Photophysiology of a mesophotic coral 3 years after transplantation to a shallow environment

With shallow coral reefs suffering from an ongoing rapid decline in many regions of the world, the interest in studies on mesophotic coral ecosystems (30–150 m) is growing rapidly. While most photoacclimation responses in corals were documented within the upper 30 m of reefs, in the present study we transplanted fragments of a strictly mesophotic species from the Red Sea, Euphyllia paradivisa, from 50 m to 5 m for a period of 3 years. Following the retrieval of the corals, their physiological and photosynthetic properties of the corals were tested. The transplanted corals presented evidence of photosynthetic acclimation to the shallow habitat, lower sensitivity to photoinhibition, and a high survival percentage, while also demonstrating a reduced ability to utilize low light compared to their mesophotic counterparts. This long-term successful transplantation from a mesophotic depth to a shallow habitat has provided us with insights regarding the ability of mesophotic corals and their symbionts to survive and withstand shallow environments, dominated by a completely different light regime. The extensive characterization of the photobiology of E. paradivisa, and its photoacclimation response to a high-light environment also demonstrates the plasticity of corals and point out to mechanisms different than those reported previously in shallower corals.