Abstract
Anthropogenic climate change has contributed to the accelerating loss of coral reefs worldwide. This crisis has led to a myriad of studies aimed at understanding the basis of coral resilience to support reef conservation. Here, we compare physiological, proteomic, and metabolomic responses to acute thermal stress to identify both diverged and conserved stress response strategies and molecular markers of bleaching susceptibility in three different coral species. We find species-specific responses with the thermally sensitive Acropora hyacinthus exhibiting a rapid decline in endosymbiont physiology (~19% decline in photosynthetic efficiency and a -1.88 fold change in abundance), coupled with one-third of proteins showing a reduction in abundance. In contrast, Porites lobata displayed a delayed physiological and proteomic (~5% initial; ~14% prolonged) response to stress, suggesting greater resilience. Stylophora pistillata initially showed shifts in the proteome (~11%) followed by colony "bail-out", that is, rapid tissue loss. Overall, we observed markedly different responses in most biochemical pathways in the three coral species. Nonetheless, some known biomarkers of stress, including heat-shock proteins, showed conserved, cross-species responses to thermal stress with differences in temporal abundance reflecting bleaching resistance. Metabolomic profiling revealed an increase in stress-associated dipeptides and free amino acids in all three species, although species-specific and temporally variable responses occurred. Our results underscore the species-specific nature of coral responses to thermal stress and highlight proteomic signatures associated with symbiosis breakdown, offering mechanistic insights into coral bleaching susceptibility and resilience. Overall, these findings enhance our ability to identify early-warning indicators of bleaching and underscore the challenges associated with the development of universal coral stress biomarkers.