THE submersible Alvin encountered its first “black smoker” 2000 metres deep off the coast of the Galapagos Islands. It was 1977, and the realisation that life could survive in pitch darkness next to deep sea hydrothermal vents was about to stun the world. Now we are returning to those vents, this time on the other side of the Pacific – and armed with diggers.
The hot water shooting out of these vents contains all sorts of dissolved precious metals. On contact with the cold ocean water, these immediately precipitate out, showering the vicinity with gold, silver, copper and more (see diagram). Some want to tap into this booty, arguing that deep sea mining is not only lucrative, but also a more sustainable alternative to mineral extraction on land. But not everyone is convinced we can exploit the deep without damaging it.
Soon such debates could become very real. Since 2009, Canadian company has held a licence from Papua New Guinea to mine in its waters, targeting a massive sulphide deposit. Such deposits are distributed around the globe, principally along the active margins of tectonic plates (see map below). This one, named Solwara 1, lies 1600 metres down and is around 7 per cent copper, 10 times what is typical for mines on land. There’s gold too: about 6 grams per tonne of rock, six times what landlubbers get. “These are grades that haven’t been seen on land for 300 to 400 years, since the start of the industrial revolution,” says Nautilus CEO Mike Johnston.
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I like to be under the sea
The Axial seamount volcano (see main story) is not the only place we’ve wired up to investigate the deep ocean. Numbers refer to the map below.
1 Axial seamount, north-west Pacific
2 Juan de Fuca plate boundary, north-east Pacific. The US Ocean Observatories Initiative (OOI) and Ocean Networks Canada have wired up sensor arrays as far down as 3000 metres to monitor the sea floor and water column.
3 Off Martha’s Vineyard, Cape Cod, north Atlantic. The OOI Pioneer array studies the interplay of nutrients, pollutants and currents at the boundary of the deep ocean and the shallower continental shelf. In February this year, it measured the transfer of momentum, heat and moisture between the sea and atmosphere during a hurricane.
4+5 Off the Chilean and Argentinian coasts. Further OOI deep ocean arrays,
6 Marianas trench, north Pacific. From April to July this year the US NOAA research ship Okeanos Explorer sent rovers to explore the deepest part of the ocean, 11,000 metres down.
7 Off the south coast of Japan, north Pacific. Some 320 kilometres of cables connect seismometers of the DONET array (Dense Oceanfloor Network System for Earthquakes and Tsunamis).
8 South China Sea. China has recently confirmed plans for a crewed “space station” 3000 metres down.
The plan is for two enormous underwater tractors to grind up the mineral-rich rock near the vents. A third will collect the rubble and deliver it to a sea floor pumping station that will send it up to a ship, ultimately to be processed in China. Because the deposits sit directly on the seabed no tunnelling is needed, and the site’s footprint is relatively small, making for cleaner extraction, says Johnston.
“To get to gold on land sometimes you take the top off a whole mountain“
Marine economist at the European Institute for Marine Studies in Brest, France, says there could be something to that argument. “To get to gold on land sometimes you have to take off the top of an entire mountain,” he says. But he points out that undersea mining will always add emissions and environmental damage unless it replaces mining on land.
How much damage is moot. Nautilus’s plans stalled in 2014 when it got into a row over funding with the government of Papua New Guinea, which holds a stake in the firm. By then, questions had been raised about the company’s . A 2012 report commissioned by an anti-mining group and prepared by John Luick at the South Australian Research and Development Institute in Adelaide argued that it , so it wasn’t clear whether any stirred-up sediments would pollute coastal areas of Papua New Guinea.
The funding worries have not completely evaporated, but Nautilus has tried to dispel some of the environmental concerns by commissioning a of the proposed Solwara 1 mine and three terrestrial copper mines. In 2015, this concluded that Solwara 1 would be less damaging to the environment. Another study, commissioned by the development organisation Pacific Community, found that deep sea mining was likely to and the Cook Islands – Nautilus is exploring mining sites near there, too.
The firm is now hoping to begin operations in 2018, and it is conducting shallow water tests of its tractors in Oman. But Stace Beaulieu, an oceanographer who studies hydrothermal vents at the Woods Hole Oceanographic Institution in Massachusetts, has some reservations about the reports. “The work is quite good. It accounts for the sea floor and the water column, but without peer review we can’t really say whether this is less damaging than land mining,” she says.
One risk is that pumping rocks to the surface might transfer cold, nutrient-rich water too. If this were to mix with surface water, it could cause algal blooms. Johnston says the pumping system has been carefully designed to ensure there will be no such mixing. Another possibility is that disturbed sediments could travel long distances and affect ecosystems far from the mining site itself. Beaulieu thinks that could be tough for filter-feeders including fish and sea anenomes. “They’re just not adapted to high sedimentation.”
The rich ecosystems in the immediate vicinity of the vents will probably be destroyed. Most of the organisms here grow rapidly – giant tube worms, for example, are the fastest-growing marine invertebrate, able to colonise a new location as juveniles and reach sexual maturity within two years. A study of a big undersea volcanic eruption with vents nearby showed that life can start to . Even so, that was a natural process, and we don’t know what will happen if mining removes the seabed. “It might take time for the habitat to return to the point where the animals are able to come back,” says Beaulieu. Nautilus is surveying the area around Solwara 1 to make sure there are communities nearby to provide new colonists.
Given our lack of knowledge about sea floor mining, some would like to see a moratorium on it. Namibia has already banned coastal phosphate mining in its waters. But many hydrothermal vents are located in international waters, along ocean plate boundaries. Who is responsible then?
The UN Convention on the Law of the Sea designates the seabed beyond national maritime boundaries as the common heritage of humanity. In these regions – known somewhat strangely as “the Area” – the job of deciding who can mine what and where, and how the environment should be protected, falls to a UN agency called the (ISA). It is developing rules to allow all nations to share the potential benefits of seabed exploitation, and put in place strong environmental safeguards.
, a high seas adviser to the International Union for Conservation of Nature, says that the ISA is behind the times. Although several companies are gearing up to work in the Area, “the ISA hasn’t adopted its exploitation rules yet, so it has no way to enforce them at present”. Gjerde also reckons that the agency’s decision-making structures are dominated by industry players, which creates conflicts of interest. “The ISA is on a precipice: either reforming itself and becoming an effective organisation, or allowing commercial interests to dominate,” she says.
One decision the ISA needs to make is how to spend any royalties it can collect from mining in the high seas. Divvying up the money among all nations will mean paltry sums for each, so Johnston and Pendleton both advocate investing the proceeds in ocean research and environmental clean-up. “We have already done so much damage to the sea floor, for example through trawling, with no way to pay for it,” says Pendleton. Perhaps at the very least the wealth of the seabed could help heal those scars.
Pretty destructive
Hydrothermal vents produce dustings of valuable metals on the sea floor, but rich pickings can be found elsewhere too. Metals can also crystallise out of seawater to form so-called polymetallic nodules. These grow incredibly slowly – at a rate of about 1 centimetre over several million years – and can reach the size of a potato.
Mining them might be pretty easy, says Phil Weaver, who coordinates the European Union’s on the impacts of deep-sea mining. “You just have to rake through the sediment and sift out the nodules, then crush them.” But the nodules are small and thinly dispersed, so collecting a profitable amount would involve destructive dredging.
Then there is the question of pumping the nodules to the surface. The nodules lie at 6000 metres, that is twice as far down as today’s deep sea mining projects, placing a huge burden on equipment. “It’s a completely new challenge,” says Weaver.
Read more in our ocean special: “High tech goes deep: A new age of ocean exploration”
This article appeared in print under the headline “Sunken treasure”
Article amended on 19 August 2016
Correction: we noted the actual location of the Juan de Fuca tectonic plate
