June 13, 2005 — The long-standing and confounding mystery of where deep-sea scavengers get enough to eat has been solved, say scientists who have spent ten years studying ocean-dwelling, web-spinning creatures called giant larvaceans.

Despite their name, giant larvaceans are small animals with oval trunks and relatively long thin tails that resemble tadpoles.

They live in surface waters in the midst of sticky, mucus webs about a yard in diameter, which they spin to capture food. The webs appear to be discarded daily and then sink to the bottom.

Only after developing a special way to capture the delicate, debris-loaded sinking webs could researchers be sure there was enough stuff in them to comprise the missing 30 percent needed to feed all the creatures of the deep sea.

"We'd seen these in fairly high density at the bottom," said researcher Kim Reisenbichler of the Monterey Bay Aquarium Research Institute.

But how much carbon they brought to the bottom — the basic currency of food — was unknown until they could find a way to capture the sinking webs.

Previous attempts to quantify the amount of carbon reaching the sea floor utilized receptacles not much larger than soup cans, too small and too stationary to catch giant larvaceans' used webs.

It's as if one was trying to find out how much debris came off a dirt road by relying entirely on cans placed along the side of the road, explains biological oceanographer William Hamner of the University of California at Los Angeles.

You'd get dust and dirt in the cans "but if you wanted to find out how many bags of trash were thrown out of windows, you wouldn't see any," Hamner said.

The giant larvacean's webs, or houses, as they are sometimes called by biologists, are those bags of trash. They can be more than yard (a meter) across when in use and inflated by a gentle tail action.

The houses collect organic debris of all kinds from the water, since they are essentially an outer filter for the larvacean, which eats floating organisms and debris under a certain size.

When the house is clogged with debris, the larvacean discards it, possibly once each day, said Reisenbichler. Then the house deflates and takes on a sort of broken parachute, streamer shape as it descends to towards the sea floor at about 2,600 feet (800 meters) per day.

"I think it's hugely important piece of work they have done," said Hamner.

For some time marine scientists and even climate modelers have been trying to discover whether the missing deep sea carbon was the fault of sampling or their calculations.

"The calculations were correct," Hamner concluded. "A (carbon) source was missing."