Explorers catalog life three miles beneath the sea

Posted by Emma Woollacott

Census of Marine Life scientists have carried out an inventory of deep sea creatures, recording a staggering 17,650 species living as deep as three miles.

Revealed via deep-towed cameras, sonar and other vanguard technologies, the creatures recorded range from crabs to shrimp to worms. Most have adapted to diets based on meager droppings from the sunlit layer above, others to diets of bacteria that break down oil, sulfur and methane, the sunken bones of dead whales and other implausible foods.

Explorers inventory life three miles beneath the seaOne of the weirdest species, found at depths of 1,000 to 3,000 meters, is a rare, primitive animal known as a cirrate or finned octopod. It's been dubbed the Dumbo, because it flaps a pair of large ear-like fins to swim, rather like the cartoon flying elephant.

The jumbo Dumbo netted by Census explorers was estimated to be nearly two meters long and, at 6kg, the largest of only a few specimens of the species ever obtained.

Altogether, nine species of gelatinous Dumbos were collected on the Mid-Atlantic Ridge, including one that may be new to science.

Another surprise came when an ordinary-looking tubeworm was scooped by a robotic arm from the ocean floor - crude oil streamed from both the animal and the open hole. The "wildcat" tubeworm had hit a gusher and was dining on chemicals from decomposing oil.

Sampling at great depths depends on high tech instruments such as remotely operated vehicles, autonomous underwater vehicles and submarines, as well as trawls, cores and dredges that need several kilometers of cable to reach the seabed.

Says Mireille Consalvey of the New Zealand National Institute of Water and Atmospheric Research, CenSeam project manager, "Every deployment is a trip into the unknown, with often seasick scientists struggling to work amid high winds and 10 meter swells."

But the census-takers weren't the only visitors from above. A southern elephant seal tagged by Census project TOPP was recently discovered to have dived down an extraordinary mile and a half from the surface.

The collective findings are still being analyzed for release as part of the final Census report to be released next October.