http://www.sciencemag.org/news/2018/05/great-barrier-reef-has-had-five-near-death-experiences-past-30000-years

Corals along Australia’s Great Barrier Reef are struggling to cope with rising sea temperatures.

Thirteen thousand years ago, as the last ice age ended, entire stretches of Australia’s Great Barrier Reef perished. Rising sea levels blanketed the world’s largest collection of corals with sediment coming off the newly inundated land, blocking the sunlight corals need to grow. The reef eventually recovered, but it took hundreds to thousands of years. This near death and eventual resurrection wasn’t a one-off, according to a new study that reveals the reef’s shifting boundaries over geological time. It’s a tale that has played out five times over the past 30,000 years—and it may be happening again today.