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Electrified cages jolt coral reef survival

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Metallic structures with a low level electric current provoke limestone formations that attract coral growth. The technology is proving effective at restoring reefs around the world, including Bali.

A low-level electric current running through domed-shaped metallic structures in the waters off Bali is giving a jolt to coral reef survival there, according to news reports.

The Biorock technology is seen by some conservationists as a means to repair coral reefs damaged by years of destructive cyanide and dynamite fishing practices, as well as steadily warming oceans.


Warming oceans are a threat to the reefs since they result in more frequent episodes of coral bleaching, a phenomenon when higher temperatures cause photosynthetic algae that provide corals with food and color to leave, turning the corals white.

Without food for a sustained period of time, the corals will die. A coral bleaching event in 1998 killed one sixth of the world's tropical reefs

Biorock technology builds from the late German marine architect Wolf Hibertz's discovery in the 1970s that electrified metallic structures cause dissolved minerals in the water to crystallize on them.

This grows "into a white limestone similar to that which naturally makes up coral reefs and tropical white sand beaches," the Global Coral Reef Alliance explains.  

Marine life including corals and oysters colonize this limestone.

"Corals grow two to six times faster. We are able to grow back reefs in a few years," Thomas J. Goreau, a marine biologist who is leading the development of the technology, told AFP.

Goreau is president of the Global Coral Reef Alliance, a U.S.-based non-profit dedicated to the protection, preservation, and sustainable management of coral reefs. 

Bali success
The alliance today works with organizations around the world to implement the Biorock technology, including a 20-year-long project in Pemuteran Bay off the north coast of Bali.

Today there are about 60 of the electrified metallic cages in the bay, creating a coral reef there that is "flourishing better than ever before," AFP reports.

What's more, researchers overseeing the project say that the Biorock technology makes the corals more resistant to global warming.

"Biorock is the only method known that protects corals from dying from high temperatures. We get from 16 to 50 times higher survival of corals from severe bleaching," Goreau told AFP.

These restored reefs in turn attract fish and tourists.

Technology limits?
While the technology is useful for small areas, the scale of coral bleaching is just too large for it to be a cost-effective solution, Rod Salm, a coral reef specialist with The Nature Conservancy, told the Associated Press in a 2007 story about Biorock technology.

A more effective method of saving reefs from mass coral bleaching may be large marine protected areas that offer plenty of shade and cooler waters for the reefs, Salm noted in a 2010 blog post for Nature.

But at the small scale, at least, Goreau argues that Biorock is more cost-effective than other solutions. For example, the National Oceanic and Atmospheric Administration recently touted the successful recovery of 376 square feet of coral in Florida that was damaged when a boat ran aground in 2002. 

With $56,671 in settlement funds, the government agency attached corals to a special cement that hardens underwater. By 2010, the restored reef was healthier than an adjacent undamaged section.

Goreau issued a press release countering the agency's success story saying that his Biorock technology is more cost effective. Based on the settlement funds used for the restoration, the government project cost $1,622 per square foot. Biorock technology can be used to grow six foot tall reef structures for $13 to $20 per square foot, he claims.

The technology will be featured in One Day on Earth, a television program sponsored by the United Nations, in early 2012. You can check it out in the video below.

More on coral reef damage and restoration:


John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

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