Paleoecology indicates wave climate as key factor in coral reef development

Abstract. The Last Interglacial (~125,000 years ago) experienced global temperatures warmer than today, making it a natural analog for future climate scenarios. Contemporary coral reefs preserve ecological signals that offer valuable insights into past climate dynamics. Here, we examine the fossil reefs of Aruba, Bonaire, and Curaçao to reconstruct wind and wave conditions during this period. While modern reefs across all three islands are confined predominantly to leeward coasts, paleo reefs flourished on both windward and leeward coasts during the Last Interglacial – raising questions as to what mechanisms underlie the spatial asymmetry in reef development through time. Using quantitative analyses of hard coral cover and changes in coral community composition across the Last Interglacial, we document a transition from a well-developed reef dominated by large colonies of Orbicella spp. and Acropora palmata to a less structurally complex system characterized by smaller Orbicella spp. and Diploria spp. colonies, mirroring a ~20 % reduction in hard coral cover by the end of the Last Interglacial. Despite this decline, coral cover remained substantial and did not resemble the Sargassum-dominated nearshore environment observed today. Atmospheric circulation and hydrodynamic models indicate that substantially weaker easterly trade winds and reduced significant wave height at 127 ka initiated robust reef development, which still persisted despite a dramatic increase in wave energy at 124 ka. By highlighting how variations in wave and wind regimes have shaped coral reef growth and resilience in the past, these findings underscore the value of integrating paleoecology and hydrodynamics to advance our understanding of reef stability under future climate change.