Award: OCE-1923743

This project investigated how environmental conditions influence the resilience of reef-building corals to climate change stressors. To do so, researchers examined the stress responses of corals living in naturally extreme habitats from Hawaii to Australia. This project revealed that coral skeletal growth was affected by daily pH fluctuations, and corals from habitats with more variable daily seawater pH conditions showed enhanced resilience to acidification stress. However, daily temperature variation had complex influences on coral heat stress tolerance and coral bleaching susceptibility. Extreme daily temperature variability led to declines in heat tolerance, while intermediate levels of variability promoted heat tolerance above that for corals in relatively stable thermal environments. This project also found that marine heatwaves lead to declines in coral metabolic rates and caused dysfunctional regulation of intracellular pH in corals, surprisingly including those that did not bleach. In addition, repetitive exposure of individual coral colonies to marine heatwaves has led to a continued loss of individuals from some coral species even without bleaching, while other species appear to be gaining resilience against heat stress following repeat exposure. Coral reproduction was also found to be sensitive to pH, as coral sperm required elevation of their intracellular pH (alkalinization) to activate motility, indicating that ocean acidification may have a significant negative impact on coral sperm function and thus corals ability to sexually reproduce. In addition, as this project found that heat stress can lead to declines (acidification) in intracellular pH, the combination of heat and seawater acidification stress resulting from climate change may have a profoundly harmful impact on the ability of coral sperm to swim to and fertilize eggs. Overall, this project supported the training of 2 postdoctoral researchers, 3 doctoral students, 1 postgraduate technician, and 8 undergraduates, and resulted in 13 peer-reviewed publications, 37 publicly available datasets, and over 20 scientific conference presentations. In addition, this project led to the development and implementation of hands-on educational activities for inner-city public high school students covering coral reef ecology and the effects of climate change on marine organisms in partnership with the Center for Aquatic Sciences in Camden, NJ. In addition, this project mentored and trained 8 Philadelphia public high school students who conducted research projects in coral reef ecology and climate change. Results of this project were also presented at over 23 outreach events for students and the general public. Last Modified: 06/06/2024 Submitted by: KatieLBarott