Deep-Sea Mining Could Starve the Ocean’s Food Web, New Study Warns

Deep-sea mining may disrupt life in the ocean's twilight zone

A University of Hawaii study published in Nature Communications warns that discharges from deep-sea mining trials could harm key mid-water ecosystems and ripple up the marine food web. The researchers analyzed water and sediment released during a 2022 mining trial and focused on the ocean's twilight zone, roughly 650–5,000 ft (200–1,500 m) below the surface.

What the study found

Companies seeking polymetallic nodules on the seafloor bring mineral-rich material to the surface and then return excess seawater, seabed sediment and fines to the ocean. That process creates a murky plume of particles whose grain sizes closely match the natural food particles eaten by zooplankton that inhabit the twilight zone.

The study's authors warn that zooplankton may consume those mining-derived particles — described by the researchers as a form of "junk food" — and become undernourished. Because more than half of the ocean's zooplankton live in this depth range, the research estimates that about 60% of micronekton (small swimming animals that feed on zooplankton) could be affected. Those micronekton in turn feed commercially important species such as mahi mahi and tuna, creating a potential cascade of impacts up the food chain.

Michael Dowd, lead author and oceanography graduate student, said: 'If these organisms down at depth are no longer present because their food web has collapsed, then that can impact higher food webs and more commercial interests.'

Broader implications and policy context

Previous research on deep-sea mining has focused mainly on direct damage to the seafloor; this study highlights significant risks in the mid-water column. The International Seabed Authority has already issued several exploration contracts for seabed minerals, and national-level interest — including policy moves in the United States — has accelerated discussion about opening the deep ocean to extraction.

Environmental researchers warn that large-scale, sustained mining could spread impacts regionally and may also release long-stored carbon from the seabed, with climate implications. Several scientists quoted in response to the paper called for much more research to define safe release depths and water-quality standards or to determine whether deep-sea extraction can be managed without causing severe ecosystem harm.

Alternatives and next steps

Senior author Brian Popp and others note that alternatives exist for obtaining necessary metals, including recycling batteries and electronics and reprocessing terrestrial mine tailings. The authors recommend further experiments and monitoring to quantify mid-water impacts, to design discharge protocols that minimize harm, and to weigh alternatives before any large-scale mining begins.

Conclusion: The study calls for precaution. Small, isolated operations may have limited local effects, but cumulative, multi-operator mining over years could pose substantial risks to ocean food webs and fisheries.

Reporting note: This article summarizes peer-reviewed research and public statements from the study team and independent experts. For complete details and methods, see the original publication in Nature Communications.