The Metals Company -- a leading deep-sea mining firm -- paid Australia's government science agency to pore through data collected during test mining in the remote Pacific Ocean.
Huge tracts of Pacific Ocean seabed are carpeted in polymetallic nodules, bulbous lumps of rock that are rich in metals used in battery production -- such as cobalt and nickel.
The Metals Company is pushing to be the first to mine these nodules in international waters, striving to exploit a remote expanse known as the Clarion-Clipperton Zone.
Australia's government science agency released a series of technical reports on Thursday detailing how mining could be managed.
Bottom-dwellers such as sea cucumbers, marine worms, starfish and crustaceans could see "significant declines in abundance immediately following mining", research found.
Some of these species would partially bounce back within a year, but filter feeders and other tiny organisms that feast on seabed sediments showed "minimal recovery".
"On the seafloor, our research shows that there are substantial local impacts from different mining operations," scientist Piers Dunstan said during a briefing.
Deep-sea mining companies are still figuring out the best way to retrieve nodules that can lie five kilometres (three miles) or more beneath the waves.
Most efforts focus on robotic harvesting machines, or crawlers, which hoover up nodules as they rove the ocean floor.
The Australian scientists looked at how sharks and fish might be harmed by plumes of sediment discharged as mining waste.
In some scenarios, apex predators could see toxic metals start to build up in their blood after prolonged exposure to these plumes.
"Long-lived top predators, such as swordfish and large sharks, accumulated the highest simulated metal concentrations," scientists noted in one report.
- 'Risk of harm' -
Simulations showed blood metal concentrations would not exceed international health guidelines, and impacts were less pronounced if sediment was discharged at a greater depth.
"This project helps ensure that if deep-sea mining were to go ahead, there is a clear approach to understand potential risks and impacts to marine life and ecosystems," Dunstan said.
Canada-based The Metals Company is striving to start industrial deep-sea mining in the Clarion-Clipperton Zone within the next two years.
The International Seabed Authority -- which oversees deep-sea mining in international waters -- has yet to adopt long-awaited rules governing the industry.
The Metals Company has indicated it could forge ahead even without the authority's approval, pointing to an obscure US law that says American citizens can recover seabed minerals in areas beyond the nation's jurisdiction.
The firm paid Australia's Commonwealth Scientific and Industrial Research Organisation -- or CSIRO -- around US$1 million to compile the reports.
CSIRO stressed it was not for, or against, deep-sea mining -- but that its work would help to measure and monitor impacts should it go ahead.
Energy transition expert Tina Soliman-Hunter said it was one of the "most comprehensive" pieces of research on deep-sea mining to date.
"Without such research, there is a risk of harm from mining activities that can persist for generations," said Soliman-Hunter, from Australia's Macquarie University.
Found in international waters between Mexico and Hawaii, the Clarion-Clipperton Zone is a vast abyssal plain spanning some 4 million square kilometres (1.7 million square miles).
Deep-sea mining negotiators to meet under Trump shadow
United Nations, United States (AFP) July 5, 2025 -
The International Seabed Authority (ISA) meets next week to continue debating rules for ocean floor mining in international waters, after the United States moved to unilaterally kick-start the controversial industry.
The Jamaica-based body, created by the UN Convention on the Law of the Sea, has been working for over a decade on rules governing mineral extraction on the high seas.
Nations are divided over the desire to exploit the ocean depths for nodules rich in metals needed for electric vehicles and other emerging technologies -- and worries about disrupting, or possibly decimating, fragile ecosystems.
The United States, which is not a signatory to the UN convention or an ISA member, disrupted the painstaking process this year when President Donald Trump issued an executive order calling for his government to speed up issuing permits for underwater mining, including in international waters.
Canadian firm The Metals Company (TMC) jumped at the opportunity and in April filed the first US application for a deep-sea mining license, angering environmental groups and many nations.
Against this backdrop, the ISA's 36-member executive council reconvenes Monday in Kingston for two more weeks of negotiations on a "mining code."
"Our shared objective remains the completion of the negotiations" this year, Council President Duncan Muhumuza Laki wrote in a letter ahead of the meetings.
The Ugandan diplomat said an additional session in the fall may be needed to meet a year-end deadline.
Louise Casson of Greenpeace called the push to wrap up negotiations "both very unwise and unfeasible."
Nations should not be "bullied" into rushing through rules after TMC's "incredibly controversial and rogue move," she told AFP.
Leticia Carvalho, secretary-general of the full ISA, said that with the global body "on the cusp of finalizing" its rules, "it is imperative that we get it right."
"When I speak of the need for timely action, this should in no way be interpreted as a call for rushed or unconsidered decisions," the Brazilian oceanographer told AFP in an e-mail.
- Moratorium -
Members are deeply divided over how to proceed, with a growing number calling for at least a temporary moratorium on deep-sea mining.
French President Emmanuel Macron opened the UN Ocean conference last month in Nice saying it would be "madness to launch predatory economic action that will disrupt the deep seabed, disrupt biodiversity, destroy it and release irrecoverable carbon sinks -- when we know nothing about it."
His country joined Chile, Costa Rica and Panama in a recent letter saying it is "clear" that the regulations "are not ready for adoption yet," and suggesting discussions on a new timeline.
"We categorically disassociate ourselves from any suggestion or interpretation that the Council is bound, legally or politically, to adopt the regulations by the end of the year," the letter said.
At the previous session in March, the ISA Council got through debate on 55 of 107 proposed rules.
Carvalho said though some members "have expressed differing views on the desirability or timing of future mining activities, the overwhelming majority have remained committed to continuing the negotiations with good faith, diligence and unity, recognizing the imperative of establishing a robust and science-based regulatory regime."
A meeting of the full 169-member ISA is scheduled for July 21-25.
The number of ISA members in favor of a precautionary pause to mining continues to grow -- from 12 in 2022 to 37 today, according to the NGO alliance Deep Sea Conservation Coalition -- but they are still far from the majority.
At that meeting, Chile hopes to revive its bid to adopt "the protection and preservation of the marine environment" as a "general policy" for the body.
The move is seen as a first step towards a moratorium.
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