The Sundarban mangrove forest (4264 km2) is about 3% of the total area of the world mangrove is interdependent on the coastal aquatic subecosystem (1781 km2). Ammonia concentration and flux measurements in the mangrove ecosystem and measurements in such tropical land-ocean boundary conditions are few and far between. A micrometeorological method was used to measure ammonia exchange over Sundarban mangrove forest and aquatic subecosystem. Results showed both emission and gaseous dry deposition in the forest area at a rate 1.79×103 and 2.26×103 kg N km-2 yr-1, respectively. Flux of ammonia in the aquatic subecosystem was found always from air to water with a rate of 775.7 kg N km-2 yr-1. The annual particulate dry and wet atmospherically deposited ammonia flux were calculated to be 69.0 and 21.5 kg N km-2 yr-1, respectively. Exchange of gaseous ammonia in the mangrove forest showed net deposition with a rate of 4.90×10 2 kg N km-2 yr-1. Annual imported flux from the proximate terrestrial source to this virgin forest was found to be 4.26×106 kg N yr-1 out of which 32.9% was deposited to the coastal water. Ammonia compensation point for mangrove vegetation was found to occur between 51 and 421 nmol m-3 and its variation was related to wind velocity, temperature, and humidity. © 2005 Elsevier Ltd. All rights reserved.

TARUN DE

Marine Science

H BISWAS

A CHATTERJEE

S K MUKHOPADHYA

S SEN

T K JANA

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Atmospheric Environment

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 (130×106molyr-1) was about six fold as large as that of NOx, (22×106molyr-1). The nitrogen stored by the processes such as plant uptake of NOx, NH3 from the atmosphere, nitrogen fixation (5×109molyr-1), and sediment water exchange (8×106molyr-1) was about two times as large as that of recycled nitrogen from litter (3×109molyr-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: 118×103molha-1 versus soil: 3×103molha-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% (8×106mol) of the annual river flux of nitrogen to the coastal waters and nitrogen is generally conserved within the system. © 2014 Elsevier B.V.

Marine Chemistry

Biogeochemical cycle of nitrogen in a tropical mangrove ecosystem, east coast of India

Amount of radiant energy (short wave) available to drive biosphere-atmosphere exchange of CO2, H2O, CH4 and for transfer into other energy forms were determined for a tropical mangrove forest at the land ocean boundary of north-east (NE) coast of Bay of Bengal from January to December 2006. The mean annual incoming short wave radiation (435±32.8 W m-2) was partitioned into 29% sensible heat, 35% latent heat, 4% ground heat, 7% physical storage energy and 10% photosynthetic storage energy. The mean budget closing energy flux (68.96±24.6 W m-2) or, budget error was 15.8% of incoming short wave radiation. In Varimax factor analysis, budget closing energy flux showed high loading in association with leaf chlorophyll of different mangrove species, indicating its major role for reflectivity of the surface for short wave. There was significant seasonality in CO2 exchange with net primary productivity of 14.1 μmol m-2 s-1. The mean methane emission was found higher (7.29 μg m-2 s-1) during the daytime than that of night time (1.37 μg m-2 s-1) with maximum methane emission rates of 36.1 and 21.1 μg m-2 s-1 in December and January, respectively. Stepwise multiple regression analysis between storage energy [ΔHs(P)] and fluxes of CO2, CH4, H (sensible heat), HL (latent heat of evaporation), ΔR (budget closer energy) showed that the combined explained variability for CO2 flux, evapotranspiration and budget closer energy (39%) was less than that of CH4 and sensible heat flux (46%). The extent of warming effect by CH4 and sensible heat flux was predominant over the resultant cooling effect due to the processes such as photosynthesis, evapotranspiration and albedo. The mangrove forest with two trademarks of low albedo and high surface roughness was poorly coupled to the environment. © 2008 Elsevier Ltd. All rights reserved.

Energy dynamics and its implication to biosphere-atmosphere exchange of CO2, H2O and CH4 in a tropical mangrove forest canopy

A comprehensive size-segregated characterization of the chemical properties (water-soluble inorganic fraction) of the sea-salt aerosol originated from the surf zone at the land-ocean boundary of Sundarban Mangrove forest, NE coast of Bay of Bengal, and an analysis of the relevant meteorological parameters revealed how the combined effect of anthropogenic gases and aerosol advected to the virgin mangrove forest and micrometeorological conditions could change the marine character of the aerosol before the onset of SW monsoon. The average aerosol mass concentration was 99.94 ± 41.9 μg m-3 with production rate of 0.19 μg m-2 s-1 (durinq January) to 4.29 μg m-2 s-1 (during April) and dry deposition rate of 0.019 μg m-2 s-1 (during January) to 13.21 μg m-2 s-1 (during June). 72.35% of the total aerosol mass was leachable by water, and relatively large concentrations of phosphorus were observed. More chloride depletion from the coarse (2.0 < d<inf>p</inf> < 10 μm) and nucleation (d<inf>p</inf> < 0.4 μm) modes compared to the accumulation mode (0.4 < d<inf>p</inf> < 2.0 μm) was observed in winter (Cl/Na = 0.6023 ± 0.1798), and a reverse trend was observed in summer (Cl/Na = 0.644 ± 0.262). A significant positive correlation was obtained for chloride loss with non-sea-sulphate and nitrate for particles > 2.0 μm. Distributions of Na+, K+, Ca2+, Mg2+, NH<inf>4</inf>+, Cl-, NO<inf>2</inf>-, NO<inf>3</inf>-, SO<inf>4</inf>2-, and PO<inf>4</inf>3- in different size modes were considered to collate their source apportionment. The proximity of Calcutta and Haldia metropolis to the mangrove forest could influence the forest air quality and depositional processes. Copyright 2006 by the American Geophysical Union.

Fulltext

Journal of Geophysical Research: Atmospheres

Formation, transformation, and removal of aerosol over a tropical mangrove forest

The Sundarban mangrove forest (4,264 km2) constitutes about 3% of the total area of the world mangrove. We measured diurnal and seasonal variations of air-water CO2 exchange in relation to the occurrence of phytoplankton during January-December 2001. Diurnal variations of airflows showed that the minimum and maximum CO2 flux of -16.2 μmol m -2 h-1 and 49.9 μmol m-2 h-1, respectively, occurred during the higher sea breeze. The average ratio of dissolved inorganic nitrogen (DIN = 13.85 ± 7.19 μmol L-1) to dissolved inorganic phosphorus (DIP = 1.23 ± 0.57 μmol L -1) was 11 ± 4 and the surface water was undersaturated with respect to dissolved oxygen. The mean value of 0.1 ± 0.08 for the ratio of phytoplankton production (P) to community respiration (R) indicated that the ecosystem was heterotrophic. The saturation of dissolved carbon dioxide with respect to the atmosphere varied seasonally between 59% and 156%, with minimum levels in postmonsoon and maximum levels in premonsoon/early monsoon (June/July). Out of the 36 genera of diatoms, 1 blue green alga, and 3 dinoflagellates that occurred throughout the year, only 6 reached bloom proportions in postmonsoon, when mangrove water was a sink of atmospheric CO2. Although 59.3% of the emitted CO2 was removed from the atmosphere by biological processes, on an annual basis, the Sundarban mangrove forest supplies 13.8 kg C ha-1 yr-1 of CO 2 from water surface to the atmosphere. Even though it is important to compare all in and out fluxes, there is no direct link between CO 2 emission and the later CO2 removal by biological processes.

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ISSN	1352-2310
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