Studies shows dramatic fall in baby coral numbers settling on the damaged reef after serious warming events but also change in type of coral

Photo Tory Chase

The number of baby corals settling on the Great Barrier Reef crashed by 89% after the mass bleaching of 2016 and 2017.

Researchers set out recruitment tiles at southern end of Great Barrier Reef and then counted the coral larvae settling on the bare surface. “But what we’re seeing is that [recovery is] happening a lot slower because we only have 10% of the babies.”

Across the entire reef the scientists measured an 89% drop in new corals, but that average includes a small increase in new coral in the southern-most sections of the reef, which were less affected by bleaching. The amount of baby coral declined by an even higher percentage in the northern sections. Replenishment of corals around Lizard Island dropped 98% last year on what has been seen historically. He said it was now faring slightly better, but the rate of new coral growth is still only 4%.

The researchers also found that the mix of species has shifted dramatically. Acropora, the branching and table corals that are the reef’s dominant species, declined by 93%. On a healthy reef, acropora typically make up two thirds of the corals and provide the nooks and crannies for fish and other species.

“We’re not saying the Barrier Reef is doomed, but it is on a new trajectory. The way it’s connected, the mix of species, it’s all changing.” For it to recover, the reef will need more mature coral, something that Hughes says will not happen overnight. “The main concern is it won’t be a sustained recovery because the timeline of it – a decade – is almost certainly going to include one or two future bleaching events.”