Coral reefs and other ecosystems dominated by benthic plant production 

 apparently have a nutritional advantage over plankton. Rather than 

 approximating the Redfield C:N:P ratio of 106:16:1, benthic plants have a C:N:P 

 ratio of about 550:30:1 (Atkinson and Smith, 1983). The nutritional implication 

 of this observation is that reefs and other benthos-dominated ecosystems can 

 produce more net C per unit of P and N availability than can plankton systems. 

 Moreover, it is well established (e.g., Webb, et aU , 1975; Wiebe, et al . , 

 1975) that coral reef communities can fix large amounts of N. Recent work 

 suggests that entire reef ecosystems, as well as other confined aquatic 

 ecosystems, can provide most of their N requirements via N fixation (Smith, et 

 a!., 1983; Smith and Atkinson, submitted). 



Thus, in any net sense, the nutritional requirements of coral reefs do not 

 differ greatly from the requirements of the plankton in the surrounding ocean. 

 We need not look for upwelling or other exogenous nutrient sources to explain 

 the survival of coral reefs. This conclusion does not imply that coral reef 

 metabolism will not respond to increased subsidy of inorganic or organic 

 nutrients. To the contrary, Canton and the Abrolhos appear metabol ical ly 

 responsive to inorganic and organic subsidies, respectively. Direct evidence 

 of reef metabolism response to increased nutrient loading has been documented 

 (Kinsey and Domm, 1974), and both community metabolism and community structure 

 of a reef system have been demonstrably altered by long-term elevation of the 

 supply of inorganic and organic nutrients (Smith, et a]_. , 1981; Brock and Smith, 

 1983). 



We can therefore return to the original question about reef survival in 

 nutrient-poor waters. Despite the rapid metabolic activity of components within 

 coral reefs, the net nutritional demands of entire coral-reef ecosystems are 

 low. The key to the success of coral reefs as biologically rich and diverse 

 entities would appear to be the accumulation of a large biomass into a network 

 of biotic communities which are effective at preventing leaks to the surrounding 



ocean. 



LITERATURE CITED 



Atkinson, M. J., and S. V. Smith. 1983. C:N:P ratios of benthic marine plants. 



Limnol . Oceanogr. 28: 568-574. 

 Brock, R. E., and S. V. Smith. 1983. Response of coral reef cryptofaunal 



communities to food and space. Coral Reefs 1: 179-183. 

 Crossland, C. J., B. G. Hatcher, M. J. Atkinson, and S. V. Smith. 1983. 



Dissolved nutrients of a high latitude coral reef, Houtman Abrolhos Islands, 



Western Australia. Mar. Ecol . Prog. Ser. (in press). 

 Eppley, R. W., and B. J. Peterson. 1979. Particulate organic matter flux and 



planktonic new production in the deep ocean. Nature 282: 677-680. 

 Kinsey, D. W. 1979. Carbon turnover and accumulation by coral reefs. Ph. D. 



thesis, Univ. Hawaii. 248 p. 

 Kinsey, D. W., and A. Domm. 1974. Effects of fertilization on a coral reef 



environment—primary production studies. Proc. 2nd Coral Reef Symp. (Brisbane) 



1: 49-66. 

 Odum, H. T. 1956. Primary production in flowing waters. Limnol. Oceanogr. 



1: 102-117. 

 Odum, H. T., and E. P. Odum. 1955. Trophic structure and productivity of a 



windward coral reef community on Eniwetok Atoll. Ecol. Monogr. 25: 291-320. 

 Sargent, M. C, and T. S. Austin. 1949. Organic productivity of an atoll. 



Trans. Amer. Geophys. Union 30: 245-249. 



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