Depth profile exploration of enzyme activity and culturable microbial community from the oxygen-starved soil of Sundarban mangrove forest, India

doi:10.4236/oje.2011.13009

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Vol.1, No.3, 65-72 (2011)

http://dx.doi.org/10.4236/oje.2011.13009

Open Journal of Ecology

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: [email protected]; [email protected]

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



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

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



NO 

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

OPEN ACCESS

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72

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

300

310

320

330

340

350

360

370

380

390

D ehydr ogenase Activit

glucosidase

activity

dehydrogenase

activity

(a)

Monsoon

210

220

230

240

250

260

270

280

290

300

0 102030405060

th (cm)

G lu cos id as e Act ivit

300

320

340

360

380

400

420

440

460

480

500

Dehydrogenase Activit

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

150

170

190

210

230

250

270

Deh ydrogen as e Act ivit

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),



, 2



, Organic C%, , , glucosidase

activity and dehydrogenase activity were included in the

PCA (principal component analysis).

PO2

SO

S. Das et al. / Open Journal of Ecology 1 (2011) 65-72

Premonsoon

15%

40%

23%

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%

49%

21%

Nitrifying Bacteria

Phosphate Solubilizing

Bacteria

Free Living Nitrogen Fixing

Bacteria

Cellulose Decomposing

Bacteria

Fungi

Sulfate Reducing Bacteria

(b)

Post monsoon

12%

10%

47%

21%

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



, 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-

PO

Tab le 2 . Principal Component Analysis (Eigenanalysis of the

Correlation Matrix): Total C.F.U, pH, Temp (˚C), Eh (mV),

Salinity (psu), 3



(µg·g–1 dry wt of soil), 2

(µg·g–1 dry

wt of soil), Organic C%,

NO



(µg·g–1 dry wt of soil), 2



(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



–0.015–0.3430.274 –0.629 –0.469 0.277



–0.390–0.1750.072 0.025 0.315 0.626

Org.C 0.401–0.140–0.204 0.124 –0.0360.235



0.423–0.042–0.148 –0.116 –0.1870.315



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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