Atoll Research Bulletin No. 519 Sponges on Mangrove Roots, Twin Cays, Belize: Early Stages of Community Assembly by Janie Wulff Issued by National Museum of Natural History Smithsonian Institution

A combination of transplant experiments and provision of recruitment surfaces has been initiated to determine the degree to which differences in sponge diversity and species composition at two Twin Cays sites, Hidden Creek and Sponge Haven, reflect differences in abiotic factors, ecological interactions, and recruitment history. This report contains the first stages of this project. The Hidden Creek sponge fauna differs from the Sponge Haven fauna largely by deletions. To determine if the cause might be stressful abiotic factors in Hidden Creek, five sponge species common at Sponge Haven, but absent from Hidden Creek, were transplanted to Hidden Creek. After 12 months, all but two transplanted individuals had died (97% mortality), suggesting distribution constraint by episodically unfavorable abiotic factors. To follow recruitment and community development from a start on bare substrata, pipes of pvc, each 25 cm long and 2.2 cm outside diameter, were suspended among prop roots in Hidden Creek. After 20 months, 69 sponge individuals representing 11 species were living on eight pipes. Differences in species composition and relative abundance between pipes and roots underscore the importance of postrecruitment processes in community development.