Climate change is expected to devastate coral reefs because warmer oceans are believed to be inhospitable to corals. Now, a team of scientists has taken a step toward identifying genetic mechanisms that might be giving some corals a natural resilience to thermal stress.
Coral reef ecologist Daniel Barshis and colleagues at Stanford University took advantage of markedly different conditions in two pools on a reef at Ofu Island in American Samoa. Because of local factors that isolate some areas of the reef from winds and waves, some pools in the reef are highly variable in temperature. They have summertime water temperatures topping 93 degrees. Yet a common reef-building coral found in these pools grows faster and is more thermally tolerant than corals of the same species in nearby pools that do not get as hot.
The team took samples of corals from both the highly variable and the moderately variable pools and subjected them to experiments while monitoring the levels of expression of a wide range of genes. They identified 60 genes with an unusual expression pattern. Under normal temperatures, these genes were more active in the corals from the highly variable pool. But when water temperatures rose, they were more active in the corals from the moderately variable pool. The scientists speculate that higher gene expression under normal conditions might be preparing these resilient corals for periodic hot water, the team reported online in the Proceedings of the National Academy of Sciences.
It’s not yet clear if this resilience reflects short-term acclimatization or adaptation that might be passed on to future generations within a coral population, or whether other factors might be at play.