Within-population variability in coral heat tolerance indicates climate adaptation potential

Area of Science:

• Marine Biology
• Climate Change Science
• Ecology

Background:

• Coral reefs face mass bleaching and mortality due to marine heatwaves and climate change.
• Coral adaptation potential relies on individual heat tolerance variation and heritability.
• The extent of heat tolerance variability within coral populations remains largely unknown.

Purpose of the Study:

• To quantify the variability in heat tolerance within a coral population.
• To assess the potential for coral adaptation to marine heatwaves.

Main Methods:

• Exposing corals from a single reef to an experimental marine heatwave.
• Comparing bleaching and mortality responses between the most and least heat-tolerant coral individuals.

Main Results:

• The most heat-tolerant 10% of corals required double the heat stress dosage to bleach compared to the least tolerant 10%.
• All least-tolerant corals died, while the most-tolerant survived the heat stress exposure.
• Differences in heat tolerance thresholds could delay annual bleaching and mortality by 10-17 years, depending on emissions scenarios.

Conclusions:

• Substantial variability in coral heat tolerance exists within populations, indicating potential for natural or assisted evolution.
• Coral adaptation can provide short-term relief from climate change impacts.
• Ambitious emissions reductions are crucial for coral reef persistence alongside adaptation efforts.