conposition of marine sediments in south 

 Florida as taken from Ginsburg (1955) are 

 illustrated in Figure 12. Behind the reef 

 tract over 40% of the sediment was gener- 

 ated from calcareous algae, Penicillus 

 capita tus produced about 6 crops per year 

 in Florida Bay and 9.6 crops per year on 

 the inner reef tract (Stockman et al . 

 1976). Based on the standing crops, this 

 would produce 3.2 g/m-/yr on the reef 

 tract which could account for one-third 

 of the sediment produced in Florida Bay 

 and nearly all of the back-reef sedi- 

 ment. Similarly, Neuman and Land (1975) 

 estimated that Halimeda incrassata pro- 

 duced enough carbonate to supply all the 

 sediment in the Bight of Abaco in the 

 Bahamas. 



The pioneer species of the Caribbean 

 seagrasses is shoal grass, which colonizes 

 readily either from seed or rapid vegeta- 

 tive branching. The carpet laid by shoal 

 grass further stabilizes the sediment sur- 

 face. The leaves form a better buffer 

 than the algal communities and protect the 

 integrity of the sediment surface. In 

 some sequences manatee grass will appear 

 next, intermixed with shoal grass at one 

 edge of its distribution and with turtle 

 grass at the other, rianatee grass, the 

 least constant member of this sequence, 

 is frequently absent, however. 



Manatee grass appears more commonly 

 in this developmental sequence in the Car- 

 ibbean islands and in the lower Florida 



SE 



REEF TRACT 



FLORIDA BAY 



NW 



Outer 

 Reef Arc 



CORAL KNOLL 



Back Reef 



MUD BANK 



MAINLAND 



Figure 12. Origin of sedimentary particles in south Florida marine waters (modified 

 from Ginsberg 1956) . 



36 



