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The aim of this study was to assess probabilistic human health risk due to ethnobotanical usage of Avicennia officinalis, Porteresia coarctata and Acanthus ilicifolius. The study was conducted at the tannery outfall near Sundarban (Ramsar wetland, India) mangrove ecosystem affected by potentially toxic elements (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn). Total metal concentrations (mg kg-1) were considerably higher in the polluted rhizosphere namely, Cd (1.05–1.97), Cu (36.3–38.6), Cr (144–184), Hg (0.04–0.19), Mn (163–184), Ni (37.7–46.4), Pb (20–36.6), and Zn (97–104). Ecological risk index indicated low to moderate ecological risk in this site, whereas the ecological risk factor showed high potential ecological risk due to Cd pollution. BCR Sequential extraction of metals showed more exchangeable fraction of Cd (47–55%), Cr (9–13%), Hg (11–13%), and Pb (11–15%), at the polluted site. Mercury, though present in trace amount in sediment, showed the highest bioaccumulation in all the three plants. Among the toxic trio, Hg showed the highest bioaccumulation in A. officinalis, Cd in P. coarctata but Pb has the lowest bioaccumulation potential in all the three species. Occasional fruit consumption of A. officinalis and dermal application of leaf, bark of A. officinalis (antimicrobial), A. ilicifolius (anti-inflammatory, pain reliever when applied on wounds) indicated negligible human health risk. However, long-term consumption of P. coarctata (wild rice variety) seeds posed health risk (THQ>1) both in adults and children age groups. This study concludes that nature of ethnobotanical use and metal contamination levels of the mangrove rhizosphere can impact human health. The transfer process of potentially toxic elements from rhizosphere to plants to human body should be considered while planing pollution mitigation measures.

In a tropical coastal environment, mangrove ecosystems store large amount of atmospheric carbon in biomass and soil. West coast of India host 29% of the mangrove ecosystems of the country. Putting aside the few scientific studies about the Indian mangroves system, there exist gaps in our scientific knowledge of Blue Carbon domain. This study aims to quantify the ecosystem carbon stocks potential and community structure of mangrove vegetation/ ecosystem species of Vypin– Cochin, a coastal region of the Southwest coast of India. The information on species-specific carbon storage will benefit to choose best species in the afforestation and conservation initiatives. Distribution, community structure and carbon pools of above and below ground biomass of the study area were assessed. From the analysis, it is evident that the amount of carbon stored in mangroves varies according to species, functional attributes (basal area, DBH, mean height etc.) and region. Avicennia officinalis, Rhizophora mucronata, Acanthus ilicifolius, Acrostichum aureum, Bruguiera cylindrica and Sonneratia caseolaris are the mangrove species observed from the study area. As per the community structure assessment, A. officinalis showed large number, frequency, density, and evenness. While considering biomass, R.mucronata species possess high value. The mean overall above ground biomass of the region was 69.55 ± 80.38 t ha−1. Ecosystem carbon stock of the area ranges from 17.7–138.8 with an average of 54.3 ± 36 t ha−1. Therefore, the findings described will serve as a baseline on carbon stock and mangrove stand structure of the region and their role in Blue Carbon dynamics of the Southwest Coast of India.

Mangroves adaptive plasticity in the changing environmental conditions is of vital importance for conservation management. Genetic diversity of mangrove brings about adaptive plasticity, enabling a species to cope with different habitat conditions. The Sundarbans of Bangladesh is the largest coastal wetland and mangrove forest with diversified habitat conditions that support a wide diversity of flora and fauna. Avicennia officinalis L. is the pioneer species in mangrove succession in the low-salinity, medium-salinity and high-salinity zones of the Sundarbans. Adopting RAPD-PCR analysis, the genetic diversity of A. officinalis was studied to explore the ecotypes of this species in the Sundarbans. The genetic distances of A. officinalis between the low-salinity and medium-salinity zones (0.50) and between the low-salinity and high-salinity zones (0.52) are significantly (p

Naturally grown mangrove forest is the south coastal community’s green barrier from any type of hydro-meteorological hazard and disasters. South-western coastal area of Bangladesh is covered by the Sundarbans, and mid-central zone is covered by Tengragiri wildlife sanctuary which is taken as a protected area in this recent era but not mapped properly with considering different species diversification and temporal changes pattern which is required for successful co-management of this mangrove forest. This study identifies species composition, plant diseases, degradation of the mangrove forests and further focuses on mapping mangroves by conducting plotting-based primary field visit, variability analysis using different indices and cross-matching with secondary databases. Existing mangrove forest boundary’s 200 m buffering with three-time series satellite imagery 2000, 2010 and 2017 is considered for further analysis. Including all buffering zone, this protected area considered 9 major classes that included four subclasses for presenting result like Baen (Avicennia officinalis), Gewa-Goran (Excoecaria agallocha, Ceriops decandra), Keora (Sonneratia apetala), Sundri (Heritiera fomes), Plantation trees Samanea Saman (Raintree), agriculture-grassland (agri-grass) and homestead settlement, sandbar and waterbody. Mapping accuracy assessment purpose automatically generated 996 points cross-matched with previously mangrove species level detailed survey results and found highest accuracy in Sundri species (70%) and all others above 50%. During 2000–2017, the Keora area showed the highest increase 129% over 2000 and increasing rate 13.17 ha/yr. About 26% Sundri and Baen–Passur increased around 13.45 ha/yr. In case of Sundri, 70% area coverage remained intact during 2000–2017, while other 25% classified in 2017 as Avicennia officinalis, Gewa-Goran classes. Furthermore, using refracted electromagnetic energy from various physical characteristics of plants application, four indices (NDVI, DVI, MSAVI-2, RVI) are usable where single-species-level crop density analysis has limitations, but identification of Sundri and Keora by MSAVI-2 and NDVI found significant and alternately lower accuracy values from RVI. Identification of dominant mangrove species groups as well as area gains and losses over 2000–2017 is a robust biophysical baseline for management of the sanctuary. Natural hearts of this area and working as first-step warriors against natural disasters originated from Indian Ocean and Bay of Bengal; so far, it is very much required to save this forest and the coastal communities as well. The results of the study and maps will be helpful for the scientific community, planners, government-international bodies and the activists, Forest Department and the local community in effective planning, monitoring the effectiveness of co-management in conservation of the sanctuary.

In Myanmar’s Ayeyarwady Delta, mangrove forests were widely converted to paddy fields, then abandoned. However, the mangrove ecosystems often fail to recover. To identify the mangrove restoration options in these fields, we conducted the current study in Pyindaye Forest Reserve, Pyapon Township of the Delta by examining the structural and functional responses to restoration for two common mangrove species (Avicennia officinalis and Bruguiera sexangula) after three post-abandonment periods (4, 8, and > 10 years), the natural recovery after these periods, and management to improve degraded forests dominated by the two species. Without replanting, we observed no mangrove cover or regeneration more than 10 years after abandonment. The sites were dominated by a perennial grass (Paspalum vaginatum), sparse climber, herbs, and spiny shrubs. With increasing the abandoned period, we observed decreasing soil quality and increasing vegetation cover by the grass, herbs, and spiny shrubs in response to increasingly harsh micro-environmental conditions for natural recovery of mangrove. Without human assistance, the abandoned paddy fields will not recover their productivity after more than 10 years. However, with increasing the period of establishing mangrove plantations in the abandoned fields, the ecosystem showed improved vegetation structure and regeneration of both planted and non-planted species. The soil conditions improved during mangrove recovery, and a well-developed canopy and aerial root system developed. By 8 years after mangrove establishment, the land could be used again as paddy fields due to suppression of P. vaginatum and the improved micro-environment. The managed forests showed the best structural attributes, conditions for regeneration, and micro-environmental conditions for plant growth and regeneration. Our results suggest three options for managing the abandoned paddy fields: paddy cultivation based on fallow periods with mangrove establishment, mangrove planting for wood production, and mangrove planting for environmental restoration.

The mangroves of Andaman and Nicobar Islands are considered as one of the finest vegetation in India with respect to species composition as well as structure. However scientific information on the influence of edaphic attributes on the structure of Andaman mangroves are lacking. Hence, we assessed the floristic composition, structural attributes, zonation pattern and its relation to edaphic variables of mangroves of the Andaman islands. Quadrat method was employed to estimate the different structural variables and multiple regression analysis to explain the influence of edaphic variables over structural attributes. Floristic analysis of 420 quadrats (10x10m) revealed a mixed species composition with 28 true mangroves in Andamans, of which Avicennia officinalis, Rhizophora apiculata, and R. mucronata were designated as the most important species based on the importance value index. Stem density varied from 133 to 14,000 ha−1 and individual basal area 0.07–78.75 m2 ha−1, further, most of the mangrove habitats showed very high stand basal area. Relatively higher Maturity Index Value was observed indicating high structural maturity in Andamans. Species zonation pattern typically varies based on the tidal inundation. Multiple regression analysis revealed the importance of soil pH, silt, total carbon, total Nitrogen and salinity in shaping the structure of Andaman mangroves. The data evolved in the study would be valuable in the site-specific management and conservation approaches of mangroves in Andamans.

The present study was aimed at evaluating the antidiabetic activity of the ethanol bark extract of a mangrove plant Avicennia officinalis (AOEB) in streptozotocin (STZ)-induced diabetic mice. The study revealed AOEB could lower the blood glucose level significantly (p

The present study involves biosynthesis of AgNPs using Avicennia officinalis and Xylocarpus granatum mangrove plants along with evaluation of their potential biomedical applications. The synthesized AgNPs were characterized by UV–Vis spectroscopy, FTIR analysis, scanning electron microscope, particle size analyzer, X-ray diffraction (XRD). The synthesized AgNPs showed absorption maxima at 470 nm for X. granatum (XG-AgNPs) and 420 nm for A. offcinalis (AO-AgNPs) which corresponds to their respective surface Plasmon resonance. The FTIR analysis reveals capping of phenolic groups providing stability of synthesized AgNPs. The morphology of silver nanoparticles was confirmed by SEM technique. The dynamic light scattering study (DLS) also confirmed the size distribution of synthesized AgNPs. XRD peaks at 2θ range of 20–70o corresponds (111), (200) and (220) reflection planes indicating the structure of metallic silver. AO-AgNPs exhibited better DPPH scavenging, superoxide and protein denatuaration activity with IC50 values of 0.14, 0.32 and 0.21 mg/ml. However, XG-AgNPs exhibited better α-amylse and α-glucosidase inhibition potential as compared to AO-AgNPs. It could be concluded that X. granatum bark extracts and A. officinalis leaf extract can be used efficiently for the synthesis of biologically active silver nanoparticles which could be exploited pharmaceutical applications.

Urban development is driving the loss and subsequent fragmentation of mangrove forests in Penang, Malaysia. However, little research has focused on the implications of urbanization onto the biodiversity within mangrove forests. This study investigates and compares both vegetation and crab assemblages between urban and rural mangrove forests. Collectively, 5853 trees were recorded including 15 species from six families: Acanthaceae, Arecaceae, Lythraceae, Malvaceae, Meliaceae, and Rhizophoraceae. Avicennia marina accounted for 88.6% of all trees in the study and held the highest species importance (IV). Although the total number of mangrove tree species varied significantly between urban (14) and rural (7) mangrove forests, the mangrove forest structure based on IV did not vary significantly. In total, 633 crabs were recorded comprising 13 different species from three superfamilies: Grapsoidea, Ocypodoidea, and Paguroidea. Crab species richness did not vary between urban and rural sites, but the biomasses of five and the densities of four crab species varied significantly. Redundancy analysis (RDA) indicated that land use, salinity, and abundance of Avicennia officinalis can best describe the distribution of crab species (r2 =32.7). This study indicates that smaller fragmented urban mangroves at the east coast of Penang have a relatively high tree and crab diversity and are worth protecting, in addition to the larger mangrove forests on the west coast. The preservation of small yet interconnected mangrove sites could be critical to the recruitment of their flora and fauna and should be considered in decision-making processes.

Salinity is an environmental stress that causes decline in crop yield. Avicennia officinalis and other mangroves have adaptations such as ultrafiltration at the roots aided by apoplastic cell wall barriers to thrive in saline conditions. We studied a cytochrome P450 gene from A. officinalis, AoCYP94B1, and its putative ortholog in Arabidopsis (Arabidopsis thaliana), AtCYP94B1, which are involved in apoplastic barrier formation. Both genes were induced by 30 min of salt treatment in the roots. Heterologous expression of AoCYP94B1 in the atcyp94b1 Arabidopsis mutant and wild-type rice (Oryza sativa) conferred increased NaCl tolerance to seedlings by enhancing root suberin deposition. Histochemical staining and gas chromatography-tandem mass spectrometry quantification of suberin precursors confirmed the role of CYP94B1 in suberin biosynthesis. Using chromatin immunoprecipitation and yeast one-hybrid and luciferase assays, we identified AtWRKY33 as the upstream regulator of AtCYP94B1 in Arabidopsis. In addition, atwrky33 mutants exhibited reduced suberin and salt-sensitive phenotypes, which were rescued by expressing 35S::AtCYP94B1 in the atwrky33 background. This further confirmed that AtWRKY33-mediated regulation of AtCYP94B1 is part of the salt tolerance mechanism. Our findings may help efforts aimed at generating salt-tolerant crops.

The ability of mangrove trees to reproduce and disperse in highly dynamic tidal environments is reflected in the contemporary genetic diversity and structure of their populations. Resilience and establishment may occur through either local recruitment (propagule pool model) or over longer distances with mixed origins (migrant pool model), thereby affecting the connectivity between natural populations. Anthropogenic activities such as encroachment and fragmentation or from mitigating reforestation could cause strategy switches and thus the connectivity and genetic structure of populations. In this study, we considered Avicennia officinalis, a dominant component of the Sundarban mangrove forest in Bangladesh to estimate dispersal dynamics over various distances within estuaries. A total of 423 individuals of A. officinalis, distributed over thirteen sites in the Sundarbans were sampled at both large and fine-scaled spatial level, the latter for comparison of natural and dense with fragmented sites. Up to 62 alleles showed a comparable level of allele diversity and gene diversities at both juvenile and adult life stages, assuming overall high levels of outcrossing. Significant inbreeding levels and high kinship values were solely observed at a reforested A. officinalis site. Genetic variables revealed high levels of connectivity between sites at close vicinity, with only a weak structure over larger geographic distances, between natural core Sundarban and coastal edge populations. Kinship coefficients were mostly low though significant up to several kilometers along estuarine branches, thereby suggesting propagule dispersal beyond each site. A fine-scaled analysis of kinship levels estimated for fragmented and natural forest plots along both sides of a river revealed that fragmentation induced higher kinship levels over 25–50 m distance, whereas dense natural populations were composed of less related individuals at shortest distances. A. officinalis populations might stay resilient through a mixture of unrelated propagules, clearly adhering a migrant pool model in natural sites and propagule pool model in fragmented sites. A poor gene diversity of planted trees might jeopardize the sustainability of mangrove plantation practices. Furthermore, high levels of diversity and connectivity indicated that the core Sundarban populations are a relevant source of germplasm in afforestation programmes.

Nutrient resorption efficiency is an important nutrient conservation and ecophysiological mechanism of mangroves growing in saline environments. This study investigated the nitrogen, phosphorus, and potassium resorption efficiency of Avicennia officinalis L. growing across a salinity gradient with seasonal variations in the Sundarbans of Bangladesh. Due to decreasing salinity during the monsoon and postmonsoon seasons, the nutrient availability in soil and nutrient resorption efficiency did not vary significantly among the low-salinity, medium-salinity, and high-salinity zones. However, the nutrient availability in the medium-salinity and high-salinity zones was significantly lower than that in the low-salinity zone during the premonsoon season due to increased salinity. Consequently, nutrient resorption efficiency in the medium-salinity and high-salinity zones was significantly higher than that in the low-salinity zone during the premonsoon. Further, leaf vein density of A. officinalis in the medium-salinity and high-salinity zones was significantly higher than that in the low-salinity zone. This modification in vein density was the mechanism for the higher nutrient resorption efficiency of A. officinalis in the medium-salinity and high-salinity zones than that in the low-salinity zone. This plasticity in nutrient resorption efficiency is a physiologically adaptive mechanism that enables A. officinalis to persist in increasingly saline environments due to climate change.

Spatial distribution of potentially toxic metals (PTMs) and their accumulation in mangrove Avicennia officinalis L. were studied along 8 locations in and around Sundarban mangrove wetland, India. Among 8 locations, S3 (Chemaguri) and S5 (Ghushighata) showed higher concentration of PTMs (Cd, Cr, Cu, Ni, Pb, Zn) characterized by higher enrichment factors (3.45-10.03), geo-accumulation indices (0.04-1.22), contamination factors (1.14-3.51) and pollution load indices (1.3-1.45) indicating progressive deterioration of estuarine quality and considerable ecotoxicological risk. Metal concentration in A. officinalis leaves showed significant correlation with sediment metals implying elevated level of bioaccumulation. Significant statistical correlation between photosynthetic pigments (Chlorophyll a, Chlorophyll b), antioxidant response (free radical scavenging and reducing ability) and stress enzymatic activity (Peroxidase, Catalase, Super-oxide dismutase) of A. officinalis with increasing metal concentration in the contaminated locations reflects active detoxification mechanism of the plant. The study indicates the potentiality of biomonitoring metal pollution using studied biochemical markers in mangrove habitats.

In a mangrove environment, several groups of organisms are symbiotically associated with pneumatophores (aerial roots). But whether these organisms are exclusively found in this habitat (uniqueness) or accidentally settled here from water or sedimentary habitat, is not clearly understood. This hampers our understanding of their functional ecology. Hence the present study aimed to characterise the epibiotic microalga and meiofauna from the pneumatophores of mangrove Avicennia officinalis . To determine the habitat influence, these communities were also compared with those found in water and sedimentary habitat. Four estuarine mangrove sites represented by brackish water (salinity varying from 5 to 12) and located at different spatial scales (5–50 km distance) were chosen to determine whether these communities are consistent or vary with sites. Overall, the microalgal community was found to vary both among the habitats as well as sites. In the pneumatophore habitat, several tychoplanktons such as Coscinodiscus, Thalassionema , Cyclotella, Fragilariopsis, and Biddulphia were observed instead of benthic ones. These diatoms are planktonic genera and might have settled on pneumatophores from the water column. The observed variability in the microalgal composition among the sites is possibly due to predatory interactions or the dominance of particular species of macroalga that govern the diatom community. On the other hand, among the meiofaunal community, diptera, halacarida, tanaidacea, and foraminifera were mainly found in the pneumatophore habitat than in the sediment. Because pneumatophores either provide refugee to meiofauna against predators or are saturated with oxygen that meiofauna can utilize for respiration. Pneumatophores were also found to harbour several rare (abundance

Avicennia officinalis L. is a typical mangrove species, inhabiting inhospitable environments in the interface between sea and land. In this study, we generated RNA-seq data to de novo assemble the A. officinalis transcriptome. Starting with 36.24 million 100 bp paired-end reads, 38,576 high-confidence transcripts with an average length of 834 bp were produced after filtration of weakly expressed and redundant transcripts. We found known protein homologs for 22,254 of these transcripts, and assigned them to at least one of 119 gene ontology (GO) terms. In addition, we identified different copies and isoforms of three candidate genes, AoPIP, AoTIP and AoDHN1, which might be involved in salt excretion via salt glands. All these genes were highly expressed in leaf tissue of A. officinalis, suggestive of a complicated mechanism of response to salt stress. We further identified 613 microsatellite markers for the assessment of genetic diversity and population differentiation in A. officinalis. Genomic resources generated in this study would be an important foundation for future research into molecular mechanisms underlying salt and other stress tolerance, as well as the evolutionary history of this mangrove species and its relatives.

The species-specific potentiality of mangroves in terms of ecosystem services is not well understood. Therefore, this study addressed the carbon sequestration and litterfall production potentiality of six major species in Sundarbans, Bangladesh, by evaluating three consecutive years of inventory data, including the stand variables and weather events impacts on them. The total mean aboveground, belowground biomass, biomass accumulation, and carbon accumulation rate were 243.4 Mg ha−1, 132.2 Mg ha−1, and 14.3 Mg ha−1 yr−1, 7.2 Mg ha−1 yr−1, respectively. Carbon stocks and sequestration rates are significantly influenced by stand variables such as diameter, density, and species composition. Large-sized trees and stands with lower density sequester more carbon than small-sized trees, and higher density stands. Among species, Avicennia officinalis contributed higher carbon to carbon stocks and also significantly different from other species for sequestering carbon, whereas Aglaia cucullata was the lowest. Mean annual litterfall was 10.01 Mg ha−1 yr−1, with the maximum litterfall for Hereteira fomes (19.2 Mg ha−1 yr−1) during the late summer or wet season (e.g., April to August). Litterfall showed a significant positive (p

Adaptive phenotypic plasticity of Avicennia officinalis across the salinity gradient in the Sundarbans of Bangladesh was studied. Propagule morphology was compared through use of a completely randomized design. Propagule growth initiation traits across the salinity gradient (from 0 to 35 ppt at 5 ppt interval) were studied by means of a randomized block design. Propagules showed variability in length, width, and weight across the salinity gradient in the Sundarbans. Propagule growth initiation time, mean growth initiation time, growth initiation index, and propagule growth initiation percentage of A. officinalis varied significantly with the increasing salinity and among low, medium, and high saline zones. However, propagules originating from the high and medium saline zones started their growth initiation more rapidly and vigorously at high salinities compared to those from the low saline zone. Therefore, A. officinalis exhibited adaptive phenotypic plasticity in terms of variability in propagule size and weight as well as physiologically adaptive plastic responses during propagule growth initiation across the salinity gradient in the Sundarbans. A. officinalis in high and medium saline zones of Sundarbans is the most salt-adapted phenotype, and a good knowledge about this will be widely useful for successful regeneration, coastal afforestation, and conservation of this species in increasing saline environments in the future.

The stimulation or suppression of the immune response may modulate disease free state. Herbal medicine paved way for immunmodulation role in many mmunological disorder. The present study was aimed to prove the traditional claim on the theimmunomodulatory activity ofAvicenniaofficinalisagainst autoimmune diseases. TheAvicenniaofficinalis leaves was authentified and coarsely powdered then extracted successively with n-hexane,70% hydroalcohol followed by, ethylacetate. The phytoconstituentsofthe three extracts were analysed . Finally, all were subjected to (NBT) Nitrobluetetrazolium Assay, Candidacidal assay and Phagocytotic evaluation. The percentage yield and phytoconstituents of the extracts were determined. Among thethree extract, the ethanolic extract and Ethylacetateextractshowed effective immunomodulatory effect by their suppression of leucocytes and neutrophils. The results of the present study proved the immunomodulatory effect of Avicenniaofficinalis and further studies are essential to target this species against autoimmune diseases.

Background The article presents the first estimates of biomass and productivity for mangrove forests along the Oligohaline zone of the Sundarbans Reserve Forest (SRF), Bangladesh. This study was conducted overone year from March 2016 to April 2017. Stand structure, above and below-ground biomass changes, and litterfall production were measured within a 2100 m2 sample plot. Methods All trees in the study plots were numbered and height (H) and diameter at breast height (DBH) were measured. Tree height (H) and DBH for each tree were measured in March 2016 and 2017. We apply the above and belowground biomass equation for estimating the biomass of the mangrove tree species (Chave et al. Oecologia 145:87−99, 2005; Komiyama et al. J Trop Ecol 21:471–477, 2005). Litterfall was collected using 1-mm mesh litter traps with collection area of 0.42 m2. Net Primary Production (NPP) was estimated by the summation method of Ogawa Primary productivity of Japanese forests: productivity of terrestrial communities, JIBP synthesis (1977) and Matsuura and Kajimoto Carbon dynamics of terrestrial ecosystem: Systems approach to global environment (2013). Results Heritiera fomes has maintained its dominance of the stand and also suffered the highest tree mortality (2.4%) in the suppressed crown class. The total above-ground biomass (AGB) and below-ground biomass (BGB) of the studied stand was 154.8 and 84.2 Mg∙ha−1, respectively. Among the total biomass of the trees, 64.8% was allocated to AGB and 35.2% to BGB. In case of species-wise contribution of biomass allocation, Avicennia officinalis showed the highest score and Aglaia cucullata the lowest. Mean annual total litterfall was 10.1 Mg∙ha−1∙yr−1, with the maximum litterfall in winter or dry season and late summer or rainy season. The mean AGB increment and above-ground net primary productivity (AGNPP) were 7.1 and 17.2 Mg∙ha−1∙yr−1, respectively. Total net primary productivity (NPP) was estimated to be 21.0 Mg∙ha−1∙yr−1 over the observed period. The results in the Sundarbans mangrove forests exhibited that mangrove communities with similar height and diameter produced different biomass production with the different basal area. The present analysis revealed that the root biomass was large enough and the mean ratio of above−/below-ground biomass was estimated to be 1.84. Conclusions Mangrove communities growing at the oligohaline zone of the Sundarbans, Bangladesh showed high biomass and net primary production indicating their ecological and conservation significance that may be considered in future decision making process for the area as well as in understanding the role of Sundarbans mangrove forest on mitigating the effect of global warming.

Salinity affects growth and development of plants, but mangroves exhibit exceptional salt tolerance. With direct exposure to salinity, mangrove roots possess specific adaptations to tolerate salt stress. Therefore, studying the early effects of salt on mangrove roots can help us better understand the tolerance mechanisms. Using two-month-old greenhouse-grown seedlings of the mangrove tree Avicennia officinalis subjected to NaCl treatment, we profiled gene expression changes in the roots by RNA-sequencing. Of the 6547 genes that were differentially regulated in response to salt treatment, 1404 and 5213 genes were significantly up- and down-regulated, respectively. By comparative genomics, 93 key salt tolerance-related genes were identified of which 47 were up-regulated. Upon placing all the differentially expressed genes (DEG) in known signaling pathways, it was evident that most of the DEGs involved in ethylene and auxin signaling were up-regulated while those involved in ABA signaling were down-regulated. These results imply that ABA-independent signaling pathways also play a major role in salt tolerance of A. officinalis. Further, ethylene response factors (ERFs) were abundantly expressed upon salt treatment and the Arabidopsis mutant aterf115, a homolog of AoERF114 is characterized. Overall, our results would help in understanding the possible molecular mechanism underlying salt tolerance in plants.

Mangrove pneumatophores (respiratory roots) form a unique habitat about which very little ecological information is available. In this study, epiphytic diatoms on the pneumatophore surface of Avicennia officinalis (L.) were investigated with a focus on their seasonal and vertical distribution. The results indicated that among the seasons, highest diatom abundance was observed in monsoon. Vertically, maximum abundance was observed on 0–5 cm of the pneumatophore during post-monsoon and pre-monsoon and then gradually decreased upwards, but during monsoon, 5–10 cm section hosted maximum abundance. There was a seasonal and vertical variation on the diatom abundance and their interactive effect. This is because diatoms probably avoid the basal section (0–5 cm) of the pneumatophore during monsoon due to excessive sediment burial caused by intense riverine flux and settlement of suspended material. Overall it was found that vertically, diatoms (>70%) are mainly concentrated on the lower 0–10 cm of the pneumatophore, probably because this section remains moist during emersion period (low tide). Among the diatoms, Melosira nummuloides and Bacillaria paradoxa exhibited dominance during the monsoon, whereas Thalassiosira spp., Navicula spp., and Nitzschia spp.were prevalent during post- and pre-monsoon. To the best of our knowledge, this is the first study describing the composition of epiphytic diatoms from the pneumatophore surface of A. officinalis. Keeping in mind that these aerial roots together greatly enhance the surface area for attachment of epiphytic diatoms, their cumulative primary production would probably surpass that of mangroves on a quantitative basis and needs future investigation.

Expression of AoNHX1 from the mangrove Avicennia increases salt tolerance of rice and Arabidopsis, and specific bHLH transcription factors regulate AtNHX1 and AtNHX6 in Arabidopsis to mediate the salinity response. Improving crop plants to better tolerate soil salinity is a challenging task. Mangrove trees such as Avicennia officinalis have special adaptations to thrive in high salt conditions, which include subcellular compartmentalization of ions facilitated by specialized ion transporters. We identified and characterized two genes encoding Na+/H+ exchangers AoNHX1 and AoNHX6 from Avicennia. AoNHX1 was present in the tonoplast, while, AoNHX6 was localized to the ER and Golgi. Both NHXs were induced by NaCl treatment, with AoNHX1 showing high expression levels in the leaves and AoNHX6 in the seedling roots. Yeast deletion mutants (ena1-5Δ nha1Δ nhx1Δ and ena1-5Δ nha1Δ vnx1Δ) complemented with AoNHX1 and AoNHX6 showed increased tolerance to both NaCl and KCl. Expression of AoNHX1 and AoNHX6 in the corresponding Arabidopsis mutants conferred enhanced NaCl tolerance. The underlying molecular regulatory mechanism was investigated using AtNHX1 and AtNHX6 in Arabidopsis. We identified two basic helix–loop–helix (bHLH) transcription factors AtMYC2 and AtbHLH122 as the ABA-mediated upstream regulators of AtNHX1 and AtNHX6 by chromatin immunoprecipitation. Furthermore, expression of AtNHX1 and AtNHX6 transcripts was reduced in the atmyc2 and atbhlh122 mutants. Lastly, transgenic rice seedlings harboring pUBI::AoNHX1 showed enhanced salt tolerance, suggesting that this gene can be exploited for developing salt-tolerant crops.

Mangrove plants are endowed with various biologically active compounds which have potent antibacterial and antioxidant properties. In present study, a bioactivity-guided fractionation for antibacterial and antioxidant active metabolites from the twigs of Avicennia officinalis collected from Kuala Selangor Nature Park, Selangor, Malaysia gave 13 major fractions. The antibacterial activity of A. officinalis fractions using well-diffusion showed strong selectivity on the Gram-positive bacteria (Staphylococcus epidermidis, S. aureus and Bacillus subtilis) with minimum inhibition concentration (MIC) values of 0.156-5.00 mg/mL. However, no antibacterial activities were observed on the Gram-negative bacteria (Vibrio cholera, Enterobacter cloacae and Escherichia coli). The active antibacterial fractions were further isolated using several chromatographic techniques to give two naphthofuranquinones, namely, avicenol C (1) and stenocarpoquinone B (2). Meanwhile, the antioxidant activity of A. officinalis fractions were evaluated using DPPH radical scavenging assay exhibited low antioxidant activities. Molecular structure of the naphthofuranquinones was elucidated using 1 D and 2 D NMR spectroscopy.

Although studies on species-level classification and mapping using multisource data and machine learning approaches are plenty, the use of data with ideal placement of central wavelength and bandwidth at appropriate spatial resolution, for the classification of mangrove species is underreported. The species composition of a mangrove forest has been estimated utilising the red-edge spectral bands and chlorophyll absorption information from AVIRIS-NG and Sentinel-2 data. In this study, three dominant species, Heritiera fomes, Excoecaria agallocha and Avicennia officinalis, have been classified using the random forest (RF) model for a mangrove forest in Bhitarkanika Wildlife Sanctuary, India. Various combinations of reflectance/backscatter bands and vegetation indices derived from Sentinel-2, AVIRIS-NG, and Sentinel-1 were used for species-level discrimination and mapping. The RF model showed maximum accuracy using Sentinel-2, followed by the AVIRIS-NG, in discriminating three dominant species and two mixed compositions. This study indicates the potential of Sentinel-2 data for discriminating various mangrove species owing to the appropriate placement of central wavelength and bandwidth in Sentinel-2 at ≥10 m spatial resolution. The variable importance plots proved that species-level classification could be attempted using red edge and chlorophyll absorption information. This study has wider applicability in other mangrove forests around the world.

Mangrove forest are used widely for meeting fuelwood needs of local communities in the tropics. However, the implications of fuelwood extraction on mangrove ecology has received very little attention. In this study, we investigated the impact of such small-scale fuelwood harvesting practices on mangrove forest structure, composition, regeneration, and biomass and carbon stocks in a protected area on the east coast of India. We sampled vegetation plots in areas where harvesting was practised and where no harvesting was observed. We found that species composition differed across forest categories with Exoecaria aggalocha and Heriteria fomes dominating non-harvested forest types and Sonneratia apetela, Sonneratia caseolaris, Avicennia officinalis along with mangrove associates comprising a large proportion of harvested mangrove forests. Similarly, tree, sapling and seedling densities, basal area, and biomass and carbon stocks were also found to vary across forest categories, with overall lower values observed in harvested areas. Lastly, total aboveground (11%) and belowground (18%) biomass and carbon stocks were also lower in harvested forests than non-harvested forests. However, large DBH size-class trees were found in harvested areas implying selective cutting practices that conserved old-growth trees and contributed to larger mean carbon pools. As harvesting is selective, mainly for cooking fuel demands, integrated management plans are required to accommodate local cultural and economic needs of the communities in this region.

This study shows results on litterfall dynamics contributing to Net Primary Productivity (NPP) and phenology in three major mixed mangrove habitats in Cochin estuarine system, south-west coast of India. Eleven true mangrove species and three mangrove associates formed the plant biomass where Avicennia officinalis was abundant in Site 1, Excoecaria agallocha in Site 2 and Avicennia officinalis , Rhizophora mucronata were abundant in Site 3. Total tree density varied from 11760 stems ha −1 in Vypin Island (Site 2); 11440 stems ha −1 in Mangalavanam Bird sanctuary (Site 3) and 7680 stems ha −1 , Aroor (Site1). The average stands basal area of the three mangrove habitats were 75.54, 54.85 and 103.26 m 2 ha −1 . The mean annual litterfall production in Cochin mangroves was 16.57±6.58 t ha −1 y −1 in which leaves (53.90%) contributed more followed by flowers, propagules (28.66%) and twigs (17.44%). The spatial variability in litterfall recorded highest in lower latitudinal mangrove habitat, Site.1 followed by Site 2 and Site 3 (2413.36 ± 873.72, 1295.65 ± 401.09, 1263.28±255.28 g DW m −2 y −1 ). Site differences in litter production were statistically significant (one-way ANOVA p 0.001 for total litterfall and p 0.05 for litter components) between the three mangrove habitats. Litter components and total litterfall showed significant seasonality ( p 0.001 ). Highest litterfall was recorded in pre-monsoon period followed by post-monsoon and least in monsoon period. The temporal trend of litterfall was explained through rainfall and mean atmospheric temperature and a negative correlation was there to rainfall during the period. The mean carbon content in the litterfall was estimated as 42.96% of the dry weight and the primary productivity through litterfall in the study area was estimated to be 7.12±2.81 t C ha −1 y −1 . This will act as the major source of carbon input to the mangrove ecosystem and surrounding coastal ecosystems and in turn reflected in NPP.

There are few studies that dealt with species preference in seedling predation by sesarmid crabs in mangrove forests. We investigated predation preference of the sesarmid crab Neosarmatium malabaricum to the seedlings of Aegiceras corniculatum, Avicennia officinalis, Excoecaria agallocha and Rhizophora mucronata in Kunhimangalam mangrove forest in Kerala. Enclosure-exclosure experiments showed that the crab preferred seedlings of E. agallocha the most and that of R. mucronata the least. Reason for this preference was the cumulative effect of morphological and chemical factors of these seedlings. Morphological factors negatively and chemical factors positively influenced the predation preference. Species preference in seedling predation could be inversely proportional to relative abundance and density of saplings. Saplings of the most preferred A. corniculatum and E. agallocha registered low density, and the least preferred R. mucronata and A. officinalis recorded high density in Kunhimangalam mangrove forest. Species preference exhibited by N. malabaricum in seedling predation has been reflected in sapling density and composition. So, this preference can possibly influence the future forest composition.

Absorption, accumulation and translocation of 12 trace elements in nine dominant mangrove plants in the Indian Sundarban Wetland revealed both organ-specific and site-specific characteristics. An overall enrichment of elements was recorded in rhizosediment, exceeding the prescribed effects range-low (ER-L) of consensus based sediment quality guidelines (SQGs) for Cu and Pb. Avicennia officinalis, A. alba, Ceriops decandra and Excoecaria agallocha exhibited unique potential for accumulating Al, Cd, Co, Cr, Cu, Ni, Mn and Zn and could be considered efficient accumulators. Maximum element accumulation in trunk bark (As 6.16, Cr 49.9, Co 2.67, Cu 91.00 and Zn 85.5 mg kg−1) and root/pneumatophore (Al 1000 and Fe 2430 mg kg−1) was recorded. Maximum bioconcentration factor (6.23) in A. officinalis and translocation factor (17.5 for Mn) in C. decandra distinguished their phytoremediation capacity. These halophytes could be used for trace element phytoremediation in stressed sites of Sundarban.

The objective of this present attempt was to investigate the relationship between leaf quality and level of herbivory at study site during August 2010–July 2011. Total amino acids with a maximum of 9.47 mg g −1 during February 2011 in Rhizophora mucronata and a minimum of 4.671 mg g −1 in May 2011 in Avicennia officinalis were noticed. Tannin was maximum (6.844 mg g −1 ) during April 2011 and minimum (0.667 mg g −1 ) in July 2011 in A. officinalis . Total nitrogen showed a maximum of 9.851 mg g −1 during February 2011 in R. mucronata and a minimum of 2.158 mg g −1 in February 2011 in A. officinalis . Total sugars registered a maximum of 4.075 mg g −1 during March 2011 in A. officinalis and a minimum of 0.063 mg g −1 in March 2011 in R. mucronata . Total phosphorus recorded the maximum (4.321 mg g −1 ) during November 2010 in R. mucronata and minimum (0.258 mg g −1 ) during May 2011 in A. officinalis . Potassium content was maximum (3.710 mg g −1 ) during October 2010 in R. mucronata and minimum (0.039 mg g −1 ) in July 2011 in A. officinalis . These data suggest that artificially developed mangrove ecosystems may be an adaptive mechanism related to nutrient conservation, and that it is associated with mangrove survival in phosphorus-deficient soil rather than an adaptation to herbivory.

The Sundarbans, the largest mangrove forest in the world and a UNESCO world heritage site has been facing increasing pressure of habitat destruction. Yet, no study has been conducted to test how human disturbances are affecting plant-pollinator interactions in this unique ecosystem. Hence, we aimed to provide the first insight into the impact of habitat loss and human disturbances on the pollinator communities in the Sundarbans. We selected 12 sites in the North-Western region of the Sundarbans, along a gradient of decreasing habitat loss and human activities from forest fragments near human settlements to continuous pristine forest, where we studied insect pollinators of two mangrove plant species, Acanthus ilicifolius and Avicennia officinalis. Our results show that different pollinator groups responded to the disturbance gradient differently. For example, the abundance of Apis dorsata, one of the three local species of honey bees, increased gradually from the village area towards the deep pristine forest. On the other hand, A. cerana and A. florea were found in the village sites and completely absent in the deep forest. Although pollinator community composition changed along the disturbance gradient, their efficacy in pollination did not seem to be significantly affected. However, lower plant diversity and low understory plant cover in the forest patches nearby the village indicated that human disturbances not only affected pollinator community composition but also played a major negative role in the regeneration of the forest. Our study provides first insights into plant-pollinator interactions in the Sundarbans and demonstrates that more research is needed to imply conservation strategies for this unique habitat.

Mangrove endophytic fungi have recently gained attention among researchers as a replacement of mangrove phytoconstituents to protect critically endangered mangrove species. 2,4,6-triphenylaniline (TPA) is an endophytic secondary metabolite isolated from a novel strain Alternaria longipes strain VITN14G derived from mangrove plant Avicennia officinalis to perceive its role in antidiabetic activity. Antidiabetic efficacy of TPA and TPA loaded nanoemulsion formulation (NE) were validated using low dosage (35 mg/kg bw) of streptozotocin (STZ) induced high-fat diet Albino Wistar rats. The diabetic rats were orally administered with TPA (10 mg/kg bw), nano emulsified TPA (10 mg/kg bw) and the standard drug metformin (10 mg/kg bw) respectively once on a daily basis for a period of 48 days. After intervention period, TPA and TPA loaded NE showed controlled blood glucose, significant effect on electrolytes, liver and kidney function test as comparable to standard drug metformin. TPA loaded NE was found to have lesser toxicity on liver, kidney, pancreas and heart than TPA. Moreover, gene expression studies of TPA and TPA loaded NE showed down regulation of PKA and up regulation of AMPK which was similar to the effect of metformin. Therefore, the antidiabetic effect of TPA and TPA loaded NE can be correlated with PKA regulation and vice versa with AMPK regulation. The outcome of this study paves a way to use a natural substitute for existing synthetic antidiabetic drugs.

The forest structure and its relation to environmental parameters of Sundarbans, largest mangrove habitat in India, are presented. Quadrat method was used to analyze the vegetation-environment interaction and structural maturity of mangroves. Floristic studies revealed twenty-seven mangrove species including the critically endangered Sonneratia griffithii and endangered Heritiera fomes. Based on Importance Value Index, Avicennia marina, Excoecaria agallocha, Avicennia officinalis and Avicennia alba were designated as the most important species. Higher diversity indices were observed (Shannon index, ranged from 4.2-1.8; Pielou’s index, 0.96-0.91) revealing greater species diversity and even dispersion of mangroves in Sundarbans. Stem density varied from 133 to 19333 ha−1 and individual basal area 0.4 to 13.4m2ha−1. A very low Maturity Index Value was recorded indicating a low degree of structural maturity. Most of the vegetation parameters (density, species diversity index, β diversity) and few of the edaphic parameters (pH, grain size, total carbon) were found to be in better condition; however, salinity showed significant negative correlations with vegetation characteristics. The study revealed a mixed species composition with intermediate structural development indicating a growing forest in Sundarbans. The data evolved in the study would be fundamental in site-specific management and conservation efforts of mangroves in this world heritage site.

The Ganges Delta and Sundarbans comprise the largest continuous mangrove area in the world. These mangroves are subjected to high riverine and tidal dynamics, and the coastline irregularity is characterized by many north-to-south oriented rivers that may hamper dispersal of mangrove propagules. Whereas connectivity levels and resulting population genetic structure often can be explained by ocean currents, other factors may control estuarine-scale mangrove genetic patterns and limit gene flow even between sites in close geographic proximity. We investigated whether the complex estuarine coastline in the Ganges Delta and Sundarbans shaped the genetic structure of Avicennia officinalis populations across regions and rivers at various distances (ca. 1 to 265 km). Using nine microsatellite loci, 433 individuals from 14 populations revealed predominant outcrossing and a high level of genetic variation when compared to other Avicennia species. A moderate but significant level of differentiation was detected among populations (F ST = 0.09), and a principal coordinate analysis clearly separated populations of the Chittagong coastline from the Sundarbans. An individual-based Bayesian analysis also indicated those two gene pools. Genetic distances across the whole region could best be explained by cumulative river width and geographical distance separating the populations. Within the Sundarban region, the low genetic differentiation of A. officinalis populations indicated a continuous distribution model with a smooth isolation-by-distance that gradually increased across large rivers shaping the genetic structure of A. officinalis in the Ganges Delta. These findings indicated that in addition to geographical distance, rivers might act as physical barriers, affect gene flow and shape genetic connectivity. This and detailed population genetic information should be incorporated into the ongoing afforestation or restoration strategies in and outside of the Sundarbans mangrove forest.

This study at Indian Sundarbans, identifies metal tolerant mangroves with phytoremediation potential by understanding the affect of metal pollution on the community structure of this estuarine ecosystem. Community study indicates that polluted site has lower relative density of the true mangrove and four metal tolerant species (Cryptocoryne ciliata, Heliotropium currasavicum, Hemarthria altissima and Avicennia officinalis) are predominant with 72 % of relative density. Biodiversity indices (Simpson’s index of Dominance and Diversity, Shannon-Weiner index) indicate reduction in diversity and increase in dominance of metal tolerance species at the polluted site. The cluster/components originating after cluster and principal component analysis shows that Cr, Pb, Cd and Ni are metal pollutants of anthropogenic origin. Metal accumulation study is conducted on these four species after assessing the status of metal pollution in their rhizospheres using Ecological risk index, Geoaccumulation index, Enrichment factor and Contamination factor. Bioaccumulation factor emphasized that C. ciliata has a high potential for extracting Cd, Cr and Pb. Bioconcentration factor of Cr is high for A. officinalis, C. ciliata (potentially invasive) and H. altissima (invasive species) whereas translocation factor indicates Cd, Ni and Zn can be translocated to the aerial part of these plants. In addition, H. altissima also transfer Cr and Pb to their aerial parts. This study concluded that C. ciliata could be used as phytoextracter for Cd, Cr and Pb in metal contaminated mangrove ecosystem.

A study was carried out to assess the species diversity of arbuscular mycorrhizal AM fungi in different salinity zones of Bhitarkanika mangroves of Orissa India Sixteen sites of Bhitarkanika mangrove areas were surveyed for the collection of roots and soil samples Seedlings of mangrove species were tested for AM colonization through root clearing and staining technique Soil samples were treated separately for the mineral analysis through wet oxidation techniques and spore multiplication by pot culture methods Wet sieving and decantation technique was followed for the isolation of AM spores from soil AM spores were identified on the basis of morphological characteristics by following the INVAM manual The physio chemical analysis of soil indicated its deficiency in phosphorus which decreases Kg ha with increase in salinity The genus Glomus is most dominant and has presence across all saline zones A total of AM species belonging to five genera namely Glomus Acaulospora Gigaspora Scutellospora and Enterophospora were recorded from three salinity zones of Bhitarkanika mangrove ecosystem The soils of lower salinity contained maximum number of AM species nos than the high salinity zones nos The decreased number of AM species in high salinity may be due to low phosphorus content and lack of suitable host plant also Among eighteen mangrove species from different salinity zones analyzed for mycorrhizal colonization in their root system Sonneratia apetala Heritiera fomes Excoecaria agallocha Derris heterophylla Bruguiera gynmorrhiza Avicennia officinalis Aglaia cucullata and Aegiceras corniculatum were found to be mycorrhizal This is first report on diversity of AM species in different salinity zones of Bhitarkanika mangroves of Orissa India

International audience; A new species of Eutrachytes (Eutrachytes flagellatus) is described based on a complete ontogenetic series, starting from larva and including the adult female and male. This Uropodina mite was isolated from the pneumatophore surface of Avicennia officinalis having algal (Bostryschia sp.) growth in Goa, India. Notable morphological attributes peculiar to immature instars of this species include a flagellate tubular dorsolateral respiratory structure extending from the peritreme, nude pygidial shields in the adult male and female and a deep concave formation at the posterolateral margins of the dorsal shield. A taxonomic discussion with salient diagnostic features of the genus is given and a key to genera of the family is presented. We present two nomenclature modifications: Deraiophoridae syn. nov. as the junior synonym of Eutrachytidae and Dentibaiulus Hirschmann, 1979 syn. nov. as a junior synonym of Eutrachytes Berlese, 1914. A compiled list of all new species discovered to date from mangrove roots in different parts of the world is given.

Nutrient cycling in mangrove forests is strongly linked to detrital processing of leaf litter, as compared to direct herbivorous consumption. Sesarmid crabs play a key role in detrital pathways in mangrove forests by processing a large amount of leaf litter produced in the ecosystem. We studied the rate of leaf litter translocation and consumption by a sesarmid crab, Neosarmatium malabaricum , through an ex situ experiment simulating field conditions. We supplied weighed senescent leaves of Aegiceras corniculatum, Avicennia officinalis , Excoecaria agallocha and Rhizophora mucronata to the crab. When provided separately, the crab translocated leaf litter of E. agallocha the maximum, and that of Rhizophora mucronata the minimum to the burrows. When litter mixed together was provided, the rate of translocation was the highest. The crabs consumed up to 80.24% of the litter that they translocated. We found this species capable of translocating 4.39 ±1.68 g of leaf litter m -2 per day and that its population had the potential to translocate 1.81 times more leaf litter than the ecosystem produced, based on comparisons of translocation rate, density of N. malabaricum and leaf litter production in the study area. Our experiments emphasize the key role played by this crab in detrital pathways of mangrove ecosystem.