How long can corals live?

Some deep-sea coral colonies can survive for thousands of years, which makes them the oldest-known colonial organisms. Corals are unique animals, though, so answering the question of exactly how long they live depends on how you count!

The life of a coral is complicated. After beginning life drifting or swimming in the water, a coral larva eventually settles to the seafloor. Once anchored, the larva grows into a small, sea anemone-like polyp. The polyp clones itself, forming a colony of genetically identical polyps connected by the exoskeleton or tissues they build together. That colony is usually what we think of as a single coral, but things can still get stranger. Sometimes parts of one colony will break off and start growing somewhere else, forming a “new” coral even though the polyps are still genetically identical to the original colony.

Those details make deciding how old a coral is challenging. Individual polyps may only live a few years, but their colonies and genetic code can survive for much longer. The oldest known coral colony is a “black coral” in the genus Leiopathes, which was found in the deep sea near Hawaii. By carbon dating its skeleton, scientists found that the black coral colony was about 4,265 years old. In 2016, other researchers found a group of shallow-water elkhorn corals that all appeared to have grown from fragments of a single original coral, making their shared DNA over 5,000 years old.

The extreme ages reached by slow growing deep-sea coral colonies can help scientists in surprising ways. Certain types of black corals and bamboo corals form growth rings in their skeletons much like a tree. Studying the chemistry and thickness of those rings can teach us about ocean conditions like temperature and acidity as they were hundreds or thousands of years ago.