Coral sex conceives new growth for the Great Barrier Reef

Published 26 November 2017
Professor Peter Harrison Professor Peter Harrison

For the first time, researchers have accelerated the formation of new coral colonies on small areas in the Great Barrier Reef using ‘baby corals’ conceived and successfully settled directly on the Reef through a pioneering pilot project funded by the Great Barrier Reef Foundation.

Professor Peter Harrison discusses the formation of new coral colonies.

The scientist who co-discovered the phenomenon of ‘sex on the Reef’ – mass coral spawning – some 30 years ago is 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.

“The success of this new research not only applies to the Great Barrier Reef but has potential global significance – it shows we can start to restore and repair damaged coral populations where the natural supply of coral larvae has been compromised.”

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 Professor Harrison’s 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.

The pioneering pilot project was made possible through a donation to the Great Barrier Reef Foundation from the former chairman of Goldman Sachs, Australia and New Zealand, Stephen Fitzgerald, who is now based in the UK.

“Working with the Great Barrier Reef Foundation board for many years, I’ve seen firsthand what’s been happening with our Reef, and reefs around the world, facing such adversity from the impacts of climate change,” Mr Fitzgerald said.

“When I heard about the amazing success Peter was having with his work, I knew I had to help get it happening on the Great Barrier Reef so we could prove the concept would work on the world’s largest and greatest coral reef, our $56 billion natural wonder,” he said.

“It’s wonderful to have another tool in the arsenal for our Great Barrier Reef,” Great Barrier Reef Foundation Managing Director Anna Marsden agreed.

“We’re increasingly looking to innovations like larval ‘reseeding’ to help coral reefs rebuild and adapt so they can live through everything the world is throwing at them and survive into the future.

“It’s time to be bold and take some calculated risks because that’s the way we’ll make a step change in how we can help restore our coral reefs.

“I’m confident that we have some of the best and brightest minds working on solutions for the Great Barrier Reef right now and it’s a great result that the Foundation has brought together the expertise of Professor Harrison’s Southern Cross University team and the philanthropic leadership of Stephen Fitzgerald to create this advance for the Reef.

“It’s also important to keep in mind that restoration options like this don’t lessen the need for strong action to reduce the major drivers of reef decline being climate change, water quality and pest management.

“There is much more to be done but this is definitely a great leap forward for the Reef and for the restoration and repair of reefs world-wide.”

The new research was not without its challenges, including the need for careful rearing of coral larval cultures and complex diving operations on the reef by the research team.

The team worked closely with the Great Barrier Reef Marine Park Authority to implement this ground-breaking pilot project.

“Innovative science like larval reseeding is one piece in the puzzle of protecting the Reef into the future,” Great Barrier Reef Marine Park Authority Chief Scientist Dr David Wachenfeld said.

“In recent years, the impacts of climate change on the Great Barrier Reef have undoubtedly accelerated, as we saw with back-to-back years of coral bleaching.

“It is vital everyone keeps working to address climate change and build the Reef’s resilience, and for restoration strategies to be developed that can work over large areas.

“We need to be more proactive and intervene to give the Reef a better chance and that’s why supporting leading-edge research like this is a priority for the Great Barrier Reef Marine Park Authority.

“The success of these first trials is encouraging – the next challenge is to build this into broader scale technology that is going to make a difference to the Reef as a whole.”

Based on the success of the 2016 pilot project funded by the Great Barrier Reef Foundation, the Australian Government is investing funds to advance Professor Harrison’s larval reseeding research, including investigating techniques to scale up the delivery method to apply on a larger scale and pioneering the collection of natural spawn slicks for restoring the Reef.

“With this new funding from the Australian Government and continued support from the Great Barrier Reef Foundation and the Great Barrier Reef Marine Park Authority, our research team used the technique again this month at Heron Island to collect and ‘match-make’ coral spawn, producing mass quantities of coral larvae to deliver new coral ‘babies’ onto the reef,” Professor Harrison said.

“I’m excited to announce that we’ve already observed successful settlement of the new coral larvae this year so it’s worked.

“We’ll be monitoring the growth of both coral colonies and working to further refine the technique for potentially broader application in the future,” he said.

Professor Harrison’s Great Barrier Reef research builds on the success of his team’s work in the Philippines in an area of reef highly degraded by blast fishing, which had similar positive results.

“Our previous studies in the Philippines funded by the Australian Centre for International Agricultural Research, showed that corals can grow from microscopic larvae to dinner plate sized adult colonies within three years and they were able to sexually reproduce. This work at Heron Island is the first step towards proving we can apply these techniques on the Great Barrier Reef,” 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.

 Media release written in conjuction with Great Barrier Reef Foundation. Vision, images and interview opportunities available on request.

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Photo: Professor Peter Harrison

Media contact: Jessica Nelson (Huxley), Southern Cross University 0417288794,