical techniques. The newly replanted mangrove site showed lesser diversity than the natural one. Ocypodid crabs, mainly Uca rosea , dominated both study sites, whereas Uca triangularis was totally absent from the replanted site. Canonical correspondence analysis showed that the total acidity, total alkalinity, pH content of water, total dissolved solids, inorganic phosphate content of water, soil specific gravity, soil density and the physical constructions of the habitat play a crucial role in moderating the crab community structure. This study reveals that brachyuran crab diversity can be used as a potential indicator of the alterations of mangrove habitats.

Vertical Profile of Phosphatase Activity in the Sundarban Mangrove Forest, North East Coast of Bay of Bengal, India

Impact of phosphate solubilizing bacteria along with soil phosphatase activity on phosphorous cycle was found to be quiet interesting in the Sundarban mangrove ecosystem. Soil phosphatase activity showed a decreasing pattern with increase in depth [soil phosphatase activity (μg pnp produced g−1 dry wt of soil) = 906.85 – 5.6316 Depth (cm)] from the deep forest region of the Sundarban forest ecosystem. Soil salinity showed a very little effect on soil phosphatase activity whereas soil temperature and pH was found to show significant impact on the soil phosphatase activity. This ensured that the microbes associated with phosphate mineralization present in the Sundarban forest ecosystem are more tolerant to fluctuation in salinity than that of temperature and pH. A direct correlation was perceptible between the number of phosphate solubilizing bacteria and phosphatase activity in the soil during the study period from 2007 to 2012. Soil phosphate concentration was found to be directly governed by the soil phosphatase activity [The regression equation is: avg PO4−3-P (μg g−1 dry wt of soil) = 0.0311 + 0.000606 soil phosphatase activity (μg pnp produced g−1 dry wt of soil); R2 = 63.2%, p < 0.001, n = 62].

Can the Sublime Be Postcolonial? Aesthetics, Politics, and Environment in Amitav Ghosh’sThe Hungry Tide

AbstractSet in the vast Sundarban mangrove forest of Bangladesh in the shadow of the colonial past and the 1979 Morichjhapi massacre,The Hungry Tidetraces the transformation of three metropolitan characters from disengaged spectators to invested insiders. The novel may be read as elaborating the theories of Jean-François Lyotard, whose revision of the sublime as the “differend” in both aesthetics and politics provides a compelling context for exploring the postcolonial sublime. Suggesting ecocentric ways of engaging the world that loosen the bonds of the colonial past and critiquing the failure of the postcolonial state and the new cosmopolitanism, Ghosh rewrites aesthetics as interconnected with ethics and politics. In his novel, the postcolonial sublime no longer reifies metaphysical or anthropocentric pure reason, but instead enables discovery of our interpenetration with the natural world, spurring us to witnessing and activism in partnership with those who have been rendered silent and invisible.

Eddy covariance based methane flux in Sundarbans mangroves, India

We report the initial results of the methane flux measured using eddy covariance method during summer months from the world’s largest mangrove ecosystem, Sundarbans of India. Mangrove ecosystems are known sources for methane (CH4) having very high global warming potential. In order to quantify the methane flux in mangroves, an eddy covariance flux tower was recently erected in the largest unpolluted and undisturbed mangrove ecosystem in Sundarbans (India). The tower is equipped with eddy covariance flux tower instruments to continuously measure methane fluxes besides the mass and energy fluxes. This paper presents the preliminary results of methane flux variations during summer months (i.e., April and May 2012) in Sundarbans mangrove ecosystem. The mean concentrations of CH4 emission over the study period was 1682 ± 956 ppb. The measured CH4 fluxes computed from eddy covariance technique showed that the study area acts as a net source for CH4 with daily mean flux of 150.22 ± 248.87 mg m−2 day−1. The methane emission as well as its flux showed very high variability diurnally. Though the environmental conditions controlling methane emission is not yet fully understood, an attempt has been made in the present study to analyse the relationships of methane efflux with tidal activity. This present study is part of Indian Space Research Organisation–Geosphere Biosphere Program (ISRO–GBP) initiative under ‘National Carbon Project’.

A study on abundance and distribution of mangrove species in Indian Sundarban using remote sensing technique

Conservation and management of Sundarban mangrove forest is difficult chiefly due to inaccessibility and hostile condition. Remote sensing serves as an important tool to provide up-to date baseline information which is the primary requirement for the conservation planning of mangroves. In this study, supervised classification by maximum likelihood classifier (MLC) has been used to classify LANDSAT TM and LANDSAT ETM satellite data. This algorithm is used for computing likelihood of unknown measurement vector belonging to unknown classes based on Bayesian equation. Image spectra for various mangrove species were also generated from hyperspectral image. During field visits, GPS locations of five dominant mangrove species with appreciable distribution were taken and image spectra were generated for the same points from hyperion image. The result of this classification shows that, in 1999 total mangrove forest accounted for 55.01 % of the study area which has been reduced to 50.63 % in the year 2010. Avicennia sp. is found as most dominating species followed by Excoecaria sp. and Phoenix sp. but the aerial distribution of Avicennia sp., Bruguiera sp. and Ceriops sp. has reduced. In this classification technique the overall accuracy and Kappa value for 1999 and 2010 are 80 % and 0.77, 85.71 % and 0.81 respectively.

Biogeochemical cycle of nitrogen in a tropical mangrove ecosystem, east coast of India

Like many coastal systems, nitrogen is the critical limiting factor for mangrove net production. This study used a box model approach to assess the nitrogen budget in the Sundarban mangrove ecosystem, which acts as a sink for atmospheric nitrogen in terms of NOx, NH3, N2, and water column dissolved inorganic nitrogen. The coupling of biosphere and atmosphere in terms of atmospheric NOx and NH3 uptake showed that uptake of ammonia (130×106molyr−1) was about six fold as large as that of NOx, (22×106molyr−1). The nitrogen stored by the processes such as plant uptake of NOx, NH3 from the atmosphere, nitrogen fixation (5×109molyr−1), and sediment water exchange (8×106molyr−1) was about two times as large as that of recycled nitrogen from litter (3×109molyr−1), and could account 74% of the nitrogen required for mangrove net production. Most of the nitrogen was conserved in the living biomass (living biomass: 118×103molha−1 versus soil: 3×103molha−1). The loss of nitrogen was 23% of the total amount that was conserved from the external sources in the Sundarban mangrove system. Thus, the coastal ecosystem like Sundarban mangroves could retain only 0.2% (8×106mol) of the annual river flux of nitrogen to the coastal waters and nitrogen is generally conserved within the system.

Quantitative Study of As (V) and As (III) Interaction with Mangrove DNA by Molecular Fluorescence Spectroscopy

This study describes the in vitro study of (1:1) one step nucleophilic displacement ([Formula: see text]) of phosphate by heavier anion arsenate and arsenite in the DNA of arsenic ridden Sundarban mangroves. Mangrove DNA was found to give rise to a broad fluorescence and its integrated fluorescence intensity was enhanced on addition of As (V) and As (III), respectively. Analyses of the fluorescence parameter showed adequacy of 1:1 model to describe substitution of phosphate of mangrove DNA chain exiplex by arsenate and arsenite with equilibrium constant (log Kc) ranging between 4.19 and 4.32 for As (V), and between 3.77 and 3.89 for As (III) at pH 7 and 25°C. In the cases, the melting temperature (Tm) and reassociation rate constant of mangrove DNA was increased on treatment with As (V) and As (III). It is suggested that heavier ion arsenate and arsenite may substitute phosphate in natural DNA.

Analysis of Relationship between Salinity and Top-Dying Diseases of Sundri Trees in Sundarbans, Bangladesh

At the advent of British rule in 1765, the Sundarbans forests were double their present size (Seidensticker, and Hai, 1983; Khan, 1997). Sundarbans mangroves in Asia including Bangladesh, India, and East Africa previously contained a much fuller range of species (Seidensticker, and Hai, 1983; Khan, 1997). In the Southeast Asian region, species diversity of mangroves was previously much higher (Ellison, 1998, 2000). Although, a particular class of men made a profession of collection of wood, fish, Golpata, Goran, natural beauty, oil, honey, and wax in Sundarbans (Awal, 2007), but it is facing tremendous problems (Awal, 207, 2009, 2014). But, it is now under serious threatened through human destruction, and by ecological pollution (Awal, 2007). The cause of this dieback is still not well understood unknown. The present work has investigated one of the possible factors that might be causing this top-dying, namely the concentrations of various chemical elements present in the sediments, particularly Salinity (Na), Exchangeable K, heavy metals, though other chemical parameters such as the pH, salinity, moisture content of the sediment and nutrient status were also assessed. (Awal, 2007). Na has no relationship with the amount of top-dying of Sundri trees in Sundarbans. However, a serious killer disease (top dying) of H. fomes in Sundarbans is affecting millions of the trees (Awal, 2007). The loss of H. fomes will have a major impact on the Sundarbans mangrove ecosystem, as well as lead to economic losses. A questionnaire survey was conducted among different groups of people inside and outside of Sundarbans to explore local perceptions as to the possible causes of top dying. This confirmed the increase in top-dying prevalence (Awal, 2007). Most of the elements including Salinity of soil and water studied had no significant correlation with the top dying of Heritiera fomes. However, Sn, Exchangeable K, and soil pH were significantly related, and three elements, namely Pb, Zn, Ni, were also close to significance. Sn concentration is negatively associated with top dying. Soil pH varied significantly in the different plots. Exchangeable K was positively associated with the tree diameter whether the top dying was severe or mild.

Analysis of Effluent Discharge in to Natural Forest in Bangladesh

Natural forest resources like Sundarbans mangroves in Asia including Bangladesh, India, and East Africa previously contained a much fuller range of species (Seidensticker, and Hai, 1983; Khan, 1997). In the Southeast Asian region, species diversity of mangroves was previously much higher, where approximately two-thirds of all species and 70% of the major vegetation types with 15% of terrestrial species in the Bangladesh-India-Malayan realm have already been destroyed (Ellison, 1998, 2000). Despite this designation, this natural forest resources (Sundarbans) in Bangladesh has been facing tremendous problems, including that of dieback (top-dying), shrimp farming, human destructions, deforestations, illicit fellings, miss-management of the main tree species (Heritiera fomes) which is affecting millions of trees (Awal, 2007). The cause of this dieback is still not well understood unknown. The present work has investigated one of the possible factors that might be causing this top-dying, namely the concentrations of various chemical elements present in the sediments, particularly heavy metals, though other chemical parameters such as the pH, salinity, moisture content of the sediment and nutrient status were also assessed. A questionnaire survey was conducted among different groups of people inside and outside of Sundarbans to explore local perceptions as to the possible causes of top dying. This confirmed the increase in top-dying prevalence (Awal, 2007). Despite various hypotheses as to the causes of this top-dying, the underlying causes are still not well understood. The present work has explored some of the possible factors involved, focusing particularly on the relationship between the amount of top-dying in different places and the concentrations of a number of chemical elements present in the soil and water, in order to test the hypothesis that chemical pollution might be responsible. Other factors such as the pH, salinity and nutrient status were also assessed. The vegetation structure was assessed in terms of tree height, bole diameter, species present, and regeneration status; and the intensity of top-dying within the plots was recorded on a rank scale. Most of the elements studied had no significant correlation with the top dying of Heritiera fomes. However, Sn, Exchangeable K, and soil pH were significantly related, and three elements, namely Pb, Zn, Ni, were also close to significance. Sn concentration is negatively associated with top dying. Soil pH varied significantly in the different plots. Exchangeable K was positively associated with the tree diameter whether the top dying was severe or mild (Awal, 2007).