The most common mangrove species in the tropical coastlines of North America are: the red 
mangrove ( Rhizophora mangle ); the black mangrove ( Avicennia germinans ); the white mangrove 
(Laguncularia racemosa)-, and the buttonwood ( Conocarpus erectus). The mangroves 
characterize and dominate a large portion of the world's tropical coastal margins. As early as 
330 BC, classical writers such as Theophrastus, Pliny the Elder, and Plutarch commented on 
these unusual trees that were nourished by salt water. The mangrove habitat is a unique blend 
of land and aquatic ecosystems. 
There is a natural succession of mangroves from seaward to landward. The red mangrove 
occurs at the seaward edge, the black mangrove occurs further landward, and the white 
mangrove occurs farthest from the shore. The red mangrove, with its thick mass of prop 
roots, is particularly well established in the substrate, and only the most violent of hurricanes 
can disturb it. It forms a protective barrier along the coast, behind which the other mangroves 
and associated flora take root. The accumulation of sand, leaves, and debris which is caught in 
this web of roots eventually decomposes and raises soil levels. At the same time, red 
mangrove seedlings take root farther seaward as the soil level increases. In time, the result is 
a gradual seaward extension of the coastline. The landbuilding quality of the red mangrove is 
important. It does well on nearly all types of soil or substrate provided they are wet. The black 
mangrove does well on all soils, including some dry and salty ones. The white mangrove does 
best in sandy and drier soil, thus explaining its general occurrence on higher ground. 
Until recently, mangrove forests in Florida were regarded as a wasteland suited only for 
development. It can be demonstrated, however, that these forests contribute in many ways to 
man's economic betterment. The contribution of the mangrove swamps to commercial and sport 
fisheries has been a subject of debate for some time. Only very recently have definitive studies 
of their contribution been undertaken. The role of the mangrove can be depicted in the following 
manner. The fallen leaves from the mangroves collect between the roots and begin to 
decompose. Ninety-five percent of the annual mangrove leaf production eventually enters the 
aquatic system. The decomposition is accomplished by the bacteria and fungi in the water, 
which turn the leaves into detritus. The detritus, or plant debris, of mangrove origin accounts 
for 35-60% of the suspended material in estuarine waters. Most of the other detrital material 
comes from the sea grasses. This detritus is the basis of the estuarine food chain, contrary to 
previous thought which maintained that estuarine food chains were based upon phytoplankton. 
A host of small invertebrate animals, ranging from nematode roundworms to small crabs and 
shrimp, feed on this detritus. They in turn are eaten by the larger predators, including 
commercial and game fish. It has been pointed out that the commercial shrimp of the Dry 
Tortugas are dependent upon the mangrove swamp as a nursery ground. Equally important is the 
fact that several other commercially valuable species, including mullet, gray snapper, red 
drum, blue crabs, tarpon, snook, and spotted sea trout, also rely on the mangrove swamp as a 
nursery and feeding ground. It is therefore evident that the destruction of mangroves would be 
tantamount to the removal of the primary food source upon which many animals of commercial 
and recreational importance depend. 
The role of the mangroves in landbuilding, shore protection and stabilization, and reforestation 
is of paramount importance. The tropical belts of the world are subjected annually to tropical 
depressions and hurricanes and mangrove forests are well suited to protect the coastline 
against the force of these storms. 
During the last few years, mangrove dieoffs have been observed. There is no evidence of 
seasonality. The dieoffs were first observed in black mangrove at higher elevations but are 
currently observed in red mangrove at lower elevations. There is a rough correlation with 
seagrass dieoffs suggesting possible correlation to high salinities (Brown and Ortner, 1994). 
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