Wildlife
The deep ocean begins where the continental shelves and their shallow waters give way to the dark depths where little or no sunlight penetrates. Here, in the layer underneath the sunlit open oceans, live some of the most bizarre and highly adapted creatures on the planet. With no plants or algae here to photosynthesize and form the base of the food chain, life here is largely dependent on the dead material and droppings that sink down from above.
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Twilight zone
Descending 200 meters into the deep sea reveals some weird and wonderful creatures.
Descending 200 meters into the dark of the deep sea reveals some weird and wonderful creatures.
Fossil life
Swimming up from the deep ocean, a young chambered nautilus is an incredible living fossil.
Eight hundred metres below sea level, a living fossil lurks. The chambered nautilus is an ancient relative of the squid and the octopus. It migrates upwards from these depths every night to feed on the tiny shrimp by the Great Barrier Reef wall, returning back to the darkness during the day. This clip shows the first images of a baby chambered nautilus, no bigger than a two pound coin, as it propels itself forward by squirting water.
Scavenger swarm
Marine invertebrates gather to feast on a food bonanza.
Three-foot nemertean worms and carnivorous sea stars prowl the Antarctic in search of flesh. Finding a dead seal, the sea stars inject it with digestive juices... then suck it up like soup.
Light lures
Bioluminescence creates pyrotechnic displays deep in the ocean's darkness.
Bioluminescence creates pyrotechnic displays deep in the ocean's darkness. Shots courtesy of WHOI
Tricks of light
Shedding bioluminescent light on the situation can work as defence.
Shedding bioluminescent light on the situation can work as defence.
The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms (1800 m) or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter produced in the photic zone. For this reason scientists once assumed that life would be sparse in the deep ocean but virtually every probe has revealed that, on the contrary, life is abundant in the deep ocean.
In 1960 the Bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at 35,798 feet or 6.77 miles (10,911 meters), the deepest spot in any ocean. If Mount Everest were submerged there, its peak would be more than a mile beneath the surface. At this great depth a small flounder-like fish was seen moving away from the bathyscaphe's spotlight. The Trieste was retired and for a while the Japanese remote-operated vehicle (ROV) Kaikō was the only vessel capable of reaching this depth. It was lost at sea in 2003. In May and June 2009, the hybrid-ROV (HROV) Nereus returned to the Challenger Deep for a series of three dives to depths exceeding 10900 meters.
It has been suggested that more is known about the Moon than the deepest parts of the ocean. Until the late 1970s little was known about the extent of life on the deep ocean floor but the discovery of thriving colonies of shrimps and other organisms around hydrothermal vents changed that. Before the discovery of the undersea vents, it had been accepted that almost all life on earth obtained its energy (one way or another) from the sun. The new discoveries revealed groups of creatures that obtained nutrients and energy directly from thermal sources and chemical reactions associated with changes to mineral deposits. These organisms thrive in completely lightless and anaerobic environments, in highly saline water that may reach 300 °F (150 °C), drawing their sustenance from hydrogen sulfide, which is highly toxic to almost all terrestrial life. The revolutionary discovery that life can exist under these extreme conditions changed opinions about the chances of there being life elsewhere in the universe. Scientists now speculate that Europa, one of Jupiter's moons, may be able to support life beneath its icy surface, where there is evidence of a global ocean of liquid water.
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Useful behaviours for this habitat
Ecozones where this habitat is found
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Antarctic minke whale
Narwhal
Rorquals
Sperm whale
Cartilaginous fish
Sharks
Basking shark
Mackerel sharks
Anglerfish
Ray-finned fishes
Lobe-finned fishes
Humboldt squid
Hermit crabs