Picture an oceanic realm so deep and dark that it resembles another planet, where bioluminescent creatures endure immense pressure. This is the midwater zone, an obscure ecosystem starting 650 feet (200 meters) beneath the ocean’s surface, sustaining life across the Earth. It encompasses the twilight and midnight zones, inhabited by unique and fragile animals. This area supports species like whales and commercially significant fish such as tuna, which rely on its inhabitants for nourishment. However, this ecosystem is facing significant threats.
With rising demand for materials needed in electric car batteries and smartphones, mining companies are shifting their focus to the deep sea, where valuable metals like nickel and cobalt are found in potato-sized nodules on the ocean floor. Research and experimentation over the past 40 years have shown that extracting these nodules can put seafloor organisms at risk by disrupting their habitats. Additionally, deep-sea mining activities pose a danger to the midwater ecosystem. If proposed deep-sea mining operations release sediment plumes into the water column, the debris could interfere with animal feeding, disturb food webs, and alter behaviors.
As an oceanographer researching marine life in a nodule-rich area of the Pacific, one believes it is crucial to understand these risks before countries and companies rush to mine. The question remains: Is humanity willing to endanger poorly understood parts of an ecosystem for essential future resources?
Beneath the Pacific Ocean southeast of Hawaii lies the Clarion-Clipperton Zone, home to polymetallic nodules scattered across the seafloor. These nodules form as metals in seawater or sediment gather around nuclei such as shell fragments. Growing only a few millimeters per million years, they contain metals like nickel, cobalt, and manganese, which are crucial for batteries, smartphones, wind turbines, and military hardware.
As demand for these technologies soars, mining companies are targeting the Clarion-Clipperton Zone and a few other similar areas around the globe. So far, only test mining has occurred, but plans for full-scale commercial mining are progressing rapidly.
Exploratory deep-sea mining commenced in the 1970s, with the International Seabed Authority being established in 1994 under the United Nations Convention on the Law of the Sea to regulate the practice. In 2022, The Metals Company and Nauru Ocean Resources Inc. fully tested the first integrated nodule collection system in the Clarion-Clipperton Zone. The companies are now planning large-scale mining endeavors in the region.
As the International Seabed Authority deliberates regulations, The Metals Company has appealed to President Donald Trump and praised his directive on April 24, 2025, to expedite U.S. licenses for seabed mining outside national waters, in accordance with the Deep Seabed Hard Mineral Resources Act. The U.S., which never ratified the U.N. Convention on the Law of the Sea, established its own licensing system, a move strongly opposed by the ISA.
Several nations have called for a halt to seabed mining until better comprehension of the risks is achieved.
The mining process involves collector vehicles scraping the ocean floor to collect nodules, stirring up sediments and eliminating habitats vital for marine life. This activity poses a threat to biodiversity and may cause irreversible damage to seafloor ecosystems. Once gathered, nodules, seawater, and sediments are transported through a pipe to a ship for separation from waste.
The remaining slurry—water, sediment, and crushed nodules—is then dumped back into the water column, creating plumes. While the discharge depth is currently under discussion, some mining operators suggest releasing waste at midwater depths, around 4,000 feet (1,200 meters). However, the behavior of these mining plumes remains uncertain in the dynamic ocean environment.
These sediment clouds could spread over vast areas, potentially damaging marine life and disrupting ecosystems. Imagine a volcanic eruption of fine sediments throughout the water column, affecting everything in its path.
As an oceanographer studying zooplankton in the Clarion-Clipperton Zone, there is concern about deep-sea mining’s impact on the ecologically significant midwater zone. This ecosystem supports zooplankton, tiny drifting animals, and micronekton, including small fish, squid, and crustaceans that depend on zooplankton for sustenance.
Sediment plumes could harm these animals, with fine sediments clogging respiratory and feeding structures and diluting food sources. Additionally, plumes might obstruct light, affecting bioluminescent organisms and visual predators.
Jellyfish and siphonophores, which are delicate creatures, could experience buoyancy issues due to sediment accumulation. Recent studies indicate that exposure to sediments causes jellyfish to increase mucous production—a stress response that burdens their energy reserves—and express genes associated with wound repair.
Noise pollution from machinery may also interfere with species communication and navigation. Such disturbances could disrupt ecosystems and affect fish and marine animal populations dependent on zooplankton for food.
The midwater zone plays a crucial role in climate regulation. Phytoplankton at the ocean’s surface capture atmospheric carbon, which moves through the food chain as zooplankton consume it. When these organisms respire, excrete waste, or sink, they contribute to carbon storage in the deep ocean, sequestering carbon dioxide for centuries.
Despite growing interest in deep-sea mining, much of the deep ocean, particularly the midwater zone, remains largely unexplored. A 2023 study in the Clarion-Clipperton Zone found that 88% to 92% of species are new to science. Current mining regulations primarily address the seafloor, overlooking broader ecosystem impacts. The International Seabed Authority is preparing to make key decisions on future seabed mining in July 2025, addressing issues like mining waste, discharge depths, and environmental protection.
These decisions could shape the framework for extensive commercial mining in ecologically critical areas like the Clarion-Clipperton Zone. Without thorough impact studies on seafloor mining techniques, irreversible damage to these fragile ecosystems is a significant risk.
This article, first published on March 25, 2025, has been updated to include Trump’s order to expedite mining licenses.