Reproductive ecology of a deep-water scleractinian coral, Oculina varicosa, from the southeast Florida shelf

The Ivory Tree Coral Oculina varicosa forms extensive reefs of azooxanthellate colonies at depths of 70–100 m along the edge of the Florida Hatteras slope. Healthy reefs support invertebrate and fish communities as diverse as those of tropical coral reefs, and are a critical spawning habitat for a number of commercial fisheries species. A 3-year study of reproduction and larval development revealed that O. varicosa is a gonochoristic broadcast spawning species, with small eggs (<100 μm) and high fecundity values. The gametogenic cycle begins in the early summer and spawning occurs during late summer and fall, with no obvious relationship to lunar or tidal phase. Planulae are small (approximately 160 μm), active swimmers that can withstand a wide range of temperatures and that settle approximately 21 days after spawning. Given the hydrodynamics of the Florida Hatteras shelf, larvae not only have the potential to be transported between the deep reef tracts, but may also contribute to nearshore zooxanthellate populations during summer upwelling events.