Reef Structure of the Florida Reef Tract 2005-2020

Shallow-water coral reefs of the Florida Reef Tract comprise the third largest reef in the world, but during the last several decades scleractinian (stony) corals have suffered unprecedented declines from global and local stressors. A program to evaluate the effects of high-temperature bleaching events was initiated by The Nature Conservancy’s Florida Reef Resilience Program in 2005 and surveys have been completed across at least some portion of the entire region every year since. The program adopted a demographic (colony-based) assessment approach, which records colony species, size (height and maximum diameter) and estimated partial mortality (percent barren skeleton). Because reef structure is critical to ecosystem functioning and services, data from 2005–2020 were analyzed to describe the abundance, size and morphological complexity of stony coral colonies forming the biogenic reef. Colony height, footprint, surface area and volume summed for each of 6,016 transects were used to describe reef structure and averages were used to characterize the components that contributed to the structure. Nearly 150,000 colonies representing 49 species were reported during this period and results demonstrated both spatial and temporal changes for the region and for geographic subregions. Some subregions showed increasing colony density, especially for three small, hemispheric species, and declining average colony size. Colony dimensions allowed quantitative estimation of some ecosystem goods and services, such as fish habitat and carbon storage.