Transition from lagoon to barrier reef is abrupt and characterized 

 by a sharp decrease in depth and change in bottom characteristics. 

 The reef is extremely rough with numerous corals and reef debris 

 up to 3 to 4 feet across (Plate 6). The most shallow portion of 

 the reef is 300 to 400 feet wide and, in some areas, awash at low 

 tide. 



Immediately seaward of the reef a sharp increase in depth occurs, 

 and at 14 to 16 fathoms the break-in-slope is reached. Below the 

 break-in-slope the bottom is essentially vertical to 100 fathoms. 



Immediately adjacent to the seaward side of the reef, on the outer 

 platform, are coral heads ranging from 2 to 10 feet high which present 

 an extremely angular, irregular, hard bottom. Seaward, this 

 association gives way to a spur and groove configuration in which 

 the coral heads are dissected into channels 15 to 20 feet deep and 

 wide. The bottoms of the grooves or channels are hard and covered 

 by a thin, shifting veneer of sand, loose cobbles, and boulders. 

 The spur and groove configuration is obscured near the break-in- 

 slope owing to an increase in sedentary organisms. 



In essence, the barrier reef and the outer platform consists of 

 a hard, irregular bottom incised by channels and grooves, and 

 reflects an area subject to vigorous water turbulence. 



BIG WOOD CAY (SITE 3) 



The survey at Site 3 commenced ashore at approximate latitude 

 24°20'18.3"N., and longitude 77°41'00.4S"W. , 300 yards west of the 

 eastern shoreline on the southeast tip of Big Wood Cay. Bathymetry 

 along the survey track of 058° to the break-in-slope is shown 

 in Figure 7. 



Loose sand overlying a well-indurated limestone composes the 

 backshore. Immediately west of the dune crest a stand of palm 

 trees gives way to thick, dense shrubs (Plate 7). A few hundred 

 feet inland the sand covering is absent and rough, angular lime- 

 stone supports thickets of mangroves and other low brush. 



16 



