108 



COLIN 



Fig. 12 Upper left: MIcroatolls (Porites lobata) at the north end of Chinimi Island, Enewetak. At low tide the water Is essentially 

 at the upper level of the microatolls. Secondary growth is also occurring In the central area of the top of the mlcroatoUs. Upper 

 right: Aerial view of lagoonward edge of the reef flat showing erosion at the end of the reef pavement caused by water flowing 

 across the reef flat. Lower left: Typical views of patch reefs in the Lojwa-Aomon interisland channel. Extensive sculpturing of the 

 sediment bottom is caused by currents which course through this channel at high tide. Lower right: Area of the Lojwa-Aomon 

 channel with sand built up behind (down current side of) a large patch reef. 



white sand built up. The width of these "tails" of sediment 

 decreases downcurrent of the reef. The upcurrent sides of 

 the patch reefs have the sand washed away to depths 

 equal to those on the sides of the reef. Corals and benthic 

 invertebrates are usually well developed on the upcurrent 

 end and sides of reefs. 



The deepest portions of the channel are 6 to 7 m, and 

 some patch reefs are emergent at low tide (Fig. 12). The 

 reefs in this channel have changed little in the last 32 

 years based on aerial photographs taken in 1949 and 

 1981. The major patch reefs are identifiable, but some of 

 the lagoonward patch reefs seem to have been somewhat 

 buried by sediment. 



Other interisland channels are similar. Rock surfaces 

 are heavily grazed by herbivorous fishes. Small caves and 

 overhangs off the patch reefs are lined with encrusting 

 coralline algae. These patch reefs are one of the few 

 places within the lagoon where branching coralline algae 



are found. Sediments are coarse, with predominantly large 

 foram tests, coral, and Halimeda bits. The reefs of the 

 channel between Lojwa and Alembel seem to have been 

 devastated by a storm during the last decade. Very little 

 live coral and few benthic invertebrates arc on them. Allen 

 (1972) used this channel as a primary study site for his 

 anemonefish work. One patch reef in the channel had 

 more than 75 clusters of 10 to 30 individuals of 

 Ph^isobrachia douglasi, with larger numbers of Amphiprion 

 melanopus. in an area of only 700 m^. In the summer of 

 1981, this area was re-examined for anemones and 

 Amphiprion, no anemones or anemonefishes of any type 

 were found. 



In channels farther north, corals and other inver- 

 tebrates seem healthy. Some of the channels were noted 

 for their abundance of large tridacnid clams, but many of 

 these clams have been eliminated since the repatriation of 

 the Enewetak people. 



