The intensity of respiration of the community of microorganisms 

 populating the coral sands of an unpolluted living reef is, on the 

 average, comparable to the magnitude of photosynthesis (Table 7). 

 Respiration is significantly greater than photosynthesis in the sands 

 deposited directly beneath the living coral, and in the loose sediment 

 of a polluted reef (Sorokin, 1973e). Each day, photosynthesis causes 

 the renewal of about 1% of the total organic carbon in the sand. 



The intensity of photosynthesis of the coral community is 3-10 g 

 C/m per day (Sargent, Austin, 1953; Odum, Odum, 1955; Odum et al . , 

 1959; Kohn, Helfrich, 1957, Kinsey, Kinsey, 1967). This is 30-50 times 

 higher than the production of phytoplankton in the column of 

 oligotrophic waters surrounding the reef. 



The most important component in the periyhytonic communities of the 

 reef is bacteria. Their population is I-5'IO cl/g in the sand, 3-5*10 

 in periphyton, and up to lO'lO in regenerative sediment (Table 7). 

 Such a high population of bacteria can be found only in the bottom 

 sediments of eutrophic lakes. The number of bacteria in the 

 regenerative sediment of the polluted reef in Kaneohe Bay, Hawaii, was 

 close to the number in the active silt of sewage purification plants 

 (Sorokin, 1973e). 



f'bst of the microflora of the periphytonic overgrowth of solid 

 substrates (dead coral, the rocky reef flat) consist of mobile 

 filamentous flexibacteria such as Leucotrix , as well as catenulate 

 bacteria such as Cladotrix and Crenotrix , which usually develop in 

 bodies of water rich in organic matter. 



The biomass of bacteria in the periphyton and in bottom sediments 

 of the coral reefs varies within 50-500 ug C/g, or about 5 g/£ of wet 

 biomass (2-3% of the total organic matter of the substrate). The 

 production of microflora in the bottom sediments and periphyton is 20- 

 200 pg C/g per day, the P/B ratio averages 0.2-0.7. Thus, the matter of 

 the benthic microflora of the coral reef is totally renewed in 2-5 days. 



2.5 Structure and Productivity of the Planktonic Communities over 

 Coral Reefs 



The plankton of reefs is relatively much poorer than the benthos, 

 its biomass and production being many times lower than that of the 

 benthic communities. Thus it mibht be concluded that the plankton is 

 insignificant in the energetics and functioning of the ecosystem of the 

 coral reef. However, this conclusion would be erroneous, because the 

 predominant benthic fauna of the reef are fil ter- feeders and sediment 

 feeders which consume the plankton (Glynn, 1973). The underevaluation 

 of the significance of the plankton is partially due to a failure to 

 consider the main producing and nutritive component of the plankton in 

 coral communities--the bacterioplankton. The plankton and the organic 

 matter dissolved and suspended are the key links by means of which the 

 individual biotopes of the reef Are energetically connected, thus 

 forming the unified coral reef ecosystem. This energetic connection is 

 achieved both by direct transfer of the larval planktonic stages, which 

 serve as a source of nutrition for the coral, and by transfer of 



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