GULF OF MEXICO 



197 



Salt marshes are best dovoloped along the more 

 protected, temperate shores of the northern part 

 of the Gulf of Mexico. There extensive marshes 

 of salt-tolei-atiiifr species of tlowerinj; plants cover 

 the tidal shores of the estuaries, bays, and lagoons. 

 According to Griffitts (1928) there are 5,600,000 

 acres of salt marshes in the South Atlantic and 

 Gulf States, of which 3,381,500 are in Louisiana, 

 680,000 in Florida, 315,000 in Texas, 34,000 in 

 Alabama, and 26.500 in Mississippi. Louisiana 

 possesses almost one-half of the total salt-marsh 

 acreage in the LInited States. 



The dominant species in these marshes are 

 Spartina alterniflora Loisel., smooth cordgrass, and 

 Juncus roemerianus Sclieele, black rush, each 

 commonly forming extensive and exclusive col- 

 onies. Several other grasses or grasslike plants, 

 however, are often found in association with them. 

 These are Distichlis spicata (L.) Greene, saltgrass, 

 Spartina patens (Ait.) Muhl., salt-meadow cord- 

 grass, Spartina spartinae (Trin.) Merr., Scirpus 

 robusfu.s Pursh, salt-marsh bulrush, and Fim- 

 bristylis castanea (Michx.j Vahl, a sedge. Showy- 

 flowered plants like Limonium carolinianum. 

 (Walt.) Britt., sea-rosemary, Solixiago semper- 

 I'irens L. var. meiicana (L.) Fern., seaside golden- 

 rod, Pluchea purpurascens (Sw.) DC, salt-marsh 

 fleabane. Aster exilis EU., A. suhulatus Michx., 

 and ^4. tenuijolius L., the salt-marsh asters, and 

 Borrichia frutescens (L.) DC, sea-oxeye, give some 

 color to the marshes though they are seldom 

 abundant. 



On wet, saline flat areas which are near high 

 tide-mark the vegetation is more open. There, 

 sometimes with scattered and dwarfed specimens 

 of Avicennia nitida L., black mangrove, and 

 several plants, such as Distichlis, Borrichia, 

 and Limonium, are found the peculiar halophytes 

 with succulent stems or leaves, Batis marilima L., 

 saltwort, Salicornia inrginica L. and S. bigelovii 

 Torr., glassworts, Suaeda linearis (Ell.) Moq., 

 sea-blite, Sesuvium portulacastrum L., sea-purslane 

 Philoierus vermicularis (L.) R. Br., beach-carpet, 

 and Bacopa monnieri (L.) Pennell, marsh-hyssop. 

 With these grow a few species with showier 

 flowers: Sabatia stellaris Pursh, sea-pink, Gerardia 

 maritima Raf., false-foxglove, and two vines, 

 Ipomoea sagittata Cav. and Cynanchum palustre 

 (Pursh) Heller. On slightly higher ground these 

 herbs or small shrubs give w&y to a thicket of 

 taller shrubs consisting mostly of Iva frutescens 



L., marsh-elder, Baccharis halimifolia L. and 

 B. anyustijoiia Michx., groundselbushes. 



Farther south along the Florida Gulf coast 

 from Tampa Bay to Key West the salt maishes 

 become much less extensive due to competition 

 from the mangroves. Salt-marsh plants there 

 generally form an understory in the Avicennia 

 zone of the mangrove swamps or predominate in 

 the transition zone between the mangroves and 

 non-halophytic vegetation. Characteristic of this 

 southern P'lorida coast, especially on Cape Sable, 

 are the salt flats. These level expanses of hard- 

 packed sand or marl or of limestone rock are 

 flooded by high tides. Thej' support a sparse 

 vegetation of species listed above for the open 

 salt marsh with the addition of several other 

 common plants like Monanthochloe littoralis En- 

 gelm., key grass, Sporobolus virginicus (L.) Kunth, 

 drop-seed, Borrichia arborescens (L.) DC, sea- 

 oxeye, Flaveria linearis Lag., Conocarpus erecta 

 L., button wood, and its other woody associates 

 listed under mangrove swamps. 



In the marshlands of southeastern Louisiana 

 Penfound and Hathaway (1938) found gradual 

 changes in the flora from strictly salt-water to 

 strictly fresh-water habitats. They noted that 

 many marsh species have a wide range of toler- 

 ance for the salt factor and are found in brackish 

 marshes as well as in salt-water or fresh-water 

 marshes. Most of the salt-marsh species listed 

 previously occur also in brackish water, and 

 many fresh-water marsh plants are found in 

 slightly brackish water. Some of these plants of 

 brackish marshes are Typha domingensis Pers. 

 and T. latijolia L., cattails, Spartina cynosuroides 

 (L.) Roth, salt-reed grass, Phragmites communis, 

 Trin., common reed, Scirpus californicus (C A. 

 Meyer) Britt. and S. chilensis Nees & Mey., 

 bulrushes, Sagittaria lancifolia L., arrowhead, and 

 Alternanthera philoxeroides (Mart.) Griseb., alli- 

 gator-weed. The last-mentioned plant is often a 

 pest in the bayous and ditches of southern Louisi- 

 ana. Another bad pest of fresh waters, Eichornia 

 crassipes (Mart.) Solms, water-hyacinth, although 

 often floated downstream into salt water, will not 

 tolerate salt, and soon dies in even slightly 

 brackish water (Penfound and Earle 1948^. 



In southern Florida the transition from salt 

 marsh or mangrove swamp to nonlialophytic types 

 of vegetation is equally gradual or very abrupt. 

 Where salt marsh is transitional between man- 



