INTERTIDAL ECOLOGY 



155 



size-frequency distributions were shifted significantly 

 toward larger shell lengths after the typhoon, suggesting 

 size-selective mortality with smaller individuals more likely 

 to die, as in the case of rainstorm-induced mortality. 



CONCLUSION 



The intertidal zone, populated almost exclusively by 

 plants and animals of marine origin, exposes these organ- 

 isms to the harshest physical conditions and widest ampli- 

 tudes of fluctuating physical variables of any oceanic 

 environment. On an atoll, heating and desiccation from 

 tropical insolation, inundation by heavy rain, and storm 

 waves exacerbate even these stringent conditions. 

 Nevertheless, complex and highly productive biotic com- 

 munities characterize the intertidal comfx>nent of atoll 

 ecosystems. At Enewetak, studies over the past 25 years 

 have documented the major outlines of community organi- 

 zation and have revealed some important, unexpected 

 characteristics. This chapter has summarized the 

 knowledge they have provided of the identity of the major 

 organisms present, their population densities, distribution 

 patterns, temporal variations, habitat requirements, and 

 trophic roles and interactions. However, a satisfactory syn- 

 thetic model of intertidal community structure and 

 processes will require more intensive future studies of 

 trophic dynamics and of both biological and physical fac- 

 tors affecting the composition and relationships of the 

 biota. 



Note Added in Proof 



Recent analysis of the microhabitats and diets of a 

 large sample of three species of Drupa collected by Paul 

 Leviten on the seaward, windward platform in 1972-74 

 amplifies the study of Bernstein (1974) reported in the text 

 (Thomas and Kohn, 1985). 



Drupa morum. the largest species (mean shell length 

 25 mm) and the one occupying the most exposed, sea- 

 ward microhabitats, preys primarily (65% of diet) on nereid 

 polychaetes (Cerafonereis mirabilis and Pehneresis singa- 

 poriensis) and secondarily (23%) on eunicid polychaetes 

 {Eunice afra and Li/sidice collaris). Drupa hcinus (mean shell 

 length 22 mm) is more widely distributed across the plat- 

 form. In its more exposed microhabitats it preys primarily 

 on vermetid gastropods (Dendropoma gregaha) and per- 

 haps other species of the genus. In inner, more protected 

 areas it preys more frequently on nereids, mainly C mira- 

 bilis. Overall its diet comprised 44% vermetids, 42% 

 nereids, 5% other polychaetes, and 9% crustaceans. Drupa 

 arachnoides (mean shell length 20 mm), the most inshore 

 species, preys almost exclusively (92%) on C. mirabilis. 

 Overall, predator size and prey size were positively 

 correlated. 



untimely death from cancer in 1980 at age 36 deprived 

 tropical marine ecology of a gifted and productive scientist. 

 Leviten was educated at the Universities of Miami (B.S 

 and M.S.) and Washington (Ph.D.). He was a Queen's Fel- 

 low for 2 years in Australia, and he served on the faculties 

 of the University of California at Irvine and Santa Barbara. 



Fig. 5 The late Dr. Paul J. Leviten at work in the Mid- 

 Pacific Research Laboratory, Enewetak. 



Leviten was the sole author or co-author of four major 

 papers, all of which repKDrted research performed at 

 Enewetak. His research blended mastery of theory, quanti- 

 tative field ecology, and devotion to knowledge of the 

 Mollusca in harmonious proportions, and his accomplish- 

 ments contributed significantly to all of these. This chapter 

 is therefore dedicated to his memory. 



ACKNOWLEDGMENTS 



Support by NSF Grants DEB 77-24430 and 81-17945, 

 and logistic support from ERDA Contracts AT(29-2)-26 

 and AT-(26-l)-628, arc gratefully acknowledged. I thank 

 the following directors for providing research facilities and 

 encouraging my research at Enewetak: R. W. Hiatt, 

 S. V. Smith, E. S. Reese, P. Helfrich. I thank J. T. 

 Harrison for discussion and criticism. 



REFERENCES 



DEDICATION 



Much of the author's research at Enewetak was carried 

 out in collaboration with Paul J. Leviten (Fig. 5), whose 



Ayal, Y., and U. N. Safriel, 1982, Role of Competition and Pre- 

 dation in Determining Habitat Occupancy of Cerithlidae 

 (Gastropoda Prosobranchia) on the Rocky, Intertidal, Red Sea 

 Coasts of Sinai, Mar Biol., 70: 305-316. 



