Mangrove

Three species of mangroves are found in Florida, red mangrove, black mangrove, and white mangrove.

Florida Mangroves

Black Mangrove on left and Red Mangrove on right.

Mangroves are a keystone species that play an important ecological role as habitat for many species of marine and estuarine plants and animals; as shoreline stabilization and storm protection; for water quality protection and maintenance; and as food-web support.

The mangrove forest is a tropical ecosystem that provides protected nursery areas for small fry, crustaceans and shellfish, which in turn, provides food for snook, snapper, tarpon, jack crevalle, sheepshead and red drum. Mangrove branches are rookeries, or nesting areas, for coastal birds such as brown pelicans and roseate spoonbills.

Red mangrove trees at water edge.

Florida's estimated 469,000 acres of mangrove forests contribute to the overall health of the state's southern coastal zone. Mangroves thrive in salty environments because they can obtain freshwater from saltwater. Some secrete excess salt through their leaves, while others block absorption of salt at their roots. Mangroves are a critical species in the because they trap and cycle various organic materials, chemical elements and nutrients from the saltwater. Mangrove roots act not only as physical traps but also provide attachment surfaces for marine organisms that filter water through their bodies and, in turn, trap and cycle nutrients in the water.

Florida Mangrove Species

Red mangrove roots.

Of the three Mangrove species found in Florida, the red mangrove (Rhizophora mangle) is probably the most well-known. It typically grows along the water's edge. It is easily identified by its tangled, reddish roots called "prop-roots." These roots have earned Red Mangroves the title of "walking trees", because they appear to be standing or walking on the surface of the water.

The black mangrove (Avicennia germinans) usually occupies slightly higher elevations upland from the red mangrove. The black mangrove can be identified by numerous finger-like projections, called pneumatophores, that protrude from the soil around the tree's trunk.

The white mangrove (Laguncularia racemosa) usually occupies the highest elevations farther upland than either the red or black mangroves. Unlike its red or black counterparts, the white mangrove has no visible aerial root systems. The easiest way to identify the white mangrove is by the leaves. They are elliptical, light yellow green and have two distinguishing glands at the base of the leaf blade where the stem starts.

Red Mangrove Seed

All three mangrove species found in Florida utilize a remarkable method of propagation. Seeds sprout while still on the trees and drop into the soft bottom around the base of the trees or are transported by currents and tides to other suitable locations.

Florida's mangroves are a tropical species; therefore, they are sensitive to extreme temperature fluctuations as well as subfreezing temperatures. Research indicates that salinity, water temperature, tidal fluctuations and soil also affect the growth and distribution of mangroves. They are common as far north as Cedar Key on the Gulf Coast and Cape Canaveral on the Atlantic Coast. Black mangroves can occur farther north in Florida than the other two species. Frequently, all three species grow intermixed.

Mangrove Losses In Florida

It is true that mangroves can be naturally damaged and destroyed, but there is no doubt that human impact has been most severe. Florida Marine Research Institute scientists are studying changes in Florida's coastal habitats. The scientists are able to evaluate habitat changes by analyzing aerial photographs from the 1940s and 1950s and satellite imagery and aerial photography from the 1980s. Frequently the changes illustrate loss of mangrove acreage. Through researching the history of study sites, these losses are often attributed to human activities.

Tampa Bay, located on the southwest Florida coast, has experienced considerable change. It is one of the 10 largest ports in the nation. Over the past 100 years, Tampa Bay has lost over 44 percent of its coastal wetlands acreage; this includes both mangroves and salt marshes.

The next major bay system south of Tampa Bay is Charlotte Harbor. Unlike Tampa Bay, Charlotte Harbor is one of the least urbanized estuarine areas in Florida. However, there has been some mangrove destruction here also. Punta Gorda waterfront development accounts for 59 percent of the total loss. An increase in mangrove acreage was noted in parts of the harbor. This is due to changes in the system. As tidal flats were colonized by mangroves, tidal flat acreage decreased and mangrove acreage increased. Spoil islands, created as byproducts of dredging, also provide suitable habitat for mangroves.

A changing system was also observed on the Southeast Florida coast in Lake Worth, near West Palm Beach. Lake Worth naturally evolved from a saltwater lagoon to a freshwater lake. Human changes modified the lake back to an estuarine lagoon. Lake Worth has experienced an 87 percent decrease of its mangrove acreage over the past 40 years. Mangroves appear to be replaced by Australian pines and urbanization. The remaining 276 acres of mangroves occur in very small scattered areas and are now protected by strict regulations.

Another study site included the Indian River from St. Lucie Inlet north to Satellite Beach. Indian River is the longest saltwater lagoon in Florida. There are just less than 8,000 acres of mangroves within the study site, but only 1,900 acres are available as fisheries habitat because of mosquito impoundments. Consequently, 76 percent of the existing mangrove areas are not productive to fisheries. A total of 86 percent of the mangrove areas have been lost to fisheries since the 1940s.

Mangrove Protection

In 1996, the Florida Legislature enacted the Mangrove Trimming and Preservation Act (FL Statute 403.9321) to limit mangrove removal by landowners in order to protect Florida's remaining mangrove forests.

(1) It is the intent of the Legislature to protect and preserve mangrove resources valuable to our environment and economy from unregulated removal, defoliation, and destruction.

(2) It is the intent of the Legislature that no trimming or alteration of mangroves may be permitted on uninhabited islands which are publicly owned or on lands set aside for conservation and preservation, or mitigation, except where necessary to protect the public health, safety, and welfare, or to enhance public use of, or access to, conservation areas in accordance with approved management plans.

(3) It is the intent of the Legislature to provide waterfront property owners their riparian right of view, and other rights of riparian property ownership as recognized by s. 253.141 and any other provision of law, by allowing mangrove trimming in riparian mangrove fringes without prior government approval when the trimming activities will not result in the removal, defoliation, or destruction of the mangroves.

(4) It is the intent of the Legislature that ss. 403.9321-403.9333 shall be administered so as to encourage waterfront property owners to voluntarily maintain mangroves, encourage mangrove growth, and plant mangroves along their shorelines.

(5) It is the intent of the Legislature that all trimming of mangroves pursuant to this act conducted on parcels having multifamily residential units result in an equitable distribution of the riparian rights provided herein.

Web Links

• Florida's Mangroves
• SOUTH FLORIDA AQUATIC ENVIRONMENTS-Mangrove

References