MEPS 455:65-77 (2012)  -  DOI:

Efficient light harvesting in deep-water zooxanthellate corals

Samuel E. Kahng1,*, Eric J. Hochberg2, Amy Apprill3, Daniel Wagner4, Daniel G. Luck1, Denise Perez5, Robert R. Bidigare6

1Hawai‘i Pacific University, 41-202 Kalaniana‘ole Highway, Waimanalo, Hawai‘i 96795, USA
2Bermuda Institute of Ocean Sciences, 17 Biological Station, St. George’s GE 01, Bermuda
3Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole Massachusetts 02543-1050, USA
4Papahānaumokuākea Marine National Monument, 6600 Kalaniana‘ole Highway, Suite 300, Honolulu, Hawai‘i 96825, USA
5National Coral Reef Institute, Nova Southeastern University, 8000 North Ocean Drive, Dania Beach, Florida 33004-7796, USA
6University of Hawai‘i at Mānoa, 1000 Pope Road, Honolulu, Hawai‘i 96822, USA

ABSTRACT: The vertical zonation of dominant megabenthic, photosynthetic taxa suggests that differential photosynthetic capabilities enable specialized, low-light zooxanthellate corals to dominate at depths where shallow-water corals become light limited. This study examines the eco-physiology of deep-water (68−113 m) Leptoseris spp. and shallow-water (2−15 m) Porites spp. zooxanthellate corals from Hawai‘i by comparing spectral absorbance properties and photosynthetic pigment concentrations to the available light spectra in their respective environments. Photosynthetically active radiation reaching Leptoseris spp. was 3 to 11% of surface irradiance compared to 41 to 90% reaching Porites spp. Optical measurements indicated that Leptoseris spp. exhibited lower reflectance (i.e. higher absorptance) compared to Porites spp. and were chromatically adapted to the wavelengths of photons available at depth. Despite the decreased spectral reflectance, deep-water Leptoseris spp. exhibited significantly lower areal photosynthetic pigment concentrations than did shallow-water Porites spp. Based on morphological comparisons of the skeletons of both coral genera, we hypothesize that Leptoseris spp. skeletons may cause incident light to travel through the coral tissue several times, thereby increasing photon-pigment interactions without increasing pigment concentrations. This superior light harvesting efficiency exhibited by Leptoseris in an energy limited environment (enabled by skeletal design rather than pigment physiology) may in part explain why the dominant genus of reef-building corals in Hawai‘i cannot compete successfully with specialized low-light corals at extreme depths.

KEY WORDS: Photobiology · Mesophotic · Coral ecology · Ecophysiology · Leptoseris

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Cite this article as: Kahng SE, Hochberg EJ, Apprill A, Wagner D, Luck DG, Perez D, Bidigare RR (2012) Efficient light harvesting in deep-water zooxanthellate corals. Mar Ecol Prog Ser 455:65-77.

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