|
Mangrove forest is a woody community that can be periodically submerged in seawater of the inter-tidal zone of tropical
and subtropical regions (Lu and Lin 1990). They are the second highest source of primary production next to rainforests. They
produce high detritus and release nutrients which are a food source for variety of organism. Mangroves provide homes to variety
of marine and terrestrial organisms. They act as nurseries and feeding grounds for many fish, shrimp and crustaceans and non-resident
fish enter the mangroves to feed at high tide. Mangroves are also prime nesting and migratory sites for hundreds of bird species.
They not only provide a wealth of biodiversity, but are an essential part of the world’s food web. As with most ecosystems,
an intricate relationship exists between mankind and mangrove. Many indigenous coastal residents rely on mangroves to sustain
their traditional cultures. They have been sustainably used for food production, medicines, fuel wood, fishery, honey and
construction materials. They are important inter-tidal estuarine wetlands along the coastlines of tropical and subtropical
regions; are exposed to anthropogenic contamination from tidal water, river water and land-based sources (Klekowski et al
1994).and Sundarban Mangrove Ecosystem being no exception. The Sundarban Forest is the largest estuarine mangrove forest in the world located in 24 Paraganas
district of West Bengal (India) and Bangladesh. In India, it covers an area of 9630 square kilometers out of which 4266 Km2 is Mangrove forest (Naskar 2000). Due to it's beauty and richness
of wildlife, it was declared a world natural heritage site by UNESCO in 1974 and a national park in 1984.
The Sundarban Mangrove Forests has been home for a wide biodiversity. It is natural habitat of
many endangered species including the Royal Bengal tiger, Estuarine
Crocodile (Crocodilus porosus), Gangetic Dolphin (Platinista gangetica), Snubfin dolphin (Orcella brevirostris),
River Terrapin (Batagur baska), marine turtles like Olive Ridley (Lepidochelys olivacea), Green Sea Turtle (Chelonia mydas),
Hawksbill Turtle (Eritmochelys imbricata), thus making it a natural biodiversity
hot spot.
The entire mangrove forest is called Sundarban owing to the dominance of the tree species Heritiera fomes, locally
known as 'sundari' because of its elegance (Jain and Sastry, 1983). Sundarban flora is characterized by of 26 True Mangrove species and 29 mangrove associates species
have been identified (www.indiansundarban.org). Characteristic mangrove species include garjan (Rhizophora sp.), kankra (Bruguiera
sp.), goran (Ceriops sp)., and baen
(Avicennia officinalis). Heritiera fomes is scattered over areas of higher elevation, along with keora (Sonneratia sp.), gengwa
(Excoecaria sp.) and Xylocarpus sp. The golpata palm Nypha fruticans and mangrove date palm or hental Phoenix paludosa is relatively uncommon but occurs on wet mud-banks along the creeks The Sundarban Mangrove Ecosystem
is the region of transition between the fresh water of the Ganges distributaries system and the saline water of the Bay of
Bengal. The river system of Hugli - Haldi, Muriganga, Saptamukhi, Thakuran, Matla, and Goasaba bring a huge sediment load with which is deposited
at delta. The estuary annually receives 411 X 106 m3 T (i.e., 328 X 106 T sediment +
83 X 106 T solute load) from Hugli river alone. (Sarkara et al, 2004) Therefore the different ecosystem processes are dominated by various factors such as river discharge,
Salinity, freshwater flushing, daily tidal water fluctuations, siltation, sedimentation and lateral erosion. However during
past few years, the natural ecosystem has been disturbed due to anthropogenic activities.
The mangrove ecosystem has suffered from loss of habitat and contamination. Aquaculture, logging of mangrove forest
for timber and fuel wood has caused the decrease in the forest cover area. They have suffered the repercussion of deforestation
for the purpose of artificial pond construction for aquaculture of shrimp farming. A large number of populations are dependent
on forest for fishing, honey collection, wood cutting, and shrimp fry collection. Fishing is second largest occupation after
agriculture. This coastal environment suffers from environmental degradation due to rapid human settlement, tourist activity,
deforestation, and increased agricultural and aquaculture practices. Moreover, the mighty Hugli river has supported multifarious
industries such as paper, chemicals, textiles, pharmaceuticals, shellac, leather, plastic, tires, and cycle rims (UNEP, 1982)
and thus carrying a huge pollution load to the mangrove ecosystem.
The ecology and the biodiversity of the
Sundarban has been extensively studied (Prain.1903; Champion, 1936; Mukherjee, 1975; Jain and
Sastry, 1983; Sanyal, 1983; Naskar 1988; Naskar and Mandal 1999 and Sen and Naskar 2003). Naskar and Guha Bakshi, (1987) studied the mangrove ecosystem with reference to human habitation
and settlement, development of agricultural fields and brackish water fisheries. Somenath Bhattacharyya (2002) explained the
zonation of Mangrove Zonation in Sundarban through remote sensing. Banerjee (1972) in Sen and Naskar (2003); Naskar and Guha Bakshi (1987); and Naskar (2000) had investigated the climatic
variation of the Sundarbans. Sugata Hazra,(2002) has studied the impact of sea level change in Sundarbanwhere as Anjali Mukherjee (2002) studied the impact of Climatic Change on Sundarban
Mangroves The geology of the lower Gangatic plain has been studied by Bhattacharya and Das, 1994; Bhattacharya, 1999; Sanyal,
1999 (in Sen and Naskar 2003). Paul 1999 (in
Sen and Naskar 2003) has described the various land form in the Sundarban mangrove ecosystem. Naskar 2000., Nath and De, 1999(in
Sen and Naskar 2003) studied some
of the important physiochemical parameter in Sundarban (temperature, transparency, DO, pH, Talk CO2 Salinity, Ca, Mg Na K, free NH4 SO4. Phosphate, Nitrate. Silicate etc.). Naskar et al (1999) studied
the chemical characteristics of estuarine water in the three zones. Biswas et al (2004, 2005) has studied the exchange of
CO2 and Ammonia near the land ocean boundary condition of Sundarbans. Subhas
Santra (2002) has carried out study on the air pollution response to plants of mangrove vegetation”. Sarkara et al (2002)
has studied heavy metals concentration from the bioata of the Sundarban mangrove ecosystem. Rita Saha, (2002) assessed the
coastal water pollution in Sundarban mangroves. Guzzella et al
2005 has studied POPs in the lower stretch of river Hugli
|
