Plans to mine the ocean floor in one of the most remote stretches of the Pacific are facing renewed scrutiny, following the discovery of whales and dolphins — including an endangered sperm whale — in the area.

The Clarion-Clipperton Zone (CCZ), a vast abyssal plain stretching between Hawaii and Mexico, has long been targeted by mining companies for its rich deposits of polymetallic nodules. 

These lumps are scattered across the seabed, containing high concentrations of valuable metals such as manganese, nickel, copper and cobalt – crucial for electric vehicle batteries and renewable technologies.

A sea cucumber (Psychropotes longicauda) on manganese nodules in the Clarion Clipperton Zone. Credit: Wikimedia Commons/ROV KIEL 6000, GEOMAR.

Now, two new studies suggest the deep-sea ecosystems in the CCZ may be far more biologically complex — and vulnerable — than previously thought.

“We know remarkably little about these ecosystems, which are hundreds of miles offshore and include very deep waters,” says Dr Kirsten Thompson, a marine biologist at the University of Exeter and co-author of both studies. “We do know many species here are long-lived and slow growing, especially on the seabed”.

“It’s very hard to predict how seabed mining might affect these species and wider ecosystems, and these risks must urgently be assessed.”

The research team led by the University of Exeter found multiple species of whales and dolphins in the region, based on 13 days of acoustic and visual surveying aboard Greenpeace’s Arctic Sunrise. In total, they logged 74 acoustic detections and six visual sightings, including common dolphins, Risso’s dolphins, and a sperm whale — a species listed as vulnerable.

One of the studies reviewed the known sensitivity of marine species in the CCZ to underwater noise — a key impact of mining. Of the taxonomic classes documented in the region, only 35% have been studied for their responses to noise. Chronic exposure to mining noise might have cascading ecological consequences, disrupting key behaviours, the researchers say. 

“If deep-seabed mining becomes a reality, whales and dolphins will be exposed to multiple sources of noise throughout the water column,” says marine scientist Dr Kirsten Young. 

“Many species are highly sensitive to certain frequencies – chronic ocean noise can mask social and foraging communications, and whales could be displaced from critical habitats,” she says. 

This acoustic vulnerability takes on new urgency given recent evidence that whales and dolphins are already inhabiting the very zones earmarked for future mining.

“The confirmed presence of cetaceans, including threatened sperm whales, in areas that The Metals Company is targeting for deep sea mining is yet another clear warning that this dangerous industry must never be allowed to begin commercial operations,” says Louisa Casson, the Global Project Leader for Greenpeace’s Stop Deep Sea Mining campaign.

These findings are published in Frontiers in Marine Science.

The Clarion Clipperton Zone. Credit: Wikimedia Commons.