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A mangrove is a
shrub A shrub (often called a bush) is a small- to medium-sized perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the p ...

shrub
or tree that grows in coastal saline or
brackish water Brackish water, also sometimes termed brack water, is water occurring in a natural environment having more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) with fresh water together, as in est ...
. The term is also used for tropical coastal vegetation consisting of such species. Mangroves occur worldwide in the
tropics The tropics are the region of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% i ...

tropics
and
subtropics The subtropical zones or subtropics are geographical Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country locat ...

subtropics
and even some
temperate In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use ...
coastal areas, mainly between latitudes 30° N and 30° S, with the greatest mangrove area within 5° of the
equator The Equator is a , about in circumference, that divides into the and hemispheres. It is an located at 0 degrees , halfway between the and poles. In , as applied in , the equator of a rotating (such as a ) is the parallel (circle of l ...

equator
. Mangrove plant families first appeared during the
Late Cretaceous The Late Cretaceous (100.5–66 Year#SI prefix multipliers, Ma) is the younger of two epoch (geology), epochs into which the Cretaceous geological period, Period is divided in the geologic time scale. Stratum, Rock strata from this epoch form the ...
to
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Er ...
epochs, and became widely distributed in part due to the movement of tectonic plates. The oldest known fossils of mangrove palm date to 75 million years ago. Mangroves are salt-tolerant trees, also called
halophyte Image:Spartina alterniflora.jpg, 250px, ''Spartina alterniflora'' (cordgrass), a halophyte. A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spr ...
s, and are adapted to live in harsh coastal conditions. They contain a complex salt filtration system and a complex root system to cope with saltwater immersion and wave action. They are adapted to the low-oxygen conditions of waterlogged mud, but are most likely to thrive in the upper half of the
intertidal zone The intertidal zone, also known as the foreshore or seashore, is the area above water level Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified ve ...
. The mangrove
biome A biome is a collection of flora, plants and fauna, animals that have common characteristics for the natural environment, environment they exist in. They can be found over a range of continents. Biomes are distinct biological community (ecology ...
, often called the
mangrove forest Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangrove trees cannot withstand ...

mangrove forest
or mangal, is a distinct saline
woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see d ...

woodland
or
shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community A plant community is a collection or Association (ecology), association of plant species within a designated geographical unit, which forms a relatively uniform patch, distinguishab ...

shrubland
habitat characterized by depositional coastal environments, where fine sediments (often with high organic content) collect in areas protected from high-energy wave action. The saline conditions tolerated by various mangrove species range from brackish water, through pure seawater (3 to 4% salinity), to water concentrated by evaporation to over twice the salinity of ocean seawater (up to 9% salinity). Beginning in 2010 remote sensing technologies and global data have been used to assess areas, conditions and deforestation rates of mangroves around the world. In 2018, the Global Mangrove Watch Initiative released a new global baseline which estimates the total mangrove forest area of the world as of 2010 at , spanning 118 countries and territories. Mangrove loss continues due to human activity, with a global annual deforestation rate estimated at 0.16%, and per-country rates as high as 0.70%. Degradation in quality of remaining mangroves is also an important concern. There is interest in
mangrove restorationMangrove restoration is the regeneration of mangrove forest Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and sub ...
for several reasons. Mangroves support sustainable coastal and marine ecosystems. They protect nearby areas from
tsunamis A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquake An earthquake (also known as a quake, tre ...
and extreme weather events. Mangrove forests are also effective at
carbon sequestration Carbon sequestration or carbon dioxide removal (CDR) is the long-term removal, capture or sequestration of atmospheric carbon dioxide, carbon dioxide from the atmosphere to slow or reverse atmospheric CO2 pollution and to Climate change mitigat ...

carbon sequestration
and storage and impede
climate change Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...
. The success of mangrove restoration may depend heavily on engagement with local stakeholders, and on careful assessment to ensure that growing conditions will be suitable for the species chosen.


Etymology

Etymology of the English term ''
mangrove A mangrove is a shrub A shrub (often called a bush) is a small- to medium-sized perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is oft ...

mangrove
'' can only be speculative and is disputed. The term may have come to English from the Portuguese ' or the Spanish '. Farther back, it may be traced to South America and
Cariban The Cariban languages are a Language family, family of languages indigenous to northeastern South America. They are widespread across northernmost South America, from the mouth of the Amazon River to the Colombian Andes, and they are also spoken ...

Cariban
and
Arawakan languages Arawakan (''Arahuacan, Maipuran Arawakan, "mainstream" Arawakan, Arawakan proper''), also known as Maipurean (also ''Maipuran, Maipureano, Maipúre''), is a language family that developed among ancient indigenous peoples in South America. Branche ...
such as
Taíno The Taíno were an indigenous people of the Caribbean. At the time of European contact in the late fifteenth century, they were the principal inhabitants of most of Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cub ...
. Other possibilities include the
Malay language Malay (; ms, bahasa Melayu, links=no, JawiJawi may refer to: People and languages *Australia: **Jawi dialect, a nearly extinct Australian aboriginal language **Jawi people, an Australian Aboriginal people of the Kimberley coast of Weste ...
and the
Guarani language Guaraní (), specifically the primary variety known as Paraguayan Guarani ( "the people's language"), is a South American South America is a continent A continent is one of several large landmasses. Generally identified ...
. The English usage may reflect a corruption via
folk etymology Folk etymology (also known as popular etymology, analogical reformation, reanalysis, morphological reanalysis or etymological reinterpretation) is a change in a word or phrase resulting from the replacement of an unfamiliar form by a more familia ...
of the words ''mangrow'' and ''
grove Grove may refer to: * Grove (nature), a small group of trees Places England *Grove, Buckinghamshire, a village *Grove, Dorset *Grove, Herefordshire *Grove, Kent *Grove, Nottinghamshire, a village *Grove, Oxfordshire, a village and civil paris ...
''. The word "mangrove" is used in at least three senses: * most broadly to refer to the habitat and entire plant assemblage or ''mangal'',Hogarth, Peter J. (1999) ''The Biology of Mangroves'' Oxford University Press, Oxford, England, . for which the terms ''mangrove forest
biome A biome is a collection of flora, plants and fauna, animals that have common characteristics for the natural environment, environment they exist in. They can be found over a range of continents. Biomes are distinct biological community (ecology ...
'' and ''mangrove swamp'' are also used; * to refer to all trees and large shrubs in a mangrove
swamp A swamp is a forested wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes pre ...

swamp
; and * narrowly to refer only to mangrove trees of the genus ''
Rhizophora ''Rhizophora'' is a genus of tropical mangrove trees, sometimes collectively called true mangroves. The most notable species is the red mangrove (''Rhizophora mangle'') but some other species and a few natural hybrid (biology), hybrids are known. ...
'' of the
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...
Rhizophoraceae The Rhizophoraceae is a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typica ...
. File:Mangrove roots at low tide.jpg, Mangrove roots at low tide in the Philippines File:Mangroves in Kannur, India.jpg, Mangroves are adapted to saline conditions


Biology

Of the recognized 110 mangrove species, only about 54 species in 20 genera from 16
families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of families is to maintain the w ...
constitute the "true mangroves", species that occur almost exclusively in mangrove habitats. Demonstrating
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eit ...
, many of these species found similar solutions to the tropical conditions of variable salinity, tidal range (inundation),
anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: *Adhesive#Anaerobic, Anaerobic ad ...
soils, and intense sunlight. Plant biodiversity is generally low in a given mangrove. The greatest biodiversity of mangroves occurs in
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern subregion of Asia, consisting of the regions ...

Southeast Asia
, particularly in the
Indonesian archipelago The islands of Indonesia, also known as the Indonesian Archipelago or Nusantara ''Nusantara'' is the Indonesian name of Maritime Southeast Asia (or parts of it). It is an Old Javanese Kawi or Old Javanese is the oldest attested phase ...
.


Adaptations to low oxygen

The red mangrove (''
Rhizophora mangle ''Rhizophora mangle'', the red mangrove, is distributed in Estuary, estuarine ecosystems throughout the tropics. Its Vivipary, viviparous "seeds", in actuality called propagules, become fully mature plants before dropping off the parent tree. The ...

Rhizophora mangle
'') survives in the most inundated areas, props itself above the water level with stilt or prop roots and then absorbs air through
lenticel bark are the lenticels. A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm Bark is the outermost layers of Plant stem, stems and roots of woody plants. Plants with bark include trees, woody vines ...

lenticel
s in its bark. The black mangrove (''
Avicennia germinans ''Avicennia germinans'', the black mangrove, is a shrub or small tree to 12 meters (39') in the acanthus family, Acanthaceae. It grows in tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude ...

Avicennia germinans
'') lives on higher ground and develops many specialized root-like structures called
pneumatophore '')'s pneumatophorous aerial roots tree of undetermined species in Fort Myers, Florida Fort Myers or Ft. Myers, is the county seat A county seat is an administrative center, seat of government, or capital city of a county or Parish (administrat ...

pneumatophore
s, which stick up out of the soil like straws for breathing. These "breathing tubes" typically reach heights of up to , and in some species, over . The four types of pneumatophores are stilt or prop type, snorkel or peg type, knee type, and ribbon or plank type. Knee and ribbon types may be combined with buttress roots at the base of the tree. The roots also contain wide
aerenchyma alt=Aerenchyma of '' Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma is a spongy tissue that forms spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases ...
to facilitate transport within the plants.


Nutrient uptake

Because the soil is perpetually waterlogged, little free oxygen is available.
Anaerobic bacteria An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenated environme ...

Anaerobic bacteria
liberate
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
gas, soluble ferrum (iron), inorganic
phosphate In chemistry, a phosphate is an anion, salt (chemistry), salt, functional group or ester derived from a phosphoric acids and phosphates, phosphoric acid. It most commonly means orthophosphate, a derivative of phosphoric acid, orthophosphoric a ...

phosphate
s,
sulfide Sulfide (British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and usage a ...

sulfide
s, and
methane Methane (, ) is a chemical compound with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes a ...
, which make the soil much less nutritious. Pneumatophores (
aerial root Aerial roots are roots above the ground. They are almost always adventitiousImportant structures in plant development are buds, shoot In botany, shoots consist of plant stem, stems including their appendages, the leaves and lateral buds, ...

aerial root
s) allow mangroves to absorb gases directly from the atmosphere, and other nutrients such as iron, from the inhospitable soil. Mangroves store gases directly inside the roots, processing them even when the roots are submerged during high tide.


Limiting salt intake

Red mangroves exclude salt by having significantly impermeable roots which are highly suberised (impregnated with
suberin Suberin, cutin and lignins are complex, higher plant Epidermis (botany), epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids ...

suberin
), acting as an ultra-filtration mechanism to exclude
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
salts In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
from the rest of the plant. Analysis of water inside mangroves has shown 90% to 97% of salt has been excluded at the roots. In a frequently cited concept that has become known as the "sacrificial leaf", salt which does accumulate in the shoot (sprout) then concentrates in old leaves, which the plant then sheds. However, recent research suggests the older, yellowing leaves have no more measurable salt content than the other, greener leaves. Red mangroves can also store salt in cell
vacuole A vacuole () is a membrane-bound organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts ...
s. White and grey mangroves can secrete salts directly; they have two salt glands at each leaf base (correlating with their name—they are covered in white salt crystals). File:Pneumatophore overkill - grey mangrove.JPG, aerial roots of the grey mangrove (''
Avicennia marina ''Avicennia marina'', commonly known as grey mangrove or white mangrove, is a species of mangrove A mangrove is a shrub or small tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation cons ...
'') File:Plody mangrovnika (Rhizophora mangle).jpg, Vivipary in ''Rhizophora mangle'' seeds


Limiting water loss

Because of the limited fresh water available in salty intertidal soils, mangroves limit the amount of water they lose through their leaves. They can restrict the opening of their
stomata File:LeafUndersideWithStomata.jpg, The underside of a leaf. In this species (''Tradescantia zebrina'') the guard cells of the stomata are green because they contain chlorophyll while the epidermal cells are chlorophyll-free and contain red pigme ...

stomata
(pores on the leaf surfaces, which exchange
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
gas and water vapor during photosynthesis). They also vary the orientation of their leaves to avoid the harsh midday sun and so reduce evaporation from the leaves. A captive red mangrove grows only if its leaves are misted with fresh water several times a week, simulating frequent tropical rainstorms.


Filtration of seawater

A 2016 study by Kim ''et al.'' investigated the biophysical characteristics of sea water filtration in the roots of the mangrove ''
Rhizophora stylosa ''Rhizophora stylosa'', the spotted mangrove, red mangrove, small stilted mangrove or stilt-root mangrove, is a tree in the family Rhizophoraceae. The specific name (botany), specific epithet ' is from the Latin meaning "stylus form", referring to ...

Rhizophora stylosa
'' from a plant hydrodynamic point of view. ''R. stylosa'' can grow even in saline water and the salt level in its roots is regulated within a certain threshold value through filtration. The root possesses a hierarchical, triple layered pore structure in the
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also calle ...

epidermis
and most Na+ ions are filtered at the first sublayer of the outermost layer. The high blockage of Na+ ions is attributed to the high surface
zeta potential Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface. Zeta potential is a scientific term for Electrokinetic phenomena, electro ...

zeta potential
of the first layer. The second layer, which is composed of macroporous structures, also facilitates Na+ ion filtration. The study provides insights into the mechanism underlying water filtration through
halophyte Image:Spartina alterniflora.jpg, 250px, ''Spartina alterniflora'' (cordgrass), a halophyte. A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spr ...
roots and could serve as a basis for the development of a bio-inspired method of
desalination Desalination is a process that takes away mineral components from saline water Saline water (more commonly known as salt water) is water that contains a high concentration of solvation, dissolved salts (mainly sodium chloride). The salt conce ...
. Uptake of Na+ ions is desirable for halophytes to build up osmotic potential, absorb water and sustain
turgor pressure Turgor pressure is the force within the cell that pushes the plasma membrane cell membrane vs. Prokaryotes A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In b ...
. However, excess Na+ions may work on toxic element. Therefore, halophytes try to adjust salinity delicately between growth and survival strategies. In this point of view, a novel sustainable desalination method can be derived from halophytes, which are in contact with saline water through their roots. Halophytes exclude salt through their roots, secrete the accumulated salt through their aerial parts and sequester salt in
senescent Ann Pouder (8 April 1807 – 10 July 1917) photographed on her 110th birthday. A heavily lined face is common in human senescence. Senescence () or biological aging is the gradual deterioration of Function (biology), functional characteristics. ...
leaves and/or the bark.Tomlinson, P. The botany of mangroves. 16–130(Cambridge University Press, Cambridge, 1986). Mangroves are facultative halophytes and ''
Bruguiera ''Bruguiera'' is a plant genus in the family Rhizophoraceae The Rhizophoraceae are a family (biology), family of tropical or subtropical flowering plants. Among the better-known members are mangrove trees of the genus ''Rhizophora''. Around 147 ...
'' is known for its special ultrafiltration system that can filter approximately 90% of Na+ions from the surrounding seawater through the roots. The species also exhibits a high rate of salt rejection. The water-filtering process in mangrove roots has received considerable attention for several decades. Morphological structures of plants and their functions have been evolved through a long history to survive against harsh environmental conditions.


Increasing survival of offspring

In this harsh environment, mangroves have evolved a special mechanism to help their offspring survive. Mangrove
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
s are buoyant and are therefore suited to water dispersal. Unlike most plants, whose seeds germinate in soil, many mangroves (e.g. ) are
viviparous Among animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aero ...
, meaning their seeds germinate while still attached to the parent tree. Once germinated, the seedling grows either within the fruit (e.g. '' Aegialitis'', ''
Avicennia ''Avicennia'' is a genus of flowering plants currently placed in the Acanthus (plant), bear's breeches family, Acanthaceae. It contains mangrove trees, which occur in the intertidal zones of Estuary, estuarine areas and are characterized by its "p ...
'' and ''
Aegiceras ''Aegiceras '' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to ...
''), or out through the fruit (e.g. ''
Rhizophora ''Rhizophora'' is a genus of tropical mangrove trees, sometimes collectively called true mangroves. The most notable species is the red mangrove (''Rhizophora mangle'') but some other species and a few natural hybrid (biology), hybrids are known. ...
'', '' Ceriops'', ''
Bruguiera ''Bruguiera'' is a plant genus in the family Rhizophoraceae The Rhizophoraceae are a family (biology), family of tropical or subtropical flowering plants. Among the better-known members are mangrove trees of the genus ''Rhizophora''. Around 147 ...
'' and '' Nypa'') to form a
propagule In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
(a ready-to-go seedling) which can produce its own food via
photosynthesis Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...

photosynthesis
. The mature propagule then drops into the water, which can transport it great distances. Propagules can survive desiccation and remain dormant for over a year before arriving in a suitable environment. Once a propagule is ready to root, its density changes so that the elongated shape now floats vertically rather than horizontally. In this position, it is more likely to lodge in the mud and root. If it does not root, it can alter its density and drift again in search of more favorable conditions.


Taxonomy and evolution

The following listings, based on Tomlinson, 2016, give the mangrove species in each listed plant genus and family. Mangrove environments in the Eastern Hemisphere harbor six times as many species of trees and shrubs as do mangroves in the New World. Genetic divergence of mangrove lineages from terrestrial relatives, in combination with fossil evidence, suggests mangrove diversity is limited by evolutionary transition into the stressful marine environment, and the number of mangrove lineages has increased steadily over the Tertiary with little global extinction.


True mangroves


Minor components


Species distribution

Mangroves are a type of tropical vegetation with some outliers established in subtropical latitudes, notably in South Florida and southern Japan, as well as South Africa, New Zealand and Victoria (Australia). These outliers result either from unbroken coastlines and island chains or from reliable supplies of propagules floating on warm ocean currents from rich mangrove regions. "At the limits of distribution, the formation is represented by scrubby, usually monotypic ''Avicennia''-dominated vegetation, as at Westonport Bay and Corner Inlet, Victoria, Australia. The latter locality is the highest latitude (38° 45'S) at which mangroves occur naturally. The mangroves in New Zealand, which extend as far south as 37°, are of the same type; they start as low forest in the northern part of the North Island but become low scrub toward their southern limit. In both instances, the species is referred to as ''Avicennia marina'' var. ''australis'', although genetic comparison is clearly needed. In Western Australia, ''A. marina '' extends as far south as Sunbury (33° 19'S). In the northern hemisphere, scrubby ''Avicennia gerrninans'' in Florida occurs as far north as St. Augustine on the east coast and Cedar Point on the west. There are records of ''A. germinans'' and ''Rhizophora'' mangle for Bermuda, presumably supplied by the Gulf Stream. In southern Japan, ''Kandelia obovata'' occurs to about 31 °N (Tagawa in Hosakawa et al., 1977, but initially referred to as ''K. candel'')."


Mangrove forests

Mangrove forest Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetland A wetland is a distinct ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with ...

Mangrove forest
s, also called ''mangrove swamps'' or ''mangals'', are found in tropical and subtropical areas. Areas where mangroves occur include
estuaries An estuary is a partially enclosed coastal body of brackish water Brackish water, also sometimes termed brack water, is water occurring in a natural environment having more salinity File:IAPSO Standard Seawater.jpg, upInternational Associatio ...

estuaries
and marine shorelines. The
intertidal The intertidal zone, also known as the foreshore or seashore, is the area above water level Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified ve ...
existence to which these trees are adapted represents the major limitation to the number of species able to thrive in their habitat. High tide brings in salt water, and when the tide recedes, solar evaporation of the seawater in the soil leads to further increases in salinity. The return of tide can flush out these soils, bringing them back to salinity levels comparable to that of seawater. At low tide, organisms are also exposed to increases in temperature and reduced moisture before being then cooled and flooded by the tide. Thus, for a plant to survive in this environment, it must tolerate broad ranges of salinity, temperature, and moisture, as well as several other key environmental factors—thus only a select few species make up the mangrove tree community. About 110 species are considered mangroves, in the sense of being trees that grow in such a saline swamp, though only a few are from the mangrove plant genus, ''Rhizophora''. However, a given mangrove swamp typically features only a small number of tree species. It is not uncommon for a mangrove forest in the Caribbean to feature only three or four tree species. For comparison, the tropical rainforest biome contains thousands of tree species, but this is not to say mangrove forests lack diversity. Though the trees themselves are few in species, the ecosystem that these trees create provides a home (habitat) for a great variety of other species, including as many as 174 species of marine
megafauna In terrestrial zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the anatomy, structure, embryology, evolutio ...

megafauna
. Mangrove plants require a number of physiological adaptations to overcome the problems of low environmental oxygen levels, high
salinity Salinity () is the saltiness or amount of salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific ...

salinity
, and frequent
tidal flooding Tidal flooding, also known as sunny day flooding or nuisance flooding, is the temporary inundation of low-lying areas, especially streets, during exceptionally high tide events, such as at Full moon, full and new moons. The highest tides of the y ...
. Each species has its own solutions to these problems; this may be the primary reason why, on some shorelines, mangrove tree species show distinct zonation. Small environmental variations within a mangal may lead to greatly differing methods for coping with the environment. Therefore, the mix of species is partly determined by the tolerances of individual species to physical conditions, such as tidal flooding and salinity, but may also be influenced by other factors, such as crabs preying on plant seedlings. Once established, mangrove roots provide an oyster habitat and slow water flow, thereby enhancing sediment deposition in areas where it is already occurring. The fine,
anoxic The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of disso ...
sediments under mangroves act as sinks for a variety of heavy (trace) metals which colloidal particles in the sediments have concentrated from the water. Mangrove removal disturbs these underlying sediments, often creating problems of trace metal contamination of seawater and organisms of the area. Mangrove swamps protect coastal areas from
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
,
storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood Coastal flooding normally occurs when dry and low-lying land is submerged by seawater. The range of a coastal flooding is a result of the elevation of floodwater that penet ...

storm surge
(especially during
tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation Atmospheric circulation is the large-scale movement of Atmosphere of Earth, air and together with oc ...
s), and
tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquake An earthquake (also known as a quake, t ...

tsunami
s. They limit high-energy wave erosion mainly during events such as storm surges and tsunamis. The mangroves' massive root systems are efficient at dissipating wave energy. Likewise, they slow down tidal water enough so that its sediment is deposited as the tide comes in, leaving all except fine particles when the tide ebbs. In this way, mangroves build their environments. Because of the uniqueness of mangrove ecosystems and the protection against erosion they provide, they are often the object of conservation programs, including national biodiversity action plans. The unique ecosystem found in the intricate mesh of mangrove roots offers a quiet marine habitat for young organisms. In areas where roots are permanently submerged, the organisms they host include
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
,
barnacle A barnacle is a type of arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference ...

barnacle
s,
oyster Oyster is the common name Common may refer to: Places * Common, a townland in County Tyrone, Northern Ireland * Boston Common Boston Common (also known as the Common) is a central public park in downtown Boston, Massachusetts. It is someti ...

oyster
s,
sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the Diploblasts. They are Multicellular organism, multicellular organisms that have bodies full of pores and channels allowing water ...

sponge
s, and bryozoans, which all require a hard surface for anchoring while they filter-feed.
Shrimp Shrimp are Decapoda, decapod crustaceans with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata. More narrow definitions may be restricted to Caridea, to smaller species of either group ...

Shrimp
s and mud lobsters use the muddy bottoms as their home.
Mangrove crab A mangrove is a shrub A shrub (often called a bush) is a small- to medium-sized perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Pl ...

Mangrove crab
s eat the mangrove leaves, adding nutrients to the mangal mud for other bottom feeders. In at least some cases, the export of carbon fixed in mangroves is important in coastal food webs. Mangrove plantations in
Vietnam Vietnam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,, group="n" is a country in Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is the ...

Vietnam
,
Thailand Thailand ( th, ประเทศไทย), historically known as Siam, () officially the Kingdom of Thailand, is a country in Southeast Asia. It is located at the centre of the Mainland Southeast Asia, Indochinese Peninsula, spanning , wi ...

Thailand
,
Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

Philippines
, and
India India, officially the Republic of India (Hindi Hindi (Devanagari: , हिंदी, ISO 15919, ISO: ), or more precisely Modern Standard Hindi (Devanagari: , ISO 15919, ISO: ), is an Indo-Aryan language spoken chiefly in Hindi Belt, ...

India
host several commercially important species of fish and crustaceans. Mangrove forests can decay into
peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation Vegetation is an assemblage of species and the they provide. It is a general term, without specific reference to particular , life forms, structure, ...
deposits because of fungal and bacterial processes as well as by the action of
termite Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

termite
s. It becomes peat in good
geochemical Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the en ...
, sedimentary, and
tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building A mountain is an elevated portion of the Earth's crust, gen ...
conditions. The nature of these deposits depends on the environment and the types of mangroves involved. In
Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico) is a Caribbean island and Unincorporated ...

Puerto Rico
, the
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color ...

red
,
white White is the lightest color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the Unite ...

white
, and
black Black is a color which results from the absence or complete absorption Absorption may refer to: Chemistry and biology *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a rout ...

black
mangroves occupy different ecological niches and have slightly different chemical compositions, so the varies between the species, as well between the different tissues of the plant (e.g., leaf matter versus roots). In Puerto Rico, there is a clear succession of these three trees from the lower elevations, which are dominated by red mangroves, to farther inland with a higher concentration of white mangroves. Mangrove forests are an important part of the cycling and storage of carbon in tropical coastal ecosystems. Knowing this, scientists seek to reconstruct the environment and investigate changes to the coastal ecosystem over thousands of years using sediment cores. However, an additional complication is the imported marine organic matter that also gets deposited in the sediment due to the tidal flushing of mangrove forests. Termites play an important role in the formation of peat from mangrove materials. They process fallen leaf litter, root systems and wood from mangroves into peat to build their nests. Termites stabilise the chemistry of this peat and represent approximately 2% of above ground carbon storage in mangroves. As the nests are buried over time this carbon is stored in the sediment and the carbon cycle continues. Mangroves are an important source of
blue carbon Blue carbon refers to carbon dioxide removed from the atmosphere by the world's ocean The ocean (also the sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the bo ...
. Globally, mangroves stored of carbon in 2012. Two percent of global mangrove carbon was lost between 2000 and 2012, equivalent to a maximum potential of of
CO2 emissions#REDIRECT CO {{rcat shell, {{R from other capitalisation {{R from ambiguous term {{R unprintworthy ...
. Globally, mangroves have been shown to provide measurable economic protections to coastal communities affected by tropical storms.


Mangrove microbiomes

Plant microbiome The plant microbiome, also known as the phytomicrobiome, plays roles in plant health and productivity and has received significant attention in recent years.. Material was copied from this source, which is available under Creative Commons Attri ...

Plant microbiome
s play crucial roles in their health and productivity of mangroves. Many researchers have successfully applied knowledge acquired about plant
microbiome A microbiome () is the community (ecology), community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps ''et al.'' as "a characteristic microbial community occupyi ...
s to produce specific inocula for crop protection. Such inocula can stimulate plant growth by releasing phytohormones and enhancing uptake of some mineral nutrients (particularly phosphorus and nitrogen). However, most of the plant microbiome studies have focused on the model plant ''
Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from ...

Arabidopsis thaliana
'' and economically important crop plants, such as
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
,
barley Barley (''Hordeum vulgare''), a member of the grass family Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consanguinity (by recogn ...

barley
,
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
,
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

maize
and
soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume A legume () is a plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation ...

soybean
. There is less information on microbiomes of tree species. Plant microbiomes are determined by plant-related factors (e.g.,
genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a specific ...
, organ, species, and health status) and environmental factors (e.g., land use, climate, and nutrient availability). Two of the plant-related factors, plant species and genotypes, have been shown to play significant roles in shaping
rhizosphere The rhizosphere is the narrow region of soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive maps of Chic ...

rhizosphere
and plant microbiomes, as tree genotypes and species are associated with specific microbial communities. Different plant organs also have specific microbial communities depending on plant-associated factors (plant genotype, available nutrients, and organ-specific physicochemical conditions) and/or environmental conditions (associated with aboveground and underground surfaces and disturbances).


Root microbiome

Mangrove roots harbour a repertoire of microbial taxa that contribute to important ecological functions in mangrove ecosystems. Similar to typical terrestrial plants, mangroves depend upon mutually beneficial interactions with microbial communities. In particular, microbes residing in developed roots could help mangroves transform nutrients into usable forms prior to plant assimilation. These microbes also provide mangroves phytohormones for suppressing phytopathogens or helping mangroves withstand heat and salinity. In turn, root-associated microbes receive carbon metabolites from the plant via root exudates8, thus close associations between the plant and microbes are established for their mutual benefits. Material was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
Highly diverse microbial communities (mainly bacteria and fungi) have been found to inhabit and function in mangrove roots. For example, Diazotroph, diazotrophic bacteria in the vicinity of mangrove roots could perform biological nitrogen fixation, which provides 40–60% of the total nitrogen required by mangroves; the soil attached to mangrove roots lacks oxygen but is rich in organic matter, providing an optimal microenvironment for sulfate-reducing bacteria (SRB) and methanogens1; ligninolytic, cellulolytic, and amylolytic fungi are prevalent in the mangrove root environment; rhizosphere fungi could help mangroves survive in waterlogged and nutrient-restricted environments. These studies have provided increasing evidences to support the importance of root-associated bacteria and fungi for mangrove growth and health. Recent studies have investigated the detailed structure of root-associated microbial communities at a continuous fine-scale in other plants15, where a microhabitat was divided into four root compartments: endosphere, episphere, rhizosphere, and nonrhizosphere. Moreover, the microbial communities in each compartment have been reported to have unique characteristics. The rhizosphere could emit root exudates that selectively enriched specific microbial populations; however, these exudates were found to exert only marginal impacts on microbes in the nonrhizosphere soil. Furthermore, it was noted that the root episphere, rather than the rhizosphere, was primarily responsible for controlling the entry of specific microbial populations into the root, resulting in the selective enrichment of Proteobacteria in the endosphere. These findings provide new insights into the niche differentiation of root-associated microbial communities, Nevertheless, amplicon-based community profiling may not provide the functional characteristics of root-associated microbial communities in plant growth and biogeochemical cycling. Unraveling functional patterns across the four root compartments holds a great potential for understanding functional mechanisms responsible for mediating root–microbe interactions in support of enhancing mangrove ecosystem functioning.


Mangrove viromes

Mangroves forests are one of the most carbon-rich biomes, accounting for 11% of the total input of terrestrial carbon into oceans. Although viruses are thought to significantly influence local and global biogeochemical cycles, though as of 2019 little information was available about the community structure, genetic diversity and ecological roles of viruses in mangrove ecosystems. Viruses are the most abundant biological entities on earth, present in virtually all ecosystems. By Viral lysis, lysing their hosts, that is, by rupturing their cell membranes, viruses control host abundance and affect the structure of host communities. Viruses also influence their host diversity and evolution through horizontal gene transfer, Natural selection#Arms races, selection for resistance and manipulation of bacterial metabolisms. Importantly, marine viruses affect local and global biogeochemical cycles through the release of substantial amounts of organic carbon and nutrients from hosts and assist microbes in driving biogeochemical cycles with auxiliary metabolic genes (AMGs). It is presumed AMGs augment viral-infected host metabolism and facilitate the production of new viruses. AMGs have been extensively explored in marine cyanophages and include genes involved in photosynthesis, carbon turnover, phosphate uptake and stress response. Cultivation-independent metagenomic analysis of viral communities has identified additional AMGs that are involved in motility, central carbon metabolism, photosystem I, energy metabolism, iron–sulphur clusters, anti-oxidation and sulphur and nitrogen cycling. Interestingly, a recent analysis of Pacific Ocean Virome data identified niche-specialised AMGs that contribute to depth-stratified host adaptations. Given that microbes drive global biogeochemical cycles, and a large fraction of microbes is infected by viruses at any given time, viral-encoded AMGs must play important roles in global biogeochemistry and microbial metabolic evolution. Mangrove forests are the only woody
halophyte Image:Spartina alterniflora.jpg, 250px, ''Spartina alterniflora'' (cordgrass), a halophyte. A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spr ...
s that live in salt water along the world’s subtropical and tropical coastlines. Mangroves are one of the most productive and ecologically important ecosystems on earth. The rates of primary production of mangroves equal those of tropical humid evergreen forests and coral reefs. As a globally relevant component of the carbon cycle, mangroves sequester approximately 24 million metric tons of carbon each year. Most mangrove carbon is stored in soil and sizable belowground pools of dead roots, aiding in the conservation and recycling of nutrients beneath forests. Although mangroves cover only 0.5% of the earth’s coastal area, they account for 10–15% of the coastal sediment carbon storage and 10–11% of the total input of terrestrial carbon into oceans. The disproportionate contribution of mangroves to carbon sequestration is now perceived as an important means to counterbalance greenhouse gas emissions. Despite the ecological importance of mangrove ecosystem, our knowledge on mangrove biodiversity is notably limited. Previous reports mainly investigated the biodiversity of mangrove fauna, flora and bacterial communities. Particularly, little information is available about viral communities and their roles in mangrove soil ecosystems. In view of the importance of viruses in structuring and regulating host communities and mediating element biogeochemical cycles, exploring viral communities in mangrove ecosystems is essential. Additionally, the intermittent flooding of sea water and resulting sharp transition of mangrove environments may result in substantially different genetic and functional diversity of bacterial and viral communities in mangrove soils compared with those of other systems.


Genome sequencing

* ''Rhizophoreae'' as revealed by whole-genome sequencing


See also

* Coastal management ** Mangrove swamp ** Mangrove restoration ** Salt marsh ** Longshore drift ** Coastal erosion ** Coastal geography * Ecological values of mangrove ** Blue carbon * Keystone species


References


Further reading

* Saenger, Peter (2002). ''Mangrove Ecology, Silviculture, and Conservation''. Kluwer Academic Publishers, Dordrecht. . * Ganapathi Thanikaimoni, Thanikaimoni, Ganapathi (1986). ''Mangrove Palynology'' UNDP/UNESCO and the French Institute of Pondicherry, ISSN 0073-8336 (E). * Tomlinson, Philip B. (1986). ''The Botany of Mangroves''. Cambridge University Press, Cambridge, . * Teas, H. J. (1983). ''Biology and Ecology of Mangroves''. W. Junk Publishers, The Hague. . * * * *Agrawala, Shardul; Hagestad; Marca; Koshy, Kayathu; Ota, Tomoko; Prasad, Biman; Risbey, James; Smith, Joel; Van Aalst, Maarten. 2003. Development and Climate Change in Fiji: Focus on Coastal Mangroves. Organisation of Economic Co-operation and Development, Paris, Cedex 16, France. * * * * *Glenn, C. R. 2006
"Earth's Endangered Creatures"
* * * *Twilley, R. R., V.H. Rivera-Monroy, E. Medina, A. Nyman, J. Foret, T. Mallach, and L. Botero. 2000. Patterns of forest development in mangroves along the San Juan River estuary, Venezuela. ''Forest Ecology and Management'' * * * Spalding, Mark; Kainuma, Mami and Collins, Lorna (2010) ''World Atlas of Mangroves'' Earthscan, London, ; 60 maps showing worldwide mangrove distribution * *


External links

* *
Top 10 Mangrove Forest In The World - Travel Mate
** * *In May 2011, the VOA Special English service of the Voice of America broadcast a 15-minute program on mangrove forests. A transcript and MP3 of the program, intended for English learners, can be found a
Mangrove Forests Could Be a Big Player in Carbon Trading
* *
Queensland’s coastal kidneys: mangroves
Stacey Larner, John Oxley Library Blog. State Library of Queensland. {{Authority control Mangroves, Aquatic biomes Aquatic ecology Blue carbon Mangrove ecoregions, Terrestrial biomes Plant common names Oceanographical terminology