Effects of Ultraviolet Radiation on the Biology of Caribbean Reef Corals

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Recent studies indicate that ultraviolet radiation can penetrate to considerable depths on tropical reefs. Persistent high levels of UV penetration, resulting from extended periods of calm sea conditions, have been shown to induce stress leading to the loss of symbiotic zooxanthellae (i.e., bleaching) in reef-building corals. These conditions may have contributed significantly to the regional mass coral bleaching events observed in the Caribbean during 1987 and 1990. This project will continue monitoring penetration of UV radiation, sea temperatures, and recovery of coral exposed to UV radiation. In addition, the project will be expanded to evaluate the effects of UV radiation on the early life-history stages, namely planula larvae and newly-recruited juveniles, of predominant coral species. While increases in UV radiation are predicted to be minimal at low latitudes, increased frequency of calm sea conditions predicted by global warming will lead to enhanced water column clarity and high UV penetration with subsequent negative effects on reef corals. This project, by experimentally defining the maximum UV intensities that can be tolerated by larval and juveniles corals, will provide insight into the role that current intensities of UV radiation play in limiting recruitment and shaping subsequent coral community structure.