Great Barrier Reef: the coral-eating starfish may also support diversity
· BehindLines newsroom
The crown-of-thorns starfish has a reputation as a reef destroyer. A University of Sydney study, published in late September and relayed by ScienceDaily on 1 November, qualifies that picture: at low densities, the animal might help maintain coral diversity on the Great Barrier Reef. The authors stress, however, the limits of this result.
A field study on a protected reef
According to the University of Sydney release, dated 24 September 2026, the work appeared in the journal Ecology and Evolution (2026, volume 16, issue 9). It is led by Dr Shawna Foo of the School of Life and Environmental Sciences. The researchers examined the scars the starfish leave on colonies, and the coral tissue that stayed alive, at the university's One Tree Island Research Station. The sites studied lie in protected areas where healthy fish populations keep starfish numbers in check.
What the observations show
The university says living tissue remained after nearly 75% of the feeding events observed. At One Tree Reef, Dr Foo says, the animal appears to eat a fairly consistent amount of coral at each meal and then move on, rather than destroying whole colonies.
Recovery observed over 22 weeks differed by coral genus. Surviving fragments of Acropora, a fast-growing coral, did not regrow over the damaged areas. Regrowth was observed in the slower-growing Montipora and Porites corals. Because the starfish readily attacks fast-growing corals, a small number of them could stop those corals from taking over all the space and leave room for slower species. Professor Maria Byrne, a co-author, considers the results consistent with the intermediate disturbance hypothesis, under which a moderate disturbance prevents any one species from dominating and supports biodiversity.
Outbreaks remain devastating
The context is still worrying. The Great Barrier Reef has seen four major starfish outbreaks since the 1960s, roughly one every fifteen years. The university adds that the decline of natural predators, including tritons (large predatory sea snails) and several reef fish, leaves the system more vulnerable.
The authors point out that their observations do not downplay the damage caused by outbreaks, from which corals struggle to recover. The work was mostly done in areas with little exposure to such episodes, which limits its reach. Dr Foo stresses the need to distinguish populations performing their natural role as predators from outbreaks that cause lasting reef decline.
Possible consequences for management
In the researchers' view, the results could inform when and why culling campaigns are carried out. Once an outbreak is under control, the goal would not necessarily be to remove the starfish entirely. Culling should be paired with strong marine management that protects its predators. This is a study of a single reef: it calls for caution rather than a change of strategy across the whole Great Barrier Reef.
Note on sources: ScienceDaily, the press release and the research paper concern the same study. For management context, the Reef Authority describes control targeting densities compatible with coral growth; this is not a replication of the study.