Reciprocal-transplantation between shallow and mesophotic stony corals.

Most studies to date on the various life-history aspects of scleractinian corals (e.g. reproduction, connectivity, and physiology) have focused on their innate habitats. However, comprehensive data on the ability of both shallow and mesophotic corals to contend in the coming decades with the different environmental conditions they may encounter due to new habitats or environmental changes (e.g. eutrophication), are scarce. Long-term cross-transplantation experiments assessing the potential responses and acclimatization ability of corals are thus needed in order to expand our knowledge. Here we examined the survivorship and changes in the photobiological acclimatization of corals following their cross-transplantation between two different depths (5-10 m and 45 m) and two sites characterized by different abiotic conditions (i.e. light, nutrient, and sedimentation regime). This year-long in-situ experiment was performed on five depth-generalist coral species. Depth of origin and the species' particular morphology were found to be the strongest predictors of survivorship. Physiological responses occurred mainly among those corals that had been translocated from deep-to-shallow water, and were expressed in a significant reduction in chlorophyll-a concentration and algal density, as well as changes in photosynthetic parameters (e.g. minimal/maximal saturating points, E and E, and rETR). Our study contributes to a better assessment of the physiological and ecological consequences of corals under acute and long-term environmental perturbations and their endurance abilities. Furthermore, it contributes to the information necessary for effective management intervention aimed at supporting the possible acclimation or rehabilitation of coral species.