New research suggests coral colonies can persist for thousands of years, much longer than previously thought. Scientists discovered 5,000 year-old genotypes of elkhorn corals, Acropora palmata, in Florida and the Caribbean.

For conservationists, the research -- detailed in the journal Molecular Ecology -- offers both good and bad news.

"Our study shows, on the one hand, that some Acropora palmata genotypes have been around for a long time and have survived many environmental changes, including sea-level changes, storms, sedimentation events and so on," Iliana Baums, associate professor of biology at Pennsylvania State University, said in a news release. "This is good news because it indicates that they can be very resilient. On the other hand, the species we studied is now listed as threatened under the U.S. Endangered Species Act because it has suffered such sharp population declines, indicating that there are limits to how much change even these very resilient corals can handle."

Until now, scientists relied on size as the best approximation of a coral colony's age. But some colonies continuously fragment as small pieces of coral break off and colonize new territory.

Researchers turned to genetics for a better way to date coral. Because genetic mutations accumulate at a more or less constant rate, researchers decided to use mutations as a proxy for age.

Analysis revealed 5,000-year-old genotypes.

"This was surprising, as previously, only cold-water corals were found to be older than 1,000 years," said Baums. "Knowing the age of individuals in a population is important for understanding their population history and whether the population is increasing or decreasing. It is especially important when the population under study is threatened."

The past heroics of Acropora palmata offers conservationists hope the coral can survive global warming -- but it's no guarantee.

"What is different now is that human-induced climate change is happening at a rate that far exceeds past environmental changes," Baums said. "Therefore, the coral's past ability to survive environmental change does not necessarily predict their future success."