Findings of a new study suggest that 53% of zooplankton and 60% of micronekton – small, swimming animals such as shrimp and fish – could be directly affected by deep-sea mining waste, disrupting food chains that extend to larger predators.
Waste plumes released from deep-sea mining operations in the Pacific Ocean’s Clarion-Clipperton Zone (CCZ) could starve life in one of the ocean’s most critical ecosystems – the midwater “twilight zone.” This the latest in a series of stark warnings that deep-sea mining could cause irreparable damage to life in the ocean and the latest study led by researchers at the University of Hawai‘i at Mānoa.
Published today in Nature Communications, the research shows that mining discharge clouds the water with nutrient-poor particles, replacing the organic detritus that sustains life 200-1,500 meters below the surface.
The findings suggest that 53% of zooplankton and 60% of micronekton – small, swimming animals such as shrimp and fish – could be directly affected, disrupting food chains that extend to larger predators including tuna, seabirds, and marine mammals.
“When mining waste enters the ocean, it turns clear waters as murky as the Mississippi,” said lead author Michael Dowd, a graduate researcher in UH Mānoa’s School of Ocean and Earth Science and Technology (SOEST). “These particles act like junk food for zooplankton – filling their guts but providing little nutrition. That shift can cascade through the entire food web.”
The Clarion-Clipperton Zone – a vast expanse between Hawai‘i and Mexico – has become a focal point for companies seeking polymetallic nodules rich in cobalt, nickel, and copper. During mining, seafloor sediment and nodules are pumped to the surface, separated, and the waste slurry is discharged back into the ocean.
While the exact discharge depth varies, some companies propose releasing waste within the twilight zone itself. Until now, the ecological consequences of this practice were largely unknown.
The UH Mānoa team analysed water samples collected during a 2022 mining trial and found that plume particles carried far fewer amino acids – key nutritional components – than natural food sources.
“This isn’t just about scraping the seafloor,” said co-author Erica Goetze, an oceanography professor at SOEST. “It’s about depleting the food that entire deep-sea communities depend on.”
The twilight zone teems with krill, small fish, squid, and gelatinous creatures that perform one of the planet’s largest daily migrations – ascending at night to feed near the surface and descending by day, helping transport carbon into the deep ocean.
By flooding this zone with nutrient-poor sediment, researchers warn, mining operations could interfere with that vertical link between the surface and the abyss.
“These plumes don’t just make the water cloudy – they alter the quality of food available,” said co-author Jeffrey Drazen, a deep-sea ecologist at SOEST. “It’s like dumping empty calories into a system that’s evolved to thrive on scarcity.”
The study’s implications extend beyond the deep sea. Tuna and other commercially important fish migrate through the Clarion Clipperton Zone, meaning disruptions there could reverberate through global fisheries and food supplies.
“Deep-sea mining hasn’t started commercially yet – which means we still have time to get it right,” said co-author Brian Popp, professor of Earth sciences at UH Mānoa. “Understanding what’s at stake in the midwater is essential before the first industrial operations begin.”
The authors urge international regulators, including the International Seabed Authority and NOAA, to consider discharge depth and plume dynamics when drafting environmental safeguards. They call for expanded research to protect the full vertical extent of ocean ecosystems – from the surface to the seafloor.
“The depth of waste release will determine the fate of these plumes,” said Drazen. “Without careful management, we risk harming communities throughout the water column – not just on the bottom.”