Deep-Sea Mining Waste Threatens Global Fisheries and Marine Life

The Hidden Dangers of Deep-Sea Mining

Drilling for minerals deep in the ocean could have significant consequences for the tiny animals that form the foundation of the vast marine food web, ultimately affecting fisheries and the food we consume, according to a new study. This research highlights the potential risks associated with deep-sea mining, which involves extracting “polymetallic nodules” rich in critical minerals like copper, iron, and zinc from the seafloor.

Although not yet commercialized, nations are increasingly pursuing deep-sea operations due to rising demand for these minerals in electric vehicles, energy transition technologies, and military applications. The study focuses on the environmental impact of waste generated during these mining activities.

What the Study Discovered

The University of Hawaii researchers examined water and waste samples collected from a deep-sea mining trial conducted in 2022. Their findings, published in the journalNature Communications, reveal that mining waste could affect a wide range of marine life, from tiny shrimp smaller than 2 millimeters to fish up to 5 centimeters long.

This is because, after mining companies bring the mineral-rich nodules to the surface, they release excess seawater, ocean floor dirt, and sediment back into the ocean. This process creates a murky plume of particles similar in size to naturally occurring food particles consumed by zooplankton at that depth.

Zooplankton make up more than half of the ocean’s zooplankton population. If these organisms consume the waste particles—referred to as “junk food” by senior study author Brian Popp—it can impact 60% of micronekton that feed on them. This undernourishment poses a problem since these tiny organisms serve as a crucial food source for higher trophic levels, including commercially important fish such as mahi mahi or tuna.

Michael Dowd, the study’s lead author and an oceanography graduate student, explained: “Surface fish can dive down deep into the water; they feed on organisms down at depth. 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.”

Impact on the Water and Alternative Sources

While other research has highlighted the negative environmental impacts of deep-sea mining, much of the focus has been on the seafloor. This study, however, examines mid-water effects. The researchers emphasize the need for further investigation into the appropriate quality and depth at which dirty water and sediment from sea mining should be returned to the ocean.

They noted that returning the excess directly to the ocean floor or at other depths could be just as environmentally disruptive as in the “twilight zone,” albeit in different ways. Brian Popp suggested that digging up the deep sea might not be necessary, pointing to alternative sources of metals such as recycling batteries and electronics or sifting through mining waste and tailings.

“If only a single company is mining in one single spot, it’s not going to affect a huge fishery. It’s not going to affect a huge amount of water. But if many companies are mining for many years and outputting a lot of material, this is going to spread across the region,” said Dowd. “And the more mining occurs, the more a problem it could be.”

Where Deep-Sea Mining Stands

It may not be feasible to simply halt ocean mining. The International Seabed Authority, which governs mineral activity beyond national jurisdiction, has already granted several exploration contracts. In the United States, former President Donald Trump expressed interest in deep-sea mining during tense trade negotiations with China, which has limited U.S. access to China’s supply of critical minerals.

In April, Trump signed an executive order directing the National Oceanic and Atmospheric Administration (NOAA) to expedite the permitting process for companies to mine the ocean floor. In May, the administration announced plans to consider selling leases to extract minerals off the South Pacific island of American Samoa. Last month, NOAA sent a draft rule to the White House to streamline operations.

Environmental groups have raised concerns about deep-sea mining, citing not only direct harm to wildlife but also the disturbance of planet-warming carbon dioxide currently stored in the ocean and on its floor.

Sheryl Murdock, a deep-sea postdoctoral researcher at Arizona State University who was not involved in the study, emphasized the broader implications: “It was well laid out in the study that the impacts wouldn’t necessarily be just the depth that the plume is released. The question being: Is it worth a few minerals to potentially destroy the way that the oceans function?”

Diva Amon, a marine biologist and postdoctoral researcher at the University of California, Santa Barbara, praised the research for examining potential consequences. “All of this could lead to species illness, species movement, species death. And depending on the scale of this, that could have graver repercussions, like species extinctions,” she said. “There’s a lot more research that needs to be done to be able to make an informed decision about how to manage this industry, if it does start, in a way that will prevent, essentially, serious harm to the ocean and ocean ecosystem.”