The area beneath the curve in Figure 

 15 was integrated over a 1-year period to 

 yield a total of 8,168 gOa/m^/yr consumed 

 by the oyster reef community, equivalent 

 to 27,036 kcal/m2/yr, assuming a respira- 

 tory quotient of 0.85. This estimate of 

 the community metabolic energy demand by 

 the reef community is conservative in that 

 it is derived by multiplying hourly rates 

 by 12 hours, with the assumption that 

 little respiratory activity occurs during 

 reef exposure at ebb tide. However, Lehman 

 (1974) reported a significant metabolic 

 rate of exposed oyster reefs by using an 

 infrared gas analyzer to detect CO2 re- 

 leased from enclosed reef samples. This 

 measured rate was about 20% of the rate 

 measured by oxygen changes during inunda- 

 tion. Total community metabolism in the 

 Georgia reefs is partitioned among oys- 

 ters, other macrofauna, small organisms, 

 and chemical oxygen demand. 



Macrofaunal Respiration 



The contribution of each species of 

 macrofauna to total community oxygen con- 

 sumption at a given temperature is a func- 

 tion of its proportion to the total bio- 

 mass, its size-frequency distribution, and 

 the relationship between rate of respira- 

 tion and size of an individual. Small rare 

 species contribute little to total biomass 

 and cannot contribute significantly to 

 total Qxygen uptake (QO2); large rare spe- 

 cies, on the other hand, can often alter 

 total oxygen uptake (Smith 1971). Banse 

 et al. (1969) and Pamatmat (1968) con- 

 cluded that the most reliable method of 

 estimating relative importance of various 

 macrofaunal species in terms of total com- 

 munity respiration is to multiply mean ash 

 free dry weight (afdw) per species by the 

 density of that species in the community. 

 By this criterion, the oyster reef commu- 

 nity members were ranked in terms of 

 macrofaunal metabolic importance, as shown 

 in Table 6. The two species that comprised 

 95% of total biomass, Crassostrea virqin- 

 ica and Guekensia demissa . contributed 

 87.5% and 7.5% of total community biomass, 

 respectively. 



The respiration of oysters accounts 

 for approximately 50% (48.1%), or about 

 13,000 kcal/mVyr of the total reef com- 

 munity respiration. Total oxygen require- 

 ments (hence energy requirements) of non- 

 oyster macrofauna was thus estimated to 



account for only 10% of the total reef 

 requirements, about 800 g02/m^/yr or about 

 2,700 kcal/m^/yr. This latter figure is 

 similar to the total oxygen uptake rate of 

 the subtidal soft bottom community near 

 Sapelo Island (Smith 1971). 



Nonoyster macrofauna were divided 

 into 14 species or groups of related spe- 

 cies, and estimates of the annual oxygen 

 consumption rates were derived experimen- 

 tally (Bahr 1974), as shown in Table 6. 



Microbial and Meiofaunal Respiration 



The metabolism of small consumer 

 organisms represents 22% of the total reef 

 community metabolism (Bahr 1974). This 

 estimate is approximate since it is based 

 on the difference between total community 

 oxygen consumption and the sum of esti- 

 mated macrofaunal and chemical oxidation 

 rates. 



The large surface area of an oyster 

 reef (at least 50 times the area of a 

 plane surface) provides a large surface 

 for aerobic bacteria as well as for epi- 

 fauna (see Section 3.1), and thus this 

 estimated large energy requirement, 1,600 

 g02/m2/yr (5,400 kcal/mVyi"), is not too 

 improbable. 



Chemical Oxidation 



Bahr (1974) estimated that the pro- 

 portion of total reef community oxygen 

 uptake accounted for by the chemical oxi- 

 dation of reduced compounds (20%) was only 

 slightly lower than microbial metabolism. 

 This estimate reflects the continual 

 release of reduced compounds from the 

 anaerobic decomposition of reef-derived 

 organic matter. 



Summary 



The seasonal energy partitioning 

 estimates for the entire reef community 

 are depicted in Figure 16. To summarize, 

 the reef community converts about 3 x 10** 

 kcal/m2/yr to heat, which represents the 

 net "cost" to the ecosystem of supporting 

 the reef community. Systems theory would 

 indicate that this cost is repaid by the 

 reef community in the form of feedback 

 services. For example, the reefs contin- 

 ually release plant nutrients, ammonia 

 and phosphorus-containing compounds; they 



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