Chapter 10 



Reef-Dwelling Br\;ozoans of Enewetak Atoll 



ROGER J. CUFFEY* and ROBERT S. COXf 



'Department of Geosciences (Deike BIdg.), Pennsi/luania 

 State University. University; Park, Pennstjluania 16802; 

 f Museum of Paleontology. Universitij of Michigan, 

 Ann Arbor, Michigan 48109 



INTRODUCTION 

 Purpose 



The goals of this report are to list the bryozoans found 

 on the modern reefs of Enewetak Atoll, illustrate the most 

 conspicuous species, indicate their biogeographic implica- 

 tions, and summarize their ecology (particularly ecozonal 

 distributions and constructional roles). 



Significance 



The contribution made by the phylum Bryozoa to the 

 Enewetak reefs, although known in general terms (Cuffey, 

 1970, 1973, 1978), has not until now been detailed at the 

 species level for the benefit of those concerned with vari- 

 ous aspects of the Enewetak ecosystem. Such information 

 will also constitute a precise data base for comparative 

 studies of fossil reefs containing these animals. Moreover, 

 the Enewetak species are of special broader interest 

 because they represent the first modern atoll-reef bryozoan 

 fauna to be analyzed thoroughly. Their distributions thus 

 will shed light on bryozoan involvement in reefs in general. 



Collections 



Over 40 localities on Enewetak Atoll were sampled by 

 scuba diving and reef walking in late 1969. Sites were 

 selected to provide balanced but comprehensive coverage 

 of the major environments, particularly ecozones, 

 developed on the atoll (Cuffey, 1973, pp. 26, 36-38; Cuf- 

 fey, 1978, pp. 68, 72; Haggerty, Weber, Cuffey, and 

 Deines, 1980, p. 97; Basile, CuHey, and Kosich, 1984, 

 Fig. 1). However, no samples were dredged from below 

 40 m (135 ft). 



Literature 



Most useful in identifying the Enewetak bryozoans were 

 the monographs by Canu and Bassler (1927, 1929), 

 Harmer (1915, 1926, 1934, 1957), Osburn (1950, 1952, 

 1953), Levinsen (1909), and Soule and Soule (1973). 

 Additional papers too numerous to list here include occa- 

 sional relevant species descriptions as well. 



FAUNAL COMPOSITION 



Overall, 84 bryozoan species, 73 cheilostomes and 11 

 cyclostomes in 61 genera have been identified on 

 Enewetak (Table 1). Of these species, six are new, being 

 published elsewhere (Cox and Cuffey, submitted). In order 

 to refer to these without creating taxonomic problems, 

 they are denoted simply as "n. sp." followed by the pro- 

 posed trivial name in quotation marks and parentheses. 

 Among the remaining species, several generic 

 reassignments were required (incorporated in Table 1) due 

 to changes in concepts since publication of the earlier 

 monographs cited above. 



Certain species are particularly conspicuous among the 

 Enewetak bryozoans and so comprise a distinctive assem- 

 blage (Figs. 1 and 2) characteristic of this atoll and possi- 

 bly others. Such species apjjear conspicuous for different 

 reasons. Some are represented by several large colonies, 

 others by many small colonies, still others by a large total 

 substrate area encrusted, and others yet by a high propor- 

 tion of the bryozoan fauna at individual localities. These 

 species are also differently distributed within the atoll, as 

 discussed below. 



The Enewetak bryozoan species are characterized by 

 relatively few colony growth forms (Cuffey, 1973, pp. 

 29-31 and references therein). Most numerous by far (both 

 colonies and species) are encrusting cheilostomes, thin 

 sheets or crusts ranging from many square millimeters in 

 area down to a few zooecia. Most of the Enewetak cheilo- 

 stome families (Table 1) studied by Cox (1983; also Cox 

 and Cuffey, submitted) grow as encrusting sheets. A few 

 sheets consist of more than one layer of zooecia, but none 

 encountered were thickened into multilaminar nodular 

 masses (not even Celleporaria albirostris, which does form 

 such masses in Bahamian bryozoan reefs; Cuffey, Gebclein, 

 Fonda, Bliefnick, Kosich, and Soroka, 1977). More regular 



8S 



