102 



COLIN 



Views of Lagoon pinnacle reefs. Upper left and lower 



left: Coral development (Pontes rus) on the western side of "Tunnel Pinna- 

 cle" (Fig. 6) with extensive development of the plate-like growth form of 

 this cora! from about 5 to 18 m depth. Upper right: Typical view of 

 lagoon pinnacle (Tunnel Pinnacle) at about 25 m depth with the coral 

 Pauona cactus and the sponge Cribochalina olemda visible. Much of the 

 substratum is devoid of cora) and has an algal community growing on the 

 rock surfaces. Lower right: The algae Asparagopsis taxiformis which is 

 abundant on most lagoon pinnacle and margin patch reefs. 



great transition. The width of the lagoon nriargin varies 

 considerably from only a few hundred meters at the south 

 end of Enewetak Island to over 1 km from Lojwa north to 

 Engebi and Boken. The deeper portions are similar to the 

 deep lagoon, and because of their accessibility to scuba 

 divers, are an excellent area for studies relevant to the 

 deep lagoon. From about 6 m to 15 to 20 m depth, the 

 bottom has areas of relatively steep sediment slopes, often 

 at the angle of repose; abundant patch reefs, often with 



relatively high vertical relief, high coral diversity, and abun- 

 dant fish populations. 



The windward lagoon margin is strongly influenced by 

 the reef flat. Areas of high water transport across the reef 

 flat ("rips"), found at the ends of islands and also along 

 interisland reef flats, affect the distribution of sediments 

 and patch reefs on the lagoon margin. In the lee of the 

 large islands (Enewetak, Medren, Runit) patch reefs are 

 somewhat "dead," with relatively low coverage of corals. 



