Mangroves
Habitat and Adaptations
The oceanic habitats support a great diversity of life and ecosystems (Ocean Literacy Principle #5)
Mangrove refers to the species of tree that make up a Mangrove Forest. Mangroves are trees or shrubs that grow in coastal “swamps” that generally have bidaily flooding with high tide. These trees live in some of the harshest environments on earth. Dealing with salt, intense sun exposure and roots inundated with saltwater, Mangrove trees (and shrubs) have some of the most unique adaptations to their roots and shoots.
Mangrove forests are the swamps of the tropics, found along the coast of tropical and subtropical countries they are a coastal habitat that exist in tidal zones of saltwater that receive little if any fresh water contributions. Nearly 75 percent of tropical coastlines, defined as 25 degrees north and 25 degrees south of the equator, have some kind of mangrove tree or shrub. With very little freshwater influence via rivers or streams to water the elaborate root systems, they have leaf and root adaptations to accommodate and rid the plant of excess salt while holding on to the freshwater necessary for survival.
The roots of mangroves are uniquely shaped to continually give a supply of oxygen to the plant outside of the water, even during high tide. This above and below water root system provides a great place for fish species, acting as a nursery ground for thousands of fish species. While providing a home for juveniles of larger fish and a permanent home for some smaller fish, these roots also provide an incredible amount of protection from erosion for the substrate during tropical storms.
We do have a subtropic region in North America that contains mangroves. The mangrove species that are found in North America are found along the Gulf Coast (Gulf of Mexico) in Florida, Alabama, Louisiana, Texas, Cuba and Puerto Rico. There are four species that vary in appearance and adaptations. The White, Black, Red and Buttonwood mangroves are all found in and around the gulf and all four can be found in Florida.
Learning Objectives:
- Demonstrate a general understanding of the mangrove ecosystem components (aquatic, terrestrial, avian & physical)
- Evaluate and explain flora and fauna adaptations that lead to the success of species
Analyzing Adaptations Flora and Fauna in Mangrove Habitats: Species Found in Mangroves
Mangroves are critical habitat for year-round resident species, migratory species as well as provide nursery grounds to various species. All three add to the biodiversity of mangroves. When mangroves are destroyed so is the habitat necessary for the year round and migratory species as well as those species that need this habitat for security during the juvenile phase.
Year-round Residents
The Red Mangrove Sea Crab lives in the canopy of the mangrove tree. The color ranges from red to orange and it feeds mainly on the flowers and fruits of plants in the mangrove forest. Mangrove crabs add to the biodiversity but may actually be one of the most significant players in trapping the energy in the forest. They consume and bury leaf litter, burrow into the ground at high tide, climb trees to escape predators while their feces and larvae provide a food source for juvenile fish.
Migratory Species
Species that use mangroves for a stopping place on a longer journey or a resting place for the winter months rely on the mud flats, the roots and the canopy for feeding and breeding. The warbler depends on mature mangrove forests for overwintering. The warmer climate, higher prey abundance and thick canopy provides the perfect place for many species as they leave the snowy cold north for the winter.
Nursery Grounds
Mangroves play an important role in the reproductive process of many sport and commercially fished species. Gray Snapper and Red Drum are among the species found in the mangrove forests in south Florida. The shallow water and intertwined root system provide protection from above avian predators and within the water from larger fish predators. The juveniles seek shelter here until they are large enough to avoid predators in the open ocean. As mangroves decrease and disappear, so does the population size of the highly prized fish.
Flora Adaptations: Root Structures
Root systems in plants are some of the most important features and are not always as simple as they may seem. Roots can be solely responsible for the uptake and supply of nutrients, fresh water, oxygen and provide support and structure for the plant. Here we will take a look at some of the root adaptations of Mangroves, understand why they have this adaptation and provide information on just how complex these adaptations can be and how they overcome the harsh environment in which they live.
Snorkel Roots
Peg like single roots that extend from the underwater root to above the water level, sometimes called pneumatophores provide a way for the mangrove to breathe. Also referred to as breathing roots, the pneumatophore would be similar to a snorkel that a human would use, providing oxygen to an oxygen breathing species when underwater. Usually seen in the White Mangrove, these really neat adaptations can range in numbers from just a few to a few hundred! They extend up to the surface from the underground horizontal root that extends out from the tree. These snorkel roots are generally seen in the shorter trees or shrubs that would not need as much support as the taller trees
Buttressing Trunks
Buttressed trunks are large wide trunks that extend out on all sides of the tree trunk, almost like a pedestal. These wide thick trunks provide stability in the otherwise shallowly rooted tree. Mangroves live in an area of sandy or mud bottom, this bottom or substrate is not deep (thick) so there is very little for the tree to use as a holdfast. The buttressed or fat bottom tree provides a more substantial area for stability. This wide thick part of the trunk also serves as a long-distance conduit for water and nutrients. Buttressing is generally seen in the taller mangrove trees, not shrubs, it is one level of defense from the strong summer storms seen in the region. Buttressing in mangrove trees has been used architecturally to stabilize buildings and structures for hundreds of years.
Prop Roots
Growing from the branches of the tree and extending down to the water and sand/mud, these prop roots are instrumental in providing structure to the tree. Just as you would use your arm to prop yourself up while sitting or leaning, these roots prop the tree up and provide support higher on the center of gravity of the tree which is especially necessary during tropical storms and hurricane. The Red Mangrove, native to Florida, typically has many prop roots that tangle together and make it difficult to distinguish one tree from another. These roots mostly provide support but do also absorb water and nutrients when necessary. Banyon trees are also very popular for their prop roots.
Key Vocabulary
Adaptations
Anoxic
Black mangrove
Buttressing
Concentration
Evaporation
Holdfast
Hydrophyte Inundate
Juvenile
Lenticels
Migratory
Nursery grounds
Organic Material Pneumatophores
Red mangrove
Sediment
Subtropic
Tropic
White Mangrove
Environmental Importance
The ocean ecosystems made the Earth inhabitable (Ocean Literacy Principle #4)
Mangrove forests play a vital role in the protection and economy of coastal communities. The unique properties and structure of the root systems provide support for the soil and sand of the coastal communities lending a hand in protection from erosion, storms and waves while at the same time providing homes and refuge for many species of fish and crustaceans. The richness and biodiversity of these ecosystems is an excellent source of food and income, making life sustainable for these (sometimes) remote islands. The interconnectedness of the root systems is excellent in their ability to sequester and remove carbon from the immediate environment (water, soil and plants) while contributing to the detrital food cycle-yes, decomposed organic matter is food for someone!
The amount of cover provided by the roots and leaves of the mangrove plant is estimated to protect 75% of game fish and 90% of commercial species of fish at some point in their life. Many of the species that rely on the mangrove cover are either endangered or threatened. The Red Mangrove prop root has been quantitatively documented and is said to be more important environmentally to some juvenile fish species than seagrass beds. Knowing the role of that mangroves play in the food cycle and food chain of so many species has led to more pointed governmental regulation of these coastal communities. Coastal land use and development laws must now take into consideration the mangrove itself, along with the species known in the area and their International Union for Conservation of Nature (IUCN) status.
Learning Objectives:
- Identify 3 ways that mangroves are environmentally important
- Discuss mangrove plant species, the chemicals they reduce and their adaptations
- Explain the significance of reducing storm surge
- Comprehend the significance of the mangrove forest as a nursery
Analyzing the significance of mangrove forest functions in the global environment
The role of a mangrove extends beyond that of coastal buffering and nursery grounds. These nutrient loving plants have the capacity to use or store a variety of nutrients throughout their lives. One of the most notable being the uptake of carbon dioxide gas and storing it as carbon in the wood and soils. Because of their location, transition zone from inland to marine waters, they also play a role in the nitrogen and phosphorus cycles as they take up nitrates, ammonium and phosphates that was downstream from fertilizers.
Vital role in detrital food cycle
Mangroves are a vital part of both the complex terrestrial and aquatic food cycles, especially the detrital food cycle. Detritus, organic matter produced by the decomposition of organisms, plays an integral role in the soil of the ecosystem by breaking down matter, storing chemicals and organics or converting carbon, nitrogen and other nutrients to usable forms. Since mangrove trees exist over an aquatic environment, the leaves that drop can be colonized with marine fungi and bacteria within a few hours. The colonization on the leaves leads to continual breakdown of the organic material (the carbon structure in the leaf) that is difficult to digest. The fungi and bacteria convert the carbon compounds along with nitrogen to create a rich material called detritus, which is food for small worms, shrimp and snails that live in the sand of the intertidal zone. These are not the only species that feed on this nitrogen rich material, mollusks, barnacles, clams and oysters have been observed feeding on the material. The food cycle continues as the mussels, clams and other bivalves are eaten by larger fish and crabs and which are then subsequently preyed upon by birds and larger, game fish that ultimately are consumed by humans.
Carbon Sink
Mangrove forests cover 75% of tropical coastlines yet only make up 1% of the earth surface. These forests contribute to the reduction of atmospheric carbon dioxide (CO2) by collecting and transferring it to the roots. Once there, CO2 and other nutrients are transformed into organic matter and stored in the water-logged soil. CO2 is an important greenhouse gas that helps trap heat within the earth's atmosphere. All species depend on levels of accessible CO2 for normal biological functions to be within a small range. The rising amount of CO2 in the atmosphere has become a problem for some ecosystems and species. Mangroves and their associated soils could be responsible for sequestering as much as 22.8 million metric tons of carbon each year and converting 10% of the terrestrial dissolved organic carbon (DOC) that is exported to the ocean each year! Recent research has suggested that mangroves sequester and store more than once thought. Many Scientist believe that mangroves collectively are the answer to removing the highest amount of atmospheric CO2 in the shortest amount of time.
Water Purification
Left alone to do their job, mangroves can be excellent water purifiers! Many nutrients enter our coastal buffer zones through runoff from the local area, but also from hundreds of miles away especially after large rain events. This runoff can bring in an excess of nitrates and phosphates, mostly found in fertilizers and lawn care/maintenance chemicals used residentially and commercially. Nitrogen and Phosphorus are the primary growth elements of mangroves (nitrogen is obtained from the uptake of ammonium). Mangroves are some of the highest nutrient absorbing angiosperms and are one of the only trees that are known to opportunistically use elements and nutrients when they become available. A healthy thriving mangrove forest can taking up much of the excessive nutrients converting and using or storing the newly found nutrients ultimately preventing excesive nutrients from entering the ocean.
Coastal Communities
Reducing storm surge in vulnerable communities has become one of the most important of the ecosystem services that mangroves provide. With an increasing number of high intensity tropical storms and with many more people moving to and building on previously undeveloped coastal land, a considerable amount of attention has been given to climate change and protecting the coast. The intricate root systems and multiple branches aid in attenuating waves from storms. With almost 2 million people living in coastal areas, mangrove mitigation is necessary to safeguard shorelines and continue to provide the nursery and feeding zones for many fish and crustacean species that rely on mangroves. Mangroves are abundant with life and are an essential food source for the 2 million people living in these areas. Local communities rely on the many fish that inhabit the ecosystem for food and as well as economic income from the many crustaceans and bivalves harvested through aquaculture. A highly productive and biodiverse ecosystem, mangroves provide seafood to feed millions of people. The destruction of mangroves and disruptive effects of climate change could lead to a decline in aquaculture, economic loss from tourism and decrease in additional ecosystem services. Efforts to restore and protect mangrove forests is vital in the sustainability of fisheries, coastal economies and communities around the world.
Key Vocabulary
Aquaculture
Atmospheric Carbon Dioxide
Attenuate
Bacteria
Bivalve
Colonized
Crustaceans
Detritus
Dissolved Organic Carbon
Ecosystem Services
Endangered
Food Cycle
Fungi
Greenhouse Gas
International Union for the Conservation of
Nature (IUCN)
Intertidal Zone
Mitigation
Organic Material
Sequestering
Storm Surge
Threatened
The Changing Climate
The ocean is a major influence on climate (Ocean Literacy Principle #3)
Scientist have known for many years that mangrove forests have played and continue to play a vital role in carbon sequestration, removal, storage or transportation of carbon dioxide. Most of the carbon taken up by mangroves during growth is converted to biomass and stored in the wood and soils where it can remain indefinitely until disturbed. After studying the inputs and outputs of mangroves, scientist now know that the carbon-rich mangrove forest can store twice as much carbon as a salt marsh of the same acreage. They have also learned that the most uptake and storage carbon occurs in young mangroves during their rapid growth period. The older, more established mangroves continue to store the carbon that was originally taken up during their younger growing phase but they play a more pivotal role in protecting coastlines from destructive storms and sea level rise. Jin Eong On, a leading mangrove scientist believes that mangroves have the highest net productivity of any natural ecosystem. Mangroves can store as much as 24 million metric tons of carbon in the soil annually, drastically changing the soil and water chemistry in the area surrounding the forest. The effects of the changing climate and impact of human activities on mangrove forests has led to a loss of over 450,000 acres of mangroves worldwide. The carbon that was once locked away has been released, many species that rely upon the mangroves for habitat are in danger and the increase in powerful storms continues to threaten the survival of mangroves. Conservation efforts, planting of mangrove trees and reducing our carbon footprint can and will help preserve these vital ecosystems.
Learning Objectives:
- Develop an understanding of the interdependence humans have with mangrove including how our actions directly or indirectly change mangrove forests
- Identify and understand sources of climate change, describing and explaining the causes and discuss the adverse effects as well as long-term solutions
Anthropogenic Actions and Climate Change
Mangrove forests are the wetlands of the tropics. Many tropical and coastal communities depend on these areas for food, wood, and clean water. Achin Steiner, United Nations Under-Secretary General told the Times of London, “We already know that marine ecosystems are multitrillion-dollar assets linked to sectors such as tourism, coastal defense, fisheries and water purification services. Now they are emerging as natural allies against climate change."
Carbon dioxide in our atmosphere acts like a blanket for earth, trapping just enough heat within the atmosphere to keep us warm. As carbon dioxide is released in abundance in the atmosphere, it traps and holds more and more heat, increasing the temperature of the atmosphere and the ocean. The exchange of carbon dioxide between the ocean surface waters and the atmosphere historically has been an equal exchange. With increasing surface water temperatures, there is a decrease in the rate of carbon dioxide uptake of (warmer water releases CO2). At the poles where the water is cold, the ocean can absorb more carbon dioxide which in turn upsets the balance of the atmospheric versus ocean surface carbon dioxide. The rise in atmospheric and oceanic temperatures has led to a decrease in the polar ice, ice caps and glaciers all which contribute to sea level rise. Over the past century, sea levels have been rising at an average rate of about one eighth of an inch per year. Although this does not seem like a large increase, in a coastal mangrove area that is delineated by the daily tides, this can force big changes in the flora found in the area.
Sea Level Rise
Sea level rise is changing coastlines all over the world. Coastal habitats are unique in that they face changing water levels daily and throughout the month and year. The plants and animals that live in the coastal ecosystems have special adaptations to allow for the daily inundation of saltwater. The zonation (arrangement) of the plants starting at the oceans edge and moving inland varies with the plants ability to handle excess amounts of salt. With the changing climate, we have seen a shift inland of many mangroves, disrupting inland plant and animal species. In some areas human development blocks the migration of mangrove forests inland. As sea levels continue to rise, some mangroves may experience higher high tides and erosion of the mud surrounding their roots that could result in the inundation and loss of the mangroves.
Decrease in Biodiveristy
The biodiversity of the mangrove forests reaches far beyond what can be seen in the immediate area. These areas of high biodiversity contain many trophic levels that include numerous fish, crustaceans, birds, worms, snails, sharks, marine mammals and humans all which depend on the mangrove ecosystems for life. When humans disrupt one area of the food web it has a cascading effect and bringing it back into balance can take many years. In the past few decades, we have seen many species disappear from some of the most productive mangrove forests. When mangroves are removed, the calm water nurseries used as protection for smaller juvenile fish diminish or disappear. As these fish nurseries disappear, there is a drastic decline in subsequent years in the number of large fish and avian species that depend on the small fish for substance. The destruction of mangrove forests is also associated with an increase in wave action. The upsurge in wave energy results in an inland movement of small crustaceans and bivalve species, or an exit all together, which adds to the decline in species biodiversity in the area. Restoring the biodiversity and food web that took hundreds or thousands of years to achieve is not something that can be easily or quickly achieved.
Water and Soil Chemistry
Left alone to do their job, mangroves can be excellent water purifiers! Many nutrients enter our coastal buffer zones through runoff from the local area, but also from hundreds of miles away especially after large rain events. This runoff can bring in an excess of nitrates and phosphates, mostly found in fertilizers and lawn care/maintenance chemicals used residentially and commercially. Nitrogen and Phosphorus are the primary growth elements of mangroves (nitrogen is obtained from the uptake of ammonium). Mangroves are some of the highest nutrient absorbing angiosperms and are one of the only trees that are known to opportunistically use elements and nutrients when they become available. A healthy thriving mangrove forest can benefit from such runoff, absorbing, converting and using or storing much of the nitrates and phosphates ultimately preventing the excess nutreints from entering the ocean waters.
Carbon Sequestration
Similar to the effect of changes in air quality that may impede our ability to breathe or make us sick, changes in the air or “gas” that exist in the soil and water of mangrove forest may also inhibit their ability to function. Mangroves take up carbon dioxide gas just as any plant does, but they do it more efficiently and at a much faster pace. After mangroves remove CO2, it is stored in the wood and soil where it can stay for hundreds of years. Between 2000 and 2015 roughly 122 million tons of carbon was released to the atmosphere due to the loss of mangrove forests. In the past 40 years, as much as 40% of the world's mangroves have been deforested. When we cut and remove mangrove, we not only take away a valuable source of carbon sequestration but also release the stored carbon back into the atmosphere and the ocean.
Want to learn more about Biodiversity? Watch our short video lesson on the impact of human activity on Biodiversity!
Key Vocabulary
Ammonium
Angiosperm
Biodiversity
Carbon Dioxide
Delineated
Food Web
Inundation
Migration
Nitrate
Nutrient
Phosphate
Run off
Sea Level Rise
Sequestration
Trophic level
Wave Action
Zonation
Activities
Click on the image below to open and download Fact Sheets, Crossword Puzzles and Coloring Sheets!
Multimedia
Click on the image below to open and download Videos and Webinars!
Next Generation Science Standards
MS-ESS-3 Earth and Human Activity. Application of scientific principles for monitoring and minimizing human activity on the environment
LS1A-Structure and function of animals as it applies to their habitat
LS1B- Growth and development of organisms
LS2A- Interdependent relationships in organisms
LS2C- Ecosystem Dynamics, Functioning and Resilience
LS4A- Evidence of common ancestry and diversity
LS4C- Adaptation
HS-LS2-2 Ecosystems: Interactions and Dynamics
HS-LS4-6 Biological Evolution: Unity and Diversity