10 November 2008

Deep-sea octopus secrets and more from the Census of Marine Life

Marine marvels revealed in the Census of Marine Life's latest report include a discovery that the ancestor of many of the world's deep-sea octopuses is still alive! It is a shallow-water octopus called Megaleledone setebos, which is only found in the icy Southern Ocean.
Deep-sea octopuses and their common ancestor (clockwise from top left): Pareledone charcoti (image: L.Allcock); Thaumeledone gunteri (image: I.Everson); Adelieledone polymoprha (image: L.Allcock); common ancestor Megaleledone setebos (image: M.Rauschert)

Octopuses apparently spread around the world after Antarctica became covered with a continent-wide ice sheet more than 30 million years ago, a shift that helped create oxygen-rich ocean currents flowing north. When sea ice forms, freshwater freezes, leaving high-salinity, high-oxygen water, which is denser and sinks, flowing into the ocean deeps. This "themohaline expressway" pierced the oxygen-less ocean bottom and the octopuses moved out from the Antarctic into deeper water. The octopuses adapted to the new deep-sea environment. For example, losing their ink sacs because there was no need for this defence mechanism in the pitch black waters.

Other amazing finds include:
  • Brittle stars that have colonized the peak of a seamount — an underwater mountain — where the current flows past at about 2.5 miles per hour. The current delivers such an ample food supply that thousands of stars can capture food simply by raising their arms.

  • A carpet of small crustaceans inhabiting the head of the Mississippi Canyon in the Gulf of Mexico. There are as many as 12,000 of these small crustaceans per square yard.

  • The mid-Atlantic ridge half way between America and Europe is home to hundreds of species rare or unknown elsewhere. The ridge includes the world's deepest known active hot vent, more than 13,300 feet (4,100 meters) deep and populated by anemones, worms and shrimp.

  • Reefs deep in the Black Sea are made of bacterial mats using methane as an energy source. The bacteria form chimneys up to 13 feet (4 meters) high.

  • The deepest comb jellyfish ever found was discovered at a depth of 23,455 feet (7,217 meters) in the Ryukyu Trench near Japan. The discovery raises questions about the availability of food resources at such depths, which had not been thought capable of supporting predators like this one.

  • The White Shark Cafe. Satellite tagging discovers that white sharks travel long distances each winter to concentrate in the Pacific for up to six months. While there, both males and females make frequent, repetitive dives to depths of 975 feet (300 meters), which researchers theorize may be significant in either feeding or reproduction.

  • Algae thriving in Arctic waters of -25 Celsius, kept from freezing because salt concentrations were six times more than in normal sea water.

  • In the eastern South Pacific, a diverse set of giant, filamentous, multi-cellular marine bacteria. They may be "living fossils" that developed in the earliest ocean when oxygen was either absent or much diminished, living on the toxic gas hydrogen sulfide.

  • Another survey found frequent examples of gigantism common in Antarctic waters. The researchers collected huge scaly worms, giant crustaceans, starfish and sea spiders as big as dinner plates.
This is the fourth report from the Census of Marine Life (CoML) since the project began in 2000. A final report will be issued in 2010. The project involves more than 2,000 scientists from 82 nations.

The overarching objectives of the global collaboration between CoML's scientists include:
  • Advancing technology for discoveries
  • Organising knowledge about marine life, and making it accessible
  • Measuring effects of human activities on ocean life
  • Providing the foundation for scientifically based policies
"We are approaching a picture of the oceans ... from micrcobes to whales,"

The $650 million census is on track for completion in 2010, assessing about 230,000 known marine species, a statement said. It has identified 5,300 likely new species, of everything from fish or corals. So far, 110 have been confirmed as new.

Full reports on the wildsingapore news blog.

The Census of Marine Life website has a gallery of photos
and video clips too!

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