Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0810875106 (2009)

The longevity of deep-sea corals has been much debated: radiocarbon dating provides estimates of millennia, but counting growth rings gives ages of only a few hundred years. Brendan Roark at Texas A&M University in College Station, an advocate of the radiocarbon approach, now reports with his colleagues more evidence for extremely long-lived corals.

They show that, in some cases at least, the organic carbon that is acquired by the corals is 'fresh'. It is carbon rapidly transported from the surface ocean to the depths at which the corals live, rather than old sea-floor carbon in which the radioactive carbon-14 has already decayed.

The fresh diet means that the carbon-14 levels in the corals should accurately reflect their ages. On this basis the team estimates members of the black-coral genus Leiopathes to be 4,265 years old.