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Mangrove forests or mangals grow at tropical and subtropical latitudes near the equator where the sea surface temperatures never fall below 16°C. Mangals line about two-thirds of the coastlines in tropical areas of the world.
There are about 80 species of mangrove trees, all of which grow in hypoxic (oxygen poor) soils where slow-moving waters allow fine sediments to accumulate (Florida Department of Environmental Protection, 2000). Many mangrove forests can be recognized by their dense tangle of prop roots that make the trees appear to be standing on stilts above the water. This tangle of roots helps to slow the movement of tidal waters, causing even more sediments to settle out of the water and build up the muddy bottom. Mangrove forests stabilize the coastline, reducing erosion from storm surges, currents, waves and tides.
Just like the high and low areas of salt marshes where specific types of grasses are found, mangals have distinct zones characterized by the species of mangrove tree that grows there. Where a species of mangrove tree exists depends on its tolerance for tidal flooding, soil salinity, and the availability of nutrients. Three dominant species of mangrove tree are found Florida mangals. The red mangrove (Rhizophora mangle) colonizes the seaward side of the mangal, so it receives the greatest amount of tidal flooding. Further inland and at a slightly higher elevation, black mangroves (Avicennia germinanas) grow. The zone in which black mangrove trees are found is only shallowly flooded during high tides. White mangrove (Laguncularia racemosa) and buttonwood trees (Conocarpus erectus), a non-mangrove species (Florida Department of Environmental Protection, 2000), face inland and dominate the highest parts of the mangal. The zone where white mangrove and buttonwood trees grow is almost never flooded by tidal waters.
A unique mix of marine and terrestrial species lives in mangal ecosystems. The still, sheltered waters among the mangrove roots provide protective breeding, feeding, and nursery areas for snapper, tarpon, oysters, crabs, shrimp and other species important to commercial and recreational fisheries. Herons, brown pelicans, and spoonbills all make their nests in the upper branches of mangrove trees. (Florida Department of Environmental Protection, 2000). (Photo: Rookery Bay NERRS site)