Abstract
Coral reef degradation and loss have been extensively documented worldwide during the last few decades. While much attention has been directed toward the mortality of reef-building corals vis-a-vis various observed disturbances (e.g., bleaching, diseases, overfishing, nutrification), the fate of other reef-associated metazoans, especially invertebrates, has not received sufficient attention. Living and dead corals, reef frameworks, and carbonate sediments provide essential habitat niches for a multitude of symbiotic and cryptic species. Thirty-one animal phyla contain species that inhabit coral reefs with known global species richness estimated at 93,000. Possibly as many as 1,000,000 reef-associated metazoans occur globally. Many of these species are undiscovered because of their cryptic or sibling nature. Metazoan reef associates have important functional roles on reefs, e.g., increasing survivorship of coral hosts, aiding in reef framework construction (calcification, consolidation), providing trophic resources, affecting coral mortality (corallivores) and erosion (bioerosion). Despite widespread bleaching and mortality, no reef-building corals (Scleractinia) have yet to become globally extinct. Three populations of Millepora spp. (Hydroida) were severely impacted in Pacific Panama during the 1982-83 El Nitio Southern Oscillation event. Present status indicates recovery of Millepora intricata Milne-Edwards and Haime, 1860 to shallow reef zones from relatively deep (10-15 m) refugia. Furthermore, two hydrocoral species have suffered regional extinctions in the eastern Pacific with populations still present in the Indo-Pacific (Millepora platyphylla Hemprich and Ehrenberg, 1834) and eastern Indian Ocean (Millepora boschmai de Weerdt and Glynn, 1991). Considering the large numbers of obligate symbionts and other coral reef metazoan associates, there is a strong likelihood of large-scale extinctions following the loss of reef-building corals.
