Inside the coral nursery growing a reef back

Divers at a coral nursery are growing a damaged reef back one small piece at a time, starting each new coral from a fragmentfragmenta small piece broken off from something larger no bigger than a finger.

Each fragment is clipped onto an underwater frame shaped like a tree, where it grows for about a year before divers glue it directly onto the damaged reef itself.

Coral grows slowly — often just a few centimetres a year — so a nursery-raised piece needs roughly two years in total before it's sturdy enough to survive storms and fish nibbling at its edges.

The team tracks which coral types survive best in warmer water, since the reef they're rebuilding has already lived through two serious heat events in the last decade.

So far more than 3,000 coral fragments have been transplanted back onto the reef, and divers say the first ones planted three years ago are now large enough to shelter small fish of their own.