Researchers from Newcastle University, UK, found a remarkable variability in corals when it comes to tolerance to heat, according to a study published in the journal Proceedings Of The Royal Society B: Biological Sciences.
Marine heat waves have destroyed many corals in the past few years and potentially many more in the future if climate change continues at current rates.
To test how resilient corals are to temperature changes, a team of researchers exposed corals collected from a single reef to a controlled heatwave. Results showed significant variability in how much corals can cope with temperature changes, with the most tolerant corals dealing with double the heat stress to induce bleaching compared to the least susceptible.
By the end of the heat stress exposure, the least tolerant corals were all dead, while the most tolerant were still alive. What’s causing this variation is still a mystery; it does not seem to be related to the type of symbiotic algae associated with the corals. The researchers believe that some of the corals are simply more heat tolerant.
“It is well known that corals vary in their tolerance to heat stress among species and in different locations, but marine scientists have rarely examined how much variation there is among corals living side by side on the same reef. Despite these corals experiencing the same conditions, we found a remarkable variation in heat tolerance among individuals, suggesting the capacity for adaptation if some of the toughest corals are able to survive marine heatwaves,” said co-author Dr. James Guest, from the School of Natural and Environmental Sciences.
“Individual variation in heat tolerance is critical if corals are to adapt to higher temperatures. We show that under an ambitious future emissions scenario, the differences we have found equate to up to 17 years of delay until the onset of annual bleaching and mortality conditions. However, this delay is limited to only ten years under a high emissions scenario,” added study lead authors Dr. Adriana Humanes Schumann and Liam Lachs from the same research group. “For coral reefs to persist through the coming century, coral adaptation must keep pace with ocean warming. However, at the same time, the global emissions reductions of greenhouse gasses countries have already committed to need to be realised to give corals a fighting chance.”
According to the authors, these climate projections for the future have the potential to be extremely valuable for policymakers and can influence coral reef conservation and restoration actions.
Humanes, A., Lachs, L., Beauchamp, E., Bythell, J., Edwards, A., & Golbuu, Y. et al. (2022). Within-population variability in coral heat tolerance indicates climate adaptation potential. Proceedings Of The Royal Society B: Biological Sciences, 289(1981). doi: 10.1098/rspb.2022.0872