Priming for Survival: Does temperature variability increase the physiological preparation of reef-building corals to a severe marine heatwave?

Coral reefs are facing alarming declines, with the most extreme marine heatwave in recorded history occurring across the southern Great Barrier Reef (GBR) this year. Encouragingly, there is evidence that exposure to high diel temperature variability can ‘prime’ corals to withstand heat stress by promoting rapid physiological acclimatization. Yet, the last heatwave to occur at this location saw three times greater coral mortality within thermally variable habitats, leaving many questions on whether life-long acclimatization to temperature variability can protect corals during extreme heatwaves. Here, we characterize host physiological performance and microbial community composition of the reef-building coral Pocillopora damicornis across six sites varying in diel temperature fluctuations (2.4–7.7°C day-1) and three timepoints: (i) pre- (Sept. 2022), (ii) during (May 2024), and (iii) post- heat stress (Sept. 2024). Pre-heatwave, P. damicornis from intermediate temperature variability demonstrated the greatest host biomass and symbiont densities, suggesting that there may be an optimal priming exposure to promote resilience. Analyses of host and symbiont genetics, tissue energetics, symbiont physiology, and microbiome patterns are ongoing, and we hypothesize that during and post-heatwave microbial communities will ‘shift’ from pre-heatwave communities. Ultimately, this research aims to clarify the complex relationships between coral microbiomes and host physiology to help guide strategies to safeguard these crucial ecosystems amid ongoing climate challenges.

Presentation Preference: Oral

Primary Presenter: Marcelina Martynek, University of Pennsylvania (martynek@upenn.edu)

Authors:

Marcelina Martynek, University of Pennsylvania  (martynek@sas.upenn.edu)

Kristen Brown, University of Pennsylvania  (ktbrown@sas.upenn.edu)

Katie Barott, University of Pennsylvania  (kbarott@sas.upenn.edu)