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Here’s what you’ll learn when you read this story:
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As companies hunt for metals in the depths of the ocean, scientists are taking inventory of every species that lives there.
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Mining the deep sea involves a suction mechanisms that could disturb or injure local fauna with sediment plumes.
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So far, 788 species have been spotted, and there could be even more waiting in the dark.
The prospect of deep sea mining in an otherwise pristine area is controversial, and as it continues to be debated, researchers who have been surveying the bottom of the ocean have found 788 reasons why businesses should rethink this venture.
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Between Mexico and Hawaii is a stretch of open water known as the Clarion-Clipperton Zone (CCZ). Though the depths of this region in the Eastern Pacific are understudied, companies are vying for a chance to possibly exploit it for metals. But their doing so could be a threat to biodiversity. Thomas Dahlgren is one of the marine biologists leading efforts by the University of Gothenburg (and other institutions) to map the seafloor, test mining impact, and inventory species living at depths of over 13,000 feet (4,000 meters) before they are disrupted.
“We found no evidence for change in faunal abundance in an area affected by sediment plumes from the test mining; however, species dominance relationships were altered in these communities, reducing their overall biodiversity,” Dahlgren said in a study recently published in the journal Nature Ecology & Evolution. “[We] highlight the value of integrated species-level taxonomic work in assessing the risks of biodiversity loss.”
Because many animals that live so far down rely on marine snow (a term used to refer to organic matter falling from above) for survival, populations can shift depending on where there is the most food. What Dahlgren and his team are concerned about is biodiversity loss from the impact of mining machines that use a suction device to remove deposits of highly sought-after minerals like copper, cobalt, gold, nickel, silver, zinc, and rare earth elements—all of which are contained in lumps of metals known as polymetallic nodules. Metals can also be found in crusts on underwater mountains and polymetallic sulfides that form around hydrothermal vents.
When a commercial deep-sea mining test was conducted on the abyssal plain of the Eastern Pacific in 2022, it found over 3,000 tons of metal. But the plumes that arise from mining could affect marine life like whales and dolphins with noise sensitivities, as well as overall biodiversity.
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Some potentially impacted species may not have even been discovered yet, while many others were identified with DNA data. Among the often unusual creatures in these waters are sea spiders, pink sea pigs, chimaeras, annelid worms, transparent sea cucumbers that can be seen digesting whatever they swallow, glass sponges, and solitaire corals that look like spectral blossoms in the darkness.
To protect ecosystems under threat, researchers need to know what lives there. Annelid worms, for example, are one of the largest groups of invertebrates to populate the seafloor, and teams from Gothenburg and the Natural History Museum of London discovered 300 new species of them while exploring the CCZ—though, unfortunately, some did not make it to the surface intact because of the drastic decrease in pressure.
When Dahlgren and his team tested the potential effects of sediment plumes from deep-sea mining, population densities of macrofauna (animals that are not microscopic) decreased by 37% in the direct path of the suction mechanism as it skimmed the seafloor. Most abyssal fauna (about 74%) live in the top layer of sediment, which is easily disturbed by mining machines. But there are also other concerns, including damage to gills, harm to feeding structures, and high metal concentrations being toxic to life on the abyssal plain.
“Longer-term monitoring of the impacted sites would enable better evidence on rates of recovery,” the researchers said. “This is particularly relevant for the areas impacted by plume settlement, where ecological changes may occur more slowly than in directly impacted sites and so should be a focus of future environmental impact studies.”
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