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Deep-Sea Mining Concerns Experts About Affecting Marine Life by Dumping Waste in the Water Column, One of the Most Biodiverse Areas of 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, and essential creatures for 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 fundamental to the marine food chain. Whales and valuable fish like tuna depend on them to survive. But this system faces an increasingly real threat: deep-sea mining.
Race for Metals at the Bottom of the Sea
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At the bottom of the sea, there are polymetallic nodules the size of potatoes. They are rich in nickel, cobalt, and manganese — essential metals for modern technologies.
These nodules form over millions of years as metals from seawater accumulate around fragments like shells or shark teeth. One of the most coveted regions for removal is the Clarion-Clipperton Zone in the Pacific Ocean, southeast of Hawaii.
Tests and Plans for Commercial Mining
Since the 1970s, exploratory tests have been conducted in deep-sea environments. In 1994, the International Seabed Authority (ISA) was established to regulate these activities.
However, it was only in 2022 that the first complete system for collecting nodules was tested in the Clarion-Clipperton Zone, by companies The Metals Company and Nauru Ocean Resources Inc.
Now, these companies plan to initiate large-scale commercial mining. They expect to submit formal proposals to the ISA by June 2025. The organization will discuss the topic in July, reviewing rules, guidelines, and benefit-sharing.
Fast and Controversial Process
The mining proposal includes collector vehicles that scrape the seabed to gather the nodules. This stirs up sediments, destroys habitats, and generates waste.
This waste, mixed with water and crushed nodules, is returned to the ocean as sludge, creating large plumes in the water column.
The exact depth of disposal is still a topic of debate. Some proposals suggest releases at around 1,200 meters depth.
However, scientists have warned: the behavior of these plumes in mid-water is poorly understood. The ocean is in constant motion, with currents that can spread sediments over great distances.
Risks to Life at the Bottom of the Sea
The plumes can directly interfere with the animals living in the mid-water zone. Zooplankton, the base of the food chain in this region, can be affected by particles clogging their respiratory and feeding structures.
Fish and visual predators, which do not have luminescent signals, may also have their behaviors altered by the turbidity of the water.
Moreover, gelatinous creatures, like jellyfish and siphonophores, may suffer from sediment accumulation in their bodies. A recent study showed that jellyfish exposed to these materials increased mucus production — an occurrence under stress — and activated genes linked to healing.
An oceanographer studying zooplankton in the Clarion-Clipperton Zone expressed concern about the impacts of deep-sea mining on this mid-water ecosystem, where small animals like zooplankton and micronekton live.
The release of sediment plumes can severely affect these organisms by clogging respiratory and feeding structures, diluting nutritional resources, and blocking light essential for communication and the hunting of bioluminescent species and visual predators.
Another concerning impact is noise pollution. Mining machines emit sounds that can disrupt communication and navigation in various species.
Effects in the Food Chain in the Ecosystem
Disturbances caused by mining in one part of the ocean can have repercussions far beyond the direct area of operation. The decline in zooplankton numbers, for instance, can affect the fish that feed on them, and this cascades throughout the food chain.
The mid-water zone also plays an important role in regulating the global climate. Phytoplankton at the surface captures carbon dioxide. Zooplankton consumes this material and, through respiration, excretion, or death, helps transfer it to the seabed.
This process contributes to carbon sequestration for long periods. Interfering in this cycle can have long-term environmental consequences.
Lack of Knowledge About the Seabed
Despite the growing interest in deep-sea mining, the mid-water zone remains poorly known. A study conducted in 2023 in the Clarion-Clipperton Zone revealed that between 88% and 92% of the species in the region were new to science.
Nevertheless, current regulations focus more on impacts on the seabed and do not fully consider the effects in the water column. The ISA’s decisions in July 2025 may define the future of mining in areas like this.
With large-scale operations increasingly imminent, the risk of permanent damage grows. Without comprehensive studies on the effects of mining techniques, the choices made now may jeopardize an ecosystem that has been poorly explored.
The mid-water zone, invisible to the human eye, may be the next victim of a new rush for resources. And the consequences of this are still unclear.
With information from The Conversation.
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