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The challenge

Coral reefs are suffering from major global and local disturbances

We are working with remote sensing scientists to understand the spatial extent of coral spawning slicks along the Great Barrier Reef. The thin pink line at the edges of the fingers of reef is a spawn slick that has formed as waters mover off the reef on the morning after spawning.

Coral reefs provide ecosystem services, such as fisheries and tourism, worth more than $6 billion per year in Australia alone. Yet a combination of global and local stressors are degrading the state of coral reefs and severely reducing their long term resilience and capacity to recover.

Coral restoration initiatives have previously been limited to highly localised efforts, but upscaling restoration to ecological meaningful scales is necessary in order to provide the capacity to safeguard reefs until global stressors such as coral bleaching from human induced climate change are reduced.

Our response

Approaches and implementation of industrial scale coral reef restoration

We are testing the effectiveness of large scale restoration using population models, field trials, and remote sensing approaches.

We are using industrial techniques to harvest coral spawn on a large scale. The photo shows a portion of coral spawn slick captured by a floating oil boom usually used for harbour clean-ups.

Population models have been developed using the best available demographic information from the literature. Models compared two potential large-scale restoration strategies: the harvesting, development, and release of wild coral spawn slicks onto a target reef, with the transplantation of gravid coral colonies to provide a seed population and local source of larvae.

Along with our industry partner Van Oord Dredging and Marine Contractors, and Delft University, we conducted a feasibility study to test fundamental components necessary for the large-scale harvesting and long distance transportation of wild coral spawn slicks. The study tested our ability to locate and concentrate spawn slicks for collection, the survival of coral embryos following pumping, comparison of survival using two different industrial scale pumps and the capacity to culture the harvested embryos through to competent larvae in a 50,000 litre aquaculture facility on board a tug boat. Funding was provided through an Advance Queensland Small Business Innovation Research grant.

Understanding of the abundances and movements of coral spawn slicks is needed to quantify their potential for sustainable harvest should this approach be implemented in large-scale restoration efforts. Working with members of our remote sensing team, we are examining the spatial extent and locations of coral spawn slicks throughout the Great Barrier Reef.

The results

Preliminary findings

Comparing the costs and benefits of harvesting wild coral spawn slicks with transplantation of gravid coral colonies has indicated (in published research) that the controlled release of coral spawn slicks has the potential to achieve large-scale restoration of coral communities with low impact technology at low cost per colony.

Our feasibility study was conducted in November-December 2018. Initial outcomes demonstrate we have the ability to successfully contain wild coral spawn slicks, harvest them onto a large vessel using two pumping approaches, and culture them until the larvae are competent to transition to new colonies on the reef.

The fact that this can be done using large commercial vessels shows that this approach can be used to transport corals across the entire length of the Great Barrier Reef. The next stage of the project will aim to upscale the approach even further and apply large scale restoration providing hundreds of millions of larvae to reefs needing restoration.

[Music plays and CSIRO logo and text appears on a blue screen: RECRUIT Recovery of Reefs Using Industrial Techniques]

[Image appears of a reef on the ocean floor and then the image changes to show fish swimming through coral]

Russ Babcock: Because the reef has been affected by things like leaching and cyclones over quite large areas it’s not going to be enough in the future to just help one part of a reef recover that’s been damaged.

[Image changes to show Russ Babcock talking to the camera on a ship with the ocean in the background and text appears: Russ Babcock, Senior Principal Research Scientist, CSIRO]

We’re going to have to take larvae from up in the northern part of the reef for example to the central region, or from the central region to the southern region because whole swathes of reef have been affected and there may not be coral left there that we can use to kick start this type of recovery.

[Images move through of a crane to delivering equipment from a small boat to a male on the ship, a male securing a sling, an aerial view of the ship, and a male pumping water into tanks on the ship]

Christopher Doropoulos: So, we’re out here to try and collect some coral spawn slicks, capture those, and then pump them onto our vessel into our massive aquaculture set up that we’ve got going.

[Image changes to show the coral spawning and then the image changes to show Christopher Doropoulos talking to the camera on the deck of a ship and text appears: Christopher Doropoulos Research Scientist, CSIRO]

Corals generally spawn once a year and for a couple of hours for one or two nights. My main concern was about whether we would even find a coral spawn slick. We found those in the hugest abundance I’ve ever seen in my life.

[Images move through to show an aerial view of an ocean spawn slick, a male looking into a microscope in a laboratory, two males working in a laboratory, and a male testing coral density]

So, in the laboratory on the ship and on land we’re checking for competency and we’re also checking how dense the corals are and how well they’re surviving.

[Image changes to show men operating a crane off the side of the ship, and then the image changes to show an aerial view of the ship]

Russ Babcock: We’ve found that the density of larvae in slicks is at least a thousand times higher than has previously been recorded in the literature.

[Image changes to show Russ talking to the camera while standing on the ship’s deck]

So, that means that it’s going to be potentially easier to get the number of larvae that we need to do this work.

[Images move through to show a male engineer working at his computer, a male crew member working, two male ecologists standing over a tank testing samples, and Chris talking to the camera]

Christopher Doropoulos: We had engineers, we had the crew of the ship, we had ourselves as ecologists all coming together in a partnership to actually scale this up and make it work effectively.

[Image changes to show an aerial view of males working on the ship and the camera pans in a clockwise direction over the ship’s deck]

Russ Babcock: We’ve shown that we can harvest natural slicks after coral spawning.

[Image changes to show three male ecologists testing coral samples in a laboratory]

We’ve shown that they can be pumped on board the vessel and they’ll survive and we’ve shown that they’re able to grow and develop to the point where they’re able to settle back on the reef.

[Images move through to show aerial views of the ship, three males operating a crane from the side of ship, a male pumping water into tanks, and then Russ talking to the camera]

And because we can get these larvae on board a vessel we can transport them from one end of the reef to the other which is what we really need to achieve if we’re going to be successful in protecting the reef.

[Music plays and text appears on a white screen: Project collaborators, Van Oord, Delft University of Technology, Special acknowledgements, Pacific Tugs, Hidrostal Pumps, This project is funded by the Australian and Queensland Government through the Advance Queensland Small Business Innovation Research initiative]

[CSIRO logo and text appears: CSIRO, Australia’s innovation catalyst]

We are assessing the prospect of implementing coral reef restoration at the scale of the entire Great Barrier Reef.

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