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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



shoals or may occur as scattered plants in brackish 

 or even fresh water well inland from the coast. 

 Generally, it grows on shores or low islands where 

 the substrate is covered by tidal water even at 

 low tide. The Avicennia zone which commonly 

 includes Laguncularia and various salt-marsh 

 plants is flooded, at least in its outer part, by salt 

 or brackish water at high tide. When Lagun- 

 cularia forms a distinct community, it is usually 

 inland from Avicennia. Conocarpus and its asso- 

 ciates of the transition zone are seldom flooded. 

 The mangroves grow on peat, muck, marl, sand, 

 and rock. They are killed by severe frosts. 

 Economically they have been of little importance 

 except in certain areas where they have been 

 used for fuel, pilings, and a source of tannin. It 

 is contended by some that mangrove swamps 

 protect shorelines, build up soil levels along the 

 coast, extend shorelines, and form new islands, 

 but it is doubtful that the mangroves play a very 

 large part in land building. 



Mangrove swamp in the Gulf region reaches its 

 greatest development along the southwestern 

 coast of Florida in the Ten Thousand Islands area. 

 There mangroves of all three species, some more 

 than 25 meters tall and 2 meters m circumference 

 (Davis 1940), grow in the extensive strand and 

 estuary swamps. Mangrove swamp to a depth 

 of several miles covers the western and southern 

 tip of peninsular Florida from Cape Romano to 

 Cape Sable and thence eastward to Biscayne 

 Bay. Mangroves also cover the numerous small 

 keys in Florida Bay and fringe the larger Florida 

 Keys south and west to the Marquesas. North- 

 ward along both sides of Florida less well developed 

 mangrove swamp, perhaps better described as 

 mangrove thicket, extends to the Cedar Keys area 

 on the Gulf coast and Cape Canaveral or farther 

 north on the' Atlantic coast, mostly in lagoons, 

 bays, and estuaries. As the mangroves become 

 smaller and more scattered on the northern Gulf 

 coast, salt marshes become more extensive. 

 Killing frosts apparently are the deciding factor 

 in the competition between the species comprising 

 the two vegetation types. In Florida mangrove 

 areas are estimated to total more than a thousand 

 square miles (Davis 1940). 



The botanically less known Gulf coasts of Cuba 

 and Mexico are fringed in the appropriate habitats 

 with mangrove swamp. According to Leopold 

 (1950), mangroves extend northward along the 



Mexican Gulf coast to southern Tamaulipas. 

 Along the northern shores of the Gulf from Cedar 

 Keys in Florida to southern Tamaulipas typical 

 mangrove swamp is absent, and mangrove species 

 are represented only by the more hardy Avicennia 

 which gi'ows, where present, mostly as scattered 

 shrubs with Batis and other salt-marsh associates. 

 Mangrove swamp is found throughout the 

 tropics along low-lying shores and estuaries that 

 are protected from direct wave action. Although 

 it is best developed on mud and marl, it is present 

 also on sand and even rock wherever crevices 

 permit the seedling mangroves to gain a foothold 

 (Crossland 1903). Oriental mangrove swamps 

 are similar to those of the American and West 

 African shores except that there are many more 

 species of Oriental mangroves. Although few 

 in number the American mangroves are widely 

 distributed. Rhizophora mangle, Avicennia nitida, 

 and Laguncularia racemosa are all found on the 

 tropical coasts of West Africa as well as on botl- 

 Pacific and Atlantic shores of tropical America. 

 The floating seedlings or fruits of all three remaui 

 buoyant and alive in salt water for several months 

 (Guppy 1917) and are thus well-adapted to long 

 distance dispersal by ocean currents. Several of 

 the plants associated with them on the Gulf 

 coasts, such as Caesalpinia crista, Sophora tomen- 

 tosa, and Acrostichum aureum, range even more 

 widely in the tropics. 



SALT MARSH 



Salt marshes of temperate shores have received 

 perhaps even more attention from botanists than 

 mangrove swamps of tropical shores. Thos 

 along the Gulf coast have not been neglected 

 Penfound and Hathaway (1938) have made ? 

 very thorough study of marshes in southern 

 Louisiana. Other botanists who have publishe 

 on salt marshes of the northern Gulf shores a)- 

 Mohr (1901), Lloyd and Tracy (1901), Cock 

 (1907), and Penfound and O'Neill (1934). Harsh- 

 berger (1914), Harper (1927), and Davis (1940, 

 1943) have described salt marshes and salt flat;- 

 along the Florida Gulf coast. The salt marshes 

 along the Atlantic coast of North America arc 

 similar in many respects, and have been weL 

 described by Kearney (1900, 1901), Harshberger 

 (1909), Johnson and York (1915), Conard (1935), 

 and Chapman (1940a, 1940b). 



