New Study Reveals Deep-Sea Mining Waste Threatens Marine Life

A groundbreaking study led by researchers at the University of Hawaii at Mānoa has unveiled significant risks associated with waste discharged from deep-sea mining operations in the Pacific’s biodiverse Clarion-Clipperton Zone (CCZ). Published in Nature Communications on November 6, 2025, this research is the first of its kind to demonstrate that mining waste could severely disrupt marine life in the ocean’s midwater “twilight zone,” which spans depths between 200 and 1,500 meters and houses vast communities of zooplankton.

The study found that approximately 53% of all zooplankton and 60% of micronekton, organisms that feed on zooplankton, would be negatively affected by the discharge from mining activities. This disruption poses a threat not just to these organisms but also to higher-level predators within the ocean’s food web.

“When the waste released by mining activity enters the ocean, it creates water as murky as the mud-filled Mississippi River,” stated Michael Dowd, lead author of the study and a graduate student in oceanography at SOEST. He explained that the toxic particles dilute the nutritious, natural food particles typically consumed by drifting zooplankton.

The research, titled Deep-sea mining discharge can disrupt midwater food webs, examines the effects of mining waste released during a 2022 trial in the CCZ. Researchers collected and analyzed water samples from the depths of discharge, revealing that the sediment particles contained significantly lower concentrations of amino acids—crucial indicators of nutritional value—compared to naturally occurring particles that sustain life in these depths.

Erica Goetze, co-author and SOEST oceanography professor, emphasized the gravity of these findings. “This isn’t just about mining the seafloor; it’s about reducing the food for entire communities in the deep sea,” she said, highlighting that many species at the depth of discharge depend on naturally occurring small detrital particles, which the mining plume replaces.

As countries increase their efforts to meet rising global demands for metals essential for electric vehicle batteries and other low-carbon technologies, the implications of this study grow increasingly urgent. Currently, approximately 1.5 million square kilometers of the CCZ are licensed for deep-sea mining, raising concerns about the long-term impacts on marine ecosystems.

Understanding the Mining Process and Its Implications

During deep-sea mining, polymetallic nodules—rich in minerals such as cobalt, nickel, and copper—are extracted from the seafloor. This process involves collecting nodules along with seawater and sediment, which are then transported to collection ships for separation. The waste, containing seawater and sediment, must be returned to the ocean. Although the exact release depth is unclear, some operators have suggested discharging waste within the twilight zone.

Until this study, the effects of mining waste on midwater communities were largely unknown. Understanding these impacts is crucial for establishing regulations around waste discharge, which are currently lacking and represent a significant gap in governance for the industry.

The twilight zone is teeming with diverse life forms, including krill, fish, squid, and jellyfish. These organisms play a critical role in carbon transport to deeper ocean layers, which is vital for both oceanic and human health. They either consume particles in the twilight zone or prey on those that do, creating a tightly linked food web connecting the surface ocean to the abyss.

“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,” explained Jeffrey Drazen, co-author and SOEST oceanography professor. He likened the situation to “dumping empty calories into a system that’s been running on a finely tuned diet for hundreds of years.”

Addressing Urgent Environmental Concerns

The findings of this study raise urgent concerns about the potential long-lasting effects of large-scale commercial mining without adequate environmental safeguards. For instance, Pacific tuna fisheries operate in the CCZ, meaning mining waste could directly impact fish that end up on dinner plates around the world.

“Deep-sea mining has not yet begun at a commercial scale, so this is our chance to make informed decisions,” said Brian Popp, co-author and SOEST earth sciences professor. He cautioned that failing to understand the implications for midwater ecosystems could lead to significant harm.

The authors of the study aim to inform international regulatory decisions currently being shaped by the International Seabed Authority and the National Oceanic and Atmospheric Administration (NOAA), which oversees environmental assessments of U.S.-led deep-sea mining initiatives. They also advocate for expanded research to protect the full vertical extent of ocean ecosystems.

“Before commercial deep-sea mining begins, it is essential to carefully consider the depth at which mining waste is discharged,” added Drazen. He noted that the fate of mining waste plumes and their effects on ocean ecosystems vary significantly with depth, and improper discharge could endanger communities from the surface to the seafloor.

The study includes contributions from oceanography graduate students Victoria Assad and Alexus Cazares-Nuesser, as well as Angelicque White, an oceanography professor. Further details can be found in the publication Deep-sea mining discharge can disrupt midwater food webs in Nature Communications (2025).