Mangroves

Montego
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The amazing trees that survive in salt water
Pneumatophores of Avicennia germinans (Black Mangrove)

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What are mangroves?

Mangroves are tropical, salt tolerant trees that are found throughout the equatorial seas. The Caribbean is home to three species: red, white and black.

Mangroves are important to a marine ecosystem for many reasons...

1. Water filtration of nutrients and sediments
2. Shoreline stabilization
3. Fish habitat (more then 75% of our commercial fish NEED mangrove wetlands as nursery habitat)
4. Bird habitat
5. Beastie habitat
6. Carbon Dioxide sequestration

Where are the mangroves?

Old Montego River & Howard Cooke Blvd. Park

The Montego Bay Marine Park has mangroves in many places throughout its bounds, but two particular areas are very dense. One of the areas surrounds the old Montego River and the Howard Cooke Blvd. Park, while the other is Bogue Lagoon. Both of these are productive habitats for a number of fish, birds and other "beasties".

About the Three Species

	Red Mangrove (Rhizophora mangle) So called for the colour inside its bark Red mangroves are recognizable for their arching prop roots. These roots extend from the main trunk and lateral branches, and grow towards the water until they reach the substrate. They are referred to as 'aerial roots' before they enter the water, and are referred to as 'prop roots' once they are in the substrate. The roots support the tree, take up nutrients and permit salt exclusion. Red mangrove leaves are elliptical and glossy, with a dark green topside and a paler dull green, sometimes with black spots, on the underside. Propagules are the pencil-like red mangrove seedlings that start growing within the wall of the fruit. They continue to grow and sprout after floating on water. As the seed tip becomes weighed down by taking in water, the seed falls to the substrate and sends out roots. Reds tend to grow the closest to the water. The prop roots help prevent coastal erosion, and smaller roots stabilize shifting substrate. The intertwined roots provide excellent habitat for juvenile and small fish, as well as other organisms such as oysters and crabs. Reds are the most susceptible to cutting. Since they only grow from the tips of branches and main stems (called 'apical meristems'), survival is doubtful when all the leaves and the apical meristem are removed.

Black Mangrove (Avicennia germinans)
So called for their dark-coloured bark

The leaves on this species are dull and dark green on the top and whitish green or gray below. They are also more elongated and pointy than the other species. Oftentimes there is a salty crust on the underside, since the leaves aid in salt exchange. Black mangrove is most notable for its snorkel like roots, called pneumatophores. These may be found sticking out of the sediment several meters from the base of the tree. They aid in air, nutrient and salt exchange, so they are in many ways functionally similar to the red mangrove's prop roots.

Black propagules are smaller than the red's, and are gray in colour. The seeds flow with the tide until the fruit wall falls, allowing the seedling to send roots into the substrate.

Blacks can develop a very stately and tall main trunk. Therefore, these mangroves are excellent windbreaks along the shoreline. Black mangrove is also more tolerant of salt, and basin environments than the other species.

	White Mangrove (Laguncularia racemosa) So called for their whitish bark The most noticeable feature of this tree are the leaves, which typically have uniform light green colour and small notches at their tips, as well as two small bumps on opposite sides of the leaf stem base. Some believe that these bumps secrete sugar and are called 'nectaries.' When these bumps attract ants, it is believed that the ants aide in control of harmful insects. Others think that they are used for salt exclusion. When the fruits drop to the substrate underwater, the seed walls become spongy and the seedlings emerge. White mangroves are less tolerant of flooding, and very rarely produce pneumatophore roots. Therefore, they are found more inland than the other species. They are typically a single trunk with very few distinguishing features. Whites are usually more tolerant of disturbance and cutting.

The Mangrove Food Web

A three dimensional system of interacting organisms based in these trees.

• On the roots
• Around the roots
• In the water
• In the mud
• In the branches

Mangrove roots...

• Slow water flow
• Hold soil
• Uptake and store nutrients
• Provide substrate habitat for other filtering organisms

Threats to the Mangrove Ecosystem

Mangroves trimmed improperly for landscaping

Trash & other pollution in the North Gully

• Landscaping and waterfront development, including creation of beaches
• Fodder cutting and Hoof Damage from livestock
• Use of mangrove for charcoal & lumber, as well as harvest for making of dye.
• Damage from waves (waves have increased as the coral reefs have eroded. These reefs used to break wave energy before reaching the shore.) Waves may also be produced by boat wakes.
• Pollution in its many shapes and forms

Case Example: Bogue Lagoon in 1964

Up until the 1960's, the Bogue Lagoon was a relatively wild and undisturbed ecosystem. Fourteen mangrove islands provided a porous water filtering environment for the nearby Montego River. The entire region was a well-developed ecosystem that was home to a variety of animals. This aerial image shows how the lagoon looked at this time. The most intrusive human activity was sugar cane cultivation, which appears in the bottom portion of the map. In 1969, ten of the fourteen islands were connected to build the Montego Bay Harbour and Freeport complex. This project greatly altered the flow of the Montego River and the surrounding sea. It eliminated or damaged all of the elements of the marine ecosystem: mangroves, sea grass, coral, and other the substrate. Furthermore, development of the lagoon area facilitated long-term human impact in the area. Homes and businesses now exist within this fragile environment. Circled in red on this map is the area that would one day become a housing development.

The Lagoon in the mid-1990's

Today, Bogue Lagoon is a heavily impacted, but still productive and ecologically valuable site. Due to land reclamation, its mangrove islands had been reduced to four in number. The Montego River no longer flows through the mangrove chain of islands. Today it flows with all its associated pollutants and sediments around Seawinds Peninsula and directly over the coral reef . Today, the Bogue Lagoon shows many signs of impact. The area in red shows an island of 1964 (same circle as above) which is now a housing development for wealthy Montegonians. The Park works with parish council, development, architects, engineers and planners to maintain a higher degree of environmental responsibility for the future than have been the norms of the past.

	The price to pay for a luxury home In a precedent-setting case in Puerto Rico, mangrove systems were valued at $300,000 USD per acre for their natural productive values

Looking to the future...

It's about revaluing a living thing or system. A mangrove wetland is more then a stinky mosquito factory to be immediately turned into a beach, and people need to know this to make good, responsible decisions. The Montego Bay Marine Park has a number of plans to help encourage sustainable practices and responsibility in the mangrove wetlands. Our key projects are the Howard Cooke Blvd. Mangrove Wetland Walking Trail and Interpretive Centre, as well as the Bogue Lagoon Kayaking Eco-Tour. Both of these plans are designed to have a minimal impact on the environment, while at the same time providing an educational outlet to Jamaicans and visitors from abroad. They will also provide an alternative income to fisherman. A fish, plant or "beastie" that is kept alive will continue to attract visitors, whereas a dead tree or fish is good for only one night's firewood or dinner. Hopefully we can encourage protection of the natural resources through these projects, and that the benefits will help all those who call Jamaica home.

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