A new study from the University of Hawai’i (UH) at Mānoa, published on November 6 in Nature Communications, provides the first direct evidence that waste from deep-sea mining could disrupt vital ecosystems in the Pacific Ocean’s Clarion-Clipperton Zone (CCZ). This area, one of the most biologically rich regions of the deep sea, is now the focus of growing industrial interest. Researchers found that sediment discharged during mining operations could harm marine life in the midwater “twilight zone,” a key habitat between 200 and 1,500 meters below the surface that supports vast populations of tiny drifting animals called zooplankton — the foundation of the ocean’s food web.
The team determined that 53% of zooplankton and 60% of micronekton, which feed on zooplankton, would be affected by mining waste discharge. Such disturbances could ripple through the food chain, ultimately impacting larger predators such as fish, seabirds, and marine mammals.
Murky Plumes and “Junk Food” Sediment
“When the waste released by mining activity enters the ocean, it creates water as murky as the mud-filled Mississippi River. The pervasive particles dilute the nutritious, natural food particles usually consumed by tiny, drifting Zooplankton,” said Michael Dowd, lead author of the study and a graduate student in Oceanography at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST).
“Micronekton, small shrimp, fish and other animals that swim, feed on zooplankton. Some migrate between the depths and near surface waters and they are consumed by fish, seabirds and marine mammals. Zooplankton’s exposure to junk food sediment has the potential to disrupt the entire food web.”
Measuring the Nutritional Impact of Deep-Sea Mining
The research, titled “Deep-sea mining discharge can disrupt midwater food webs,” examined the effects of sediment plumes released during a 2022 mining test in the CCZ. This vast region is targeted for the extraction of polymetallic nodules that contain valuable minerals such as cobalt, nickel, and copper — key components for electric vehicles and renewable technologies.
By collecting and analyzing water samples from the depths where waste was discharged, the scientists found that mining particles contained far fewer amino acids, an important measure of nutritional quality, than the natural particles that typically nourish marine organisms.
“This isn’t just about mining the seafloor; it’s about reducing the food for entire communities in the deep sea,” said co-author Erica Goetze, a SOEST oceanography professor and marine zooplankton specialist. “We found that many animals at the depth of discharge depend on naturally occurring small detrital particles — the very food that mining plume particles replace.”
At present, around 1.5 million square kilometers of the CCZ are licensed for deep-sea mining exploration, reflecting the surge in global demand for minerals used in low-carbon technologies.
Disrupting an Ecosystem Built on Scarcity
During the mining process, nodules are collected from the seafloor along with surrounding sediments and seawater, then pumped to a surface vessel where nodules are separated from the waste material. The leftover sediment and fine nodule fragments are then released back into the ocean. Some companies have proposed releasing this waste within the twilight zone, but the environmental consequences of such practices have remained largely unknown — until now.
These findings underscore a major regulatory gap, as no international rules currently govern where or how mining waste can be discharged.
The twilight zone teems with life, including krill, squid, fish, octopus, and delicate jelly-like species. Many of these organisms travel upward toward the surface each night to feed and then descend again by day, transporting carbon to the deep ocean in the process. This vertical migration helps maintain the planet’s carbon balance and supports the health of marine ecosystems worldwide.
“Our research suggests that mining plumes don’t just create cloudy water — they change the quality of what’s available to eat, especially for animals that can’t easily swim away,” said co-author Jeffrey Drazen, a deep-sea ecologist and SOEST professor of oceanography. “It’s like dumping empty calories into a system that’s been running on a finely tuned diet for hundreds of years.”
Global Implications for Marine Food Webs
The study raises concerns that large-scale mining could trigger widespread and long-lasting changes in ocean ecosystems if it proceeds without strict safeguards. Even commercial fisheries could be affected; for instance, tuna populations migrate through the CCZ, meaning the impacts of mining could extend to seafood consumed around the world.
“Deep-sea mining has not yet begun at a commercial scale, so this is our chance to make informed decisions,” said co-author Brian Popp, SOEST professor of Earth sciences and an expert in marine stable isotope biogeochemistry. “If we don’t understand what’s at stake in the midwater, we risk harming ecosystems we’re only just beginning to study.”
A Call for Responsible Regulation
The authors hope their results will guide policy discussions currently underway at the International Seabed Authority and inform environmental reviews conducted by the National Oceanic and Atmospheric Administration. They stress the importance of developing international rules to protect marine ecosystems from surface waters to the deep sea.
“Before commercial deep-sea mining begins, it is essential to carefully consider the depth at which mining waste is discharged,” added Drazen. “The fate of these mining waste plumes and their impact on ocean ecosystems varies with depth, and improper discharge could cause harm to communities from the surface to the seafloor.”
Additional contributors to the study include UH Mānoa oceanography graduate students Victoria Assad and Alexus Cazares-Nuesser, and oceanography professor Angelicque White.
