A Salty Habitat

Octopuses live in every ocean, and different species have adapted to different marine habitats. As juveniles, common octopuses inhabit shallow tide pools.
No species are known to live in fresh water ^[1]. A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea.
Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out
to the edge of the continental shelf. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf. ^[2]

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Copyright (c) 2004 Richard Ling, CC BY-SA 3.0, via Wikimedia Commons

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate.
Most coral reefs are built from stony corals, whose polyps cluster in groups. Coral reefs flourish in ocean waters that provide few nutrients.
They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas. ^[3]

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Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places,
areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspots. The dispersal of hydrothermal fluids throughout the global ocean
at active vent sites creates hydrothermal plumes. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents.
The Vulcanoctopus hydrothermalis octopus lives near hydrothermal vents at 2,000 m (6,600 ft). ^[4]

Some species are adapted to the cold, ocean depths. The spoon-armed octopus, Bathypolypus arcticus, is found at depths of 1,000 m (3,300 ft).
Although several species are known to live at bathyal and abyssal depths, there is only a single indisputable record of an octopus in the hadal zone;
a species of Grimpoteuthis, dumbo octopus (as pictured above) photographed at 6,957 m (22,825 ft).^[1]

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