Monsoonal Influence on Evapotranspiration of the Tropical Mangrove Forest in Northeast India
Dipnarayan Ganguly, Raghab Ray, Natasha Majumder, Chumki Chowdhury,
Tapan Kumar Jana
American Journal of Climate Change, 2014, 3, 232-244

Abstract

Evapotranspiration (ET) is an important part of the water cycle. This study reports on the monsoonal influence on the temporal variation in evapotranspiration of an extremely water conservative and salinity stressed tropical mangrove forest at the land-ocean boundary of northeast coast of India. The magnitude and dynamics of evapotranspiration (ET) exhibited seasonality dominated by monsoon and evaporation rate was greater (0.055 ± 0.015 g∙m−2∙s−1) during the monsoon than in pre-monsoon (0.049 ± 0.018 g∙m−2∙s−1) and post-monsoon (0.044±0.012gm−2∙s−1). Seasonal difference in evapotranpiration was mostly due to fluctuation of canopy resistance, which was the minimum during monsoon when relative humidity was greater than in the dry season (pre- and post-monsoon) and deficiency of water supply (ET ≈ ETeq) was minimum. Evapotranspiration in the Sundarban mangrove ecosystem is the predominant biophysical processes that recycles 67.7% of total precipitation annually to the atmosphere, and has significant monsoonal influence.

Keywords

Canopy Resistance, Evapotranspiration, Hydrological Cycle, India, Mangrove Forest, Monsoonal Cycle

Biogeochemical cycle of nitrogen in a tropical mangrove ecosystem,
east coast of India
Raghab Ray, Natasha Majumder, Subhajit Das, Chumki Chowdhury, Tapan Kumar Jana
Marine Chemistry, Elsevier, doi.org/10.1016/j.marchem.2014.04.007

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 × 106 mol yr−1) was about six fold as large as that of NOx, (22 × 106 mol yr−1). The nitrogen stored by the processes such as plant uptake of NOx, NH3 from the atmosphere, nitrogen fixation (5 × 109 mol yr−1), and sediment water exchange (8 × 106 mol yr−1) was about two times as large as that of recycled nitrogen from litter (3 × 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 × 103 mol ha−1 versus soil: 3 × 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 × 106 mol) of the annual river flux of nitrogen to the coastal waters and nitrogen is generally conserved within the system.

Keywords: Box model,Nitrogen, Biomass, Mangrove, Sundarban.

Quantitative Study of As (V) and As (III) Interaction with Mangrove DNA by Molecular Fluorescence Spectroscopy
N. Majumder • C. Chowdhury • R. Ray •T. K. Jana
Bull Environ Contam Toxicol
DOI 10.1007/s00128-014-1265-y

This study describes the in vitro study of (1:1) one step nucleophilic displacement (S1 N) of phosphate by heavier anion arsenate and arsenite in the DNA of arsenicridden 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.