BioEd Online

An artificial reef made from tyres dumped off the coast of Florida is being dismantled, after the tyres broke their moorings and damaged natural reef in the ocean.

The reef was made in the 1970s, when an estimated 2 million tyres were chained to the seabed across 34 acres off the coast near Fort Lauderdale. But a reef never formed, and the clips holding the tyres together rusted and loosened, setting the tyres rolling towards the natural reef.

"As time went on the tyre pile turned into a coral killing machine," says William Nuckols, the US government's project coordinator for the clean-up project, based at Coastal America, Washington DC.

Throughout June, divers from the US Army, Navy and Coast Guard set about salvaging some of the tyres in a pilot project for a full-blown tyre-removal programme beginning in 2008. The military divers pulled out 10,373 tyres, and aim to remove many more over the next three years.

Tiring work

The original goal was to get rid of some 700,000 tyres, but that now looks unlikely says Ken Banks from the Broward County Environmental Protection Department, which is leading the clean-up operation.

"We won't be able to get rid of them all," says Banks. Effort will focus on the rogue tyres that are causing the damage, he adds. Many tyres are in an area that seems to be stable, so they will be left. The amount of damage caused will never be known, says Nuckols, because no surveys were conducted before the reef was built.

Following the pilot study, Banks estimates that up to 1,400 tyres a day could be removed when the full project starts next May. He hopes that the salvage efforts will last for at least 90 days in each of the three years they have funding for. The tyres collected so far have been chipped and burned as fuel.

Better engineering

This one failure shouldn't mean the end of tyre reefs, says marine researcher Antony Jensen from the University of Southampton, UK. The problem is one of poor engineering, rather than a flawed concept.

"If you're going to place tyres in the sea they have to be extremely well engineered, they have to be well attached to the seabed," he says. The chains used in the 1970s were inadequate, but that is no longer a problem. "We can use nylon ties not available 40 years ago," Jensen says, and these attachments don't corrode like the older anchoring methods.

But other reef conservation scientists would scrap the use of tyres. "Tyres are not ideal," says Alison Moulding at the National Coral Reef Institute based at Nova Southeastern University Oceanographic Center in Dania Beach, Florida. "The original concept was a way to dispose of tyres — it didn't work," she says. Florida has banned the use of tyres to build reefs.

Artificial reefs are widely used to replace natural reef, or to create a new habitat for marine life. In Japan, artificial reefs are used extensively to attract fish for human consumption. In Florida the idea is to reduce pressure on the natural reef from divers, says Banks. The tyre-damaged reef will take decades to recover, he says.

Jensen says that to prevent problems like those seen off the coast of Florida, more engineers need to enter the marine science community. "If tyres are going to be used we need to put a lot more emphasis on the engineering, and on balancing the wave energy and tidal currents that can impact on that engineering," he says.