12^th International Estuarine Biogeochemistry Symposium (IEBS 2013)

Plymouth University, 30^th June - 4^th July 2013

Keynote Speaker:

• Prof. Tapan Kumar Jana, University of Kolkata, India

Title of talk: Biosphere-Atmosphere coupling – a tropical mangrove system perspective


Venue: Plymouth University, Rolle Building , Plymouth PL4 8AA 

 

Dynamics and exchange fluxes of methane in the estuarine mangrove environment of the Sundarbans, NE coast of India

M.K. Dutta, C. Chowdhury, T.K. Jana, S.K. Mukhopadhyay
Atmospheric Environment 77 (2013) 631-639

Abstract

The distribution and exchange fluxes of methane (CH₄) were measured in a mangrove vegetated island and its bordering estuarine system of the Sundarbans mangrove biosphere from June 2010 to December 2011 on monthly basis. The onset of methane production is evident in the forest sediment at about 25 cm deep sediment layer under strong redox condition having an average Eh value of 175.7 mV and showing a 2.8 folds increase in the pore water dissolved methane concentration at that depth in comparison to the surface layer. The average diffusive flux of methane from this methane producing layer to surface was calculated to be 591±106 nmol m ^-2 d ^-1. The depth profiles of NO₂^- -N, SO₄^-2-S, acid volatile sulphide, organic carbon and dissolved methane in the sediment cores from inter-tidal zones showed distinct trends representing signatures of denitrification, sulfate reduction and methanogenesis in the sediment layers. The methane emission from the sedimenteatmosphere interface was observed to be maximum during monsoon and higher emission rates was recorded from upper littoral zone. The annual average atmospheric methane mixing ratio was 2.038±0.07 ppmv. This mangrove biosphere was found to act as source for methane during monsoon while as sink during pre and postmonsoon seasons. Estuarine surface water showed a very high degree of super saturation about 2748±730% for dissolved methane at an annual basis and act as a significant source of methane having an annual average exchange flux of 408±110 nmol m^-2 h^-1. A box model approach has been adopted at annual basis to understand the distribution and dynamics of methane in this mangrove environment

Improved model calculation of atmospheric CO₂ increment in affecting carbon stock of tropical mangrove forest

By RAGHAB RAY, CHUMKI CHOWDHURY, NATASHA MAJUMDER,

MANAB KUMAR DUTTA, SANDIP KUMAR MUKHOPADHYAY and

TAPAN KUMAR JANA*, 

*Department of Marine Science, University of Calcutta,

35, B. C. Road, Kolkata-700019, India

(Manuscript received 15 June 2012; in final form 18 March 2013)

Citation: Tellus B, 65, 18981, http://dx.doi.org/10.3402/tellusb.v65i0.18981

ABSTRACT

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 northeast coast of the Bay of Bengal. The above and below ground biomass (AGB+BGB) and sediment held different carbon stock (53.20±2.87 Mg C ha^-1 (mega gram carbon per hectare) versus 18.52±2.77 Mg C ha^-1). Carbon uptake (0.348 mg C m^-2s^-1) is more than offset by losses from plant emission (0.257 mg C m^-2s^-1) and litter fall (13.52 μg C m^-2s^-1) was more than soil CO₂ and CH₄ emission (8.36 and 1.39 μg 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 5.94 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 disturbance.

Keywords: carbon stock, CO₂ sensitivity, box model, mangrove forest, India

Implication of Organic Matter on Arsenic and Antimony Sequestration in Sediment: Evidence from Sundarban Mangrove Forest, India.

S. K. Mandal, R. Ray, C. Chowdhury, N. Majumder, T. K. Jana

Bull Environ Contam Toxicol, 2013, DOI 10.1007/s00128-012-0934-y

Abstract

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.

Key words: Arsenic, Antimony, Humic substances, stability constant