NATURE’S NOTEBOOK
Critical habitat for Southwest Florida ecology and economy
Mangroves
Mangrove habitats in Florida range from St. Johns County on the east coast and Levy County on the west southward into the Caribbean. There are four species of mangroves in south Florida: red mangrove, white mangrove, black mangrove and buttonwood.
The most dominant species is red mangrove, recognized by its arrangement of stilt- like prop roots and its habit of producing large, fleshy seeds that germinate while still on the parent plant. Red mangrove is dominant in low marsh areas along the oceanfront, tidal creeks, canals and low basins. Black mangrove is more dominant in high marsh areas. Associated with the black mangrove forest are the white mangrove and buttonwood species, which are restricted to areas of less significant tidal action.
Mangrove forests are tropical and subtropical and are killed back by freezing temperatures along the Central Florida coasts. However, black mangroves are more tolerant of freezing temperatures and thus are the species that pioneer coastal areas north of the subtropical zone. They can be distinguished by their emergent, pencil- like root extensions, known as pneumatophores. Mangrove islands expand during hurricane- free intervals. Mangrove species are mostly associated with saline water and soils, but they can also tolerate freshwater environments.
Mangrove forests, at no cost to man, provide protection from storms, shoreline stability, aesthetically pleasing experiences, and habitat for valuable birds, mammals, amphibians, reptiles, fishes and invertebrates. They are an important attractant for tourism on Sanibel Island, directly or indirectly drawing photographers, birders, fishermen, boaters, hikers and others who enjoy these unique tropical habitats and their associated wildlife. They also protect several endangered species of wildlife and partially support extensive coastal food webs.
The importance of mangrove habitats to fish and wildlife was well documented by William E. Odum et. al. in 1982 in The
Ecology of the Mangroves of South Florida: A Community Profile ( reprinted i n 1985). More than 217 species of saltwater and freshwater fish species spend part of their life cycle in mangrove habitats. This includes both commercial and sport fish such as redfish, snook, mullet, menhaden, spotted sea trout, gray and other snapper, sheepshead, jacks, ladyfish and jewfish. Many other fish species play significant roles in the food web for many species of birds, mammals and fish.
Important invertebrates that are dependent on mangroves i nclude pink shrimp, spiny l obster, oysters and blue crabs. Many other invertebrates are also important in the ecological food web associated with mangrove forests, particularly insects, which provide food for many species of birds. Over 200 species of insects have been identified in mangrove habitats.
Bird utilization of mangrove community types is significant, with several bird groups using mangroves for food, shelter and nesting. This includes wading birds, probing shorebirds, floating and diving water birds, aerially searching birds, birds of prey and arboreal birds.
In summary, mangrove habitats are very valuable to fish, wildlife and man. Mangrove forests help protect the shoreline from erosion caused by storms and heavy waves. They contribute to a healthy economy for Sanibel Island and south Florida by maintaining a diverse ecosystem for fish and wildlife that encourages many types of tourism. The best management for this ecosystem is preservation by improving water quality runoff and preventing destruction of mangrove habitats.