It's a deadly predator, but not one you would expect. One particular type of starfish that serves as one of the greatest hazards to our coral reef. Known as the crown of thorns starfish, it's an organism not only poisonous to humans, but deadly to the coral reef.

"It's very present on Guam," said University of Guam associate professor of marine biology Dr. Terry Donaldson. "It appears here on a regular basis but there are occasions when they have population explosions." Dr. Donaldson, says population explosions of the coral-eating starfish Acanthaster Planci can harm the reef's growth. He said back in the 1960s, concern over this particular starfish led to thousands of dollars worth of research funding that ultimately aided in the establishment of the University of Guam Marine Laboratory.

"It's a big problem here, it's a big problem in Australia, it's a big problem pretty much wherever this species is found," he said.

In fact, a single outbreak of crown of thorn starfish could consume up to ninety percent of the coral reef it settles in. Frequency of outbreaks have increased over the past few decades, and the pressure it puts on coral reefs is so great, that predictions show without it, the declining coral-cover curve would actually be positive instead of negative. "We don't just want to go out and start killing these starfish, they are part of our coral reef community. What you want to do is if they have a population explosion, try to control their numbers," said Dr. Thompson.

Previous attempts to control the population using noxious injections were either too expensive, or too harmful to the reef. But a new discovery shows citric acid injections may be the solution. "It's interesting because these are natural products that they're using, they utilize citric acid in the lime juice to essentially poison the starfish," he said of the creature's M.O.

Not only does lime juice kill the starfish immediately, but it is readily available, inexpensive, and has negligible effects on the coral reef. "Previously they've used things like formaldehyde or formalin, or certain other chemical substances that have had a negative effect upon the reef," he said.

The discovery was made through collaboration between scientists in Vanuatu. The first field trials began last year and have proved successful, leaving the island of Emao Acanthaster-free.

Dr. Donaldson said the discovery also has applications for Guam.