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What are Mangroves?
Mangroves are tropical plants which are found along much of the
world’s tropical coasts. They grow in loose, wet soils,
salt water, and are periodically submerged by tidal flows. Their
distribution throughout the world is affected by climate, salinity
of the water, fluctuation of the tides, type of soil in the area
and, more recently, by development of tidal wetlands for residential
use as well as industrial, i.e. shrimp farms.
Florida has 3 of the 50 species of Mangroves found throughout
the world.
Red Mangrove (Rhizophora Mangle)
- The Red Mangrove - also known as the “Walking Tree” -
can be identified by the trunk roots which have a reddish color
to the bark.
- They have shiny deep green leaves which are lighter on the
underside. The leaves measure 1-5 inches in length and are broad
and blunt
at the tip.
- Their prop roots - arching out from the trunk and the
branches, produce additional roots and give the tree the
appearance that
it is walking into the water.
The red mangroves are the first flora to populate
a volcanic island in the Galapagos Islands of Ecuador.
The survival of this tree in brackish
water is a direct result of the tree’s ability to adapt to
its environment by using its roots to remove 99/100ths of the salt
from the water it drinks.
Red Mangrove tissue samples, when analyzed, revealed that the salt
content of the water in those samples had approximately 1/100th
of the salt found in the water in which the trees were growing.
The
Red Mangrove produces bud-like growths which grow into torpedo-shaped
seedlings known as propagules. These seedlings eventually fall
into the water and either take root in the ground below or
float and drift with the tides until suitable ground is found.
A red
mangrove propagule can drift for a year before rooting and
producing a tree.
Black Mangrove (Avicennia Germinans)
Black Mangroves, larger and taller than the Red
and White Mangroves because of their
age, they are found upland of
the Red Mangroves
at higher elevations. These old timers are the most cold tolerant
of the three species found in Florida. They can readily be identified
by:
- Looking at the ground. These trees are surrounded
by pneumatophores
(prounounced “new-mat-afores”) – stick-like structures
(growths) - pointing
skyward from the soil surrounding the trunk of the tree. Pneumatophores
come
from the roots of the Black Mangroves and help the tree to breathe.
This species
of mangrove generally grows in areas where the soil is saturated
with water –
without the pneumatophores, which act like a diver’s snorkel,
the tree would
lack the oxygen it needs to survive.
- The bark of a Black Mangrove
is dark.
- The leaves are shiny dark green on the top,
oblong and pointed at the tip.
The undersides of the leaves are a dull green color with short
dense hairs -
glands - which excrete salt – the leaves serve as a back-up
system for ridding
the Black Mangrove of the salt that has not been excreted by
the roots.
When early settlers came to Florida they harvested salt from
the Black
Mangrove leaves.
- The seedlings produced by these trees are light
green in color and shaped
like large coins.
Black Mangoves surrounded by pneumatophores
which provide their oxygen
when they are submerged by tidal flows.
White Mangroves (Laguncularia Racemosa)
White
Mangroves, usually found at higher elevations (further upland than
the red or black mangroves) can easily be identified by:
- Their leaves
which are light green in color, approximately 3 inches long,
rounded at both ends – often having a notch in the tip.
- At the base
of their leaves, where the leaves meet the stems, you will
find two
bumps. These bumps are glands which excrete the salt found
in the water.The seedlings of the White Mangrove are pod-shaped,
about the size of a nickel
and whitish in color.
Mangrove Functions and Values
- Mangroves trap and
cycle various organic materials, chemical elements, and
important nutrients in the coastal eco-system.
- Mangroves
provide one of the basic food chain resources for marine organisms.
The leaves of mangroves last for approximately a year
before falling into the water where bacteria and fungus decompose
the leaves – these leaves form the base of the food chain.
The mixture of decaying plant material, soil, water, fungus and
bacteria makes up Detritus (pronounced “di-tri-tes”)
which provides food for marine organisms – i.e. crabs, shrimps,
oysters, claims, anchovies, mullets. These marine species in turn
provide food for larger species, i.e. Snook, Seatrout, Red Drum
and Pinfish, Mangrove Snapper, Tarpon, which in turn provide food
for Bottle Nosed Dolphins, Bull Sharks, Alligators, pelicans, Great
Blue Herons, Egrets, Wood Storks, Eagles, Osprey – and
humans.
- Mangroves
provide physical habitat and nursery grounds for a wide
variety of marine organisms, many of which have important
recreational
or commercial value. For example, the pneumataphores
of the Black Mangrove provide safety for many marine animals,
sheltering
crabs,
shrimp, fish and clams, protecting many from predators.
- Mangroves
serve as storm buffers by reducing wind and wave action in
shallow shoreline areas.
- Mangrove seedlings unlike other
plants whose seedlings need to be germinated, are alive and
ready to grow. The moment
they are
dropped from the parent plant they have the ability
to take root and produce trees.
An estimated 500,000
acres of mangroves remain in the coastal areas of Central and
South Florida. It is estimated that
approximately 80% are under governmental or private
ownership or control
for conservation and preservation purposes.
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