Corals in places with widely fluctuating temperatures, such as areas of extreme high and low tides, are naturally resistant to temperature stress. A study published in Nature Communications Tuesday (September 17) found that although the stress-resistant coral Acropora aspera can maintain its health during heatwaves, its resilience is limited after adapting to a warmer climate.
Verena Schoepf and colleagues at the University of Western Australia transferred corals from a reef with variable temperatures in Northwest Australia to tanks that were either cooler or warmer on average. The cooler corals showed some signs of cold stress, but were still able to survive and acclimate—and they could cope with heatwaves. The ones in slightly warmer temperatures also adapted, as long as the heat was in a normal seasonal range. But once the researchers gave all of them two-week heat stress tests to examine their heat tolerance after acclimating to cooler or warmer temperatures, the warmer ones experienced bleaching at the same temperature threshold as the cooler ones. Even though these animals had adapted to a warmer baseline, their temperature threshold for bleaching didn’t also go up.
The team concluded that even if corals adapt to increased heat, they may not be able to adjust to an environment with generally higher temperatures. However, their cold tolerance suggests that they could be transplanted into damaged reefs living in cooler environments to help restore reef health.
V. Schoepf et al., “Stress-resistant corals may not acclimatize to ocean warming but maintain heat tolerance under cooler temperatures,” doi:10.1038/s41467-019-12065-0, Nat Commun, 2019.
Emily Makowski is an intern at The Scientist. Email her at firstname.lastname@example.org.