Project: RAPID: Does life-long acclimatization to temperature variability promote coral climate resilience?

Coral reefs are in serious danger, with relentless ocean warming currently considered the greatest threat to reef survival. Sustained temperatures just 1°C above a coral’s typical summer maximum can lead to coral bleaching – the breakdown of symbiosis between the coral and its endosymbiotic algal partner. Coral bleaching can often lead to coral death, and marine heatwaves causing mass coral bleaching have increased from a single mild event in the last century to as many as five per decade in modern times. Remarkably, thermally variable habitats provide a glimmer of hope that heatwave-resilient coral populations may exist, as exposure to high daily temperature variability can ‘prime’ reef-building corals to better withstand heat stress. This project will investigate the effects of the most extreme marine heatwave to occur on the southern Great Barrier Reef to understand whether the elevated coral bleaching thresholds due to priming equate to coral community resilience against bleaching during a heatwave. This data will enhance our understanding of how priming influences coral responses to heat stress, the ecological relevance of current priming benefits in a warming ocean, and the physiological properties of corals that may promote heat tolerance. Broader impacts of this project include research support and training for several early career scientists as well as informing local, regional, and global action from stakeholders to make more educated conservation and management decisions, particularly surrounding ecosystem intervention and restoration. For the 500 million people who rely on coral reefs for food, tourism, and coastal protection, a better understanding of how diverse coral communities develop thermal tolerance and withstand the increasing threat of marine heatwaves will allow us to more effectively conserve and manage coral reef ecosystems in the Anthropocene.

It has become increasingly important to identify heat-tolerant coral populations capable of surviving intensifying marine heatwaves. This project will carry out an urgent assessment of whether life-long exposure to daily fluctuations in temperature that regularly expose corals to extreme temperatures improve the ability of corals to cope with the additional heat stress associated with severe marine heatwaves. The objectives of this research are to uncover the priming exposure (e.g., magnitude of diel thermal variability) most beneficial for bleaching resistance and survival, and determine the physiological properties that promote this resilience across biological scales. Specifically, this project will: (i) compare coral community bleaching resilience (i.e. prevalence and severity) during this heatwave with a decade of seawater temperature, coral demography, species composition, and benthic cover data, and (ii) compare the gene expression and physiology of three genera of corals (Acropora, Pocillopora, and Porites) across six sites with different maximum diel temperature fluctuations (2.4–7.7°C day-1). This research will inform local, regional, and global action from stakeholders to make more educated conservation and management decisions, particularly surrounding ecosystem intervention (e.g., assisted gene flow), restoration (e.g., outplanting thermally-tolerant corals), and conservation (e.g., protection of heat tolerant populations). For the millions of people who rely on coral reefs for food, tourism, and coastal protection, a better understanding of how diverse coral communities develop heat tolerance will better enable us to effectively conserve and manage coral reef ecosystems during the extreme heatwaves accompanying our changing climate. In addition, this project will support the training of early career researchers who are underrepresented in marine science, including undergraduate, graduate and postgraduate scientists.