A changing climate for coral reef research

By Line K Bay (AIMS), Juan Ortiz (AIMS), Kate M Quigley (Minderoo Foundation)

“There is no such thing as a special category of science called applied science; there is science and its applications, which are related to one another as the fruit is related to the tree that has borne it.”

Louis Pasteur, Correspondence of Pasteur and Thuillier Concerning Anthrax and Swine Fever Vaccinations

The Reef is under threat

The scale, frequency and severity of marine heatwaves that cause mass coral bleaching are increasingly eroding the reef resilience. Coral adaptation to warming ocean temperatures will be critical to sustain functional assemblages of species into the future. Management and conservation approaches that protect or enhance the resilience and adaptive capacity of structure-building corals, and by extension, the reef biodiversity they support, are therefore urgently needed. Understanding the natural adaptive capacity of reef building corals, and the extent to which it can be enhanced through active restoration interventions, is a priority area of targeted research and development.

A changing climate for coral reef research

We have studied the evolutionary potential of reef building corals on the Great Barrier Reef (GBR) for close to two decades. During this time, we have witnessed a shift in research focus from understanding the underlying biological mechanisms of acclimatisation and adaptation to applying such knowledge to enhance corals’ thermal tolerance, for example in reef restoration. While perceived as disparate by some, the underpinning questions are often the same and advances in both research fields are based on parallel discoveries.

Indeed – funding for research into restoration and adaptation can provide an opportunity to fast-track our fundamental knowledge of coral reefs’ futures required for conventional management and conservation.

Some corals likely harbour the raw material for adaptation

Some coral populations harbour extensive standing genetic variation that may facilitate adaptation to current and future warming and individuals with enhanced tolerance under predicted future conditions currently exist across reef scapes. While restoration and adaptation seek to map these heat tolerant corals to identify sources for restoration activities like selective breeding, this research also provides essential information to support decisions for the spatial protection of sensitive or tolerant populations, management of extractive activities, or active restoration.

The level of adaptation required to avoid regular bleaching depends on species-specific stress thresholds, background rates of warming, and the severity of acute events. To date, bleaching thresholds have been determined from observations and the analysis of samples collected during bleaching events, as well as experimental approaches in the laboratory or the field, like in the staged deployment of heat tolerant corals. However, how much potential for natural adaptation based on underlying genetic diversity and how much this process can be accelerated with assisted evolution is unclear. In this context, a combination of ecological models that incorporate the main mechanism driving reef dynamics and evolutionary models focusing on natural adaptation rates can and should inform on the potential benefits and risks of different intervention strategies and how much adaptation (both naturals and enhanced) may be required to maintain reef resilience.

Above: Quantitative genetics is the study of the inheritance of traits and forms the basis of selective breeding for enhanced tolerance. © ReefSkyPhoto.

“We stand united in our call to decision makers, business, and the broader community to act on climate change now.”

Top of page left : Rapid heat stress assays undertaken in the field are used to determine the distribution and abundance of heat tolerant corals and can be used to develop markers for selective breeding. © James Gilmour Above: Coral spawning event provides an opportunity to study the reproductive biology of corals and apply this knowledge to coral propagation and aquaculture. © ReefSkyPhoto

While the GBR has seen an increase in coral cover over the past few years the long-term threats to this iconic ecosystem from global threats like climate change remain and are predicted to increase. We stand united in our call to decision makers, business, and the broader community to act on climate change now. However, even if carbon emissions are reduced immediately, the legacy of historic emissions will result in significant warming over the coming decades and corals will continue to decline unless tolerance increases rapidly. While many uncertainties remain around restoration and adaptation it is increasingly clear that doing nothing is not a risk-free option either. The scientific community needs to focus on the fundamental knowledge needed for coral reefs and be ready to apply this information in the most appropriate manner to give our reefs the best future we can.

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Above: Natural variation in bleaching tolerance is evident in corals photographed near Lizard Island in March 2021.© Dr Emily Howells