What’s happening? Nearly two-thirds of the hundreds of mollusc species in the deep ocean could face extinction due to deep-sea mining, according to a study from Queen’s University in Belfast. The research has seen dozens of mollusc species living close to hydrothermal vents added to the red list of threatened species published by the International Union for the Conservation of Nature (IUCN). The researchers have said mining could also lead other species dependent on the vents to face extinction risk.

Why does this matter? The deep sea is the largest biome on the planet, comprising varied geomorphological features and habitats – from canyons and seamounts to cold seeps and brine pools. Hydrothermal vents, first discovered in 1977, can be found at a depth of 1,000 to 4,000 meters and play an important role in regulating ocean chemistry. They occur at volcanically active mid-ocean ridges, where seawater enters the Earth’s crust and gets heated up to 400C by hot magma. During the process, the water absorbs minerals such as copper, iron, zinc or cobalt from surrounding rocks before exiting via vent openings as hot, mineral-rich fluids. The contact with cold seawater leads to a chemical reaction and the formation of solid mineral deposits.

With about one-fifth of the global ocean floor mapped, scientists have discovered 600 hydrothermal vent sites, each hosting an abundance of diverse life forms. In the absence of sunlight, endemic microbes convert CO2 into sugar using chemical energy from the vent fluids – a process called chemosynthesis – which forms the basis for symbiotic relationships with larger organisms such as shellfish or tubeworms. These animals attract predators including crabs, zoarcid fish and octopuses, turning the vents into biodiversity hotspots.

Hydrothermal vent structures – also known as seafloor massive sulphides – are one of three types of deep-sea mineral deposits under consideration for commercial exploitation, alongside cobalt-rich seamount crusts and polymetallic nodules on abyssal plains. Researchers have now warned that mining poses a substantial threat to these unique ecosystems. Of 184 mollusc species found near hydrothermal vents, 62% were classified as threatened, while only 25 species were fully protected from extraction activities through local conservation measures. In the Indian Ocean, every single mollusc species was listed as threatened.

The new study is not the first to warn about the consequences of industrial-scale deep-sea mining. Others have pointed out that the destruction of seafloor habitat, the release of toxins and sediment plumes, as well as the noise and light pollution associated with deep-sea mining could have catastrophic long-term impacts on sensitive and under-researched ecosystems. Large-scale impacts on these ecosystems would also have implications for climate change mitigation: scientists have estimated that deep-sea bacteria could fix up to 200 million mt of CO2 in the oceans per year.

Although countries like Japan, South Korea and Papa New Guinea have started mining resources in territorial waters, the vast majority is located in international waters beyond national jurisdiction, which have not been opened to large-scale extraction. This area, estimated to contain more valuable metals than all continents combined, is governed by the International Seabed Authority (ISA) under the UN Convention on the Law of the Sea. As of May 2021, the ISA has issued 31 exploration licenses to advance the development of machines and extraction methods. By June 2023, the organisation is due to finish the underwater Mining Code, a regulatory framework setting out technical and environmental standards for the mining of materials used to produce green energy technology and electric vehicles.

Meanwhile, more than 600 marine science and policy experts, backed by the European Parliament and the IUCN, have called for a global moratorium on deep-sea mining.

Sources: Frontiers in Marine Science; The Guardian