the environment. These products of heterotrophic metabolism are 

 utilized in the autotrophic biosynthesis of the zooxanthellae, without 

 leaving the organism of the polyps. It has been established that 

 hermatypic corals, having zooxanthellae, excrete much less inorganic 

 phosphate per unit of biomass as compared with hermatypes, which do not 

 have zooxanthellae, or with other marine animals (Yonge, Nicholls, 1931; 

 Pomeroy et al . , 1974). 



An intensive photosynthesis (Table 5) is inherent for the corals, 

 in spite of the fact that the biomass of the zooxanthellae represents 

 only a few percent of the biomass of the polyps (Table 6). The mean 

 intensity of photosynthesis of madrepore corals is 0.2-0.3 mg C/g of dry 

 matter of the colony, or about 5 mg C/g of organic matter of the polyps 

 per day. The production of photosynthesis usually exceeds the losses of 

 polyps to metabolism by 1.5-3. Therefore, for most corals inhabiting 

 areas with optimal conditions of illumination, energy losses can be 

 completely compensated for by photosynthesis. When this occurs, about 

 half of the organic matter synthesized by the zooxanthellae is found 

 within a few hours as part of the tissue of the polyps (Muscatine, 1967, 

 1973i Von Holt, Von Holt, 1968). Such an intensive autotrophic 

 production of organic matter is achieved due to a high intensity of 

 photosynthesis of the zooxanthellae, the daily P/B coefficient of which 

 is about 2 to 5. 



In addition to the production of organic matter, the functioning of 

 the zooxanthellae enhances the process of calcification in the 

 construction of the skeleton of hermatypic corals, and so of the growth 

 of the reef itself. With the use of isotope Ca, it has been shown that 

 the process of accumulation of calcite in the skeleton of the corals 

 depends directly upon the intensity of the light and the presence of 

 zooxanthellae (Goreau, Goreau, 1960). The addition of specific 

 photosynthesis inhibitors to the water inhibits also the process of 

 precipitation of calcium carbonate in the skeleton of the corals. 



The capability of corals to feed on microplankton has been proven 

 experimentally, using phytoplankton and bacteria labeled with C-"-^ or S-^^ 

 (DiSalvo, 1973; Sorokin, 1973e). This sedimentation mode of feeding of 

 corals is based on trapping of the nutritious particles (bacteria, 

 algae, protozoa) by the mucous surface of the body of the polyp and 

 their transfer by the action of cilia to the mouth (Yonge, 1968; 

 Muscatine, 1973). Apparently, the coenosarc (the tissues covering the 

 surface of a colony between polyps) also may participate in the process 

 of sedimentation feeding, which may significantly increase the intensity 

 of sedimentation feeding (Goreau, 1959). According to the observations 

 of Goreau, the nutritious particles which precipitate onto the mucous 

 surface are transferred toward the polyps by the movement of the mucus. 



Determinations of the intensity of the sedimentation way of 

 heterotrophic feeding of massive species of coral (Pocil lopora , Pori tes , 

 Fungia , Montipora ), using bacteria labeled with C-^^ as the food, have 

 shown that this method of nutrition can compensate for up to 10% of the 

 daily losses in metabolism (Fig. 4). The phytoplankton is consumed and 

 assimilated by the polyps much more poorly than the bacteria, since the 

 polyps are not capable of digesting plant cells (Yonge, 1930). 



172 



