(36) for the Mid and South Atlantic coastal regions. Whereas the Mid 

 Atlantic region has numerous shallow and open fresh-water marshes and coastal 

 salt meadows, the South Atlantic region has few of these types of marshes. 

 However, the South Atlantic has vast acreages of open sounds and bays, inland 

 fresh-water marshes, swamps, bogs, regularly flooded salt marshes, and irregu- 

 larly flooded salt marshes. Wetlands value for waterfowl, by state in de- 

 creasing order is given as (36): Maryland, Virginia, North Carolina, South 

 Carolina, Georgia, Florida, Delaware, and New Jersey. 



Ecologically, there is only an arbitrary dividing line between the bio- 

 logical communities in the two study regions. Many organisms are distributed 

 over a range wider than the bounds of just the Mid or South Atlantic. Fur- 

 thermore, certain physical and chemical phenomena occurring in the two study 

 regions are the result of conditions that have developed outside the study 

 area, notably, the Gulf Stream (23, p. 0-2). 



Not only does the temperature effect of the close-to-shore Gulf Stream 

 play a major role in biological zonation, but the sediment composition also 

 comes into play as a differentiation characteristic between communities north 

 and south of Cape Hatteras. The sandy bottoms of the Carolinian region have 

 a much higher carbonate content than areas north of Cape Hatteras. These 

 sediments support a benthic fauna which replaces some northern species with 

 ones found only in the south, such as the surf clam, Spisula raveneHi re- 

 placing its northern cousin, S. solidissima . Also, there appears to be 

 introduction of new groups and greater diversity of species as one progresses 

 from north to south of Cape Hatteras (23, p. 5-9). 



From a commercial viewpoint, surf clam harvesting is a major industry 

 in the Middle Atlantic Bight, whereas its southern counterpart, Spisula 



35 



