The absolute and relative composition of Holocene reef cores collected between 1976 and 2017 from the Florida Keys reef tract

Quantifying Holocene Reef Composition: USGS researchers analyzed the composition of 61 cores through digital analysis of high-resolution, photographic core logs (provided in Toth and others, 2018) by identifying 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; however, some corals were combined into broader taxonomic groups. Agaricia, Madracis, Oculina, 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 229 recovered intervals OF the 61 cores. The individual depth intervals were defined based on core penetration depths indicated in the core boxes by the researchers who collected the cores (see Toth and others, 2018). For each interval in each core, the absolute and relative percent composition of all coral taxa were calculated. To calculate absolute percent recovery and composition, a theoretical surface area for each interval was first calculated by multiplying the penetration length of the interval (for example, 1.5 meters or 5 feet) by the average diameter of the core measured in CPCe, which varied between ~3 and 5 centimeters depending on the specific equipment used to collect the core. Absolute percent composition was then calculated by dividing the total measured area of each coral taxa (or other recovered material) in an interval by the theoretical, projected surface area of that interval. Relative percent composition of coral taxa was calculated as a percentage of total coral recovery by dividing the area represented by each individual coral taxa in an interval by the total area of all coral taxa in that interval.

Age and Paleodepth Calculations: Intervals with no recovery, intervals containing only unconsolidated sediments, or intervals that only contained other non-coral material were not included in further analyses. In order to provide a paleoecological context for Holocene composition data, the mean age and paleodepth for each of the remaining 59 intervals in the cores was calculated. The ages of the boundaries of each depth interval in the cores was estimated by linear interpolation of the 203 radiometric ages for the 59 cores, which are provided in Toth and others (2018). The estimated ages of the beginning and end of the interval were then averaged to determine the mean age of that interval. Cores that did not have at least two ages (the minimum needed to generate age models) were not included. The average paleodepth for each interval was determined using the reconstruction of Holocene sea-level variability in south Florida developed by Khan and others (2017). First, Khan and others' (2017) model outputs were used to estimate the position of sea-level relative to modern mean sea level (MSL) at the beginning and end of each depth interval in the cores based on the estimated ages of those points. Depths of intervals in the core were converted to MSL by adding the water depth at the coring location (see Toth and others, 2018). Mean paleodepths were then calculated for each interval by averaging the paleodepths at the beginning and end of each interval.

Added keywords section with USGS persistent identifier as theme keyword.