reef. These opportunistic" species include, for example, 

 Pocillopora damicornis , Porites asteroides , fentrastrea annularis , 

 Acropora cervicornis , Stylopora pistil lata . There are species (e.g., 

 Porites porites) which populate the shoals (zones L and R) and the 

 deeper zones of the outer slope (Bu, FR), but are practically absent in 

 the surf zones on the rocky plateau ( Fl , Br, ^b, Mix). Finally, a 

 number of species occupy the slope biotopes (Bu, FR, FRS) but are not 

 encountered at depths of less than 20 m ( Agaricia grahami , 

 Kddracis mirabil is , Nycetophyl la reesi , Acropora hyacinthus , 

 Seriatopora hystrix ). The "opportunistic" forms, encountered in all 

 zones of the reef, characteristically are able to change the form of 

 their colonies, depending on conditions of illumination and 

 turbulence: branched colonies in the lagoon, and massive colonies on 

 the reef flat. 



2.3 Ecological and Physiological Features of Reef-Forming Corals 

 and Factors Influencing their Growth and Distribution 



f'ciny fundamental peculiarities of the coral communities result from 

 the ecological-physiological properties of the hermatypic corals 

 themselves. They include: the diversity of ways of feeding of corals, 

 including photosynthesis, the coupling of the process of calcification 

 with photosynthesis and the antagonistic interactions between some coral 

 species. 



The diversity of ways of feeding of madrepore corals makes them, in 

 a certain sense, a unique set of hydrobionts. They possess practically 

 all known types of feeding behavior peculiar to aquatic invertebrates 

 and have the specific morphologic structures and enzyme mechanisms for 

 this purpose. Because of the presence of symbiotic algae in the tissues 

 of their polyps they are capable of autotrophic nutrition, like green 

 plants. Their growth, like the growth of plants, depends on light also 

 because the precipitation of CdC03 and MgCOo from the water by them is 

 directly dependent upon illumination (Muscatine, Cernichiari, 1969; 

 Goreau, 1963; D. J. Barnes, 1973). The well-developed ciliar epitheliu 

 and the streamlike movement of mucus along the tentacles of the polyps 

 allow the corals to obtain nutrition from the detritus and micro- 

 organisms suspended in the water. The operation of the ciliate 

 apparatus and the presence of the required enzymes gives them the 

 ability to utilize organic matter dissolved in the water. Finally, the 

 polyps are capable of predatory feeding. The polyps catch their prey 

 using their stinging cells, then digest the prey inside their gastral 

 cavity or outside of the polyp's body by means of their mesenterial 

 filaments. These combined ways of feeding eliminate the basic factor 

 which limits the development of life in the poor surface tropical waters 

 of the ocean: the shortage of nutrients such as nitrogen and 

 phosphorus. Actually, due to their heterotrophic nutrition, the corals 

 can utilize the organic sources of nutrients (Sorokin, 1973a). The 

 processes of autotrophic production and heterotrophic decomposition of 

 organic matter, combined in a single organism, provide a closed cycle of 

 nutrients with minimum losses into the environment (Johannes et al . , 

 1970). This is not feasible for heterotrophs , the metabolism of which 

 occurs only under conditions including liberation of nitrogen (in the 

 form of urea) and phosphorus (in the form of inorganic phosphate) into 



171 



urn 



