Sundarbans Mangrove Forest Research Articles

Characterizing air–sea CO2 exchange dynamics during winter in the coastal water off the Hugli-Matla estuarine system in the northern Bay of Bengal, India

The distribution of the fugacity of CO2 (fCO2) and air-sea CO2 exchange were comprehensively investigated in the outer estuary to offshore shallow water region (lying adjacent to the Sundarban mangrove forest) covering an area of *2,000 km 2 in the northern Bay of Bengal during the winter. A total of ten sampling surveys were conducted between 1 December, 2011 and 21 February, 2012. Physico- chemical variables like sea surface temperature (SST), salinity, pH, total alkalinity (TAlk), dissolved inorganic carbon (DIC) and in vivo chlorophyll-a along with atmo- spheric variables were measured in order to study their role in controlling the CO2 flux. Surface water fCO2 ranged between 111 and 459 latm which correlated significantly with the SST (r = 0.71, p \ 0.001, n = 62). Neither DIC nor TAlk showed any linear relationship with varying salinity in the estuarine mixing zone, demonstrating the significant pre- sence of non-carbonate alkalinity. An overall net biological control on the surface fCO2 distribution was established during the study, although no significant correlation was found between chlorophyll-a and fCO2 (water). The shallow water region studied was mostly under-saturated with CO2 and acted as a sink for atmospheric CO2. The difference between surface water and atmospheric fCO2 (DfCO2) ranged from -274 to 69 latm, with an average seaward flux of - 10.5 ± 12.6 lmol m -2 h -1 . The DfCO2 and hence the air- sea CO2 exchange was primarily regulated by the variation in sea surface fCO2, since atmospheric fCO2 varied over a com- paratively narrow range of 361.23-399.05 latm.

Clicking in Shallow Rivers: Short-Range Echolocation of Irrawaddy and Ganges River Dolphins in a Shallow, Acoustically Complex Habitat

Toothed whales (Cetacea, odontoceti) use biosonar to navigate their environment and to find and catch prey. All studied toothed whale species have evolved highly directional, high-amplitude ultrasonic clicks suited for long-range echolocation of prey in open water. Little is known about the biosonar signals of toothed whale species inhabiting freshwater habitats such as endangered river dolphins. To address the evolutionary pressures shaping the echolocation signal parameters of non-marine toothed whales, we investigated the biosonar source parameters of Ganges river dolphins (Platanista gangetica gangetica) and Irrawaddy dolphins (Orcaella brevirostris) within the river systems of the Sundarban mangrove forest. Both Ganges and Irrawaddy dolphins produced echolocation clicks with a high repetition rate and low source level compared to marine species. Irrawaddy dolphins, inhabiting coastal and riverine habitats, produced a mean source level of 195 dB (max 203 dB) re 1 µPapp whereas Ganges river dolphins, living exclusively upriver, produced a mean source level of 184 dB (max 191) re 1 µPapp. These source levels are 1–2 orders of magnitude lower than those of similar sized marine delphinids and may reflect an adaptation to a shallow, acoustically complex freshwater habitat with high reverberation and acoustic clutter. The centroid frequency of Ganges river dolphin clicks are an octave lower than predicted from scaling, but with an estimated beamwidth comparable to that of porpoises. The unique bony maxillary crests found in the Platanista forehead may help achieve a higher directionality than expected using clicks nearly an octave lower than similar sized odontocetes.

Community perceptions of state forest ownership and management: A case study of the Sundarbans Mangrove Forest in Bangladesh

The Sundarbans Mangrove Forest (SMF) is the world's largest mangrove forest and it provides livelihoods to 3.5 million forest-dependent people in coastal Bangladesh. The first study aim was to analyse the efficacy of the state property regime in managing the forest through a close examination of the relationship between property rights and mangrove conservation practices. The second study aim was to explore forest-dependent communities' (FDCs) perceptions about their participation in management and conservation practices. The Schlager and Ostrom theoretical framework was adopted to examine the role of potential ownership variations in a common property resource regime. A survey of 412 FDC households was undertaken. Current management by the Bangladesh Forest Department (BFD) does not result in implementation of mandated mangrove conservation practices. It was found that allocation of property rights to FDCs would be expected to increase conservation practices. 92% of respondents expressed the view that the evidenced rapid degradation over the past 30 years was due primarily to corruption in the BFD. About half of FDCs (46%) surveyed are willing to participate in mangrove conservation through involvement in management as proprietors. Consistent with Schlager and Ostrom's theory, the results indicate the necessity for de facto and de jure ownership and management change from a state to common property regime to ensure FDCs' participation in conservation practices.

Natural resources, livelihoods, and reserve management: a case study from sundarbans mangrove forests, bangladesh

The Sundarbans Reserved Forest, and its surrounding buffer zone, is one of the most diverse and richest areas of natural resource in Bangladesh. It is a part of the largest mangrove forest in the world, with an area of about 10,000 km², of which 6,000 km² are in Bangladesh and about 4,000 km² are part of India: it has been recognized as an internationally important World Heritage and Ramsar site. The mangroves provide substantial ecosystem services supporting the livelihood of local communities. This paper describes the diverse uses of these natural resources and aims to evaluate the contribution of ecosystem services to the livelihood of residents. The results indicate that residents depend on ecosystem services in two ways. First, local households earn cash income by selling ecosystem products, such as fihoney, and nipa palm, at local markets. Second, the use of natural resources provides substantial subsistence such as food, fresh water, and timber. However, residents’ income may be signifi cantly increased by improved resource management, including reducing local authority corruption and improvements in law enforcement. Our paper concludes with a range of recommendations for enhancing residents’ standard of living while conserving natural resources.

Implication of Organic Matter on Arsenic and Antimony Sequestration in Sediment: Evidence from Sundarban Mangrove Forest, India

This study reports the measurement of stability constants for the interaction of As (V and III) and Sb (V and III) with humic substances extracted from aquatic sediments of the Sundarban mangrove forest ecosystem. It was observed that As and Sb formed a slightly more stable association with fulvic acid (FA) than with its humic acid (HA) counterpart. Quenching of fluorescence at increasing As (III and V) or Sb (III and V): FA or HA ratios was obtained that ideally correspond to a 1:1 complexation model. Quite strong complexation of As and Sb by FA and HA occurs at neutral pH, indicating that HA and FA probably markedly affect the mobility of As and Sb in the mangrove environment.

A review on the ichthyofaunal diversity in mangrove based estuary of Sundarbans

The two great rivers of India the Ganga and the Brahmaputra form their estuary at the lower part of West Bengal and most of the part of this estuarine system is surrounded by Sundarban mangrove forest. This mangrove based estuarine ecosystem harbors a large number of fin fishes i.e. more or less 267 species of fishes which belong under 81 families. Estuary’s own ecological characters and mangrove’s all beneficial features support this high species diversity here. But due to continuously increasing natural and anthropogenic stresses, nowadays this entire species community faces a tremendous problem of extinction. 82 species under 24 families loss their juveniles in a significant number regularly due to wild harvest of lucrative prawn seeds. The present article aims to review the roles of estuary and mangroves in enrichment of finfish diversity and the possible threats causing harm to the same.

Improved model calculation of atmospheric CO2 increment in affecting carbon stock of tropical mangrove forest

Because of the difficulties in setting up arrangements in the intertidal zone for free-air carbon dioxide enrichment experimentation, the responses to increasing atmospheric carbon dioxide in mangrove forests are poorly studied. This study applied box model to overcome this limitation, and the relative changes in present level of reservoirs organic carbon contents in response to the future increase of atmospheric carbon dioxide were examined in the Avicennia-dominated mangrove forest at the land–ocean boundary of the northeast coast of the Bay of Bengal. The above- and below-ground biomass (AGB+BGB) and sediment held different carbon stock (53.20±2.87Mg C ha−1 (mega gram carbon per hectare) versus 18.52±2.77Mg C ha−1). Carbon uptake (0.348mg C m−2s−1) is more than offset by losses from plant emission (0.257mg C m−2s−1), and litter fall (13.52µg C m−2s−1) was more than soil CO2 and CH4 emission (8.36 and 1.39µg C m−2s−1, respectively). Across inventory plots, Sundarban mangrove forest carbon storage in above- and below-ground live trees and soil increased by 18.89 and 5.94Mg C ha−1 between June 2009 and December 2011. Box model well predicted the dynamics of above- and below-ground biomass and soil organic carbon, and increasing atmospheric carbon dioxide concentrations could be the cause of 1.1- and 1.57-fold increases in carbon storage in live biomass and soil, respectively, across Sundarban mangrove forest rather than recovery from past disturbances.

Spatial and Temporal Variation of Total Nitrogen and Total Phosphorus in Major River Systems of Sundarbans Mangrove Forest, Bangladesh

Mangrove provides a unique ecological environment for diverse communities and Sundarbans is a rapidly changing ecosystem due to various anthropogenic activities. In order to assess the spatial and temporal variation of total Nitrogen and total Phosphorus concentration in Major River Systems of Sundarbans, a study was carried out from September, 2010 to February, 2011. Fourteen sampling location from major river systems were chosen. During post monsoon and winter seasons the range of total Phosphorus (0.326-0.409 mg/L and 0.091-0.371 mg/L respectively) and total nitrogen (2.52-3.50 mg/L and 3.43-5.25 mg/L respectively) were observed in Rupsha - Passur river system. On the other hand the range of total Phosphorus (0.475-0.144 mg/L and 0.060-0.113 mg/L respectively) and total nitrogen (2.31-3.61 mg/L and 3.22- 5.95 mg/L respectively) were found in Arpangashia - Malancha river system during post monsoon and winter seasons. The nutrients of water of Baleswar- Bhola river system during rainy and dry seasons were found in the range of total Phosphorus (0.106-0.364 mg/L and 0.053-0.075 mg/L respectively) and total nitrogen (2.59-3.57 mg/L and 2.87-5.60 mg/L respectively). Total Nitrogen and total phosphorus levels were relatively higher than the EPA standards for surface water during the two seasons. The Dynamic nutrients level observed in the study area may have severe consequences on the in-dwelling aquatic flora and fauna.

Spatial and Temporal Variations in Phytoplankton Abundance and Species Diversity in the Sundarbans Mangrove Forest of Bangladesh

The study examined taxonomic composition, abundance and spatial distribution of phytoplankton, and water quality of three major river systems of the Sundarbans. A total of 134 phytoplankton species were identified, and diversity and abundance were found to fluctuate with time and space. A total of 97 species were enumerated in Rupsha-Pashur while 122 and 110 in Khalpatua-Arpangachia and Bhola-Baleswar river system respectively. Abundance was lowest (3.709×103 ± 4.257×102 cellsL-1) in monsoon and highest (2.174×105 ± 1.723×105cellsL-1) in summer in Bhola-Baleswar. Species composition was dominated by Bacillariophyta over the area except in summer in Bhola-Baleswar, where Cyanophyta become dominated. Species diversity, richness and evenness index varied between 2.03-4.64, 1.2-2.44, 0.77-1.5 in Rupsha-Pashur; 2.47-3.85, 1.8-5.84, 0.78-0.94 in Khalpatua-Arpangachia; and 0.66-4.27, 1.19-5.12, 0.59-1.29 in Bhola-Baleswar. Water temperature, pH, DO, Transparency and Salinity were determined between 19.92°C-31°C; 6.7-7.87; 3.93 mgL-1-7.37 mgL-1; 7.5 cm-60 cm; 2-23 ppt, respectively. Nutrient elements i.e. NO3 -, PO4 3-, NH4 +, SiO4 4- fluctuated seasonally from 0.0062 to 1.633 mgL-1, 0.005 to 0.772 mgL-1, 0.038 to 2.467 mgL-1, 3.124 to 27.234 mgL-1, respectively. Chlorophyll-a concentrations were fluctuated seasonally within 0.24 to 5.94 μgL-1 and highest phytoplankton biomass was observed in Bhola-Baleswar in summer. Chlorophyll concentration was found to be correlated positively with transparency, salinity and nutrients.

Allometry, above-ground biomass and nutrient distribution in Ceriops decandra (Griffith) Ding Hou dominated forest types of the Sundarbans mangrove forest, Bangladesh

The Sundarbans, the world’s largest single expanse of natural mangroves located in southern Bangladesh, is the most productive mangrove ecosystem in the world. Ceriops decandra (Griff.) Ding Hou is the dominant shrub in the strong saline zone of the Sundarbans and is mainly extracted for fuel wood, charcoal and tannin. The harvest of C. decandra has decreased by about 50 % in the Sundarbans during the last 10 years creating a major concern. This study derived allometric models of above-ground biomass and estimated of above-ground standing and harvestable biomass and nutrient stock in C. decandra in dominant forest types (C. decandra and C. decandra–Excoecaria agallocha) in the Sundarbans. Allometric relationships between collar girth (CG) and biomass of plant parts (leaf, branch and stem) were tested using linear, power and logarithmic equations. The power equation was found to be most suitable. The density and the estimated total aboveground biomass of C. decandra in C. decandra and C. decandra–E. agallocha forest types were 33,237 and 965 stems/ha (density) and 33.49 and 14.36 t/ha (biomass), respectively. Also, 13.56 and 6.61 t/ha of harvestable biomass were estimated, from C. decandra and C. decandra–E. agallocha forest types, respectively. Nitrogen, potassium and phosphorus concentrations in the leaves, branches and stems showed significant (p < 0.05) variation. The findings of the present study will help to quantify the impact of present harvesting techniques and alteration of different silvicultural intervention like fixation of felling cycle, felling criterion, and regeneration and slash treatment.

Microbial Ecosystem in Sunderban Mangrove Forest Sediment, North-East Coast of Bay of Bengal, India

This is the first documentation of seasonal and spatial fluctuation of the culturable microbial population collected from different zones in the sediment of the Sunderban mangrove forest. The population of cellulose degrading bacteria, [mean value of CFU 6.189 ± 1.025 × 106 (g dry weight of sediment)−1] was found to be maximum during post monsoon in the deep forest region, whereas, the fungal population [mean value of CFU 3.424 ± 0.886 × 106 (g dry weight of sediment)−1] was found to be maximum during pre-monsoon in the rooted region. The abundances of microbes, in decreasing order, studied from different zones are nitrifying bacteria [mean value of CFU 1.125 ± 0.359 × 106 (g dry weight of sediment)−1], phosphorous solubilizing bacteria (PSB) [mean value of CFU 0.805 ± 0.322 × 106 (g dry weight of sediment)−1], free living nitrogen fixing bacteria [mean value of CFU 0.417 ± 0.120 × 106 (g dry weight of sediment)−1] and sulfur reducing bacteria (SRB) [mean value of CFU 0.356 ± 0.125 × 106 (g dry weight of sediment)−1]. The content of organic carbon in the soil decreased from the deep forest region to the rooted and unrooted region but a reverse profile was found for soil salinity and soil silicate concentration. The results from the present study indicate that the monsoon cycle has a pronounced effect on the microbially dominated biogeochemistry in the sediment and consequently on the ecology of the Sundarban mangrove forest.

Intra-Annual Variation of Modern Foraminiferal Assemblage in a Tropical Mangrove Ecosystem in India

This study relates the abundance of foraminifera with the fluctuations in hydrobiological characteristics generated by the monsoonal cycle in a tropical mangrove ecosystem. Monthly variation of physicochemical properties of water and sediment, phytoplankton production, foraminiferal assemblages were measured in the littoral zone of the Sundarbans mangrove forest. Intra-annual variation of foraminifera exhibited a maximum abundance during the post-monsoon period and out of the 25 genera, numbers of calcareous and agglutinated forms were 16 and 9, respectively. Live benthic foraminifera were found to inhabit a wide range of sediment depths and inhabiting a high energy environment their abundance was not restricted to the uppermost centimeter. Owing to mechanical damage (due to high energy system), chemical dissolution and intense bioturbation, the taphonomic processes in this mangrove swamp could result in the destruction of the small size fraction of foraminifera, including agglutinated tests. The low numbers of agglutinated foram could be due to silty clay substrate. Abundance of more calcareous dead specimens over live ones could be attributed to predation and transportation of dead marine species. Most of the marine species could not survive in this freshwater dominated system. Anthropogenic nutrient input and diatom bloom in association with enhanced food to benthos are important controlling factors on foraminiferal abundance and composition.

Allometric relationship for estimating above-ground biomass of Aegialitis rotundifolia Roxb. of Sundarbans mangrove forest, in Bangladesh

Tree biomass plays a key role in sustainable management by providing different aspects of ecosystem. Estimation of above ground biomass by non-destructive means requires the development of allometric equations. Most researchers used DBH (diameter at breast height) and TH (total height) to develop allometric equation for a tree. Very few species-specific allometric equations are currently available for shrubs to estimate of biomass from measured plant attributes. Therefore, we used some of readily measurable variables to develop allometric equations such as girth at collar-height (GCH) and height of girth measuring point (GMH) with total height (TH) for A. rotundifolia, a mangrove species of Sundarbans of Bangladesh, as it is too dwarf to take DBH and too irregular in base to take Girth at a fixed height. Linear, non-linear and logarithmic regression techniques were tried to determine the best regression model to estimate the above-ground biomass of stem, branch and leaf. A total of 186 regression equations were generated from the combination of independent variables. Best fit regression equations were determined by examining co-efficient of determination (R2), co-efficient of variation (CV), mean-square of the error (MSerror), residual mean error (Rsme), and F-value. Multiple linear regression models showed more efficient over other types of regression equation. The performance of regression equations was increased by inclusion of GMH as an independent variable along with total height and GCH.

Depth Integrated Microbial Community and Physico-Chemical Properties in Mangrove Soil of Sundarban, India

In the Sundarban Mangrove forest microbial activities are dominantly involved in both the mineralization and decomposition processes that regulate nutrient profile in soil of different depth. It was found that besides changing the water and soil quality, monsoonal cycle plays a crucial role in regulating microbial population distribution in the mangrove soil. Statistical analyses revealed that organic carbon was the most significant factor that regulated the total microbial population. The cellulose degrading bacteria, [mean value of CFU 14.32 × 106 (gm dry weight of soil)–1] was dominant throughout the year. The sulfate reducing bacteria showed an increasing trend along depth with a minimum value at the surface i.e. 6.113 × 106 (gm dry weight of soil)–1 and 12.312 × 106 (gm dry weight of soil)–1 at a depth of 60 cm. Intensification of monsoonal cycle could heavily affect microbe dominated soil biogeochemistry and subsequent change in the regional ecology of the Sundarban Mangrove Forest.

Seasonally and Spatially Coordinated Strategy of Detritus Conservation and Use in the World’s Largest Mangrove Ecosystem

A study in the inter-tidal regions of Indian Sundarban mangrove forest has revealed that intensified detritus input into marine estuaries during pre-monsoon (summer) coupled with lowest volume and intensity of water influx into the sea through the Ganges during this time create a localized and relatively static pool of nutrients in the estuarine water. This detritus reserve immediately acts as the source of nutrients for the huge population of detrivores that invade these estuaries during the monsoon when water flow through the rivers is huge and is coupled with severe rolling of water in the confluence zones. Rolling of water facilitates the uplifting and pushing of organic reserves of these inundated estuaries more towards the sea for the availability to animals migrating from sea towards the river mouth. C/N ratio has been very high in the soil with high soil organic C content indicating soil N limitation. Huge detritus supply has been ensured by a moderate decomposition of a huge litter-fall, with a maximum of 9721 g m−2 year−1 and high below ground fine + coarse root production that can range up to 3265 g m−2 year−1 measured up to a depth of 15 cm only. Peak litter fall coupled with high root mortality have been encountered during pre-monsoon when soil water’s salinity is highest and dissolved oxygen concentration is at its lowest. As a part of nutrient conservation strategy, lion share of the total organic trash instead of being acted upon by decomposers goes into a very efficient mechanism of ‘formation’ of relatively static (lacks much mobilization) detritus food reserve particularly during pre monsoon, for its subsequent ‘best possible utilization’ by the detrivores that invade the ecosystem and reproduce in large numbers during monsoon.

A review of the role of property rights and forest policies in the management of the Sundarbans Mangrove Forest in Bangladesh

The purpose of this paper is to critically evaluate past forest management policies and property rights regimes in achieving sustainability of the Sundarbans Mangrove Forest (SMF) in Bangladesh. The adequacy of forest policies to reflect regimes of property rights in their design and implementation is examined using content analysis. The analysis synthesises forest policies of four distinct historical time periods, and the embedding of property rights during those periods using Schlager and Ostrom's typology. The findings reveal the inadequacy of the existing state property rights regime to secure the livelihood of 3.5million people in marginalised and disadvantaged forest-dependent communities, and to achieve sustainability in the SMF by reversing the trend of rapid reduction of forest resources. The challenge, therefore, is to find an alternative property rights regime to address the missing link between conservation and livelihood-security of forest-dependent communities using sustainable management practices in the SMF.

DNA Base Composition Heterogeneity in Two Avicennia Species in Response to Nitrogen Limitation in the Sundarban Mangrove Forest, India

DNA Base Composition Heterogeneity in Two Avicennia Species in Response to Nitrogen Limitation in the Sundarban Mangrove Forest, India

Carbon sequestration and annual increase of carbon stock in a mangrove forest

Here we show carbon stock is lower in the tropical mangrove forest than in the terrestrial tropical forest and their annual increase exhibits faster turn over than the tropical forest. Variable for above ground biomass are in decreasing order of importance, breast height diameter (d), height (H) and wood density (ρ). The above ground biomass (AGB) and live below ground biomass (LBGB) held different biomass (39.93 ± 14.05 t C ha−1 versus 9.61 ± 3.37 t C ha−1). Carbon accrual to live biomass (4.71–6.54 Mg C ha−1 a−1) is more than offset by losses from litter fall (4.85 Mg C ha−1 a−1), and carbon sequestration differs significantly between live biomass (1.69 Mg C ha−1 a−1) and sediment (0.012 Mg C ha−1 a−1). Growth specific analyses of taxon density suggest that changes in resource availability and environmental constrains could be the cause of the annual increase in carbon stocks in the Sundarbans mangrove forest in contrast to the disturbance – recovery hypotheses.

Salt tolerant culturable microbes accessible in the soil of the Sundarban Mangrove forest, India

Sundarban Mangrove forest is highly productive marine ecosystem where halophilic microbes actively participate in bio-mineralization and biotransformation of minerals. The population of aerobic halophilic microbes was studied to determine their distribution with the availability of different physicochemical parameters with increasing depth of this forest sediment. The present study revealed that microbes present in the top soil region were less tolerant to fluctuation in salinity than the middle and bottom segment. Microbes isolated from bottom segment showed higher growth rate in anaerobic condition. A decreasing trend of total microbial population and organic carbon content of soil were found with increase in depth. In contrary a reverse profile was found for salinity. A significant stratification was found to exist among microbial population and the salty nature of the soil of Sundarban Mangrove forest.

Depth profile exploration of enzyme activity and culturable microbial community from the oxygen-starved soil of Sundarban mangrove forest, India

Populations of culturable microbes and activities of dehydrogenase & ?-D glucosidase were found maximum in surface soil and decreased with increase in depth in Sundarban mangrove environment.The maximum (13.529 X 106 C.F.U g-1 dry weight of soil) and minimum (11.547 X 106 C.F.U g-1 dry weight of soil) total microbial popu- lations in surface soil were recorded during po- st-monsoon and monsoon respectively. At 60 cm depth, the lower (6.396 X 106 C.F.U g-1 dry weight of soil) and higher (8.003 X 106 C.F.U g-1 dry weight of soil) numbers of total microbial populations were observed during monsoon and post-monsoon respectively. A decreasing trend of total microbial load, enzyme activities and nutrient status with organic carbon were found with increase in depth throughout the year. Present study revealed the relationship among depth integrated variations of physico-chemical compo- nents (viz. soil temperature, pH, moisture, orga- nic-C, .nitrogen, and available-P) and microbial populations as well as activity of dehydrogenase and ?-D glucosidase enzymes.