L. HILLIS-COLINVAUX 



Fig. 100. Surge channel behind the algal ridge on the seaward reef of Enewetak Islet, 

 Enewetak Atoll. Halimeda grows, to some extent at least, in the passages and 

 caverns of these channels, although it is not shown here. The algal growth on the 

 rock surface includes blue-greens, ulotrichean filaments and lush green skeins of 

 Bryopsis. 



reef, and Ladd in his visits of 1950 and 1952 found this and some of the 

 other reefs of the windward shores drab (Emery et al., 1954), a condition 

 which has been attributed both to rate of reef growth, and to the effects 

 of bombardment and release of fuel oil during the Second World War. 

 At the time of my visit to the area in 1975 the macrofiora was sparse. 

 There was, however, a good growth of smaller algae with much associ- 

 ated fauna. Many of the algae grew in short spongy turfs, and as green 

 and blackish slimy rock coatings. The only Halimeda found was 

 macrophysa, living in crevices behind the algal ridge, in water several 

 centimetres deep at low tide. 



In the abandoned limestone quarry of the inner back-reef of 

 Enewetak Islet sizeable populations of the sprawlers distorta and 

 gracilis grew, as well as macrophysa, and a bushy form of minima. The 

 water depth is 1-1-3 m at low tide. This setting is more protected than 

 the open reef flat. 



