The potential effects of mining-generated sediment plumes and noise on pelagic taxa. Organisms and plume impacts are not to scale. See text for explanation of effects. Connections between seafloor vehicles and surface ships are only shown for nodule mining. Source: Drazen, et al. (2020).


Deep seabed mining targets three deep sea habitats for the metals and minerals associated with these ecosystems: hydrothermal vents, seamount crusts, and polymetallic nodules.

Each proposed type of deep seabed mining would destroy the target habitats and lead to unavoidable and large-scale species loss. Most of the threatened unique and unusual species have yet to be discovered. Extensive habitat destruction would include polymetallic nodules and seamount crusts, which take millions of years to form and will not recover in human time scales.

Permitting of deep seabed mining in the territorial waters of nation states may occur by individual countries. Papua New Guinea issued the first permit for seabed mining, of hydrothermal vents, to Canadian company Nautilus Minerals. Nautilus went bankrupt in 2019 before mining could begin. Mining in international waters, the Common Heritage of Humankind, can only be permitted by the International Seabed Authority. To date 31 permits have been granted by the International Seabed Authority for mining exploration in international waters. On June 25, 2021, the small Pacific island nation of Nauru triggered a “two year rule” that requires the International Seabed Authority to complete within two years the regulations necessary to approve plans of work by companies to permit deep seabed mining to begin. If the regulations have not been completed in two years – by June 2023 – the ISA can be asked to approve mining permits on the basis of whatever draft regulations are in place at the time. Nauru is the sponsoring state for the Canadian mining company The Metals Company.

Nauru has indicated that its subsidiary Nauru Ocean Resources Inc (NORI) will be ready to apply for a mining permit shortly after June 2023.


Map of ISA deep seabed mining exploration concessions

Source: ISA Exploration Areas. Click to enlarge

Global locations of targeted deep seabed habitats

Source: Front. Mar. Sci., 10 January 2018. Click to enlarge


Hydrothermal vents are most commonly found at depths of 2.5 – 5 km undersea.

They often form along tectonic plate boundaries and resemble underwater volcanoes.  They spew hot, acidic, and metal-rich fluid up through the seafloor. As this fluid cools the dissolved minerals precipitate out, harden and create the hydrothermal vent chimneys.

Hydrothermal vents are unique ecosystems, with extremes of both hot and cold temperatures. They exist at depths where there is no sunlight and immense water pressure. The chemicals spewing out through the vents would be toxic for most terrestrial species.

And yet, hydrothermal vents are home to a great diversity of organisms that only live on and near deep-sea vents and are found nowhere else on earth. Over 600 species have been identified so far. Including unique tube worms, clams, mussels, crabs and shrimp.

Amazingly, these creatures feed on vent organisms, microbes, which derive energy from the chemicals coming from the vents, via chemosynthesis, rather than through photosynthesis from sunlight. It is thought that life on earth may have started at such vents.


Seamounts are underwater mountains found at depths of 800 meters to 2.5 km.

As seamounts span the biodiverse midwater zone of the ocean, they are characterized by very rich associated biodiversity that also serves as a source of food for many migratory species such as sharks and tuna. These seamounts are targets for mining because they are covered in cobalt-rich ferromanganese crusts.



Most polymetallic nodules are between 2-10 cm in size and are found on the seabed surface of the abyssal plains of the ocean at the great depths of 4-6 km below the surface.

Most of the permits that have been granted by the International Seabed Authority to date for exploration in international waters, 19 out of 31 permits, are for mining of polymetallic nodules, primarily in the Clarion Clipperton Zone in the Pacific Ocean. The Clarion-Clipperton Zone spans 4.5 million square kilometers between Hawaii and Mexico.

Like seamount crusts, polymetallic nodules grow extremely slowly. It is believed to take millions of years for one centimeter of growth. They form as dissolved metals in seawater precipitate out around a small object on the seafloor, such as a fish tooth.

While it used to be believed that the abyssal plains of the ocean were devoid of life, it is now understood that individual polymetallic nodules are themselves ecosystems as they host various microbes and a wide variety of deep seabed organisms. The nodules form the substrate for an ecosystem of highly vulnerable abyssal creatures, which are themselves connected to the web of life in the water column above them.

It was recently hypothesized that million-year-old nodules remain at the surface of the seabed through the activity of star fish, octopods and molluscs that forage on and around the nodules leading one deep sea scientist, Dutkiewicz, to conclude that “deep sea ecosystems and nodules are inextricably connected.”

Like many of the species found on and around seamount crusts the species found on polymetallic nodules are characterized by extremely slow growth rates, delayed sexual maturity, and by producing relatively few offspring. They are particularly vulnerable to disturbance, recovering very slowly, if at all.


These machines were built by Canadian mining company Nautilus for mining hydrothermal vents in Papua New Guinea at the Solwara 1 site in the Bismarck Sea.

This is a 25 tonne small-scale test machine for mining polymetallic nodules belonging to the mining company GSR.


Mining machines and prototypes have been built and tested for mining hydrothermal vents and polymetallic nodules.

Suctioning up polymetallic nodules will not only remove, effectively forever, the substrate for life on the seabed and associated life in the water column above it, but it will also create large plumes of sediments both in front of and behind the machine as it traverses the seabed. These thick sediment plumes are expected to smother marine life far beyond the mined area by travelling vertically and horizontally over potentially great distances.

After initial processing on board the ship, sediment and metal-rich effluent will be piped back down and dispersed, likely in the biodiverse-rich midwater zone.  These sediment plumes moving both horizontally and vertically from the pipe outfall are expected to put species in their path at risk over potentially great distances.                          

This midwater region connects deep sea ecosystems and the ocean surface and represents more than 90% of the biosphere. It contains fish biomass 100 times greater than the global annual fish catch, which scientists say is at risk from deep seabed mining (Drazen et al., 2020).

Among the other predicted impacts are the compression of the sea bottom leading to further organism loss, light pollution in an otherwise perpetually dark parts of the ocean, and harmful noise pollution, which will occur as a result of operations of surface vessels, as well as mining of the seabed and through the riser pipes that will affect all levels of the ocean in between.  Noise will be generated by pumps and impellers driving the suction of material through the riser pipes, as well as broadband transport sounds by the movement of sediments and ore through the riser pipes (OceanCare 2021).