Vol.1, No.3, 65-72 (2011)
http://dx.doi.org/10.4236/oje.2011.13009
Open Journal of Ecology
C
opyright © 2011 SciRes.
Depth profile exploration of enzyme activity and
culturable microbial community from the
oxygen-starved soil of Sundarban
mangrove forest, India
Subhajit Das1, Tarun kumar Sarkar2, Minati De3, Dipnarayan Ganguly1, Tusher kanti Maiti4,
Abhishek Mukherjee1, Tapan kumar Jana1, Tarun Kumar De1*
1Department of Marine Science, Calcutta University, Calcutta, India;
*Corresponding Author: [e-mail]; [e-mail]
2Department of Community Medicine, North Bengal Medical College, Darjeeling, India;
3Maniktala Siksha Bhavan, Calcutta, India;
4Microbiology Laboratory, Department of Botany, Burdwan University, Burdwan, India.
Received 23 August 2011; revised 26 September 2011; accepted 16 October 2011.
ABSTRACT
Populations of culturable microbes and active-
ties of dehydrogenase & β-D glucosidase were
found maximum in surface soil and decreased
with increase in depth in Sundarban mangrove
environment. The maximum (13.529 × 106 C.F.U
g–1 dry weight of soil) and minimum (11.547 × 106
C.F.U g–1 dry weight of soil) total microbial po-
pulations in surface soil were recorded during
post-monsoon and monsoon respectively. At 60
cm depth, the minimum (6.396 × 106 C.F.U g–1
dry weight of soil) and maximum (8.003 × 106
C.F.U g–1 dry weight of soil) numbers of total
microbial po pulatio ns were observ ed du ring mon -
soon and post-monsoon respectively. A decrea-
sing trend of total microbial load, enzyme activi-
ties and nutrient status with organic carbon were
found w ith increase in depth throughout the year.
Present study revealed the relationship among
depth integrated variations of physico-chemical
components (viz. soil temperature, pH, moisture,
organic-C, Nitrate-Nitrogen, and available-P) and
microbial populations as well as activity of de-
hydrogenase and
 -D glucosidase enzy mes.
Keyw ords: Sundarban; Mangrove Sediment;
Enzyme Activities; Depth; Microbial Populations
1. INTRODUCTION
The distribution of microbial activities in estuarine
systems is clearly complex and variable. Much research
remains to be done in order to define the distributions of
microbial activities and the major factors involved in
controlling these distributions in estuaries. Mangroves
are highly productive marine ecosystem where bacteria
actively participate in bio-mineralization and biotrans-
formation of minerals. [1]. Leaves and wood provided
by mangrove plants to the sediment are degraded prima-
rily by large variety of microbes and their active partici-
pation in the heterotrophic food chain [2-4]. Major pro-
ducts of general recycling of organic matter are detritus
which is rich in enzymes and proteins and contains large
microbial populations [5]. Bacteria are the major par-
ticipants in the Carbon, Sulphur, Nitrogen and Phosphor-
rous cycles in mangrove forest [6,7]. Bacterial activities
are responsible for most of the carbon recycling in man-
grove sediment under both in oxic and anoxic condition.
Sulfate reduction, methane production, and denitrifica-
tion are the important processes for the terminal electron
removal during decomposition of organic matter in an-
oxic environment. It has been studied that N2 fixation by
heterotrophic bacteria are generally regulated by specific
environmental factors like O2, combined N2 and the
availability of carbon source for energy requirement [8].
Aerobic, autotrophic nitrifiers (nitrifying bacteria) oxi-
dize NH3 to 2
NO

and 3, with molecular oxygen as
electron acceptor. Nitrite and nitrate are reduced to
gaseous di-nitrogen by heterotrophic denitrifying bacte-
ria which use NOx instead of oxygen as electron accep-
tor [9,10]. These estimations of enzyme activities and
CO2 emission provide an index of microbial dynamics.
These estimations also provide an insight into the rates
of organic matter breakdown and mineralization. Sea-
sonal variation in soil enzyme activity is biologically
important because they, along with the changes in the
NO 

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72 66
amount and condition of the substrate upon which they
act, are indicative of the changes in rate of soil processes.
Dehydrogenase activity plays an essential role in the
initial stages of oxidation of soil organic matter. It de-
pends more upon the metabolic state of the microbial
population than the activity of free enzymes available in
the soil. Urease and Phosphatase act as intermediary
enzymes in the transformation of organic Nitrogen and
Phosphorous into inorganic forms [11]. A number of
studies in soil enzyme activity with physico-chemical
parameters and biological distinctiveness of soils is not
implicated. The purpose of the present study was to look
into seasonal and depth wise variations in microbial
population, interaction with physico-chemical features
and the activities of the enzymes from the oxygen-star-
ved soil of the Sundarban Mangrove Forest, India.
2. METHODS AND MATERIALS
2.1. Study Area
The Sundarban Mangrove forest is located geogra-
phically in between 21˚31'N and 22˚30'N and longitude
88˚10'E and 89˚51'E along the North East coast of Bay
of Bengal, India. This mangrove forest is a part of the
estuarine system of the River Ganges, NE coast of Bay
of Bengal (Figure 1), which covers 9630 km2. Several
numbers of discrete islands constitute Sundarbans. The
climate in the region is characterized by the southwest
monsoon (June-September), northeast monsoon or post-
monsoon (October-January), and pre-monsoon (February-
May); 70% - 80% of annual rainfall occurs during the
summer monsoon (southwest monsoon), The tide in this
estuarine complex is semidiurnal in nature with spring
tide ranging between 4.27 m and 4.75 m and neap tide
range between 1.83 m and 2.83 m. It is a unique biocli-
matic zone in between the land and ocean boundaries of
the Bay of Bengal and the largest delta on the globe. The
deltaic terrain of Sundarban Biosphere Reserve comprises
mainly saline alluvial soil consisting of clay, silt, fine and
coarse sand particles.
2.2. Sample Collection
Soil samples were collected aseptically using a hand-
held stainless steel core sampler (3.2 cm diameter, 100
cm long) from six different depth i.e. 1) 0 - 10 cm, 2) 10
- 20 cm, 3) 20 - 30 cm, 4) 30 - 40 cm, 5) 40 - 50 cm & 6)
50 - 60 cm) at five different sites in Sundarban, covering
different seasons. Three replicates from each site were
analyzed for five sites at different depths. The result
represents the average value at each depth.
2.3. Quantification of Bacteria
Quantification of Bacteria: Sediment samples were
Figure 1. The map is showing the study area.
stored at 4˚C immediately after collection and transpor-
ted with adequate care to the laboratory for analysis. For
quantification of different types of bacteria we followed
the procedure as described by Ramnathan et al.; 2008
[12]. We homogenized 10 gm of the samples collected
from different locations in sterile phosphate buffer solu-
tion. Serial dilutions up to 10–4 were made and inocula-
tion was done with 0.1ml homogenized sample. For quan-
tification of free-living Nitrogen fixers, inoculations from
each zone were done in a selective medium, comprising
Mannitol (15.0 gms), K2HPO4 (0.5 gms), MgSO4·7 H2O
(0.2 gms), CaSO4 (0.1 gms), NaCl (0.2 gms), CaCO3
(5.0 gms), Agar (15.0 gms), Isotonic solution with the
soil was prepared with NaCl and sterilized distilled wa-
ter (1lt) and pH maintained at 8.3. Phosphate solubiliz-
ing bacteria (PSB) were enumerated using Pikovskaya’s
medium that had the following composition: Glucose
(10 gm), Ca3 (PO4)2 (5 gm), (NH4)2SO4 (0.5 gm), KCl
(0.2 gm), Agar (20 gm), Isotonic solution with the soil
was prepared with NaCl and sterilized distilled water (1lt)
and pH maintained at (6.8 - 7.0). Cellulose decomposing
bacteria (CDB) were isolated and quantified in selective
media containing K2HPO4 (1.0 gms), CaCl2 (0.1 gms),
MgSO4·7 H2O (0.2 gms), NaCl (0.1 gms), FeCl3 (0.02
gms), NaNO3 (2.0 gms), Agar (12.0 gms). Precipitated
cellulose (4.0 gms), Isotonic solution with the soil was
prepared with NaCl and sterilized distilled water (1 lt).
Fungi were enumerated in the Czapedox agar media,
which contained NaNO3 (3.0 gm), KH2PO4 (1.0 gm),
MgSO4.7H2O (0.5 gm), KCl (0.5 gms), FeSO4·7H2O
(0.01 gms), Sucrose (30 gms), Agar (15 gms), ZnSO4·7H2O
(0.05 gms), Isotonic solution with the soil prepared from
NaCl and sterilized distilled water (1 l tr) [12]. The ni-
trifying bacteria were quantified on Winogardsky’s me-

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72
6767
electrode was checked before using the quinhydrone in
pH 4 and 7 buffers (mV reading for quinhydrone is 218
and 40.8, respectively, at 25˚C). The potential of a calo-
mel reference electrode (+244 mV) was added to each
value to calculate Eh value for the sediment samples
[20].
dium (g/l: K2HPO4 1, NaCl 2, MgSO4·7H2O 0.5, FeSO4·7H2O
trace, CaCl2·2H2O 0.02, pH 8.5) containing 1.0 g/l either
(NH4)2SO4 and the colonies were visualized (pinkish hue)
by flooding the plates with sulphanillic acid reagent
(sulphanillic acid 8 g/l acetic acid (5 M) and ά-na-
phthayl amine 5 g/l acetic acid (5 M); 1:1, v/v) [13].
Sulfate reducing bacteria (SRB) were cultured under
anaerobic condition for quantification in Starkey’s me-
dium containing K2HPO4, 0.5 gm; NH4Cl, 1 gm; Na2SO4,
1 gm; CaCl2·2H2O, 0.1 gm; MgSO4·7H2O, 2 gm; Sodium
Lactate (70% Solution), 5 gm; FeSO4·(NH4)2SO4·6H2O,
0.5 gm; Isotonic solution with the soil prepared from
NaCl and sterilized distilled water (1 L) and pH main-
tained at (7.0 - 7.5) [14].
2.5. Measurement of Enzyme Activity
Dehydrogenase activity assay: Moist 1 gm soil sample
from each depth was mixed with 1.5 ml TRIS buffer and
2ml 0.5% aqueous solution of iodonitrotetrazolium chlo-
ride (substrate). After 2 hr of incubation, the samples
were extracted by using 10 ml solution N,N-dimethyl-
formamide/ethanol in a 1:1 ratio. Produced iodonitro te-
trazolium formazan (INTF) were measured immediately
spectrophotometrically at 464 nm [21]. Determination of
β-D-Glucosidase activity: 1 gm of the collected soil
samples from different depth region were mixed with
acetate buffer. After 10min, p-nitrophenyl-β-Dglucopyranoside
(substrate) was added in required amount and incubated
at 37˚C temperature for 1 hour. Ethanol (95%) was ad-
ded in required amount to terminate the reaction. Relea-
sed para nitro phenol (PNP) was determined spectropho-
tometrically at 400 nm [22].
2.4. Sediment Quality Measurement
Concentrations of Sulphate-Sulphur, Nitrate-Nitrogen,
Nitrite-Nitrogen, Phosphate-Phosphorous, and Silicate-
Silica in the soil sediment sample were measured foll-
owing standard procedure [15,16]. The pH value was mea-
sured in a 1:5 (w/w) soil water suspension using an elec-
tric digital pH meter [17] and salinity of a soil saturation
extract (ECe) was determined by measuring the elec-
trical conductance of soil water saturation extract with
the help of a conductivity meter [18]. Soil organic car-
bon was measured by standard methods [19]. Soil redox
potentials (Eh) at each sampling site were measured with
brightened platinum electrodes which were allowed to
equilibrate in situ for 1 hr prior to measurement. Each
3. RESULT AND DISCUSSION
Ta bl e 1 depicts the seasonal variations of total micro-
bial populations, organic carbon content and physico-che-
Table 1. Seasonal variations of physico-chemical parameters and microbial population (CFU × 106·g–1 dry sediment) at different depth
in Sundarban mangrove environment.
Season Depth (cm) Eh (mV) pH Temp (˚C)Salinity (PSU)Org.C2
4
SO

3
4
PO

3
NO 
2
NO  CFU × 106
0 –98 7.94 17.83 16.97 1.031.830.3150.175 0.049 12.237
10 –102 8.39 17.83 17.01 0.971.640.3050.179 0.048 11.604
20 –108 8.27 17.82 17.08 0.921.420.3150.166 0.045 10.62
30 –112 8.23 17.82 17.23 0.821.380.3400.221 0.044 9.279
40 –128 8.25 17.82 17.35 0.781.290.3210.245 0.048 8.560
50 –136 8.21 17.80 17.84 0.751.210.2850.226 0.032 8.941
Pre-mon-soon
60 –143 8.19 17.82 17.87 0.701.070.2390.214 0.050 7.763
0 –102 8.22 24.68 14.99 0.871.040.3200.204 0.047 11.547
10 –112 8.12 24.71 15.05 0.821.000.2620.183 0.045 10.326
20 –135 8.19 24.67 15.05 0.800.890.2800.173 0.044 10.103
30 –148 8.18 24.69 15.17 0.830.910.2300.159 0.047 8.921
40 –165 8.14 24.59 15.22 0.700.820.2500.159 0.058 7.767
50 –173 8.16 23.82 15.28 0.670.940.2100.163 0.048 7.413
Mon-soon
60 –175
8.12 23.73 15.41 0.590.870.1900.162 0.048 6.396
0 –121 8.42 12.94 15.35 1.371.310.6750.205 0.024 13.529
10 –128 8.37 12.95 15.36 1.261.200.6120.197 0.014 12.183
20 –131 8.34 12.94 15.46 1.251.130.5660.171 0.013 10.958
30 –135 8.32 12.93 15.53 1.071.140.5110.176 0.021 10.743
40 –145 8.24 12.90 15.55 0.971.060.4410.151 0.021 9.576
50 –167 8.24 12.92 15.67 0.921.060.4430.136 0.019 9.008
Post-mon-soon
60 –187 8.19 13.12 15.69 0.930.940.3440.130 0.018 8.003

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72 68
mical parameters at various depths in Sundarban mangro-
ve sediment. Temperature and Eh values of soil samples
showed a decreasing trend from surface to a depth of 60
cm. A reverse profile was observed in case of pH and
salinity. During monsoon, the salinity was found to be
14.99 psu in surface soil and it was 15.41 psu at 60 cm
below surface. Less soil salinity in monsoon with respect
to pre-monsoon and post-monsoon may be due to high
degree of dilution by river (freshwater) run off during
monsoon period [23]. Eh value showed a decreasing
trend from surface soil (–98 mV) to the 60 cm depth
(–143 mV) which represented more anoxicity of bottom
soil than that of surface during pre-monsoon (Ta b l e 1 ).
Soil redox potential value (Eh) from surface to a region
of 60 cm of depth in three distinct seasons suggested that
the soil of deep forest region of Sundarban Mangrove is
relatively anoxic or it can be referred to as oxygen-im-
poverished or oxygen-starved soil.
Total number of microbial populations in surface soil
was found to be 12.237 × 106, 11.547 × 106 and 13.529 ×
106 (C.F.U g–1 dry wt. of sediment) compared to 7.763 ×
106, 6.396 × 106 & 8.003 × 106 (C.F.U g–1 dry wt. of se-
diment) at the 60 cm depth during pre-monsoon, mon-
soon and post-monsoon respectively (Table 1).
Depth profile exploration with respect to microbial
population showed an inverse relationship between the
total bacterial population and depth (cm) (Figure 2)
[The regression equation is, Total bacterial population
= 2.94187 + 7.55525 Organic C (%); F = 42.86; P =
0.000; n = 21] whereas a direct relationship is reflected
from the study between the total bacterial population and
organic C% throughout the year (Figure 3). [The regres-
sion equation is To tal bacterial populatio n = 12.2396 –
0.0818286 Depth (cm); F = 91.74; P = 0.000; n = 21].
During three seasons, the decrease in total microbial
population with increasing depth might be due to dep-
letion of organic carbon with increase in depth since
previous studies have revealed that organic carbon is
most significant for controlling microbial population
Figure 2. Relationship between Total CFUs (×106) and depth
(cm).
Figure 3. Relationship between Total CFUs (×106) and organic
carbon.
[24]. Decrease in Nitrate-Nitrogen concentration with in-
crease in depth (Table 1) could be explained by the
decrease in population of nitrifying bacteria with in-
crease in depth as earlier study has showed active par-
ticipation of nitrifying bacteria in bio-mineralization [25].
The concentration of phosphate-phosphorous was found
to be 0.675 and 0.344 μg·g–1 dry wt. of sediment in sur-
face and at a depth of 60 cm respectively, during post-
mon-soon. The concentration of Phosphate-Phospho-
rous, Sulfate-Sulfur, organic Carbon and organic matter
were found to show a decreasing trend with increase in
depth. Dehydrogenase activity plays an essential role in
the initial stages of oxidation of soil organic matter [11].
Dehydrogenase activity was found to diminish from
surface with increase in depth (Figure 4) and the regres-
sion equation is Dehydrogenase = 373.563 – 1.57281 Depth
(cm); [F = 2.80548, P = 0.110, n = 21].
During pre-monsoon, the depth profile study with re-
spect to enzyme activity evoked an informative scenario.
Dehydrogenase and β-D glucosidase activity were found
to show a decreasing trend with increase in depth (Fig-
ure 5(a)). Dehydrogenase activity was found to show de-
creasing trend with increasing depth. Same profile was
found for β-D glucosidase activity (Figure 5(b)). Niemi
Figure 4. Relationship between enzyme (dehydrogenase) ac-
tivity and depth (cm).

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72
6969
R.M. et al. in 2005 [26] showed similar trend of enzyme
activity with increase in depth. During post monsoon
urease activity did not show significant gradation with
increasing depth from surface to 60 cm of depth. Both
dehydrogenase and β-D glucosidase activity were found
Pre mo nsoon
225
230
235
240
245
250
255
260
0 102030405060
Dep th (cm)
G lucosid as e Activit
y
300
310
320
330
340
350
360
370
380
390
D ehydr ogenase Activit
y
glucosidase
activity
dehydrogenase
activity
(a)
Monsoon
210
220
230
240
250
260
270
280
290
300
0 102030405060
De
p
th (cm)
G lu cos id as e Act ivit
y
300
320
340
360
380
400
420
440
460
480
500
Dehydrogenase Activit
y
glucosidase
activity
dehydrogenase
activity
(b)
Po st mon soon
200
205
210
215
220
225
230
235
240
245
250
0 102030405060
Dep th (cm)
G lucosid a se Act ivit
y
150
170
190
210
230
250
270
Deh ydrogen as e Act ivit
y
glucosidase
activity
dehydrogenas e
activity
(c)
Figure 5. Depth profile of soil enzyme activity during pre-
monsoon, (a) monsoon and (b) post monsoon(c).
to show decreasing pattern with increase in depth up to
20 cm of depth (Figure 5(c)).
Culture methods used in this study to assess the sea-
sonal influences on the microbial community of the Sun-
darban mangrove forest ecosystem detected six different
types of microbes (Cellulose Decomposing Bacteria,
Sulfate Reducing Bacteria, Phosphate Solubilizing Bac-
teria, Nitrogen Fixing Bacteria, Fungi, and Nitrifying
Bacteria). Apart from these six different types (Proteo-
bacteria, Flexibacteria, Actinobacteria, Chloflexi, Planto-
mycetes, and Gammatimonadates) were detected. Ghosh
et al. 2010 [27] detected two more types (Acidobacteria,
Firmicutes), using culture independent method in the
Sundarban mangrove sediment. Plate culture method is
able to count only a fraction of total microbial load acce-
ssible in soil; however they provide a valid and reliable
measure of heterotrophic microbial biomass and acti-
vities present in the soil and generally the variations in
number of colony forming units correspond to the varia-
tions in the total microbial community [28-30]. From the
season wise study of relative abundance of microbial
population of different category, an expounding outcome
was revealed. During pre-monsoon the most dominating
group was cellulose decomposing bacteria (40%). Least
dominance was showed by free living nitrogen fixing
bacteria (5%). Phosphate solubilizing bacteria (8%), Sul-
fate reducing bacteria (9%) and nitrifying bacteria (15%),
however, showed considerable relative abundance (Fig-
ure 6(a)). During monsoon, the most dominating group
was cellulose decomposing bacteria (49%) prior to fungi
(21%). Least supremacy was exhibited by free living
nitrogen fixing bacteria (4%). Phosphate solubilizing ba-
cteria (10%), Sulfate reducing bacteria (4%) and nitrify-
ing bacteria (12%) showed considerable relative abun-
dance (Figure 6(b)).
Climatic condition and occurrence of plenty of orga-
nic carbon in the soil throughout the year might be re-
sponsible for maximum abundance of cellulose decom-
posing bacteria [31]. The post monsoon season also fol-
lowed the same pattern with the most dominating group
of microbe being cellulose decomposing bacteria (47%)
prior to fungi (21%). Free living Nitrogen fixing bacteria
was of least dominance (5%).
Phosphate solubilizing bacteria (10%), Sulfate redu-
cing bacteria (5%) and nitrifying bacteria (12%) follow-
ing the pattern reflected earlier showed quite consider-
able relative abundance (Figure 6(c)).
Increase in population of sulfate reducing bacteria
with increase in depth might be due to increase in anox-
icity with increase in depth [32]. Twelve parameters viz.
Total C.F.U, pH, Eh (mV) , Temp (˚C), Salinity (psu),
3
NO

, 2 NO

, Organic C%, , , glucosidase
activity and dehydrogenase activity were included in the
PCA (principal component analysis).
3
4
PO2
4
SO

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72 70
Premonsoon
15%
8%
5%
40%
23%
9%
Nitrifying Bacteria
Phosphate Solubilizing
Ba ct eria
Free Living Nitrogen Fixing
Ba ct eria
Cellulose Decomposing
Ba ct eria
Fungi
Sulfate Reducing Bacteria
(a)
Monsoon
12%
10%
4%
49%
21%
4%
Nitrifying Bacteria
Phosphate Solubilizing
Bacteria
Free Living Nitrogen Fixing
Bacteria
Cellulose Decomposing
Bacteria
Fungi
Sulfate Reducing Bacteria
(b)
Post monsoon
12%
10%
5%
47%
21%
5%
Nitrifying Bacteria
Phosphate Solubilizing
Ba c t er ia
Free Living Nitrogen Fixing
Ba c t er ia
Cellulose Decomposing
Ba c t er ia
Fungi
Sulfate Reducing Bacteria
(c)
Figure 6. Relative abundance of different groups of culturable
microbes in the sediment during (a) pre-monsoon; (b) monsoon;
and (c) post-monsoon.
The principal component analysis (Table 2) showed
that only three factors were responsible for explaining
the variability of physico-chemical parameters and enzy-
me activities. All these three factors comprise about 87%
of the variability. In fact, factor 1 & 2 contributed to
about 72% of the variability including the components.
Temp., Eh, 3, 2, NO NO2
4
SO

, β-D glucosidase, dehy-
drogenase show negative correlation with total bacterial
populations and, , Org.C %. Factor 3 largely arises
due to salinity and glucosidal activity which are posi-
3
4
PO
Tab le 2 . Principal Component Analysis (Eigenanalysis of the
Correlation Matrix): Total C.F.U, pH, Temp (˚C), Eh (mV),
Salinity (psu), 3
NO

(µg·g–1 dry wt of soil), 2 (µg·g–1 dry
wt of soil), Organic C%,
NO
3
4
PO

(µg·g–1 dry wt of soil), 2
4
SO

(mg·g–1 dry wt of soil ), β-D Glucosidase activity (µg PNP
produced hr–1·g–1 dry wt of soil) & dehydrogenase activity
[nmol INTF (g dry wt of soil )–1 2 h–1].
Eigen value5.04443.55811.7686 0.8810 0.38000.1591
Proportion 0.4200.2970.147 0.073 0.0320.013
Cumulative0.4200.717 0.864 0.938 0.969 0.983
Variable PC1 PC2PC3 PC4 PC5PC6
Total CFU 0.265–0.367–0.268 0.172 0.0200.006
pH 0.314–0.049–0.045 –0.571 0.724–0.113
Eh (mV) 0.061–0.508–0.032 0.076 0.067–0.258
Temp –0.407–0.060–0.261 –0.106 0.0940.162
Salinity –0.023–0.1990.682 0.008 0.058–0.298
3
NO

–0.015–0.3430.274 –0.629 –0.469 0.277
2
NO

–0.390–0.1750.072 0.025 0.315 0.626
Org.C 0.401–0.140–0.204 0.124 –0.0360.235
3
4
PO

0.423–0.042–0.148 –0.116 –0.1870.315
2
4
SO

0.142–0.3780.312 0.443 0.1890.257
β-D Glucosidase–0.171–0.412–0.323 –0.069 –0.213–0.323
Dehydrogenase–0.347–0.282–0.213 –0.033 0.146–0.109
tively correlated with total bacterial populations.
4. CONCLUSIONS
From the present study an efficient conclusion can be
drawn as a result of our research on depth profile ex-
ploration of enzyme activity with microbial community
from the oxygen-starved soil of Sundarban Mangrove
forest, India. Organic carbon from the leaves, wood from
forest and other organic dead or waste products from
other living organisms are easily degraded by cellulose
decomposing bacteria in the mangrove sediment because
they are the most dominating group of microbes prior to
fungi. Other groups of microbes have also exhibited sig-
nificant population count which helps in bio-mineralize-
tion. Microbial activity throughout the year with respect
to dehydrogenase activity and β-D glucosidase activity
were found to be efficient enough to carry out active
bio-mineralization through biogeochemical cycles. Verti-
cal decrease in nutrient concentration along with soil
enzyme activity suggested that increasing depth caused
unfavorable condition for microorganisms to carry out
bio-mineralization processes.
5. ACKNOWLEDGEMENTS
The financial assistance from DOEn, Govt. of West Bengal and U. G.
C., New Delhi are gratefully acknowledged. The authors are also
grateful to the Forest Department, Govt. of West Bengal for assisting

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72
7171
the research team in collecting data and providing all infrastructural
facilities to reach the remote island.
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