Late Holocene "Turn-Off" of Coral Reef Growth in the Northern Red Sea and Implications for a Sea-Level Fall.

Coral reefs, known for their remarkable diversity, serve a pivotal function in modulating the global oceanic carbon cycle and act as natural barriers that protect coastlines from erosion and storm surges by dissipating wave energy. Despite their importance, their sensitivity to temperature fluctuations, sea-level shifts and anthropogenic changes in the future is highly unknown. In this study, we create a comprehensive documentation of coral growth, sedimentology and ecology spanning the middle to late Holocene in the Gulf of Eilat/Aqaba, northern Red Sea. We then integrate these findings with a reconstruction of the area's environmental conditions over time. The findings reveal a noticeable hiatus of reef growth between 4400 and 1000 years BP (Before Present; "present" being defined as 1950), aligning well with comparable observations made across various locations in the Southern Hemisphere. The coral diversity and abundance along the cores display surprisingly similar patterns before and after the hiatus. This implies that the distinctive coral community thriving during the initial growth phase reappeared nearly 4000 years later, presumably sourced from the deeper reefs. The results are evaluated in the context of a potential sea-level drop and the resilience of coral communities to perturbations of this magnitude. We conclude that the hiatus at this site is due to a combination of factors, including tectonic activity and glacio-eustatic sea-level changes. Our research highlights the critical importance of understanding and managing coral reef ecosystems' responses to sea-level fluctuations to mitigate future impacts on these vulnerable environments.