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Electrically charged frames
are being used
Sean Hargrave ELECTRICITY is coming to the rescue of coral reefs. A novel idea of using an electric charge to build new reefs and help dying coral recover is being tested in the Maldives. But the technology could be used first 1,000 miles to the west in the Seychelles, where the government has applied to the World Bank for funds to pay for it. One in three fish lives on a coral reef, yet global warming and pollution is killing coral. As much as half of the world's coral may be dead or dying. A rise of just one degree Celsius above average temperatures is enough to kill a reef. The new approach relies on elementary chemistry. First scientists place a steel frame in the sea and pass an electric charge of one or two volts through it. The steel then carries a charge and has positive and negative terminals, just like a battery. The cathode terminal, which forms the bulk of the construction, makes the water around it slightly more alkaline. The anode makes the water slightly acidic but it is placed a couple of metres away from the main steel frame. Making the water around the frame more alkaline causes calcium carbonate particles in the sea to settle and form a limestone base. This is the perfect home for coral, which thrives on clean, fresh limestone. Tom Goreau of the Global Coral Reef Alliance (37 Pleasant Street, Cambridge MA 02139, USA) says the system brings an extra benefit to the coral. Usually much of the coral's energy goes into creating a slightly alkaline stream of water so it can feed. "We are effectively giving coral exactly what it wants, for free," he says. "We give it a good clean base to settle on and make sure it doesn't expend its energy turning the water alkaline. It's a really good environment to create growth, and it's based on giving a helping hand to a natural principle. "I cannot see that anybody can come up with a better solution because all other attempts rely on creating reefs out of rubber tires or old bricks, but coral doesn't chose to live there. We are creating exactly the conditions coral needs." The limestone that forms the reef can be grown at a rate of between 1cm and 2cm a year. The voltage can be altered to speed up growth but this results in limestone that is too soft. Scientists using the technique in the Maldives have found it can promote coral growth of several centimetres a year once coral settles on the artificially created reef. The new technology is needed, says the GCRA, because there will hardly be any live coral left if something is not done to redress the damage caused by pollution and global warming. "If half the world's trees were disappearing there would be an uproar, but this is happening under water and so people aren't seeing it," says Goreau. "We have to act now to give a helping hand. Remember, once the reefs are gone many islands that are already suffering from erosion are going to be unprotected against the power of the sea. People forget that apart from playing home to one in four marine species, coral reefs also hold back the sea and protect islands. Without them island communities would be devastated." The original idea for the electric process came from a German architect, Wolf Hilbertz. He developed the idea so that limestone building materials could be made within steel meshes placed in the sea. This would provide a free source of materials and stop islanders raiding reefs for stone to build houses. Now that Goreau's team has proven the principle also works in creating and sustaining coral reefs, work with solar and turbine power has begun. These sustainable sources are preferred because they do not add to the pollution or global warming that are being blamed for the demise of coral. Goreau is encouraged by the Seychelles government's interest in the technology. However, the government of the Maldives, where nearly all the development work has taken place, has no plans to adopt it even though the island group has been hit more than any other by the death of coral. |
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