Can Corals Adapt to Climate Change?
Global Genetic Study Offers Fresh Insight into Coral Survival in a Warming Ocean
As climate change drives increasingly intense and frequent marine heatwaves, many reef-building corals are being pushed beyond their thermal limits, triggering mass coral bleaching and reef degradation. With coral reefs globally at risk, scientists are asking: Can corals evolve fast enough to survive in a warming ocean?
A recent global study, co-authored by Ocean Revive’s CEO, Dr Sebastian Schmidt-Roach, on the brain coral Platygyra daedalea offers new insight. By breeding corals from 10 diverse reef regions and testing their larvae under extreme heat, researchers explored the genetic capacity of corals to withstand heat stress. Their findings shed light on the heritability of coral heat tolerance and what this means for the future of climate-resilient reef restoration.
Key Findings: Coral Heat Tolerance and Climate Adaptation
Heat tolerance in corals is partly heritable
Heritability and adaptive potential vary across populations
Corals from genetically diverse populations are more resilient
No major trade-offs were found between key fitness traits such as heat survival and settlement success
Corals from heat-stressed regions show lower genetic potential to adapt further, suggesting that past heat exposure may reduce future adaptive capacity
Rationale: Can Coral Reefs Adapt Genetically to Climate Change?
This study explored whether P. daedalea has the genetic capacity to evolve and survive as ocean temperatures rise.
The scientists focused on three key questions:
Is heat tolerance in coral larvae heritable?
Can parents pass on heat-resilient traits to their offspring?
Does a reef’s thermal history influence its adaptive capacity?
Do corals from historically warmer or more heat-stressed regions show different levels of adaptive capability?
Are there any trade-offs between heat tolerance and other key survival traits?
Does adapting to heat come with any trade-offs or constraints that might impact the corals’ survival?
Methods: How Scientists Measured Coral Heat Tolerance and Evolutionary Potential
To explore these questions, scientists paired a series of carefully designed breeding and heat stress experiments with quantitative genetics to help distinguish genetic influences from environmental ones.
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The researchers collected 105 adult P. daedalea colonies from 10 reef sites across the Indo-Pacific, Red Sea, and Persian Gulf—capturing a wide range of thermal environments.
During their annual mass spawning, eggs and sperm were collected and mixed to create controlled crosses between parent colonies, producing:
360 family crosses from 105 parents
56,000 coral larvae
Because the parentage of each larval family was known, the researchers could apply use quantitative genetics to track how inherited genetic differences influenced traits like heat tolerance.
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To test heat tolerance, larvae from each family were exposed to either:
Ambient temperatures: 27-28°C
High temperatures: 36°C – simulating extreme marine heatwaves
Larval survival was tracked until ~50% of the heat-treated group had died. Comparing survival across related families allowed the scientists to estimate genetic influence on heat tolerance.
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To understand how heat tolerance is inherited, the researchers calculated values for the following key evolutionary parameters:
Additive Genetic Variation (VA): the proportion of genetic variation passed from parents to offspring that contributes to traits such as heat tolerance
Narrow-sense heritability (h2): the proportion of total trait variation that is due to genetic inheritance
Low (<0.2) = trait mostly influenced by the environment
Moderate (0.2-0.5) = mixed genetic and environmental influence
Hight (>0.5) = trait strongly influenced by inherited genetics
They also examined:
Breeding Values: estimates how much an individual’s gene contributes to a trait compared to the population average
Positive = an individual is likely to pass on above-average performance for that trait to its offspring
Negative = an individual is likely to pass on below-average performance for that trait to its offspring
Genetic Correlations (R): describes how related two traits are at a genetic level
Positive correlation (R>0) = if one trait improves, the other is also likely to improve
Negative correlation (R<0) = improving one trait could come at the cost to the other
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Using satellite data (1985–2022), the scientists analysed how past sea temperatures shaped each population’s genetic variation. This helped test if long-term heat exposure had already filtered out genetic diversity
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To test for genetic correlations between traits and help uncover potential trade-offs or evolutionary constrains that could limit how corals adapt to rising temperatures, larvae from 30 families were exposed to:
Cold stress: 17.5°C
Ambient: 27°C
Heat stress: 33.5°C
Researchers measured larval survival and settlement to see if heat adaptation came at a cost.
Results: What Did the Researchers Discover about Coral Heat Tolerance and Heritability?
Heat Tolerance is heritable, but it varies by population
The researchers found that coral heat survival is partly inherited, with heritability ranging from 19% to 49% depending on the reef. This means genetics can explain up to half of a coral larva’s ability to survive extreme heat, but it varies across regions.
Some parent corals passed on genes that made their larvae more heat-tolerant (positive breeding values), while others didn’t (negative values). Populations with greater genetic diversity showed the widest range in performance, highlighting the importance of preserving diverse gene pools for future adaptation.
Thermal history shapes genetic potential
Corals from historically hotter regions showed lower genetic variation for heat tolerance. This suggests that natural selection may have already favoured the most heat-tolerant individuals, leaving less variation for future adaptation.
Genetic correlations suggest no trade-offs between key fitness traits
In the genetic correlation experiment, the researchers looked for correlations between survival and settlement across temperature experiments.
Larvae that survived high temperatures also performed well in cooler conditions and were just as likely to settle successfully. That means heat-tolerance didn’t reduce other key traits, making these corals strong candidates for reef restoration.
What Does This Mean for Coral Restoration?
This global study paints a hopeful yet cautious picture. It shows that coral adaptation to climate change is possible but not guaranteed. Not all populations have equal potential, and past heat stress may reduce their ability to adapt further. Conservation and restoration strategies should therefore:
Prioritise genetically diverse populations
Select heat-resilient genotypes for breeding and restoration
Incorporate assisted evolution into reef restoration planning
Conclusion: Coral Evolution as a Climate Adaptation Strategy
Genetics won't save coral reefs alone, but it offers a powerful tool in the fight against climate change. By understanding which corals can adapt, and why, scientists and reef managers can design restoration efforts that boost resilience rather than just replace what is lost.
At Ocean Revive, we believe science-backed strategies are essential for designing resilient reef restoration programs. As the climate crisis accelerates, we continuously refine our methods by integrating the latest research — from ecological insights to cutting-edge genetics — ensuring our innovations remain at the forefront of scalable coral restoration
Read the full research paper here
Bibliography
Howells, E.J., Abrego, D., Schmidt-Roach, S., Puill-Stephan, E., Denis, H., Harii, S., Bay, L.K., Burt, J.A., Monro, K. and Aranda, M., 2025. Marine heatwaves select for thermal tolerance in a reef-building coral. Nature Climate Change, pp.1-4.
