251

KEYWORDS

ISSN: 0974 - 0376

NSave Nature to Survive

: Special issue, Vol. III:

www.theecoscan.inAN INTERNATIONAL QUARTERLY JOURNAL OF ENVIRONMENTAL SCIENCES

Prof. P. C. Mishra Felicitation Volume

Paper presented in

National Seminar on Ecology, Environment &Development

25 - 27 January, 2013

organised by

Deptt. of Environmental Sciences,

Sambalpur University, Sambalpur

Guest Editors: S. K. Sahu, S. K. Pattanayak and M. R. Mahananda

Susanta Kumar Chakraborty

Mangrove

Biodiversity

Biocomplexity

Environmental Variables

Ecohydrology

Ecorestoration

251 - 265; 2013

INTERACTIONS OF ENVIRONMENTAL VARIABLES DETERMINING

THE BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM OF

WEST BENGAL, INDIA

252

SUSANTA KUMAR CHAKRABORTY

Department of Zoology, Vidyasagar University,

Midnapore - 721 102, West Bengal, INDIA

E-mail: susantachakraborty@yahoo.com

INTRODUCTION

Coastal Zone represents the junction between the land and sea. The extent of

coastal ecosystem is limited to that part of land which is influenced by adjoining

sea and that part of the sea / estuary which is subjected to the impact of adjoining

land. Coastal environment plays a vital role in nation’s economy by virtue of their

resources, potential for ecotourism and fisheries, controlling ability of

meteorological phenomenon, ensuring navigation and water transport system.

India has a coastline of 7517km of which the mainland accounts for 5422km.

Lakshadeep coast extends 132km and Andaman and Nicobar Islands have a

coastline of 1962km. Nearly 250 million people live within a distance of 50km

from the coast (Qasim et al., 1988). Coastal habitats across the world have been

under multi-dimensional threats during last few decades because of high

population and development pressures. Mangroves have been particularly

vulnerable to exploitation because they contain valuable bioresources and

provide significant ecological services.

Mangrove ecosystem, a unique, fragile, highly productive ecosystem in the sea-

land interphase, is the conglomerations of plants, animals and microorganisms

acclimatized in the fluctuating environment of tropical intertidal zone.

Mangrove forests cover wide tropical and subtropical intertidal areas of coastal

environment, and they are very important for their role in maintaining biodiversity,

for sustainable livelihood (e.g., wood and food resources) and for coastal

protection (Robertson and Alongi, 1992; Wolanski, 2006a).

The coastal area of West Bengal extends over 0.82 million hectors and 220km of

NSave Nature to Survive QUARTERLY

Among the 9 maritime states of India with a

coastline of 7500km, West Bengal enjoys a

unique geographical location possessing the

Hoogly-Matla estuarine complex of

Sundarbans shared with neighbouring country

– Bangladesh. The biodiversity of the coastal

area of West Bengal extending over 0.82

million hectare and along 220km of coastal

line shared by two coastal districts viz. South

24 Parganas and Midnapore (East), includes a

good number of mangroves and their associate

plant species, different species of algae, fungi,

lichen, fishes, amphibians, reptiles, birds,

mammals, besides numerous species of

phytoplankton, zooplankton, ichthyoplankton,

benthos, soil inhabiting arthropods and both

soil and vegetation dependent insects. The

settlement of mangrove species and their

simultaneous growth trigger the accretion

process paving the way of deltaic formation in

the coastal West Bengal and simultaneous

settlement of associated floral and faunal

components in tune with interplay of different

eco-bio-physico-chemical factors along

environmental gradients. An ecohydrological

approach towards understanding of mangrove

ecosystem functioning appears to be a

prerequisite for sustainable biodiversity

management and ecosystem restoration. The

present paper highlights the uniqueness of

coastal mangrove ecosystem functioning in

respect of interactions of different

environmental variables with biodiversity in

West Bengal coast. This is also an attempt to

represent how the interplay between

specialized adaptations and extreme trail

plasticity that characterize the mangrove and

intertidal environment giving rise to the bio-

complexity that distinguishes mangrove

ecosystem from others. In such context,

assessment of environmental threats,

biodiversity conservation strategies and

ecorestoration possibilities have been dealt

with in this studied environment.

ABSTRACT

Figure 1: Maps of Sundarban and Midnapore coastal belt

253

coastal line. Muddy coast accounts for 180km, of which 90%

are treated as marshy zone having halophytic vegetation and

their associated flora and fauna; only around 40km is

considered as sandy belts. It includes two coastal districts –

The South 24 Parganas, supported by Sundarban Mangrove

Ecosystem and Midnapore Coast having sand flats and

degraded mangrove patch. Indian part of Sundarbans occupies

mangrove area (4262km2) slightly more than that (4109km2)

of highly reclaimed counterpart in Bangladesh (Chaakraborty,

2011). The coastal belt of Midnapore district represents 27%

of West Bengal of coastal tract (60km) extending along the

west bank of Hooghly estuary from New Digha and then

curving around Junput, Dadanpatrabarh, Khejuri and Haldia

on the east to the further north east upto Tamluk or even on

the bank of Rupnarayan (Fig. 1). In West Bengal, three seasons

are very much pronounced (premonsoon, monsoon and

postmonsoon), each with four months duration and are mainly

governed by rainfall and temperature (Chakraborty et al.,

2010).

Seasonal dynamics of mangrove ecosystem

Seasonal change: Mangrove ecosystems are influenced by

seasonal changes in climate, especially seasonal variations in

rainfall as well as sea level. Seasonal changes in sea level

result from a number of factors: (1) variations in wind direction

and speed (often monsoonal) upon the coastal ocean (Ridd et

al., 1988), (2) changes in water temperature that bring about

an expansion in water volume, (3) changes in atmospheric

pressure, and (4) changes in river runoff due to rainfall (Kjerfve,

1990). Such changes in meteorological parameters especially

in view of global climatic change is being thought to impart a

profound impact on mangrove-estuarine biodiversity of West

Bengal (Hazra et al., 2002; Mitra et al., 2004).

Hydrodynamics in mangrove area: Mangrove ecosystems

experience daily inundation and exposure twice a day causing

an interruption of continuous flow throughout the cycle of a

tidal period. Densely vegetated mangrove trees, prop roots,

leaves, pneumatophores and other epiphytic forms, faunal

bioturbatory structures govern the horizontal and vertical

hydrodynamics. Further, since the nature of water flow within

mangrove areas depends on the timescale, it is necessary to

develop different flow models due to tidal flows, groundwater,

and other atmospheric processes, individually. Mangrove

prop roots and pneumatophores are densely intertwined

above the bottom substrate. Because of interaction between

mangrove roots and tidal flows, water turbulence or eddies

occurs primarily in the region of the swamp near the boundary

of the open coast. These turbulent interactions act to mix and

diffuse water and materials, and contribute to form and

maintain the distribution of material within the swamp

(Wolanski, 1995; Furukawa and Wolanski, 1996; Furukawa

et al., 1997). In particular, Wolanski et al. (1998) proposed

that the sedimentation is enhanced by the turbulence around

the vegetation and results in the formation of new land.

Different parts of West Bengal coastal estuarine-deltaic

mangrove settings experience different grades of erosion and

accretion process because of increased velocity of flood inflow

balanced by frictional dissipation of hyper-synchronous

Hooghly estuary (Paul, 2002). Besides, the hydrodynamics

and macrotidal setting, funnel shaped plan of different deltas,

upstream movement of large volumes of riverine sediments

coupled with depositional characteristics have cumulatively

contributed to the depositional landform development (Paul,

2002; Chakraborty et al., 2012)

Material dispersion: The fate of water-born materials in the

mangrove areas is controlled by dispersion processes, which

depend on the unique topography and spatial characteristics

of mangrove vegetation. The fate of cohesive, fine suspended

sediments influences the inflow of sediment-laden waters into

the mangrove forest and triggered the settling of a fraction of

this sediment in the swamp, leading to modify the bathymetry

and expansion of the forest area (Mazda et al., 2009).

Holistic system: The mangrove ecosystem is maintained via

strong feedbacks between many factors as mentioned above.

Each of these factors operates at different timescales. The total

ecosystem is established by nonlinear interactions between

these factors with contrasting timescales. Further, the mangrove

environment should be understood as the ecohydrology,

composed of the river basin, the river, the estuary, and coastal

waters, through which not only water and dissolved materials

but also biotic actions are strongly connected (Wolanski,

2006a).

The four factors, namely, (1) biota (mangrove trees, benthic

fauna such as mad crabs and algae) (2) sediment topography,

(3) water flow such as tidal flow and waves and (4) the

atmospheric processes (wind, rainfall etc), play important roles

individually and in conjunction with others, forming andmaintaining the mangrove ecosystem. Every factor interactsone of other factors (Mazda et al. 2007). The amount of waterthat inundates mangrove swamps depends on vegetationdensity because the vegetation resists water inundation (Mazdaet al., 1999). Further, the tide in mangrove swamps ismeasurably modified from that offshore due to resistance ofmangrove vegetation (Mazda and Kamiyama, 2007). Watson(1928) proposed a simplified classification model to explainthat the growth of mangrove trees and species zonation patternsdepend strongly on the hydrological conditions such as thetides and the elevation of the substrate, as these factors control

the flooding frequency, the duration of inundation and the

depth of inundation (Bunt et al., 1985).

In Sundarbans, the mangrove bioassemblage has been found

to be divided into several ecotonal zones with dominant

characteristic plant species adapted to a set of physico-

chemical variables. Chaudhuri and Chowdhury (1994) divided

the forest into four major forms, based on tidal levels, as, i)

High tide ii) Above general tidal level iii) Frequently inundated

by salt water and iv) Below tide level.

Uniqueness of mangrove ecosystems

Global distribution of Mangroves and associated biodiversity:The term mangroves collectively refers to woody halophyticangiospermic trees inhabiting in the intertidal zone of coastal-estuarine regions in the tropics and subtropics, especiallybetween 25ºN and 25ºS where the winter water temperatureremains not less than 20ºC. Mangrove has a worldwidecircumtropical distribution, the highest concentration beinglocated in the IndoPacific region. The mangroves dominatealmost 1/4th of world’s tropical coastline. The total mangrove

area which spans 30 countries including various island nationsis about 1, 00, 000km2 (Annon, 2003). Mangrove forests have

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

254

SUSANTA KUMAR CHAKRABORTY

been estimated to have occupied 75% of the tropical coastsworldwide (Chapman, 1976).

Root causes of loss of mangrove: Anthropogenic pressureshave been found to have reduced the global range of theseforests to less than 50% of the original total cover (Saenger etal., 1983; Spalding et al., 1997). These losses have largelybeen attributed to anthropogenic pressures such as over-harvesting for timber and fuel-wood production (Semesi, 1998),reclamation for aquaculture and saltpond construction(Chakraborty, 1998, Primavera, 1995), mining, pollution anddamming of rivers that alter water salinity levels (Qasim, 1988;Lewis, 1990, Wolanski, 1992) and oil spills (Sengupta andQasim, 1988; Ellison and Farnsworth, 1996; Burns et al.,1994). A major threat to mangrove wetlands is their conversionto areas of aquaculture. After the development of intensiveshrimp farming techniques in Taiwan in the 1970’s, there wasa sudden rush into modern shrimp farming in Southeast Asia(Chakraborty, 1998). In the Indo-Western Pacific region alone,1.2 million hectares of mangroves had been converted toaquaculture ponds by 1991 (Primavera, 1995).

Shrimp farming represents a relatively new form of coastalland use that is becoming a threat in the region. The

construction of shrimp ponds would result in the exposure of

strongly reducing acid-sulphate, soils and a buildup of salinity

levels, such that the subsequent replanting of mangroves in

eventually abandoned ponds is difficult or even impossible

(Stevenson et al., 1999).

More recently mangroves have been managed for integrated

fish culture (Primavera, 1995) and for eco-tourism (Bacon 1987).

Planting mangroves has also been applied for erosion control

in Florida (Teas, 1977) and Nayachar Island, West Bengal,

India (Chakraborty et al., 2012). Beginning with the realization

of ecological roles of mangroves (Odum and Heald, 1975)

and after the enactment of several laws protecting them from

destruction, many small plantings for mitigating environmental

damage have occurred for example in Hawaii, Burma, Fiji(Hamilton and Snedaker, 1984) andJharkhali, Sundarbans,West Bengal, India (Chakraborty et al., 2010).

Role of mangroves: Importance and values: For centuries,mangrove ecosystems have provided goods and services bothon the community, as well as national and global levels(Hamilton and Snedaker, 1984; Stafford-Deitsch, 1996;Dahdouh-Guebas et al., 2000; Kairo and Kivyatu, 2000). Manyof these services are still offered and include collection ofbuilding materials and fuel-wood, gathering of shells toproduce lime and wild honey collection. Mangroves also filterland run-off (Thom, 1967) and control coastal erosion (Davis,1940).

The importance of mangrove ecosystem for its potential forbiological production has received wide acceptance all overthe globe, mainly due to two reasons-

1. Large quantities of energy in the form of mangrove plantscontributed detritus are exported from the mangrove forest

to open water bodies (Odum and Heald, 1975) and positive

correlation exists in between the extent of mangrove and

total bioresource from adjacent water bodies (Macnae,

1974).

2. Profitable regional and international markets for high

quality biological products.

Besides, they are being used as important nursery grounds

and breeding sites for a wide range of faunal components like

birds, mammals, crustaceans, reptiles, finfishes and shellfish.

They act as buffers against coastal erosion and natural disasters

like cyclone, typhoon etc. and provide accumulation sites for

sediment, nutrients, and other elements, including

contaminants.

Adaptability of mangroves and associated fauna and their

response towards ecological changes: Mangrove, being a

unique assemblage living between land and sea display a

number of morphological and ecophysiological adaptations

including viviparous germination, aerial roots

(pneumatophores) and physiological mechanisms to cope with

salinity, inundation and exposure pressure to maintain water

and carbon balance.

Floral adaptations

Adaptations to low oxygen: Red mangroves especially

Rhizophora spp. inhabiting inundated areas, prop themselves

up above the water level with stilt roots and can then take in

air through pores in their bark (lenticels). Black mangroves

like Avicennia spp. living on higher tidal level develop many

pneumatophores having a height of about few meters which

are covered in lenticels. The roots also contain wide

aerenchyma to facilitate oxygen transport within the plant.

Common examples of this type of root are visible in several

species of mangroves like Avicennia spp., Sonneratia spp.,

Heritiera sp., Lumnitzera sp. etc. It is to be noted that Heritiera

fomes (Sundari) shows numerous woody peg like

pneumatophores or blind root suckers (Tomlinson, 1996).

Adaptations for support: Certain mangrove shrubs like

Acanthus sp and climbers like Derris spp., Ipomea sp., grow

on the edges of rivers, saline waterbodies, dunes, marshes

etc. where the anchorage is not very strong. In these cases,

short roots grow obliquely downwards from near the base of

the stem and act like stilts providing additional support as well

as anchorage to the stem (Tomlinson, 1996).

Adaptations to high salinity: Mangrove species have a wide

range of salinity tolerance; as such, mangroves survive and

grow in the frequently tidal inundated saline coastal zones

and estuarine mouths. The soil and water in these coastal and

estuarine zones may interact with mangrove species by three

different ways, viz. by osmotic inhibition of salt water

absorption, by specification effects on nutrition or by causing

toxicity

All mangroves exclude most of the salts in seawater. Thus,

mangroves are endowed with a unique system of ion influx-

efflux regulation by virtue of which they regulate their cellular

ionic contents and have classified mangroves into three

categories (Walter, 1961): salt excluding, salt excreting and

salt accumulating types.

In salt excluding species like Rhizophora mucronata, Bruguiera

gymnorhiza and Ceriops decandra, the root system possess

an ultra-filtration mechanism, which is just like an insurance

of this particular group to dominate in the mangrove

community. Joshi (1975) opined that this characteristic has

enabled these species to dominate other floral components.

The salt excreting species of mangrove community like

255

Avicennia alba, Avicennia marina, Avicennia officinalis,

Aegiceros corniculatum, Acanthus ilicifolius etc. regulate their

internal salt levels through foliar glands. However, salt

accumulating species like Sonneratia apetala, Lumnitzera

racemosa, Exoecaria agallocha, Sesuvium portulacastrum,

Sueda maritima etc has the ability to accumulate high

concentration of salts in their cells and tissues, which imparts

succulence. Avicennia spp. can grow best in higher saline

soils and regular tidal inundated areas than in less saline zone.

These species can accumulate sodium ion in its leaf-tissue 10

times higher than potassium ion. Heritiera fomes can also

grow best in less saline soils and are found to accumulate

more of potassium ion than sodium ion (Karmarkar, 1985;

Naskar et al., 2004).

Red mangroves exclude salt by having significantly

impermeable roots which are highly suberised, acting as an

ultra-filtration mechanism to exclude sodium salts from the

rest of the plant. Analysis of water inside mangrove plants has

shown that anywhere from 90% to 97% of salt has been

excluded at the roots. Any salt which does accumulate in the

shoot is concentrated in old leaves which are then shed, as

well as stored away safely in cell vacuoles. White (or grey)

mangroves can secrete salts directly; they have two salt glands

at each leaf base (hence their name-they are covered in white

salt crystals). The most distinctive trichome (appendages which

are epidermal in origin) that develops in certain mangrove

leaves is the structure for secreting certain ions like Na+ and

Cl-. These form a general class of secretory structures referred

to as ‘salt glands’ by Fahn (1979).

Adaptation for limiting water loss: Because of the limited

availability of freshwater in the salty soils of the intertidal zone,

mangrove plants have developed ways of limiting the loss of

water either through transpiration or evaporation that they

lose through their leaves. The orientation of their leaves vary

to avoid the harsh midday sun and so reduce evaporation

from the leaves, and their stomatal openings lie below the

surface of the leaves (shrunken stomata). Mangrove leaves are

almost leathery, coriaceous, thick, fleshy and more or less

translucent with obscure leaf veins, which mean that there,

are no vein sheaths surrounding the veins. Sometimes, the

cuticle is thick and smooth with small hairs, giving the plant a

glossy appearance (Mitra et al., 2004).

Adaptation for nutrient uptake: The mangroves face the

biggest problem in nutrient uptake; thriving in perpetually

waterlogged soil, having little free oxygen. The osmotic

potential of the leaf cells of mangroves is high which is essential

to absorb saline water having higher density with its high

negative water potential.

Thus anaerobic bacteria liberate nitrogen gas, soluble iron,

inorganic phosphates, sulfides, and methane, which make

the soil much less nutritious and contribute to a mangrove’s

pungent odor. Prop root systems allow mangroves to take up

gases directly from the atmosphere, and various other nutrients,

like iron, from the inhospitable soil (Tomlinson, 1996).

Adaptations for increasing survival of offspring: In this harsh

environment, mangroves have evolved a special mechanism

to help their offspring survive. Mangrove seeds are buoyant

and therefore suited to water dispersal. Alternately, viviparous

mode of germination has been developed to ensure the settling

of saplings in the soft soil of mangrove forest floor and thereby

avoid shifting of the propagules by tidal water (Tomlinson,

1996).

Faunal adaptations

Adaptations to wave action: To encounter wave action, soft-

body animals such as bivalves, periwinkles and rock oysters

have hard calcareous shells. Periwinkles and mud snails have

suctorial foot for attachment of rock surface by suction. Crabs

shells are generally flat and round in shape to reduce resistance

to wave action. Crabs also have strong legs for gripping.

Adaptations to salinity stress: Bivalves, rock oysters and

gastropods and mud snails close up their valves or operculum

to prevent the entry of excessively salty water.

Adaptations to desiccation or alternate wetting and drying:

Bivalves, periwinkles, mud snails and rock oysters enclose

themselves in shells and trap a small amount of water within

the shells. Some mobile infauna such as polychaetes,

sipunculans, nemerteans and crabs hide in mud cave to evade

desiccation.

Adaptations for gaseous exchange: Inter-tidal animals enclose

their respiratory organs in a protective cavity to prevent them

from desiccation. Molluscs such as bivalves and rock oysters

have gills in the mantle cavity kept moist and protected by the

shells. Gaseous exchange usually only occurs in the presence

of water trapped in the branchial chamber. In Gastropods

such as mud snails gills are reduced and mantle cavity has

been modified as a lung for aerial respiration.

Adaptations for feeding: Bivalves and rock oysters are filter

feeders. Mud snails possess a radula for browsing the algae

on rock surfaces or plant structures. Fishes like Mudskippers

forage on exposed mudflats when tide water recedes by

hopping about on their limb like fins. Most of these animals

feed during high tides and have their bodies submerged. Crabs

feed at low tides and as detritivores, they feed on any food

washed in by tides.

Response of Mangroves and Mangrove Ecosystems to

Environmental Variables

Mangrove habitats have relatively low levels of species richness

compared with other high biomass tropical habitats like rain

forests and coral reefs (Ricklefs and Latham, 1993). Despite

the relatively low biodiversity, mangrove plants have a broad

range of structural and functional attributes which promote

their survival and propagation in relatively harsh conditions

of the intertidal zone. In this sense, diversity of mangroveplants is not measured in terms of numbers of species, butalso in terms of the ability of each species to cope with thewide range of environmental conditions in utilizing theirindividual, specialized attributes (Duke et al., 1998). Theimportance of such influencing factors is observed wheremangrove species group in distinct forest communityassociations (Bridgewater, 1989), and where species often havedistinct distributional ranges at different geographic scales(Duke, 1992). The distributions of mangroves are constrainedby various physical, environmental and climatic factors.Essentially, all factors must act upon each plant in some way,

and at some, or all, of the various stages of its life, from

propagule development to dispersal, to establishment, to

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

256

seedling growth, to reproductive years and maturation, to

advanced age and death. Since mangrove plants are a pool of

individual genetic entities related overall only by their ability

to grow in the intertidal zone, they have understandably

developed different attributes and strategies to live in this

enviroment, including: physical form and structure;

physiological capabilities; productive capacity and growth;

and reproductive development with dispersal of propagules.

Each attribute is then influenced by a range of biotic and

environmental factors which combine to determine the

distributional patterns of each species in combination with

others at global, regional, estuarine and intertidal scales.

The distribution and diversity of mangroves therefore warrants

careful re-consideration in view of the apparently wider

interplay of influencing factors.

Responses to light & temperature: Rates of photosynthesis

drop in mangroves exposed to excessive sunlight, possibly

due to high doses of UV-B radiation. Increasing UV-B produces

biochemical changes like decrease in amino acid and

unsaturated fatty acid production (Kathiresan, et al., 2001).

Excess shading may also negatively affect mangrove plants. In

dense mangrove forests, shaded saplings have lower shoot

biomass than those exposed to the sun.

Response to gases: Mckee (1993) found that flooding and

anoxia reduced the total biomass of Avicennia germinans

seedlings by 20-40% relative to drained controls. High

methane load is associated with anoxia in mangrove

environmants. Mangrove species with pneumatophores may

be best equipped to deal with high methane loads.

Pneumatophore-bearing species release more methane

through their leaves than do those lacking pneumatophores.

Response to gases: CO2: CO

2 stimulates productivity and more

efficient use of water as a result of reduced stomatal

conductance. Elevated CO2 reduced stomatal conductance

and transpiration. However, the effects of increased CO2 may

vary with other physical and chemical conditions.

Response to coastal changes: The mangroves are healthy and

diverse where the land is flat. In shallow basins, poor flushing

and the resultant hypersalinity stunt the mangroves or replace

them with saltmarsh or barren soil devoid of vegetation.

Decreasing rainfall and increasing evaporation also markedly

change mangrove populations. Ellison and Stoddart (1991)

suggested that mangroves are stressed by sea level rises

between 9-12cm. 100y-1 and concluded that faster rates could

seriously threaten mangrove ecosystems. Distribution of

mangroves will be affected by rising sea levels.

Response to tidal gradients and zonation: Zonation can be a

structural feature of mangrove forests in some parts of the

world (Woodroffe, 1992). Contributing factors of zonationinclude plant succession, geomorphology, physiologicaladaptation, propagule size, seed predation and interspecificinteractions (Schwamborn and Saint-Paul, 1996). Interspecificdifferences in tolerance for physiological stress is a cause ofmangrove zonation. Mangrove species respond differently todifferent tidal regimes.

Response to soil conditions: Soil properties have a major

impact on mangrove nutrition and growth. Some of the most

important characteristics are texture, electrical conductivity,

pH and cation exchange capacity. Nutrient fluxes in these

environments are closely tied to plant assimilation and

microbial mineralization (Alongi, 1996). Nutrients availability

may limit growth and production in many mangals. Varying

nutrient concentrations can change competitive balances and

affect species distributions (Twilley and Chen, 1998). In Indian

Sundarbans, texture of soil has been found to show spatial

variations like sandy (18.1 to 50.5), silt (26.6-60.6) and clay

(25.2 to 39.9) (Naskar et al., 2004) and also variations among

different tidal levels like sand (1.3 to 87.8), silt (9.2 to 59.3)

and clay (1 to 47.8) (Chakraborty et al., 2010)

Response to salinity: Salinity, as controlled by climate,

hydrology, topography and tidal flooding, affects the

productivity and growth of mangrove forests (Sylla et al., 1996;

Twilley and Chen, 1998). It can also strongly influence

competitive interactions among species (Ukpong, 1995).

Mangrove vegetation is more luxuriant in lower salinities

(Kathiresan et al., 2001). Chronic high salinity is always

detrimental to the mangroves. True mangroves (e.g. Avicennia

spp. and Rhizophora spp.) tolerate higher salinity than do

non-mangroves, but tolerance also varies among the true

mangroves. The soil and water salinity exhibit three different

mode of interactions in the Sundarbans mangrove estuarine

complex viz by osmotic inhibition of salt water absorption, by

specific effect (Naskar et al., 2004).

Response to sedimentation: Massive land reclamation and

continuous deforestation during last couple of centuries have

resulted detachment of freshwater sources (creeks and

channels of Bidyadhari, Matla estuaries) leading to accelerated

deposition of silts in different deltaic networks of Sundarbans.

Besides, considerable and continuous erosion processes have

led to make the water bodies turbid and to promote unwanted

accretion (Chakraborty, 2011).

Response to metal pollution: The chemical and physical

environment of the mangal may efficiently trap trace metals in

non-bioavailable forms. Disturbances may cause the

mangrove soils to lose their metal-binding capacity, resulting

in mobilization of the metals. The mangal then shift from a

heavy metal sink to a heavy metal source (Lacerda, 1998).

Response to organic and oil pollution: It has been recorded

that mangroves posses high capacity to retain pollutants, which

may be attributed to their presence in anaerobic and reduced

conditions, periodically flooded by tides endowed with high

clay and organic matters. However, the impact of wastewater

to the mangrove ecosystem is a matter of great concern than

the efficiency of wetlands in improving water quality. The

productivity of mangroves may increase due to discharge of

anthropogenic wastes and this process is beneficial particularly

in those areas where nutrient status is low (Wong et al., 1995).

However, excessive discharge of waste may also cause a

negative impact on the positive health of the ecosystem, which

may reduce the efficiency of the system in the process of

biopurification.

Dumping of sewage has become very common in mangrove

systems mainly because of the following factors (Mitra et al.,

2004).

1. The sewage on its way through the mangrove habitat gets

dispersed over vast areas.

SUSANTA KUMAR CHAKRABORTY

257

2. The vegetation automatically filters the nutrients needed

for its growth.

3. The mangrove soil, algae, microbes and physical processes

also absorb large amount of the pollutants (Wong et al.,

1995).

4. The capacity of sequestering the pollutants increases with

the progression of time.

Nutrients (primarily nitrate and phosphates) are often the major

components of sewage load. Researchers have studied the

ability of mangals to absorb nutrients and the effects of the

pollutants on the mangal community and a whole. In general,

mangrove soils have unique capability of trapping wastewater

borne phosphorus, but are less effective in removing nitrogen

(Tam and Wong, 1995). High levels of organic pollutants can

contribute to diseases, death and changes in the species

composition within the mangal (Tattar et al., 1994).

The mangrove soil, algae, microbes, and physical processes

absorb large amounts of pollutants. Nutrients (primarily

nitrogen and phosphorus) are often major components of the

pollution. High levels of organic pollution contribute to disease,

death, and changes in species compositions within the mangal

(Tattar et al., 1994). Oil pollution from oil or gas exploration,

petroleum production and accidental spills severely damages

mangrove ecosystems (Mastaller, 1996). Oiling of mangroves

causes defoliation of the trees. Grant et al. (1993) demonstrated

that sediment oil can inhibit establishment and decrease

survival of mangrove seedlings for several years.

Response to heavy metals: Metal pollution in the estuarine,

harbor and coastal environment is usually caused by land

run-off, mining activities and anthropogenic inputs (Panigrahy

et al, 1999). In coastal West Bengal, the high concentrations

of Zn, Cu, Pb in the sediment and surface waters of Jambu

Island, Frazergaunge and Kakdwip may be related to the

presence of fish landing stations in these areas. A large number

of fishing vessels and trawlers that are engaged in fishing and

landing operations use antifouling paints for their regular

conditioning and protection from biofoulers like barnacle.

Heavy metals like Zn, Cu and Pb being the principal ingredients

of the antifouling paints often contaminate the ambient media

(Goldberg, 1975). Avicennia alba, Avicennia marina, Exoecaria

agallocha and Acanthus ilicifolius have been found to be

unique accumulator of Zn, Cu and Pb. In all the species, the

metal accumulated in the order Zn>Cu>pb>hg in all the

vegetative parts. In a mangrove associated macroalgae

Enteromorpha sp. (Class: Chlorophycea0 this trend has not

been violated (Mitra et al., 2004).

Response to global changes: Because of their location at the

interface between land and sea, mangroves are likely to be

one of the first ecosystems to be affected by global changes.

Most mangrove habitats will experience increasing

temperature, changing hydrologic regimes (e.g., changes in

rainfall, evapotranspiration, runoff and salinity), rising sea level

and increasing tropical storm magnitude and frequency

(Michener et al., 1997). If temperatures exceed 35ºC, root

structures, seedling establishment and photosynthesis will all

be negatively affected. Reduced rainfall and runoff would

produce higher salinity and greater seawater-sulfate

concentrations thus decreasing mangrove production.

Zonation of mangroves: flora and fauna

Mangrove species display distinct zonation in respect of their

adaptability to different environmental stimuli. Small

environmental variations within mangrove forests may lead to

greatly differing methods of coping with the environment.

Therefore, the mix of species at any location within the

intertidal zone is partly determined by the tolerances of

individual species to ecohydrological factors like tidal

inundation exposure and salinity, erosion, but may also be

influenced by other factors such as predation of plant seedlings

by crabs.

The intricate root systems of mangrove plants provide a habitat

for a number of benthic organisms like algae, molluscs,

polychaetes, crabs, bryozoans etc which all require a hard

substratum for anchoring while they filter feed, and help to

impede water flow, thereby enhancing the deposition of

sediment in areas where it is already occurring. Usually, the

fine, anoxic sediments under mangroves act as sinks for a

variety of heavy (trace) metals which are scavenged from the

overlying seawater by colloidal particles in the sediments.

Besides supporting the leaves of a galaxy of pelagic and benthic

fauna of ecological and economic importance, the export of

carbon fixed in mangroves plays very important role in coastal

food webs.

A wide variety of plant species can be found in mangrove

habitat, but of the recognized 110 species, only about 54

species in 20 genera from 16 families constitute the “true

mangroves”, species that occur almost exclusively in mangrove

habitats and rarely elsewhere. Convergent evolution has

resulted in many species of these plants finding similar

solutions to the problems of variable salinity, tidal ranges

(inundation), anaerobic soils and intense sunlight that come

from living in the tropics (Chakraborty et al., 1989).

Why are mangrove ecosystems one of the most productive

ecosystems of the world?

Mangrove ecosystem- the ecosystem dominated by intertidalsalt tolerant halophytic vegetation enjoying the influences oftwo high and two low tides a day, offers a unique environmentfor biodiversity development (Chakraborty, 1995). Duringhigh tide, major parts of the forest subsystem get inundatedand received the major inputs from estuarine water in theform of moisture recharging components of the bottom soildeposition of sediments and nutrients support (macro, microand trace elements) for the forest subsystem. During low tide,the receding water takes away huge amount of mangrove littercontributed detritus to the adjoining aquatic subsystem. Thenutrients released from detritus are utilized by phytoplanktonalong with plenty of water and sunlight available in the openwater system. Mangroves, being a group of perennial evergreenplants, produce huge amount of leaf litter throughout the yearwhich after falling on the moisture rich surface of silt- clayloaded bottom soil are broken down by a galaxy of benthicfauna (crabs, gastropods, microarthropods etc.) into smallerpieces providing more scopes for microbial communities(bacteria, fungi, protozoa) to act upon them for detritusproduction through litter decomposition. The deposit feeders(crabs, molluscs, polychaetes, nematodes etc) through their

feeding activities turn over the surface sediment layer, thereby

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

258

exposing new litter surfaces to microbial actions (Chakraborty,

2011).

This detritus based coastal ecosystem is highly productive

having a productivity of about 20 times more than the average

oceanic production (Goudha and Panigrahy, 1996).

Productivity of mangrove ecosystem had been attributed to

four reasons: (1) three types of primary production units (marsh

vegetation, benthic algae and phytoplankton); (2) ebb and

flow of water movements resulting from tidal action; (3)

abundant supplies of nutrients and (4) rapid regeneration and

Floral groups Sundarban Midnapore coast Faunal groups Sundarbans Midnapore coast

True Mangrove 39 16 Zooplankton >100 40

Mangrove associated plant 48 19 Actinarians 07 04

Mesophyte invasive plant 10 6 Polychaetes 59 28

Algae (both benthic & plankton) 150 28 (benthic) Brachyuran crabs 26 14

Molluscs 130 43

Table 1: Diversity of floral and faunal components in mangrove ecosystems of Sundarbans and Midnapore coast, West Bengal

Primary ProducersF

O

R

E

S

T

PhytoplanktonA

Q

U

A

T

I

C

Mangrove

Plants

Benthic algae

Primary Trophic

level

Subsystem

Primary Consumers(Herbivores)

Rotifera , Cladocera ,

Copepods,

Icthyoplankton etc.

Insects, Crabs, Birds,Molluscs , Deer, Wild Boars,Monkeys etc.

Secondary Trophic

level

Secondary Consumers

(Carnivores/Omnivores)

Zooplankton( Chaetognatha )

Subtidal

Benthos(starfish )

and Small Fishes etc

Polychaetes , Globid fishesFishing Cats, Sankes

Birds etc.

.

Tertiary Trophic

Level

Highest Consu mers

(Top Carnivores)

Crocodile

Tiger

Highest Trophic

Level

-----

-----

-----

-----

-----

-----

-----

-----

-----

Primary ProducersF

O

R

E

S

T

PhytoplanktonA

Q

U

A

T

I

C

Mangrove

Plants

Benthic algae

Primary Trophic

level

Subsystem

Primary Consumers(Herbivores)

Rotifera , Cladocera ,

Copepods,

Icthyoplankton etc.

Insects, Crabs, Birds,Molluscs , Deer, Wild Boars,Monkeys etc.

Secondary Trophic

level

Secondary Consumers

(Carnivores/Omnivores)

Zooplankton( Chaetognatha )

Subtidal

Benthos(starfish )

and Small Fishes etc

Polychaetes , Globid fishesFishing Cats, Sankes

Birds etc.

.

Tertiary Trophic

Level

Highest Consumers

(Top Carnivores)

Crocodile

Tiger

Highest Trophic

Level

-----

-----

-----

-----

-----

-----

-----

-----

-----

Figure 2: Trophic relationships in mangrove ecosystem

Figure 3: Diagrammatic representation of food-web in mangrove

ecosystem of Sundarbans, India

conservation of nutrients due to the activity of microorganisms

and filter feeders (Schelake and Odum, 1962) (Fig. 2 and 3).

Biodiversity of Mangrove ecosystems

Global perspective: The genetic as well as species diversity of

mangrove tree species within a given area has been found to

be low compared with other tropical forests and coral reefs.

Research evidence suggests that much greater species richness

is found among fungi, bacteria, protists, viruses, and other

invertebrate phyla (Kathiresan and Bingham, 2001).

As in other ecosystems, species diversity declines as individual

body size increases. Most aquatic invertebrate groups consist

of a few to <50 species within a given forest area (Alongi and

Sasekumar, 1992) with highest diversity most often found

among the crustaceans (Kathiresan and Bingham, 2001).

Insects and birds, although most are only temporary visitors,are highly diverse with species numbers often exceeding 300within a single mangrove estuary. Fish are the most diverseamong vertebrate phyla with species numbers usually rangingfrom 100 to 250 per estuary (Robertson and Blaber, 1992). Ina southeast Asian mangrove estuary, a maximum of 260 fishspecies was recorded (Hong and San, 1993). Such wide rangesof species numbers are a reflection of variable environmentalconditions.

For instance, east Africa has a reduced mangrove crab richness(about 35 species) compared with southeast Asia (>100species; Gillikin and Schubart, 2004), mirroring the diversity

differences between the regions in mangrove flora. At the local

scale, metazoan diversity is, on average, higher on the tree

(encrusting or epibiont assemblages) or on the forest floor

surface and in tidal waters than within the forest floor (Alongi,

1989).

Like other forests, the fauna and flora inhabiting the mangrove

canopy are important in structuring food webs and in

influencing the species composition of mangroves, but this

SUSANTA KUMAR CHAKRABORTY

259

was not recognized until quite recently (Ellison and Farnsworth,

2001; Kathiresan and Bingham, 2001). Insects ordinarily

consume mangrove material equivalent to only approximately

5% of net primary production (Robertson, 1991), but recent

findings point to the importance of insects in affecting the

establishment and growth of seedlings (Minchinton and Dalby-

Ball, 2001; Burrows, 2003; Sousa et al., 2003) and as

pollinators (Ellison and Farnsworth, 2001).

Birds and mammals either temporarily or permanently reside

in mangrove forests, using the forest as shelter and to find

food. The works (Lefebvre et al., 1992, 1994; Lefebvre and

Poulin, 1996, 1997) have established the importance of

mangroves as a home for many species of birds, with some

forests containing up to 315 species and feeding extensively

on invertebrates on the trees, on the forest floor, and in tidal

water.

Scenario in West Bengal: Sundarbans and Midnapore Coast.

Sundarbans Mangrove Ecosystem

Sundarbans mangrove ecosystem harbours various floral

species viz. 34 true mangrove species, more than 50 mangrove

associate species, 163 species of fungi, 150 species of algae,

32 species of lichens and 40 species of mangrove associate.

Among true mangrove plant species, special mention may be

made of Rhizophora apiculata, Sonneratia apetala, Avicennia

marina, Excoecaria agallocha, Bruguiera cylindrica, Acanthus

ilicifolius etc. The mangrove associated plants are represented

by species such as Sarcolobus carinatus, Suaeda maritima,

Pandanus tectorius etc. Some examples of the mesophytic

bioinvasive plants occurring in the three study sites are

Casuarina equisetifolia, Alternanthera sp. etc. Important

phytoplankton species include Nitzschia sp., Peridinium sp.

Ceratium sp (Chakraborty and Choudhury, 1994; Chakraborty

et al., 2010).

The faunal biodiversity of Sundarbans mangrove ecosystem

includes 215 species of fishes, 7 species of amphibia, 59

species of reptiles, more than 100 species of birds, 39 speciesof mammals, besides numerous species of phytoplankton,zooplankton, ichthyoplankton, benthos, soil inhabiting andmangrove plants dependant insects. The faunistic compositionof zooplankton in this system includes copepods as principalcomponent of the total zooplankton (67.8% to 90%). A totalof 36 copepod species belonging to 19 families and 21 generahave been recorded. Other zooplanktonic forms aremysidacea, sergestidae, amphipoda, cladocera, ostracoda,

cumacea, chaetognatha, hydromedusea etc (holoplankters)

and polychaete larvae, nauplius, zoea, megalopa, fish eggs

and larvae, echinoderm larvae etc (meroplankters) (Annon,

2003; Chakraborty et al., 2010).

Nektonic fauna include hundred of species under 29 families.

Important ichthyoplanktons mainly belong to the families

Clupeidae, Engraulidae, Megalopidae etc.

A hoard of benthic fauna, both infauna (sessile, semisessile

and burrowing) and epifauna (crawlers and creepers) are the

happy residents of these habitats. Benthic fauna are divisible

into three broad groups based on their body sizes-macrobenthos, meiobenthos and microbenthos. Among the

intertidal macrobenthic fauna, 26 species of brachyuran crabs

belonging to 15 genera and 5 families have been recorded

from the deltaic Sundarbans estuarine complex. A total of 69

species of polychaetes under 45 genera and 25 families have

been documented from this ecosystem. 110 species of benthic

mollusca classified under class gastropoda (59 species) and

bivalvia (40 species) and a rich abundance of benthic insects

have also been identified. 44 species of microarthopods

belonging to six major taxonomic groups viz. Acarina,

Collembola, Coleoptera, Diptera, Isoptera, and Hymenoptera

have been identified. Actiniarian, sipunculans, echiurans,

hemichordates, globid fishes etc are other important benthic

faunal groups. 80 species of nematodes belonging 26 families

have been documented which are the major meiofaunal groups

(Chakraborty et al., 2011).

Midnapore coastal tract

The floral diversity includes 32 families of mangroves, 28

species of benthic algae under 4 families and 8 phytoplankton

species under 3 families have been recorded in Midnapore

coastal belt.

The faunal components of Midnapore coast remain in the

state of pelagic and benthic forms. Seventeen species of

zooplankton mainly comprising of copepoda, chaetognatha,

rotifera and some considerable number of nauplius larvae

have been recorded. Seventeen species of zooplankton mainly

comprising of copepoda, chaetognatha, rotifera and some

considerable number of nauplius larvae have been recorded.

A total number of 48 molluscan species belonging to 3 classes,

15 orders and 36 families have been reported from intertidal

habitats.A total number of 22 polychaete species belonging

to 10 families have been documented. A total number of 12

actinarian species belonging to 2 classes, 3 orders and 6 families

have been observed in different study sites. Besides, sea

cucumbers (Holothuroida), sea pen (Cnidaria), Lingula sp

(Brachyopoda), were found to occur in mudflats of Talsari,

Shankarpur, Junput, and Nayachar Islands. Out of 68

arthropod species recorded from this coast, 13 species

brachyuran crabs, 13 species of prawns and shrimps, 21

insects belonging to 33 families represent the major groups of

fauna . A total number of 51 soil microarthropods belonging

to insects orders viz. Collembola, Hymenoptera, Diptera and

Isoptera have been recorded from different parts of this coast.

Both the species of horse- shoe crabs viz. Carcinocorpius

rotundicauda and Taphypleus gigas have been also observed

in Digha-Talsary intertidal flats. A total of 51 fish species under

2 classes, 9 orders and 25 families have been documented

from different fish markets and landing centers (Chakraborty

et al., 2010).

Functional contribution of macrobenthic fauna – Crabs and

Microarthropods

Different intertidal brachyuran crabs especially those belonging

to the families grapsid and ocypodid are the most important

faunal components influencing the structure and function of

many tropical mangrove forests, after bacteria and the trees

(Lee, 1998)). Mangrove crabs used to adjust to significant

temperature and salinity fluctuations, which they do by

adopting nocturnal foraging behavior, retreating into burrows

in the day, decreased urine production etcThrough their life

activities, they exert extraordinary influence on the structure

and function of mangrove ecosystem. Through their

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

260

consumption of mangrove leaf litter, they significantly reduce

the amount of detritus available for export, thus enhancingretention and recycling of nutrients and organic matterinternally; their wastes can support coprophagous organismsfurther ensuring conservation of materials within the forest,and their selective consumption of mangrove propagulesaffects forest structure by reducing the recruitment and relativeabundance of tree species whose propagules are preferentiallyconsumed (Lee, 1999; Kristensen, 2008). Bioturbation by crabsalso results in changes in soil texture and chemistry, surfacetopography, degree of anoxia, and abundance of meiofaunawhile stimulating microbial production (Alongi, 2009). Thepresence of crab burrows enhances the flow of tidal waterthrough the forest floor, speeding up the flow of water andassociated dissolved and particulate material between forestand adjacent waterway (Ridd, 1996; Chatterjee et al., 2008).

Recent work has focused on clarifying the trophic role of crabs,especially positive feedback loops and interactions with treesand other flora and fauna in relation to food availability(Ashton, 2002; Kristensen and Alongi, 2006), and theirreproductive and life history strategies in relation to treecomposition and environmental factors (Lee and Kwok, 2002;Koch et al., 2005; Moser et al., 2005). In mesocosmexperiments, Kristensen and Alongi (2006) found that the

presence of the fiddler crab, Uca vocans, stimulated the growth

and development of Avicennia marina saplings but depressed

the abundance and productivity of microalgal mats at the soil

surface. Smith et al. (1991) found that the absence of crabs

increased the concentration of ammonium and sulfide in soils,

but reduced plant stipule and propagule production. The

presence of crabs therefore facilitates plant growth by aeratingthe soil to limit the buildup of toxic metabolites. The presenceof tree species may also influence crab productivity by way ofaltering tidal height, modification of soil texture and nutrientavailability (Lee and Kwok, 2002). Regardless of themechanisms involved, positive interactions between trees,crabs, and microbes make ecological sense in that the overallstability of mangrove ecosystems is enhanced (Alongi, 2002).

Digging by crabs, in conjunction with other benthic fauna likenematodes, polychaetes, and mudskippers can also have aprofound effect on nutrient cycling and the physical andchemical environment of the mangal (Lee, 1998). Burrowsenhance aeration, facilitate drainage of the soils, and promotenutrient exchange between the sediments and the overlayingtidal waters. One characteristic features of burrowing by crabsis the formation of varied structures by bio-turbation.Bioturbation is the stirring or mixing of sediment layers bybiological activities, mobility, feeding, burrowing etc. of benthicfaunal components. Bioturbation affects the geochemistry ofsediments and their interstitial water by mixing the soil of upperlayer with the lower one, pumping water and oxygen into thedeep layers of sediment providing different niche for the growthand propagation of microorganisms. It influences the microbialdegradation rate of sediment particulate organic matters byway of affecting the standing crop, community structure andphysiological state of microbial, micro and meiobenthiccommunity. A study from Midnapore Coastal Belt revealedthat different brachyuran crabs construct different categoriesof burrows of different depths, shapes, and diameters in orderto ensure courtship, breeding, feeding and escaping from

predators which show distinct variations in different seasons,

mudflats, sandflats and tidal levels. The various bioturbatory

structures formed by brachyuran crabs in the coastal belt of

West Bengal include Pseudo pellets, Sand Ball, Mud balls,

San Pyramids, Semi domes, Chimneys, Hoods etc (Chatterjee

et al., 2008).

Microarthropods: Soil microarthropods are considered to be

among the strongest determinants of plant litter decomposition

in warm, humid sites. These faunal components not only

enrich the biodiversity wealth of the system but also play crucial

role in nutrient cycling by the way of mangrove litter

decomposition. Microarthropod population peak coincide

with the maximum nutrient status of decomposing litters (Dey

et al., 2010). It has also been proposed that climate change

may increase the effects of elevation on soil microarthropod

litter processing (Wang et al., 2009).

Seasonal variation of physico-chemical factors, soil, water

and their interrelationships

Different physicochemical parameters displayed a wide range

of temporal and spatial variation. Water temperature, salinity,

pH, conductivity, turbidity, dissolved oxygen (DO), and

biochemical oxygen demand (BOD) were found to be higher

during pre-monsoon, while, silicate, phosphate phosphorous,

nitrite nitrogen, ammonical nitrogen, and nitrate nitrogen were

maximum during monsoon. The post-monsoon season was

characterized in having lowest temperature, moderate salinity,

and other parameters. Soil temperature, salinity, organic

carbon, and sand content were found to be higher during pre-

monsoon, while available potassium, available nitrogen, and

available phosphorous were maximum during monsoon. The

post-monsoon season was characterized in having lowest

temperature, available phosphorous, available potassium,

available nitrogen, and moderate level of other parameters.

CCA involving 12 environmental parameters of water viz.

temperature, pH, salinity, turbidity, conductivity, dissolved

oxygen, biochemical oxygen demand, silicate, phosphate

phosphorous (W PO4), nitrate nitrogen (W NO3), ammonical

nitrogen (W NH3), nitrite nitrogen (W NO2), and 10

environmental parameters of soil viz. temperature, pH, organic

carbon, salinity, available potassium, available phosphorous,

available nitrogen, and textural components (sand, silt, and

clay) revealed interrelationships among different

macrozoobenthic species in terms of their different ecological

parameters on one hand and also recorded cumulative

influence of a group of ecological parameters on the

abundance of macrozoobenthic population on the other

(Chakraborty et al., 2010). In Midnapore coast, different

physico-chemical parameters also exhibited seasonal

variations like water temperature (20.8°C-32.8°C), soil

temperature (20.1°C-34.8°C), salinity of water (8.6%-26%),

salinity of soil (10%-33.4%), D.O. (3.24 mg/L) to 5.47 mg/L,

pH of water (7.15-8.17) and pH of soil (7.68-8.72). Besides,

texture of sediment displays variations among different parts

and tidal levels of this coastal belt (Khalua, 2008).

Management of Mangrove coastal belts of West Bengal

Several natural and anthropogenic threats have been inflicting

their impact on biodiversity of West Bengal Coast in several

ways which are mentioned below:

SUSANTA KUMAR CHAKRABORTY

261

• Non judicious exploitation of mangrove bioresources to

meet the demand of steadily increasing local human

population.

• Considerable changes of land use pattern for the

development of aquaculture, fisheries and agriculture

promoted large scale reclaimation of land of virgin deltaic

islands leading to deforestation (Hazra et al., 2002;

Chakraborty et al., 2010).

• Large scale destruction of juveniles of hundred of species

of different fishes, and shell fishes for the collection of

shrimp juveniles, especially juveniles of Peneaus monodon

to be used in semi intensive aquaculture.An estimate shows

for the collection of one juvenile of Peneaus monodan,

juveniles of other aquatic fauna having a range of 27.41 to

31.77 at different sites of Sundarbans were destroyed

(Annon, 2003).

• Fishermen camps often lead to disturbances to the coastal

ecosystem functioning because of the release of different

waste materials as well as operation of increased number

of nylon nets having small mesh size to the death of marine

turtles, migratory birds and threatened fish species

(Chakravorty et al., 2004).

• Changing flow pattern of Ganga River during last centuries

because of faulty neotectonic movements has influenced

the hydrology of deltaic region and modified the

sedimentation patterns and reduction of fresh water inflow

leading to salinity invasion. (Gopal and Chauhan, 2006;

Hazra et al., 2002).

• Indiscriminate use of agrochemicals (fertilizers and

pesticides) in the catchments of Ganga and Brahamaputra

rivers, their numerous tribularis as well as in agriculture

fields close to the mangroves, pollute both the water ways

and the land mass and thereby affect the vegetation and

fauna directly.

• From seaward side, major pollution occurs through oil

spills that cause damage especially to aquatic fauna and

seabirds (Qasim et al., 1988). Besides, thousand of

mechanized boats for carrying passengers and fishing, are

the major source of oil pollution (Paul, 2002).

• Construction of embankment and dredging of riverbeds

hamper the water circulation, distabilise bottom sediments,

increase turbidity and affects settlement of flora and fauna

(Paul, 2002).

• Ecotourism to different parts of Sundarbans (Sagar Island,

Bakhali, Sajnekhali etc) contribute profusely for the

ecodegradation of the West Bengal coast.

• Growing Industrialization of the area around Kolkata and

Haldia industrial complex and industries situated on the

wastern side of the Hoogli estuary, contribute significantly

to the pollution load and hence to the degradation of

mangroves. (Chakravorty et al, 2004).

• Errosion and accretion pattern in Sundarbans: A time series

analysis of the change in the shape, size and geomorphic

features of the island over the part 32 years (1969-2001)

show some important changes like degradation of

mangrove swamps and mudflats, increase in salinisation

and development of saline banks within mangrove swamp.

• Global warming: A steady rate of increase of water

temperature (0.050C/year) in this coastal environment over

the past 27 years has had a profound impact on other

physical parameters of estuarine water and enhanced the

salinity (~6 psu over last 30 years), evaporation, free CO2,

precipitation, fresh water runoff and intrusion of sea water

and decreased pH (0.015 per decade) (Mitra et al., 2009).

Management strategies of the Mangrove coastal areas include

In- situ conservation of Wildlife

An integrated approach for the conservation of Sundarban

Mangrove estuarine complex and Midnapore coastal belt in

general and the flora and fauna in particular is very much

needed.

• To conserve diversity and integrity of plants, animals and

micro- organisms;

• To promote research on ecological conservation and other

environmental aspects;

• To provide facilities for education, awareness and training

for effective participation of the people living around

biosphere reserves.

Participatory management of bioresources

The stability of ecosystem is individually insignificant but

collectively determined cumulative ecological effects are not

attributable to any one source or action and cannot be

regulated in isolation. This requires cross sectional approaches

to natural resource management which should take into

account the participatory management practices in order to

integrate the goals of conservation into mainstream of

economic development (Patra et al., 2005; Mishra et al., 2009).

Integrated coastal zone management

An integrated management scheme for the judicious utilization

of coastal resources and also to minimize eco- degradation

involves monitoring changes and the handling of much

information. These tasks have been aided in recent years by

the application of remote sensing techniques and Geographic

Information system (GIS) (Paul, 2009).

The Ministry of Environment and Forests enacted the CRZ

notification in 1991 under the Environment Protection Act to

protect coastal areas from over- development and

industrialization. The CRZ areas of the country is defined as

coastal stretches of sea, bays estuaries, creeks, rivers, back

waters, all influenced by tidal action on the landward margins.

However, based on ecological sensitivity, geomorphic features

and demographic distribution, the CRZ is categorized into

four significant areas as:

CRZ-I: (ecologically sensitive and tidally influenced upto 500m

from HTL)

CRZ-II: (Urban built-up areas or densely developed areas along

the shoreline)

CRZ-III: (rural coastal dwelling units or developed areas of the

coast).

CRZ-IV: (islands surrounded by water bodies and isolated from

the main land).

Much of Purba-Medinipur coastal district falls within CRZ-I

and CRZ-III. Areas of CRZ-III are further sub-divided. The area

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

262

upto 200 meters HTL is no construction zone where only

repairs of existing authorized constructions are permitted or

allowed.

Restoration

In terms of ecology, restoration will seldom mean returning an

ecosystem to its initial state but will more often mean bringing

it back to a state of effectiveness. A practical definition of

restoration is given by Morrison (1990) ‘Restoration is the re-

introduction and reestablishment of community-like groupings

of native species to sites which can reasonably be expected to

sustain them with the resultant vegetation demonstrating

aesthetic and dynamic characteristics of the natural

communities on which they are based.’ Field (1998)

distinguished between rehabilitation - ‘the partial or full

replacement of the ecosystem’s structural and functional

characteristics’ and restoration - ‘the act of bringing an

ecosystem back to its original condition’.

Restoration provides an opportunity to improve or enhance

the landscape and increase environmental quality (Kairo et

al., 2001).

Mangrove resilience factors that are a prerequisite for

mangrove restoration

1. Association with drainage systems including permanent

rivers and creeks that provides freshwater inputs and

sediment supply.

2. Sediment rich-macrotidal environments to facilitate

sediment redistribution and accretion

3. Mangroves backed by low-lying retreat areas (for

example, salt flats, marshes, coastal plains) which may

provide suitable habitat for colonization and landward

movement of mangroves in view of rising sea level.

4. Mangroves in areas where abandoned alternate land

use provides opportunities for restoration, for example,

flooded villages, tsunami-prone land, unproductive

pond.

5. Areas with a large tidal range may be better able to adjust

to increases in sea level due to stress tolerance

6. Permanent strong currents to redistribute sediment and

maintain open channels

7. Diverse species assemblage and clear zonation over

range of elevation (intertidal to dry land)

8. Tidal creek and channel banks consolidated by

continuous dense mangrove forest (which will keep

these channels open)

9. Access to healthy supply of propagules, either internally

or from adjacent mangrove areas

10. Close proximity and connectivity to neighboring stands

of healthy mangroves

11. Access to sediment and freshwater

12. Limited anthropogenic stress

13. Integrated Coastal Management Plan or Protected Area

Management Plan implemented

DISCUSSION

Mangrove ecosystem is a highly valued ecosystem in terms of

economy, environment and ecology. Its uniqueness is in therandom and rapid fluctuations in varied physico-chemicalparameters, and the surprising degree of adaptation displayedby the resident biota in response to such fluctuations (Chandraet al., 2003; Mishra et al., 2009).

A review of the available literature on mangrove plantationestablishments shows mixed successes of restoration efforts(Ellison 2000), even though it has been said that mangrovewetlands are easy to restore and create (e.g. FAO, 1994).Whereas the lost mangrove plant species can be returned(Kairo, 1995a), a restored forest may or may not function asthe original pre-disturbed system (McKee and Faulkner, 2000,Bosire, 1999). If a mangrove forest is disturbed by logging it isunlikely that the forest will regenerate to function as the pre-disturbed state, since the species mix, soil type, stocking ratesand numbers of animals will certainly have changed.

When contemplating mangrove rehabilitation, specialattention must be paid to soil stability and flooding regime(Pulver, 1976), site elevation (Hoffman et al., 1985), salinityand fresh water runoff (Jeminez, 1990), tidal and wave energy(Field, 1996), propagule availability (Loyche 1989; Kairo,1995a, 2001), propagule predation (Dahdouh-Guebas et al.,1997), spacing and thinning of mangroves (FAO, 1985; Kairo,2001), weed eradication (Saenger and Siddique, 1993),nursery techniques (Siddique et al., 1993), monitoring (Lewis,1990), community participation (Kairo, 1995b) and total costof restoration measures (Field, 1998).

CONCLUSION

Although, significant measures have been taken up for the

conservation of biodiversity of Sundarbans and Midnapore

coast, an integrated action plan is required incorporating the

outcome and recommendations of multidimensional

researches undertaken during the last four decades. Based on

these, proper guidelines are to be framed for future researchers

on this globally important environmental sector so that TimeSeries Analysis and Long Trend Analysis on the natural and

anthropogenic stress factors become possible. These will

facilitate the process of pointing out problems more distinctly

and remedial measures more effectively.

REFERENCES

Alongi, D. M. 1989. The role of soft-bottom benthic communities in

tropical mangrove and coral reef ecosystems. Rev. Aquat. Sci. 1: 243-

280.

Alongi, D. M. and Sasekumar, A. 1992. Benthic communities. In:

Tropical Mangrove Ecosystems. A.I. Robertson and D.M. Alongi (Eds.).

American Geophysical Union, Washington DC, pp. 137–171.

Alongi, D. M. 1996. The dynamics of benthic nutrient pools and

fluxes in tropical mangrove forests. Journal of Marine Research. 54:123

148.

Alongi, D. M. 2002. Present state and future of the world’s mangrove

forests. Environ. Conserv. 29: 331–349.

Alongi, D. M. 2009. Paradigm shifts in mangrove biology. In: Coastal

Wetlands: An integrated ecosystem approach. Elsevier. pp. 628-629

Annon. 2003. Mangrove ecosystem: Biodiversity and its influence on

the natural recruitment of selected commercially important finfish

and shellfish species in fisheries. National Agricultural Technology

Project (NATP). Indian Council of Agriculture Research (ICAR).

SUSANTA KUMAR CHAKRABORTY

263

Principal Investigator: George, J.P.; Co-PI: Chakraborty, S.K. and

Damroy, S.N.: 1 – 514.

Ashton, E. C. 2002. Mangrove sesarmid crab feeding experiments in

peninsular Malaysia. J. Exp. Mar. Biol. Ecol. 273: 97-119.

Bacon, P. R. 1987. Use of wetlands for tourism in the insular

Caribbean. Annals of Tourism Research 14: 104–117

Bosire, J. O. 1999. Floristic and faunistic secondary succession in a

mangrove ecosystem in Kenya. MSc Thesis, Vrije Universiteit Brussels,

Belgium

Bridgewater, P. B. 1989. Syntaxonomy of the Australian mangal

refined through iterative ordinations. Vegetatio. 81: 159-168

Bunt, J. S., Williams, W. T. and Bunt, E. D. 1985. Mangrove species

distribution in relation to tide at the seafront and up rivers. Aust. J.

Mar. Freshwater Res. 36: 481-492.

Burns, K. A., Garrity, S. D., Jorissen, D., MacPherson, J. and Stoelting

M. 1994. The Galeta oil spill. II: Unexpected persistence of oil trapped

in mangrove sediments. Estuarine Coastal and Shelf Science. 38: 349–

364

Burrows, D. W. 2003. The Role of Insect Leaf Herbivory on the

Mangroves Avicennia marina and Rhizophora stylosa. PhD Thesis,

James Cook University, Townsville, p.286.

Chakraborty, S. K. and Choudhury, A. 1989. Ecological studies on

the zonation of brachyuran crabs in a virgin mangrove island of

Sundarbans, India. Journal of the Marine Biological Association, India.

34(1 & 2): 189-194.

Chakraborty S. K. and Choudhury, A. 1994. Community structure of

macrobenthic polychaetes of intertidal region of Sagar Island, Hooghly

Estuary, Sundarbans, India. Tropical Ecology. 35(1): 97-104.

Chakraborty, S. K. 1995. Aquaculture potential of mangrove ecosystem

of Sundarbans, India. In: Proceedings of Seminar on Fisheries - a

multimillion dollar industry. AFI, Madras. pp.72-83.

Chakraborty, S. K. 1998. Coastal aquaculture and environment in the

context of West Bengal, India. Vidyasagar University J. Biological

Sciences. 4: 13-20.

Chakravarty, G., Giri, S., Giri, S. and Chakraborty, S. K. 2004.Distribution of coliform bacteria in different estuaries of West BengalCoast, India. In: Protected Habitats and Biodiversity. A.Kumar,J.R.Dhanze, A.K.Chopra and D.S.Malik (Edt). (Publ. by Natconpublication). pp. 395-402.

Chakraborty, S. K. 2010. Coastal environment of Midnapore (East),West Bengal – Potential, threats and management. Journal of CoastalEnvironment. 1(1): 27-40.

Chakraborty, S. K. 2011. Mangrove Ecosystem of Sundarbans, India:Biodiversity, Ecology, Threats and Conservation. In. Mangroves:Ecology, Biology and Taxonomy. James N. Metras (Edt) (Publ. byNOVA publisher, USA). pp.83-112.

Chandra, A. K., Chakravarty, G. and Chakraborty, S. K. 2003.Polychaete diversity of Midnapore Coastal Belt, West Bengal, India. J.Nature Conservators. 15(2): 95-108.

Chapman, V. J. 1976. Mangrove vegetation. J Cramer Verlag, Vaduz,Liechtenstein.

Chatterjee, S., Bhunia, G. and. Chakraborty, S. K. 2008. Bioturbationof Brachyuran crabs and its impact on coastal ecosystem of Midnaporedistrict, West Bengal, India. In Proceedings of Fourth InternationalConference on Environmental Science and Technology at Houston,Texas U.S.A. pp.133-148.

Chaudhuri, A. B. and Chowdhury, A.1994. Mangroves of theSundarbans, India. IUCN-Bangkok. Thailand. I: 1-247.

Dahdouh-Guebas, F., Verneirt, M., Tack, J. F. and Koedam, N. 1997.Food preferences of Neosarmatium meinerti de Man (Decapoda:Sesarminae) and its possible effect on the regeneration of mangroves.Hydrobiologia. 347: 83–89.

Dahdouh-Guebas, F., Mathenge, C., Kairo, J. G. and Koedam, N.

2000. Utilization of mangrove wood products around Mida Creek

(Kenya) among subsistence and commercial users. Economic Botany.

54: 513–527

Davis, J. H. Jr. 1940. The ecology and geological role of mangroves.

In: Florida Carnegie Inst. Wash., Papers of the Tortugas Laboratory.

32: 303–412

Dey, M. K., Hazra, A. K. and Chakraborty, S. K. 2010. Functional

role of microarthropods in nutrient cycling of mangrove-estuarine

ecosystem of Midnapore coast of West Bengal, India. International

Journal of Environmental Technology and Management. 12(1): 67-

84.

Duke, N. C. 1992. Mangrove floristics and biogeography. In: Tropical

mangrove ecosystems. A. I. Robertson and D.M. Alongi (Edts), pp.

63-100. American Geophysical Union, Washington, D.C.

Duke, N. C., Ball, M. C. and Ellison, J. C. 1998. Factors influencing

biodiversity and distributional gradients in mangroves. Global Ecology

and Biogeography letters. 7: 27-47.

Ellison, J. C. and Stoddart, D. R. 1991. Mangrove ecosystem collapse

during predicted sea-level rise: Holocene analogues and implications.

Journal of Coastal Research. 7: 151-165.

Ellison, A. M. 2000. Mangrove restoration: Do we know enough?

Restoration Ecology. 8: 219–229

Ellison, A. M. and Farnsworth, E. J. 1996. Anthropogenic disturbance

of Caribbean mangrove ecosystems: past impacts, present trends, and

future predictions. Biotropica. 24: 549–565

Ellison, A. M. and Farnsworth, E. J. 2001. Mangrove communities.

In: Marine Community Ecology. Hay, M.E. (Ed.), Sinauer Associates,

Inc, Massachusetts. pp. 423–442.

Fahn, A. 1979. Secretory tissues in plants. Academic Press, London.

FAO. 1985. Mangrove management in Thailand, Malaysia and

Indonesia. FAO Environment Paper, Rome, p. 60

FAO 1994. Mangrove forest management guidelines. FAO Forestry

Paper 117. Rome, p. 320

Field, C. 1996. Restoration of mangrove Ecosystems. International

Tropical Timber Organization and International Society for Mangrove

Ecosystems, Okinawa, Japan

Field, C. 1998. Rehabilitation of mangrove ecosystems: an overview.

Marine Pollution Bulletin. 37: 383–392

Furukawa, K. and Wolanski, E. 1996. Sedimentation in mangrove

forests. Mangroves Salt Marshes. 1: 3–10

Furukawa, K., Wolanski, E. and Mueller, H. 1997. Currents and

sediment transport in mangrove forests. Estuar. Coast. Shelf Sci. 44:

301–310.

Gillikin, D. P. and Schubart, C. D. 2004. Ecology and systematics of

mangrove crabs of the genus Perisesarma (Crustacea:Brachyura:

Sesarmidae) from East Africa. Zool. J. Linn. Soc. 141: 435–445.

Goldberg, E. G. 1975. The Mussel Watch – First Step in Global

Marine Monitoring. Ocean Pollution Bulletin. 6: 111.

Gopal, B. and Chauhan, M. 2006. Biodiversity and its conservation

in the Sundarban Mangrove Ecosystem; Aquatic Sciences. 68: 338-

354.

Goudha, R. and Panigrahy, R. C. 1996. The mangrove of Orissa. J.

Indian Ocean Studies. 3(3): 228 – 237.

Grant, D. L., Clarke, P. J. and Allaway, W. G. 1993. The response of

grey mangrove (Avicennia marina (Forsk.) Vierh.) seedlings to spills of

crude oil. Journal of Experimental Marine Biology and Ecology. 171:

273-295.

Hamilton, L. S. and Snedaker, S. C. (Eds) 1984. Handbook for

mangrove area management. Honolulu, Hawaii: Environment and

Policy Institute, East-West Center. p. 123.

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

264

Hazra, S., Ghosh, T., Dasgupta, R. and Sen, G. 2002. Sea level and

associated changes in the Sundarbans. Science and Culture. 68(9-12):

309-321.

Hoffman, W. E., Durako, M. J. and Lewis, R. R. 1985. Habitat

restoration in Tampa bay. In: Simon SAF, Lewis JL III, Whiman RR, RL

Jr (eds) Treat, Proc. Tampa Bay Area Scientific Inf. Symp. Florida Sea

Grant College, Bellwether Press. pp. 636–657

Hong, P. N. and San, H. T. 1993. Mangroves of Vietnam. IUCN,Bangkok. p.173.

Joshi, G. V. and Bhosale, L. J. 1982. Contributions to the Ecology ofHalophytes. In: Sen, D. N. and Rajapurohit, K. S. (eds) Junk, TheHague, pp. 21-33.

Kairo, J. G. 1995a. Artificial regeneration and sustainable yieldmanagement of mangrove forests in Gazi Bay, Kenya. MSc Thesis,University of Nairobi, Nairobi, Kenya. p. 116.

Kairo, J. G. 1995b. Community participatory forestry for rehabilitationof deforested mangrove areas of Gazi Bay (Kenya). A first approach.Final technical report. University of Nairobi, Department of Botany,Nairobi, Kenya’

Kairo, J. G. and Kivyatu, B. 2000. Mangrove management surveywithin and adjacent to Kiunga Marine National Reserve. WWF/KE:0089/01, Final Technical Project. World Worldlife Fund for NatureEast Africa Regional Program Office (WWF–EARPO), Nairobi. p. 113

Kairo, J. G., Dahdouh-Guebas, F., Bosire, J. and Koedam, N. 2001.Restoration and management of mangrove systems – a lesson for andfrom the East African region. South African Journal of Botany. 67:383-389

Karmarkar, S. M. 1985. Mangroves – a review (Published in: Proc.Nat. Symp. Biol. Util. Cons. Mangroves). pp. 60-79

Kathiresan, K. and Bingham, B. L. 2001. Biology of mangroves andmangrove ecosystems. Advances in Marine Biology. 40: 81-251.

Khalua, R. K., Chakravorty, G. and Chakraborty, S. K. 2008.Community Structure of macrobenthic molluscs of three contrastingintertidal belts of Midnapore Coastal belt, West Bengal. ZoologicalResearch in Human Welfare. 6: 47-55.

Kjerfve, B. 1990. Manual for Investigation of Hydrological Processes

in Mangrove Ecosystems. The UNESCO/UNDP Regional Project

“Mangrove Ecosystems in Asia and the Pacific” RAS/79/ 002 and RAS/

86/120, Thomson Press, p.79.

Koch, V., Wolff, M. and Diele, K. 2005. Comparative population

dynamics of four fiddler crabs (Ocypodidae, genus (Uca) from a

North Brazilian mangrove ecosystem. Mar. Ecol. Prog. Ser. 291: 177–

188.

Kristensen, E. and Alongi, D. M. 2006. Control of fiddler crabs (Uca

vocans) and plant roots (Avicennia marina) on carbon, iron, and

sulphur biogeochemistry in mangrove sediment. Limnol. Oceanogr.

51: 1557–1571.

Kristensen, E. 2008. Mangrove crabs as ecosystem engineers; with

emphasis on sediment processes. J. Sea Res. 59: 30–43.

Lacerda, L. D. 1998. Biogeochemistry of Trace Metals and Diffuse

Pollution in Mangrove Ecosystems. International Society for Mangrove

Ecosystems, Okinawa.

Lee, S. Y. 1998. Ecological role of grapsid crabs in mangroveecosystems: a review. Mar. Freshw. Res. 49: 335–343.

Lee, S.Y. 1999. Ecology of tropical mangals: the need for a synthesisof physical and biotic influences on ecosystem structure and function.Austr. J. Ecol. 24: 355–366.

Lee, S. Y. and Kwok, P. W. 2002. The importance of mangrovespecies association to the population biology of the sesarmine crabsParasesarma affinis and Perisesarma bidens. Wetl. Ecol. Manage. 10:215–226.

Lefebvre, G., Poulin, B. and McNeil, R. 1992. Settlement period and

function of long-term territory in tropical mangrove passerines.

Condor. 94: 83–92.

Lefebvre, G., Poulin, B. and McNeil, R. 1994. Temporal dynamics of

mangrove bird communities in Venezuela with special reference to

migrant warblers. Auk. 111: 511–514.

Lefebvre, G. and Poulin, B. 1996. Seasonal abundance of migrant

birds and food resources in Panamanian mangrove forests. Wilson

Bull. 108: 748–759.

Lefebvre, G. and Poulin, B. 1997. Bird communities in Panamanian

black mangroves: potential effects of physical and biotic factors. J.

Trop. Ecol. 13: 405–415.

Lewis, R. R. 1990. Creation and restoration of coastal wetlands in

Puerto Rico and the US Virgin Islands. In: Wetland Creation and

Restoration: The Status of Science, Kusler JA, Kentula ME (eds) Vol. I:

Regional Reviews, Island Press, Washington

Loyche, M. 1989. Mangrove of West Africa — the forest within the

sea. Mangroves and Fish. IDAF Newsletter. 9: 18–31

Macnae, W. 1974. Mangrove forest and fisheries Indian Ocean

Programme, 34. Indian Ocean Fisheries Commission, Rome. 1 OFC/

DEV/74/34: 1-35.

Mastaller M. 1996. Destruction of mangrove wetlands – causes and

consequences. A Biannual Collection titled Natural resources and

development– Focus: Mangrove forests. Institute for Scientific

Cooperation, Tubingen. 43/44.

Mazda, Y., Kanazawa, N. and Kurokawa, T. 1999. Dependence of

dispersion on vegetation density in a tidal creek-mangrove swamp

system. Mangroves and Salt Marshes. 3: 59–66.

McKee, K. L. and Faulkner, P. L. 2000. Restoration of biogeochemical

function in mangrove forests. Restoration Ecology. 8: 274–259

Mazda, Y., Wolanski, E. and Ridd, P. V. 2007. The Role of Physical

Processes inMangrove Environments: Manual for the Preservation

and Utilization of Mangrove Ecosystems. TERRAPUB, Tokyo, p.598.

Mazda, Y. and Kamiyama, K., 2007. Tidal deformation and inundation

characteristics within mangrove swamps. Mangrove Sci. 4/5: 21–29.

Mazda, Y. and Wolanski, E. 2009. Hydrodynamics and modeling of

water flow in mangrove areas. In: Coastal Wetlands: An integrated

ecosystem approach. pub. Elsevier.

McKee, K. L. 1993. Soil physico-chemical patterns and mangrove

species distribution: Reciprocal effects? Journal of Ecology. 81: 477-

487.

Michener, W. K., Blood, E. R., Bildstein, K. L., et al. 1997. Climate

change, hurricanes and tropical storms, and rising sea level in coastal

wetlands. Ecol Appl. 7: 770–801.

Minchinton, T. E. and Dalby-Ball, M. 2001. Frugivory by insects on

mangrove propagules: effects on the early life history of Avicennia

marina. Oecologia. 129: 243–252.

Mishra, S. S., Acharjee, S. K. and Chakraborty, S. K. 2009. Development

of tools for assessing conservation categories of siluroid fishes of fresh

water and brackish water wetlands of South West Bengal, India. J.

Environmental Biology of Fishes. 84: 395-407

Mitra, A., Banerjee, K. and Bhattacharyya, D. P. 2004. The other

faces of mangrove. Pub. Dept. of Environment, Govt. of West Bengal.

Moser, S., Macintosh, D., Laoprasert, S. and Tongdee, N. 2005.

Population ecology of the mud crab Scylla olivacea: a study in the

Ranong mangrove ecosystem, Thailand, with emphasis on juvenile

mortality. Fish. Res. 71: 27–41.

Morrison, D. 1990. Landscape restoration in response to previous

disturbance. In: Landscape heterogeneity and disturbance. Turner

MG (Ed.) Springer-Verlag, New York. pp. 159–172

Naskar, K., Sen-Sarkar, N., Ghosh, A., Dasgupta, M. and Sengupta,

B. 2004. Status of the mangroves and mangrove ecosystem of

SUSANTA KUMAR CHAKRABORTY

265

Sundarbans in West Bengal: its impact on estuarine wetlands fisheries.

CIFRI Bull. 134: 8.

Odum, E. P. and Heald, E. J. 1975. Mangrove forests and aquatic

productivity. In: Haster, A.D. (Ed) Coupling of Land, water systems.

Ecological Studies (Springer-Vesllog, New York), 10: 129-136

Odum, W. E. and Heald, E. J. 1975. The detritus food web of an

estuarine mangrove community. In: Estuarine Research. Cronin L

(Ed.) Academic Press, New York, USA, pp. 265-286

Panigrahy, P. K., Das, J., Das, S. N. and Sahoo, R. K. 1999. Evaluation

of the influence of various physicochemical parameters on water

quality around Orissa by factor analysis. lnd. Jour. Mar. Sci. 28: 360

- 364.

Patra, M. K. Acharjee, S. K. and Chakraborty, S. K. 2005. Conservation

categories of siluroid fishes in North-East Sundarbans, India.

Biodiversity and Conservation. 14: 1863-1876

Paul, A. K. 2002. Coastal Geomorphology and Environment. (Published

by- Ajoy Bhattacharya of acb publications). 1-575

Paul, A. K. 2009. Man-Environment interactions in the single largest

mangrove forest along the shoreline of the Bay of Bengal : A case

study of Sundarbans. Geomorphology in India (edts H.S. Sharma and

V.S Kole): pp. 263-286.

Primavera, J. H. 1995. Mangroves and brackish water pond culture

in the Philippines. Hydrobiologia. 295: 303–309

Pulver, T. R. 1976. Transplant techniques for sapling mangrove trees,

Rhizophora mangle, Laguncularia racemosa and Avicennia germinans,

in Florida. Florida Marine Research Publications 22. Contribution

No. 282, St. Petersburg, Florida, USA. p. 14

Qasim, S. Z. Sengupta, R. and Kureishy, T. W. 1988. Pollution of the

seas around India. Proceedings of Indian Academy of Science (Animal

Science). 97(2): 117-131.

Ricklefs, R. E. and Latham, R. E. 1993. Global patterns of diversity in

mangrove floras. In. Species diversity in ecological communities. R.E.

Ricklefs and D. Schulter, (ed.) pp. 215-229. University of Chicago

Press, Chicago.

Ridd, P. V., Sandstrom, M. W., Wolanski, E. 1988. Outwelling from

tropical tidal saltflats. Estuar. Coast. Shelf Sci. 26: 243-253.

Ridd, P. V. 1996. Flow through animal burrows in mangrove creeks.

Estuar. Coast. Shelf Sci. 43: 617–625.

Robertson, A. I. 1991. Plant-animal interactions and the structure and

function of mangrove forest ecosystems. Austr. J. Ecol. 16: 433–443.

Robertson, A. I. and Alongi, D. M. (Eds.) 1992. Tropical Mangrove

Ecosystems. Coastal and Estuarine Studies 41. American Geophysical

Union, Washington, DC, p. 329.

Robertson, A. I. and Blaber, S. J. M. 1992. Plankton, epibenthos and

fish communities. In: Tropical Mangrove Ecosystems. Robertson, A.I.,

Alongi, D.M. (Eds.), American Geophysical Union, Washington DC,

pp. 173–224.

Saenger, P., Hegerl, E. J. and Davie, J. D. S. 1983. Global status of

mangrove ecosystems. The Environmentalist. 3: 1–88.

Saenger, P. and Siddique, N. A. 1993. Land from the sea: the

afforestation program of Bangladesh. Ocean and Coastal Management.

20: 23–39

Schelake, C. L. and Odum, E. P. 1962. Mechanisms for maintaining

high productivity in Georgia estuaries. Proceedings of Gulf Caribb

Fishery Institute. 14: 75-80

Schwamborn, R. and Saint-Paul, U. 1996. Mangroves—forgotten

forests? Nat Resour Dev. 43/44: 13–36

Semesi, A. K. 1998. Mangrove management and utilization in eastern

Africa. Ambio. 27: 620–626

Siddique, N. A., Islam, M. R., Khan, M. A. M. and Shahidulla, M.

1993. Mangrove nurseries in Bangladesh. Mangrove Ecosystem

Occasional, Papers 1. ISME. Okinawa, p. 14

Smith, III., T. J., Boto, K. G., Frusher, S. D. and Giddens, R. L. 1991.

Keystone species and mangrove forest dynamics: the influence of

burrowing by crabs on soil nutrient status and forest productivity.

Estuar. Coast. Shelf Sci. 33: 419–432.

Sousa, W. P., Kennedy, P. G., Mitchell, B. J. 2003. Propagule size

and predispersal damage by insects affect establishment and early

growth of mangrove seedlings. Oecologia. 135: 564–575.

Spalding, M., Blasco, F. and Field, C. 1997. World Mangrove Atlas.

International Society for Mangrove Ecosystems, Okinawa, Japan.

Stevenson, N. J., Lewis, R. R. and Burbridge, P. R. 1999. Disused

shrimp ponds and mangrove rehabilitation. In: An International

Perspective on Wetland Restoration. Streever W (Ed.) Kluwer Academic

Publishers, Dordrecht, The Netherlands, pp. 277-297

Sylla, M., Stein, A. and van Mensvoort, M. E. F. 1996. Spatial variability

of soil actual and potential acidity in the mangrove agroecosystem of

West Africa. Soil Sci. Soc. of Am. J. 60: 219–229

Tam, N. F. Y. and Wong, W. S. 1995. Retention and distribution of

trace metals in mangrove soils receiving waste water. Environmental

Pollution. 94: 283- 291.

Tattar, T. A., Klekowski, E. J. and Stern, A. I. 1994. Dieback and

mortality in red mangrove, Rhizophora mangle L., in Southwest.

Puerto Rico. Arboricultural Journal. 18: 419-429.

Teas, H. J. 1977. Ecology and restoration of mangrove shorelines in

Florida. Environmental Conservation. 4: 51–58

Thom, B. G. 1967. Mangrove ecology and deltaic geomorphology:

Tabasco, Mexico. Journal of Ecology. 55: 301–343

Twilley, R. R. and Chen, R. 1998. A water budget and hydrology

model of a basin mangrove forest in Rookery Bay, Florida. Marine

and Freshwater Research. 49: 309–323.

Ukpong, I. E. 1995. An ordination study of mangrove swamp

communities in West Africa. Vegetatio. 116: 147-159.

Walter. 1961. The adaptations of plant saline soils. Arid zones,

Proc.Teheran symp. UNESCO Publ.14:129-134.

Wang, L. and Sousa, W. 2009. Distinguishing mangrove species with

laboratory measurements of hyperspectral leaf reflectance. Int. J.

Remote Sens. 30:1267–1281

Watson, J. G. 1928. Mangrove Forests of the Malay Peninsula. Malayan

Forest Records No. 6, Forest Department, Federated Malay States,

Kuala Lumpur, p.275.

Wolanski, E. 1992. Hydrodynamics of tropical coastal marine systems.

In: Pollution in Tropical Aquatic Systems. Connell D, Hawker D (eds)

CRC Press, Boca Raton, Florida, USA, pp. 3-27.

Wolanski, E., Gibbs, R.J., Mazda, Y., Mehta, A. and King, B. 1992.

The role of turbulence in the settling of mud flocs. J. Coast. Res. 8(1):

35-46.

Wolanski, E. 1995. Transport of sediment in mangrove swamps.

Hydrobiologia. 295: 31-42.

Wolanski, E., Spagnol, S. and Ayukai, T., 1998. Field and model

studies of the fate of particulate carbon in mangrove-fringed

Hinchinbrook Channel, Australia. Mangroves and Salt Marshes. 2:

205-221.

Wolanski, E. 2006. The application of ecohydrology for sustainable

development and management of mangrove-dominated estuaries. The

ICEMAN 2006 Mangrove Conference in Kuala Lumpur.

Wong, Y. S., Lam, C. Y., Che, S. H., Li, X. R. and Tam, N. F. Y. 1995.

Effect of wastewater discharge on nutrient contamination of mangrove

soil and plants. Hydrobiologia. 295: 243-254.

Woodroffe, C. D. 1992. Mangrove sediments and geomorphology.

In: Robertson, A.I. and Alongi, D.M. American Geophysical Union,

Washington, De, USA, pp. 7 41.

BIODIVERSITY OF COASTAL-MANGROVE ECOSYSTEM

266