Coral sex could save the Great Barrier Reef

Australian researchers have succeeded for the first time in promoting the formation of new coral colonies in the Great Barrier Reef using ‘baby corals’. The Great Barrier Reef has lost nearly half of its coral in the past two years.

The same scientist who helped discover the phenomenon of ‘sex on the Reef’ – mass coral spawning – some 30 years ago is now leading the breakthrough which aims to accelerate regrowth of corals.

“This is the first project of its kind on the Great Barrier Reef to successfully re-establish a population of juvenile corals from larvae settling directly on the reef,” said Southern Cross University’s Professor Peter Harrison, lead researcher on the project.

“This pilot study carried out on Heron Island shows that our new techniques to give corals a helping hand to conceive and then settle, develop and grow in their natural environment can work on the Great Barrier Reef.

During the November 2016 coral spawning, Professor Harrison and his team travelled to the Great Barrier Reef’s Heron Island for the Australian-first trial. They collected vast quantities of coral eggs and sperm during mass spawning, using them to grow more than a million coral larvae, and then delivered the larvae onto reef patches in underwater mesh tents.

Twelve months on, the team returned to Heron Island during the November 2017 mass spawning event to discover that the surviving juvenile corals had successfully established themselves on the Reef.

“The results are very promising and our work shows that adding higher densities of coral larvae leads to higher numbers of successful coral recruits,” Professor Harrison said.

He sees great promise in the mass larval restoration approach and says it has the potential to make a difference to reef recovery on a larger scale using natural coral spawn slicks that contain many millions of larvae from different coral species.

The larval restoration approach contrasts with other reef restoration methods like so-called coral gardening which relies on breaking apart healthy corals and sticking branches back onto reefs in the hope they’ll regrow, or growing corals in nurseries before transplantation.

“Coral gardening is the most widely used technique in other reef regions but we know it is expensive and often doesn’t work very well and sometimes it fails completely,” he said.


Image credit: NASA

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