Coral reefs are a significant source of biodiversity and may support up to 25 percent of life in the ocean. Corals around the world are also under intense pressure as the oceans warm, acidify, and become more polluted. About half of the coral cover in Australia's Great Barrier Reef is thought to have been lost in only the last three decades. Now researchers have found that genetic sequencing could help researchers engineer coral strains that are able to survive in warmer temperatures. The work, which might complement or assist ongoing conservation efforts, has been reported in Science.
"We need to use as many tools as possible to intervene or we will continue to see coral reefs vanish," said the first author of the study Zachary Fuller Ph.D., a postdoctoral researcher in biology at Columbia University. "Using genomics can help identify which corals have the capacity to live at higher temperatures and reveal genetic variants associated with climate resilience."
Coral reefs don't only provide a habitat for marine species. They also help protect coastlines from storm damage and flooding and help provide economic benefits to people.
When an ocean is hit by extremely high temperatures, it can destroy an important symbiotic relationship, as the photosynthetic algae that live in symbiosis with coral leave it. That turns the coral white or bleaches it, and the coral can starve to death because they rely on the algae for nutrients. An initial wave of bleaching happened to coral reefs worldwide in the 90s, and more have happened since. Some reefs can spring back after these damaging events, but the repeated stress can destroy them eventually.
This study showed it's possible to predict, to a degree, which reefs will survive.
"Genomics allows us to examine the genetic differences that could influence survival and bleaching tolerance, helping us work out how we might support coral health," said the senior study author Molly Przeworski, a professor in the Departments of Biological Sciences and Systems Biology at Columbia.
The researchers gathered samples from twelve locations along the Great Barrier Reef, and looked for genetic signatures of tolerance to bleaching.
"What we discovered is that no single gene was responsible for differences in a coral's response to bleaching, but instead many genetic variants influence the trait," Fuller said. "On their own, each has a very small effect, but when taken together we can use all these variants to predict which corals may be able to survive in the face of hotter seas."
This study may also help scientists learn more about other species that are risk from climate change, noted the authors.
"The best chance we have to save what's left of the Earth's coral reefs is to mitigate the effects of climate change by rapidly reducing greenhouse gas emissions," Fuller said. "In the meantime, genetic approaches may be able to buy us time."