In 2014, as part of their 50th Anniversary Commemorative Giving Program, The Ian Potter Foundation awarded a $500,000 grant to The Lizard Island Reef Research Foundation. The purpose of this grant was to investigate ways to help control outbreaks of Crown-of-Thorns Starfish (COTS) or lessen their severity or frequency. Twenty research projects were supported resulting in twenty-seven scientific publications to date

In the summary below, Dr Lyle Vail (LIRS Co-Director) highlights some important outcomes that have flowed from research supported by these grants.

Vinegar – a huge increase in productivity for the culling of COTS

The discovery that using vinegar delivered with a fine point needle to inject COTS has been hugely successful in increasing the efficiency of divers in controlling COTS numbers. Previously, sodium bisulphate was used to control COTS. However, to kill a COTS using this chemical they needed to be removed from the reef matrix in order to be effectively injected 10 – 25 times around the perimeter of their disc, with the number of injections depending on body size. This is a time consuming and thus inefficient process, especially when protecting an area with hundreds or thousands of COTS. When using vinegar, a COTS can be killed by injecting them in-situ because only 1-2 injections are required anywhere in the disc, thus enabling a diver to kill many more animals per dive.

Vinegar injections are used to kill Crown-of-Thorns Starfish. Photo: Lyle Vail.

Using vinegar to control COTS is one of only three chemicals approved by the Great Barrier Reef Marine Park Authority (see GBRMPA COTS Control Guidelines) for this purpose. It is used by many of the government funded COTS control vessels, whose purpose is to protect reefs from outbreaks of COTS, since it is the most cost-effective and easy to work with of the three chemicals. There is now good evidence that we can contain (or even prevent) outbreaks at individual reefs with concerted culling effort and thereby protect coral. The ability to protect reefs in this manner is a significant development for the Queensland tourism industry. However, the potential to suppress or contain outbreaks at regional or reef-wide scales still needs work. The research on using vinegar and a fine point needle to cull COTS was done by Dr Lisa

Bostrum-Einarsson (James Cook University) under a grant awarded in 2015.

 

 

The life-cycle of COTS

To be able to control or regulate COTS outbreaks, we need to understand every stage of their life-cycle.  Numerous targeted grants were made and resulted in extensive new knowledge about COTS. This information is included in the 27 peer-reviewed papers that have been published to date and it will continue to be a valuable resource for researchers and marine managers.  More papers from this research will be published in the future.

Researchers dissecting COTS to determine spawning condition. Photo: Lyle Vail.

Lessen the severity or frequency of future outbreaks

Early intervention during the initiation of new population irruptions of COTS represents our best opportunity to effectively manage this threat. However, prior to research done pursuant to this grant, survey methods were not sufficiently sensitive to detect changes in COTS densities during the early onset of population irruptions. Consequently, in the past, outbreaks of COTS were well established and large numbers of COTS were eating coral before resources could be garnered to commence controlling them, typically by lethal injection.

The Foundation’s Science Committee awarded a number of grants to develop improved technological and survey methods and we are now in a better position to detect the early stages of an outbreak.

We can now use eDNA to detect the presence of COTS in an area from water samples, even when they are at low densities. This important advancement was undertaken by Dr Sven Uthicke and Jason Doyle (Australian Institute of Marine Science) with grants awarded in 2016, 2018 and 2019. A detailed summary of results from this work was published in August 2022 and is available here.

Grants awarded during the last few years of the granting period (2019 and 2020) resulted in a new and more effective technique to survey COTS numbers. Professor Morgan Pratchett (James Cook University) and colleagues devised a method to survey COTS using underwater scooters – termed SALAD for Scooter Assisted Large Area Diver-based visual surveys. The technique is ground-breaking because, unlike most other survey techniques (e.g., manta tows), it can detect populations of COTS in the early stages of an outbreak. The significance of this technique lies in the large area that can be surveyed effectively: it allows divers to survey up to 11,000 m2 of reef area in each dive. Juvenile COTS are small and often hiding under corals. This technique allows divers to search for these small animals carefully, and the result is a much better quantification of the presence of COTS. An overview of results from surveys at Lizard Island from 2019 – 2022 was recently published (November 7, 2023) and is available here. This work provides strong evidence that the anticipated fifth population irruption of COTS since the 1960s has already commenced in the northern GBR.  The information from these surveys has been communicated to the Great Barrier Reef Marine Park Authority. Appropriate resources are now needed to tackle the outbreak at an early stage by culling the juveniles.

 

A Crown-of-Thorns Starfish eating coral.