Journal
JOURNAL OF EXPERIMENTAL BIOLOGY
Volume 213, Issue 23, Pages 4084-4091Publisher
COMPANY BIOLOGISTS LTD
DOI: 10.1242/jeb.039891
Keywords
photoadaptation; transplantation; chromatic adaptation; coral; absorption spectra
Categories
Funding
- Batsheva de Rothschild Foundation
- Bar Ilan University
- Moshe Shilo Center for Marine Biogeochemistry
- Nato SfP Foundation
- Interuniversity Institute
- Australian Research Council
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Depth zonation on coral reefs is largely driven by the amount of downwelling, photosynthetically active radiation (PAR) that is absorbed by the symbiotic algae (zooxanthellae) of corals. The minimum light requirements of zooxanthellae are related to both the total intensity of downwelling PAR and the spectral quality of the light. Here we used Stylophora pistillata colonies collected from shallow (3 m) and deep (40 m) water; colonies were placed in a respirometer under both ambient PAR irradiance and a filter that only transmits blue light. We found that the colonies exhibited a clear difference in their photosynthetic rates when illuminated under PAR and filtered blue light, with higher photosynthetic performance when deep colonies were exposed to blue light compared with full-spectrum PAR for the same light intensity and duration. By contrast, colonies from shallow water showed the opposite trend, with higher photosynthetic performances under full-spectrum PAR than under filtered blue light. These findings are supported by the absorption spectra of corals, with deeper colonies absorbing higher energy wavelengths than the shallow colonies, with different spectral signatures. Our results indicate that S. pistillata colonies are chromatically adapted to their surrounding light environment, with photoacclimation probably occurring via an increase in photosynthetic pigments rather than algal density. The spectral properties of the downwelling light are clearly a crucial component of photoacclimation that should be considered in future transplantation and photoacclimation studies.
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