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Deep-sea mining concerns experts about the impact on marine life by dumping waste in the mid-water zone, one of the most biodiverse in the ocean. Understand the risks
A mid-water zone, a hidden ecosystem that begins 200 meters below the surface and is home to strange, delicate creatures that are essential to the Life on Earth — now threatened by the advance of deep-sea mining.
In this mysterious part of the ocean, divided between the twilight zone and the midnight zone, live animals that are essential to the marine food chain. Whales and valuable fish, such as tuna, depend on them for survival. But this system faces an increasingly real threat: deep-sea mining.
Race for metals on the seabed
Demand for batteries used in electric cars and smartphones is growing at a rapid pace. To meet this demand, mining companies are targeting the depths of the ocean.
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On the seafloor, there are potato-sized polymetallic nodules. They are rich in nickel, cobalt and manganese — metals essential for modern technologies.
These nodules form over millions of years as metals from seawater accumulate around fragments such as shells or shark teeth. One of the most sought-after areas for removal is the Clarion-Clipperton Zone in the Pacific Ocean, southeast of Hawaii.
Tests and plans for commercial mining
Exploratory testing has been carried out on the high seas since the 1970s. In 1994, the International Seabed Authority (ISA) was created to regulate these activities.
However, it was not until 2022 that the first complete nodule collection system was tested in the Clarion-Clipperton Zone, by The Metals Company and Nauru Ocean Resources Inc.
Now, these companies are planning to begin large-scale commercial mining. They are expected to submit formal proposals to the ISA by June 2025. The organization will discuss the issue in July, considering rules, guidelines and benefit sharing.
Fast and controversial process
The mining proposal includes collecting vehicles that scrape the seabed to collect the nodules. This disturbs sediments, destroys habitats and generates waste.
This waste, mixed with water and crushed nodules, is returned to the ocean in the form of mud, creating large plumes in the water column.
The exact depth of disposal is still a matter of debate, with some proposals suggesting disposal at a depth of around 1.200 meters.
However, scientists cautioned that the behavior of these plumes in mid-water is poorly understood. The ocean is constantly moving, with currents that can spread sediments over vast distances.
Risks to life on the seabed
Plumes can directly affect animals living in the mid-water zone. Zooplankton, the base of the food chain in this region, can be affected by particles that clog their respiratory and feeding structures.
Fish and visual predators, which do not have light signals, can also have their behavior altered by water turbidity.
Additionally, gelatinous creatures like jellyfish and siphonophores can suffer from sediment buildup on their bodies. A recent study showed that jellyfish exposed to these materials increased mucus production—a stress trigger—and activated genes linked to wound healing.
An oceanographer who studies zooplankton in the Clarion-Clipperton Zone has expressed concern about the impacts of deep-sea mining on this mid-water ecosystem, which is home to small animals such as zooplankton and micronekton.
The release of sediment plumes can seriously affect these organisms by obstructing respiratory and feeding structures, diluting nutritional resources, and blocking light essential for communication and hunting by bioluminescent species and visual predators.
Another worrying impact is noise pollution. Mining machines emit noise that can disrupt communication and navigation among several species.
Effects on the chain in the ecosystem
Disruptions caused by mining in one part of the ocean can have repercussions far beyond the direct area of impact. A decline in zooplankton numbers, for example, can affect the fish that feed on them, and this spreads throughout the food chain.
The midwater zone also plays an important role in regulating the global climate. Phytoplankton at the surface capture carbon dioxide. Zooplankton consume this material and, through respiration, excretion or death, help transfer it to the seafloor.
This process contributes to carbon sequestration over long periods. Interfering with this cycle can have long-term environmental consequences.
Lack of knowledge about the seabed
Despite growing interest in deep-sea mining, the mid-water zone remains poorly understood. A 2023 study of the Clarion-Clipperton Zone found that between 88% and 92% of the region’s species were new to science.
However, current regulations focus more on impacts on the seabed and do not fully consider the effects on the water column. The ISA’s decisions in July 2025 could define the future of mining in areas like this.
With large-scale operations moving ever closer, the risk of permanent damage increases. Without comprehensive studies of the effects of mining techniques, choices made now could jeopardize an ecosystem that has been poorly exploited.
The mid-water zone, invisible to the human eye, could be the next victim of a new race for resources. And the consequences of this are still unclear.
With information from The Conversation.
