SciTech | 1727253035 | 11 min read Scientists find heat-tolerant corals hidden in plain sight

#Lismore (Australia)
Just as individual humans handle stress differently, so do corals. Even coral colonies of the same species, growing side by side, vary in their tolerance to pressures such as heatwaves.

In research published, we discovered surprising new evidence of variable heat tolerance in corals. As the world’s oceans warm, these differences are important.

Earlier this year, the world’s fourth global mass bleaching event was declared. The Great Barrier Reef has suffered five mass bleachings since 2016 – most recently this past summer. The declarations followed the world’s warmest year on record.

To keep the world’s coral reefs healthy and functioning, global carbon emissions must be dramatically curbed to reduce the rate of ocean warming. As humanity works towards that goal, interventions may buy time for corals to survive in their warming environments.

Nature and Nurture
Corals handle stress differently for two reasons: nature and nurture. Each coral has a unique “nature” or genetic makeup that can affect its heat tolerance. Results suggest corals found across the entire Great Barrier Reef may hold unique genetic resources that are important for recovery and adaptation.

However, aspects of the marine environment may nurture, or hinder, a coral’s heat stress response. These include water temperatures, nutrient conditions, and the symbiotic algae living inside coral tissue.

We found corals living in warmer regions, such as the northern Great Barrier Reef, can handle higher water temperatures. However, because the water is so warm in these areas, the corals are already pushed close to their temperature limits.

Corals in the southern Great Barrier Reef cannot handle temperatures as high as their northern neighbours.  These tolerance patterns may affect which corals survive heatwaves.

Giving our reefs a future
Findings have potentially important implications for the ability of corals to adapt to warmer seas under climate change.

The results may also inform reef restoration and conservation efforts. For example, heat-tolerant parent corals could be selectively bred to produce offspring better suited to warmer waters.

The success of such programmes depends on the extent to which a coral’s genetic makeup controls its tolerance to heat. So, the next step in this research is investigating these genetic differences.
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Selective breeding trials are already underway, using the most heat-tolerant corals identified in this study.Agencies