Natasha Majumder

Improved model calculation of atmospheric CO 2 increment in affecting carbon stock of tropical mangrove forest

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

Implication of organic matter on arsenic and antimony sequestration in sediment: evidence from Sundarban mangrove forest, India.

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

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

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

Wood chemistry and density: An analog for response to the change of carbon sequestration in mangroves

This study aimed to resolve the variations of physical and chemical properties of wood records measured in different mangroves with their annual carbon sequestration. The methods of investigation used were to examine growth rate by monitoring breast height diameter, wood chemistry and density, FTIR spectroscopy and thermogravimetry. Carbon sequestration rate showing an increase with density varied between 0.088 and 0.171 μg C kg(-1) AGB s(-1), and Avicennia marina showed the maximum value and Bruguiera gymnorrhiza, the minimum. The changes in FTIR bands at 4000-2500 cm(-1) and 1700-800 cm(-1) were correlated to the variations in cellulose in mangrove woods and lignin to cellulose ratio ranged between 0.21 and 1.75. Thermal analyses of mangrove wood suggested that the fuel value index (985-3922) exhibited an increase with the decrease in maximum decomposition temperature and density. The seasonal variation of temperature and CO2 were likely to affect chemical properties through changes in wood density.

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

This study describes the in vitro study of (1:1) one step nucleophilic displacement (

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

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Adsorption kinetic control of As(III & V) mobilization and sequestration by Mangrove sediment

SN1) of phosphate by heavier anion arsenate and arsenite in the DNA of arsenic ridden Sundarban mangroves. Mangrove DNA was found to give rise to a broad fluorescence and its integrated fluorescence intensity was enhanced on addition of As (V) and As (III), respectively. Analyses of the fluorescence parameter showed adequacy of 1:1 model to describe substitution of phosphate of mangrove DNA chain exiplex by arsenate and arsenite with equilibrium constant (log Kc) ranging between 4.19 and 4.32 for As (V), and between 3.77 and 3.89 for As (III) at pH 7 and 25°C. In the cases, the melting temperature (Tm) and reassociation rate constant of mangrove DNA was increased on treatment with As (V) and As (III). It is suggested that heavier ion arsenate and arsenite may substitute phosphate in natural DNA.

Inter-annual abundance variation in some genera of diatom and zooplankton in a mangrove ecosystem

ABSTRACT The extent of toxic metalloid retention and bioavailability and mobility in the sediment is of interest for understanding their biogeochemical cycling and for accurate risk assessment in an ecosystem. Intensification of monsoon and rainfall, believed to be related to global warming, could drive future changes of temperature, salinity, and pH distribution pattern affecting antimony cycling in the Sundarbans. This study investigated sorption kinetics of antimony (Sb) (III and V) as a function of temperature, salinity, and pH following the Langmuir model, and demonstrated that clayey silt type mangrove sediment was an effective adsorbent with higher efficiency for Sb (V) than Sb (III). Background level of Sb in the sediment was 0.35–0.78% of the maximum adsorption capacity (Γm). Out of the two distinct type of sorption sites governing mobility and bioavailability of Sb in the sediment, site 1 (Humic acid) showed higher affinity for Sb than the site II (oxyhydroxide). Sb adsorption was strongly influenced by temperature, salinity, and pH, which may be altered by long-term changes in climate and rainfall pattern.