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Mangrove Forests

Intermediate and Senior Contestants should study the following description to prepare for the Ecosystem Quiz station in the Florida 4-H Annual Ecology Contest

Contents Overview and History……………………………………………………………………………2

Environmental Factors…………………………………………………………………………...3

Community Types and Zones……………………………………………………………………7

Plants of Florida’s Mangrove Forests……………………………………………………………9

Wildlife…………………………………………………………………………………………..14

Human Impacts…………………………………………………………………………………..19

Summary…………………………………………………………………………………………20

Links to learn more………………………………………………………………………………22

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Overview and History

The Florida mangrove ecological community includes four tree species collectively called mangrove: red mangrove (Rhizophoa mangle), black mangrove (Avicennia germinans), white mangrove (Languncularia racemosa) and buttonwood (Conocarpus erectus L.) (see Figure 1). Scientifically, they are only distantly related but they share special adaptations that allow them to flourish in an environment of salt and tidal floods, where no other trees can survive.

Mangrove forests are found in tropical and subtropical tidelands throughout the world. In Florida, mangroves occur in coastal areas from St.Augustine on the Atlantic southward, and up the Gulf Coast to Cedar Key. Killing frosts keep mangroves from growing any farther north and the salt marshes of northern Florida transition to mangrove forests as you travel further south into milder climates. Extensive mangrove forests are found at the southern tip of Florida, including Ten Thousand Islands (150,000 acres), one of the largest mangrove swamps in the world. Freeze-stunted black mangroves are also found in Louisiana and Texas. The red mangrove was imported from Florida to Hawaii in 1902 where it’s now considered a pest.

Figure  1:  (Left  to  Right)  Red  mangrove,  black  mangrove,  white  mangrove,  and  buttonwood  

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Mangroves play an especially important role as a marine nursery. Photosynthesis in mangrove leaves supports a complex food web that feeds young fish and shellfish, and their roots provide habitat and stabilize rich bottom sediments. Young shrimp, lobster, snook and some snapper must be protected and fed in the mangroves on their journey to adulthood. In all, over 200 species of fish use mangroves. The abundance of mangrove marine life helps to attract many other animals including over 200 species of birds, 21 species of reptiles, and 18 species of mammals.

Mangrove stabilizes the land by trapping and holding sediment. Wide buffers of mangroves can protect the shoreline from waves and reduce flooding damage from storm surges. They are critical in heavily populated, low-lying areas subject to hurricanes and typhoons. Removing the shield of mangroves in Bangladesh may have cost thousands of lives when typhoon storm surges rushed ashore unimpeded in 1970.

In the past, mangroves have been destroyed by development, alteration of water levels, and pollution. However, the links between mangroves, shore protection, seafood and tourism are now appreciated. The Florida legislature recognizes the ecological and economic value of mangroves and has passed laws to protect them.

Environmental Factors Why do mangroves flourish in some environments, but are totally absent in others? Some environmental conditions such as cold and high wave energy prevent them from growing, while other conditions that mangroves are adapted to, like salt and flooded soils, prevent competing plants from growing.

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Cold

Mangroves are adapted to many harsh environmental conditions, but don’t like cold weather. Specifically, they don’t grow well in climates with an annual average temperature of less than 66 degrees Fahrenheit, and freezing temperatures will damage or kill them. The range of Florida’s mangroves fluctuates with invasions of severe cold weather. For example, the series of devastating freezes of the 1980s that wiped out the citrus industry in north central Florida also killed mangroves as far south as Naples on the Gulf coast and West Palm Beach on the Atlantic coast. Although mangroves have been reported as far north as St. Augustine and Cedar Key, the northern mangroves are stunted and may only be present as a shrub form that sprouts from roots after freeze damage.

Wind, waves, and tides

Hurricanes are an important factor controlling the mangrove ecosystem of south Florida. Ninety-six tropical storms have affected Florida Bay since 1916, with a major hurricane hitting about every 30 years. Wind damage to foliage and severe erosion of sediments prevents mangroves from reaching their growth potential in areas with frequent, severe hurricanes. For example, in 1960 Hurricane Donna’s 180 mph and 12 feet storm surge ripped away the mangrove fringes of the keys in Florida Bay. Some scientists believe that mangroves in hurricane prone area have evolved to reach their maximum productivity in about 30 years.

Mangroves grow best in protected environments with low wave energies. Areas with heavy wave action are not suitable for mangroves because waves destroy their shallow root system, prevent seedling establishment, and prevent the buildup of fine sediments. Mangroves are

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Figure  2:  Hydrogen  sulfide,  or  H2S,  is  a  very  toxic  mixture  that  can  be  very  harmful.  

found in area protected from waves by reefs, shell islands, bays and tidal rivers.

On the other hand, the movement of tidal water in and out of the mangroves is key to their survival. Tides remove toxic compounds like hydrogen sulfide (H2S) that build up in flooded soils. Hydrogen sulfide is responsible for a rotten egg like smell that can sometimes be detected at low tide in mangroves. Tides also prevent the buildup of salt and re-supply the system with oxygenated water.

Fine sediment brought into mangroves with the tide can be trapped by the mangroves root system. Over time, this may result in the build-up of land islands around the trees. For this reason some people describe mangroves as land builders. Mangrove trees depend on these sediments to provide a place to reproduce and regenerate new trees within the community.

Salt

Mangroves are halophytes or salt-tolerant plants. Their adaptation to saltwater allows them to flourish where no other trees can survive. They can grow quite well in fresh water, but their special ability to regulate salt allows them to out-compete most other trees in the tropical and subtropical tidal environment. Mangroves prevent excessive amounts of salt from damaging their tissues by restricting the amount of salt that can enter through roots, expelling salt crystals through

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transpiration, growing a thick cuticle to restrict salt absorption, or by salt excreting glands.

Scientists studying the pollen and spores from sediment buried in the past in Florida Bay have discovered that mangroves expanded their range when natural and manmade events decreased freshwater flow from the Everglades and increased salinities.

Anaerobic Soils

Water on top of soil blocks oxygen from entering. Tree roots and many of the soil organisms need oxygen for respiration. Under flooded conditions they will use up the soil oxygen and it will become anaerobic (without oxygen). Wetland plants, including mangroves, have adaptations for supplying roots in wet soils with oxygen. Red mangroves

have prop roots that grow above the water from the base stem and drop roots that grow down from the branches. Both prop and drip roots have small above ground pores called lenticels and spongy passages called aerenchyma (See Figure 3) that transport

oxygen from the air to the root below the ground. The roots of black mangroves

have special structures called pneumatophores that stick out of the soil like hundreds of fingers. At low tide, air travels through the aerenchyma of the pneumatophore into the below ground roots. When mangrove forests are removed, for example by hurricanes, soils return to a less productive anaerobic condition.

Figure  3:  Arenchyma  

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The mangrove’s environment of anaerobic soils and tidal floods present reproductive challenges. To meet these challenges, similar reproductive adaptations have been developed in the Red, Black, and White mangroves.

These mangroves have floating seeds that germinate while still attached to the mother plant. Actually, because the mangrove embryo doesn’t develop into resting seed-stage, but continues its development into a plant while still on the tree, it’s referred to as a propagule instead of a seed. This process is celled vivipary and it gives the mangrove propagule a head start before they are dropped into the harsh coastal environment. Because mangrove propagules conditions. White mangrove propagules can survive for several months and red mangrove propagules can survive for over year.

Community Types and Zones

Some of Florida’s mangrove forests are nearly 80 feet tall while others are more of a bushy-scrub than a forest. These differences are the result of different environmental conditions, such as topography, type of growing surface (rock, silt, sand), tidal action, freshwater inputs, nutrient availability, and climate. Although mangroves grow in a wide range of environmental condition, they have been classified into 4 major types: riverine, fringe, basin, and dwarf.

Community types

Riverine mangroves occur along tidal rivers and creeks and may be several miles inland from the coast. They receive nutrients from upland and estuarine sources, and fresh water flushing lowers the salt stress. These favorable conditions make the riverine mangrove forest very productive and trees they may grow over 80 feet tall.

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Growing conditions for fringe mangroves are less favorable and trees will seldom grow to half the height of those in a riverine environment. Fringe mangroves form a thin boarder along protected shorelines. Examples are the mangrove forests lining the Keys and Ten Thousand Islands. They receive little freshwater or nutrients from the land, and are vulnerable to high winds. Many of the small islands are actually over washed on a daily basis during high tide. Basin mangroves are located inland from fringe and riverine mangroves in depression basins. They are only flushed by infrequent extreme ride events. The resulting stagnant, salty conditions exclude red mangroves and limit the growth of black and white mangroves to less than 30 feet high.

Dwarf mangroves may only grow to 5 feet tall in 50 years. The stunted growth can be the result of extremely salty conditions, severely nutrient poor environments, or colder climates.

Zones

In general, the 4 species of mangroves sort themselves into the tidal zone where their adaptations give them a competitive advantage. For example the stilted, lenticel covered roots of the red mangroves allow them to grow in the deepest part of the tidal zone and they dominate the fringe community. In contrast, the pneumatophores of the black mangrove are too short to function well in a zone of high tidal fluctuation. But they are better adapted to survive the higher levels of H2S that occur in the more landward basin community that has less tidal flushing. White mangroves are also tolerant of high H2S and salt, but their seedlings grow best in high light zones, such as openings created by lightning fires or wind damage. Buttonwoods are the least tolerant of salt and they are usually upland of the tidal zone and frequently transition into the tropical hammock. In addition to adaptive based zones, the smaller propagules of the black and white mangroves are

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more likely to wash further up the tide zone than the long, bottom dragging, and red mangrove propagule. Mangrove zones are a useful concept based on observations and ecological principles. However, in the complex, changing, and chaotic coastal environment the different species are frequently observed “out of place.”

Plants of Florida’s Mangrove Forests

The diversity of plants in mangroves is low compared to other ecosystems. Few plants can tolerate the harsh conditions of coastal tidal zones and the mangrove’s thick canopies can block most of the light from other plants. There are four species of trees that are included in Florida’s mangrove forests. While similar in many respects, each has special adaptations for their watery environment.

Red Mangrove- (Rhizophora mangle L.)

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Red mangroves are easily identified by their tall arching roots, called prop roots that give them the appearance of walking on water. These roots are adapted to supply air to the underground roots, as well as adding the stability of trees. The roots also have special cells which allow them to absorb mostly fresh water from salt water.

Leaves of the red mangrove are opposite,, egg shaped to elliptical, leathery and shiny dark green above and paler underneath. Leaf edges are smooth and somewhat thickened. Clusters of 3 to 4 pale yellow flowers can be seen in the spring.

Red mangroves grow further out in the water than the other mangroves and are usually flooded at high tide. They can root on intertidal surfaces such as oyster bed and sand bars forming “mangrove islands.”

New trees establish themselves further away from the original tress by a well-adapted reproductive process. In a process called vivipary, seeds sprout into torpedo-shaped seedlings called propagules, while still attached to the parent tree. Sprouts then drop to the ground or into the water it may either take root among the other mangrove roots or float with the current until it drifts on to suitable ground. Seedlings remain viable for long periods of time and can become established after floating as long as 12 months.

Black Mangrove- Avicennia germinans

Figure  5:  Leaves  of  red  magrove  

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Black mangroves can be easily identifies 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, these provide air to the flooded roots of some black mangroves can also filter out salt water, but much of their salt regulation is accomplished by salt excreting glands in the leaves. Black mangroves also tend to have dark bark, whereas bark of white mangroves is light. The drop roots and inner flesh of red mangrove may have a reddish tint.

As a result of this salt excretion, the upper surfaces of black mangrove leaves are frequently coasted with salt crystals. The leaves are simple, oppositely arranged, persistent, and 2” to 4” long by ¾” to ½” wide. The oblong shaped leaves usually have shinny upper surfaces 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 (See Figure 6).

Black mangroves bloom heavily in June and July with white flowers. During black mangrove bloom, beekeepers set up their hives to collect the nectar for production of “mangrove honey.” This honey is of very high quality. Considerable quantities were made in the United States until about 1895. Hurricane destruction of the best forests

Figure  6:  Leaf  of  black  mangrove  with  salt  crystals.  

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decreased honey production. In recent years there has been renewed interest in this product. The lima bean shaped propagule is green and 1 ½” long by 1” wide and has splits along two edges. Black mangroves grow closer to the shore where they are reached only by high tides. At the northern edge of their range, (St. Augustine on the east coast and Cedar Key on the Gulf coast), these trees are small and shrub-like. Larger trees up to 50 feet tall with a branch spread of 35 feet are found further south around Sanibel-Captiva Islands.

White Mangrove-Languncularia racemosa

White mangroves typically grow at the highest and driest part of the tidal zone. They may have peg and/or prop roots depending on habitat conditions, but most have neither. Peg roots are similar to the pneumatophores of black mangrove except they are shorter and stouter. The lower trunk has tiny lenticels along the bark to help bring in extra oxygen when water levels are high.

The bark and leaves of “white” mangroves are lighter than other mangroves. They are best differentiated from other mangroves by succulent, light green leaves which are rounded at the base and tip and smooth underneath. Glands at the base each leaf called nectaries excrete sugar and salt. Some insects feed on the sugar. Its flowers are greenish-white and produce good honey. The fruit is small, dry, leathery and ribbed. It contains a dark red seed, and like other mangrove propagules, it’s buoyant allowing it to float to new growing sites.

Figure  7:  White  mangrove  with  nectaries  

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Buttonwood-Conocarpus erectus

Buttonwood is in the same family as the white mangrove, but it’s often considered only as an associate of mangroves. Like white mangrove, it has salt glands on the leaves to expel salt and lenticels on the lower trunk to bring in extra oxygen. However, buttonwood is less tolerant of salty conditions that the “true” mangroves and therefore it grows further inland. Frequently it occupies a transition zone between the tidal mangroves and the tropical hammock (Figure 8).  

The “button” part of the name comes from the button-like appearance of the dense, rounded flower heads that grow in a branched cluster, and the purplish-green, round, cone-like fruit. The other three mangrove leaves are alternate, leathery, pointed at the tips, have smooth edges, and two glands at the base of each leaf. It is shrubby along the shore, but it takes on a tree form further inland. The wood of these trees is extremely dense and durable and was used for firewood, cabinets, and making charcoal. Old stamps and downed branches of buttonwood trees may lie along coastal beaches for decades before they decay.

Other plants of mangrove forest

Mangroves frequently border salt tolerant marshes that may include salt grass, black needle rush, spike rush, gulf cordgrass and glasswort. The landward fringes of mangroves can interface with seaside mahoe (a “naturalized” exotic), fan palm, coin vine, and nicker bean. Where sufficient light filters through the mangrove canopy, salt tolerant

Figure  8:  Leaves  of  buttonwood  

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herbaceous plants like the leather ferns, Spanish bayonet, sea blite, rubber vine and air plants can be found. The Powdery Catopsis (Catopis berteroniana) is endangered air plant of the Florida Everglades that has a slippery powder to attract insects. They slide into a water reservoir at the base of the plant and their decaying body supplies nutrients. Most invasive exotic species find mangroves too inhospitable to invade. However, Brazillian pepper and Australian pine can sometimes penetrate into black mangrove basin communities.

Wildlife

The dense foliage, maze of prop roots, and rich sediments of mangroves form an important habitat for a diverse wildlife community. The animals you may find there range from microscopic invertebrates to bull gators, and from the common fiddler crab to the endangered Florida panther.

Invertebrates

Prop roots that extend below low tide provide food, shelter, and attachment surfaces for small marine creatures without backbones (invertebrates). Some invertebrates that inhibit the submerged prop root “forest” are barnacles, sponges, oysters, snails, conches, shrimp, spiny lobsters, and crabs. Larvae of spiny lobsters may hide and feed among the prop roots for most of their juvenile life. The adults of course are highly sought after delicacy. Other invertebrates, like the tree snails, live in the above water parts of mangroves.  

Crabs are sometimes referred to as the “keystone” species of mangroves. They

Figure  9:  A  crab,  the  “keystone”  species  of  mangroves.  

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perform key functions that support the overall ecosystem. Two of the most important functions are stimulating the transfer of mangroves leaves to the rest of the food web and aeration of the flooded soils. While shredding and eating the mangrove leaf litter, they break it into smaller particles which are more readily colonized by bacteria and fungi. Some crabs like the mangrove tree crab reside in the canopy feeding primarily on red mangrove leave while other live in the mud flats eating dead leaves. Crabs burrowing in the mud flats allow oxygenated water to reach deeper sediments. This helps the flooded soils to “breath” and reduces the build of toxic chemical like hydrogen sulfide and ammonium.

Fish

Many young fish, like tarpon and snook, are spawned offshore but spend their nursery years among the mangrove roots. Mangroves are also important nursery areas for other commercially important fish like the gray snapper, spotted sea trout, and red drum. The submerged roots of mangroves provide protection and habitat diversity and their leaves state the food web. Mangroves leaves that fall into the water feed fungi, bacteria, and protozoa that in turn feed invertebrates, and they in turn feed juvenile fish. Of course the small fish attract larger picivourous (fish eating) fish like barracuda.

Different types of mangroves support different types of fish. For example riverine mangroves may contain freshwater bass and gar, especially during the rainy season when salinities are low. Fringe mangroves have higher salinities and attract marine visitors like drum and snapper. The stagnant pools of basin mangrove are low in oxygen and support fish like the mosquito fish that can breathe from surface air.

Reptiles and Amphibians

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The largest reptile in North America, the American crocodile, is making its last stand in the mangroves of south Florida. There are only about 500 remaining. Hunting in the past reduced their numbers and now loss of habitat threatens to eliminate them altogether. They may live over 70 years and reach lengths over 20 feet. Fortunately, they are shy of man and mostly eat crabs, turtles, fish, raccoons, and water birds. Interestingly, red mangrove seedlings have been found in their stomachs. Crocodiles can be distinguished from alligators by their more pointed snouts, raised tail scales, long exposed teeth and they can be found in salty water (see Figures 10.1-10.2). Alligators lack the salt-extracting glands of crocodiles and are unable to survive in salt water for extended periods of time.

Alligators are found in the less salty inland riverine mangroves. There they play an important part in keeping the mangrove creeks open. Where alligators have declined, the mangrove roots have grown together allowing the accumulation of debris, and many former mangrove creeks are now buttonwood stands.  

Other reptiles that inhibit mangroves are the mangrove water snake, several species of anole lizards, diamondback terrapin, Atlantic ridley’s and hawksbill turtles. The hawksbill gets its name from its sharp beaklike mouth. Because its shell is extremely valuable, the hawksbill

Figure  10.1-­‐10.2:  10.1(top),  American  crocodile,  the  largest  reptile  in  North  America.  10.2(bottom)  Alligators  tend  to  have  pointer  snouts  than  crocodiles.  

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has been hunted to the brink of extinction. The marbles plastic-like scutes, which cover its shell is the source of “tortoise shell” used in the making of jewelry, carved figurines and decorative ornaments. In the United States the worldwide demand for the shell, meat, leather, and oil contributes to its continued decline.

Few amphibians can tolerate the salty conditions of mangroves. Their porous skin allows osmosis of body fluids into the salty water and limits their ability to survive in salty environments. Osmosis occurs if two aqueous solutions of different salinity are separated by a semi-permeable membrane, like the porous skin of amphibians. Osmosis will cause water to pass through the membrane in the direction of the more concentrated solution. In other words, the salty water will suck the fresh water out of most amphibians.

Mammals

In addition to North America’s largest reptile, mangroves provide food and habitat for the Key Deer, the smallest race of North American deer (see Figure 11). Key deer are a miniature variety of the white tailed deer and are only found on a few islands of the Florida Keys. They generally weigh less than 50 pounds and are about 2 feet tall. During the last ice age (about 15,000 years ago) many animals migrated to Florida to escape the advancing glaciers. As more of the earth’s water was frozen into glaciers sea

levels dropped more than 100 feet lower than they are today. At that time the Keys were hills

and Florida Bay a flat forest. When the glaciers melted and sea level

Figure  11:  Key  Deer  

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rose, the deer that remained on the Keys had to adapt to the limited resources of the small islands.

Red mangrove is an important food source for the Key deer. They can drink some brackish water but most of the population is limited to the few Keys with significant permanent fresh water sources. In 1955 there were less than 50 Key deer left. Today they are protected under the endangered species act, but there are still less than 800 Key deer left in the world. Habitat loss and motor vehicles continue to threaten the remaining population.

Habitat protection is critical for the protection of endangered species and the Key Deer National Wildlife Refuge (NWR link) was established in 1957. Most of the Refuge uplands are located on Big Pine and No Name Keys. Unfortunately, much of the refuge is interfaced with suburban and urban land uses and deer must frequently cross roads. In order to reduce their attraction to roads, feeding Key Deer is prohibited. Also a slower night time speed limit is strictly enforced.

Another endangered mammal that isn’t seen very often, but is most frequently observed near mangroves in the Everglades, is the Florida panther. More common inhabitant is the bobcat, skunk, raccoon, and river otter. Two marine mammals that frequent mangroves are the bottlenose porpoise and manatee.

Birds

Mangroves provide the most elevated natural structure along much of the south Florida coast and attract over 200 species of birds. The list includes wading birds like the stilts, ibis and birds of prey like the eagle. The elevated trunk, limbs and foliage are used for resting, roosting, and nesting. In addition, the mangrove ecosystem support and attracts many fish, snails, crabs, shrimp, crayfish, and insects that birds feed on.

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Mangroves are critical nesting grounds for the brown pelican, roseate spoonbill, great blue heron, reddish heron, double crested cormorant, and Louisiana heron (tricolored heron)(Figure 12). During drought years many of the other birds that nest in the interior wetlands of south Florida find refuge and nesting in the coastal mangroves. The opportunistic mangrove cuckoo is known to take advantage of this abundant egg supply when the parents are away from the nest.

Human Impacts

About 20% of Florida’s historical mangrove habitat has been lost to human impacts. A mangrove in urban areas like Tampa, Marco Island, the Keys and Dade County have often suffered the greatest loses. While some of the loss is result of direct removal, oils, sediments, hydrological modifications and boat waves can be just as destructive.

The above ground roots of mangroves are essential adaptations to harsh natural conditions. However, they also expose mangroves to harmful human influences. The tiny lenticels that must “breath” for the flooded roots are highly susceptible to clogging from oils and fine sediments. Oil spills will kill much of the invertebrate community within a few days and many of the mangroves will die in a few weeks. Mangroves may continue to die for a year after the spill. Fine particles from dredging, sugar and pulp mill wastes will also choke out the oxygen supply and kill mangroves.

Figure  12:  Louisiana  heron  or  commonly  named  tri-­‐colored  heron.  

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Diking that continually submerges prop roots and pneumatophores will drone and kill mangroves. Draining will allow other species to invade mangrove habitat. Blocking the flushing of tidal flows can result in stressful stagnant conditions. Reestablishing the proper hydrology is the single most important factor for successful restoration of mangroves. However, restoration of mangrove ecosystems can cost more than $50,000 per acre and take decades. Protection is the best policy.

Summary

Mangrove trees have special adaptations that allow them to grow in Florida’s subtropical tidelands, where no other trees can grow. Like many wetland plants, they have mechanisms for delivering oxygen to flooded roots. In addition, their roots may exclude some salt and their leaves may excrete it. The seeds of mangroves grow into floating plants before they are dropped.

The four mangrove species that grow in Florida are found in the community type and tidal zone that best fits their adaptations. Red mangroves with their tall prop roots are most frequently found in the fringe communities and the most seaward tidal zone. Black mangroves with their shorter pneumatophores and higher tolerance of salt and H2S are found further up the tidal zone in more stagnant basin communities. White mangroves usually don’t display either prop roots or pneumatophores (peg roots) and they grow even further up the tidal zone. Buttonwoods are the least salt tolerant and they grow at the interface of upland ecosystems like the tropical hardwood hammock.

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The mangrove forest provided habitat for animals both above and below the water. They are important habitat for seven endangered species and a multitude of more common invertebrates, fish, reptiles, birds and mammals. Leaves that drop into the water feed a food web starting with fungi, bacteria, and invertebrates that may end with shrimp, lobster and snapper on our dinner plates. Many people contribute to Florida’s tourist economy visiting mangroves just to observe the abundant wildlife.

Mangroves also help to protect and stabilize Florida’s shoreline. The benefits of the mangrove ecosystem and their susceptibility to human impacts are now better understood, appreciated, and protected.

Figure  13:  The  mangrove  ecosystem  

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Links to learn more:

Mangroves Fact Sheet from Electronic Data Information Source of UF/IFAS Extension—http//edis.ifas.ufl.edu

Blue Planet Biomes

http://www.blueplanetbiomes.org/mangrove_forests.htm

National Park Service—

http://www.nps.gov/ever/naturescience/mangroves.htm

Florida Department of Environmental Protection—

http://www.dep.state.fl.us/coastal/habitats/mangroves.htm