IOSR Journal Of Environmental Science, Toxicology And Food Technology (IOSR-JESTFT)
e-ISSN: 2319-2402,p- ISSN: 2319-2399.
Volume 3, Issue 5 (Mar. - Apr. 2013), PP 24-31
www.Iosrjournals.Org
www.iosrjournals.org 24 | Page
Spatial variation of chlorophyll integrity in a mangrove plant
(Excoecaria agallocha) of Indian Sundarban, with special
reference to leaf element and water salinity
Subhajit Bhar
1
, D. Chakraborty
1
, S. S. Ram
2
, D.Das
1
, A. Chakraborty
2
, M.
Sudarshan
2
and S.C. Santra
1
1
Department of Environmental Science, University of Kalyani, India
2
UGC DAE CSR, Kolkata Centre, India
Abstract: Present study describes a site specific variation of leaf elemental concentration and Photosynthetic
pigment concentration in a mangrove plant Excoecaria agallocha in Sundarban, India. Three locations (S1, S2
and S3) were selected according to water salinity gradient in north to southward direction. Range of water
salinity is from 19 ppt to 34 ppt. All elements (Fe, Cu, and Mn) are found to be higher in S1 followed by S2 and
S3 except Zn. They follow the trend like Fe>Mn>Zn>Cu. Interestingly photosynthetic pigment concentration
(total chlorophyll, chlorophyll-a, chlorophyll-b) showed negative correlation with salinity i.e. increase in water
salinity causes decrease in pigment concentration. Results from our study depicts that Sundarban is facing
problems for increasing pollution load and water salinity.
Keywords: Excoecaria agallocha, Leaf element, Mangrove, Salinity gradient, The Sundarban.
I. Introduction
The Sundarban, a UNESCO World Heritage Site (for rich flora and fauna) covering parts
of Bangladesh and Indian state of West Bengal, is the largest single block of tidal halophytic mangrove forest
in the world (Gopal and Chauhan, 2006). Mangrove forests are among the most productive ecosystem and are
natural renewable resource that grows in saline coastal sediment habitats in the tropics and subtropics
(Chapman, 1977; Knox and Miyabera, 1984). Being host for a number of threatened and endangered species,
with different animals, mammals, amphibians, reptiles and bird species, they play crucial role for protecting
environment from the fury of cyclones and storms and also protect coral reefs, sea-grass bed, shipping lines
from siltation. Mangrove vegetation can acts also as a purifier of water by absorbing impurities and harmful
heavy metal and also absorbs air pollutants. The mangrove plants show different responses to elemental uptake
(Kabata-Pendias and Pendias, 1997).
Flow of anthropogenic activity induced pollutants from nearest metro city Kolkata, population pressure
in this region, global warming etc., are now causing threats to this natural resource. One important impact of
these disturbances is increase in water salinity (Mitra et al., 2004). Decreasing fresh water amount in the
tributaries of river Hooghly, siltation in the river channel directly trigger salinity increase while sea level rise
due to Global Warming and increasing evaporation rate, indirectly help to increase the water salinity. Salinity
also has some adverse effect on photosynthetic efficiency in the plant (Critchley, 1985; Sharkey et al., 1985).
According to Naskar et al., (1997) high salinity and human interference have compelled several species to
migrate towards the eastern Sundarban or are gradually dying. In coming future Sundarban will face destruction
of major forest resources along with forest environment due to anticipated sea level rise and increasing salinity
caused by global warming. It is reported that salinity adversely affects metabolic activities and seedling growth
of plants (Hampson and Simpson, 1990; Zidan and Al-Zahran, 1994).
Besides increasing water salinity, heavy metal pollution causes another threat to mangrove ecosystem
(Agoramoorthy et al., 2008) as heavy metals are retained in mangrove forests through plant uptake (Machado et
al., 2002). Earlier reports of MacFarlane and Burchett (2000) showed that Avicennia marina exposed to zinc,
copper, and lead, accumulate high concentration of metals in their cell wall of the roots. The same group has
enlightened that Heavy metals are amongst the most serious pollutants within the natural environment due to
their toxicity, persistence and bioaccumulation problems (MacFarlane and Burchett, 2000).
The present research was designed to evaluate a site specific variation of chlorophyll integrity and leaf
element of Excoecaria agallocha and changes of chlorophyll on the basis of leaf element and salinity gradient.
These in turn will the fact, how Sundarban is in risk.
Spatial variation of chlorophyll integrity in a mangrove plant (Excoecaria agallocha) of Indian
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II. Materials And Methods
2.1. STUDY AREA
The study areas (Fig.1) are located in an around Sundarban. Study Site I (S1) situated near Matla river
(22°18'40.53''N 88°40ʹ31.27ʺE) having most population pressure than other two sites. Boat activities were
carried out by local fisherman and also ferry service is there. Site II (S2) (22°1'22.51''N 88°41ʹ11.71ʺE) situated
near river Hariavanga and human population moderate, fishing activity is there. Site III (S3) (21°34'25"N
88°17'47"E) is situated near the Bay of Bengal; fishing and tourist activity are there. The sites have diverse
human interferences with a variable degree of exposure to heavy metal and trace organic contamination.
Information’s of three study sites are in Table1.
2.2. STUDY SPECIES
Excoecaria agallocha is mangrove species belonging to family Euphorbiaceae (Ghani, 2003). It is
found near the bank of tidal rivers in brackish water and almost all the places in the above study area of
Sundarban. Leaves and saps are used in epilepsy, conjunctivitis dermatitis, haematuria, and leprosy. Sap is used
in toothache. This plant provides match wood. Plant also has anti-cancerous, antibacterial and antiviral
properties (Peter and Sivasothi. 1999).
2.3. SAMPLING TECHNIQUES
The mangrove plant leafs were collected from three sites. For each sampling station, three replicate
were taken (n=3). Water sample were also collected from the same sampling sites. The samples were
immediately packed with zip-lock packet and labeled. All samples were kept in cooler box with ice at 4
o
C
(Prica, 2007) during transporting back to the laboratory at the trace element lab, UGC DAE CSR, Kolkata
Centre, India.
2.4. ELEMENTAL ANALYSIS USING EDXRF
2.4.1. SAMPLE PREPARATION
Leaf samples were lyophilized for 36h and dried leaf samples were homogenized using a mortar and
pestle and 150 mg sample made into pellets (1 mm thick and 13 mm diameter) using a tabletop pelletizer
(Pressure: 100–110 kg/cm
2
for 5 min). Three pellets were made for each sampling site.
2.4.2. EDXRF MEASUREMENT
EDXRF (Energy Dispersive X-Ray Fluorescence) spectroscopy is a multi-elemental, nondestructive
technology use in elemental analysis. The elemental analysis of lichen samples was carried out using a
Xenemetrix, Ex-3600 Energy dispersive X-ray fluorescence (EDXRF) spectrophotometer with an oil-cooled Rh
anode X-ray tube (maximum voltage 50 kV, current 1 mA). The measurements were carried out in vacuum
environment using different filters (between the source and sample) for optimum detection of elements. A Ti
filter (0.05-mm-thick) was used in front of the source for Mn, Fe, Cu and Zn with an applied voltage of 20 kV
and a current 400 mA. All measurements were carried out for 1200 s. The X-rays were detected using a liquid-
nitrogen-cooled 12.5 mm2 Si (Li) semiconductor detector (resolution 150 eV at 5.9 KeV). The X-ray
fluorescence spectra were quantitatively analyzed by the software nEXT integrated with the system. A standard
reference material (SRM) from National Institute of Standards and Technology (NIST) Apple leaf (SRM 1515)
was used for quantification of the elements and checking the reliability of the data obtained by the system.
2.4.3. PIGMENT ANALYSIS
Pigment analysis was done following methods of Barnes et al. (1992). About 50mg mangrove leaves
(E.agallocha) of all three sites were extracted in dark for 1 hr at 65ºC with 5 ml of di-methyl sulfoxide (DMSO)
in the presence of polyvinyl-pyrrolidone (PVP) (2.5mg/ml
-1
) to minimize chlorophyll degradation. Extracts were
then allowed to cool to ambient temperature, diluted 1:1with fresh DMSO, and the absorbance were taken at 740
nm, a reflection of turbidity, was checked with a PerkinElmer lambda-25 UV-VIS-spectrophotometer to be
certain that it was always less than 0.01. To assess chlorophylls, absorbance of the extracts was then read at 665,
649, 435 and 415 nm. Chlorophyll a, Chlorophyll b and total chlorophyll were calculated using equations
derived from specific absorption coefficients for pure chlorophyll a and chlorophyll b in DMSO (Barnes et al.
1992).Three replicates were used for each sites.
Spatial variation of chlorophyll integrity in a mangrove plant (Excoecaria agallocha) of Indian
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III. Results And Discussion:
Our results depict a site specific variation of elemental profile as well as photosynthetic pigment
analysis (Chlorophyll-a, Chlorophyll-b, Total Chlorophyll) in E. agallocha .Photosynthetic pigment changes
with salinity gradient i.e increase in water salinity causes decrease in chlorophyll content in E. agallocha.
Figure2. represents site specific variation of elements (Mn, Cu, Zn, Fe) in leaf of E. agallocha . All
elements (except Zn) are found to be higher in low saline region (S1) followed by S2 (moderately saline ) and
S3 ( high saline). Fe content is higher in all sites than other elements. Interestingly, higher level of variation of
Mn and Fe are noticed between these three sites. Mn is found to be 35%-31% higher in S2 than S3 and S1,
while we observed Fe is 70 %( S2) and 57% (S3) higher concentration than S1. Pollution load and
anthropogenic activities may explain the higher elemental concentration in S1 followed by S2 and S3, while
heavy metal pollution like Zn is found to be higher in S3. Defew et al., (2005) also found same trend
(Fe>Mn>Zn>Cu) of elemental concentration in mangrove sediments as well as in mangrove plants. Our results
are in tune with Pahalawattaarachchi et al., (2009); they found high Fe content than other metals in Rhizophora
mucronata.
Similarly, low saline region (S1) contains higher amount of total chlorophyll which follows site S2
(moderately saline) and S3 (high saline) (Fig.3). S2 contains 10.15% less total chlorophyll, 9.78% less
chlorophyll a, 11.17% less chlorophyll b with respect to low saline zone S1. While for S3 (high saline region), it
is 19% less total chlorophyll, 10.15 % less chlorophyll b and 19.11% chlorophyll b than low saline zone S1
(Fig-2). Pearson correlation (Table-2) represents a very strong correlation between pigment concentration (Chl-
a, Chl-b and total chlorophyll) and Mn, Zn, salinity (p<0.001) and Fe (p<0.05). While against salinity it shows a
strong negative correlation. Some elements also show positive correlation between them like Mn and Fe
(p<0.001), Cu and Mn. According to Dhanapackiam and Muhammed (2010), high salinity (40 and 50 mM)
induced a significant decreasing effect in the concentration of pigment (chlorophyll a and chlorophyll b) and
also in the total chlorophyll concentration with respect to control. Our results also revealed the same trend,
which showed that in high saline region (S3), pigment (chlorophyll a and chlorophyll b) concentrations are also
low and in low saline region(S1), pigment (chlorophyll a and chlorophyll b) concentration is high. Earlier
reports of Biber (2011), also supposed that change in salinity affects photosynthetic pigment of Rhizophora
mangle L.
IV. Conclusion
This preliminary study depicts a site specific variation of leaf elemental concentrations as well as
photosynthetic pigment analysis of Excoecaria agallocha. Water salinity of these sites are significantly different
from one another, that is reflected through variation in chlorophyll concentration (Increase in water salinity
causes decrease in chlorophyll content), which signifies salinity causes destruction of chlorophyll (i,e
annihilation in photosynthetic activity). Other species also have same photochemical responses on salinity
(Naidoo et al., 2002). Whether salinity has any adverse relation with mangrove elemental uptake or not, needs
more study, so that these plants can be used for bioremediation purposes. E .agallocha of S1 contains higher
elemental concentration which signifies higher pollution load than other sites, which may cause further threat to
Sundarban. So, proper assessment and mitigation as well as safety measures are urgently needed. The
pigments, being the key factors for controlling the growth and survival of the mangroves plants require an
optimum salinity range between 4 to 15 psu (Downton 1982; Burchett et al., 1984) for proper functioning. The
present study is extremely important from the point of view of rising salinity in this study area of Sundarban
where fresh water supply were depleted due to heavy siltation (Chaudhuri and Choudhury, 1994) and sea level
rising (Hazra et al., 2002).
Acknowledgements
Authors are very much thankful to UGC-DAE Consortium for Scientific Research, Kolkata Centre for
providing EDXRF facility and fund for carrying out the work. The authors also thankfully acknowledge Govt.
College of Engineering and Leather Technology, Kolkata for providing UV-VIS Spectrophotometer.
Spatial variation of chlorophyll integrity in a mangrove plant (Excoecaria agallocha) of Indian
www.iosrjournals.org 27 | Page
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Figure1. Study area with three sampling sites [S1, S2 and S3]
Mn Fe Cu Zn
10
100
1000
Concentration(mg/kg)
Elements
SiteI
SiteII
SiteIII
Figure2. Concentration of Mn, Fe, Cu and Zn in Excoecaria agallocha leaf in three specific sites