Mangrove

Above and below water view at the edge of the mangal

Mangrove are woody trees or shrubs that grow in coastal habitats or mangal (Hogarth, 1999), for which the term mangrove swamp also would apply. Mangrove plants are found in depositional coastal environments where fine sediments, often with high organic content collect in areas protected from high energy wave action.

Mangrove plants are a diverse group which have been able to exploit a habitat (the intertidal zone) because they have developed a set of physiological adaptations to overcome the problems of anoxia, salinity and frequent inundation. Each species has its own capabilities and solutions to these problems and this may be the primary reason why on some shorelines mangrove tree species show distinct zonation as a consequence of variations in the range of environmental conditions across the intertidal zone. The mix of species at any location within the intertidal zone is therefore partly determined by the tolerances of individual species to physical conditions such as tidal inundation and salinity, but also may be influenced by other factors such as predation of their seedlings by crabs.

Once established, the roots of the mangrove plants help to impede water flow and thereby enhance the deposition of sediment in areas where it is already occurring. It is usually the case that 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. In areas of the world where mangroves have been removed for development purposes, the disturbance of these underlying sediments often creates problems of trace metal contamination of seawater and biota.

It is often stated that mangroves provide significant value in the coastal zone as a buffer against erosion, storm surge and tsunamis. While there is some attentuation of wave heights and energy as seawater passes through mangrove stands, it must be recognised that these trees typically inhabit areas of coastline where low wave energies are the norm. Therefore their capacity to ameliorate high energy events like storm surge and tsunamis is limited. Their long term impact on rates of erosion is also likely to be limited. Many river channels that wind through mangrove areas are actively eroding stands of mangroves on the outer sides of all the river bends, just as new stands of mangroves are appearing on the inner sides of these same bends where sediment is accreting.

They also provide habitats for wildlife, including several commercially important species of fish and crustacea and in at least some cases export of carbon fixed in mangroves is important in coastal foodwebs. In Vietnam, Thailand, the Philippines, and India, mangrove plantations are grown in coastal regions for the benefits they provide to coastal fisheries and other uses. Despite replainting programs over 50% of the World's mangroves have been lost.

The mangal is often considered a type of biome. Mangrove habitat is exclusively subtropical and tropical and tidal, and therefore having soil or sediment that is water-logged and saline or of variable salinity. Areas where mangal occurs includes estuaries and marine shorelines. A wide variety of plant species can be found in mangrove habitat, but some 54 species in 20 genera, belonging to 16 families constitute the "true mangroves", species that occur almost exclusively in mangrove habitats and rarely elsewhere (Hogarth, 1999).

The mangrove species, Sonneratia, growing on the landward margin of the reef flat on Yap and showing abundant pneumatophores

Species of mangroves

The following listing (modified from Tomlinson, 1986) gives the number of species of mangroves in each listed plant genus and family.

Major components

Family Acanthaceae (alt. Avicenniaceae, Verbenaceae)

• Avicennia – 9

Family Combretaceae

• Laguncularia – 1
• Lumnitzera – 2

Family Arecaceae

• Nypa – 1

Family Rhizophoraceae

• Bruguiera – 6
• Ceriops – 2
• Kandelia – 1
• Rhizophora – 8

Family Sonneratiaceae

• Sonneratia – 5

Minor components

Family Acanthaceae

• Acanthus – 1
• Bravaisia – 2

Family Bombacaceae

• Camptostemon – 2

Family Cyperaceae

• Fimbristylis – 1

Family Euphorbiaceae

• Excoecaria – 2

Family Lythraceae

• Pemphis – 1

Family Meliaceae

• Xylocarpus – 2

Family Myrsinaceae

• Aegiceras – 2

Family Myrtaceae

• Osbornia – 1

Family Pellicieraceae

• Pelliciera – 1

Family Plumbaginaceae

• Aegialitis – 2

Family Pteridaceae

• Acrostichum – 3

Family Rubiaceae

• Scyphiphora – 1

Family Sterculiaceae

• Heritiera – 3

Mangrove ecoregions

Mangroves in other media

• Because of the mangrove's unique significance as a self-sustaining biome, the mangrove is used as a symbol in Annie Dillard's essay "Sojourner".

References

• Hogarth, Peter J. 1999. The Biology of Mangroves. Oxford Univ. Press. 228 p. ISBN 0198502222
• Thanikaimoni, G. 1986. Mangrove Palynology. UNDP/UNESCO and the French Institute of Pondicherry, 104 p. ISSN 0073-8336 (E).
• Tomlinson, P. B. 1986. The Botany of Mangroves. Cambridge Univ. Press, Cambridge.
• tsunami protection

External links

• The story of the UNESCO Mangrove Programme
• WWF article about the mangrove biome
• East African Mangroves
• Coastal wetland and shoreline change mapping of Pichavaram, south east coast of India using Satellite data
• Status of Indian Mangroves: Pollution Status of Pichavaram Mangrove, Southeast Coast of India
• Mangrove Action Project - Advocacy group devoted conservation, restoration and sustainable management of mangroves & related coastal ecosystems
• Global Mangrove database and Information System (GLOMIS)
• Information and photo of Red Mangrove in aquarium - Rhizophora mangle (Italian)

The content of this page is retrieved from http://en.wikipedia.org/wiki/Mangrove under GFDL