RED MANGROVE 



BLACK MANGROVE 



TROPICAi 

 "EST 



Viviparous 



seedli 



JUNCUS 



' ' 



I - METERS 



40 80 



SPARTINA 



6 12 18 24 



IVA 

 SPARTINA 



JUNCUS 



JUNCUS 



DISTICHLIS 



SALICO 

 BAT IS 



PAIMETTC 



jot Jfw?p!Z4f 



fllKIUiffitJii 



HARDPAN. 



Figure 25. — Diagrammatic cross sections of (A) a mangrove swamp, (B) a barrier island of the north coast, «nd 

 (C) a transect from tidal channels to flatwoods on the north coast (after Davis, 1940; Kurz and Wagner, 1957). 



The distribution of the sea grasses is contin- 

 uous around the entire Gulf (Humm, 1956; Phil- 

 lips, 1960b; Moore, 1963). Vertical zonation 

 correlates with tidal level in shallow estuarine 

 water (Fig. 26A). Diplanthera ivrightii and 

 Ruppia maritima are abundant intertidally, the 

 latter preferring a somewhat lower level than 

 Diplanthera, whereas Thalassia testidinum, Sy- 



ringodium filiforme, Halophila baillonis, and H. 

 engelmannii are found only below low water 

 levels. Syringodium and Halophila apparently 

 tolerate no exposure to air. Diplanthera and 

 Ruppia are often abundant below low water lev- 

 els, mainly where Thalassia and Syringodium are 

 sparse or absent. For example, low or unusually 

 high salinity may restrict or eliminate Thalassia 



49 



