Data from: 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. 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. No Symbiodinium clade shift was found following the year-long light treatments. We conclude that E. paradivisa, and its original symbiont clade, can adapt to various light conditions by controlling its metabolic rate and growth energy investment, and consequently induce LEC