The Great Barrier Reef Restoration Symposium will feature what is believed to be the world’s first multidisciplinary scientific sessions dedicated to control of crown-of-thorns starfish (COTS). Importantly, the sessions will include presentations from researchers, managers and on-water operations staff, including the tourism industry.
Sheriden Morris of the Reef and Rainforest Research Centre (RRRC) said that of all the threats facing the Reef – such as climate change and declining water quality – outbreaks of coral-eating COTS were amongst the most amenable to actual intervention.
“However, in the past, both control and research efforts have been patchy and not well-coordinated,” she said. “Since 2015 we have been steadily implementing an Integrated Pest Management (IPM) research program through the NESP Tropical Water Quality Hub, bringing what’s been learned from successful pest control strategies on land into the marine realm for the first time. Close links between research, management and on-water control operations on the GBR have enabled us to make great strides in efficiency and effectiveness.”
Sheriden will speak on Monday 16th July at 14.45 pm in the Urchins Ballroom.
Dr David Westcott from CSIRO leads the Hub’s IPM research effort. “The key objective for the Hub’s COTS program has been to work with researchers and managers to develop a management strategy that reflects the realities of both the ecology of COTS outbreaks and of the control capabilities,” he said.
“A first pass at this was an early product of the research and over the last two years, we have been refining that strategy to reflect changes in our understanding and our control capacity.
“At the Symposium I will provide an overview of that journey, the current management strategy, future research directions and how we are ensuring our research is providing real assistance to managers in meeting their objectives.”
“A central question is whether COTS control is effective in reducing COTS numbers and their impact on reefs,” said Dr Westcott. “Come along to the session to find out!”
David will speak on Tuesday 17th July at 9.15 am in the Urchins Ballroom.
Other speakers in the sessions will present on the tools being developed to assist managers in decision making, and gap-filling studies of COTS that are being conducted through the Hub’s research program, some of which are highlighted below.
The proceedings of these special COTS sessions will be published as a peer-reviewed NESP TWQ technical report that will be freely available to all.
What’s eating COTS?
The loss of natural predators of COTS is suspected to be one of the primary causes of their massive population outbreaks. Knowing which species of fish eat lots of larval, juvenile and adult COTS could be an important piece of the puzzle when it comes to controlling numbers of the coral-eating starfish. Dr Frederieke Kroon and her team at AIMS has been using environmental DNA (eDNA) technology to detect COTS predators in the Great Barrier Reef. They have developed a specific DNA probe designed to reveal the presence of COTS DNA in samples such as fish poo.
“The eDNA approach allows us to identify fish species that may eat COTS, using non-invasive and non-lethal methods,” Dr Kroon said. She and her team collect fish from the reef, keep them overnight on-board the AIMS research vessel, and collect their poo the next morning before releasing the fish back onto the reef. The poo samples are then taken back to the AIMS laboratory for further DNA analyses. So far, the project has collected and analysed close to 500 fish poo samples, and confirmed COTS DNA in poo from six species of plankton-eating damselfish. Dr Kroon and her team will be conducting another field trip in the weeks prior to the Symposium to target fish species that may eat juvenile and adult COTS. “We will be looking at species like emperors, wrasses, and pufferfish,” Dr Kroon said.
Come along to her presentation on Tuesday 17th July at 11.45 am to hear the latest findings.
Monitoring COTS recruitment: early warning of an outbreak?
In another component of NESP TWQ’s integrated portfolio of COTS research, Prof Morgan Pratchett at James Cook University has been working on an ‘early warning system’ for COTS recruitment that could drastically improve capacity to manage future outbreaks. He and his team are looking into the earliest phases of COTS recruitment (when planktonic larvae settle onto solid surfaces to begin growing into juveniles) and post-settlement movement capabilities.
They have been trialing the use of settlement traps – compact plastic cages filled with high-surface-area ‘bioballs’ designed to capture and recruit all manner of planktonic organisms from the surrounding water – for the detection of COTS larvae or juveniles. After being submerged on the Great Barrier Reef during the summer spawning period, the traps are retrieved and their contents are checked for COTS.
“Originally we were relying on visual identification of COTS in the mix retrieved from the bioballs, which was both very time-consuming and we had a lot of doubts about this method’s accuracy – it’s like searching for a needle in a haystack, there’s so much algae, sediment and other organisms in there to sort through,” Prof Pratchett said.
“But what we’ve been able to do now is leverage the work being done at AIMS on the genetic signal of COTS larvae. This enables us to get a much faster and more reliable picture of whether or not they’re present in a given sample.”
The project has already answered a major question in the field of COTS research, and further advances in the ‘genetic probe’ technology are expected to shed even more light on early COTS behaviour.
“There is a hypothesis that COTS are only being recruited from deeper in the water column. However, what we’ve learned from using these devices is that they are being recruited in both deep and shallow water on the Reef,” Prof Pratchett said.
“At the moment we can provide semi-quantitative data by comparing the proportion of settlement devices in which we find COTS to the proportion in which we don’t. In the future we will be able to tell the proportion of COTS genetic material within each device. This will add a whole extra layer of information to what we know about COTS recruitment, which will in turn enable us to guide control efforts that much more effectively.
“When you pair that up with our other NESP TWQ-funded research projects on the movement rates of adult COTS across the seafloor, we are already getting a fairly good indication that when COTS recruit at a reef they tend to stay there. This means that we could concentrate control effort on that reef once we know there’s likely to be an outbreak there.”
Morgan will be speaking at on Tuesday 17th July at 11.15 am in the Urchins Ballroom.
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