Scientists gather for census of sea critters

WASHINGTON — A city of brittle stars off the coast of New Zealand, an Antarctic expressway where octopuses ride along in a flow of extra salty water and a carpet of tiny crustaceans on the Gulf of Mexico sea floor are among the wonders discovered by researchers compiling a massive census of marine life.

“We are still making discoveries,” but researchers also are busy assembling data already collected into the big picture of life in the oceans, senior scientist Ron O’Dor said.

The fourth update of the census was released Sunday, before a meeting of hundreds of researchers that begins Tuesday in Valencia, Spain. More than 2,000 scientists from 82 nations are taking part in the project, which is to be completed in 2010.

A discovery that delights O’Dor is that many deep-ocean octopuses share an Antarctic origin. As the Antarctic got colder, ice increased and octopuses were forced into deeper water, he said.

Salt and oxygen are concentrated in the deeper waters, he said. This dense water then flows out, carrying along the octopuses that have adapted to the new conditions, enabling them to spread to deep waters around the world.

Scientists at this week’s sessions will hear about the discovery of what the researchers call a brittle star city off the coast of New Zealand.

The brittle stars, animals with five arms, 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.

Researchers found 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.

Among the other findings being reported at the meeting:

n The mid-Atlantic ridge halfway between America and Europe is home to hundreds of species rare or unknown elsewhere.

n The ridge includes the world’s deepest known active hot vent, more than 13,300 feet deep and populated by anemones, worms and shrimp.

n 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 high.

n The deepest comb jellyfish ever found was discovered at a depth of 23,455 feet 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.

n The White Shark Cafe. Through satellite tagging, scientists discovered 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, which researchers theorize may be significant in either feeding or reproduction.