Throughout this document, oyster "reefs" 

 are strictly defined as "the natural 

 structures found between the tide lines 

 that are composed of oyster shell, live 

 oysters, and other organisms and that are 

 discrete, contiguous, and clearly distin- 

 guishable (during ebb tide) from scattered 

 oysters in marshes and mud flats, and from 

 wave-formed shell windrows." Intertidal 

 reefs, as defined here, are also distinct 

 from natural and planted subtidal oyster 

 populations. 



Ecologists' opinions differ as to 

 whether benthic communities (and some 

 other communities) exist as tightly inter- 

 active and interdependent systems of orga- 

 nislns, or whether such communities are 

 merely loose, chance associations to which 

 member species belong solely by geographic 

 accident. A proponent of the former argu- 

 ment long ago chose the oyster community 

 as an example of a biocoenosis, or inter- 

 active community (Mobius 1883). Whether or 

 not some species that occur in the oyster 

 reef community are dispensable, the Ameri- 

 can oyster is the "keystone" species (or 

 indispensable) in the sense intended by 

 Paine (1959) when he coined the term. 



Specific objectives of this report 

 are as follow: (1) to synthesize a state- 

 of-the-art systems view of the oyster reef 

 community in the study area from existing 

 literature; (2) to address the effects of 

 various potential cultural and natural 

 perturbations on the oyster reef subsys- 

 tem, including pollution effects, physical 

 alterations to the estuary, and natural 

 changes; (3) to condense the above infor- 

 mation into conceptual ecosystem models 

 constructed at a level understandable by a 

 variety of readers, including those inex- 

 perienced in using ecological models. 



The American oyster is the quintes- 

 sential or most typical estuarine animal. 

 It can tolerate a wide range of salinity, 

 temperature, turbidity, and oxygen ten- 

 sion, and therefore is adapted to the pe- 

 riodic and aperiodic changes in water 

 quality that characterize estuaries. Some 

 physiological and anatomical reasons for 

 its adaptive plasticity are described in 

 Chapter 2, which treats the autecology of 

 the oyster. Other aspects of the success 

 of the intertidal oyster are related to 

 its colonial lifestyle and mutual inter- 

 dependence and cannot be comprehended from 



information gathered for individual oys- 

 ters. Chapter 3 is devoted to a discus- 

 sion of the entire reef community. Chap- 

 ter 4 discusses the reef's role in the 

 coastal ecosystem and Chapter 5 presents 

 three models expressing the reef's role. 

 Chapter 6 summarizes the other chapters 

 and gives implications for management. 



This chapter's remaining sections de- 

 scribe the specific estuarine environment 

 of the oyster reef community. They in- 

 clude the physical, chemical, and biolog- 

 ical settings. 



1.2 GENERAL CHARACTERISTICS 

 OF THE SOUTH ATLANTIC BIGHT 



The geographic area on which this 

 profile primarily focuses is the portion 

 of the South Atlantic Bight, extending 

 along the southeastern coast of the United 

 States between Cape Fear , North Caro- 

 lina, and Cape Canaveral, Florida. This 

 section of the southern coastal plain ex- 

 hibits a continuum of change in coastal 

 morphology, but is characterized by exten- 

 sive lagoon-marsh systems and estuaries 

 bound at their eastern extent by barrier 

 island complexes. The morphology of coast- 

 al barrier island systems and extent of 

 the lagoon-marsh are the results of a com- 

 plex interplay of physical and biological 

 processes. 



In general, this area can be consid- 

 ered a mixed-energy coast (Hayes 1975) 

 since coastal processes and morphologies 

 are determined by the varying influence of 

 both waves and tides. Wave and tidal con- 

 ditions in this area are largely a func- 

 tion of the changing profile of the inner 

 continental shelf (Hayden and Dolan 1979; 

 Hubbard et al. 1979). Average wave heights 

 decrease from a maximum of 1.2 m (4 ft) 

 along the North Carolina coast to a mini- 

 mum of 0.1 m (0.5 ft) along the central 

 Georgia coast (Hubbard et al. 1979). Where 

 the shelf is broad, nearshore wave heights 

 are reduced through frictional loss caused 

 by shoaling on the ocean floor shelf. 



Shelf width, combined with the arcu- 

 ate shape of the coastline, also influenc- 

 es tidal range. The southern coast of 

 North Carolina is classified as a micro- 

 tidal coastline (Davies 1964), with semi- 

 diurnal tides that range between and 2 m 



