HYDROGRAPHY OF THE MARINE WATERS 65 



sink to the bottom in shallow water their contained nutrients are not drained 

 from the region of photosynthesis. 



The sounds of North Carolina comprise about 2,500 square miles of 

 typically productive shallow waters, seldom as much as 20 feet deep. A 

 complete range from sea water to fresh adds to the potentialities since vast 

 areas meet the salinity requirements of almost any marine, brackish water, 

 and migratory species. Correlated with the latitude is a mild seasonal tem- 

 perature change which, if other things are equal, provides a longer growing 

 season than is expected where it is colder. Rivers draining about 30,000 

 square miles, almost all within the Coastal Plain and Piedmont Plateau, flow 

 into these sounds. This is small compared to the 67,505 square miles (Wells, 

 Bailey and Henderson, 1929) draining into Chesapeake Bay with its surface 

 area of 2,800 squares miles (Cowles, 1930), and it may be that the lesser 

 Carolina fishery is partially the result of proportionate differences in nutrients 

 contributed by drainage. On the other hand, too little is known to accept such 

 a conclusion. The difference in harvest may not be correlated with differences 

 in potential harvest. It may be that the barrier beach bordering the sounds 

 creates a compensating reservoir effect holding important nutrients in more 

 of a closed production system. 



Offshore from the North Carolina barrier beach there are about 14,000 

 square miles of shallow water (to the lOO-fathom curve which is the edge of 

 the continental shelf). Because of the adjacent Florida Current of the Gulf 

 Stream System, the temperature on this shelf has an unusually moderate 

 seasonal change for this latitude. For this reason apparently, the region is an 

 important winter retreat for migratory fish from the north, and perhaps from 

 the south as well. In addition, this coast and its large adjacent sounds serve 

 as the nursery area and center of dispersal for some species. 



Some nutrients are inevitably added to these shelf waters from the rivers 

 and sounds but the contributions from oceanic circulation are unknown. 

 There are indications of counter-clockwise eddy currents over the shelf from 

 the edge of the Gulf Stream System which, among other things, would tend 

 to bring waters from off Chesapeake Bay. There is no known upwelling but 

 biologically similar effects may be produced if the frictional stress of the 

 Florida Current forces eddies of deep, nutrient-rich water into the coastal 

 region. 



With a figure for basic productivity it would be possible to estimate the 

 total production of the 16,500 square miles of sounds and shallow oceanic 

 waters of North Carolina. Riley (1944) states, "The best determinations for 

 open oceanic waters average about 340 tons of carbon per km^. per year [881 

 tons of carbon per square mile per year]. . . ." The same author (1941) says 

 there is no major difference in productivity associated with latitude but that 

 local conditions greatly modify productivity. Because of North Carolina's 



