Great Barrier Reef corals aren’t repopulating very quickly

Enlarge / Bleached coral in March 2017. (credit: G Torda / ARCCOE / Flickr)

Australia's Great Barrier Reef was hit hard by warm ocean water in 2016 and 2017, causing back-to-back disasters filled with widespread coral die-offs. During marine heatwaves, corals are forced to expel the single-celled symbiotes that photosynthesize inside them. This leaves the corals a pallid white color—a process called "bleaching."

If this bleaching lasts too long, the corals die. That's what happened along much of the Great Barrier Reef (the southern end has largely avoided bleaching). And, if the reef doesn't recover quickly, it could suffer from a long-term degradation.

The question—asked with fingers firmly crossed—was whether the reefs would find a way to bounce back quickly, repopulating with a new generation of corals. Unfortunately, a new study published this week shows that the first year's data is not encouraging.