Fall Asleep While Learning Mangroves

In this episode of the I Can't Sleep Podcast, fall asleep while learning about mangroves. Trees, trees, trees. The world has them, and they are, well, boring. I love the shade they provide in my backyard during the hot summer, but man, they're a pain to take care of after the leaves fall! But I still love them. Oh, and they are pretty boring—especially the mangroves. Sure, they are more interesting than maples (I assume) because they can live in brackish water, but don't get too braggadocious, mangroves. Happy sleeping!

Transcript

Welcome to the I Can't Sleep Podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Boster,

And today's episode is from a Wikipedia article titled Mangrove.

A mangrove is a shrub or tree that grows mainly in coastal saline or brackish water.

Mangroves grow in an equatorial climate,

Typically along the coastlines and tidal rivers.

They have particular adaptations to take in extra oxygen and remove salt,

Allowing them to tolerate conditions that kill most plants.

The term is also used for tropical coastal vegetation consisting of such species.

Mangroves are taxonomically diverse due to convergent evolution in several plant families.

They occur worldwide in the tropics and subtropics and even some temperate coastal areas,

Mainly between latitudes 30°N and 30°S,

With the greatest mangrove area within 5° of the equator.

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 date to 75 million years ago.

Mangroves are salt-tolerant trees,

Shrubs,

And ferns,

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 mangrove biome,

Often called the mangrove forest or mangle,

Is a distinct saline woodland or shrubland habitat characterized by depositional coastal environments,

Where fine sediments often with high organic content collect in areas protected from high energy wave action.

Mangrove forests serve as vital habitats for a diverse array of aquatic species,

Offering a unique ecosystem that supports the intricate interplay of marine life and terrestrial vegetation.

The saline conditions tolerated by various mangrove species range from brackish water through pure seawater,

3-4% 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 air areas,

Conditions,

And deforestation rates of mangroves around the world.

In 2018,

The Global Mangrove Watch initiative released a new global baseline which estimates that total mangrove forest area of the world as of 2010 had 137,

600 square kilometers,

Spanning 118 countries and territories.

A 2022 study on losses and gains of tidal wetlands estimates a 3,

700 square kilometer net decrease in global mangrove extent from 1999 to 2019.

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.

7%.

Degradation and quality of remaining mangroves is also an important concern.

Etymology of the English term mangrove can only be speculative and is disputed.

The term may have come to English from the Portuguese meng or the Spanish mangle.

Further back,

It may be traced to South America and Caribbean and Arawakan languages such as Taino.

Other possibilities include the Malay language mengi mengi.

The English usage may reflect a corruption via folk etymology of the words mangrove and grove.

The word mangrove is used in at least three senses.

Most broadly to refer to the habitat and entire plant assemblage or mangle,

For which the term mangrove forest biome and mangrove swamp are also used.

To refer to all trees and large shrubs in a mangrove swamp.

And narrowly to refer only to mangrove trees of the genus Rhizophora of the family Rhizophoraceae.

According to Hogarth 2015,

Among the recognized mangrove species there are about 70 species in 20 genera from 16 families that 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 survives in most inundated areas,

Props itself above the water level with stilt or prop roots,

And then absorbs air through lenticels in its bark.

The black mangrove 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 30 centimeters and in some species over 3 meters.

The roots also contain aranchema 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,

Sulfides,

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 that are highly subarized,

Acting as an ultrafiltration mechanism to exclude sodium salts from the rest of the plant.

One study found that roots of the Indian mangrove exclude 90% to 95% of the salt and water taken up by the plant,

Depositing the excluded salt in the cortex of the roots.

An increase in the production of subarin and in the activity of a gene regulating cytochrome P450 were observed in correlation with an increase in the salinity of the water to which the plant was exposed.

In a frequently cited concept that has become known as the sacrificial leaf,

Salt which does accumulate in the shoot then concentrates in old leaves,

Which the plant then sheds.

However,

Recent research on the red mangrove suggests that the older,

Yellowing leaves have no more measurable salt content than the other,

Greener leaves.

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,

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 seawater filtration in the roots of the mangrove from a plant hydrodynamic point of view.

R.

Styloza 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,

And most Na plus ions are filtered at the first sublayer of the outermost layer.

The high blockage of Na plus 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 plus 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 method of desalination.

Uptake of Na plus ions is desirable for halophytes to build up osmotic potential,

Absorb water,

And sustain turgor pressure.

However,

Excess Na plus ions may work on toxic elements.

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 leaves and or the bark.

Mangroves are a facultative of halophytes,

And Brugueria is known for its special ultrafiltration system that can filter approximately 90% of Na plus ions from the surrounding seawater through the roots.

The species also exhibits a high rate of salt rejection.

The water filtration 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.

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 or out through the fruit to form a propagule,

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.

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.

Mangrove Forests Mangrove forests,

Also called mangrove swamps or mangles,

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 saltwater,

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 increase 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 to 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.

Mangrove plants require a number of physiological adaptations to overcome the problems of low environmental oxygen levels,

High salinity,

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 mangrove 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 and oxic 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,

Especially during tropical cyclones and tsunamis.

They limit high-energy wave erosion,

Mainly during events such as storm surges and tsunamis.

The mangrove's 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,

Barnacles,

Oysters,

Bunges,

And bryozoans,

Which all require a hard surface for anchoring while they filter feed.

Shrimps and mud lobsters use the muddy bottoms as their home.

Mangrove crabs eat the mangrove leaves,

Adding nutrients to the mangle mud for other bottom feeders.

In at least some cases,

The export of carbon fixed in mangroves is important in coastal food webs.

Mangrove forests contribute significantly to coastal ecosystems by fostering complex and diverse food webs.

The intricate root systems of mangroves create a habitat conducive to the proliferation of microorganisms,

Crustaceans,

And small fish,

Forming the foundational tiers of the food chain.

This abundance of organisms serves as a critical food source for larger predators like birds,

Reptiles,

And mammals within the ecosystem.

Additionally,

Mangrove forests function as essential nurseries for many commercially important fish species,

Providing a sheltered environment rich in nutrients during their early life stages.

The decomposition of leaves and organic matter in the water further enhances the nutrient content,

Supporting overall ecosystem productivity.

In summary,

Mangrove forests play a crucial and unbiased role in sustaining biodiversity and ecological balance within coastal food webs.

Larger marine organisms benefit from the habitat as a nursery for their offspring.

Lemon sharks depend on mangrove creeks to give birth to their pups.

The ecosystem provides little competition and minimizes threats of predation to juvenile lemon sharks as they use the cover of mangroves to practice hunting before entering the food web of the ocean.

Mangrove plantations in Vietnam,

Thailand,

Philippines,

And India host several commercially important species of fish and crustaceans.

The mangrove food chain extends beyond the marine ecosystem.

Coastal bird species inhabit the tidal ecosystems feeding off small marine organisms and wetland insects.

Common bird families found in mangroves around the world are egrets,

Kingfishers,

Herons,

And hornbills,

Among many others dependent on ecological range.

Bird predation plays a key role in maintaining prey species along coastlines and within mangrove ecosystems.

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,

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 as 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.

Mangrove Microbiome Plant microbiomes play crucial roles in the 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 in economically important crop plants such as rice,

Barley,

Wheat,

Maize,

And soybean.

There is less information on the microbiomes of tree species.

Plant microbiomes are determined by plant-related factors e.

G.

Genotype,

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,

Different plant organs also have specific microbial communities depending on plant-associated factors,

Plant genotype,

Available nutrients,

And organ-specific physiochemical conditions and environmental conditions associated with above-ground and underground surfaces and disturbances.

ROOT MICROBIOME Mangrove roots harbor a repertoire of microbial taxa that contribute to important ecological functions in mangrove ecosystems.

Like 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 before 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 exudates.

Thus,

Close associations between the plant and microbes are established for their mutual benefits.

Reviews

Thank you, Benjamin! Success in boring me to sleep once again! 😁

Thank you, Ben. Fell asleep but didn’t stay there. That happens. Not your fault. I’ll try another reading.