Title: Glowing corals in a changing ocean
Warming ocean temperatures and local stressors are threatening the survival of coral reef ecosystems and the vital resources they provide to the human population. In light of the global reef crisis, understanding how corals have adapted to their environment and how they respond to changing conditions is paramount to guide management efforts. Green Fluorescent Protein (GFP)-like pigments produced by the coral host are sensitive to environmental conditions and can be monitored non-invasively, making them a valuable tool to investigate coral physiological response to change. Using optical and molecular methods, we studied the regulation of GFP-like proteins in corals from light-limited mesophotic reefs and from high-light shallow water reefs. We described two separate mechanisms through which GFP-like proteins are regulated to optimise the internal light environment of coral colonies, with benefit for the coral-algae symbiosis. Our findings indicate an important role of host pigments in the adaptation and acclimatisation of the coral holobiont to a wide range of conditions, and highlight a potential application of GFP-like proteins as biomarkers of coral physiology.