functional importance in the marsh system 

 resides more in terms of nutrient (phos- 

 phorus) cycling than in energy flow. He 

 estimated the mean density of Guekensia in 

 the entire marsh at 7.82 animals/m^, 

 whereas in oyster reefs in Georgia, this 

 mussel averaged over SOO/m^. Ischadium 

 recurvum was found to be 10 times more 

 numerous in reefs than was Guekensia (see 

 Table 4), and together these two species 

 contributed 9.5% of total macrofaunal bio- 

 mass (112.08 g/m2). Dame (1979) reported 

 about 7 Guekensia/ m^ in South Carolina 

 reefs and about 71)0 Ischadium/ m^, or two 

 orders of magnitude greater than Gueken - 

 sia . 



Anemones 



Anemones are sessile epibenthic sus- 

 pension feeders that have soft bodies and 

 are extremely vulnerable to dessication. 

 Thus, they are not normally considered 

 intertidal organisms. Their common occur- 

 rence in reef samples in Georgia (Bahr 

 1974) attests to the capacity of oyster 

 reefs to retain water above MLW and to 

 extend the vertical distribution of such 

 creatures. Dame (1979) did not report any 

 anthozoans in South Carolina reefs, but 

 this group could have been overlooked in 

 preserved samples. 



Polychaetes 



Polychaetes are generally one of the 

 dominant groups in benthic systems because 

 of their contribution to total biomass or 

 to numbers, or both; but they are usually 

 considered infauna, with some obvious 

 exceptions such as the serpulids, which 

 produce encrusting calcareous tubes. Smith 

 (1971) found that polychaetes constitute 

 the major portion of macrofauna in a sub- 

 littoral community near Sapelo Island. In 

 the oyster reef community, polychaetes 

 accounted for only 0A% of the total bio- 

 mass, most of which was contributed by one 

 species, Neanthes succinea , which averaged 

 1,739 animal s/m^, compared to 281 /m^ in 

 Long Island Sound (Sanders 1958). 



The three most abundant small poly- 

 chaetes, Polydora websteri , Heteromastus 

 filiformis . and Streblospio benedicti , 

 together compri sed only about 0.01% of 

 total macrofaunal biomass. There is a 

 relative dearth of polychaetes in this 



reef system compared with other communi- 

 ties. This is perhaps related to the pre- 

 dominantly epibenthic nature of the reef 

 community and to the absence of a substan- 

 tial layer of aerobic sediment. Dame 

 (1979) found significant numbers of Heter- 

 omastus in South Carolina reef samples, 

 but he did not find many of the other two 

 small polychaetes, probably because of the 

 large mesh size used to screen his benthic 

 samples. 



Amphipoda 



Amphipods are more numerous and di- 

 verse in sublittoral oyster beds than on 

 intertidal reefs since, in the latter sit- 

 uation, tidal pools are not available to 

 sustain them during ebb tides. Grackles 

 were observed feeding on oyster reefs, 

 probably preying on amphipods and mud 

 crabs (Bahr 1974). Dame (1979) found rel- 

 ativity few amphipods in South Carolina 

 oyster reef samples, and only one species, 

 Melita nitida , was reported. 



Accidentals 



Hydroids, bryozoans, flatworms, and 

 sponges, all commonly associated with sub- 

 tidal oysters (Guida 1976), were so rarely 

 encountered in Georgia oyster reefs as to 

 be considered "accidentals" in the reef 

 community. 



3.3 REEF COMMUNITY ENERGETICS 



The energy requirements, expenditures 

 and an overall energy budget for reef oys- 

 ters are discussed in the Appendix. The 

 additional energy requirements of nonoys- 

 ter members of the reef community are ad- 

 dressed in the following section. The data 

 used are primarily those reported by Bahr 

 (1974). 



The best available estimate of total 

 energy requirements of the reef community 

 is the rate at which a unit area of reef 

 consumes oxygen (community respiration 

 rate). A sine curve fitted to oxygen con- 

 sumption of the total reef community in 

 Georgia for a 1-year period is depicted in 

 Figure 15. The variation in community oxy- 

 gen uptake ranged from approximately 6 to 

 50 g02/m2/day over a temperature range of 

 9° to 30° C. 



48 



