Marine Conservation Science and Policy Service
learning Program
Mangroves are trees that grow in tropical and subtropical intertidal zones. These areas
are tough places for plants to grow. During low tides intertidal zones are exposed to air.
During high tides they’re covered by salt water. They flood frequently. The soil is poor.
But mangrove trees survive and even thrive in these harsh conditions. Big groups of
mangroves and other plants that live here are called mangrove swamps, mangrove
forests, and sometimes simply mangal.
Module 1: Ocean and Coastal Habitats
Section 3: mangroves
Sunshine State Standards
SC.912.N.1.1, SC.912.N.1.4, SC.912.E.7.4, SC.912.L.14.3,
SC.912.L.14.7,
SC.912.L.14.8,
SC.912.L.14.10,
SC.912.L.15.2, SC.912.L.15.13
Objectives
Students will be able to:
 Identify and research the types of organisms that live in mangroves.
 Name and describe 4 common mangrove species found in South Florida
 Compare and contrast the characteristics and adaptations of different mangrove
species
 Recognize the different life characteristics of mangroves
 Identify the different stages of mangroves in the field
 Discuss the benefits that mangroves offer to the environment and our community
 Measure the growth of mangrove seedlings
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Vocabulary
Estuary- is a partly enclosed coastal body of water with one or more rivers or streams
flowing into it, and with a free connection to the open sea.
Halophyte- Any plant that tolerates an environment having a high salt content
Mangrove- trees and shrubs that grow in saline coastal habitats in the tropics and
subtropics
Pneumatophores- aerial roots found on the black mangroves
Propagules– the viviparous seeds produced by mangroves
Background
Mangroves are trees and shrubs that grow in saline coastal habitats in the tropics and
subtropics – mainly between latitudes 25° N and 25° S. The saline conditions tolerated
by various species range from brackish water, through pure seawater (30 to 40 ppt), to
water of over twice the salinity of ocean seawater, where the salt becomes concentrated
by evaporation (up to 90 ppt).
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There are many species of trees and shrubs adapted to saline conditions. Not all are
closely related, and the term "mangrove" may be used for all of them, or more narrowly
only for the mangrove family of plants, the Rhizophoraceae, or even more specifically
just for mangrove trees of the genus Rhizophora.
Mangroves form a characteristic saline woodland or shrubland habitat, called
mangrove swamp, mangrove forest, mangrove or mangal. Mangals are found in
depositional coastal environments where fine sediments (often with high organic
content) collect in areas protected from high energy wave action. They occur both in
estuaries and along open coastlines. Mangroves dominate three quarters of tropical
coastlines
Mangroves are found in tropical and sub-tropical tidal areas, and as such have a high
degree of salinity. Areas where mangals occur include estuaries and marine shorelines.
Why are mangroves important?
The mangrove community is valued for its protection and stabilization of lowlying
coastal lands and its importance in estuarine and coastal fishery food chains. Mangrove
forests protect uplands from storm winds, waves, and floods. The amount of protection
afforded by mangroves depends upon the width of the forest. Mangroves can help
prevent erosion by stabilizing shorelines with their specialized root systems.
The relationship between mangroves and their associated marine life cannot be
overemphasized. Mangroves provide protected nursery areas for fishes, crustaceans,
and shellfish. Seventy-five percent of the game fish and ninety percent of the
commercial species in south Florida are dependent on mangrove ecosystems (Law and
Pywell FRC-43). They provide food for a multitude of marine species such as snook,
snapper, tarpon, jack, sheepshead, red drum, oysters, and shrimp.
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Many animals find shelter either in the roots or branches of mangroves. Mangroves
serve as rookeries, or nesting areas, for beautiful coastal birds such as brown pelicans
and roseate spoonbills.
Plants in mangals are diverse but all are able
to exploit their habitat (the intertidal zone) by
developing physiological adaptations to
overcome the problems of anoxia, high salinity
and frequent tidal inundation. About 110
species belong to the mangal. Each species
has its own solutions to these problems; this
may be the primary reason why, on some
shorelines, mangrove tree species show
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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, like tidal inundation and salinity, but may
also be influenced by other factors such as predation of plant
seedlings by crabs.
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 scavenged from the
water. Mangrove removal disturbs these underlying sediments, often creating problems
of trace metal contamination of seawater and biota.
Mangroves protect coastal areas from erosion, storm surge (especially during
hurricanes), and tsunamis. The mangrove's massive root system is efficient at
dissipating wave energy. Likewise, they slow down tidal water enough 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 own environment. Because of the uniqueness of
mangrove ecosystems and the protection against erosion that they provide, they are
often the object of conservation programs including national Biodiversity Action Plans.
However, mangroves' protective value is sometimes overstated. Wave energy is
typically low in areas where mangroves grow, so their effect on erosion can only be
measured over long periods. Their capacity to limit high-energy wave erosion is limited
to events like storm surges and tsunamis. Erosion often occurs on the outer sides of
bends in river channels that wind through mangroves, while new stands of mangroves
are appearing on the inner sides where sediment is accreting.
The unique ecosystem found in the intricate mesh of
mangrove roots offers a quiet marine region for young
organisms. In areas where roots are permanently
submerged, the organisms they host include algae,
barnacles, oysters, sponges, and bryozoans, which all
require a hard surface for anchoring while they filter
feed. Shrimps and mud lobsters use the muddy bottom
as their home. Mangrove crabs mulch the mangrove
leaves, adding nutritients to the mangal muds for other bottom feeders. In at least some
cases, export of carbon fixed in mangroves is important in coastal food webs.
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Mangrove plantations in Vietnam, Thailand, the Philippines and India host several
commercially important species of fish and crustaceans. Despite restoration efforts,
developers and others have removed over half of the world's mangroves in recent
times.
Survival of the Few
Not many plants can make it in the mangal. Only about one hundred plant species are
found in most mangrove swamps. Some swamps are home to only one or two species!
(The rain forest, on the other hand, has many thousands.) Ferns live in mangrove
swamps, as well as some kinds of pine and palm trees.
Please Pass the Salt
Mangroves survive in the very salty mangrove waters because they
can get rid of the salt through the glands in their leaves.
The plants that do survive have ―tricks‖ up their sleeves called
adaptations to deal with the special challenges. One of the biggest
challenges is the salinity, or the amount of salt in the water. The
water in a mangrove swamp is so salty it would kill most plants. But
the roots of red mangroves contain a waxy substance that helps
keep salt out. The salt that does get through this barrier is sent to
old leaves that the trees then shed. It’s like taking the trash to the
curb so the garbage truck can haul it away.
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Rain, Rain, DON’T Go Away!
Just as mangroves can keep salt out, they have other
adaptations to keep freshwater in. They can close up the
pores in their leaves. They can also turn their leaves away
from the sun to keep from drying out.
All of the plants found only in mangroves are woody and
tree-like. They tend to be short with tough, evergreen
leaves – another adaptation that keeps the moisture in.
Take a Deep Breath. Well, Try.
Lack of oxygen is a huge challenge in mangrove forests. The soil is covered with salt
water every time the tide comes in. Salt water’s low oxygen level means bacteria can
thrive. These bacteria free up chemicals and substances harmful to plants, like
phosphates, sulfides, and methane.
So mangrove trees grow fancy systems of roots that make the trees look as if they’re
growing on a bunch of stilts. The roots ―breathe‖ through knobby holes called lenticels
(LEN-tuh-sels). They take in carbon dioxide directly from the air, instead of from the soil
like other plants.
Let’s Root for the Roots
The tangle of mangrove roots offers safe habitats for fish,
shrimp, and oysters. The roots help stop erosion by
anchoring the ground and also lessening the effects of the
waves. They prevent silt from damaging reefs and sea
grass beds. They trap sediments that can contain
dangerous heavy metals, keeping them away from inland
waters and fragile animal (and human) populations.
Manatees, Monkeys and a Fishing Cat
Mangrove forests are nesting grounds for hundreds of species of
birds. They’re home to manatees, monkeys, turtles, fish, monitor
lizards, and, in parts of Asia, the fishing cat. In Florida, mangroves
shelter endangered species such as hawksbill turtles, bald eagles,
and American crocodiles.
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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 mangal. This is especially true in higher
latitudes and in the Americas. The greatest biodiversity occurs in the mangal of New
Guinea, Indonesia and Malaysia.
Adaptations to low oxygen
Red mangroves, which can survive in the most
inundated areas, prop themselves above the water
level with stilt roots and can then absorb air through
pores in their bark (lenticels). Black mangroves live on
higher ground and make many pneumatophores
(specialised root-like structures which stick up out of
the soil like straws for breathing) which are also
covered in lenticels. These "breathing tubes" typically
reach heights of up to thirty centimeters, and in some
species, over three meters. There are four types of
pneumatophore—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 oxygen transport within the plant.
Limiting salt intake
Red mangroves exclude salt by having significantly
impermeable roots which are highly suberised, acting as
an ultra-filtration mechanism to exclude sodium salts from
the rest of the plant. Analysis of water inside mangroves
has shown that 90% to 97% of salt has been excluded at
the roots. Salt which does accumulate in the shoot
concentrates in old leaves which the plant then sheds.
Red mangroves can also store salt in cell vacuoles. White
(or grey) mangroves can secrete salts directly; they have
two salt glands at each leaf base (hence their name—they are covered in white salt
crystals).
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Limiting water loss
Because of the limited freshwater availability in salty intertidal soils, mangroves limit the
amount of water that 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
vapour during photosynthesis). They also vary the orientation of their leaves to avoid
the harsh midday sun and so reduce evaporation from the leaves. Anthony Calfo, a
noted aquarium author, observed anecdotally that a red mangrove in captivity only
grows if its leaves are misted with fresh water several times a week, simulating the
frequent tropical rainstorms.
Nutrient uptake
The biggest problem that mangroves face is nutrient uptake. Because the soil is
perpetually waterlogged, there is little free oxygen. Anaerobic bacteria liberate nitrogen
gas, soluble iron, inorganic phosphates, sulfides, and methane, which makes the soil
much less nutritious and contributes to mangroves' pungent odor. Prop root systems
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.
Increasing survival of offspring
In this harsh environment, mangroves have evolved a
special mechanism to help their offspring survive.
Mangrove seeds are buoyant and therefore suited to
water dispersal. Unlike most plants, whose seeds
germinate in soil, many mangroves (e.g. Red
Mangrove) are viviparous, whose seeds germinate
while still attached to the parent tree. Once
germinated, the seedling grows either within the fruit
(e.g. Aegialitis, Avicennia and Aegiceras), or out through the fruit (e.g. Rhizophora,
Ceriops, Bruguiera and Nypa) 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 doesn't
root, it can alter its density and drift again in search of more favorable
conditions.
Geographical regions
Mangroves occur in numerous areas worldwide. See List of mangrove
ecoregions.
Africa
The mangroves survive the heat of the city of Bombay/ Mumbai and Navi Mumbai
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There are important mangrove swamps in Kenya and Madagascar, with the latter even
admixing at the coastal verge with dry deciduous forests.
Nigeria has Africa's largest mangrove concentration, spanning 36,000 km2. Oil spills
and leaks have destroyed many in the last fifty years, damaging the local fishing
economy and water quality.
Along the coast of the Red Sea both on the Egyptian side and in the Gulf of Aqaba,
mangroves composed primarily of Avicennia marina and Rhyzophora mucronata in
about 28 stands cover about 525 hectares. Almost all Egyption mangrove stands are
now protected.
Americas
Mangroves live in many parts of the tropical and subtropical coastal zones of North,
South and Central America.
Continental United States
Because of their sensitivity to subfreezing temperatures, mangroves
in the continental United States are
limited to the Florida peninsula and
isolated
growths
of
Black
Mangrove (Avicennia germinans)
along the coast of southern
Louisiana and south Texas
Central
Caribbean
America
&
Mangroves occur on the west
coast of Costa Rica, on the Pacific and Caribbean coasts of Nicaragua, Belize,
Guatemala, Honduras, and Panama and on many Caribbean Islands, such as Curaçao,
Bonaire, Antigua, the Bahamas, Saint Kitts and Nevis and St. Lucia. Significant mangals
include the Marismas Nacionales-San Blas mangroves in Mexico. Mangroves can also
be found in Puerto Rico, Cuba, the Dominican Republic, Haiti, Jamaica, Trinidad,
Barbados, and the Pacific coast of El Salvador.
South America
Brazil contains approximately 26,000 km2 of mangals, 15% of the world's total of
172,000 km2.
Ecuador and Peru have significant areas of mangroves mainly in the Gulf of GuayaquilTumbes mangroves.
Venezuela's northern Caribbean island, Margarita, possesses mangrove forests in the
Parque Nacional la Restinga.
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Colombia possesses large mangrove forests on both its Caribbean and Pacific coasts.
Asia
Indomalaya ecozone
Mangroves occur on Asia's south coast, throughout the Indian subcontinent, in all
southeast Asian countries, and on islands in the Indian Ocean, Arabian Sea, Bay of
Bengal, South China Sea and the Pacific.
The mangal is particularly prevalent in the deltas of large Asian rivers. The Sundarbans
is the largest mangrove forest in the world, located in the Ganges delta in Bangladesh
and West Bengal, India.
The Pichavaram Mangrove Forest near Chidambaram, South India, by the Bay of
Bengal is the world's second largest mangrove forest. Notably, it has actually increased
by 90% in size between 1986 and 2002.
Major mangals live on the Andaman and Nicobar Islands and the Gulf of Kutch in
Gujarat.
Other significant mangals include the Bhitarkanika Mangroves and Godavari-Krishna
mangroves.
The mangal in the Ganges-Surma-Meghna River System delta was one of the largest in
the world.
In Vietnam, mangrove forests grow along the southern coast, including two forests: the
Can Gio Mangrove Forest biosphere reserve and the U Minh mangrove forest in the
Sea and Coastal Region of Kien Giang, Ca Mau and Bac Lieu province.
The mangrove forests of Kompong Sammaki in Cambodia are of major ecological and
cultural importance, as the human population relies heavily on the crabs and fish that
live in the roots.
The three most important mangrove forests of Taiwan are: Tamsui River in Taipei,
Jhonggang River in Miaoli and the Sihcao Wetlands in Tainan. According to research,
there are four existing types of mangrove in Taiwan.[citation needed] Some places have
been developed as scenic areas, such as the log raft routes in Sihcao.
In the Indonesian Archipelago, mangroves occur around much of Sumatra, Borneo,
Sulawesi and the surrounding islands. While further north they found along the coast of
the Malay Peninsula.
Pakistan
Pakistani mangroves are located mainly on the Indus delta (the Indus River DeltaArabian Sea mangroves ecoregion. Major mangrove forests are also found on the
coastal line of provinces Sindh and Balochistan.
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In Pakistan, the mangrove forest are located on the coasts of Sindh and Balochistan
provinces. In Karachi, land reclamation projects are cutting down mangrove forests and
filling then earth and selling them for commercial and urban development.
Middle East
Oman, near Muscat, supports large areas of mangroves, in particular at Shinas, Qurm
Park and Mahout Island. In Arabic, mangrove trees are known as qurm, thus the
mangrove area in Oman is known as Qurm Park. Mangroves are also present
extensively in neighboring Yemen.
Iranian mangrove forests occur between 25°11′N to 27°52′N. These forests exist in the
north part of the Persian Gulf and Oman Sea, along three Maritime Provinces in the
south of Iran. These provinces respectively from southwest to southeast of Iran, include
Bushehr, Hormozgan and Sistan & Balouchestan.
Australia
More than fifty species of Rhizophoraceae grow in Australasia with particularly high
biodiversity on the island of New Guinea and northern Australia.
Australia has approximately 11,500 km2 of mangroves primarily on the northern and
eastern coasts of the continent, with occurrences as far south as Millers Landing in
Wilsons Promontory, Victoria (38°54′S) and Barker Inlet in Adelaide, South Australia.
New Zealand
New Zealand also has mangrove forests extending to around 38°S (similar to Australia's
southernmost mangrove incidence): the furthest geographical extent on the west coast
is Raglan Harbour (37°48′S); on the east coast, Ohiwa Harbour (near Opotiki) is the
furthest south that mangroves are found (38°00′S).
Pacific islands
Twenty-five species of mangrove are found on various Pacific
islands, with extensive mangals on some islands. Mangals on
Guam, Palau, Kosrae and Yap have been badly affected by
development.
Mangroves are not native to Hawaii, but the Red mangrove,
Rhizophora mangle, and Oriental mangrove, Bruguiera
sexangula, have been introduced and are now naturalized. Both
species are classified as pests by the University of Hawaii Botany
Department.
Cultivating Mangroves
Red mangroves are the most common choice, used particularly in
marine aquariums in a sump to reduce nitrates and other nutrients
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in the water. Mangroves also appear in home aquariums, and as ornamental plants,
such as in Japan.
The Manzanar Mangrove Initiative is an ongoing experiment in Arkiko, Eritrea, part of
the Manzanar Project founded by Dr Gordon H. Sato; establishing new mangrove
plantations on the coastal mudflats. Initial plantings failed, but observation of the areas
where mangroves did survive by themselves led to the conclusion that nutrients in water
flow from inland were important to the health of the mangroves. Trials with the Eritrean
Ministry of Fisheries followed and a planting system was designed to introducing the
nitrogen, phosphorus, and iron missing from seawater. The propagules are planted
inside a reused galvanised steel can with the bottom knocked out; a small piece of iron
and a pierced plastic bag with fertilizer containing nitrogen and phosphorus are buried
with the propagule. As at 2007, after six years of planting, there are 700,000 mangroves
growing; providing stock feed for sheep and habitat for oysters, crabs, seashells and
fish.
Mangroves for Many Uses
Millions of people in developing parts of the world where mangroves flourish rely on the
mangal for a huge portion of their daily needs. They use mangrove wood for fuel and to
build boats and furniture. They use the bark for dye and medicine. They use leaves for
tea and animal feed and the fruit for food. These coastal swamps protect property and
lives during storms and hurricanes by acting as a buffer against the winds and waves.
Harshest Threat: Humans
Mangrove trees survive harsh natural conditions, but
threats from pollution and industry are an even bigger
problem. The land where mangroves live has often been
sold cheaply to businesses, which cut down many of the
trees. Sewage, weed-killers, and spilled oil are extremely
unhealthy for the mangroves.
As human activity around mangroves increases, more and more mangrove forestland is
lost. Dredging coastal areas and filling them in to make them suitable for building also
leads to destruction of mangroves. Artificial dikes cause long-term flooding that the
mangroves simply cannot handle. Thousands of acres have been cut down to make
room for the artificial ponds required by the shrimp industry.
Even the beauty of mangrove swamps threatens them. More tourists are coming to see
them, and with more tourism comes more garbage, along with air and water pollution.
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A Global Rescue Mission
Mangroves do not recover quickly from severe damage. This
mangrove forest in Honduras never recovered from the destruction
caused by the development of a shrimp farm.
According to some experts, half of the world’s mangrove swamps
have already been lost. So is all hope lost? Not at all. Environmental
activists are raising awareness of mangrove swamps’ unique
features and benefits around the world. They are trying to pass laws
to protect mangroves, and to encourage people to stop buying
shrimp grown in areas where mangroves once used to thrive.
The Mangrove Replenishment Initiative (MRI) could make a difference around the
world. One of MRI’s goals is to research and develop effective ways of replanting
mangrove forests. Growing these trees from seeds, from the ground up, is difficult. It’s
not enough to drop seeds and hope for the best.
The Forestry and Agriculture Organization of the United Nations is also involved in
studying ways to preserve mangroves. In Belize, where increased population and the
construction of homes threatened mangrove swamps, an educational workshop helped
to raise the residents’ awareness of the true value of the mangroves. A similar program
might be introduced in Malaysia.
In Florida, the Mangrove Trimming and Preservation Act
makes it illegal to use poisonous chemicals in mangroves.
People need a permit from the government before they
can disturb mangroves in any way.
What Can You Do?
How can you do your part to save the mangroves and the rich variety of life that
depends on them?




Find out more at your local library, or go online.
Get people interested in mangroves. (Weird trees, endangered animals, native
populations in trouble—shouldn’t be too hard!)
Don’t buy shrimp raised on former mangrove land. Be an all-around friend to the
environment.
Donate money to the Mangrove Action Projects.
Exploitation and conservation
The United Nations Environment Program estimated that shrimp farming causes a
quarter of the destruction of mangrove forests.
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Grassroots efforts to save mangroves from development are becoming more popular as
the benefits of mangroves become more widely known. In the Bahamas, for example,
active efforts to save mangroves are occurring on the islands of Bimini and Great
Guana Cay. In Trinidad and Tobago as well, efforts are underway to protect a mangrove
threatened by the construction of a steelmill and a port. In Thailand, community
management has been effective in restoring damaged mangroves.
Approximately 35% of mangrove area was lost during the last several decades of the
twentieth century (in countries for which sufficient data exist, which encompass about
half of the area of mangroves).
It has been cited that Mangroves can help buffer against Tsunami, cyclones, and other
storms. One village in Tamil Nadu was protected from Tsunami destruction - the
villagers in Naluvedapathy planted 80,244 saplings in order to get into the Guinness
Book of World Records. This created a kilometre wide belt of trees of various varieties.
When the Tsunami struck, much of the land around the village was flooded, but the
village itself suffered minimal damage.
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Mangrove Removal Regulation
Mangrove trees along natural and many artificial water bodies are protected from
removal. Mangrove trees are protected from removal by Dock and Shoreline
regulations, the natural waterway buffer requirement and the Tree Protection Code. In
many cases, mangrove trees can not be removed without first obtaining a vegetation
removal permit from Lee County. Mangroves are typically located in wetlands. Impacts
or removal of mangrove wetlands may require permits from state and federal agencies
Mangrove Pruning Regulation
Since July 1, 1996, Lee County has generally not been involved in the regulation of
mangrove tree pruning. Below are state agencies that permit mangrove pruning per the
Mangrove Trimming and Preservation Act (Florida Statutes Sections 403.9321403.9333) - www.leg.state.fl.us/Statutes/
FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION - (DEP)
South Florida District Office
2295 Victoria Avenue, Suite 364
Fort Myers, FL 33901
Telephone (239) 332-6975
Fax (239) 332-6969
http://www.dep.state.fl.us/
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Florida Mangroves
Red mangrove
(Rhizophora
mangle)
The red mangrove is one of the
four mangrove species found in the
mangrove ecological community.
The other species within this
community are the white mangrove
(Laguncularia racemosa), black
mangrove (Avicennia germinans),
and
buttonwood
(Conocarpus
erectus). Scientifically, they are
distantly related and are only
grouped based on ecological
function within the community.
The mangrove community plays an important
role in tropical and subtropical regions of the
world. Different mangrove species protect and
stabilize low lying coastal lands and provide
protection and food sources for estuarine and
coastal
fishery
food
chains.
Mangro
ves
serve
as
feeding,
breedin
g, and
nursery grounds for a variety of fish, shellfish,
birds, and other wildlife. Mangroves also
produce 3.6 tons per acre of leaf litter per year
which benefit estuarine food chains. An
estimated 75% of the game fish and 90% of the
commercial species in south Florida depend on
the mangrove system.Their tall arching roots
called prop roots easily identify the red
mangroves. Prop roots supply air to the
underlying roots and provide support and stability to the red mangrove. They also trap
mud and silt that flows with the tide, thus gradually increasing the soil around them. They
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are found closer to the water than the other mangroves in the
community due to their high salt tolerance. The wood is used for fuel,
piling, crossties, and charcoal. The red mangrove is also known for its
large quantity of tannins found in the bark. Red mangroves range from
Daytona Beach and Cedar Key southward.
Waterfront development has strongly affected the habitat of mangrove
communities. Removal of these trees and the destruction of mangrove
wetland habitats endanger the natural systems of Florida's coastal
zone. The result of removal or damage to the mangrove communities
has affected Florida's coastal land by causing erosion and a decrease
in food at the base of the food chain supporting commercial fisheries.
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Identifying Characteristics
Size/Form:
The red mangrove is a tall tree that reaches 70' to 80' in height in
the tropics; however in Florida, it is characterized as a short bushy
tree reaching about 20' in height. It is characterized by its numerous
above ground roots called prop roots.
Leaves:
The persistent leaves are oppositely arranged, 3" to 5" long and 1"
to 2" wide. They are elliptical in shape, dark green on top, and paler
below. Leaf margins are smooth.
Flowers:
The flowers on the red mangrove are a pale yellow and appear in
the spring.
Fruit:
The leathery fruit is a rusty-brown conical berry. Before it falls from
the tree, one seeds germinate and send down an initial root, 6" to
12" long. When the fruit falls this root lodges in the soil and the top
begins to grow immediately. This is a unique plant adaptation to the
wet environment.
Bark:
The thick gray to gray-brown bark is ridged and scaly.
Habitat:
The red mangrove grows in brackish areas along creeks, bays, and
lagoons.
Black mangrove (Avicennia germinans)
Black mangrove is a communal species that plays a key
role in the mangrove ecosystem. It contributes to the
ecological community by trapping in the root system debris
and detritus brought in by tides. The community is valued
for its protection and stabilization of low-lying coastal lands
and its importance in estuarine and coastal fishery food
chains. Black, white, and red mangroves serve as feeding,
breeding, and nursery grounds for a great variety of fish,
shellfish, birds, and other wildlife.
Black mangrove grows in coastal tidal areas throughout
the tropics and subtropics of America and Africa. It grows
closer inland from the shore. There it can be reached only
by high tides. It is found on the gulf coast of Florida from
Cedar Key to Key West and back up to St. Augustine on
the Atlantic side. Southwest Florida islands contain the
most concentrated area of mangroves. The tree becomes
shrubby toward the north of its range due to the cooler weather. Freezing temperatures
prevent the range from extending northward.
19
The wood is dark-brown to nearly black. It is preferred for its strong, heavy, and hard
qualities. Black mangrove wood has been used as posts, fuel, and for marine
construction. Black mangrove contains tannin in the bark and has been used to prepare
leather products.
Black mangroves bloom in June and July with white flowers. When in bloom, black
mangrove nectar is used for "mangrove honey" production. This honey is of very high
quality. Considerable quantities were made in the United States until about 1895.
Hurricane destruction of the best forests decreased honey production. In recent years,
there has been renewed interest in this product.
Black mangroves can be easily identified by the numerous pencil-like breathing tubes,
called pneumatophores, which grow vertically from the mud to just above the highest
sustained water level. Like the prop roots of the red mangrove (Rhizophora mangle),
these provide air to the underground and underwater roots. Unfortunately, the diverse
natural community provided by the mangrove forest is declining due to the invasion of
overpowering plant species, such as the Brazilian pepper, and urban development.
20
Identifying Characteristics
Size/Form:
Black mangrove is a small to medium-sized tree that reaches
heights of 50'. It is small and shrub-like toward the north end of its
range.
Leaves:
The leaves are simple, oppositely arranged, persistent, and 2" to 4"
long by ¾" to 1 ½" wide. The oblong shaped leaves usually have
shiny upper surfaces coated with salt crystals while the underneath
surface is hairy. The leaf base is wedged and the leaf tip is rounded.
The leaf margin is smooth and sometimes slightly rolled down along
the side edges.
Fruit:
The egg-shaped capsule is green and 1 ½" long by 1" wide, has
splits along two edges, and contains one seed.
Bark:
The dark-brown bark has long, vertical furrows between flat, scaly,
squarish blocks. The bark sloughs off to reveal an orange-red inner
bark.
Habitat:
Black mangrove grows in the wet soils of coastal high-tide shores of
Florida in the mangrove ecosystem.
White mangrove (Laguncularia
racemosa)The white mangrove is one
of four mangrove species in the mangrove
community. The other species are the red
mangrove (Rhizophoria mangle), black
mangrove (Avicennia germinans), and
buttonwood
(Conocarpus
erectus).
Scientifically, they are distantly related
and are only grouped based on ecological
function within the community.
White mangroves range from Volusia
County and Levy County southward. The
mangrove community plays an important
role in the tropical and subtropical regions
of the world. Different mangrove species protect and stabilize low lying coastal lands
and provide protection and food sources for estuarine and coastal fishery food chains.
Mangroves serve as feeding, breeding, and nursery grounds for a variety of fish,
shellfish, birds, and other wildlife. Mangroves also produce 3.6 tons per acre of leaf litter
per year, which benefit estuarine food chains. An estimated 75% of the game fish and
90% of the commercial species in south Florida depend on the mangrove system.
21
The white mangrove is easily differentiated from other mangrove species by its leaves
and root system. The leaves are rounded at the base and the tip and are smooth
underneath. Each leaf has two glands, called nectarines, at its base that excrete sugar.
Many
insects
feed
on
the
excreted
sugar.
Depending on habitat conditions, the white mangrove may possess pneumataphores
and/or proproots. Pneumatophores are cone-shaped extensions of the root system
protruding from the ground. Pneumatophores are thought to function as the trees'
means of obtaining oxygen for the roots during flooded conditions. Prop roots are tall
arching roots originating from trunks and branches. The white mangrove is fast growing
in
fertile
habitats.
A common belief that the
mangroves build land is
usually not true. However,
after they colonize newly
formed sandbars and
embankments, their roots
may
entrap
and
accumulate soil, helping
to stabilize soil during
rough weather.
Identifying Characteristics
Size/Form:
The white mangrove is a small low sprawling shrub or tree that reaches
40' to 60' in height. It is characterized by its narrow rounded crown.
Leaves:
The persistent leaves are oppositely arranged and are 1" to 3" long. The
leaves are leathery and possess small glands on the bottom of the leaf
towards the outer edges.
Fruit:
The leathery fruit is a reddish-brown drupe that contains a dark red
seed.
Bark:
The 1" thick reddish-brown bark is ridged and scaly.
Habitat:
White mangrove grows in areas where tides may be high and also in
lagoons.
22
Buttonwood
(Conocarpus
erectus)Buttonwood is a shrubby
mangrove tree that has a picturesque
appearance when exposed to constant
seashore winds creating an attractive
addition to the beach landscape. Its
name refers to the red-brown, conelike fruits. Buttonwood is usually low
branching and multi-trunked. It is
native to Florida's mangrove forest
ecosystem.
As a tropical tree, buttonwood does not grow north of Florida's Cape Canaveral and
Cedar Key. From this northern limit, buttonwood growth in the brackish tidal lagoons
and bays ranges to the Florida Keys and Bermuda, the West Indies, Central and South
America, and western Africa. Buttonwood is highly
tolerant of full sun, sandy soils, salty conditions, and the
soils of shaded and moist oak hammocks. They are
found on the edges of salt flats, rocklands of the Florida
Keys, borders of fresh and brackish marshes, edges of
hammocks, sometimes on spoil and other disturbed
areas in South Florida.
Buttonwood is often used for seaside landscaping. The
wood was used for firewood, cabinets, and making
charcoal. It is very strong wood and ideal for smoking
meats and fish because it burns slowly and releases generous quantities of heat.
Buttonwood is tough and long lasting in the landscape. It can withstand the rigors of
urban settings and makes a durable street or parking lot tree.
23
Identifying Characteristics
Size/Form:
Buttonwood is a small tree that seldom reaches heights of 40'. It is
usually small and shrub-like.
Leaves:
The leaves are simple, alternately arranged, persistent, and are 1" to
4" long by ½" to 1 ½" wide. The oblong shaped leaves usually have
dark, shiny green upper surfaces while the underneath surface is
paler and smooth with silky hairs. The leaf base is wedged with a pair
of marginal glands. The leaf tip is tapering and the margin is smooth.
Fruit:
The fruit is a tiny reddish, leathery drupe. The scale-like drupes are
borne in heads that resemble a cone that is 1" in diameter.
Bark:
The dark-brown to black bark has irregular fissures that form flat,
interlacing, scaly ridges.
Habitat:
Buttonwood grows in the silty, muddy shorelines of tidal bays and
lagoons, commonly landward of the fringe of mangrove community
and above high tides. They are also found on the edges of
hammocks, salt flats, marshes, and sandy rocklands.
Florida Mangroves Zonation
24
Activity: The Coast Protectors
Duration: 1 hour
Objectives

Students construct models to demonstrate how mangroves help protect
shorelines and contribute to the growth of the Florida peninsula.
Materials













Photos of different mangrove habitats and species
3 copies of the Mangrove Concentration worksheet
3 sheets cardstock
Glue
2 large, shallow trays (4‖x12‖x18‖ – a baking or roasting pan)
10 Sheets of Styrofoam (about ½ inch thick)
Sand (enough to cover the bottoms of the trays 1-3 inches)
1 package red pipe cleaners
1 package black pipe cleaners
1 package white pipe cleaners
1 package green pipe cleaners
2 strips of Styrofoam or plastic, cut to fit into the tray and at least as deep
(4‖x12‖)
Additional small pieces like leggos or jewelry boxes to represent homes,
buildings, etc.
Procedure
1. Before class begins, make the Mangrove Concentration cards
 Glue or copy the ―front‖ (adaptation descriptions) to a sheet of cardstock
and cut out cards
 Cut out the ―back‖ (mangrove species) and paste to the back of the front
cards as follows:
o 1, 5, 9, 13 – red mangrove
o 2, 6, 10, 14 – black
o 3, 7, 11, 15 – white
o 4, 8, 12, 16 – buttonwood
 Repeat to make 2 more sets of cards
 Lay the cards on the desk for 3 groups, with the ―front‖ face up (the side
with the adaptations
2. Show students the mangrove photographs. Discuss the types of mangroves
common in Florida and the characteristics of each species.
 What are the 4 species of mangrove in South Florida?
25
3.
4.
5.
6.
7.
8.
o White, black, red, and buttonwood.
o The buttonwood is not a ―true‖ mangrove
 How are these species alike or different?
o Each mangrove species have their own adaptations that help them
to survive in the saline environment.
o Also, the mangroves exhibit zonation, such that they are found in
different areas on the coast (the reds are in the water and the
buttonwoods are more upland, away from the water).
Divide the class into 3 groups. Tell the students that they will play Mangrove
Concentration.
 Set each group in front of one set of cards.
 Tell students that they must take turns flipping two cards at a time. If the
cards match, they player keeps the cards. If they don’t match, both cards
must be flipped back over.
 When all the cards have been matched, have students present the
mangrove characteristics/adaptations described on the cards for each
species.
Discuss the similarities and differences among the types of mangroves.
Inform students that they are going to construct 2 models to demonstrate the
roles mangroves play in the coastal community.
 One model will include simulated mangroves and the other will not.
 Encourage students to contribute ideas for building the models.
In the bottom of BOTH trays construct shoreline topography out of the Styrofoam
 One end represents the coastline; the other end, inland.
 Add enough washed coarse sand to cover the shoreline topography to a
depth of 1-3 inches.
Randomly place several small boxes of leggo pieces inland to represent condos,
homes, hotels, etc.
On one model, use the colored pipe cleaners to simulate the 3 types of
mangroves and buttonwood.
 When adding mangroves to the model, make sure they are securely
inserted into the Styrofoam. The ―black mangroves‖ may have to be glued
or taped before adding sand.
o Have students assist in making the pipe cleaner mangroves as
many will be necessary
 For red mangroves:
o Twist several red pipe cleaners together at their midpoint to form
the trunk
o Spread the ends of individual pipe cleaners apart to form prop
roots.
o Add a coastal fringe of red mangroves to the model (from one side
to the other) by interlocking the simulated prop roots and pressing
them into the sand along the shoreline of the model
 For the black mangroves:
26
o Using the black pipe cleaners, use the same technique as for the
red, but spread the simulated roots apart and flatten them like the
spokes of a wheel.
o Add pneumatophores by twisting short pieces of pipe cleaner
around the flattened roots so that they project upwards.
o Place the black mangroves in a band behind the red mangroves by
pressing the roots into the sand so the pneumatophores project
above the surface.
o Black mangroves may have to be made and added to the
model first before adding the sand.
 For white mangroves (white pipe cleaners) and buttonwoods (green pipe
cleaners):
o Push the twisted end of a bunch of pipe cleaners into the sand.
o Add a band of white mangroves behind the black mangroves
o Add a band of buttonwoods behind the whites
 The entire coastal fringe of simulated trees should be about 4-6 inches
across.
 To simulate branches on all the trees, simply spread apart and arrange
the tops of the twisted pipe cleaners.
9. Add water to the shoreline end of both models, to about 1/3 the depth of the tray.
 For the mangrove model, be sure the water barely covers the lower part of
the prop roots of the red mangroves and covers all of the roots of the
black mangroves, so that only the pneumatophores project above the
water.
10. Place a small piece of Styrofoam or plastic in the water end of each tray.
 Move it back and forth to simulate waves
 Push it strongly toward the beach to simulate storm surge
11. Have students observe, record, and discuss the effects.
 What were the differences between the two models?
 When waves and the storm surge were simulated, what did you observe?
 What effect did the mangroves have in the model?
 What implications does this have for our coastlines?
 What do you think would happen if we lost all our mangroves?
Activity adapted from Discover a Watershed.
27
Mangrove Concentration Cards (Front)
1
2
3
4
Largest leaf
With
silvery Glands on petiole
underside of leaf
Salt
excreted
through leaf
5
6
7
8
Prop roots
Pneumatophores
Smallest
mangrove
9
10
11
12
Salt excluder
Salt excretion
Salt extruder
Grows in higher
less saline habitat
13
14
15
16
Cigar-like
propagules
Lima bean-shaped Triangular
propagule
propagule
true Rough bark in older
trees
Button-shaped
seed
28
Mangrove Concentration Cards (back)
Red Mangrove
Black Mangrove
White Mangrove
Buttonwood
Red Mangrove
Black Mangrove
White Mangrove
Buttonwood
Red Mangrove
Black Mangrove
White Mangrove
Buttonwood
Red Mangrove
Black Mangrove
White Mangrove
Buttonwood
29
Activity: Mangrove Field Study
Duration: 1.5 hours
Objectives

Journey outside the classroom to a mangrove forest where students can
investigate some special mangrove characteristics.
Materials










5 tape measures
5 transects
5 Clipboards
Pencils
5 thermometers
Refractometer
Anemometer
5 Clinometers
Mangrove PowerPoint
Mangrove Life Cycles Data Sheet
Procedure
1. The week prior to conducting the activity, select a suitable mangrove site.
 This location should have 3-4 of the common mangrove species, and
demonstrate the community succession that is often found in mangrove
habitats.
 Also, be sure to check the tides and arrange to visit the site during low
tide, if possible.
2. Introduce students to mangroves. Lead a class discussion using the following
guiding questions:
 What makes mangroves different from other trees?
 What are some of the adaptations that allow mangroves to survive in salt
water?
 Explain why certain mangrove species are found closer to or further from
the shore.
 What are some of the benefits provided by mangroves?
 Why are mangroves a great habitat?
 Describe some reasons why it is important to protect mangroves.
3. Introduce the term ―propagules‖ to the students and discuss the mangroves’
reproductive strategy
 Mangrove trees develop seeds known as propagules that sprout while on
the tree. They are long and pencil shaped. When the propagules ripen,
30
4.
5.
6.
7.
8.
9.
they fall off the tree and either land in the soft mud below or into the water
where it is carried away.
 Propagules are buoyant, and thus able to float vertically in the water.
They can travel from several days to months in the water until it finds a
shallow area to settle.
 Once a propagule is planted, it begins to develop prop roots, which help to
stabilize the tree in the water. As the mangrove grows, the prop roots
allow for sand, detritus and other sediments to collect, which makes the
location more suitable for settlement for other wandering propagules.
Eventually a mangrove forest (if next to the shore) or a mangrove island (if
offshore) forms.
Explain to the students that today they will have the opportunity to participate in a
Mangrove Field Study where they will observe and measure some of these
special mangrove characteristics.
Divide students into 5 teams. Give each team a tape measure, thermometer,
clipboard, clinometers, transect, and data sheet.
Tell students that each team will conduct its own field study. As a part of the field
study, groups will:
 Choose an area that shows mangrove succession
 Record the mangrove species observed
 Run a transect line to measure the length of the area and identify the
distance of each species from the water
 Record the temperature, salinity, and wind speed
 Record the average height of each species’ canopy
 Locate and measure the growth of a seedling
 Describe the organisms observed in their mangrove area.
Take the students to the designated areas.
 Demonstrate how to use the clinometer and how to measure the
seedlings.
 Direct each group to:
o Locate an area
o Complete their measurements and record their data.
 Each member in the group must participate.
After returning to the classroom, allow each group about 10 minutes to review
their results.
Allow each group to present their conclusions on whether they think the area
they surveyed is a healthy habitat. Students should consider the following
questions:
 What are some indicators of a healthy mangrove ecosystem?
 What are some ways that a damaged mangrove area can be restored?
 How would you bring awareness about this fragile ecosystem to the
public?
31
Mangrove Data Sheet
Group Members ______________________________________________
Date________________________________________________________
Field Work
A. Site Selection – select an area that has multiple species of mangroves, and if
possible, shows zonation. Area should also have several seedlings present.
 Be sure it is an open space where your group can conduct the field work
safely.
 Avoid areas that are too muddy.
B. Site Description
 Write a brief, general description of your site. Where is it located? Is the
area diverse (what other plants or organisms can you see besides
mangroves)? Is it high or low tide? Sunny or shaded? Describe anything
that you see.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
_____________
C. Plants
 Conduct a survey of the plants in your site area, including the mangroves
and any other plant species that might be a part of your site.
 When measuring height, take measurements from 5 trees and calculate
the mean
32
Tree Height
1 2 3 4 5 Mean
Descriptive Features
Leaf
Trunk
Root
Other Plant Mangroves
Species
Species Name
D. Site Profile
 Use the transect to measure the entire length of your site from the
mangroves furthest in the water (your origin) to the last mangrove in
shore.
Length of site area: _________

Measure the length of each mangrove zone starting with those closest to
the water.
Species 1: ______________________
Species2: ______________________
Dist. from origin: ____
Zone length: ____
Zone length: ____
Dist. from origin:____
Species 3: ______________________
Species4: ______________________
Dist. from origin: ____
Zone length: ____

Zone length: ____
Dist. from origin:____
Sketch the study area and its vicinity. Make sure to include the relative
measurements of the zones in your drawing, as well as symbols to
represent each species present.
33
Symbols Key
Water
Comments__________________________________________________
___________________________________________________________
___________________________________________________________
__________________________
F. Physical Factors
 Measure temperature, salinity, and wind speed
 Take each measurement 5 times, and then calculate the mean values.
Air
Temperature
Water
Temperature
Soil
Temperature
Salinity
Wind Speed
1
2
3
4
5
Mean
34
E. Organisms
 Conduct a survey of the animals and different organisms you observe in
your site area
Species
Name
Location
Found
External Features
Behavior
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
For location, describe where you find the organisms, e.g. above leaf, below leaf,
on trunk, on mud surface, in leaf litter, in water, in crevice, etc…
F. Seedling Growth
 Locate mangrove seedlings in your site area (see picture).
 Starting from the substratum, measure the height of the hypocotyls or zero
node, followed by successively higher nodes along the main stem until
reaching the base of the apical node. This is measured as the last in the
present sequence.
 Count the heights of all the nodes along the main stem from the
substratum to the apical node.
 Calculate intermodal extension by estimating the difference between the
height of the node above, minus the one below.
35



Plot the data in a graph with node number (x-axis) vs. intermodal
extension (y-axis)
Repeat with 5 more seedlings.
If your seedlings have more than 6 nodes, extend the chart on the back.
36
Node 2
Node 3
Node 4
Node 5
Node 6
Inter-nodal
Height
Inter-nodal
Height
Inter-nodal
Height
Inter-nodal
Height
Height
Inter-nodal
Node
Count
Inter-nodal
Seedling
Node 1
Height
Height
–
substr
atum
to zero
node
1
2
3
4
5
Internodal Extension
Key to
Seedlings
Node Number
37
Resources
http://www.globio.org/glossopedia/article.aspx?art_id=39
http://www3.leegov.com/DCD/Environmental/Mangroves.htm
http://en.wikipedia.org/wiki/Mangrove
http://water.epa.gov/type/wetlands/mangrove.cfm
http://www.ncl.ac.uk/tcmweb/tcm/mglinks.htm
http://www.wettropics.gov.au/pa/pa_mangroves.html
http://www.floridaplants.com/horticulture/mangrove.htm
All images are taken from Google Images.
38