Papers by Chumki Chowdhury
Environmental Earth Sciences, Jul 22, 2011
Elevated concentrations of arsenic in the sediment and pore water in the Sundarban wetlands pose ... more Elevated concentrations of arsenic in the sediment and pore water in the Sundarban wetlands pose an environmental risk. Adsorption and desorption are hypothesized to be the major processes controlling arsenic retention in surface sediment under oxic/suboxic condition. This study aims to investigate sorption kinetics of As(III & V) and its feedback to arsenic mobilization in the mangrove sediment. It ranges from sand to silty clay loam and shows the adsorption of As(III & V) following the Langmuir relation. Estimates of the maximum adsorption capacity are 59.11 ± 13.26 lg g-1 for As(III) and 58.45 ± 8.75 lg g-1 at 30°C for As(V) in the pH range 4 to 8 and salinity 15-30 psu. Extent of adsorption decreases with increasing pH from 4 to 8 and desorption is the rate-limiting step in the reaction of arsenic with sediment. Arsenic in the sediment could be from a Himalayan supply and codeposited organic matter drives its release from the sediment. Arsenic concentration in the sediment is well below its maximum absorption capacity, suggesting the release of sorbed arsenic in pore water by the microbial oxidation of organic matter in the sediment with less feedback of adsorption.
Tellus B, 2013
Because of the difficulties in setting up arrangements in the intertidal zone for free-air carbon... more 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 landÁocean boundary of the northeast coast of the Bay of Bengal. The above-and below-ground biomass (AGB'BGB) and sediment held different carbon stock (53.2092.87 Mg C ha (1 (mega gram carbon per hectare) versus 18.5292.77 Mg C ha (1). Carbon uptake (0.348 mg C m (2 s (1) is more than offset by losses from plant emission (0.257 mg C m (2 s (1), and litter fall (13.52 mg C m (2 s (1) was more than soil CO 2 and CH 4 emission (8.36 and 1.39 mg C m (2 s (1 , respectively). Across inventory plots, Sundarban mangrove forest carbon storage in above-and below-ground live trees and soil increased by 18.89 and 5.94 Mg 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.
Sustainable Crop Cultivation: A Comprehensive Update
Apple Academic Press eBooks, May 23, 2023
Transparent exopolymer particle production by diatoms and its relation with CO2 flux in mangrove waters of Sundarban, West Bengal
Journal of the Marine Biological Association of India
A simple method for the simultaneous determination of guanine, xanthine and hypoxanthine by RP-HPLC with UV detection
Department of Marine Science, Calcutta University, 35, Ballygunge Circular Road, Kolkata-700 019,... more Department of Marine Science, Calcutta University, 35, Ballygunge Circular Road, Kolkata-700 019, India E-mail : natasha.majumder@gmail.com Manuscript received online 14 August 2014, accepted 06 February 2015 A simple, rapid and accurate method for the simultaneous determination of guanine, xanthine and hypoxanthine has been developed. The quantitative determination of these bases was accomplished by reverse phase high-performance liquid chromatography (<strong>RP-HPLC</strong>) with <strong>UV</strong> detection based on their different retention time without chemical suppression. Separation in the order of guanine, hypoxanthine and xanthine were obtained on <strong>ODS</strong> hypersil column using mobile phase containing 1% ACN in acetic acid (50 mM), ammonium acetate (85 mM) and 0.5% methanol at 0.5 ml min<sup>–1</sup> flow rate. A portion of the natural <strong>DNA</strong> isolated from Avicennia marina was spiked wi...
Journal of Atmospheric Chemistry, 2018
Temporal variations in atmospheric hydrogen sulphide concentrations and its biosphereatmosphere e... more Temporal variations in atmospheric hydrogen sulphide concentrations and its biosphereatmosphere exchanges were studied in the World's largest mangrove ecosystem, Sundarbans, India. The results were used to understand the possible contribution of H 2 S fluxes in the formation of atmospheric aerosol of different size classes (e.g. accumulation, nucleation and coarse mode). The mixing ratio of hydrogen sulphide (H 2 S) over the Sundarban mangrove atmosphere was found maximum during the post-monsoon season (October to January) with a mean value of 0.59 ± 0.02 ppb and the minimum during pre-monsoon (February to May) with a mean value of 0.26 ± 0.01 ppb. This forest acted as a perennial source of H 2 S and the sediment-air emission flux ranged between 1213 ± 276 μg S m −2 d −1 (December) and 457 ± 114 μg S m −2 d −1 (August) with an annual mean of 768 ± 240 μg S m −2 d −1. The total annual emissions of H 2 S from the Indian Sundarban were estimated to be 1.2 ± 0.6 Tg S. The accumulation mode of aerosols was found to be more enriched with non-sea salt sulfate with an average loading of 5.74 μg m −3 followed by the coarse mode (5.18 μg m −3) and nucleation mode (1.18 μg m −3). However, the relative contribution of Non-sea salt sulfate aerosol to total sulfate aerosol was highest in the nucleation mode (83%) followed by the accumulation (73%) and coarse mode (58%). Significant positive relations between H 2 S flux and different modes of NSS indicated the likely link between H 2 S, a dominant precursor for the non-sea salt sulfate, and non-sea sulfate aerosol particles. An increase in H 2 S emissions from the mangrove could result in an increase in enhanced NSS in aerosol and associated cloud albedo, and a decrease in the amount of incoming solar radiation reaching the Sundarban mangrove forest.
International Journal of Biological Chemistry, 2011
Environmental Earth Sciences, 2011
Elevated concentrations of arsenic in the sediment and pore water in the Sundarban wetlands pose ... more Elevated concentrations of arsenic in the sediment and pore water in the Sundarban wetlands pose an environmental risk. Adsorption and desorption are hypothesized to be the major processes controlling arsenic retention in surface sediment under oxic/suboxic condition. This study aims to investigate sorption kinetics of As(III & V) and its feedback to arsenic mobilization in the mangrove sediment. It ranges from sand to silty clay loam and shows the adsorption of As(III & V) following the Langmuir relation. Estimates of the maximum adsorption capacity are 59.11 ± 13.26 lg g-1 for As(III) and 58.45 ± 8.75 lg g-1 at 30°C for As(V) in the pH range 4 to 8 and salinity 15-30 psu. Extent of adsorption decreases with increasing pH from 4 to 8 and desorption is the rate-limiting step in the reaction of arsenic with sediment. Arsenic in the sediment could be from a Himalayan supply and codeposited organic matter drives its release from the sediment. Arsenic concentration in the sediment is well below its maximum absorption capacity, suggesting the release of sorbed arsenic in pore water by the microbial oxidation of organic matter in the sediment with less feedback of adsorption.
Intra-Annual Variation of Modern Foraminiferal Assemblage in a Tropical Mangrove Ecosystem in India
Wetlands, 2012
This study relates the abundance of foraminifera with the fluctuations in hydrobiological charact... more 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.
Tellus B: Chemical and Physical Meteorology, 2013
Because of the difficulties in setting up arrangements in the intertidal zone for free-air carbon... more 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 landÁocean boundary of the northeast coast of the Bay of Bengal. The above-and below-ground biomass (AGB'BGB) and sediment held different carbon stock (53.2092.87 Mg C ha (1 (mega gram carbon per hectare) versus 18.5292.77 Mg C ha (1). Carbon uptake (0.348 mg C m (2 s (1) is more than offset by losses from plant emission (0.257 mg C m (2 s (1), and litter fall (13.52 mg C m (2 s (1) was more than soil CO 2 and CH 4 emission (8.36 and 1.39 mg C m (2 s (1 , respectively). Across inventory plots, Sundarban mangrove forest carbon storage in above-and below-ground live trees and soil increased by 18.89 and 5.94 Mg 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.
Biogeochemical cycle of nitrogen in a tropical mangrove ecosystem, east coast of India
Marine Chemistry, 2014
ABSTRACT Like many coastal systems, nitrogen is the critical limiting factor for mangrove net pro... more ABSTRACT Like many coastal systems, nitrogen is the critical limiting factor for mangrove net production. This study used a box model approach to assess the nitrogen budget in the Sundarban mangrove ecosystem, which acts as a sink for atmospheric nitrogen in terms of NOx, NH3, N2, and water column dissolved inorganic nitrogen. The coupling of biosphere and atmosphere in terms of atmospheric NOx and NH3 uptake showed that uptake of ammonia, (130 x 106 mol yr- 1 ) was about six fold as large as that of NOx, (22 x 106 mol yr- 1). The nitrogen stored by the processes such as plant uptake of NOx, NH3 from the atmosphere, nitrogen fixation (5 x 109 mol yr- 1), and sediment water exchange (8 x 106 mol yr- 1) was about two times as large as that of recycled nitrogen from litter (3 x 109 mol yr- 1), and could account 74 % of the nitrogen required for mangrove net production. Most of the nitrogen was conserved in the living biomass (living biomass: 118 x 103 mol ha- 1 versus soil: 3 x 103 mol ha- 1). The loss of nitrogen was 23 % of the total amount that was conserved from the external sources in the Sundarban mangrove system. Thus, the coastal ecosystem like Sundarban mangroves could retain only 0.2 % (8 x 106 mole) of the annual river flux of nitrogen to the coastal waters.and nitrogen is generally conserved within the system.
Microbial Ecosystem in Sunderban Mangrove Forest Sediment, North-East Coast of Bay of Bengal, India
Geomicrobiology Journal, 2012
This is the first documentation of seasonal and spatial fluctuation of the culturable microbial p... more This is the first documentation of seasonal and spatial fluctuation of the culturable microbial population collected from different zones in the sediment of the Sunderban mangrove forest. The population of cellulose degrading bacteria, [mean value of CFU 6.189 ± 1.025 × 10 (g dry weight of sediment)] was found to be maximum during post monsoon in the deep forest region, whereas, the fungal population [mean value of CFU 3.424 ± 0.886 × 10 (g dry weight of sediment)] was found to be maximum during pre-monsoon in the rooted region. The abundances of microbes, in decreasing order, studied from different zones are nitrifying bacteria [mean value of CFU 1.125 ± 0.359 × 10 (g dry weight of sediment)], phosphorous solubilizing bacteria (PSB) [mean value of CFU 0.805 ± 0.322 × 10 (g dry weight of sediment)], free living nitrogen fixing bacteria [mean value of CFU 0.417 ± 0.120 × 10 (g dry weight of sediment)] and sulfur reducing bacteria (SRB) [mean value of CFU 0.356 ± 0.125 × 10 (g dry weight of sediment)]. The content of organic carbon in the soil decreased from the deep forest region to the rooted and unrooted region but a reverse profile was found for soil salinity and soil silicate concentration. The results from the present study indicate that the monsoon cycle has a pronounced effect on the microbially dominated biogeochemistry in the sediment and consequently on the ecology of the Sundarban mangrove forest.
Carbohydrate Polymers, 2012
This study aimed to resolve the variations of physical and chemical properties of wood records me... more 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 g 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 CO 2 were likely to affect chemical properties through changes in wood density.
Atmospheric Environment, 2011
Here we show carbon stock is lower in the tropical mangrove forest than in the terrestrial tropic... more Here we show carbon stock is lower in the tropical mangrove forest than in the terrestrial tropical forest and their annual increase exhibits faster turn over than the tropical forest. Variable for above ground biomass are in decreasing order of importance, breast height diameter (d), height (H) and wood density (r). The above ground biomass (AGB) and live below ground biomass (LBGB) held different biomass (39.93 AE 14.05 t C ha À1 versus 9.61 AE 3.37 t C ha À1). Carbon accrual to live biomass (4.71e6.54 Mg C ha À1 a À1) is more than offset by losses from litter fall (4.85 Mg C ha À1 a À1), and carbon sequestration differs significantly between live biomass (1.69 Mg C ha À1 a À1) and sediment (0.012 Mg C ha À1 a À1). Growth specific analyses of taxon density suggest that changes in resource availability and environmental constrains could be the cause of the annual increase in carbon stocks in the Sundarbans mangrove forest in contrast to the disturbance e recovery hypotheses.
Atmospheric Environment, 2011
This study reveals that landesea breezes, atmospheric stability and influence of net ecosystem me... more This study reveals that landesea breezes, atmospheric stability and influence of net ecosystem metabolism for the conversion of organic carbon to atmospheric CO 2 are the major driving forces behind the variation of atmospheric CO 2 at the landeocean boundary, northeast coast of India. The seasonal variation of partial pressure of CO 2 (pCO 2) and its efflux from the coastal water were several fold higher in the pre-monsoon (1807.9 AE 757.03 m atm; 579.03 AE 172.9 mM m À2 h À1) than in the monsoon (1070.5 AE 328.5 m atm; 258.96 AE 185.65 mM m À2 h À1) and the post-monsoon (615.7 AE 121.6 m atm; 53.27 AE 19.24 mM m À2 h À1). The mean photic zone productivity to column respiration ratio was 0.12 AE 0.08, revealing predominance of heterotrophic processes. Community respiration was at minimum during monsoon (38.82 AE 8.63 mM C m À2 d À1) but was at maximum (173.8 AE 111.8 mM C m À2 d À1) during pre-monsoon and intermittent (125.07 AE 11.97 mM C m À2 d À1) during post-monsoon. Diurnal variations of atmospheric CO 2 concentration were determined by local air circulations and atmospheric stability. Seasonal variations of atmospheric CO 2 bear a significant signature of biological processes occurring in the coastal water by means of airesea exchange, markedly affected by the net ecosystem metabolism. Important predictors of coastal atmospheric CO 2 in decreasing order of explained variability are wind direction, stability, CO 2 efflux and wind velocity.
Estuaries and Coasts, 2017
Phosphorus (P) cycling in mangroves plays an important role in productivity but the magnitude of ... more Phosphorus (P) cycling in mangroves plays an important role in productivity but the magnitude of atmospheric input in the mangrove P budget is still uncertain. This study applied a box model approach to assess P budget in the Indian Sundarban, the world's largest mangrove ecosystem for conceptual understanding of P cycling and for better representation of transport and transformation of P within the mangrove ecosystem. The P content in the sediment (0.19-0.67 μg g −1) was found much below its maximum retention capacity (322 μg g −1) and was lower than the mean marine sediment (669 μg g −1). The C:N and C:P ratios were correlated (r 2 = 0.66, P < 0.01) and the major fraction of available P was recycled within the organic structure of mangrove ecosystem, thus maintaining productivity through conservation strategies. Atmospheric input accounted for 56.7% of total P input (16.06 Gg year −1) and 50% of total P output (14.7 Gg year −1) was attributed to plant uptake. Budget closing or unaccounted P (1.36 Gg) was only 8.5% of the total input. Two feedback pathways, i.e., input of P from dust fallout and biochemical mineralization of organic matter, significantly affected P availability. The findings of the study suggest that atmospheric deposition is of major importance as a natural and/or anthropogenic forcing function in the Sundarban mangrove system.
Comparison of Monsoonal change of water quality parameters between 1983 and 2008 in a tropical estuary in Northeastern India: role of phytoplankton and community metabolism
Marine Ecology
Ongoing climate change and anthropogenic activities are introducing stressors that affect the str... more Ongoing climate change and anthropogenic activities are introducing stressors that affect the structure and function of coastal ecosystems. This paper focuses on the fluvial fluxes and estuarine transport of nutrients from a tropical river (Mahanadi River) in Northeastern India and compares select nutrient and water quality parameters between 1983 and 2008. This estuary acts as a perennial source of CO2 with a net annual flux to the atmosphere of about 135 tons. The non‐conservative fluxes showed a net annual removal of 650 and 140 tons of phosphorus and nitrogen from the water column, respectively. Negative biogeochemical feedbacks that decreased the availability of N and P in 2008 relative to 1983 levels indicate major changes in biogeochemical responses towards fluvial fluxes of nutrient.
Effect of pH and Salinity on Sorption of Antimony (III and V) on Mangrove Sediment, Sundarban, India
Soil and Sediment Contamination: An International Journal
Arsenic distribution in waters and its geochemical behavior in sediment of Mahanadi estuary in India
Environmental Monitoring and Assessment, 2016
Distribution of arsenic in the marine environment is associated with its biogeochemical behavior.... more Distribution of arsenic in the marine environment is associated with its biogeochemical behavior. Indeed, very few studies have been conducted along the seasonal cycle to show its non-conservative behavior in the tropical estuary. The Mahanadi River, one of the major tropical rivers in the peninsular India, drains densely populated and industrialized region of Paradeep port. Over this 1-year study, the variations of inorganic arsenic were examined along the salinity gradient of the Mahanadi estuary, with the aim to provide some insights into the mechanisms that control arsenic concentrations and behavior under estuarine mixing. Arsenic in the estuary was derived from both natural and anthropogenic sources, and it displayed partial removal from the water in the mixing zone. Results of geo-accumulation index indicated that sediments were uncontaminated and they acted as a sink for arsenic. The diffusive fluxes from water to sediment were estimated to be 9.05 μg m(-2) day(-1) at Chaumohona, 9.83 μg m(-2) day(-1) at Kaudia, and 11.85 μg m(-2) day(-1) at Neherubunglow. The findings of the study suggest that both the removal of arsenic by biogeochemical processes and its diffusive transport from water to sediment are of major importance for both the non-conservative behavior of arsenic in the estuary and its export to the coastal water.
Seasonal distribution and correlates of transparent exopolymer particles (TEP) in the waters surrounding mangroves in the Sundarbans
Journal of Sea Research, 2016
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Papers by Chumki Chowdhury