Mangrove And Pneumatophores In Moreton Bay, Qld
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A mangrove is a
shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...
or tree that grows in coastal
saline Saline may refer to: * Saline (medicine), a liquid with salt content to match the human body * Saline water, non-medicinal salt water * Saline, a historical term (especially US) for a salt works or saltern Places * Saline, Calvados, a commune in ...
or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in several plant families. They occur worldwide in the tropics and
subtropics The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...
and even some temperate coastal areas, mainly between latitudes 30° N and 30° S, with the greatest mangrove area within 5° of the
equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...
. Mangrove plant families first appeared during the Late Cretaceous to Paleocene epochs, and became widely distributed in part due to the movement of tectonic plates. The oldest known fossils of
mangrove palm ''Nypa fruticans'', commonly known as the nipa palm (or simply nipa, from ms, nipah) or mangrove palm, is a species of palm native to the coastlines and estuarine habitats of the Indian and Pacific Oceans. It is the only palm considered adapted ...
date to 75 million years ago. Mangroves are salt-tolerant trees, also called halophytes, 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, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...
. The mangrove biome, 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 mangroves cannot withstand fr ...
or mangal, is a distinct saline woodland or
shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity. It m ...
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. A 2022 study on losses and gains of tidal wetlands estimates a 3,700 km2 net decrease in global mangrove extent from 1999–2019, which was only partially offset by gains of 1,800 km2. 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 restoration for several reasons. Mangroves support sustainable coastal and marine ecosystems. They protect nearby areas from tsunamis and extreme weather events. Mangrove forests are also effective at carbon sequestration and storage and
mitigate climate change Climate change mitigation is action to limit climate change by reducing emissions of greenhouse gases or removing those gases from the atmosphere. The recent rise in global average temperature is mostly caused by emissions from fossil fuels bur ...
. As the effects of climate change become more severe, mangrove ecosystems are expected to help local ecosystems adapt and be more resilient to changes like extreme weather and sea level rise. 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'' can only be speculative and is disputed. The term may have come to English from the Portuguese ' or the Spanish '. Further 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 ...
and Arawakan languages such as Taíno. Other possibilities include the Malay language and the Guarani language. 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 famili ...
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 ...
''. 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'' and ''mangrove swamp'' are also used; * to refer to all trees and large shrubs in a mangrove
swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
; and * narrowly to refer only to mangrove trees of the genus '' Rhizophora'' of the family Rhizophoraceae. 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 constitute the "true mangroves", species that occur almost exclusively in mangrove habitats. Demonstrating convergent evolution, many of these species found similar solutions to the tropical conditions of variable salinity, tidal range (inundation), anaerobic soils, and intense sunlight. Plant biodiversity is generally low in a given mangrove. The greatest biodiversity of mangroves occurs in Southeast Asia, particularly in the Indonesian archipelago.


Adaptations to low oxygen

The red mangrove ('' 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 A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of dicotyledonous flowering plants. It functions as a pore, providing a ...
s in its bark. The black mangrove ('' Avicennia germinans'') lives on higher ground and develops many specialized root-like structures called pneumatophores, 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 to facilitate transport within the plants.


Nutrient uptake

Because the soil is perpetually waterlogged, little free oxygen is available. Anaerobic bacteria liberate nitrogen gas, soluble ferrum (iron), inorganic phosphates,
sulfide Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds lar ...
s, and methane, which make the soil much less nutritious. Pneumatophores ( aerial roots) 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), acting as an ultra-filtration mechanism to exclude sodium salts 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 vacuoles. 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, Pneumatophorous aerial roots of the grey mangrove ('' Avicennia marina'') File:Plody mangrovnika (Rhizophora mangle).jpg, Vivipary in ''Rhizophora mangle'' seeds


Limiting water loss

File:Water filtration in mangrove roots.webp,
(a) Schematic of the root. The outermost layer is composed of three layers. The root is immersed in NaCl solution.
(b) Water passes through the outermost layer when a negative suction pressure is applied across the outermost layer. The
Donnan potential Donnan potential is the difference in the Galvani potentials which appears as a result of Donnan equilibrium, named after Frederick G. Donnan, which refers to the distribution of ion species between two ionic solutions separated by a semipermeab ...
effect repels Cl ions from the first sublayer of the outermost layer. Na+ ions attach to the first layer to satisfy the electro-neutrality requirement and salt retention eventually occurs. Material was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
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 In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...
(pores on the leaf surfaces, which exchange 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'' 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, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
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 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 roots and could serve as a basis for the development of a
bio-inspired Bioinspiration is the development of novel materials, devices, and structures inspired by solutions found in biological evolution and refinement which has occurred over millions of years. The goal is to improve modeling and simulation of the biolog ...
method of
desalination Desalination is a process that takes away mineral components from saline water. More generally, desalination refers to the removal of salts and minerals from a target substance, as in Soil salinity control, soil desalination, which is an issue f ...
. 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 against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibri ...
. 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 Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence invol ...
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. It is a small genus of five mangrove species and three hybrids of the Indian and west Pacific Ocean region, its range extending from East Africa and Madagascar through coastal India, ...
'' 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 seeds are buoyant and are therefore suited to water dispersal. Unlike most plants, whose seeds germinate in soil, many mangroves (e.g. red mangrove) are viviparous, meaning their seeds germinate while still attached to the parent tree. Once germinated, the seedling grows either within the fruit (e.g. ''
Aegialitis ''Aegialitis'' is a genus of two shrubby mangrove species, with one native to Southeast Asia and the other native to Australia and Papua New Guinea. Description The two species of the genus are woody mangrove shrubs or small trees that grow ...
'', '' Avicennia'' and '' Aegiceras''), or out through the fruit (e.g. '' Rhizophora'', ''
Ceriops ''Ceriops'' is a genus of mangroves in family Rhizophoraceae. There are 5 accepted species and 17 known synonyms. List of species * ''Ceriops australis'' (C.T.White) Ballment, T.J.Sm. & J.A.Stoddart ** ''Ceriops tagal'' var. ''australis'' C.T ...
'', ''
Bruguiera ''Bruguiera'' is a plant genus in the family Rhizophoraceae. It is a small genus of five mangrove species and three hybrids of the Indian and west Pacific Ocean region, its range extending from East Africa and Madagascar through coastal India, ...
'' and '' Nypa'') to form a
propagule In biology, a propagule is any material that functions in propagating an organism to the next stage in its life cycle, such as by dispersal. The propagule is usually distinct in form from the parent organism. Propagules are produced by organisms ...
(a ready-to-go seedling) which can produce its own food via 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 Bunbury (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 wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangroves cannot withstand fr ...
s, also called ''mangrove swamps'' or ''mangals'', are found in tropical and subtropical tidal areas. Areas where mangroves occur include estuaries and marine shorelines. The intertidal 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, the megafauna (from Greek μέγας ''megas'' "large" and New Latin ''fauna'' "animal life") comprises the large or giant animals of an area, habitat, or geological period, extinct and/or extant. The most common threshold ...
. 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 dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
, and frequent tidal flooding. 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 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,
storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the n ...
(especially during tropical cyclones), and tsunamis. 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 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 eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
,
barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...
s, oysters, sponges, and bryozoans, which all require a hard surface for anchoring while they filter-feed.
Shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...
s and mud lobsters use the muddy bottoms as their home. Mangrove crabs 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, Thailand, Philippines, and India host several commercially important species of fish and crustaceans. Mangrove forests can decay into peat deposits because of fungal and bacterial processes as well as by the action of termites. 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 e ...
, sedimentary, and tectonic conditions. The nature of these deposits depends on the environment and the types of mangroves involved. In Puerto Rico, the red, white, and black mangroves occupy different ecological niches and have slightly different chemical compositions, so the carbon content 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 organic carbon that is captured and stored by the world's oceanic and coastal ecosystems, mostly by algae, seagrasses, macroalgae, mangroves, salt marshes and other plants in coastal wetlands. The term Blue Carbon was coined ...
. 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. Globally, mangroves have been shown to provide measurable economic protections to coastal communities affected by tropical storms.


Mangrove microbiome

Plant microbiomes play crucial roles in their health and productivity of mangroves. Many researchers have successfully applied knowledge acquired about plant microbiomes 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 native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter a ...
'' and economically important crop plants, such as rice , barley, wheat, maize and 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 alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...
, 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 and plant microbiomes, as tree genotypes and species are associated with specific
microbial communities Microbial population biology is the application of the principles of population biology to microorganisms. Distinguishing from other biological disciplines Microbial population biology, in practice, is the application of population ecology and popu ...
. 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 A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
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
phytopathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...
s or helping mangroves withstand heat and salinity. In turn, root-associated microbes receive carbon
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
s from the plant via root
exudate An exudate is a fluid emitted by an organism through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from Latin ''exsūdāre'' 'to (ooze out) sweat' (''ex-'' 'out' and ''sūdāre'' 'to ...
s, 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, 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 and
methanogen Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain Archaea. All known methanogens are members of the archaeal phylum Euryarchaeota. Methanogens are com ...
s,
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
olytic, 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 plants, 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 virome

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 mangroves cannot withstand fr ...
s are one of the most carbon-rich biomes, accounting for 11% of the total input of terrestrial carbon into oceans. Viruses are thought to significantly influence local and global
biogeochemical cycle A biogeochemical cycle (or more generally a cycle of matter) is the pathway by which a chemical substance cycles (is turned over or moves through) the biotic and the abiotic compartments of Earth. The biotic compartment is the biosphere and the ...
s, 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
lysing Lysis ( ) is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ''lysate''. In molecular bio ...
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, selection for resistance and manipulation of bacterial metabolisms. Importantly,
marine virus Marine viruses are defined by their habitat as viruses that are found in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Viruses are small infectious agents that can only replicate i ...
es affect local and global
biogeochemical cycle A biogeochemical cycle (or more generally a cycle of matter) is the pathway by which a chemical substance cycles (is turned over or moves through) the biotic and the abiotic compartments of Earth. The biotic compartment is the biosphere and the ...
s through the release of substantial amounts of organic carbon and nutrients from hosts and assist microbes in driving biogeochemical cycles with
auxiliary metabolic genes Auxiliary metabolic genes (AMGs) are found in many bacteriophages but originated in bacterial cells. AMGs modulate host cell metabolism during infection so that the phage can replicate more efficiently. For instance, bacteriophages that infect the ...
(AMGs). It is presumed AMGs augment viral-infected host metabolism and facilitate the production of new viruses. AMGs have been extensively explored in
marine cyanophage Cyanophages are viruses that infect cyanobacteria, also known as Cyanophyta or blue-green algae. Cyanobacteria are a phylum of bacteria that obtain their energy through the process of photosynthesis. Although cyanobacteria metabolize photoautotrop ...
s 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 halophytes 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, 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 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 mangroves cannot withstand fre ...
** Mangrove restoration ** Salt marsh **
Longshore drift Longshore drift from longshore current is a geological process that consists of the transportation of sediments (clay, silt, pebbles, sand, shingle) along a coast parallel to the shoreline, which is dependent on the angle incoming wave direction ...
** Coastal erosion **
Coastal geography Coastal geography is the study of the constantly changing region between the ocean and the land, incorporating both the physical geography (i.e. coastal geomorphology, climatology and oceanography) and the human geography (sociology and history) ...
*
Ecological values of mangrove Mangrove ecosystems represent natural capital capable of producing a wide range of goods and services for coastal environments and communities and society as a whole. Some of these outputs, such as timber, are freely exchanged in formal markets. V ...
**
Blue carbon Blue Carbon refers to organic carbon that is captured and stored by the world's oceanic and coastal ecosystems, mostly by algae, seagrasses, macroalgae, mangroves, salt marshes and other plants in coastal wetlands. The term Blue Carbon was coined ...
** Nursery habitat ** Foundation species *
Keystone species A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance, a concept introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaini ...


References


Further reading

* Saenger, Peter (2002). ''Mangrove Ecology, Silviculture, and Conservation''. Kluwer Academic Publishers, Dordrecht. . * 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 * Warne, Kennedy (2013) ''Let them eat shrimp: the tragic disappearance of the rainforests of the sea.'' Island Press, 2012, * *


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 Aquatic biomes Aquatic ecology Blue carbon Terrestrial biomes Plant common names Oceanographical terminology