ECOLOGY OF ROCKY COASTS 



337 



whilst the belt below is dominated by oyster and Mytilus. In this 

 respect the warm water coast here is similar to the warm water east 

 coast of the Auckland Province in New Zealand (see table p. 336). 

 The lowest belt on these U.S. shores is algal and dominated by species 

 of Gracilaria, Ulva and Enter omorpha. The sub-littoral fringe is 

 represented by Grateloupia and Sargassurn. The Stephensons have 

 suggested that a mean winter water temperature of 10° C should 

 form the hmit between cold temperate and warm temperate shores. 

 Bennett and Pope (1953) in Austraha, however, regard the belts on 

 the shores of Victoria (see table p. 336) as typically cold temperate, 

 but the mean winter temperature of the water is 11 •8'' C. In the 

 event it may prove impossible to set an exact temperature at which 

 the transition takes place. 



Our knowledge of zonation in the tropical and sub-tropical 

 coasts is much less extensive. There are, however, a few examples. 

 Thus, in the tropical waters of the Caribbean, algae replace 

 animals as the major dominants in the belts. 



Supra-littoral 

 fringe 



Mid-littoral 



Sub-littoral 



Florida Keys 



Bare white belt 

 Grey belt 



(Bostrychia) 

 Black belt 



Jamaican Keys Jamaica 



Bare Flat limestone or 



Red — Herposiphonia Beachrock 



Myxophyceae or 

 Black — Myxophyceae Gelidium- 



(Myxophyceae) 



Yellow belt Algal turf 



(algal turf) Cladophoropsis 



Lower platform Herposiphonia 

 (Valonia) Champia 



Centroceras, Clado- 

 phoropsis, Caulerpa 



Reef flat. Coral Coral and mixed 

 and mixed algae (Mostly 



algae (mostly Siphonales) 

 Siphonales) 



Bostrychia 



Algal turf 

 (Padina) 



Valonia 



Coral and mixed 

 algae (Sargas- 

 sum and 

 Siphonales) 



This may be compared with zonations recorded from a range of 

 shores on the Gold Coast where again algae are predominant, 

 especially on exposed coasts. 



