Printable PDF Of This Image (~896k)
Chances are you’ve fished along the margins of the “mangrove swamps” that are so characteristic of the coastal wetlands of Citrus County. Or perhaps you have drifted in your canoe or kayak past the little mangrove-studded islands and outcrops of the St. Martins Marsh Aquatic Preserve that takes in the outflows of both the Crystal and Homosassa Rivers. Our visitors appreciate the natural beauty of mangrove clusters, more accurately known as mangals, but very few are aware of the vital importance of mangroves to the coastal environment throughout the tropical, subtropical and warm temperate zones of the world.
Rooting for Saltwater
Mangroves live with their roots planted in saltwater sand or mud. This salt-rich environment would kill most other plant species, but mangroves have developed ways of coping with their saline surroundings. Plants that thrive in salty waters are known, as a group, as halophytes. Their survival is based on a complex cellular chemistry that includes control of the water content and most remarkably, special glands in the base of their leaves, which actually excrete excessive salt.
Two mangrove species, the black mangrove and the white mangrove (Avicennia germinans and Laguncularia racemosa) handle their environment this way. A quite different coping mechanism is found in the red mangrove (Rizophora mangle) which has root cell membranes that impede the passage of salt while admitting the water that is vital to growth.
Red mangroves are found closest to the water and provide the familiar sight of numerous “prop roots.” These roots poke up above the surface of the water, presenting a tangled mass that makes walking through them almost impossible, but provides perfect shelter to the small fish and hatchlings that use mangrove thickets as nurseries and shelters from predators.
Black mangroves are found somewhat higher up the shoreline and are easily identified by numerous pencil-like roots called pneumatophores jutting out of the mud. These enable the mangrove to breath in the water-saturated soil. White mangroves, however, do not have a visible root system.
Over 50 mangrove species are found across the world, but these three are the only species found in Citrus County and Florida overall.
Expanding the Land
The three Florida species are often found together in dense mangrove forests. Mangroves will root just beyond the limits of established firm mud or sand, patiently blocking some of the tidal movement until they accumulate enough solid matter to extend the margin of the swampland or to establish a new island in the tidal marsh. These islands can become part of extensive mazes of narrow waterways and thickly overgrown patches of “land.” It is possible to lose your way in these areas, so a GPS unit—or better still, an experienced guide—is recommended for nature lovers, birders and other explorers.
Areas with high density of mangroves help form a valuable buffer against flooding, winds and waves. Their unique systems of roots also combat erosion by holding the soil together.
In Times Past, Food, Drink and Structure
Partly because of government protection for their habitat, and partly because there are so many more convenient options today, mangroves are no longer harvested. But there was a time when mangrove products were highly valued. The red mangrove, for example, has leaves that once were collected, dried and used to brew a kind of tea which was thought to have medicinal value. The red mangrove are also said to be edible.
Red mangrove wood is strong and water resistant. When found in growths mature enough, wood from this plant was used to build houses and boats, employed as fence posts and pilings and worked into home furnishings.
The nectar of black mangrove flowers attracts honeybees, making valued sites for establishing beehives. Tannin was also often extracted from black mangrove bark.
Many nature writers mention the small oysters that cling to the tidally-washed roots of mangroves. These oysters, when present, are much favored by raccoons, and are known locally as “coon oysters.” The oysters may be tender and tasty, but they are much too small for commercial harvesting.
A Well-Protected Natural Resource
The importance of mangroves in the overall health of wetlands, saltwater marshes and swamps—and their interrelationship with fish and waterfowl populations—has been recognized by numerous federal, state and county declarations. In Citrus County, perhaps the most important measure was the establishment, in October of 1969, of the St. Martins Marsh Aquatic Preserve, a 23,000 acre tract of sovereign submerged lands, including coastal salt marshes, mud flats, oyster bars, mangrove islands and seagrass beds. The preserve is the southern terminus for migratory waterfowl of the Atlantic and Mississippi flyways.
Additionally, the Citrus County Board of County Commissioners has further defined and provided for protection of many wildlife species, including the mangroves.
Educational Links