UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Sessile invertebrates are important for their contributions to community assemblages in terms of their competitive and trophic interactions. Colonial invertebrates make excellent model organisms for the study of ecological processes. Bryozoans, modular colonial filter feeders, are important competitors in a range of habitats and represent a potentially significant source of diversity. Little work has been done to catalog the Bryozoa of Mo’orea, French Polynesia. By examining coral rubble, artificial substrates and Turbinaria spp. algal fronds, I quantified the distribution of bryozoans in a shallow lagoon and simultaneously recorded their competitive interactions. I also quantified patterns of bryozoan richness and abundance with respect to depth and location. Finally, I conducted an experiment to determine the degree to which predation effects an abundant genus, Rhynchozoon spp. I found more bryozoans further from the barrier reef and in deeper water. There were vastly more cheilostomates than either cyclostomates or ctenostomates, though it remains unclear whether they are competitively dominant. A few genera dominated the epibiotic algal habitat, showing abundance patterns opposite those seen on coral rubble. I did not find any successional patterns on algae. I did not find a significant effect of predation on uncaged Rhynchozoon spp. colonies in the field. This study suggests that abiotic factors may be more important than trophic and competitive interactions in determining bryozoan abundance, but their relative influences remain unclear. This work lays the foundation for future ecological work on factors limiting bryozoans in French Polynesia and provides a guide to the genera found in this study.