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.
•Nitrogen was at all times recycled in the mangrove biomass.•Sundarban could retain 0.2% of the river flux of nitrogen to the coastal waters.•Sundarbans acted as a sink for atmospheric N2, NOx, NH3 and DIN.•The loss of nitrogen was 19% of the gain from the external sources.•Nitrogen is generally conserved within the system.
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 the northeast coast of the Bay of Bengal. The above- and below-ground biomass (AGB+BGB) and sediment held different carbon stock (53.20±2.87Mg C ha
−1
(mega gram carbon per hectare) versus 18.52±2.77Mg C ha
−1
). Carbon uptake (0.348mg C m
−2
s
−1
) is more than offset by losses from plant emission (0.257mg C m
−2
s
−1
), and litter fall (13.52µg C m
−2
s
−1
) was more than soil CO
2
and CH
4
emission (8.36 and 1.39µg 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 5.94Mg 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.
Nitrification is a vital biogeochemical process during which ammonium (NH
4
+
) is oxidized to nitrite (NO
2
−
) and nitrate (NO
3
−
) using oxygen. Nitrification is particularly important in ...estuaries, where nitrification rates have significant implications for ecosystem functioning. Our study investigated seasonal and spatial variations of nitrification rates in both water and sediment phases of mangrove ecosystems in the Indian Sundarbans, integrating the three major estuaries (Saptamukhi, Thakuran, and Matla). We used on board incubation to measure nitrifying activity i.e., ammonium oxidation rate (Ra) and nitrite oxidation rate (Rn) in the water column. We found that average Ra and Rn rates were similar, ranging from 31.1 to 31.8 nmol N L
−1
h
−1
, respectively. Water column nitrification rates showed an inverse relationship with salinity (
r
= − 0.51,
p
< 0.001), while substrate concentrations of ammonium had a direct impact on nitrification rates. Annual dissolved inorganic nitrogen (DIN) concentrations were 11.7 ± 7.65 µM, with an average nitrate (NO
3
−
) concentration of 4.5–16.3 µM and average ammonium (NH
4
+
) concentrations from 2.1 to 5 µM. Suspended particulate matter and chlorophyll showed positive (
r
= 0.38,
p
= 0.009) and negative (
r
= − 0.31,
p
= 0.034) correlations, respectively, with water column nitrification rates. For water, both Ra and Rn occurred at similar rates in our study area. In sediment, nitrifying activity (SEDn) rates ranged from 0.34 to 8.69 nmol N g wet wt
−1
h
−1
. SEDn showed positive and negative correlations with sediment temperature (temp) and pH, respectively. Based on our observations, the average water column nitrification potential ranged from 43 to 420 nmol N L
−1
h
−1
considering three estuaries, while the sediment nitrification potential estimated at Saptamukhi estuary showed a value of 69 nmol N g wet wt
−1
h
−1
.
In situ concentration of transparent exopolymer particles (TEP) are usually associated with phytoplankton dominated by diatoms and their release of precursor polysaccharide material in the aquatic ...system. Here, we present temporal data on TEP variation and related habitat parameters for waters surrounding mangroves in the Sundarbans located at the coastal boundary of the Ganges River delta. Over three study years (2009–2011), TEP concentration was highest during the post-monsoon period and was mainly a function of phytoplankton production. The most common diatom species (by percentage of relative abundance) were Skeletonema cf. costatum (Cleve 1873), Ditylum brightwellii (Gosse 1850), and Chaetoceros sp. During the post-monsoon, when phytoplankton was abundant TEP/Chl-a ratio was relatively low and as nutrients depleted from water, phytoplankton biomass declined subsequently, increasing mean TEP/Chl-a ratio in the pre-monsoon.
•TEP concentration related to phytoplankton abundance dominated by diatom.•The most common diatom species was Skeletonema cf. costatum (Cleve, 1873).•TEP concentration was highest during pre-monsoon relative to monsoon and post-monsoon.•TEP/Chl-a ratio was found to be low in nutrient enriched mangrove water.
A detailed study on potential sources, variation, and environmental effects of the rainwater ions was carried out at Lothian Island, Sundarban mangrove forest, India, during the southwest monsoon ...(June–September) in 2019. On an event basis, the maximum rainwater precipitation was observed 17.65 mm Day
−1
and a minimum of 1.02 mm Day
−1
. The maximum amount of total precipitation was recorded in the month of July (237 mm). The volume weighted mean (VWM) concentration shows that the total ionic composition was 93.7 μeq L
−1
, whereas the percentage contribution of the total ionic concentration is found to be 45.97% to anions and 54.02% to the cations. Temporal variation was observed between early (June- July) and late monsoon (August—September), which shows a high concentration of major ions in early monsoon and low concentration in late monsoon due to the washout of atmospheric particles with the frequent and increasing precipitation. The pH values of the 78% samples show neutral pH and neutralization factors (NF) followed a sequence of NF
Ca
˃NF
Mg
˃ NF
NH4
with factors of 0.77, 0.34, and 0.14 indicating Ca
2+
was the most potential species to balance the acidic ions (NO
3
−
, SO
4
2−
) over the study area. Source apportionment study indicates the significant influence of marine actions (long-range transport by monsoonal wind from marine origin, Sea spray, salty soil profile of mangrove) as the major source of ions over Sundarban. The rate of nutrient wet deposition in the form of rainwater was estimated and average monsoonal nitrogen flux was observed 0.87 kg ha
−1
where NO
3
contributes the most (0.60 kg ha
−1
). N and P deposition flux also showed a simultaneous pattern with the seasonal nutrient concentration of surrounding river water, which may be an indication of a possible contribution of atmospheric wet deposition in the spike of monsoonal nutrient concentration in river water.
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.
This study presents data for the abundance of phytoplankton and zooplankton and related habitat parameters for Lothian Island mangrove ecosystem located at the coastal boundary of the Ganges River ...delta. Over the 3 study years, total abundance of phytoplankton and zooplankton was lowest during the monsoon period. In 2008, the most common diatom genera (by % relative abundance) were
Skeletonema
cf.
costatum
(14.2),
Thalassiothrix
(9.36),
Nitzschia sigma
(8.16),
Coscinodiscus radiatus
(7.65),
Chaetoceros
(6.64),
Pleurosigma
(3.05),
Thalassionema
(1.77),
Ditylum brightwellii
(1.71), and
Cyclotella
(1.0), whereas in 2010 they were
Skeletonema
cf
. costatum
(41.7),
Chaetoceros
(11.1),
Thalassiothrix
(6.04),
Nitzschia sigma
(4.49),
Coscinodiscus radiatus
(3.96),
Cyclotella
(2.61),
Thalassionema
(2.11),
Pleurosigma
(1.22) and,
Ditylum brightwellii
(1.01). Relative abundance of the zooplankton size classes typically followed the order meso > micro > macro and Copepods were the most abundant taxa (54.6 % of total zooplankton abundance). Total abundance of both phyto and zooplankton almost doubled in 2010 relative to 2008 although the ratio of the two remained constant (Zooplankton: phytoplankton = 0.002). The N:P ratio of water did not change much over the study and did not seem to be responsible for phytoplankton abundance changes; rather interannual variations in phytoplankton abundance could be explained by a simple predator–prey-relationship with zooplankton.
The extent of toxic metalloid retention and bioavailability and mobility in the sediment is of interest for understanding their biogeochemical cycling and for accurate risk assessment in an ...ecosystem. Intensification of monsoon and rainfall, believed to be related to global warming, could drive future changes of temperature, salinity, and pH distribution pattern affecting antimony cycling in the Sundarbans. This study investigated sorption kinetics of antimony (Sb) (III and V) as a function of temperature, salinity, and pH following the Langmuir model, and demonstrated that clayey silt type mangrove sediment was an effective adsorbent with higher efficiency for Sb (V) than Sb (III). Background level of Sb in the sediment was 0.35-0.78% of the maximum adsorption capacity (Γ
m
). Out of the two distinct type of sorption sites governing mobility and bioavailability of Sb in the sediment, site 1 (Humic acid) showed higher affinity for Sb than the site II (oxyhydroxide). Sb adsorption was strongly influenced by temperature, salinity, and pH, which may be altered by long-term changes in climate and rainfall pattern.
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.
Expansion of shrimp-based aquaculture in Sundarban is one of the major causative factors for the degradation of mangroves though has proven positive impact on aquaculture. In order to understand the ...perception of the local coastal community on the contribution of Mangrove Ecosystem Service in brackish water aquaculture in Indian Sundarban, a situational analysis was carried out in 2019-2020 with 30 farmers of Kultali block under South 24 Parganas district of West Bengal. Based on the descriptive and inferential statistical analysis of the data collected from aquaculture pond owners, it was observed that the smaller farms, located in the vicinity of the mangroves (<50 mts from the mangrove creek) showed significant benefits through higher yield and lower operational costs. The results also showed that the farmers were not adequately aware of ecosystem benefits and the need to conserve mangroves for sustainable pond-based aquaculture.
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