In the field, in this case, in the Reef
Our researchers were at Heron Island in the southern part of the Great Barrier Reef to conduct research associated with coral spawning. Coral spawning is when corals release egg and sperm bundles into the water. This release occurs in massive synchronous events, and forms what is known as coral spawn slicks.
You don’t want to blink and miss it. It often only happens a few times a year, a few days following the late spring-summer full moons.
Coral spawning is playing an increasingly important role to aid new and innovative efforts to help restore parts of the Reef. One method our research team is using is harvesting coral spawn slicks to assist coral population recovery.
But first, our researchers needed to find coral slicks.
Spotting a slick
Previously, researchers had to try and spot a slick from a boat. As the Great Barrier Reef is roughly the size of Italy, covering large parts of the Reef could be time-consuming.
These days, the team uses drones to make the process much more efficient.
Drones are a cost-effective way to detect coral slicks in the water so the researchers can then travel by boat to where the slicks are.
Slicks can be hard to find and don’t appear very often. But when they do, they can be big and extend to up to five kilometres in length.
Collecting coral larvae
To collect coral eggs from the sea surface, researchers hit the water, both day and night.
They used a new prototype surface skimmer, which can be towed from a boat. The skimmer has such a fine mesh that it can capture and filter the coral eggs. It’s like a giant manta ray that skims the surface water to collect all the eggs and contains them within its giant body.
This equipment enabled our team to collect larvae on masse and transfer them to culturing facilities.
Once collected, the eggs were transferred to floating ponds set up in the lagoon of Wistari Reef. These floating ponds have been developed by Professor Harrison at Southern Cross University (SCU) and are used to culture coral larvae in bulk, on the Reef.
Further collaboration with QUT is trialling robotics to assist with the collecting of larvae.
Harvesting larvae in the lab
Over a week, the researchers cultured the coral eggs into swimming larvae.
From a previous research trip, researchers set up a large floating aquaculture facility on a tugboat outside Heron Reef. This trip, researchers also harvested the coral larvae in the lab so they could test differences in conditions between the floating ponds and laboratory tanks and how this influenced coral larvae development and survival.
They also began investigating techniques for tagging the larvae in the lab so they could be be identified and monitored when being placed back into the Reef.
From lab to reef: larvae on the move
Once the corals were ready to change from a swimming larva to a settled coral polyp, the team actioned small releases of the larvae directly onto the Reef.
We also settled the larvae onto different devices in the SCU larval pools. This included 3D devices provided by our collaborators at the Australian Institute of Marine Science (AIMS), and traditional flat tiles which were then deployed onto reefs.
The team has since been back to quantify how many of the juvenile corals survived on the Reef after six weeks. They found many healthy small colonies growing on the tiles.
Next steps for restoration
Once the research team has fully analysed the results of the innovative trials from the field, the team plan to visit Heron Island again in the coming months to monitor coral survival on the different tiles and devices. They’ll also conduct preliminary assessments of the larval deliveries directly onto the Reef.
For those methods that prove successful, the research team aims to scale-up restoration efforts for larger areas of the Reef to kick-start recovery for areas that need it.
This research is a collaboration with Southern Cross University and QUT, as part of the Reef Restoration and Adaptation Program (RRAP). RRAP, funded by the partnership between the Great Barrier Reef Foundation and the Australian Government’s Reef Trust, is a consortium of partners dedicated to developing effective interventions to help the Reef resist, adapt to, and recover from the impacts of climate change.
Here's a video snapshot of the research: