Abstract
Framework-forming scleractinian corals form the foundation for the benthic ecosystem, which can be found around the world’s oceans. Their development is characterized by many factors including, (1) currents providing proper food supply, (2) favorable temperatures, and (3) adequate oxygen saturation conditions. Given these requirements are met, these frameworks can form large biogenic reefs, which are biodiversity hotspots seen across the Atlantic Ocean. This study aims to predict and quantify cold-water coral (CWC) distribution and their developmental history in the Straits of Florida from the Late-Pleistocene to the Modern; whether cold-water coral growth is restricted to glacial/interglacial stages, how local geomorphology and current systems influence the distribution of CWCs and the formation of coral mounds, and if cold-water corals are recorders of changes in temperatures of bottom waters over time.
In the Straits of Florida, benthic terrain modeling combined with habitat mapping for two sites provide insights into spatial quantification of facies and CWCs on the seafloor. Corals at the site with antecedent topography reveal a direct relationship to the high relief features and boulders of the surrounding seafloor with a 2% coral cover of the total area with over 30% of all high relief features showing coral presence. Orientations of corals and associated mounds at this site correlate closely with the semi-diurnal current regime. At the site with self-organizing corals, the corals cover over 25% of the total area and are present on more than 95% of all features detected and are oriented into the current regime at a SSE trend. Corals grow preferentially into the current regimes, which affects overall mound morphology over time.
Using cold-water corals as an archive into the past has become a common practice. For the Straits of Florida, corals grow across glacial and interglacial climate cycles including the Last Glacial Maximum (LGM), from MIS 14/15 to the modern except for MIS 10 and MIS 4. This indicates that the current system within the Straits was pronounced enough to deliver all the required food for coral growth. Evidence of differing sedimentary structures of coral mounds reveal the current system’s impacts on their evolution through time. Despite being localized within a single carbonate province, the multitude of current systems within the region have direct impact on the formation of mounds. Weaker currents provide the food for coral proliferation as well as sediment supply for overall mound formation, whereas mounds in higher velocity currents are impacted by slower mound aggradation due to winnowing of fine-sediments and/or non-deposition.
The assessment of CWCs as a proxy for temperature variations in the Straits of Florida yields insights into the advancement of clumped isotope thermometry for biogenic carbonates. Analyzed CWCs do not conform to recent published calibrations for temperature. Combining modern coral samples and literature data enabled a corrected calibration to that previously published, while establishing a likely need for species- dependent calibrations for carbonate precipitating organisms. Combining age-dated corals with temperatures derived from the new calibration reveals a variation of 3°C from glacial periods to interglacial periods within the Straits without having to account for the various factors reflected in other techniques used to derive temperature.
Integrating data and knowledge from the ecological standpoint with that of the geological promotes critical understanding of these fragile ecosystems.