Jul 8, 2021 - Science

The unknowns of deep-sea mining

Illustration of a deep-sea fish with a photo-luminescent antenna in the shape of a question mark

Illustration: Sarah Grillo/Axios

The prospect of mining the seafloor is prompting calls for more research about its potential impact on the ocean and sea life.

The big picture: Metal-rich mineral nodules on the ocean floor contain cobalt, nickel and other ingredients that power batteries, solar panels and other renewable energy technologies. But they also support unique organisms, and mining a habitat that scientists are just beginning to explore and understand carries risks.

What's happening: The Pacific island nation of Nauru last month triggered a clause in the UN Convention on the Law of the Sea, requiring the International Seabed Authority to finalize rules for mining the ocean floor within two years.

  • At that time, contracts to mine the seabed would proceed under the regulations put in place.

But some marine scientists and policy experts say the scientific research required to create regulations can't be done in two years.

Details: Polymetallic nodules resting 15,000 feet below sea level on the ocean floor are rich in cobalt, nickel, copper and manganese, which build up around fragments of shell and rock over millions of years.

  • About half of the seafloor biodiversity in the Clarion-Clipperton Zone (CCZ) of the North Pacific Ocean where mining exploration is focused is associated with nodules, says Lisa Levin, a biological oceanographer at the Scripps Institution of Oceanography. Many of the animals, such as sponges and corals, are thought to be slow-growing and some support unique sea life.
  • The vast majority of biodiversity in the deep sea hasn't been described. Levin says it should be characterized before mining to know whether it has unique properties useful for medicine, materials and more.
  • "We don't yet know enough about the connections" between the seafloor and water column, she says, adding fisheries depend on a healthy water column and it's unclear how mining one area may affect another.

Other big questions are how far the plumes of sediment created when nodules are harvested travel and what impact they have on the ocean environment.

  • Recent tests in the CCZ found the densest part of the plume generated by a prototype nodule collector rose 16–20 feet above the seafloor, while smaller concentrations of sediment were detected at heights up to about 100 feet.
  • Most of the plume settled in or near the test area, says marine geologist Annemiek Vink of the Federal Institute for Geosciences and Natural Resources in Germany, which is conducting the research as part of a project called MiningImpact. But they found nodules blanketed with sediment up to about 1,600 feet away from the source.
  • Another study found similar results and "although this experiment was just in one location, it points to the need for more experiments and means we must be cautious when making statements about plumes spreading far and wide," says study author Bramley Murton, a marine geologist at the U.K.'s National Oceanography Centre.

Yes, but: These testing areas are small in comparison to what would be mined, says Levin.

  • And there are open questions about the effects of plumes farther from the collection sites.

What to watch: Vink says the team is working on detailed analyses of how the sediment behaves at different depths of the water column and how much is redeposited or blanketed on the nodules. They're also analyzing samples of microbes and fauna taken before and after the tests as well as noise emissions, and they plan to monitor the area over the next five years.

  • Other researchers meanwhile are studying whether artificial nodules can be placed on the seafloor to aid recovery after mining.

The bottom line: "We don’t have the science ready to make effective regulation," Levin says. "And two years is probably not enough time if we invoke the precautionary approach."

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