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Florida's Mangroves: The Walking Trees


Mangroves serve very important functions in the ecology of South Florida. Mangroves have a high ecological role as nursery grounds and as a physical habitat for a wide variety of vertebrates and invertebrates. They recycle nutrients and the nutrient mass balance of estuarine ecosystems. Mangrove leaves, wood, roots, and detrital material provide essential food chain resources, and provide habitat for many wildlife including mammals, birds, reptiles, amphibians, and arthropods. Mangroves have a special ecological function for endangered species, threatened species, and species of special concern. They also serve as storm buffers; their roots stabilize shorelines and fine substrates, reducing potential turbidity and enhancing water clarity. One of the greatest values of mangroves swamps in Florida is their aesthetic appeal.

Four major factors limit the distribution of mangroves: climate, salt water, tidal fluctuation and soil type. Mangroves are found in tropical and subtropical estuarine habitats. They rarely tolerate temperatures below freezing; therefore occur in regions where the annual average temperature is above 19 C (66 F). Mangroves can live in salt water and are able to keep the salt content lower than the salt content in the soil. They accomplish this with several methods: secreting salt through salt glands; secreting salt through their roots; thick leaves with a waxy covering; facultative halophytes. Water fluctuations are important to mangrove forest development because the tidal action carries mangrove propagules into upper portion of the estuary.

Rhizophora mangle

Red Mangrove
The red mangrove is often found seaward of the other species and grows in frequently flooded areas. This species belongs to the family Rhizophoraceae and is very easy to identify. Red mangroves have characteristic aerial roots, which originate downward from the trunk and lower branches. These roots are an adaption to saltwater environment. The tree can take in oxygen directly from the surrounding air. The roots also provide the tree additional support to remain upright in the muddy substrate. The leaves are shiny, thick, leathery and dark green. Red mangrove fruits germinate on the parent tree to form long, pencil shaped propagules which act as seedlings. These seedlings are denominated viviparous. Flowering in spring and summer, although it can occur throughout the year. Although usually shorter than other types, the red mangrove tree may reach up to 50 feet in height.

Avicennia germinans
Black Mangrove
Black mangroves are often found in close association with red mangroves and seem to grow in the most salt-rich soils. The tree belongs to the family Avicenniaceae. On the ground around the black mangroves one can find numerous pneumatophores which extend upwards above the mud from the submerged root system. Pneumatophores are essentially the erect lateral branches of an otherwise horizontal root system. They serve the same aerating purpose as the prop roots of the red mangrove. The leaves of the black mangrove are narrow and oblong, dark green above and silver-green underneath. The black mangrove can grow as tall as 60 feet.

Laguncularia racemosa
White Mangrove
White mangroves usually grow on higher land, landward of red and black mangroves. They are often found in association with black mangroves. The white mangrove belongs to the family Combretaceae. Contrary to the other two species, the white mangrove does not develop prop roots or pneumatophores. The most identifyable characteristic of the white magrove are the leaves. The leaves are thicker and more oval than those of the red and black mangrove, and they are uniform pale green on both surfaces. On either side of the stem one can see two small glands on each leaf. The white mangrove grows as a tree or shrub and can reach a height of 50 meters or more.

For more information on mangroves, click here. [External Link]


Current Highlights

  • Read the latest edition of the Lake Worth Lagoon E-News [LINK]
  • Read the Fall 2015 edition of Environmental Times [PDF]
  • Become a Natural Area Youth Explorer by completing a Scavenger Hunt at a local natural area! [PDF]
  • Watch this touching footage on the Andrew "Red" Harris Artificial Reef deployed last week 1 mile offshore from the Jupiter Inlet [VIDEO]
  • Operation Clean Sweep is a mobile pesticide collection program offering free pick up of the first 500 lbs for farms, nurseries, pest control companies, and golf courses. Visit the Florida Department of Environmental Protection's website for more information. [LINK]
  • Stay up to date on our projects with the Department's Monthly Status Reports. [LINK]