Scientists successfully breed corals to improve their heat tolerance

A new study has shown that selective breeding can lead to a slight increase in corals’ heat tolerance.

Led by experts at the University of Newcastle’s Coralassist Laboratory, the study documents the world’s first effort to selectively breed adult corals for improved heat tolerance, i.e. the ability of adult corals to to survive intense marine heat waves. The breeding effort was a success, showing that it is possible to improve the heat tolerance of adult coral offspring, even in a single generation.

However, the improvement was modest compared to future marine heatwaves expected due to climate change. The authors emphasize that rapid reductions in global greenhouse gas emissions are an absolute necessity to mitigate warming and give corals the opportunity to adapt.

The study, published in the journal Natural communicationswas produced in partnership with the University of Victoria, Horniman Museum and Gardens, Palau International Coral Reef Center, University of Derby and University of Exeter.

The publication is the result of a five-year project initiated by Dr James Guest.

Not a miracle solution

“This work shows that selective breeding is feasible but is not a silver bullet and that further research is needed to maximize breeding results,” says Liam Lachs, lead author of the study and postdoctoral research associate at the University of Newcastle. He goes on to emphasize that “at the same time, rapid reductions in global greenhouse gas emissions are an absolute necessity to mitigate warming and give corals an opportunity to adapt.

Dr Guest, Reader in Coral Reef Ecology at the School of Natural and Environmental Sciences at the University of Newcastle, explains that “the results show that selective breeding could be a viable tool for improving population resilience. .

“How many corals need to be transplanted to benefit wild populations? Can we guarantee there is no trade-off (the evidence so far suggests this is not a significant risk)? How can we avoid dilution of selected traits once added to nature? How can we maximize responses to selection?

“Given the moderate levels of improvement we achieved in this study, the effectiveness of such interventions will also depend on urgent climate action.”

Successful reproduction attempt

Selective breeding has been practiced by humans for thousands of years to produce animals and plants with desirable traits. It is now considered a tool for nature conservation, particularly coral reefs.

These marine ecosystems are on the front lines of the impacts of climate change, as reef-building corals are very sensitive to marine heatwaves. These can trigger massive coral bleaching and mortality events that have already led to considerable decline of reefs globally.

The experts carried out selective breeding trials for two different traits, either tolerance to short and intense exposure to heat (10 days, reaching +3.5°C) or less intense but long-term exposure more typical of natural marine heatwaves (1 month, reaching +2.5°C).

The team found that selecting parental colonies for high rather than low heat tolerance increased the tolerance of adult offspring. This result is valid for the response to 10-day and 1-month exposures. Heat tolerance could theoretically be improved by around 1°C/week in one generation. However, this level of improvement is likely insufficient to keep pace with continued warming.

What’s next?

Selective breeding for short-term stress tolerance has not shown evidence of improving the ability of offspring to survive long exposure to heat stress. In the absence of detected genetic correlation, it is plausible that these traits are under independent genetic control.

This would have important implications, as interventions would benefit from rapid, inexpensive tests that can effectively identify heat-tolerant colonies for reproduction. However, if these analyzes do not predict the survival of adult colonies in the face of natural marine heatwaves, this represents a significant challenge for management interventions.

Lead author of the study, Dr Adriana Humanes, a postdoctoral research associate at the Coralassist laboratory at the University of Newcastle, emphasizes that “considerable work remains to be done before selective breeding can be successfully implemented . genetically correlated. »

Takeaway message

The authors say this work is an important proof of concept: selective reproduction of corals for adult survival during a heatwave is possible. They are now calling for more research and development to understand how to operationalize breeding interventions and maximize outcomes, in hopes of keeping pace with lower levels of warming that can be achieved through concurrent climate action.