KEYNOTE: Geological perspectives on the degradation and restoration of Florida’s coral reefs

HCAS Guy Harvey Oceanographic Center, Nova Southeastern University

The growth and maintenance of the complex coral-reef structures built over 100s to 1000s of years serve as the foundation for the myriad ecosystem services reefs provide to society. Understanding how climate and other anthropogenic disturbances will influence reef-building in the future is critical; however, accurately forecasting the long-term process of reef accretion is generally not possible with short-term ecological studies. Geological records, particularly those from sensitive, marginal reef environments such as the subtropical reef system of south Florida, are key to projecting how the processes of reef-framework construction and destruction will change in the future. Millennial-scale reconstructions from throughout the ~500 km extent of the Florida reef tract suggest that climate has been a primary control of reef development for at least the last 10,000 years. Whereas reefs grew rapidly and expanded their latitudinal limits during the relatively warm climate 10,000 to 8,000 years ago, as the climate cooled and winter cold fronts became more common reef development declined. By 3,000 years ago, reef-building was negligible throughout the region, marking the collapse of the reefs’ geological function. Over the last 50 years, anthropogenic disturbances have also threatened the ecological functions of Florida’s reefs by driving unprecedented loss of reef-building corals. These changes have unbalanced Florida’s carbonate budgets, leading to decadal-scale declines in reef-accretion potential and increases in reef erosion. Although trajectory of reef degradation has dire consequences for future dependence on reef structure and function in the future, there is still hope: in some locations coral restoration may still have the potential to reverse long-term declines in reef building.