INSHORE SITE, BOGUE SOUND, N.C. 



6km SEAWARD OF BOGUE SOUND, N.C. 



400 



500 



-i 1 r i t i i 



400 



500 



600 



700 



Wavelength (nm) 



Figure 3. Irradiance versus wavelength for an inshore site (left) in Bogue Sound, NC, and for a site 6 km offshore 

 (right). The numbers on each line indicate depth in meters. (Data provided by R. Forward, Duke University Marine 

 Laboratory.) 



commonly the nutrient limiting plant 

 growth in coastal waters. In summers, the 

 availability of dissolved inorganic 

 nitrogen may change by more than an order 

 of magnitude on a diel cycle, rising at 

 night and falling dramatically during the 

 day as it is consumed during 

 photosynthesis (Litaker et al . 1987). 

 Highly productive seaweeds like the sea 

 lettuce, Ul va , can take advantage of these 

 nitrogen spikes by rapidly storing 

 nitrogen for later use. Other more 

 massive and slower growing seaweeds like 

 Codium do not have this ability (Ramus and 

 Venable 1987), but may gain additional 

 nitrogen by establishing symbiotic 

 associations with nitrogen fixing blue- 

 green algae (Rosenberg and Paerl 1980). 



2.4 CURRENTS 



The most important offshore current 

 in the region is the Florida Current, 

 which originates in the Florida Straits 

 between Florida and Cuba. It is joined by 

 the north flowing Antilles Current, which 

 runs along the outer edge of the 

 Continental Shelf. The Florida Current 

 moves offshore at Cape Hatteras to become 

 the Gulf Stream, although this latter name 

 is often applied to the Florida Current as 

 well. The position of the Florida Current 

 varies seasonally. In the summer it moves 

 inshore, bringing warm, clear water to the 

 shelf. In the winter it is driven 

 offshore by northerly winds. When this 

 happens cold water from the north may move 



