Scientists detected 5,000 sea creatures nobody knew existed. It’s a warning.

There are bright, gummy creatures that look like partially peeled bananas. Glassy, translucent sponges that cling to the seabed like chandeliers flipped upside down. Phantasmic octopuses named, appropriately, after Casper the Friendly Ghost.

And that’s just what’s been discovered so far in the ocean’s biggest hot spot for future deep-sea mining.

To manufacture electric vehicles, batteries and other key pieces of a low-carbon economy, we need a lot of metal. Countries and companies are increasingly looking to mine that copper, cobalt and other critical minerals from the seafloor.

A new analysis of the Clarion-Clipperton Zone, a vast mineral-rich area in the Pacific Ocean, estimates there are some 5,000 sea animals completely new to science there. The research published Thursday in the journal Current Biology is the latest sign that underwater extraction may come at a cost to a diverse array of life we are only beginning to understand.

“This study really highlights how off the charts this section of our planet and this section of our ocean is in terms of how much new life there is down there,” said Douglas McCauley, an ocean science professor at the University of California at Santa Barbara who was not involved in the study.

It also underscores a conundrum of so-called clean energy: Extracting the raw material needed to power the transition away from fossil fuels has its own environmental and human costs.

Advocates for deep-sea mining say the toll of getting those metals is at its lowest under the sea, away from people and even richer ecosystems on land. “It just fundamentally makes sense that we look for where we can extract these metals with the lightest planetary touch,” said Gerard Barron, chief executive of the Metals Company, one of the leading firms aiming to mine the seafloor for metals.

But the discovery of so much sea life reveals how little we know about Earth’s oceans - and how great the cost of renewable energy may be to life below the waves.

Life at the bottom of the abyss

At the bottom of the ocean, miles below the surface, is a potato. A bunch of potatoes. Or more precisely, a bunch of rocks that look like potatoes.

After a shark’s tooth or clam’s shell descends the depths to the seafloor, layer upon layer of metallic elements dissolved in the seawater build up on those fragments of bone and stone over millions of years.

The results are submarine fields of potato-size mineral deposits called polymetallic nodules. For a society in need of those minerals, the nodules are unburied treasure, sitting right there on the sea floor ready to be collected.

One of the biggest assemblages of nodules sits at the bottom of the Clarion-Clipperton Zone, a region twice the size of India sandwiched between Mexico and Hawaii. The only light that deep comes from occasional flashes of bioluminescent animals.

Despite decades of interest in mining this abyss, little is known about the region’s baseline biodiversity. So a team led by the Natural History Museum in London analyzed over 100,000 records from years of research cruises sampling sea creatures.

For some expeditions, scientists plunged boxes to the bottom and winched them back to the surface, much like an arcade claw game. For others, researchers used remote-controlled underwater vehicles to snap pictures or scoop up some “poor, unsuspecting starfish or sea cucumber,” said Muriel Rabone, the researcher at Natural History Museum who led the paper.

The team found between 6,000 and 8,000 animals, with about 5,000 being completely new to science. One of the world’s few remaining intact wildernesses, the extreme depths and darkness of the Clarion-Clipperton Zone, or CCZ, have fostered the evolution of some animals found nowhere else on Earth.

Among them is the gummy squirrel, a neon-yellow sea cucumber that may use its long tail to surf underwater waves and roam the seabed like “wildebeests traveling across the Serengeti,” said Adrian G. Glover, another co-author from the Natural History Museum.

Another animal spotted is a beady-eyed, stubby-armed cephalopod called the Casper octopus, discovered in Hawaii in 2016 and named for its ghostly white appearance due perhaps to a lack of pigment in its food.

Or at least scientists think they’ve seen the octopus in the CCZ. “These are only visual observations, so we can’t be sure it is the same species,” said Daniel Jones of the National Oceanography Centre in England, another paper co-author.

Many animals find shelter in the nodules themselves. Tiny ragworms burrow into them, while glass sponges, which use silicon to build their eerie, crystal-like skeletons, grow out of them. Little is known about how any of these species interact and form ecosystems.

“It’s a surprisingly high-diversity environment,” Glover said.

The need for nodules

That biodiversity has led over 700 marine science and policy experts to call for a pause on mining approvals “until sufficient and robust scientific information has been obtained.” Too little is known, they say, about how mining may hurt fisheries, release carbon stored in the seabed or put plumes of sediment into the water. Old underwater mining test sites show little sign of ecological recovery.

The bottom of the ocean was once thought to be “a bit of a desert,” said Julian Jackson, senior manager of ocean governance at the Pew Charitable Trusts, which funded the paper and wants a moratorium on deep-sea mining.

“But now we understand that actually there’s vast amounts of biodiversity in the abyssal plains,” he said.

Proponents of deep-sea mining argue it comes with fewer ethical trade-offs than does land-based extraction. Deep in the ocean, there are no Indigenous communities to move, no child labor to exploit and no rainforests to raze. Right now, the top nickel-producing country is rainforest-rich Indonesia.

“You couldn’t dream up a better place to put such a large, abundant resource,” said Barron, the executive at the Metals Company based in Vancouver. His firm has also provided funding to Natural History Museum researchers.

The company says it has designed its robotic vehicle to pick up nodules with as little sediment as possible. But Barron admits that it’s a “bad day” for any organism sucked up. “This is not about zero impact,” he said, but about minimizing the global impact of mining. “I don’t know of anything that has zero impact.”

For now, there is no commercial extraction in the CCZ, where no one nation is in charge. Environmentalists and mining executives are waiting for a U.N.-chartered body called the International Seabed Authority to issue regulations around underwater mining. But the small Pacific nation of Nauru, which is the Metals Company’s partner, invoked a clause in the U.N. Convention on the Law of the Sea to speed up the process.

If all goes according to plan, the Metals Company expects to begin mining by late 2024 or early 2025. Opponents worry that isn’t enough time to make sure it can be done safely. Jackson said it is “completely undecided about how we’re going to oversee and enforce any of these regulations.”

“That’s a very live debate at the moment,” he added.

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This article is part of Animalia, a column exploring the strange and fascinating world of animals and the ways in which we appreciate, imperil and depend on them.