All reef-forming corals depend on the photosynthesis performed by their algal symbiont, and such corals are therefore restricted to the photic zone. The intensity of light in this zone declines over several orders of magnitude—from high and damaging levels at the surface to extreme shade conditions at the lower limit1. The ability of corals to tolerate this range implies effective mechanisms for light acclimation and adaptation2. Here we show that the fluorescent pigments3,4,5,6,7,8,9 (FPs) of corals provide a photobiological system for regulating the light environment of coral host tissue. Previous studies have suggested that under low light, FPs may enhance light availability4,5. We now report that in excessive sunlight FPs are photoprotective; they achieve this by dissipating excess energy at wavelengths of low photosynthetic activity, as well as by reflecting of visible and infrared light by FP-containing chromatophores. We also show that FPs enhance the resistance to mass bleaching of corals during periods of heat stress, which has implications for the effect of environmental stress on the diversity of reef-building corals, such as enhanced survival of a broad range of corals allowing maintenance of habitat diversity.
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We thank the Great Barrier Reef Marine Park Authority, especially J. Oliver, R. Berkelmans, M. Russell and U. Engelhart, for financial and logistic support. This work was also supported by an Australian Research Council (ARC) SPIRT PhD award (A.S.) and ARC grants (O. H.-G. and A.L.). M.K. was supported by the Danish Natural Science Research Council. We thank the staff of Heron and One Tree Island research stations for assistance during fieldwork.
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Salih, A., Larkum, A., Cox, G. et al. Fluorescent pigments in corals are photoprotective. Nature 408, 850–853 (2000). https://doi.org/10.1038/35048564
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