Deep-sea mining in a remote part of the Pacific Ocean could harm ocean life including whales and dolphins, new research shows.
The Clarion Clipperton Zone (CCZ) of the Eastern Pacific is a vast area of deep ocean and seamounts.
A Canadian firm – The Metals Company – is planning to explore parts of the CCZ for polymetallic nodules.
In two new studies, researchers found whales and dolphins – including an endangered sperm whale – in the CCZ, and raise concerns about impacts on a wide range of marine species.
"We know remarkably little about these ecosystems, which are hundreds of miles offshore and include very deep waters," said Dr Kirsten Young, from the University of Exeter.
"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."
Dr Young said noise from mining would travel great distances underwater – possibly hundreds of kilometres through a SOFAR channel.
One of the research papers reviews noise sensitivity among species known to live in the CCZ , and finds that only 35% of taxonomic classes there have been studied for noise impacts.
Soniferous fish, which rely on acoustic communication, are particularly vulnerable to noise.
Chronic exposure to mining noise might have cascading ecological consequences, disrupting key behaviours, the researchers say.
The second study is a survey of whales and dolphins, conducted from the Greenpeace vessel Arctic Sunrise.
Over 13 days of visual and acoustic monitoring, there were 74 acoustic detections and six sightings.
These included a sperm whale, Risso's dolphins, common dolphins and 70 dolphin groups that could not be identified to species level.
Dr Young said: "If deep seabed mining becomes a reality, whales and dolphins will be exposed to multiple sources of noise throughout the water column.
"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.
"The behaviour and impact of sediment plumes created by mining is also poorly understood but could affect food webs."
Louisa Casson of Greenpeace International said: "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."
The review paper, published in the journal Marine Pollution Bulletin, is entitled: "Noise from deep-sea mining in the Clarion-Clipperton Zone, Pacific Ocean will impact a broad range of marine taxa."
The whale and dolphin paper, published in Frontiers in Marine Science, is entitled: "Threatened cetaceans in a potential deep seabed mining region, Clarion Clipperton Zone, Eastern Pacific."
