completely. The corals trap zooplankton and protozoa, the filter 

 feeders and sediment feeders trap the phytoplankton and microflora. The 

 high effectiveness of the reef as a biologic filter and the significant 

 volume of neritic water which passes over the reef, with a high 

 concentration of plankton, allow the coral community to receive such a 

 great influx of organically bonded nutrients that it compensates for the 

 unavoidable losses of nutrients liberated in the process of metabolism 

 and carried away by the ocean water passing over the reef. The positive 

 balance of nutrients in the processes of exchange between the reef and 

 the water passing over it is apparently the key to the solution of one 

 of the most baffling peculiarities of the reef metabolism: the clear 

 accumulation of organic matter in the community, in spite of its visible 

 and tremendous output into the waters of the ocean. It is clearly 

 visible to the naked eye that the water approaching the reef is 

 transparent, with little organic sediment, while the water flowing away 

 from the reef is turbid, rich in suspended matter and organic aggregates 

 (N. B. ^c^rshall, 1968; Johannes, 1967). How is the essentially positive 

 balance maintained, in terms of organic matter, with these losses and 

 with the intensive destruction of organic matter within the community? 

 Apparently, the reef community is so organized that, being under optimal 

 conditions of illumination and temperature and having an unusually high 

 content of chlorophyll per unit area, it creates a sufficient quantity 

 of organic matter to compensate for losses due to erosion and 

 destruction. We must consider that the organic matter which is lost and 

 destroyed is poorer in nutrients than that consumed by the community 

 from the water passing over the reef. Without this mechanism, providing 

 a more positive balance of nutrients in exchange with the surrounding 

 water, the formation of the coral biogeocenoses would hardly be 

 possible. 



It is characteristic of coral communities to have extensive porous 

 surfaces, overgrown with an active and rich periphytonic microflora. 

 Its functioning occurs under optimal conditions of temperature and 

 oxygen supply. Under these conditions, similar to the conditions of the 

 air tanks of purification structures, the processes of bacterial 

 destruction are intensified, like chemical reactions on a surface of 

 porous platinum. It can be assumed that the microbial population of the 

 periphyton can assimilate those fractions of the organic matter which 

 make up the predominant portion of the total dissolved organic matter of 

 sea water, but are difficult for bacterioplankton to oxidize in the 

 pelagic zone. Therefore, although the waters of the ocean passing over 

 the reef show an increased content in labile organic matter (Sorokin, 

 1973b), it is probable that their content of a stable organic matter and 

 particularly, the nutrients bonded with it, must decrease as the ocean 

 water passes a reef. 



This system of exchange of coral communities with the water passing 

 over the reef requires further testing, but we can assume that, given 

 the tremendous area of coral reefs, the intense destructive activity of 

 the periphyton microflora is of global significance in processes of 

 biogeochemical cycling of organic matter in the world ocean. The coral 

 reef communities should be looked upon as the location of oxidation of a 

 significant portion of the stable organic matter (water humus) in sea 

 water. It should be expected that the constancy of concentration of 



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