144 



KOHN 



TABLE 4 



Distribution and Biomass of Algae Across the Windward 

 Reef Platform at Enewetak Islet' 



'Data from Bailey-Brock, White, and Ward, 1980. Figures in body of table 

 are percent cover. 



flncludes Acetabularia clauata. 

 :t:lncludes Ceramium sp. 



inshore (Table 4). The coralline Jania capillacea and the 

 brown Sphacelaria sp. are predominant algae in the 

 encrusting zone (Miller, 1983). 



Benthic Fauna: Abundance and 

 Distribution 



Protozoa 



Foraminifera containing symbiotic algae are the largest 

 and most prominent benthic intertidal Protozoa at 

 Enewetak. They are probably restricted to cracks and 

 holes in the reef rock that afford both adequate light for 

 photosynthesis and shelter from grazing fishes and inver- 

 tebrates (Lipps and Delaca, 1980). These authors reported 

 the presence of several genera at Enewetak but did not 

 indicate which were intertidal. Hirshfield, Charmatz, and 

 Helson (1968) noted that the family Miliolidae comprised 

 82% of the Foraminifera on the Parry (Medren) Island; 

 seven rarer taxa were also present. Foraminifera containing 

 zooxanthcllae are often important contributors to both cal- 

 cification and organic carbon fixation in coral reef associ- 

 ated communities (Smith, 1977). Benthic Foraminifera are 

 sufficiently abundant occasionally to be important food 

 items of some xanthid crabs (Havens, 1974) and fishes 

 (Hiatt and Strasburg, 1960). 



Porifera 



Clionid sponges that excavate chambers in the herma- 

 typic coral Pontes lutea on interisland platforms are ecolog- 



ically the most important Porifera of the Enewetak inter- 

 tidal and shallow subtidal zones. The dominant species are 

 Aka sp. cf. A. diagonoxea and Cliona sp. cf. C. quadrata 

 (Highsmith, 1981). They initiate burrows as cylindrical 

 excavations about 200 fim in diameter and 300 nm deep. 

 The burrow is then extended 2 to 3 mm, after which it is 

 expanded into a chamber 5 mm or more in diameter. 

 Chambers of this size are found within 3 months of expo- 

 sure of dead coral skeletal surface, especially on the under- 

 sides of P. lutea microatolls. Highsmith (1981) showed that 

 sponges are the most common infaunal associate (in 86% 

 of coral heads examined) and the most important bio- 

 eroders of corals at Enewetak. The overall effect of this 

 bioerosion is not known. Smith (1973) suggested that the 

 rate of CaC03 removal by sponges is probably something 

 less than one-fourth the rate of calcification. 



Cnidaria 



The predominant cnidarian of low intertidal ( + 0.15 to 

 0.3 m; Havens, 1974) interisland platforms is the herma- 

 typic coral Porifes lutea. Here its typical growth form is 

 the microatoll. As described by Highsmith (1980), "the 

 tops of these massive corals are killed by prolonged expo- 

 sure during seasonally low tides. The coral tissue around 

 the periphery of the head survives and continues to grow 

 radially outward resulting in the characteristic microatoll 

 form." Pontes lutea microatolls tend to become detached 

 from their substrate because (1) their inability to maintain 

 live tissue under shaded portions of the jseriphery results 



