Mangrove Ecosystem – Explained!

Mangroves are a type of coastal, intertidal vegetation or a group of plants that tolerate salinity. In this blog we’ll know what is mangrove, types of mangrove, limiting factors and driving forces of mangrove, organisms associated with mangrove ecosystem, the economic value of mangrove forest, etc.

What is Mangrove?

The term “mangrove” is derived from two Portuguese and English words, viz., “mangue” and “grove,” respectively. In Portuguese, a mangrove tree or bush is referred to as a “mangue,” whereas an English word for a group of trees and shrubs is “grove.” Mangrove plants have unique mechanisms for coping with salt, including salt extrusion, salt exclusion, and salt accumulation. From these unique traits, mangrove species can adapt best in salty environments, in the areas between the high and low tides along the coast, and at the mouths of estuaries.

Mangrove tree

Mangroves are defined as “trees or bushes growing between the level of high water at spring tide and the level close to but above the mean sea level,” according to Mac Nac (1968).

Hamilton and Snedaker (1984) defined “the mangroves are salt-tolerant forest ecosystems of the tropical and sub-tropical intertidal regions of the world.”

Around 70 kinds of mangrove plants have been identified worldwide. The three main species are-

  1. White Mangrove- Laguncularia racemosa, 
  2. Black Mangrove- Avicennia germinans, and
  3. Red Mangrove- Rhizophora mangle

Types of Mangroves:

Several major types of mangrove communities are described based on geological and hydrological processes. Generally, mangroves grow best in depositional environments with low wave energy. Extreme wave conditions prevent the establishment of propagules, destroy relatively shallow root systems, and prevent the accumulation of fine sediments, Primarily, these conditions exist along deltaic coasts or estuarine shorelines.

1. Riverine mangroves:

Riverine mangroves grow along the edges of coastal rivers, often several miles inland from the coast. Flooded by river water as well as by tides, the salinity is moderate. Even though the water table is often just below the soil surface, these mangroves may be dry for a long time. These mangroves are usually very productive because they get enough fresh water and get a lot of nutrients from both upland and estuarine sources. The maximum heights of trees in this community are 66 feet (20 m).

2. Fringing mangroves:

Along protected shorelines and in some canals, rivers, and lagoons, you can find fringe mangroves. They take place at shorelines that are in close proximity to terrain that is higher than usual during high tide but is still subject to daily tides. Although the tides seem to flush these forests every day, they do not receive as much terrestrial runoff as riverine forests. Because of the weak tides and the abundance of prop roots, they frequently get a lot of organic waste. Due to their open locations, fringe mangroves are frequently exposed to storms and high winds, which causes debris to accumulate.

Most of the plants that live in the fringe mangroves have prop roots that block the flow of the tides and spread wave energy when the seas are rough. The consequences of seawater pollution are particularly hard on these mangroves. In this neighborhood, trees can grow to a maximum height of a little over 30 feet (10 m).

3. Basin mangroves:

They occur in inland depressions or basins, often behind fringe mangrove forests and in drainage depressions where water is stagnant or slowly flowing. The ground surface of such forests is often covered by pneumatophores from the dominant trees. Trees in this community have maximum heights of almost 50 feet (15 m).

4. Scrub or Dwarf mangroves:

Scrub or dwarf (small) mangroves exist in low-productive mangrove wetlands that are usually limited in nutrients and freshwater inflows. They are dominated by scattered small (often less than 2 m tall) mangrove trees. Hypersaline conditions and cold at the northern extremes of the mangrove range can also produce scrub or stressed mangrove trees in riverine, fringe, or basin mangroves.

5. Overwashed mangroves:

Overwashed mangroves exist as islands that are frequently washed over by tides. All species are present, with the red mangrove (Rhizophora mangle) as the dominant species. Typically, these islands develop as red mangrove propagule strands in a shallow flat. The maximum height of the community is 25 feet (7 m)

Old-world mangroves, which grow on river and tide sediments, have a more comprehensive structure (Woodroffe 1992). This system distinguishes three extremes based on the dominant physical process:

  • River-dominated (riverine mangrove) 
  • Tide-dominated ( fringe mangrove) and
  • Interior mangrove (basin mangrove).

Limiting factors and driving forces:

A primary factor of the natural environment that affects mangroves over the long term is sea level and its fluctuations. Other shorter-term factors are air temperature, rainfall, day length, the geographic position of the area, storms, and man-made factors. Most mangroves live on muddy soils, but they also grow on sand, peat, and coral rock. If tidal conditions are optimal, mangroves can flourish far inland, along the upper reaches of coastal estuaries.


1. Tidal inundation:

The typical and best mangrove flora require frequent tidal inundation. Mangroves are facultative halophytes which means salt water is not a physical requirement for growth. Most can grow well in freshwater, but mangrove communities are not usually found in strict freshwater environments. Although not a direct physical requirement, tidal fluctuation plays an important indirect role in mangrove distribution.

Tidal fluctuation results in alternating wetting and drying of the coastal soil, transportation of relatively clean water and nutrients, exporting wastes, detritus, and sulfur compounds, and effective dispersal of propagules. Where evaporation is very high, tidal fluctuation washes excess salt away preventing excessively high soil salinity concentrations. Due to the above factors, mangrove systems reach the greatest development around the world in low-lying regions with relatively large tidal fluctuations.

2. Climate, temperature, and rainfall:

The mangrove flora requires a typical tropical climate, with the temperature ranging between 20°C and 35°C along with annual rainfall between 150 mm to 300 mm. High humidity, silt-clay sediment soil, protected shallow sheltered bays and wide beach areas are also needed. The long-armed rivers with wide mouths or estuaries are the ideal sites or potential areas for the healthy growth of the diverse mangrove flora.

Temperature condition controls the limit of spreading the mangroves, while rainfall determines the sequence of mangrove zones in the tidal region. Among these climatic factors, the atmospheric and water temperature, atmospheric humidity, seasonal monsoon precipitation, wind velocity, solar radiation or day length, the average number of rainy days/annum, and the volume of upstream freshwater supply are the other important and dominating factors for better growth and development of the mangroves. It has been observed that the mangroves develop best in the tropical estuaries and occasionally in the subtropical wetlands and grow very rarely in the subtropical dry zones.

3. Geographic position:

The tropical estuaries receive heavy rainfall, which is evenly distributed throughout the year. This is preferable for the effective growth and development of mangroves. Aridity may act as the limiting factor for the effective growth, regeneration, and development of mangroves. Besides the climatic factors, the wide estuarine mouths with the yearlong upstream flow and silted-up delta lands-dominated bays or areas in the tropical and sub-tropical zones are the ideal site for the natural growth and regeneration of mangroves.

4. Storms and natural calamities:

Besides the above-mentioned factors, mangrove areas are prone to cyclones, storms, and floods. These natural calamities often cause extensive damage to the mangrove ecosystem and hence act as a limiting factor for mangrove forests

The mangroves are often affected by disease and pest problems. For example, Avicennia and Sonneratia are infected by the black rust, especially at their basal trunks; seedlings of Rhizophora apiculata are damaged by crabs. Avicennia is found defoliated and even killed by lepidopterous larvae. Bruguiera parviflora is damaged at their basal trunks by the larvae of cerambycid beetles and, Rhizophora mucronata shows browning by a fungus.

5. Man-made factors:

Man-made factors are mostly in the reclamation of mangrove lands for agriculture and prawn culture practices, tree cutting for firewood, house and boat constructions, and developmental activities such as the establishment of fertilizer factories nearer to the mangroves. There is an over-exploitation of fishery resources, especially for the seeds of the tiger prawns. Some gastropods and bivalves species are exploited for lime preparation from the mangrove forest areas, which also affects mangrove ecosystems.

The mangroves are excellent feed for cattle. The buffaloes, goats, and cows are left among mangroves during the summer months and they graze Avicennia leaves and other grasses in the mangrove forests. Local people also collect mangrove leaves to feed their castles. It is believed that the buffaloes when fed with Avicennia leaves produce more milk. This also affects the mangrove trees.

Organisms associated with mangrove

The aerial roots of mangroves help to keep this environment stable and provide a base for many plant and animal species to live on. Above the water, the mangrove trees and canopy provide important habitats for a wide range of species. These include birds, insects, mammals, and reptiles. Under the water, tunicates, sponges, algae, and bivalves grow on the roots of mangrove trees. The soft ground beneath the mangroves is home to many species of infauna and epifauna, while the space between the roots is home and food for animals that can move, like prawns, crabs, and fish.

Mangrove Ecosystem

Mangrove litter is transformed into detritus, which partly supports the mangrove food web. Plankton, algae that grow on plants, and micro-phytobenthos are also important parts of the food web in mangroves. Due to the high abundance of food and shelter, and low predation pressure, mangroves form an ideal habitat for a variety of animal species, during part or all of their life cycles. As such, mangroves may function as nursery habitats for commercially important crab, prawn, and fish species, and support offshore fish populations and fisheries.

Most of the species found in the mangrove ecosystem belong to the Animal Kingdom, followed by species from the Plant Kingdom. Among the most common animals are crustaceans, insects, arachnids, mollusks, fish, and birds. The plants that are found in the mangrove ecosystem are algae, monocotyledons (one seedling leaf) dicotyledons (two seedling leaves). lichens, briophites, and ferns.

Mangrove forests rich in different animals are from the soil, but most of them are from the sea. Among the terrestrials, the most notable are bats and insects. Among the marine animals, crabs and mollusks live permanently in the forest. Langoustines (crayfish) and fish come with the tide from the sea to feed on the mangrove soil, rich in nutrients.

The mangrove swamp is a route from sea to the soil, where the most primitive pulmonated snails, terrestrial crabs, and some fish species come in. It is also a route from seawater to freshwater as indicates some nereid snails and from freshwater to the sea, as indicates the invasion of some aquatic insect larvae.

Saltwater crocodiles are one of the most infamous inhabitants of mangrove areas. They do not generally nest in mangroves but are found nesting in vegetation fringing mangrove areas and vegetation where rivers adjoin coastal flood plains. On the rising tide, these reptiles come into the mangroves to feed. Juvenile crocodiles feed on crabs, prawns, mudskippers, and other small fish. As they mature their diet changes to include large mud crabs, birds, and mammals.

Sea snakes are common visitors to mangrove forests as are terrestrial snakes. Pythons tend to be occasional visitors to the mangroves, while the little file snake, the mangrove snake, and the white-bellied mangrove snake tend to use the mangroves as their primary habitat. The Mangrove monitor and the rusty monitor, which feed on insects, fish, crabs, and sometimes birds, also use the mangroves as their primary habitat.

Mudskippers are one of the few animals which are restricted to mangrove environments. They burrow into the soil and can swim like fish, but, using their pectoral fins, can also climb tree roots and move across the soil. In contrast, most other fish species which inhabit mangrove creeks are also found in the coastal seas, entering the mangroves during a particular stage of their life cycle. For example, barramundi spawns and spend their juvenile phase in mangrove creeks.

Sea mullets also inhabit the mangroves as juveniles. The availability of food and protection from predation are important factors influencing fish migration into, and out of, mangrove environments.

Crustaceans (sea lice, barnacles, shrimp, prawns, and crabs) are abundant in mangrove forests. One of the most distinctive crustaceans is the mud lobster which builds large mud towers at the entrance to its burrow. Pistol shrimp and post-larvae of black tiger shrimp are also available in mangrove forests.

There are also around 60 species of crabs that inhabit the mangroves. Some crabs are predominantly leaf eaters while others feed mainly on algae and detritus on the soil surface, scooping the material into their mouthparts and discarding the inedible material as round pellets. Mollusecs, like the common mud whelk and the mangrove oyster, are often visible on the muddy soil around the base of mangrove trees.

Many species of birds also depend seasonally on mangrove environments for food and shelter. Honeyeaters and lorikeets visit the mangroves for nectar during the plant flowering season. Other species, such as the torsion imperial pigeon, inhabit the mangroves during breeding.

Mangroves are important habitats during migrations and can become important refuges during droughts and when the adjacent terrestrial forest is destroyed. Water birds that visit the mangroves on a more regular basis include the Jabiru, egrets, and the Mangrove Heron while the mangrove robin, white-breasted whistler, mangrove honeyeater, and mangrove kingfisher are woodland birds that are considered mangrove specialists.

Flying foxes (fruit bats) often form large colonies in the mangroves and can be seen roosting during the day. Other mammals are not often seen in mangroves, however, wallabies, rats, possums, and bandicoots visit the mangroves, as do feral pigs, cattle, and water buffalo.

The mangrove forests are like a natural wildlife sanctuary. A variety of marine animals, including snails, land crabs, and fiddler crabs, scavenge for food at low tide. Raccoons (carnivorous animals) search for crabs among the mangrove roots in the evenings. When the tide is in the crown conch (large sea snails) prey on oysters and fish such as the mangrove snapper feed on the smaller fish and invertebrates swim among the roots. Brown pelican and other mangrove birds build their nests in the leafy trees which hunt and scavenge on the abundant marine life.

The economic value of Mangrove forest

Economic importance of mangrove forests:  Mangrove forests have been widely and variously used by the people who live in or close to them and who traditionally have made a living from the mangrove ecosystem for thousands of years. People have depended on mangrove trees for many purposes. The mangrove ecosystem offers numerous wood and non-wood forest products (NWFP) for the local communities. The economic importance of mangroves can be summarized as follows:

A. Utilization of wood products

Direct mangrove forest extraction is not good at all for the environment. But it will be traditional and potential utilization for many purposes which are discussed as follows:

1. Fuel wood: Mangrove wood was preferred as fuel wood because of its high calorific value. The calorific value of various species normally ranges between 4700 to 5300 cal/kg. The coastal communities in India used most of the mangrove species as fuelwood. Mangrove species belonging to the genus Rhizophora, Ceriops, Sonneratia, Avicennia, and Bruguiera are popularly used as firewood in many countries. Fishermen in the islands used Avicennia marina wood for fish smoking as it burns with little smoke. 

2. Food: Avicennia marina, Bruguiera parviflora, Rhizophora apiculata, and Acrostichum aureum are used as food for cows, buffaloes, and goats in many countries in the world. 

3. Timber: Generally, mangrove woods are not very important as timber. Rhizophora Bruguiera, Sonneratia species are not used as timber as they split and warp when dried. Most of the mangrove woods have high density, which makes it difficult to work. However, Avicennia species that have relatively lesser density were used as timber for the construction of houses and carpentry items.

4. Charcoal: Wood density largely determines the yield of charcoal from wood, therefore, Rhizophora species were the most preferred ones for the manufacture of charcoal. Other species used for the manufacture of charcoal belong to the genus Bruguiera, Sanneraria, and Ceriops.

5. Poles: Poles of Sonneratia caseolaris and other mangrove trees are widely used for house construction and to support tidal fish nets.

6. Thatching material and sugary syrup: These products can be obtained from Nypa fruticans. Fronds of the plant are used by local communities of Andaman for making thatching material for rural houses. Nypa cultivation can produce 16,000 species of thatching leaf/ha/year (Vannucci, 1989). A sugary sap can also be extracted from the Nyp which can be used as sweetening syrup or for the manufacture of alcohol and vinegar. A plantation with 250 Nypa/ha can yield 50,000 liters of sap/year.

7. Construction material for a hut, fencing, and walkway: In Andaman, stems of Phoenix paludosa is used as construction material for the hut, fencing, and walkway in mangrove nursery/marshy lands. 

8. Tannin: Fresh and moist barks of mangrove species are potential sources for commercial extraction of tannin. Rhizophora species are most preferred as they yield very high-quality tannin. Other species, which can be used as the source of tannin, are Bruguiero gymnorrhiza, B. parviflora, B. cylindrica, Ceriops tagal, Kandella candle, Sonneratia caseolaris, S. alba. Xylocarpus granatum, X. mekongensis, and X. moluccensis. Traditionally, fishermen were using nets made of natural fibers. They used to cure and dye the nets with mangrove tannin to make them resistant to biological decay.

9. Development of driftwood and carpentry industry: Today, there is a big demand for show- pieces made from driftwood and other small wood derived from the forests. These items obtain very high prices in the national and international markets. Realizing the importance, industries have already started professional training for the local people in this trade in different countries. 

10. Pulp and paper: Excoecaria agallocha, Sonneratia caseolaris, and Avicennia marina are used in the pulp and paper industries.

B. Utilization of non-wood forest products (NWFPs)

The mangrove ecosystem is the potential source of numerous NWFPs. If the resource is managed sustainably, it can bring about the fast development of local communities. 

1. Capture fishery: Mangrove forests are the excellent breeding and resting ground for varieties of fishes, prawns, crabs, etc. Decomposed mangrove leaves act as nutritious food for these aquatic animals. Rhizophora has a characteristic root system, which entraps sediments, animal, and plant material. Local fishermen in the coastal areas earn their livelihood by catching fish, prawns, and crabs from the mangrove forests using nets and by other traditional methods. The mangrove is nature’s aquaculture system with several advantages.

2. Culture fishery: Although aquaculture can be practiced in all aquatic systems but mangrove areas are mostly preferred for this purpose. The availability of fish and prawn seeds in the natural waters is a critical factor in the development of cultural fisheries. There are many types of aquaculture like oyster culture, crab culture, and fin fish culture which can be practiced in mangrove areas without destroying or degrading them. Development of fishpond must be carried out towards the landward fringes of mangrove swamps.

3. Crocodile farming: It is widely practiced in mangrove areas of Cambodia and Cuba. Although the average life span of a crocodile is 80 years. Crocodiles require little space and care to rear. It has a low mortality rate and can be fed with cheap varieties of fish. Successful crocodile rearing can bring radical changes in the socio-economic status of the people, however, it requires specialized training. Necessary clearance from the wildlife authorities must be obtained before venturing into the business.

4. Sea-weed culture: China, Hong Kong, Vietnam, Philippines, Taiwan, Japan, and Korea are the Asian countries that consume large quantities of seaweeds as food and also for medicine and cosmetic purposes (FAO, 1994). Farming Gracilaria (a seaweed) can bring a net income of US $2720/ha/year (Christensen, 1983). These sea-weeds farming can be designed in the mangrove ecosystem.

5. Wax and honey: In the mangrove forests, honeybee nests are common and yield wax and honey. Honeybees prefer the species Excoecaria,  Avicennia, and Aegiceras for nectar collection. In the Sunderban mangrove forests of Bangladesh, honey is collected on a commercial basis, and sustainable revenue is earned from this sector. To tap the potential, apiculture can be developed in mangrove forests. Apiculture is an eco-friendly activity, that provides local people, including women, with food and self-employment opportunities.

 6. Food: Local people including aboriginal tribes in Andaman and Nicobar Island eat the kernel of Nupa and Heritiera fruits. Fruits of Phoenix paludosa are relished by children. Young shoots of Acrostichum aureum are used as vegetables. Propagules of Bruguiera parviflora and Bruguiera cylindrica are eaten by the Jarwa tribe of Andaman.

7. Medicines: In the Andaman Islands, the decoction of shoots of Ceriops tagal is used in the treatment of malaria. Decoction of seeds of Heritiera littoralis is used in diarrhea and dysentery. Berks of Xylocarpus granatum and Xylocarpus moluccensis are used in the treatment of dysentery.

8. Agriculture in Mangrove Areas: At best, reclaimed mangrove areas can be considered marginal agricultural lands. Soils in mangrove areas are highly saline and potentially acid sulfate. Because of these two properties of the mangrove soils, they can be used for raising a limited variety of crops and that too under intensive soil management. In mangrove areas, one must ensure an adequate supply of water to maintain the water table above the sulfide layer in the soil. This will prevent the oxidation of sulfides present in mangrove soil, which may otherwise result in the formation of acid-sulfate soils. Mangrove soil can be used for raising the following shallow-rooted crops:

  • Paddy cultivation: Some paddy crops especially salt-tolerant varieties are cultivated in mangrove areas in different countries.
  • Coconut plantation: As the coconut is a salt-tolerant plant, it is most preferred for planting on reclaimed mangrove areas. It is a successful crop in Andaman and Nicobar Islands.
  • Cultivation of oil palm:  Oil palm plantations in Malaysia have been established by adopting appropriate management practices. They yield almost the same as compared to the plantation on normal soil. A proper water control system should be adopted to prevent the formation of acid-sulfate soil. The addition of lime to the soil can further improve productivity.

9. Coastal Agroforestry: Agroforestry is a system for multiple uses of land simultaneously. It generally involves the planting of crops and forestry trees and shrubs on the same land. However, in a broader sense, agroforestry also includes animal husbandry and fisheries, which can be introduced depending on the suitable ecological conditions present in a particular area. Putting these models into action in mangrove areas can help the local people make more money and improve the health of the ecosystem as a whole.

10. Salt production: Hypersaline mangrove areas can be developed for the establishment of salt pins for salt production. This can be an additional source of income for the local people. Solar salt production is a traditional and important industry in many coastal dry and semi-dry regions

11. Development of eco-tourism: A mangrove forest is a beautiful environment. It acts as a sightseeing route for eco-tours, and it brings financial incentives to the community. Mangroves are the habitat for a variety of reptiles, birds, and aquatic animals. Crocodiles and snakes are commonly seen in mangrove areas. Various hinds tab as Egrets, Stock Kingfishers, Bramhany kites, Bramhany ducks, Grey herons, Seagulls, fishing eagles, Sandpipers, Pintales River twins, and Coots are seen in mangrove forests.

The development of eco-tourism can be solved the unemployment problem. If proper facilities are provided a large number of tourists would like to enjoy the floral and faunal beauty of the mangrove ecosystem. Even this will lead to an inflow of more and more tourists and spread awareness about the mangroves. Activities that can be promoted in mangrove areas are nature trails, bird watching, nature photography, and crocodile farms. fishing, canoeing and botanical studies, etc.

The mangrove ecosystem is one of the most productive coastal ecosystems of the world and has played a crucial role in the development of local communities since time immemorial. It plays an important role in the lives of the people who live in or near it, and also in the economy of the country as a whole.

The mangrove forest of Bangladesh

Bangladesh has two types of mangrove forests: natural mangroves and planted mangrove forests.

Mangrove forest

Natural mangrove forest

We have two natural mangrove forests. The Sunderbans Forest Reserve represents the biggest stand of mangroves in Bangladesh, and it is located in the southeastern part of the delta region around Khulna. Other important mangrove forests are the Chakaria Sundarbans, located in the district of Cox’s Bazar, in the southeast part of the country. Along the banks and estuarine islands of the Naaf river, there is a small strip (1800 ha) of E. agallocha and Ceriops spec. mangroves.

Planted forest

The coastal afforestation program in Bangladesh was started in 1966. Up to 1996, the program was funded by the World Bank and the Government of Bangladesh and a total of 765 km2 of plantations were established (Revilla et al. 1998). Planted species are mainly Sonneratia apetala and Avicenna officinalis. Others are Excoecaria agallocha, Bruguiera gymnorhiza) and Nypa fruticans. The primary objective of developing mangrove plantations was to mitigate the disastrous effects of cyclones and storm surges, with which some other objectives were added later:

  • Production of timber for fuel wood and industrial uses:
  • Supply of urgently needed resources into the national economy:
  • Creation of employment opportunities for remote rural communities: 
  • Development of a suitable environment for wildlife, fish, and other estuarine and marine fauna

Sundarbans Mangrove Forest

The Sundarbans is the largest single block of tidal halophytic mangrove forest in the world. The name Sundarban can be translated as “beautiful jungle” or “beautiful forest” in the Bengali language (Sundar, “beautiful” and ban. “forest” or “jungle”). The name may have been

derived from the Sundari trees that are found in Sundarbans in large numbers. Alternatively, it has been proposed that the name is a corruption of Samudraban

Location: The forest lies in the vast delta on the Bay of Bengal formed by the confluence of the Ganges. Brahmaputra and Meghna rivers across southern Bangladesh (Khulna, Bagerhat, and Satkhira district) and West Bengal, India. It occupies the area between longitudes 89°00’E & 89°55′ and latitudes 21°30’N & 22°30’N. 

Forest boundaries: North-Bagerhat. Khulna and Sathkira districts.

The forest covers 10,000 square kilometers, approximately 6.000 square kilometers (2400 square miles) of which are in Bangladesh. 

Location Total area in haForested areaWater areaDeforested area

A list of famous places in Sundarban:

  • Hiron Point (Nilkamal) for tiger, deer, monkey, crocodiles, birds, and natural beauty.
  • Katka for deer, tiger, crocodiles, varieties of birds and monkeys, morning and evening symphony of wild fowls. The vast expanse of grassy meadows running from Katka to Kachikhali (Tiger Point) provides opportunities for wild tracking.
  • Tin Kona Island for tigers and deer.
  • Dublar Char (Island) for fishermen. It is a beautiful island where herds of spotted deer are often seen grazing.

Sundarbans environment:

This mangrove forest is characterized by

  • An interconnected network of rivers, canals, and creeks.
  • Complex salinity pattern.
  • Hydrology is regulated by high local rainfall and tidal inundation.
  • Soils of this delta are slightly calcareous, alkaline, clayey mud with low organic matter content (Hassan 1982).

Some important environmental aspects of Sundarbans 

FactorsKey charactersDescription
Rainfall West-1600 and East-200 mm mean annual rainfall80-85% during the monsoon season
Temperature24-340 c12-250 cMarch to JuneDecember to January
TidesSemi diurnal period-12 hours,25 minutesMean tidal hight-4 cmGreatest tidal level from June to AugustLowest tidal level in February
Water salinityOligohaline (0-5ppt)Mesohaline (5-18 ppt) Polyhaline ( > 18ppt)Southeastern part Middle northern partWestern part
Water pH6.5-8No marked seasonal variation
HumidityMean annual humidity 70% to 80%High-June to OctoberLow- February

Ecological Zonation:

Salinity, water tolerance, and specific threshold govern the distribution of mangrove species. Generally, it is considered that forests in the northern and eastern parts are better supplied with fresh water and floristically richer than the South and west. Based on species composition and salinity SRF have been classified into zones by Curtis 1933.

  1. Freshwater zone: Northern and central parts of the Sundarbans are dominated by the Sundri tree- also comprises of passur and kankra. Common fish species are Pangasius pangasius, Tenulosa ilisha, Lates calcarifer, and Macrobrachium rosenbergii (Prawn).
  1. Moderately saltwater zone: A mixture of gewa and sundori with varying amounts of goran is available in this zone. Fish species commonly found in this zone are Penaeus monodon, Tenulosa ilisha, Lates calcarifer, and Polynemus spp. Metapenus monoceros and Scylla serrata. 
  1.  Saltwater Zone: Western part of Sundarbans is dominated by the gewa, passur, and dhundal trees. Some fish species are commonly found in this zone. Harpadon neherus,  Trichiurus haumela, Pampus argenteus, Sardinalla spp., Panaeus monodon etc. and also shark, rays.

List of white fish species in the Sundarbans

Species NameScientific Name
Ilish Tenulosa ilisha
KamilaCongresox talabonides
Kata Arius arius
LiottaHarpodon nehereus
Mur bailaPlatycephalus indicus
Vetki Lates calcarifer
BarguniTherapon jarbua
TulardandiSillago domina
Poa Panna microdon
LakhuaPolynemus inducus
ChuriTruchiorus leptures
Folichanda Pampus argentina
Rupchanda Pampus chinensis
Parse Liza parsia
Fatra Raconda russeliana
Taposi Polynemus indicus
Nailla Dussumiera acuta
KhoiraSaradinella gibbosa
Moduphasa Setipinna pasha

Some common flora of Sunderbans:

Species name Scientific name
Sundari treeHeritiera fomes
Golpati Nypa fruticans
Keora Sonneretia apelata
Garjan Rhizophoroa apiculata
Dhundul Xylocarpus granatum
Hatal Phoenix paludosa
Figure: Map of the Bangladesh coast showing mangroves. Image credit: ResearchGate

Leave a Comment