20130107

The Deep Sea

Because so little is known about the deep sea, compared to habitats on land, scientists are continually discovering new things - some of them very surprising.  Here are some facts from the deep ocean.
  • The oceans cover two-thirds of the Earth's surface to an average depth of almost 4km.  The deepest point discovered so far is almost 11km deep.
  • The oceans provide about 190 times as much living space as all of the Earth's other environments - soil, air and fresh water - put together.
  • Life on Earth almost certainly originated in the sea and was more or less restricted to the oceans for the first 3 billion years of evolution.
  • The giant squid, Architeuthis dux, has the largest eyes of any animal on Earth. They are up to about 30cm across - the size of a dinner plate.
  • The record for the deepest fish goes to Abyssobrotula galatheae, a member of Ophidiidae family. It was dredged from the bottom of the Puerto Rico Trench at a depth of 8,368m in 1970.
  • The largest known deep sea fish is the Greenland shark, Somniosus microcephalus, which grows to over 7m in length.  However, it doesn't spend all its time in the deep sea. It also comes up to the surface to eat offal thrown overboard from fishing boats.
  • Life in the sea is incredibly rich.  There are creatures from 28 major groups of animals living in the sea, including sponges, crustaceans and molluscs, whereas only 11 major groups of animals live on land.

Amazing Facts

Of the estimated 500,000 to 10 million species living in the deep sea, the majority are yet to be discovered.
Approximately 98 percent of the oceans' species live in, on or just above the floor of the sea.
The estimated number of seamounts ranges from 30,000 to 100,000.
Seamounts are home to a breathtaking array of species (for example, over 850 species were recently found on seamounts in the Tasman and Coral Seas).
15 percent or more of the breathtaking array of species being found on seamounts may be endemic, meaning that they are unique to that area. Because of this, each unsampled seamount is a potential source of numerous undiscovered species. The Coral and Tasman Sea seamounts have endemism rates of about 30 percent
Two-thirds of all known coral species live in waters that are deep, dark, and cold — some live three miles deep and are able to survive in -2°C.
Some cold-water corals are 5,000-8,500 years old or more, and some grow into beautiful structures that rise up to 35 meters high.
Deep-sea corals, sponges and other habitat-forming organisms provide protection from currents and predators, nurseries for young fish, and feeding, breeding, and spawning areas for hundreds of thousands of species.
Commercially important deep-water fish and crustacean populations found in the high seas include crabs, shrimp, cod, Pacific cod, orange roughy, armorhead, grenadier, Patagonian toothfish (aka Chilean sea bass), jacks, snappers, porgies, sharks, groupers, rockfish, Atka mackerel, and sablefish.
Deep-sea species tend to be slow growing, late maturing and low in reproductive capacity. Many deep-water fish species live 30 years or more. Some, such as orange roughy, can live up to 150 years.
Because deep-sea species live in rarely disturbed environments and tend to be slow growing, late maturing and endemic, they are exceptionally vulnerable to extinction.
Deep-sea coral and sponge communities are largely untapped sources of natural products with enormous potential as pharmaceuticals, enzymes, pesticides, cosmetics, and other commercial products, for example:
  • Gorgonian corals produce antibiotics; compounds found in certain deep-sea sponges are potent immunosuppressive and anti-cancer agents;
  • some coral species contain the pain-killing compounds known as pseudopterosians;
  • seafans contain high concentrations of prostaglandins (compounds used to treat asthma and heart disease).
Ancient deep-sea corals provide valuable records of climate conditions that may assist our understanding of global climate change.

More information:

24 Sep 2004 - Mysteries and Mountains of the Deep Sea - Conserving Deep-Sea Biodiversity and Habitats, pdf; 4 pages; 607 KB (English | English US standard | Spanish)

FACTS ABOUT THE DEEP SEA ENVIRONMENT


  • It's deep: average depth of ocean is 3,800 m; deepest trenches reach ~11,000 m.
  • Ergo, hydrostatic pressures are high: pressure increases by 1 atmosphere for each 10 m increase in depth - pressures may reach ~1,100 atmospheres.
  • Temperatures are low: only a few degree above 0 degrees Centigrade in most regions.
  • Temperatures are low: only a few degree above 0 degrees Centigrade in most regions.
  • Hydrothermal vent temperatures may be high, up to ~ 400 degrees Centigrade.
  • It's dark.
  • It may be very low in oxygen (oxygen minimum layers)
  • But...despite all of this...life goes on there.