Interactive graphic: Deep sea gold rush: World’s hydrothermal vent fields
Editorial: “New dawn for mining at the seabed“
As mining companies prepare to exploit the copper and gold in the seabed, we explore the fate of the unique ecosystems around tectonic boundaries
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SOME 1600 metres below the waves, a 150-tonne tank-like vehicle wields a robotic arm armed with rotating rock cutters. After it has ground down the volcanic chimneys that rise from the sea floor, other mining robots follow in its tracks. One chews up the levelled seabed, composed of ores of copper and gold; another acts like a giant vacuum cleaner, gathering the finely ground rubble so that it can be pumped to a ship at the surface.
If all goes to plan, this is the scene that will play out in late 2013 at a site called , off the coast of Papua New Guinea (see interactive map). According to of Vancouver, Canada, the company behind the scheme, the rich mineral deposits that form at marine hydrothermal vents – volcanic systems that spew scalding sulphurous water into the ocean – are the next frontier of mining. As well as exploiting other sites in Papua New Guinea’s waters, the company intends to mine vents off Tonga, Fiji, Vanuatu and New Zealand.
The industry, if it takes off, is unlikely to be restricted to national – the regions that stretch up to 200 nautical miles (370 kilometres) seaward of each country’s coast, over which it has rights to use the marine resources. Some of the biggest known hydrothermal vent fields, which cluster along tectonic plate boundaries, lie in international waters, and exploiting these fields is legally complicated. Next week, the Legal and Technical Commission of the (ISA), based in Kingston, Jamaica, will review for 15-year exploration contracts to begin prospecting at sites on the Southwest Indian ridge and the Mid-Atlantic ridge, respectively. The age of mining at hydrothermal vents, it seems, is dawning.
Vent fields are attractive for mining because they contain high-grade metal ores. Deposits at Solwara 1, for instance, are thought to contain 6.8 per cent by weight of copper, compared with about 0.6 per cent typically found at mines on land. The deposits form when water that has percolated through rock beneath the sea floor, dissolving sulphur and metals, is ejected at temperatures of up to 350 °C into the frigid deep ocean. Black metal sulphides precipitate out, forming vent chimneys. As chimneys topple and reform, vent fields can develop into mounds of metal-rich ore.
The prospect of mining these deposits alarms many scientists who study vents and their creatures. A variety of worms, molluscs and crustaceans inhabit the vents – including such oddities as 2-metre-long giant tube worms () and the yeti crab (), named for its “hairy” legs and claws. What makes these ecosystems remarkable is that the entire food web depends on microbes that get their energy by oxidising hydrogen sulphide emitted from the vents – some of which live as symbionts inside larger organisms. This chemosynthesis is fundamentally different from the photosynthesis that sustains most life on Earth.
Since the first vents were seen in 1977, new animal species have been found at a rate of about one per month, with no sign of discovery rates falling off (see diagram). Given that vent ecology is still poorly understood, some researchers argue that it is too early to begin commercial exploitation. “We have really just scratched the surface of what lives in these areas,” says , a vent scientist at the Woods Hole Oceanographic Institution in Massachusetts. “You have the potential of wiping out a community that you don’t yet know exists.”
That won’t happen at Solwara 1, Nautilus officials insist. “The environmental impacts are going to be well managed,” says Joe Dowling, the company’s vice-president for communications. Indeed, Nautilus asserts that its activities at the relatively small Solwara 1, which spans just over 0.1 square kilometres – about the size of 10 football pitches – will be much less environmentally damaging than conventional mining, which typically occurs on a much larger scale.
Solwara 1 is a relatively quiet vent field that includes dormant chimneys and none of the gushing “black smokers” seen at the most spectacular vents. Still, chimneys venting hot water host vibrant populations of animals including snails and barnacles, which will be destroyed by mining. Nautilus is establishing a reserve site some 2.5 kilometres away, from which larvae should recolonise the mined area once operations cease, after 30 months or so. To minimise damage from mining spoil, particles larger than 8 micrometres across will be removed by the processing ship, before waste water is returned to the ocean, about 50 metres above the seabed.
As part of its evaluation, Nautilus commissioned independent scientists to survey both sites. They concluded that the reserve site was well chosen. “It is more diverse [than the area to be mined],” says marine ecologist of the National University of Ireland in Galway, a member of the team. “Mining may be an acceptable disturbance in the context of the natural variability and disturbed nature of these vent fields.”
“Mining may be an acceptable disturbance in the context of the natural variability of vent fields”
, Nautilus’s environmental manager, says the company will survey for recolonisation for at least three years after mining ceases and will monitor the effects of the fine sediment likely to fall on the seabed from the returning waste water.
Vent biologists contacted by żěè¶ĚĘÓƵ are generally impressed with Nautilus’s , but remain wary about the future if mining expands. “I’m concerned, and I’m paying attention,” says of Pennsylvania State University in University Park.
In March, the international body that coordinates vent science, , sent the ISA a list of vent fields that it suggested should be considered for protection from prospecting. This included almost half of the 72 known active vent fields in international waters, and was based on a poll of vent scientists, some of whom wanted to protect all active sites. These are easier to find because of their “smoky” plumes.
Earlier this year, of Duke University’s Marine Laboratory in Beaufort, North Carolina, who also worked on the site assessment for Nautilus, argued in Nature that mining and prospecting should be put on hold until firm guidelines for the conservation of vent ecosystems are in place ().
That’s unlikely to happen, but Adam Cook, a marine scientist with the ISA, says that the authority’s legal and technical experts will issue environmental guidelines at a later date. He also points out that the prospecting that will be allowed under the ISA’s exploration contracts is similar to the sampling already performed by vent researchers (see “Vent scientists clean up their act”). By the time mining takes off, if it does, guidelines should be in place.
For the foreseeable future, simple economics provides some reassurance that vents will not be trashed en masse. Perhaps 1 per cent of vent fields contain commercially viable mineral deposits, estimates , an economic geologist at the University of Ottawa in Canada. But if prices of copper and gold rise, the incentives will shift.
The fear is that without strong oversight, subsequent environmental assessments may not be as rigorous as that conducted for Solwara 1. Vent fields differ radically in the species present and possibly the extent to which the animals at a particular site embody unique genetic diversity. “Every one of these developments needs an appropriate assessment,” says Kennedy. “We shouldn’t allow a Wild West free-for-all after one or two studies.”
Vent scientists clean up their act
There’s an irony to calls from marine researchers to restrict mining at hydrothermal vents: until now, the greatest threat to these natural wonders has been overenthusiastic scientific research.
The alarm was sounded in 1990 by at the University of Victoria in British Columbia, Canada. She studied vent sites on the Juan de Fuca ridge in the north-east Pacific that had been visited by scientists at least three times in the 1980s. Populations of tube worms had plummeted at chimneys where sampling had taken place, but remained healthy at unsampled sites (Journal of Geophysical Research, ).
In some cases, even looking at vent animals can hurt them. In 1999, UK researchers found that the shrimp that congregate around vents on the Mid-Atlantic ridge had apparently been blinded by the powerful lights of submersibles that explored the vent fields (Nature, ).
Fortunately, subsequent monitoring indicates that shrimp populations are doing fine, says of the University of Southampton, UK. But it was another reminder that scientists needed to put their house in order. “The last thing we want to do is damage them by studying them,” Copley says.
Copley is co-chair of InterRidge, the international body set up to coordinate vent science, which in 2006 adopted a . It calls on scientists to avoid any activities that will undermine the sustainability of vent organism populations, refrain from all but essential collections and avoid transplanting material or creatures between sites. It also asks researchers to share samples and information to avoid duplication.
But the statement lacks the teeth of an earlier draft code of conduct, put forward by Lyle Glowka, a consultant who today is a legal adviser to the UN Convention on Biological Diversity, and marine ecologist of the University of Victoria. This would have asked national research agencies to make funding conditional on abiding by the code. “It fell flat on its face,” says Glowka. “I think it was seen as a threat.”
How closely scientists abide by the InterRidge statement is unclear. Earlier this year, Cindy Lee Van Dover of Duke University in North Carolina published a survey in which 90 per cent of researchers who responded said they followed the recommendations. However, half doubted whether their colleagues did – and only 5 per cent of more than 3000 scientists who were sent the questionnaire replied (Conservation Biology, ).
