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.
Like many coastal systems, nitrogen is the critical limiting factor for mangrove net production. This studyused a box model approach to assess the nitrogen budget in the Sundarban mangrove ecosystem, whichacts 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 uptakeof 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, nitrogenfixation (5 × 109 mol yr−1), and sediment water exchange (8 × 106 mol yr−1) was about two times aslarge as that of recycled nitrogen from litter (3 × 109 mol yr−1), and could account 74% of the nitrogen requiredfor 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 amountthat was conserved from the external sources in the Sundarban mangrove system. Thus, the coastal ecosystemlike Sundarban mangroves could retain only 0.2% (8 × 106 mol) of the annual river flux of nitrogen tothe coastal waters and nitrogen is generally conserved within the system.
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