Here’s a riddle for you: What animal behaves like a plant?

The answer is coral. These tiny, transparent organisms live mostly in colonies, connected by living tissue through which they share nutrients.

But they often can’t consume enough nutrients to live. So, they rely on special symbiotic algae in their tissues—meaning most corals require sunlight, like a plant.

The algae take in sun and carbon dioxide and produce oxygen and sugars, which the corals consume to grow and produce the hard exoskeletons that give the reef its shape.

However, seas are becoming warmer and more acidic, which stresses the corals’ algae, causing them to produce toxins. The corals respond by expelling or digesting them.

Without the algae, the corals lose their nutrients and their vibrant colors, which is why this is called “bleaching.” If they can’t replace their algae, they die.

In the last decade, a third of the world’s reefs experienced some bleaching and coral death.

But some parts of these reefs survived, and scientists have realized it’s because their algae could tolerate the heat, acidity, or both.

Scientists are now sequencing the DNA of these “super algae” to see if they could genetically enhance other coral algae to make them hardier.

Coral reefs are a source of great biodiversity in the ocean and support the livelihoods of half a billion people around the world.

Good reasons to hope we can help them adapt to warmer seas.