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

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 light-enhanced calcification by investigating the response of the coral under several controlled light regimes during a long-term experiment. E. paradivisa specimens were collected from 40-50 m depth and incubated under three light conditions for a period of one year: full-spectrum shallow-water light (~3 m, e.g. shallow-light treatment); blue deep-water light (~40 m, e.g. mesopho...