Stanford scientists have identified heat resistant corals in the backreef of Ofu, an island in American Samoa. They say these corals may offer hope for reefs suffering the effects of climate change. (Photo courtesy of Stephen Palumbi)

Beneath the sea, in the fight for survival, coral reefs are thriving in the turquoise lagoons of a tiny, volcanic outcrop island called Ofu. This island in American Samoa houses the Muhammad Ali of corals, able to thrive in temperatures that would knock out most counterparts.

Tough corals like these may be among the last line of defense for one of the most diverse ecosystems in the world. Coral reefs are under distress across the world due to rising seawater temperatures and increasingly acidic ocean conditions. Those climate change related threats are compounded by everything from coastal pollution to overfishing to spreading epidemics of coral disease. This is bad news for local communities, commercial fisheries, and thousands of reef species themselves.

Coral reefs occupy less than 0.1 percent of the world’s marine environment, yet they support almost one third of the world’s marine fish species. They are hotspots of diversity and life, sometimes called the rainforests of the sea.

This spring, six scientists set out to find coral species tough enough to withstand all these insults. The team, led by Stanford University marine ecologist, Stephen Palumbi set out for American Samoa and the Cook Islands, a location where they hoped to find evidence for more strong corals. They went armed with a coral stress tank, designed to mimic the conditions of extreme warming, to help them separate the tough corals from the wimps. The team’s first stop was the island of Ofu, where tough corals had been previously tested, followed by an unexplored site at Rarotonga in the Cook Islands. At both sites, small pieces of coral were removed from the reef and placed in the stress tanks to test their heat threshold. The corals are then submerged in sea water inside the tank and exposed to severe temperatures. What Palumbi and his colleagues found was surprising.


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