The Relative Composition of Late Pleistocene Coral Reefs in the Florida Keys

Quantifying MIS5c-a Coral Reef Composition: Following the methods described in Toth and Stathakopoulos (2019), USGS researchers analyzed the composition of the Late Pleistocene (~116 to ~74 thousand years before present; Marine Isotope Stage 5d-a) of 31 reef cores through digital analysis of high-resolution, photographic core logs (provided in Toth and others, 2018). The late Pleistocene age of the intervals was confirmed through radiometric dating by Hsia and others (2024a,b) as described in Toth and others (2025). USGS researchers (Toth and Stathakopoulos) identified all visible material in the core photographs including corals, unconsolidated sediments, and consolidated carbonate reef rock, using the physical core records for reference. All coral taxa were identified to the species level whenever possible, using the Corals of the World taxonomic list as reference (https://www.coralsoftheworld.org). However, some corals were combined into broader taxonomic groups. Agaricia and Millepora spp., which were all rare in these records, were only identified to the genus level. Porites astreoides was always identified to the species level, but the other western Atlantic Porites spp.—P. porites, P. divaricata, and P. furcata—were grouped as “branching Porites spp.”. Orbicella annularis, O. faveolata, and O. franksi were all classified as “Orbicella spp.” because of difficulty in distinguishing fine-scale differences in the morphology of this group. Corals that were too taphonomically degraded or too small to be confidently identified to even the genus level were categorized as “unidentified coral species”. USGS researchers quantified the abundance of each coral taxon as well as unconsolidated sediment and carbonate reef rock by using the Area Analysis Tool in the program Coral Point Count (CPCe; Kohler and Gill, 2006) to digitally trace the projected surface area of all material in the core photographs. These data were used to calculate the percent composition of all core constituents within 66 recovered intervals of the 31 cores. The individual depth intervals were defined based on core penetration depths indicated in the core boxes by the researchers who collected the cores (Toth and others, 2018). For each interval, the relative percent composition of all coral taxa were calculated by dividing the area represented by each individual coral taxa in an interval by the total area of all coral taxa in that interval. Total (absolute) percentage recovery within each interval was also estimated by dividing the total measured areas of an interval by a theoretical interval area, calculated as the product of its recorded length and digital measurements of its projected width as described in Toth and Stathakopoulos (2019) and Toth and others (2019).

Quantifying Composition of the MIS5e Coral Reef at Windley Key: These data were originally collected from quarried areas of the subaerially exposed Key Largo Limestone at Windley Key Fossil Reef Geological Park (24.9492, -80.5961) by Weinstein. Briefly, compositional features of the Key Largo Limestone were identified along seven, 10-meter (m) transects placed parallel to the ground at randomly selected heights (0.6–1.7 m) along exposed walls of the quarry. The length of each textural feature along each transect, including corals, was recorded. However, in the original study, corals were only identified to the genus level. USGS researchers (Toth and Stathakopoulos) used photographs taken during the surveys to verify and refine the coral species identifications (using Corals of the World for reference). This data release provides the relative percent composition of all coral taxa and total non-coral carbonates identified on the transects.