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  • Approximately 98% of ocean species live in, on, or just above the seafloor.

  • Creatures living near deep-sea hydrothermal vents are unlike any other form of life. They don’t rely on the sun for their energy but on chemicals being pumped from below the Earth’s crust, and they convert these chemicals to energy via a process known as chemosynthesis.

  • Deep-sea life has evolved to live within a hostile environment of extreme pressure, no sunlight, low food availability, and freezing temperatures – or in the case of hydrothermal vents, very high temperatures. These conditions mean many deep-sea species take a long time to reach sexual maturity, grow very slowly, and may live for hundreds of years, making them extremely vulnerable to even just a small change in their environment or to damage caused by human activities – the impacts of which may be irreversible.

  • The mineral-rich fluid emitted from hydrothermal vents can be at temperatures as high as 400 °C (750 °F). Nevertheless, the species which inhabit these unique ecosystems – such as crabs, clams and tube worms – are adapted to survive and thrive in this extreme environment. 

  • What happens on the deep seabed affects the ocean surface. Deep-sea life supports a complex ocean food web. Many twilight-zone inhabitants migrate to the surface every night to feed, as part of the largest migration on Earth.

  • Over half of all known coral species live in deep cold waters. Cold-water corals can live for thousands of years and grow into beautiful structures that can rise 35 meters high.

  • Some deep-water fish species like the orange roughy can live for up to 150 years, while a deep-sea black coral found in Hawai’ian waters in 2004 was estimated to be 4,265 years old.

  • Quite recently more than 20,000 underwater mountains were discovered in the deep!

  • Certain coral species produce compounds used in antibiotics and painkillers, while compounds found in certain deep-sea sponges are potent immunosuppressive and anti-cancer agents. 

  • Studies have also found that compounds found in the deep sea could be key to fighting pandemics; for instance, one of the tests used to diagnose coronavirus was developed from a microbe found in hydrothermal vents. 

  • Seafans contain substances used to treat asthma and heart disease.

  • The female Casper octopus, only discovered in 2016, wraps her body around her eggs on the deep seabed, often onto a manganese nodule – a lump of rock containing precious metals. She will protect her eggs until they hatch, which can take several years, and often starves to death in the process. 

  • The recently discovered scaly-foot snail, which lives alongside deep-sea hydrothermal vents, is literally iron-plated – the only known creature that has iron sulphide in its skeleton and shell. 

  • Endemism is high in the deep sea, with many species found only in a specific habitat and region. 

  • The mesopelagic zone, between 200 meters and 1,000 meters below the ocean’s surface, is estimated to be home to 95% of the world’s fish biomass. 

  • Cuvier’s beaked whale (Ziphius cavirostris) is the world’s deepest diving whale: it has been recorded at an incredible depth of 2,992 meters. 

  • The deep sea is home to the “impossible fish”, or snailfish, which broke the record for living at a depth of 8,336 meters.

  • The deep-dwelling anglerfish has a very strange mating ritual in which the male, who is much smaller than the female, bites onto the female’s body, where he remains for the rest of his life, serving only as a sperm bank for when the female is ready to spawn.