Corals Learn to Live in Hotter Water

Nature is on the move as the world warms. Scandinavian birds are flying north – and tropical corals are adjusting to the rise in temperatures.

The last is a surprise:  the experience of El Niño years is that reef corals have been vulnerable as sea temperatures creep up.  They can recover, but higher water temperatures are not healthy for reef ecosystems.

But Stephen Palumbi of Stanford University in California and colleagues report in the journal Science that at least some corals learn to adjust to hot water – and have been observed doing so at least 50 times faster than the pace of evolutionary change suggests that they should.

Coral reefs are, like the tropical rainforests, among the richest ecosystems on the planet: they are of economic importance for up to a billion people, as sources of food, as tourist attractions and as natural protection from storms.

There have been repeated alarms about the impact both of global warming and of the steady change in ocean water chemistry on tropical reefs that have already been weakened by pollution, predation and commercial exploitation.

But Palumbi and colleagues decided to take a closer look at the coral animal’s living arrangements in American Samoa, where temperatures in shallow reefs can reach 35°C when low tide is around noon.  Most corals are at risk at water temperatures of 30°C.  So some native corals had clearly learned to adjust.

The reasoning is that corals must have adaptive genes that can be turned off or switched on when conditions change.

The research suggests that corals stand at least some chance of adjusting to a warmer world.

Corals Learn to Live in Hotter Water