A review of the current knowledge of the flow of carbon and energy in scleractinian corals

The precipitous decline in global coral cover over the past several decades necessitates a comprehensive understanding of the energetic underpinnings and fundamental biology governing coral growth, reproduction, and acclimation. Quantifying the flow of energy in corals is a critical component of the knowledge needed to predict, manage, and mitigate the coming future for these sentinel species in an era of rapid global change. In this review, we synthesize nearly 100 yr of the literature on carbon budgets, which are closely linked to coral energetics. To this end, this review is organized into energetic gains and losses, with a focus on detailed mechanistic processes, their historical foundations, and our current understanding. We highlight how the level of energetic reserves and trophic flexibility governs the fate of scleractinian corals, particularly following a bleaching event. We also observe a high degree of species specificity in energy acquisition, storage, and use, specifically in the ability to leverage heterotrophy to buffer energy loss during bleaching. We note that current energetic research has prioritized only ~ 20 species out of at least 1,500 known scleractinians and is focused on taxa with wide ranging geography. Finally, we identify research priorities for addressing the precipitous loss of coral cover in the “Anthropocene.” Key research avenues include (1) taking a species-driven approach to quantify the contribution of autotrophy and heterotrophy to energy and carbon acquisition, (2) assessing trophic flexibility under environmental stress, and (3) generating robust models to explain and predict energetic status. Broadening the scope of studied scleractinians to include corals at range edges, endemics, and understudied taxa with alternative mechanisms for energy utilization, will be key to understanding the flow of energy in corals now and in the coming future.