Sundarbans Research Articles

Challenges towards the Sustainability and Enhancement of the Indian Sundarban Mangrove's Blue Carbon Stock.

The Sundarban is the world's largest contiguous mangrove forest and stores around 26.62 Tg of blue carbon. The present study reviewed the factors causing a decline in its blue carbon content and poses a challenge in enhancing the carbon stock of this region. This review emphasized that recurrent tropical cyclones, soil erosion, freshwater scarcity, reduced sediment load into the delta, nutrient deficiency, salt-stress-induced changes in species composition, mangrove clearing, and anthropogenic pollution are the fundamental drivers which can potentially reduce the total blue carbon stock of this region. The southern end of the Ganges-Brahmaputra-Meghna Delta that shelters this forest has stopped its natural progradation due to inadequate sediment flow from the upper reaches. Growing population pressure from the north of the Sundarban Biosphere Reserve and severe erosion in the southern end accentuated by regional sea-level rise has left minimal options to enhance the blue carbon stock by extending the forest premises. This study collated the scholarly observations of the past decades from this region, indicating a carbon sequestration potential deterioration. By collecting the existing knowledge base, this review indicated the aspects that require immediate attention to stop this ecosystem's draining of the valuable carbon sequestered and, at the same time, enhance the carbon stock, if possible. This review provided some key recommendations that can help sustain the blue carbon stock of the Indian Sundarban. This review stressed that characterizing the spatial variability of blue carbon with more sampling points, catering to the damaged trees after tropical cyclones, estuarine rejuvenation in the upper reaches, maintaining species diversity through afforestation programs, arresting coastal erosion through increasing sediment flow, and combating marine pollution have become urgent needs of the hour. The observations synthesized in this study can be helpful for academics, policy managers, and decision makers willing to uphold the sustainability of the blue carbon stock of this crucial ecosystem.

Exopolysaccharide producing bacteria of Sundarban Mangrove Forest soil and their antibiotic sensitivity profile

Exopolysaccharide producing bacteria of Sundarban Mangrove Forest soil and their antibiotic sensitivity profile

Environmental drivers and ecological implications of a ctenophore swarm: a case study from the Bay of Bengal, northern Indian Ocean

Abstract Ctenophores are quick responders to coastal environmental changes and play a crucial role in marine food web dynamics. We report the environmental drivers of a ctenophore swarm (Pleurobrachia spp.) and associated ecological changes in estuarine and coastal waters of the Sundarbans mangrove–estuarine complex in the northern Bay of Bengal (BoB). Plankton and fish samples were collected from estuarine and coastal waters at the peak of estuarine outflow in the northeast monsoon (NEM). Sampling locations at the estuarine mouth witnessed ctenophores (Pleurobrachia pileus and Pleurobrachia globosa) in swarming proportions. Multivariate statistical analysis revealed significant differences in hydrographical and biological properties between the swarm and non-swarm areas. The sea surface salinity, ammonium, and mesozooplankton (MSP) density were positively correlated while microzooplankton (MCZ) density was negatively correlated with the ctenophore swarm. Fish caught from swarm locations, dominated by microbial food web consisted of species of less market value, while those from the non-swarm locations, dominated by conventional plankton food web consisted mainly of commercially important species. Thus, in the first-ever record from a commercially important fishing ground in the BoB, this study provides evidence of how a ‘dead end’ plankton predator affects the plankton food web organization and fisheries in tropical coastal waters.

Multi-dimensional approach for an environmental health assessment of a deltaic mangrove ecosystem, Sundarbans

The largest contiguous tract of tidal halophytic mangroves in Bangladesh is about 10,000 km2. It has a wide range of physiochemical and nutritional qualities, as well as ecological health. To understand the hazardous and heavy metal concentrations, ten heavy metals concentrations were examined in both water and sediment. Indices for pollution and contamination, such as Modified Hazard Quotient (mHQ), Degree of Contamination (Cd), Geo-Accumulation Index (Igeo), Mean Effect Range Median Quotient (M-ERM-Q), Nemerow's Pollution Index (NPI), Heavy Metal Evaluation Index (HEI) give a more accurate diagnostic result for water and sediment in the Sundarbans mangroves. The Water Quality Index (WQI) and Mangrove Quality Index (MQI) are also evaluated for a final statement. The nutrient concentrations average of NO3, PO4, NH3, and SiO2 are found 0.59 ± 0.05, 0.09 ± 0.01, 0.23 ± 0.02 and 1.72 ± 0.17 (mg/L), respectively in water. Pb, Cd, Hg, As, Cr, Mn, Fe, Ni, Cu, and Zn have average concentrations of 19.1 ± 1.62, 1.1 ± 0.11, 0.48 ± 0.04, 1.19 ± 0.11, 83.27 ± 8.3, 35.45 ± 2.95, 282.73 ± 30.82, 33.85 ± 2.95, 6.09 ± 0.54, and 172.18 ± 17.15 (µg/L) in surface water and 19.57 ± 1.25, 0.16 ± 0.005, 0.026 ± 0.0009, 1.48 ± 0.08, 36.38 ± 4.31, 456.66 ± 76.76, 42.36 ± 2.57, 53.81 ± 1.93, 20.67 ± 1.24, and 43.60 ± 6.09 (mg/kg) for sediments. According to the heavy metals analysis indices, we discovered very little contamination. The WQI indicates that the water quality in the Sundarbans Mangroves is generally protected but occasionally deteriorates. The MQI categorizes the Sundarbans as a moderate mangrove, falling into category 3. Despite being controlled the heavy metal pollution is getting worse as the Mongla port's economy grows. A more seasonal and in-depth approach to this topic can be achieved by collecting more samples over a year. The deltaic Sundarbans mangrove ecosystem is currently in moderate to an acceptable condition, with low or non-significant pollution levels and fair water quality, according to this study, except for certain constraints.

Isolation and characterization of halotolerant plant growth promoting rhizobacteria from mangrove region of Sundarbans, India for enhanced crop productivity.

Halotolerant plant growth promoting rhizobacteria (PGPR) are beneficial microorganisms utilized to mitigate the biotic and abiotic stresses in plants. The areas of Sundarban mangroves of West Bengal, India have been reported to be rich in halotolerant microflora, yet major area remains unexplored. The present study, therefore, aims to map down the region-specific native microbial community potent of salt tolerance, plant growth promoting (PGP) activity and antagonistic activity against fungal pathogens. Bacterial samples were isolated from the saline soil of the Sundarban mangroves. A total of 156 bacterial samples were isolated and 20 were screened for their salt tolerance potential. These isolates were characterised using morphological, biochemical, and molecular approaches. Based on 16s rRNA sequencing, they were classified into 4 different genera, including Arthrobacter sp. (01 isolate), Pseudomonas plecoglossicida (01 isolate), Kocuria rosea (01 isolate), and Bacillus (17 isolates). The halotolerant isolates which possessed plant growth promoting traits including phosphate, and zinc solubilization, indole acetic acid production, siderophore, and ammonia generation were selected. Further, the effect of two halotolerant isolates GN-5 and JR-12 which showed most prominent PGP activities was evaluated in pea plant under high salinity conditions. The isolates improved survival by promoting germination (36 to 43%) and root-shoot growth and weight of pea plant in comparison to non-inoculated control plants. In a subsequent dual culture confrontation experiment, both these halo-tolerant isolates showed antagonistic activities against the aggressive root rot disease-causing Macrophomina phaseolina (Tassi) Goid NAIMCC-F-02902. The identified isolates could be used as potential bioagents for saline soils, with potential antagonistic effect on root rot disease. However, further studies at the physiological and molecular level would help to delineate a detail mechanistic understanding of broad-spectrum defence against salinity and potential biotic pathogen.

Evaluating Social Equity in Protected Areas Co-management: Evidence from the Sundarbans Mangrove Forests, Bangladesh

Protected areas (PA) co-management can offer equitable benefits from global to local level. Therefore, social equity has come out as a vital goal in PA co-management for ethical and instrumental reasons. In the Bangladesh context, however, social equity issues have been less studied in PA co-management. This study was conducted in the Sundarbans of Bangladesh, and we evaluated social equity as multidimensional concepts of recognitional, procedural and distributional equity. We employed mixed approaches, including 122 structured interviews using a 5-point Likert scale, 15 key informants interview and 4 focus group discussions to collect data on equity perception. Mean and frequency (percent) were calculated and generalized linear models were performed to analyze the predictor’s influence on equity perception. The results showed that recognitional equity was perceived high, while procedural and distributional equity perceived moderate and low. Findings would be useful for policy makers in framing policies towards equitable PA co-management.

How biotic, abiotic, and functional variables drive belowground soil carbon stocks along stress gradient in the Sundarbans Mangrove Forest?

Mangrove forests, some of the most carbon-dense ecosystems on Earth, play an important role in climate change mitigation through storing carbon in the soil. However, increasing anthropogenic pressures and sea level rise are likely to alter mangrove forest structure and functions, including the major source of carbon in mangrove ecosystems — below-ground soil carbon stocks (BSCS). Although estimating soil carbon stocks has been a popular practice in the mangroves, but poorly understood the (I) the linkage between BSCS and key ecosystem drivers (i.e., biotic, abiotic, and functional) and in (II) determining the pathways of how BSCS and multiple forest variables interact along stress gradients. This lack of understanding limits our ability to predict ecosystem carbon dynamics under future changes in climate. Here, we aimed to understand how abiotic factors (such as salinity, canopy gap fraction, nutrients, and soil pH), biotic factors (e.g., structural parameters, canopy packing, and leaf area index, LAI), and forest functional variables (e.g., growth and aboveground biomass stocks, AGB) affect BSCS (i.e., soil organic carbon, SOC, and root carbon, RC) using spatiotemporal data collected from the Sundarbans Mangrove Forest (SMF) in Bangladesh. We observed that BSCS decreased significantly with increasing salinity (e.g., from 70.6 Mg C ha−1 in the low-saline zone to 44.6 Mg C ha−1 in the high-saline zone). In contrast, the availability of several macronutrients (such as nitrogen, phosphorous, and potassium), LAI, species diversity, AGB, and growth showed a significant positive effect on SOC and RC. Stand properties, including tree height, basal area, density, canopy packing, and structural diversity, had a non-significant but positive impact on RC, while tree height and basal area significantly influenced SOC. Pathway analysis showed that salinity affects BSCS variability directly and indirectly by regulating stand structure and restricting nutrients and forest functions, although basal area, nutrients, and LAI directly enhance RC stocks. Our results indicate that an increase in nutrient content, canopy density, species diversity, and leaf area index can enhance BSCS, as they improve forest functions and contribute to a better understanding of the underlying mechanisms.

Assessing effectiveness of nature-based solution with big earth data: 60 years mangrove plantation program in Bangladesh coast

BackgroundIn the climate change context, nature-based solution (NBS) is considered one of the effective tools to increase the resilience of socio-ecological system. The concept coincides with the government’s attempts of afforestation and reforestation programs that have been going on for 60 years in Bangladesh. This study, therefore, envisaged understanding how NBS (mangrove afforestation and reforestation) works to promote climate change resilience through the synthetization of remote sensing-based big earth data, statistical tools, and models. The study took the entire coast of Bangladesh except for Sundarbans Reserve Forest and rolled back to 1962 to work on 60 years’ time series data. Declassified CORONA satellite imagery along with Landsat satellite imagery was used, which is the first-ever attempt in the remote sensing-based ecosystem work in Bangladesh.ResultsThe study's main innovation is to spatially establish the effectiveness of the NBS. The study critically assessed and estimated stable lands and their socio-economic benefits as part of the effectiveness of the NBS. As part of the NBS-derived benefits in the context of climate change, it estimated the sequestrated carbon in mangrove forests. A significant positive relationship was observed between the increase of mangroves and stable lands. Near about 448,011 ha of agricultural land was stabilized due to the NBS intervention whose economic value is 18,837 million USD. In addition, 29,755.71 kt of carbon have been sequestrated due to NBS program.ConclusionsThe concept of NBS is still in the development stage and very little or no work has been done so far in measuring and labeling the effectiveness of the NBS. Therefore, our study can innovatively contribute to the scientific community to show the effectiveness of the NBS in three domains (social, economic and ecological) in the changing climatic scenario.

Isolation and Screening of Dye Degrading Lignocellulolytic Bacteria from Sundarban Mangrove Ecosystem, West Bengal, India

The present research work was carried out on isolating lignocellulolytic enzyme-producing natural bacterial isolates of the Sundarban Mangrove ecosystem in West Bengal, India. Multiple bacterial isolations and qualitative as well as quantitative screening of the isolates was conducted by selective media plates and dye decolorization assay. Growth characterization of the top three isolates, namely GD1, GD2, and GD3, was determined in both nutrient broth and selective media. GD1 showed laccase activity in ABTS plate and decolorized congo red, malachite green, and methylene blue by 64.82%, 47.69%, and 33.33%, respectively, which is the inherent property of laccase. Along with the maximum laccase activity (9.72U/L), it also showed a little amount of cellulase (5.8U/ml) and pectinase (0.55U/ml) activity in the enzyme assay. GD2 showed maximum cellulase activity (6.56U/ml) with only 3.3% degradation of congo red and 39.43% degradation of malachite green. Like GD1, GD2 also bears 5.6U/L laccase and 0.12U/ml pectinase enzyme activity. The last isolate, GD3 specialized in pectinase production and having 4.4U/ml enzyme activity, degraded congo red by 66.75% and malachite green by 54.26%.All isolates showed activity between 30° and 37°C, and pH ranges from 4.5 to 7. The outcomes of this research will be useful in the fiber industry like jute or banana, dye industry, pulp-paper industry, and textile industry for waste remediation, recycling, and fiber modification.

Rising trend of man-tiger conflict at man-nature interface of Indian Sundarbans: study towards traditional understanding and challenging livelihood of Sundarbans people

Sundarbans region has its own unique physiographical, ecological, economical and socio-cultural individuality. As a home of nearly nine million people the entire Sundarbans area has emerged as one of the poorest and malnourished region of the South-east Asia. Man-tiger conflict or tiger attacks in riverside settlements around the Sundarbans Reserve Forest in West Bengal, India are a continuous matter of concern. The principal objective of this research is to identify the reasons behind the increasing human-tiger conflict in Indian Sundarbans. Landsat-8 satellite image (path = 138, row = 45, 30 m spatial resolution and eleven spectral bands) has been used to identify the high possible areas of Man-Tiger conflict within the SBR region. The survey involved 100 respondents selected from Gosaba, Kultali, Basanti and Mathurapur II CD blocks in which 85 respondents aged 50 and above were actively participated in the perceptional survey process. Result showed that major proportion of the Sundarbans people is traditionally dependent on forest resources for maintenance of their livelihood. Research identified the principal factors which have been responsible for increasing man-tiger conflict in Sundarbans such as degeneration of forests, habitat loss due to flood and sea level rise, encroachment into wildlife territories for economic activities, intrusion into human settlements for scarcity of wild pray in forest. Deulbari, Dongajora, Bhuvaneswari are the areas of human-tiger conflicts due to closeness with nearest buffer forest area. The adjoining rivers of these two villages Melmel and Gomor are highly vulnerable due to its proximity of reserve forest.

Seasonal variability of modern benthic foraminifera assemblages in a mangrove ecosystem from northeast coastal Bay of Bengal

Benthic foraminifera assemblages, nutrient dynamics of surface and porewater from 10 intertidal sites spanning over two years (2019–2020) covering two major estuaries in Sundarbans mangrove were evaluated to understand role of seasonal precipitation and primary production (driven by eddy nutrients) with a focus on standing crop. Benthic foraminifera abundance ranged between 280 individuals/10 cc in pre-monsoon (2019), 415 individuals/10 cc in post-monsoon 2019 and 630 individuals/10 cc in post-monsoon (2020). Standing crop was highest in post-monsoon coinciding with eddy nutrients driven stoichiometry and increase in abundance of large diatom cells. Calcareous and agglutinated foraminifer taxa Ammonia sp.1, Quinqueloculina seminulum, Entzia macrescens and Textularia sp. respectively were frequent. Entzia macrescens was found in dense mangrove vegetation sites; exhibited strong relationship with sediment texture and pore water total organic carbon. One of the major findings is mangroves with pneumatophores improves oxygen availability in sediment and leads to an increase in standing crop.

Establishment of seed biopriming in salt stress mitigation of rice plants by mangrove derived Bacillus sp.

Salinity stress is one of the growing challenges for agro-ecosystems. Present study aimed to explore the role of halotolerant bacteria in alleviation of salinity stressed rice plants. Bacillus sp. strain PnD was isolated from Indian Sundarban Mangrove Forest, conferred plant growth promoting (PGP) traits like indole 3-acetic acid (IAA) production, phosphate solubilization, siderophore production but had negative effect of 1-aminoacyclopropane 1-carboxylate (ACC) deaminase activity. Rice seeds (Oryza sativa L.) of Amal-Mana variety were subjected to salinity stress for 24 h by being immersing in 1% NaCl. Another set of seeds were soaked in a broth cultured with Bacillus sp strain PnD, containing 1% NaCl in the media, denoted as bioprimed condition. The seeds that were soaked in distilled water had no salt stress and were not primed, served as control. All the treatments were assigned randomly to the seeds and each treatment was replicated three times resulting in nine experimental units. Completely randomized design was adopted in this experiment. Overall results showed bioprimed seeds soaked in 1% NaCl for 24 h had significantly higher germination percentage, seedling growth, photosynthetic pigments content compared to control and non-primed salinity exposed plants. Scanning electron micrograph revealed root colonization of bacteria in bioprimed seedlings, tissue distortion was also noted during salt stress. The study revealed that Bacillus sp. strain PnD is a potential plant growth promoting bacterium (PGPB), and the seed biopriming technique can efficiently mitigate inhibitory effects of salinity stress in rice plants.

How Does Increased Salination Jeopardize the Floral Diversity of the Sundarbans Mangrove of Bangladesh?

How Does Increased Salination Jeopardize the Floral Diversity of the Sundarbans Mangrove of Bangladesh?

Assessing the Impact of Climate Change on the Nypa Palm (Nypa Frutican) and Associated Species of the Sundarbans Mangrove of Bangladesh

Assessing the Impact of Climate Change on the Nypa Palm (Nypa Frutican) and Associated Species of the Sundarbans Mangrove of Bangladesh

Nature-based Mitigation Strategies to Sea Level Rise and Other Climate Change Impacts on the Sundarbans Mangrove of Bangladesh: Analyzing the Legal, Institutional and Policy Framework

Nature-based Mitigation Strategies to Sea Level Rise and Other Climate Change Impacts on the Sundarbans Mangrove of Bangladesh: Analyzing the Legal, Institutional and Policy Framework

Impact of Climate Change: Whispering from the Sundarbans Mangrove of Bangladesh

Impact of Climate Change: Whispering from the Sundarbans Mangrove of Bangladesh

Antagonistic activity of Bacillus amyloliquefaciens subsp. amyloliquefaciens against multidrug resistant Serratia rubidaea

Serratia rubidaea is an opportunistic Gram-negative pathogen that has developed antimicrobial resistance to a variety of commercial antibiotics. The spread of this multidrug-resistant pattern predicts that it will get harder and harder to treat S. rubidaea infections in the future. For this perception, antimicrobial proteins might represent a safe, effective, and biodegradable alternative because their site of action is on cyclic peptides. In this study, one candidate Bacillus amyloliquefaciens subsp. amyloliquefaciens was isolated from the soil of Sundarban mangrove forest, and its identification was confirmed both using the PCR (Polymerase chain reaction) method and the BIOLOG™ microbial identification system. The antibacterial protein, which has a molecular mass of about 50 kDa, was isolated from B. amyloliquefaciens subsp. amyloliquefaciens. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to confirm the extracted protein's purity. This potential protein was discovered to develop and exhibit antagonistic activity throughout a broad temperature, pH, and salinity range. At doses ranging from 300 to 400 μg/ml, this protein has antagonistic activity against multidrug resistant S. rubidaea and a wide range of other resistant pathogenic bacteria such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and so on. The research provides new insights to develop bio-control agents that can be applied for prevent, treat, and control infectious diseases caused by multidrug resistant S. rubidaea, as well as other pathogenic bacteria.

Exopolysaccharide (EPS) Producing Bacteria of Sundarbans Mangrove Forest Soil

The present study was undertaken to investigate the exopolysaccharide (EPS) producing bacteria from Sundarbans Mangrove Forest (SMF) soil of Bangladesh. The pH and aerobic heterotrophic bacterial counts of the soil samples ranged from 5.83 to 7.77 and 0.87 × 107 to 7.2 × 107 cfu/g, respectively. Potential 18 EPS producing bacterial isolates were selected for detailed study among which 15 were provisionally identified as members of the genus Bacillus, 2 were recognized as Dinococcus sp. and another one as Micrococcus sp. The genus Bacillus includes 7 distinct species viz. B. stearothermophilus, B. subtilis, B. brevis, B. marinus, B. schlegelli, B. pumilus and B. globisporous. The highest EPS production was found in the LB medium. The pHs of 6.5-7.5, 0% salinity, and 37°C temperature were found to be optimum for better growth of EPS producing bacteria. The three EPS producing bacterial isolates i.e. B. pumilus, B. globisporus and B. strearothermophilus were further confirmed through 16S rDNA sequence analysis. The culture and sensitivity (C/S) test results revealed streptomycin (S 10) as the most effective antibiotic to control the tested bacterial isolates. Plant Tissue Cult. & Biotech. 32(2): 145-156, 2022 (December)

Diversity and seasonal prevalence of starch hydrolysing, phosphate solubilizing and nitrogen-fixing bacterial groups of rooted and un-rooted regions of tropical mangrove sediments of Sundarbans, West Bengal, India

ABSTRACT The Sundarbans mangrove is a transitional zone between terrestrial land and sea, a unique location in our global geography. This study identifies the richness and population dynamics of bacterial populations along different seasons in the rooted and unrooted regions of soil sediments in Sundarbans, West Bengal. Throughout the year, bacterial populations were higher in the rooted sediment zone, than the unrooted area. The rooted zone contains more silt and clay but the unrooted zone harbours more silty, sandy soil. Salinity is lower in the unrooted zone. The heterotrophic bacterial populations were higher than other types of bacteria in both regions irrespective of seasonal variation. The results revealed that the most varied seasons were the monsoon season in the rooted and unrooted sediment region. The changes identified in this study were most likely due to variances in the microhabitat associated with mangrove root, physicochemical parameters and seasonal fluctuations.

Sustainable livelihoods and household participation in agroforestry: a case study adjacent to the Sundarban reserve forest in Bangladesh

Sustainable livelihoods and household participation in agroforestry: a case study adjacent to the Sundarban reserve forest in Bangladesh