Could electric biorocks save coral reefs?

By Katie SilverFeatures correspondent

In Indonesia, ecologists have created ‘biological rocks’ on the ocean floor using an ingeniously simple technology. Katie Silver investigates.

Just metres off the beach, beneath the clear water, is a giant motorbike, sitting atop a big steel structure in the shape of a speedbump. It is covered in coral, and tropical fish dart under the handlebars and between the spokes of the wheels.

The structure isn’t an art installation, however; their frames tingle with electrical currents, which helps them create a rocky coating – which in turn becomes a nursery for coral reefs that have been damaged by human activity.

These electrically charged shapes are in Gili Trawangan, one of three small islands northwest of Lombok in the Indonesian archipelago. A tourism industry has sprung up here in record time. With it, a small group of expat environmental activists have clubbed together to create the steel structures submerged in the nearby waters, and shown how a smart technology may help this developing nation safeguard some of its natural wonders.

The ‘Gilis’, as they’re known, were a destination previously off-the-beaten-track; that’s no longer the case. On Gili T’s main street, tourists sip soy lattes and munch on superfoods in air-conditioned cafes as the Islamic call to prayer sings out as background noise. Swedish and Australian tourists bike around the three-kilometre-long island, past locals in pony-drawn carts and hijabs. 

“I was really quite amazed and surprised to see the results of the technology,” says Delphine Robbe, the manager of Gili Eco Trust. Originally from France, Robbe moved to the island as a dive instructor in the early 2000s. She started the biorock project a decade ago, funding it originally through her own salary. There are now 111 of them across the three islands, each costing around £1,500 ($2,270)

Biorock technology was originally developed by marine scientists Thomas Goreau and Wolf Hilbertz. A low-voltage direct current is run through the steel. This electricity interacts with the minerals in the seawater and causes solid limestone to grow on the structure. It draws on the principles of electrolysis, where the electric current causes a chemical reaction to occur which wouldn’t have otherwise. 

Healing space

Eventually, the limestone solidifies. “It’s the same thing that makes up [marine] skeletons,” says Robbe. And it’s a perfect breeding ground for aquatic life. 

“It’s speeding up the normal reaction of coral growth. Corals on the biorocks survive more than any other.”

When divers see injured coral, they move it to one of these structures to rehabilitate. The coral heals some 20 times faster, and has up to 50 times more chance of survival. The rehabilitated coral can often be astoundingly brilliant in colour and densely branched. Once healed, it is returned to the open sea. 

“Just observing the reef and hoping it will recover is pointless – it doesn’t work,” says Robbe. 

She says there are coral rubbles lying on the seabed that, with strong storms and waves, are constantly being shifted about, making their regeneration impossible. 

The behaviour of locals and tourists don’t help either. The use of heavy nets and even dynamite by fishermen, dragging anchors, and divers and tourists touching or walking on the reef all cause damage. “These are all forbidden in the Indonesian lawbook but there’s no control,” she says. 

Protecting effect

The biorocks – shaped like giant steel manta rays, pyramids, planes, dolphins, whale sharks, lizards and turtles – are helping to stave off these adverse effects. 

And it’s not just coral that improves: the biorocks have helped the fish populations as well, particularly lobsters and juvenile fish who shelter in the structures. “Now we have more biodiversity and the water quality is better,” she says. They have also helped turn the tide when it comes to severely eroding beaches. Slowing the onslaught of fast waves, biorocks lead sand to be deposited, rather than eroded, at the shoreline. This has seen certain parts of the beach grow some 15 metres in a few years. 

And, they’ve proven themselves resistant to damage from natural disasters, such as the Asian Tsunami of 2004, as their open frameworks allow large waves to pass through. 

While there is no limit to the size or shape of the structures – they could be hundreds of miles long if funding allowed – there is a limit when it comes to powering them. 

“You can’t have them way out to sea because you need electricity,” says Robbe.

And in a developing country like Indonesia, electricity means oil. It’s a vicious circle environmentally.

The team has experimented with powering biorocks using solar energy from a solar panel on a barge above the structure. The only problem? The panels are often stolen.

Tidal energy

Now they’re looking to harness the energy of the marine currents. “The marine turbine acts like a wind turbine but underwater,” says Robbe. Operating in a cylinder, there are three blades that spin with the current with a generator on the top. As the biorock doesn’t need a constant energy supply, the tidal waves would provide enough power.

The team has been trying to fund the project for the last four years. Not only is the technology very expensive, but importing it attracts huge taxes. As a result, they’re now trying to produce it locally. Their first prototype wasn’t quite right – the fan rotated too slowly – but they’re working with engineers on a new one. If it’s successful, Robbe imagines wind-turbine-powered biorocks could be replicated around the world. 

What’s more, she hopes the project could serve to show Indonesia that they could use tidal energy, rather than oil, to produce the country’s electricity. 

“Tidal power has great potential for future power and electricity generation especially in Indonesia which would be able to use its main wealth, the ocean,” writes Robbe on her blog. 

The simple structures currently doing their coral-conserving work in the warm offshore waters may turn out to have some far-reaching effects.

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