Deep-Sea Mining Waste Threatens Ocean Food Webs

A new study published in Nature Communications, November 6, 2025 has revealed that waste discharge from deep-sea mining operations could severely disrupt midwater food webs in the Pacific Ocean. The research, conducted in the Clarion-Clipperton Zone (CCZ), warns that the release of mining waste into the water column could alter the structure of marine food chains and endanger the sustainability of deep-sea ecosystems.

Stretching between Hawaii and Mexico, the Clarion-Clipperton Zone is known for its vast deposits of polymetallic nodules—rocky lumps rich in valuable metals such as cobalt, nickel, and manganese. More than 1.5 million square kilometers of this seabed have already been licensed for exploration by the International Seabed Authority (ISA). Yet, scientists remain divided over the environmental consequences of mining these deep-sea resources.

According to the research team, most previous studies have focused on benthic (seafloor) communities, while little attention has been given to midwater ecosystems that could be affected by mining waste discharge. During mining operations, seawater and sediments are pumped up along with the nodules for processing on ships, and the resulting slurry—containing fine sediment and crushed mineral particles—is discharged back into the ocean at depths of 700 to 1,500 meters.

“Deep-sea mining waste plumes have the potential to alter natural particle availability and disrupt the flow of energy through midwater food webs,” Michael H. Dowd, the authors from University of Hawai wrote. “These effects could cascade upward, affecting zooplankton, small fish, and even top predators that depend on them.”

Impact on the Food Web

The study found that large natural particles—those greater than six micrometers in diameter—form the primary base of the midwater food web. Around 65 percent of the sampled marine organisms, including zooplankton and micronekton, relied heavily on these large particles as their main energy source.

However, waste particles from mining operations differ markedly in quality. While they may be more abundant, they contain fewer essential amino acids compared to natural particles, making them less nutritious.

“This means that although mining waste increases the quantity of particles, it lowers their nutritional quality,” said Dowd again. “When the foundation of the food web is weakened, the entire ecosystem can be affected.”

Since about 53 percent of zooplankton feed directly on particles and roughly 60 percent of micronekton feed on zooplankton, a decline in the quality of particulate matter could trigger a bottom-up disruption—rippling through the food web and ultimately impacting larger species such as tuna and whales.

A Threat to Marine Ecosystems and Fisheries

The researchers warned that disturbances to midwater food webs could undermine global ecological stability, including the ocean’s biological carbon pump—a process crucial for absorbing carbon dioxide from the atmosphere. Such disruptions could also threaten commercial fish populations that millions of people depend on for food and livelihood.

“Pelagic ecosystems play a vital role in climate stability and oceanic food security,” the team wrote. “Altering the base of these food webs could destabilize entire marine systems.”

The study also noted that discharging waste into the midwater column poses greater ecological risks than returning it to the seafloor. The authors therefore urged stronger regulations to protect not only benthic ecosystems but also mesopelagic and bathypelagic communities that have largely been overlooked in environmental impact assessments.

Call for Stronger Regulation

The researchers called on international bodies such as the ISA and countries involved in deep-sea exploration to strengthen their environmental safeguards. Among the recommended measures is returning mining waste to the seafloor under strict monitoring instead of releasing it into the midwater column, which serves as an essential habitat for countless species.

“The environmental impact of midwater waste discharge could persist for decades and be extremely difficult to reverse,” the study concluded. “Caution is needed before sacrificing deep-sea ecological functions for short-term economic gain.”

The findings come at a critical moment when demand for minerals such as cobalt and nickel—used in batteries for electric vehicles and renewable energy technologies—is surging. While deep-sea mining is often promoted as a solution to the global mineral shortage, this research highlights its potential to create a new ecological crisis beneath the waves.

As global debate over deep-sea mining intensifies, scientists are urging policymakers to weigh industrial ambitions against the long-term survival of marine ecosystems—before it’s too late. (Wage Erlangga)

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