Photoacclimation and induction of light-enhanced calcification in the mesophotic coral Euphyllia paradivisa

Gal Eyal, Itay Cohen, Lee Eyal-Shaham, Or Ben-Zvi, Yaron Tikochinski, Yossi Loya

Research output: Contribution to journalArticlepeer-review

Abstract

Corals and their photosymbionts experience inherent changes in light along depth gradients, leading them to have evolved several well-investigated photoacclimation strategies. As coral calcification is influenced by light (a process described as LEC-'light-enhanced calcification'), studies have sought to determine the link between photosynthesis and calcification, but many puzzling aspects still persist. Here, we examine the physiology of Euphyllia paradivisa, a coral species found at a wide range of depths but that is strictly mesophotic in the Red Sea; and also examines the coupling between photosynthesis and LEC by investigating the response of the coral under several controlled light regimes during a long-term experiment. E. paradivisa specimens were collected from 40 to 50 m depth and incubated under three light conditions for a period of 1 year: full-spectrum shallow-water light (approx. 3 m, e.g. shallow-light treatment); blue deep-water light (approx. 40 m, e.g. mesophotic-light treatment) or total darkness (e.g. dark treatment). Net photosynthesis remained similar in the shallow-light-treated corals compared to the mesophotic-light-treated corals, under both low and high light. However, calcification increased dramatically with increasing light intensity in the shallow-light-treated corals, suggesting a decoupling between these processes. Photoacclimation to shallow-water conditions was indicated by enhanced respiration, a higher density of zooxanthellae per polyp and lower chlorophyll a content per cell. The dark-treated corals became completely bleached but did not lower their metabolism below that of the mesophotic-light-treated corals.

Original languageEnglish
Article number180527
JournalRoyal Society Open Science
Volume6
Issue number2
DOIs
StatePublished - 1 Feb 2019

Keywords

  • Coral reefs
  • Light-enhanced calcification
  • Mesophotic coral ecosystems
  • Photosynthesis
  • Red Sea
  • Twilight zone

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