The UN has described the deep sea as “the largest source of species and ecosystem diversity on Earth.” Life thrives particularly on the vast expanses of sea floor known as abyssal plains, amid the submarine mountains that rise from them and around superheated springs. Extremes of temperature and pressure have proved no obstacle to the creatures here. But plans to commercially mine the seabed pose a grave threat to their survival.

Abyssal plains, the flattest places on the planet, are home to fish, eels, crustaceans, molluscs, sponges, sea cucumbers, starfish and brittle stars to name a few.

Virtually every dive to a submarine mountain, or “seamount”, reveals species endemic to that particular island of life. More than 800 species of fish have been discovered, as well as gardens of corals and sponges that attract further species of crustacean, mollusc and sea cucumber. Open-sea fauna such as tuna, sharks and sea turtles also visit, to feed on the permanent residents.

More than 500 species have been identified in hydrothermal vent ecosystems, including tubeworms, mussels, crabs, squat lobsters, limpets, scaleworms, zoarcid fish and octopuses.

Mining companies are eager to scrape metal-rich nodules off the abyssal plains using mechanical “crawlers” reminiscent of tanks. Other robots may be able to extract the metallic crusts that cover many seamounts. And the metal-rich sulphide deposits at hydrothermal vents could be crushed and excavated too.

As well as destroying species directly, mining would stir up sediment that could smother sponges and corals. To date, only 5% of the ocean floor has been explored. Scientists argue that more research is needed to understand the extraordinary range of life down here, its wider importance for the ocean, and the impact mining could have.

This article is part of our deep-sea mining series. Read more here:

The future of deep seabed mining

Can a ‘mining code’ make deep seabed extraction sustainable?

Deep seabed mining: key questions

We need to better understand the deep ocean if mining is to go ahead

Is China ready to mine the deep sea?