Indian Sundarbans Research Articles

Securing the sustainable future of tropical deltas through mangrove restoration: Lessons from the Indian Sundarban

Securing the sustainable future of tropical deltas through mangrove restoration: Lessons from the Indian Sundarban

Estimation of Chlorophyll-a, TSM and salinity in mangrove dominated tropical estuarine areas of Hooghly River, North East Coast of Bay of Bengal, India using sentinel-3 data

The study aims to assess variations in spatio-temporal characteristics of water quality parameters from three tropical estuaries, namely Muri-Ganga, Saptamukhi, and Hooghly, in the western portion of the Indian Sundarbans. Reliable retrieval of near-surface concentration of water quality parameters such as Chlorophyll-a, SST & TSM from diverse aquatic ecosystems with broad ranges of tropical requirements has always remained a complex issue. In this study, application of Case 2 Regional Colour Correction (C2RCC) processor has been tested for its accuracy across different bio-optical regimes in both inland and coastal waters. Satellite images for the same period were also collected and analysed using the C2RCC processing sequence to retrieve parameters like the depth of water, surface reflectance, water temperature, inherent optical properties (IOPs), chlorophyll-a, salinity, total suspended matter (TSM), etc., using the SNAP software. In situ sampling from specific locations within these estuaries and water quality analysis were conducted for the period 2017–2019. The OLCI retrieved datasets were compared and corroborated with field survey datasets. It was observed that the highest amount of TSM was recorded at Diamond Harbour during the 2018 pre-monsoon season (301.40 mg/L field-based value and 308.54 mg/L estimated value). Similarly, chlorophyll-a had higher concentrations throughout the monsoon season (3.03 mg m−3, (field survey), and 2.96 mg m−3, (estimated) at Fraserganj and Sagar south points. A very good correlation was observed for all seasons for Chl-a (r = 0.829) and TSM (r = 0.924) between the OLCI data and in situ measurements. Higher correlation and significant ‘r’ values highlight the importance of having both field-based as well as remotely-sensed information in understanding any dynamic system in a sustained manner. Results also confirm that the water quality model using OLCI Chl-a and TSM products outperforms conventional techniques. The study demonstrates the efficacy of using Sentinel 3 OCLI data for shallow marine and estuarine remote sensing applications, especially for monitoring TSM and Chl-a concentrations.

Cyclone-induced coastal vulnerability, livelihood challenges and mitigation measures of Matla-Bidya inter-estuarine area, Indian Sundarban.

Indian Sundarban is highly susceptible to tropical cyclones and resultant impacts such as storm surge-induced floods, embankment breaching, and saline water intrusion. It affects life and livelihood in severe ways. Mitigation and policy measures are therefore very important, based on information gathered at the grassroots level. Hence, this study is designed to assess inter-village variation in cyclone vulnerability, considering physical vulnerability, social vulnerability, and mitigation capacity. This study also highlights livelihood challenges faced by coastal dwellers. Geospatial and quantitative methods were used to assess the composite vulnerability index (CVI). Remote sensing data and climatic data were integrated to assess physical vulnerability and various socioeconomic data were incorporated to determine the social vulnerability. Moreover, an intensive field survey (2020-2021) was also conducted to understand the livelihood challenges of local people and accordingly suggest mitigation measures to cope with natural hazards. According to this analysis, nearly 18% of the total population living in the southern and eastern parts of the Matla-Bidya inter-estuarine area (MBI) are extremely vulnerable (CVI > 0.544) due to their geographical location and high exposure to coastal hazards. Almost 51% of the total populations inhabited in 46% of the total MBI villages are experiencing high to moderate vulnerability. Conversely, MBI villages in the northern part, where 32% of the total population lives, show low vulnerability (CVI < 0.387) due to less exposure and high resilience. Coastal low-lying villages are often hardest hit by tropical cyclones. Therefore, effective mitigation strategies and coping mechanisms are essentially needed to reduce the adverse impacts of cyclones.

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.

Developing micro level resilience index for Indian Sundarban adopting resilience indicators for measurement and analysis (RIMA) methodology

• Communities along West Bengal coast devastated by cyclone-induced multi-hazards. • To comprehend the resilience strategy, four pillars of RIMA-II have been explored. • Villages affected differently and bounce back diversely. • Vulnerability and risk exposure are negatively correlated with the resilience index. Tropical cyclones induced multi-hazards have wreaked havoc on coastal communities in the last two-three years in coastal West Bengal, India. This research article aims to highlight the essence of these people's resilience to cyclone induced multi-scale hazards focusing on the Kakdwip Subdivision of Coastal West Bengal (Indian Sundarban Portion). Indicators in explaining RIMA-II, four pillars have been examined: Access to Basic Services (ABS), Assets (AST), Social Safety Nets (SSN) and Adaptive Capacity (AC). A total of 18 indicators from four pillars have been considered (6 from ABS, 4 from AST, 3 from SSN, and 5 from AC) and associated data has been gathered through a primary survey. In order to fully understand the village level scenario, the study has also used the Resilience Capacity Index (RCI). With the exception of Kuemuri, which is located in the far north-eastern part of the research area and is the most resilient, the study's findings show that the villages with a higher score (>56.81) are more resilient than others and are typically found in the section of Kakdwip Sub-northern Division. The least resilient settlements are clearly identified by their geomorphological location. Additionally, the resilience index shows a favourable relationship with the demographic index and a negative relationship with vulnerability and hazard exposure.

Assessing the cropping intensity dynamics of the Gosaba CD block of Indian Sundarbans using satellite-based remote sensing

Assessing the cropping intensity dynamics of the Gosaba CD block of Indian Sundarbans using satellite-based remote sensing

Sustainability assessment of Indian Sundarban delta islands using DPSIR framework in the context of natural hazards

Since the inception of the concept, sustainability has been interpreted as encompassing social, economic, and environmental dimensions of it. It is now rapidly shifting from a concept to a measurable state of the human-ecological dynamic system. Recent research is focusing on an integrated approach, due to the absence of a perfectly defined sustainable condition with the presence of some driving forces in the environmental system as a reference. In the recent world, severe natural hazards are increasingly having a fatal impact on societal and economic strata. The islands of Indian Sundarban Delta are the focus of this study as their sustenance is highly at stake due to climate change induced sea level rise, cyclone, tidal surge, and severe land erosion. The main objective of this study is to design a model for obtaining a composite sustainability index of three adjacent islands of western part of Indian Sundarban Delta (ISD) Sagar, Mousani and Ghoramara which are facing severe hazard impact based on the ‘Driving Force-Pressure-State-Impact-Response’ (DPSIR) framework integrating all three dimensions. Indicators have been categorised into state indicators and driving forces under ten profiles chosen from three dimensions of sustainability. The impact score of driving forces over any profile has been considered as a product of values of drivers and states from that profile. The total sustainability score was attained by summarizing the impact scores assigning the same weights and different weights respectively, to the sustainability indicators. The sustainability score shows that Sagar is in a better position than the other two islands.

A novel coupled framework for detecting hotspots of methane emission from the vulnerable Indian Sundarban mangrove ecosystem using data-driven models

Coastal mangroves have been lost to deforestation for anthropogenic activities such as agriculture over the past two decades. The genesis of methane (CH4), a significant greenhouse gas (GHG) with a high potential for global warming, occurs through these mangrove beds. The mangrove forests in the Indian Sundarban deltaic region were studied for pre-monsoonal and post-monsoonal variations of CH4 emission. Considering the importance of CH4 emission, a process-based spatiotemporal (PBS) and an analytical neural network (ANN) model were proposed and used to estimate the amount of CH4 emission from different land use land cover classes (LULC) of mangroves. The field work was performed in 2020, and gas samples of various LULC were directly collected from the mangrove bed using the enclosed box chamber method. Historical climatic data (1960–1989) were used to predict future climate scenarios and associated CH4 emissions. The analysis and estimation activities were carried out utilizing satellite images from the pre-monsoonal and post-monsoonal seasons of the same year. The study revealed that pre-monsoonal CH4 emission was higher in the south-west and northern parts of the deforested mangrove of the Indian Sundarban. A sensitivity study of the anticipated models was conducted using a variety of environmental input parameters and related main field observations. The measured precision area under curve of receiver operating characteristics was 0.753 for PBS and 0.718 for ANN models, respectively. The temperature factor (Tf) was the most crucial variable for CH4 emissions. Based on the PBS model with coupled model intercomparison project-6 temperature data, a global circulation model was run to predict increasing CH4 emissions up to 2100. The model revealed that the agricultural lands were the prime emitters of CH4 in the Sundarban mangrove ecosystem.

Block level annual and seasonal rainfall changes over Indian Sundarbans during 1901-2100

Block level annual and seasonal rainfall changes over Indian Sundarbans during 1901-2100

Block level annual and seasonal rainfall changes over Indian Sundarbans during 1901-2100

Block level annual and seasonal rainfall changes over Indian Sundarbans during 1901-2100

An Innovative Approach to Delineate and Differentiate Clear and Turbid Water Ponds in Indian Sundarban Area Using Sentinel-2 MSI Data

Pond water is the main source of irrigation in the Sundarbans area of West Bengal. The serious issues faced in agricultural lands and ponds are due to salinity. As salinity cannot be detected on high scales through satellite images, in this study the remotely sensed turbidity has been compared and studied with laboratory-measured salinity. The high-resolution Sentinel-2 MSI data with optimum bands for water quality detection have been used in this study. The small agricultural ponds in the study area were not detected by the conventionally used water indices, as the ponds were surrounded by homestead vegetation. Hence, a new index called Pond Probability Spectral Index (PPSI) was formulated and used in the decision tree algorithm to delineate all the ponds. Turbidity indices were used over the extracted ponds to classify them into three classes, clear, turbid and highly turbid. From the field accuracy assessment, one of the turbidity indices outperformed in segregating the ponds with an overall accuracy of 83.3%. It was also found that salinity was inversely proportional to turbidity only when the turbidity value was greater than 100 NTU. The total estimated pond area (average of 3 seasons) in the Sundarban region was 471.66 km2.

Assessing the Impact of Super Cyclone Amphan on Indian Sundarban Biosphere Reserve

Assessing the Impact of Super Cyclone Amphan on Indian Sundarban Biosphere Reserve

Whole-genome sequencing of biofilm-forming and chromium-resistant mangrove fungus Aspergillus niger BSC-1

Filamentous fungus Aspergillus niger has gained significant industrial and ecological value due to its great potential in enzymatic activities. The present study reports the complete genome sequence of A. niger BSC-1 which was isolated from Indian Sundarban mangrove ecosystem. The study revealed that the genome of A. niger BSC-1 was 35.1 Mbp assembled in 40 scaffolds with 49.2% GC content. A total of 10,709 genes were reported out of which 10,535 genes were predicted for encoding the proteins. BUSCO assessment showed 98.6% of genome completeness indicating high quality genome sequencing. The genome sequencing of A. niger BSC-1 revealed the presence of rodA and exgA genes for initial adhesion to surface and Ags genes for matrix formation, during biofilm growth. OrthoVenn2 analysis revealed that A.niger BSC-1 shared 9552 gene clusters with the reference strain A. niger CBS554.65. Semi-quantitative RT-PCR analysis unveiled the role of Ags1 and P-type ATPase in fungal biofilm formation and chromium (Cr) resistance, respectively. During biofilm growth the expression of Ags1 significantly (P < 0.0001; two-way ANOVA followed by Sidak's multiple comparisons test) increased with respect to planktonic culture revealing the possible involvement of Ags1 in biofilm matrix formation. Expression of P-type ATPase gene was significantly upregulated (P < 0.0001; one-way ANOVA followed by Dunnett's multiple comparisons test) with the increasing chromium concentration in the fungal culture. Besides, several other genes encoding metalloprotease, copper and zinc binding proteins, and NADH-dependent oxidoreductase were also found in the genome of A. niger BSC-1. These proteins are also involved in heavy metal tolerance and nanofabrication indicating that this filamentous fungus A. niger BSC-1 could be potentially utilized for chromium detoxification through biofilm or nanobiremediation.

Regional Environmental Change, Farmers’ Perceptions and Resilient Farming: Experiences from the Sagar Island of Indian Sundarbans

This research analyzed the patterns of agricultural transformations and adjustments to rapid environmental changes in deltaic island ecosystems by considering the case of Sagar Island of Indian Sundarbans using decadal climatic datasets, geospatial information, and farmers’ perceptions. Farmers’ cognition was considered for identifying crops that were suitable for cultivation in the changing environment. Results indicated that the average annual temperature and precipitation in this region had increased notably since 1980. Similarly, surface soil salinity had also recorded an overall increase throughout the island during the last three decades. In such a scenario, local farmers were only able to profitably cultivate few salinity-tolerant varieties of paddy (e.g., Masoori, Kalma, Santoshi, and Pratiksha) and vegetables (e.g., sunflower, potato, onion, okra, and betel leaf). Brackish water aquaculture had also become popular here in spite of its socio-ecological detriments. Many farmers were found to use their traditional knowledge proficiently alongside modern methods. However, the pressure of local peers, lack of readily investable wealth, and appropriate technological expertise often weakened their adaptive capacity. The findings suggested that effective cropping strategies such as coupled mangrove-shrimp farming and cultivation of salinity as well as waterlogging tolerant crop varieties could be considered as viable strategies toward enhancing resilience.

Delineation of Mangrove Patches using Multiple Landsat-8 OLI-based Indices: A Case Study of Indian Sundarban and Surroundings

Delineation of Mangrove Patches using Multiple Landsat-8 OLI-based Indices: A Case Study of Indian Sundarban and Surroundings

Batch adsorption and process optimization for sequestration of Cr(VI) from aqueous solution using biofilm forming filamentous fungus Aspergillus niger BSC-1

Chromium (Cr) contamination in an aquatic environment is one of the greatest concerns nowadays. However, biosorption by various microorganisms is proven to be an environmentally sustainable method. The present study investigated fungal biofilm-mediated sorption of hexavalent chromium [Cr(VI)] using manglicolous filamentous fungus Aspergillus niger BSC-1 obtained from the Indian Sundarban mangrove ecosystem. Biosorbents, such as fungal pellet and fungal biofilm, were utilized for Cr(VI) sequestration. The result showed significantly higher removal of Cr(VI) by fungal biofilm (97.81 ± 2.5 %) than the fungal pellet (79.14 ± 2.4 %) (P < 0.05; two-way ANOVA). Batch adsorption study showed that the highest removal efficiency was attained at 40 °C and pH 3 with 3 g/L of fungal biofilm. The adsorption isotherms, kinetics and thermodynamic analysis suggested monolayer, endothermic and chemisorption of Cr(VI) on the fungal biofilm biosorbent. The adsorption process was further optimized using response surface methodology (RSM) - Central Composite Design (CCD), suggesting the quadratic model for Cr adsorption with high significance (P < 0.0001). The 3D surface plots among the three key variables, i.e., pH, temperature and Cr concentration, revealed that maximum sequestration (92.39 %) was achieved at 40 °C, pH 3 and 30 mg/L of Cr(VI) using 3 g/L of fungal biofilm. Regeneration study demonstrated that fungal biofilm retained 87.19 ± 3.23 % of Cr(VI) sorption with no significant reduction in Cr(VI) removal after five successive adsorption-desorption cycles. X-ray photoelectron spectroscopic analysis showed that adsorption, reduction and complexation mechanisms were involved in Cr(VI) detoxification. Furthermore, the fungal biofilm biosorbent efficiently removed approximately 100 % of Cr(VI) from leather effluent within 90 min of reaction time.

Analyzing the multi-hazard coastal vulnerability of Matla–Bidya inter-estuarine area of Indian Sundarbans using analytical hierarchy process and geospatial techniques

In the current global climate change era, the Indian Sundarbans Delta (ISD) is severely exposed to multiple environmental disasters especially high-intensity tropical cyclones, storm surges and flood inundation. These disasters threaten the lives and livelihoods of coastal communities. To formulate a disaster risk reduction strategy, it is necessary to identify priority areas based on their level of vulnerability. Therefore, this research aims to assess the multi-hazard coastal vulnerability of the Matla–Bidya Inter-estuarine (MBI) area of ISD considering exposure, sensitivity, and adaptability. The coastal vulnerability was derived in this study based on a total of 26 indicators using the analytical hierarchy process (AHP) in combination with remote sensing data and geospatial techniques. To better understand the impacts of recent natural disasters, a field survey was conducted in each village from 2020 to 2021 to collect information directly from households regarding the effects of recent disasters on the different aspects of livelihoods. The present study found that the coastal villages in the Basanti and Gosaba Blocks located within the southern MBI are the most vulnerable due to coastal proximity, tropical cyclones, storm surges and flooding incidents. The high exposure and sensitivity cause potential effects on coastal environments and a lack of resistance to environmental disasters, leading to a considerable increase in coastal vulnerability. Local people's livelihoods are at risk in almost 33% of MBI villages. In contrast, villages in the northern MBI, in the Canning II Block are less susceptible to the effects of extreme events due to better resilience. This village-level multi-hazard vulnerability study helps to identify priority areas considering the vulnerability level of each village and accordingly proposed effective strategic planning for environmental and socio-economic resilience.

Erosion-accretion pattern in the tidal-rivers of Indian Sundarban in relation to estuarine hydrodynamics

Mapping the changes in the deltaic-coastal zone under changing hydrodynamic conditions is crucial for developing a concise picture of coastal vulnerability. The present study provides a comprehensive idea of changing scenario of rivers in the world's largest delta-Sundarban, using a variety of remotely sensed data and measurements, and relating these changes to hydrodynamic conditions. Bathymetric changes have also been estimated using Landsat imageries, calibrated with bathymetric chart data. We document a substantial dynamic variation between western and eastern sections of the Sundarban tidal rivers, as well as between the northern and southern parts. As such, banks adjoining the Saptamukhi and Thakuran rivers in the west have accreted by +43.48 ​km2 and +6.13 ​km2 respectively, while the net change in the eastern rivers like Matla, Gosaba, and Hariabhanga river systems shows a loss of −51.54 km2, –13.92 km2, and –13.82 km2, respectively, over the last century. Erosion rates have decreased from the southern seafront zone to the northern interior parts due to the low wave exposure, and high tidal range. The accretion rate has increased on the same ground. The depth of these rivers has also changed significantly. For instance, the depth of most sections along the Thakuran river has increased from 5 to 7 m to about 7–10 m during the period 1987–2016. The findings of this study will help researchers all around the world in understanding the centurial dynamics of tidal rivers, and by comparing these to other deltas, it will be possible to emphasize the relative vulnerability of major deltas to current sea level rise.

Anthropogenic impact accelerates antibiotic resistome diversity in the mangrove sediment of Indian Sundarban

Mangroves are situated in convergence zones between fresh and marine water and are prone to pollution and deforestation. This study explored the microbiome structure, function and antibiotic resistome of Indian Sundarban. The taxonomic Chao1 estimated diversity was highest in uninhabited Kalash (1204.64 ± 12.72) and lowest in Godkhali, which experiences considerable human activities (1158.76 ± 11.18). The alpha diversity showed negative correlation (p < 0.05) with PAH such as Acenaphthene (r = −0.56), Acenaphthylene (r = −0.62), Fluoranthene (r = −0.59), Fluorene (r = −0.55), Phenanthrene (r = −0.57), while the biochemical parameters phosphate (r = 0.58) and salinity (r = 0.58) had a significant (p < 0.05) positive correlation. The data suggest the importance of physicochemical parameters in maintaining the mangrove microbiome. The taxonomic composition was dominated by Proteobacteria (54.12 ± 0.37). All sites were dominated by ARGs such as rpoB2, cpxR, ompR, camP, and bacA. Comparing the Sundarban mangrove sediment resistome with mangrove from other sites in India (Kerala) and China (Guangxi, Hainan, and Shenzhen) suggested that resistome from Indian mangrove has a significantly (p < 0.05) higher ARG diversity compared to Chinese mangroves. Yet, the abundance of the ARG was significantly (p < 0.05) lower in the Indian mangroves posing a much greater risk if enriched. The study suggests that anthropogenic activities and pollution degrade the microbiome diversity, disturb the microbiome functions, and enrich ARGs.

Organic Farming in the Tropical, Disaster-Prone Coasts: Interventions, Major Challenges and a Success Story from Sundarban Biosphere Reserve, India

Organic agricultural practices are sustainable alternatives to chemical methods. This article highlights the major challenges faced by environmentalists, social workers in popularizing organic agriculture as well as its positive field application. The primary soil parameters (pH, alkalinity, electrical conductivity, soil, organic carbon, soil texture, and available N, P and K) are compared between global coastal agricultural soils. Organic farming practices adopted in different regions were also focused in this article. Sundarbans is the world’s largest contiguous mangrove ecosystem, largest delta, abode of mangrove dwelling tigers and Indian part is the home of 4.6 million natural disaster vulnerable populations. This work showcases success story of organic farming by 84 families of Indian Sundarbans since 2012, with use of vermicompost, biopesticides (neem oil) and natural microbe augmentations (Trichoderma sp), as a part of a socio-environmental intervention project. This intervention resulted in increased yield in both kharif season (10-12%) and rabi season (5-10%) by 2017.