This document analyzes soil samples from 12 stations across the Indian Sundarbans for organic carbon content, bulk density, and organic carbon density over different seasons and soil depths. Higher organic carbon density is found in stations of the western Sundarbans, which is closer to urban areas with more anthropogenic activities. The eastern Sundarbans exhibits lower organic carbon density as it is located further within the protected forest area with minimal human influence. Organic carbon and density decrease with increasing soil depth, while bulk density increases at lower depths. Significant spatial variation is observed in soil organic carbon and density across the study area.

1. 1 23
National Academy Science Letters
ISSN 0250-541X
Volume 35
Number 3
Natl. Acad. Sci. Lett. (2012) 35:147-154
DOI 10.1007/s40009-012-0046-6
Spatial Variation in Organic Carbon
Density of Mangrove Soil in Indian
Sundarbans
Abhijit Mitra, Kakoli Banerjee & Saurov
Sett

2. 1 23
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3. RESEARCH ARTICLE
Spatial Variation in Organic Carbon Density of Mangrove Soil
in Indian Sundarbans
Abhijit Mitra • Kakoli Banerjee • Saurov Sett
Received: 5 March 2012 / Accepted: 19 May 2012 / Published online: 14 June 2012
Ó The National Academy of Sciences, India 2012
Abstract Soils from intertidal mudflats of mangrove
dominated Indian Sundarbans were analyzed for soil
organic carbon, bulk density and organic carbon density
during 2009 in two different sectors: western and eastern.
Samplings were carried out at 12 stations in four different
depths (0.01–0.10, 0.10–0.20, 0.20–0.30 and 0.30–0.40 m)
through three seasons (pre-monsoon, monsoon and post-
monsoon). High organic carbon density is observed in the
stations of western Indian Sundarbans, which is relatively
close to the highly urbanized city of Kolkata, Howrah and
the newly emerging Haldia port-cum-industrial complex.
The mangrove forest in the eastern Indian Sundarbans
exhibits comparatively lower organic carbon density.
Anthropogenic activities are almost negligible in this sector
because of its location almost within the protected forest
area. The bulk density of the mangrove soil increased with
depth, while organic carbon and carbon density decreased
with depth almost in all the stations. We observed signif-
icant spatial variations in soil organic carbon and organic
carbon density in the study area.
Keywords Sundarban mangrove Á
Soil organic carbon (SOC) Á Bulk density Á
Organic carbon density (OCD) Á Spatial variation
Introduction
Human activities have led to considerable emissions of
greenhouse gases [1]. In particular, for the period from 1980
to 1989 carbon dioxide emission from fossil-fuel burning
and tropical deforestation amounted to 7.1 billion tons of
carbon being released a year (Table 1) [2]. Increase in
atmospheric carbon dioxide concentration can account for
about half of the carbon dioxide emission for this period [3].
This has led to study the capacity of carbon sequestration in
forests and other terrestrial and wetland ecosystems. Most
of the studies so far available are related to forest ecosys-
tems and crops, and there is not enough information on
carbon sequestration potential of wetland soil. Wetlands
provide several important ecosystem services, among which
soil carbon sequestration is most crucial particularly in the
backdrop of rising carbon dioxide in the present century.
Wetlands cover about 5 % of the terrestrial surface and are
important carbon sinks containing 40 % of SOC at global
level [4]. Estuarine wetlands have a capacity of carbon
sequestration per unit area of approximately one order of
magnitude greater than other systems of wetlands [5] and
store carbon with a minimum emission of greenhouse gases
due to inhibition of methanogenesis because of sulphate [6].
The reservoirs of SOC, however, can act as sources or sinks
of atmospheric carbon dioxide, depending on land use
practices, climate, texture and topography [7–10].
Vertical patterns of SOC can contribute as an input or
as an independent validation for biogeochemical models
and thus provide valuable information for examining
the responses of terrestrial ecosystems to global change
[11–13]. A large number of biogeochemical models, how-
ever, do not contain explicit algorithms of below-ground
ecosystem structure and function [14]. Most of the studies
primarily focused on the topsoil carbon stock, and carbon
A. Mitra (&) Á S. Sett
Department of Marine Science, University of Calcutta,
35 B.C. Road, Kolkata, West Bengal 700 019, India
e-mail: abhijit_mitra@hotmail.com
K. Banerjee
School for Biodiversity and Conservation of Natural Resources,
Central University of Orissa, Landiguda, Koraput 764020, India
123
Natl. Acad. Sci. Lett. (May–June 2012) 35(3):147–154
DOI 10.1007/s40009-012-0046-6
Author's personal copy

4. dynamics in deeper soil layers and driving factors behind
vertical distributions of soil organic carbon remain poorly
understood [11, 15, 16]. Thus, improved knowledge of dis-
tributions and determinants of SOC across different soil
depth is essential to determine whether carbon in deep soil
layers will react to global change and accelerate the increase
in atmospheric carbon dioxide concentration [16, 17].
With this background the present study was undertaken to
estimate the SOC in four different depths in the mangrove
dominated Indian Sundarbans that sustains some 34 true
mangrove species and some 62 mangrove associate species
[18]. This deltaic lobe together with Bangladesh Sundarbans
constitutes the world’s largest brackish water wetland. Hence
it is essential to establisha base linedata of soil carbon pool of
this mangrove ecosystem. In this study, we used our unpub-
lished data of SOC and bulk density to evaluate the spatial
variations of OCD in the intertidal mudflats of western and
eastern Indian Sundarbans that are markedly different with
respect to anthropogenic activities and mangrove vegetation.
Materials and Methods
The Study Area
The Sundarban mangrove ecosystem covering about one
million ha in the deltaic complex of the Rivers Ganga,
Brahmaputra and Meghna is shared between Bangladesh
(62 %) and India (38 %) and is the world’s largest coastal
wetland. Enormous load of sediments carried by the rivers
contribute to its expansion and dynamics.
The Indian Sundarbans (between 21°130
N and 22°400
N
latitude and 88°030
E and 89°070
E longitude) is bordered by
Bangladesh in the east, the Hooghly River (a continuation of
the River Ganga) in the west, the Dampier and Hodges line in
the north, and the Bay of Bengal in the south. The important
morphotypes of deltaic Sundarbans include beaches, mud-
flats, coastal dunes, sand flats, estuaries, creeks, inlets and
mangrove swamps [19]. The temperature is moderate due to
its proximity to the Bay of Bengal in the south. Average
annual maximum temperature is around 35 °C. The summer
(pre-monsoon) extends from the mid of March to mid-June,
and the winter (post-monsoon) from mid-November to
February. The monsoon usually sets in around the mid of
June and lasts up to the mid of October. Rough weather with
frequent cyclonic depressions occurs during mid-March to
mid-September. Average annual rainfall is 1,920 mm.
Average humidity is about 82 % and is more or less uniform
throughout the year. This unique ecosystem is also the home
ground of Royal Bengal Tiger (Panthera tigris tigris). The
deltaic complex sustains 102 islands, 48 of which are
inhabited. The ecosystem is extremely prone to erosion,
accretion, tidal surges and several natural disasters, which
directly affect the top soil and the subsequent carbon density.
The average tidal amplitude is around 3.0 m.
We conducted survey at 12 stations in the Indian
Sundarbans region through three seasons viz. pre-monsoon
(May), monsoon (September) and post-monsoon (Decem-
ber) in 2009. Station selection was primarily based on
anthropogenic activities and mangrove floral diversity.
Because of rapid industrialization, urbanization, unplanned
tourism, navigational, pilgrimage and shrimp culture activi-
ties; the western Indian Sundarbans is a stressed zone (Stn.
1–6). On the contrary stations 7–12 (in the eastern sector)
are the areas with rich mangrove biodiversity and have been
considered as control zone in this study. The major activi-
ties influencing the carbon pool in the selected stations are
highlighted in (Table 3).
Sampling
Table 2 and Fig. 1 represent our study site in which sam-
pling plots of 10 9 5 m2
were considered for each station.
Table 1 Anthropogenic carbon fluxes; 1980–1989 (IPCC 1994)
GtC/year
Carbon dioxide sources
Fossil-fuel burning, cement production 5.5 ± 0.5
Changes in tropical land use 1.6 ± 1.0
Total anthropogenic emission 7.1 ± 1.1
Partitioning among reservoirs
Storage in the atmosphere 3.2 ± 0.2
Oceanic uptake 2.0 ± 0.8
Uptake by northern hemisphere forest regrowth 0.5 ± 0.5
Additional terrestrial sinks: CO2 fertilization, nitrogen
fertilization, climatic effects
1.4 ± 1.5
Table 2 Sampling stations in western and eastern Indian Sundarbans
Station Station no. Geographical location
Longitude Latitude
Kachuberia Stn. 1 88°080
04.4300
21°520
26.5000
Harinbari Stn. 2 88°040
52.9800
21°470
01.3600
Chemaguri Stn. 3 88°100
07.0300
21°390
58.1500
Sagar south Stn. 4 88°030
06.1700
21°380
54.3700
Lothian island Stn. 5 88°220
13.9900
21°390
01.5800
Prentice island Stn. 6 88°170
10.0400
21°420
40.9700
Burirdabri Stn. 7 89°010
43.600
22°040
39.200
Sajnekhali Stn. 8 88°460
10.800
22°050
13.400
Amlamethi Stn. 9 88°440
26.700
22°030
54.200
Dobanki Stn. 10 88°450
20.600
21°590
24.400
Netidhopani Stn. 11 88°440
39.400
21°550
14.900
Haldibari Stn. 12 88°460
44.900
21°430
01.400
148 Natl. Acad. Sci. Lett. (May–June 2012) 35(3):147–154
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5. Care was taken to collect the samples within the same
distance from the estuarine edge, tidal creeks and the same
micro-topography. Under such conditions, spatial vari-
ability of external parameters such as tidal amplitude and
frequency of inundation [20], inputs of material from the
adjacent bay/estuary and soil granulometry and salinity
[21, 22] are minimal.
Ten cores were collected from the selected plots in each
station by inserting PVC core of known volume into the
soil to a maximum depth of 0.40 m during low tide con-
dition. Each core was sliced in 0.10 m layers up to 0.40 m
depth. The uppermost 0.01 m, which frequently includes
debris and freshly fallen litter, was not used in this study.
Each core section was placed in aluminum foil and packed
Fig. 1 Map of the study region
showing the sampling stations
0
0.2
0.4
0.6
0.8
1
1.2
1.4
88°08'04.43"E&
21°52'26.50"N
88°04'52.98"E&
21°47'01.36"N
88°10'07.03"E&
21°39'58.15"N
88°03'06.17"E&
21°38'54.37"N
88°22'13.99"E&
21°39'01.58"N
88°17'10.04"E&
21°42'40.97"N
89°01'43.6"E&
22°04'39.2"N
88°46'10.8"E&
22°05'13.4"N
88°44'26.7"E&
22°03'54.2"N
88°45'20.6"E&
21°59'24.4"N
88°44'39.4"E&
21°55'14.9"N
88°46'44.9"E&
21°43'01.4"N
SOC%
pre monsoon
monsoon
post monsoon
Fig. 2 Spatial and seasonal
variation of SOC (mean of four
depths each)
Fig. 3 Shoreline changes of Sagar Island (Stn. 4) during 1955–1989
showing erosion of the southern part of the island
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6. in ice for transport. In the laboratory, the collected samples
were carefully sieved and homogenized to remove roots
and other plant and animal debris prior to oven-drying to
constant weight at 105 °C for bulk density determination
considering the volume of the PVC core. SOC of the col-
lected samples (n = 10) from each plot was analyzed by
standard method [23] and the mean value was considered
for determination of OCD in (kg/m2
) as per the expression:
OCD ¼ % SOC Â bulk density BDð Þ Â soil depth
Results and Discussion
Organic Carbon
The organic carbon in soil differs significantly between sta-
tions. It is observed that the western Indian Sundarbans (Stn.
1–6) has an average SOC of 0.87 %, whereas in eastern
Indian Sundarbans (Stn. 7–12), the value is 0.55 %. These
figures are average of three seasons and four depths. The
spatial trend of SOC follows the order Stn. 3 (1.05 %) [ Stn.
1 (1.01 %) [ Stn. 5 (0.84 %) [ Stn. 6 (0.81 %) [ Stn. 2
(0.78 %) [ Stn. 4 (0.72 %) [ Stn. 8 (0.61 %) [ Stn. 11
(0.60 %) [ Stn. 9 (0.58 %) [ Stn. 10 (0.57 %) [ Stn. 12
(0.50 %) [ Stn. 7 (0.44 %) (Fig. 2). The significant spatial
variation of SOC between western and eastern sectors
(p = 0.005428) may be attributed to a large extent by man-
grove diversity, anthropogenic activity, accretion and erosion
processes (Table 4). Anthropogenic activities like fish land-
ing, tourism, urban development and shrimp farms contribute
appreciable amount of organic load in stations like Kachu-
beria (Stn. 1) and Chemaguri (Stn. 3). The presence of shrimp
farms at Chemaguri (Stn. 3) along with 12 years old man-
grove vegetation (17 species) may be attributed to highest
organic carbon level in the soil core. The relatively low SOC
at Sagar South (Stn. 4) is due to its location at sea front where
wave action and tidal amplitude is maximum (*3.5 m mean
amplitude). This station experiences the freshwater discharge
from the Farakka barrage (located in the upstream zone),
which is about 40,000 cusec/day. This huge quantum of fresh
water discharge through the Hooghly channel also causes
erosion of the Sagar Island. Continuous erosion of the
southern part of this island may be the reason behind mini-
mum retention of organic matter in the intertidal zone
(Fig. 3). The variation of SOC in the Indian Sundarbans is
thus regulated through an intricate interaction of biological,
physical and anthropogenic activities (Table 3).
The factors governing variation of below-ground carbon
storage in mangrove soils is difficult to pinpoint [24, 25] as
Table 3 Major activities influencing the SOC in Indian Sundarbans
Station Major activity Magnitude
Kachuberia station 1 Prawn seed collection ??
Mangrove vegetation (5 species) ?
Passenger vessel jetties ???
Fish landing activities ?
Market related activities ??
Harinbari station 2 Mangrove vegetation (11
species)
???
Prawn seed collection ?
Fish landing activities ?
Chemaguri station 3 Mangrove vegetation (17
species)
???
Unorganized fishing activities ??
Market related activities ??
Sagar south station 4 Pilgrims ???
Tourism ???
Navigational channel ???
Erosion (sea facing) ???
Mangrove vegetation (11
species)
???
Lothian island station
5
Biodiversity research and study ?
Mangrove vegetation (27
species)
???
Prawn seed collection ?
Prentice island station
6
Mangrove vegetation (25
species)
???
Burirdabri station 7 Mangrove vegetation (17
species)
???
Sajnekhali station 8 Mangrove vegetation (25
species)
???
Tourism ???
Amlamethi station 9 Mangrove vegetation (24
species)
???
Dobanki station 10 Mangrove vegetation (24
species)
???
Netidhopani station 11 Mangrove vegetation (25
species)
???
Haldibari station 12 Mangrove vegetation (25
species)
???
?, ??, and ??? indicate low, medium and high magnitude
respectively for the major activities in the selected stations
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Western Eastern
SOC%
0 to 10cm
10 to 20cm
20 to 30cm
30 to 40cm
Fig. 4 Depth profile of SOC in western and eastern Indian
Sundarbans (mean of 3 seasons and 6 stations in each sector)
150 Natl. Acad. Sci. Lett. (May–June 2012) 35(3):147–154
123
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7. it is not a simple function of measured flux rates, but also
integrates thousands of years of variable deposition,
transformation, and erosion dynamics associated with
fluctuating sea levels and episodic disturbances [26]. The
mean value of SOC considering all the six stations and
seasons in western Indian Sundarbans shows a decrease
with depth (Fig. 4). Similar trend is also observed in
eastern Indian Sundarbans (Stn. 7–12) where there is
almost no anthropogenic impact (Fig. 4). The organic
carbon levels under Rhizophora mangle soil were 2.80,
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
88°08'04.43"E&
21°52'26.50"N
88°04'52.98"E&
21°47'01.36"N
88°10'07.03"E&
21°39'58.15"N
88°03'06.17"E&
21°38'54.37"N
88°22'13.99"E&
21°39'01.58"N
88°17'10.04"E&
21°42'40.97"N
bulkdensityingm/cc
0 to 10cm
10 to 20cm
20 to 30cm
30 to 40cm
Fig. 5 Depth wise variation of
bulk density in western Indian
Sundarbans
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
89°01'43.6"E&
22°04'39.2"N
88°46'10.8"E&
22°05'13.4"N
88°44'26.7"E&
22°03'54.2"N
88°45'20.6"E&
21°59'24.4"N
88°44'39.4"E&
21°55'14.9"N
88°46'44.9"E&
21°43'01.4"N
Bulkdensityingm/cc
0 to 10cm
10 to 20cm
20 to 30cm
30 to 40cm
Fig. 6 Depth wise variation of
bulk density in eastern Indian
Sundarbans
Table 4 ANOVA for spatial variation of SOC and OCD
Source of variation SS df MS Fobs P value Fcrit
SOC
Between western and eastern sector 0.302961 1 0.302961 21.91293 0.005428 6.607891
Between stations 0.037367 5 0.007473 0.540547 0.742047 5.050329
OCD
Between Western and Eastern sector 0.607181 1 0.607181 18.1139 0.008045 6.607891
Between stations 0.108846 5 0.021769 0.649437 0.676359 5.050329
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 to 10cm 10 to 20cm 20 to 30cm 30 to 40cm
Carbondensityinkg/sqm
western
eastern
Fig. 7 Depth profile of OCD in
western and eastern Indian
Sundarbans (mean of 3 seasons
and 6 stations in each sector)
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123
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8. 2.70 and 2.70 % in the 0.01–0.05, 0.05–0.10 and
0.10–0.15 m depth respectively [27]. Similar decrease of
SOC with depth was also observed under Avicennia soil
[27]. Report of decreasing mangrove SOC below 1 m was
also documented in several mangrove ecosystems [28].
Seasonal variation of SOC (pre-monsoon [ post-
monsoon [ monsoon) in the present study area (Fig. 2) is
attributable to the climatic conditions that influence the
physical processes like waves, tidal amplitude and current
pattern. Heavy rainfall in monsoon (80 % during July–
September) coupled with high tidal amplitude (4.8–5.2 m
during spring tide and 2.1–2.8 m during neap tide) erode
the top soil and wash away the deposited organic matter
and mangrove litter to the adjacent aquatic system.
It is interesting to note that SOC in western Indian
Sundarbans is 57.21 % higher than the eastern sector. The
stations in the eastern Indian Sundarbans are within the
Reserve forest area, with almost minimum or no anthro-
pogenic activities. The SOC in these stations is almost
exclusively contributed by mangrove vegetation (through
litter and detritus). The stations in western Indian
Sundarbans are highly stressed due to intense anthropo-
genic activities. The high values of SOC in stations like
Chemaguri (Stn. 3) and Kachuberia (Stn. 1) are due to
organic load contributed from market wastes and decom-
posed fish wastes. Thus anthropogenic factors act as
additive to increase the SOC level in the deltaic complex of
Indian Sundarbans.
Bulk Density
The bulk density of mangrove soil is attributable to the
relative proportion of sand, silt and clay and more specif-
ically to the specific gravity of solid organic and inorganic
particles and porosity of the soil. The compactness of
mangrove soil increases with depth both in western and
eastern Indian Sundarbans due to which the bulk density
exhibits higher values with depths in all the stations
0
0.5
1
1.5
2
2.5
88°08'04.43"E&
21°52'26.50"N
88°04'52.98"E&
21°47'01.36"N
88°10'07.03"E&
21°39'58.15"N
88°03'06.17"E&
21°38'54.37"N
88°22'13.99"E&
21°39'01.58"N
88°17'10.04"E&
21°42'40.97"N
89°01'43.6"E&
22°04'39.2"N
88°46'10.8"E&
22°05'13.4"N
88°44'26.7"E&
22°03'54.2"N
88°45'20.6"E&
21°59'24.4"N
88°44'39.4"E&
21°55'14.9"N
88°46'44.9"E&
21°43'01.4"N
carbondensityinkg/sqm
pre monsoon
monsoon
post monsoon
Fig. 8 Spatial and seasonal
variation of OCD (mean of 4
depths each)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
Estuarineoceanic
soil
RainforestinOhio,
USA
Wetlandsatthe
southeasternUSA
Mangrovesin
Okinawa,Japan
Wetlandsatthe
southeastern
Australia
WesternIndian
Sundarbans
EasternIndian
Sundarbans
Carbondensityinkg/sqm
BernalandMisch(2008)
BrevikandHomburg(2004)
Khanandcolaborators(2007)
Howeandcolaborators(2009)
ourstudy
ourstudy
Donatoetal.(2011)
Fig. 9 Comparison of our
study with that of others
152 Natl. Acad. Sci. Lett. (May–June 2012) 35(3):147–154
123
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9. (Figs. 5, 6). Basically the bulk density in the present study
area is regulated by sediment texture and deposition/
erosion which is the effect of current pattern, tidal ampli-
tude and wind action.
Organic Carbon Density
OCD being a direct function of SOC and bulk density
exhibits almost similar spatial variation to that of SOC.
The OCD differs significantly between stations and sectors.
It is observed that the western Indian Sundarbans (Stn. 1–6)
has an average OCD of 1.19 kg/m2
, whereas in eastern
Indian Sundarbans (Stn. 7–12), the value is 0.74 kg/m2
.
These figures are average of three seasons and all four
depths. The spatial trend of OCD is in the order Stn. 3
(1.55 kg/m2
) [ Stn. 1 (1.36 kg/m2
) [ Stn. 5 (1.14 kg/m2
)
[ Stn. 6 (1.09 kg/m2
) [ Stn. 2 (1.03 kg/m2
) [ Stn. 4
(0.99 kg/m2
) [ Stn. 10 (0.84 kg/m2
) [ Stn. 8 (0.83
kg/m2
) [ Stn. 9 (0.79 kg/m2
) [ Stn. 11 (0.73 kg/m2
) [
Stn. 12 (0.66 kg/m2
) [ Stn. 7 (0.61 kg/m2
). The significant
spatial variation of OCD between western and eastern sec-
tors (p = 0.008045) (Table 4) may be attributed to man-
grove diversity and nature of anthropogenic activities as
mentioned in Table 3. It is observed that the OCD of western
sector is 60.26 % higher than that of the eastern sector
confirming the fact that anthropogenic factors significantly
contribute to OCD value (Fig. 7). The seasonal variation
(pre-monsoon [ post-monsoon [ monsoon) can be related
to heavy rain and high water current that washes away the
organic matter from the intertidal mudflats (Fig. 8).
We compared our carbon density data (ranging from
0.61 to 1.55 kg/m2
) with several global reports published
between 2004 and 2011. OCD of 3.03, 0.033, 5.73, 6.61
and 0.38 kg/m2
were observed in rain forest of Ohio, USA
[29]; wetlands at the southeastern USA [30]; mangroves in
Okinawa, Japan [31]; wetlands at the southeastern Aus-
tralia [32] and estuarine oceanic soil [28] respectively
(Fig. 9). Even though our study area does not have highest
OCD, it neither has the least. The relatively higher OCD
value in the western sector is the effect of anthropogenic
activities, which is non-existent in the stations of eastern
sector because of their location within the protected reserve
forest.
The present study is significant from the point that the
area has not yet witnessed the light of documentation of
soil carbon content although above ground mangrove bio-
mass (AGMB) and carbon storage have been studied by
several workers [33, 34]. A thorough study has been done
on the whole-ecosystem C storage in mangroves across a
broad tract of the Indo-Pacific region, the geographic core
of mangrove area (40 % globally) and diversity and the
study sites comprised wide variation in stand composition
and stature spanning 30° of latitude (8°S–22°N), 73° of
longitude (90°–163°E), and including eastern Micronesia
(Kosrae); western Micronesia (Yap and Palau); Sulawesi,
Java, Borneo (Indonesia); and the Sundarbans (Ganges–
Brahmaputra Delta, Bangladesh) [28]. The study, however,
left out the lower Gangetic region sustaining the Indian
Sundarbans. The present approach is thus an attempt to fill
this gap area and establish a baseline data of SOC and OCD
in the mangrove dominated Indian part of Sundarbans.
Acknowledgments The financial assistance from the National
Remote Sensing Centre (NRSC), Govt. of India under the programme
ISRO-GBP/NCP/SVF is gratefully acknowledged. The infrastructural
support from the Forest Department, Govt. of West Bengal is duly
acknowledged.
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