The United States is preparing to hold the first deep-sea mining lease sale in its history, offering more than 31 million acres of seabed off American Samoa to mining companies. 

The Department of the Interior has announced two lease areas on the territory’s outer continental shelf. The first covers approximately 16 million acres and the second more than 15 million acres. Both sales are scheduled for November 19th 2026.

The proposed areas sit directly next to the Rose Atoll Marine National Monument, a protected area that includes crucial nesting grounds for sea turtles, refuge for humpback whales and habitat for other endangered species.

Opposition to the move has been strong. American Samoa Governor, Pulaali’i Nikolao Pula has openly opposed any commercial extraction of minerals in the territory’s waters, and the Marine Minerals Administration received more than 76,000 public comments during an earlier comment period on the proposed sale, with an overwhelming majority against.

Oceana’s defence campaign manager, Julia Singer, said: ”These lease sales will open the floodgates to the exploitation of our deep seas. The message from American Samoa – and people across the United States – could not be clearer: stop deep-sea mining before it starts.

“Thousands of scientists, local leaders, and community members have warned of the danger that deep-sea mining poses, yet the Trump administration is continuing to ignore widespread opposition to this proposal. The US government should defend the deep, not fast-track its destruction.”

The mining lease targets the minerals found in ferromanganese crusts and polymetallic nodules. Mining the crusts involves removing the surface of the seafloor itself, while nodule mining uses robotic vehicles that move along the seabed to excavate the nodules. Once the material has been brought to the surface and separated, the waste is released back into the ocean, creating plumes that can smother organisms on the seafloor and in the surrounding waters. 

There have also been studies that found mining to release toxic and radioactive materials into the water column.

As the US moves towards leasing, a European research team is examining what a mining trial leaves behind. The research vessel SONNE has set sail from San Diego on expedition SO322, bound for the Clarion-Clipperton Zone (CCZ) in the Pacific, the area with the largest known deposits of polymetallic nodules on the seafloor. Germany, among others, holds an exploration licence there.

Led by Dr Matthias Haeckel of the GEOMAR Helmholtz Centre for Ocean Research Kiel, the team will investigate sites where nodule mining was tested five and a half years ago.

In spring 2021, Belgian company Global Sea Mineral Resources tested a remotely controlled pre-prototype collector on the seafloor at a depth of more than 4,000 metres. Over 74 hours the vehicle travelled around 32 kilometres and harvested nodules from an area of 54,000 square metres, roughly seven football pitches.

The expedition aims to assess the impacts on habitats in the water and on the seafloor, and the results will feed into fact-based recommendations for international regulation of deep-sea mining. It is part of the MiningImpact project, which has studied the environmental impacts of potential deep-sea mining since 2015.

These polymetallic nodules form slowly, growing about one to two millimetres over a million years. They are the only hard surface on the abyssal seafloor.

“Typically, we find two to three small organisms on each nodule,” said Haeckel, a biogeochemist and chief scientist of the expedition. Sea anemones, soft corals and giant stalked sponges, which in turn shelter other organisms, are absent where nodules have been removed. Because everything proceeds extremely slowly in the deep sea, Haeckel is certain of the likely outcome. “Likely, we will not see any recovery.”

Mining also disturbs the sediment, creating a plume that resettles within several hundred metres of the site. Animals attached to the nodules cannot escape it and are buried. “Some organisms can clean themselves, others cannot. Those that filter their food from the water are also very likely to be affected,” said Haeckel.

The scientists will also examine how long the effects of the plume persist, and whether artificial hard substrates could replace mined nodules and promote recolonisation of the seabed.

The ship carries 16 containers of scientific equipment, including the remotely operated vehicle KIEL 6000 and the autonomous underwater vehicle ABYSS, along with three benthic landers and sediment sampling devices. A total of 39 researchers from 17 institutions in seven European countries are taking part, and SONNE will not enter port for 54 days, the maximum stay at sea for which the ship is designed.

Even answers to these questions will leave large gaps. “Many species in the CCZ are extremely rare; about 90% of the species that we have sampled so far are still unidentified and have no name. And no one knows how many species are still to be discovered,” said Haeckel.

Little is known about how species are connected across the region, either. Many are distributed across the entire CCZ between Mexico and Hawaii, and some across the Pacific, which means genes must be exchanged, but the spatial and temporal steps involved are unknown. Mining that disrupts this connectivity could have immense consequences for the deep-sea ecosystem.

“We are still far from having a complete knowledge of the abyssal ecosystem; for example, we do not know what role the individual species play,” continued Haeckel. “We’re only just beginning to understand the deep sea.”

“This kind of large-scale damage must be prohibited, because we would only notice it, if it is already too late. The benthic ecosystem will not recover on human time scales. While the specific nodule habitat is removed permanently, sedimentary processes will be altered for thousands of years.”

Click here for more from the Oceanographic Newsroom.