Some Corals Like it Hot

In lakes and labs, corals are getting a head start at living in hot water. A joint team of Indonesian and Dutch researchers recently found that some 37 species of corals in “marine lakes” are already adjusted to temperatures of 32.6 degrees Celsius (90.68 degrees Fahrenheit)—well beyond the temperature at which most oceanic coral bleaches. This discovery gives ecologists great diversity to restore damaged reefs.

Coral in Raja Ampat. Image credit: rizal arif cahyadi

While most corals can bounce back after a heatwave, ecologists know they need a back up plan for a prolonged hot spell. Their solution was to create captive coral populations, which could be exposed to higher temperatures in laboratory conditions. These lab-bred coral could be spread among a damaged reef to reseed with more resilient individuals. The idea, called “assisted evolution”, was initially met with hesitation.

But in Raja Ampat—an Indonesian archipelago—researchers have found a similar situation has arisen naturally. Raja Ampat has many caves, some of which host underwater rivers. Marine lakes, landlocked on the surface but fed seawater below, were the focus of the Indonesian-Dutch joint coral study. These lakes are shallower and hotter than the ocean, but many species of coral have taken hold and adjusted to the conditions. Young coral polyps born in these hot lakes may be swept to the ocean, where they would settle onto existing reefs.

The lake corals of Raja Ampat are a welcome reminder that nature is tougher than it first seems. And they are a source of healing for the future which we will sample to restore reefs,