Thermal Tolerance Across Depth-Segregated Orbicella Corals
Location
HCAS Guy Harvey Oceanographic Center, Nova Southeastern University
Start
2-14-2025 9:00 AM
End
2-14-2025 9:15 AM
Type of Presentation
Oral Presentation
Abstract
Coral bleaching (loss of symbiotic algae) has decimated coral reefs globally due to rising seawater temperatures. However, some corals continue to thrive under conditions that are lethal to others, potentially due to unrecognized genotypes with varying physiological thresholds. This study examines the thermal tolerance of two coral species, Orbicella faveolata and Orbicella franksi, which inhabit different depths at Media Luna Reef, Puerto Rico. We investigated their survivorship following reciprocal transplant experiments across opposite depths (5 vs 20 m) and assessed their physiological responses to acute thermal stress using the Coral Bleaching Automated Stress System (CBASS). We employed low-coverage whole-genome sequencing (lcWGS) to characterize coral genomic variation and analyzed their photosymbiotic algal communities through ITS2 genotyping. Additionally, we studied their photo-physiology by examining photosynthesis versus irradiance (PE) curves and measuring protein, chlorophyll a, and Symbiodiniaceae density. Environmental assessments revealed significant differences in light conditions, but not in temperature or oxygen levels across depths, which influenced coral photo-physiology. Our results indicate that O. faveolata and O. franksi have diverged both genetically and physiologically over a narrow depth and light gradient. These differences are evident in their associations and densities of Symbiodiniaceae communities, respiration rates, and responses to acute thermal stress, with O. franksi demonstrating greater thermal tolerance. These findings provide valuable insights into the selective pressures shaping the evolutionary trajectories of these closely related taxa and their potential resilience to global warming.
Thermal Tolerance Across Depth-Segregated Orbicella Corals
HCAS Guy Harvey Oceanographic Center, Nova Southeastern University
Coral bleaching (loss of symbiotic algae) has decimated coral reefs globally due to rising seawater temperatures. However, some corals continue to thrive under conditions that are lethal to others, potentially due to unrecognized genotypes with varying physiological thresholds. This study examines the thermal tolerance of two coral species, Orbicella faveolata and Orbicella franksi, which inhabit different depths at Media Luna Reef, Puerto Rico. We investigated their survivorship following reciprocal transplant experiments across opposite depths (5 vs 20 m) and assessed their physiological responses to acute thermal stress using the Coral Bleaching Automated Stress System (CBASS). We employed low-coverage whole-genome sequencing (lcWGS) to characterize coral genomic variation and analyzed their photosymbiotic algal communities through ITS2 genotyping. Additionally, we studied their photo-physiology by examining photosynthesis versus irradiance (PE) curves and measuring protein, chlorophyll a, and Symbiodiniaceae density. Environmental assessments revealed significant differences in light conditions, but not in temperature or oxygen levels across depths, which influenced coral photo-physiology. Our results indicate that O. faveolata and O. franksi have diverged both genetically and physiologically over a narrow depth and light gradient. These differences are evident in their associations and densities of Symbiodiniaceae communities, respiration rates, and responses to acute thermal stress, with O. franksi demonstrating greater thermal tolerance. These findings provide valuable insights into the selective pressures shaping the evolutionary trajectories of these closely related taxa and their potential resilience to global warming.