Researchers have made a killer discovery that could protect the Great Barrier Reef's most valuable coral sites from the destructive crown of thorns starfish.
A harmless protein mixture, used to grow bacteria in science labs, has been found to destroy the starfish in as little as 24 hours.
The breakthrough comes as new starfish outbreaks hit parts of the Great Barrier Reef and reef systems across the Asia Pacific.
The next step will be tests to show the protein is safe for other marine life, say researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University.
If there are no adverse effects, the discovery will provide a far more efficient tool to control outbreaks at sites critical for conservation and tourism.
"A crown of thorns outbreak can destroy from 40 to 90 per cent of the corals on a reef and over the past 50 years it has caused more damage than bleaching," researcher Dr Jairo Rivera Posada said in a statement on Monday.
"There were massive outbreaks in many countries in the 1960s and 1980s and a new one is well underway on the Great Barrier Reef."
The lightbulb moment came when Dr Posada was on a beach with colleague Professor Morgan Pratchett at Lizard Island in the northern Great Barrier Reef.
Dr Posada wondered if the substance he was using in the lab to culture the Vibrio bacteria that naturally inhabit the starfish could give the bugs enough of a boost to damage their host.
The researchers rushed back to their tanks and injected five starfish with the media culture solution and were astonished when the starfish rapidly began to fall apart and die as the bacteria attacked them.
The solution had caused the bacteria to bloom and attack the starfish.
At the same time, the starfish suffered an acute allergic reaction to the unfamiliar animal proteins - derived mainly from cattle - used in the culture.
The bacteria also spreads under favourable conditions to other starfish that come near or into contact with an infected individual.
Extensive tank testing was needed before sea trials of the compound could be considered.
Currently starfish outbreaks at high-value sites are controlled by divers who inject them with poison.
The new discovery offered hope of a much more effective and efficient method, Prof Pratchett said.
"The protein solution needs only a single jab into a starfish, enabling a diver to kill as many as 500 crown of thorns in a single dive compared with 40 or so using the poison injection," Dr Posada said.
But the discovery is not a silver bullet for the mass outbreaks currently being seen.
"In the Philippines they removed as many as 87,000 starfish from a single beach. This gives you an idea of the numbers we have to deal with," Dr Posada said.
"Any attempts to control these outbreaks will be futile without also addressing the root cause of outbreaks, including loss of starfish predators as well as increased nutrients that provide food for larval starfishes."