Media Release ·

Coral sex conceives new growth for the Great Barrier Reef

Coral sex conceives new growth for the Great Barrier Reef

#Baby coral breakthrough

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.

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.

Eight months later Professor Harrison’s team returned to Heron Island to discover more than 100 surviving juvenile corals established on the settlement tiles out 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, we returned to Heron Island for the November 2017 coral spawning and used the technique again to collect coral spawn and ensure high rates of fertilisation, producing millions of coral larvae to deliver new corals 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 again.

“We’ll be monitoring the growth of both coral colonies and working to further refine the technique for potentially larger scale 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.


Professor Peter Harrison, Southern Cross University – founding Director of the Marine Ecology Research Centre at Southern Cross University. He’s a recognised leader in coral reproduction ecology as a researcher and teacher in marine science and ecology for more than 35 years. He has been awarded more than $10 million in research funding support and completed more than 100 scientific publications. He is passionate about communicating science discoveries and has featured in more than 20 television documentaries, a TEDx talk and many hundreds of media interviews to highlight science research and promote conservation and management.

Coral Spawning – Mass coral spawning was discovered on the Great Barrier Reef in the 1980’s by Professor Peter Harrison and colleagues. This discovery altered scientific understanding of how and when most reef corals reproduce and led to a global renaissance in coral reproduction studies.

The mass coral spawning research on the Great Barrier Reef also enabled relatively predictable access to millions of spawned gametes and the development of techniques for rearing millions of larvae. These advances in knowledge have in turn led to the development of coral larval enhancement studies, sometimes referred to as larval ‘reseeding’.

Advances in these studies are important because coral reproduction in natural environments can be highly inefficient. During spawning, clouds of coral eggs and sperm float in all directions, at the mercy of the currents, winds, and waves. When egg and sperm do eventually meet, many of the resulting larvae can drift away from reefs and die. Only very few of the larvae settling on reefs take hold and reach breeding age themselves.

Larval reseeding – Larval ‘reseeding’ is an innovative technique that produces millions of larvae from eggs and sperm captured during large-scale spawning events. The resulting larvae are delivered back onto the reef via underwater mesh tents where the settlement and growth rates of the juvenile corals are monitored and quantified. This technique is a novel means of repopulating reef ecosystems that may be damaged from coral bleaching or other causes.

The technique has great potential for scaling-up restoration efforts to be ecologically meaningful at the individual reef scale. Mass larval enhancement also has significant advantages of producing greater genetic diversity among coral recruits, which is likely to improve their ability to adapt and increase resistance to future disturbances, thereby strengthening resilience and recovery rates.