MEPS 217:251-261 (2001)  -  doi:10.3354/meps217251

ABSTRACT: Sedimentation, predation and visible light are cited as causal factors to explain the preferential recruitment of coral larvae to shaded habitats in shallow water. Here I examine the effects of ultraviolet radiation (UVR, 280 to 400 nm) on settlement of Pocillopora damicornis (Linnaeus) larvae, and the role of UV-absorbing compounds, mycosporine-like amino acids (MAAs), in 3 field experiments. Larvae were obtained from adults of 4 origins: shallow (<0.5 m), deep (2 to 3 m), acclimated under UV-transparent (UVT) filters, and under UV-opaque (UVO) filters. Larvae were then exposed to UVT or UVO conditions in specially designed larval settlement chambers placed on the reef at 0.5 m depth. UVR had a negative effect on total settlement. However, UVR did not significantly increase mortality. High performance liquid chromatography analyses revealed significantly higher concentrations of MAAs in adults incubated in UVT conditions compared to those in UVO, and in shallow larvae compared to deep larvae. Despite the differences in MAA concentrations, larval origin did not significantly affect survival or settlement. Lack of an Œorigin¹ effect suggests that either MAAs may not be important to the larval ecology of this species, or that the deep and UVO larvae had at least the minimum amount of MAAs required for UVR protection. Regardless of MAAs, these experiments indicate that larvae may delay settling to the substrate when UVR levels are high (behavioral response), or that UVR is inhibiting the settlement process in some way (physiological response).

KEY WORDS:\fMycosporine-like amino acids Coral recruitment UV radiation Coral planulae