Monsters of the deep

Science World, March 25, 2002 by Laura Allen

THERE'S A place on Earth where night and day don't exist. No sunlight penetrates at all. Temperatures are a bone-chilling 2 [degrees] C (36 [degrees] F) all year long. Oxygen is scarce, food scarcer. Pressure crushes from all sides--the equivalent of three tons weighing on every square inch of whatever is bizarre enough to live there.

Its residents? Some are soot-colored, eyes black and beady, with crumpled snouts and gaping mouths--teeth like needles of glass. Others are pale and clammy, with spidery tentacles and wing-like fins.

Welcome to the stuff of nightmares--the deep sea. Specifically, the bathypelagic zone: Though spanning more than 90 percent of Earth's surface, the area from 1,000 to 4,000 meters (3,300 to 13,000 feet) below sea level is more a mystery to scientists than the moon (see diagram, p. 14). The recent discovery of a strange yet apparently common 6.4-m (21-ft)-long squid is proof of scientific ignorance: "That they have not been observed until now indicates how little is known about life in the deep ocean," says cephalopod (squid and octopus) researcher Michael Vecchione at the Smithsonian's National Museum of Natural History in Washington, D.C.

Now researchers hope to shed more light on Earth's darkest realm: Last year, the U.S. National Oceanic and Atmospheric Administration (NOAA) created the Office of Ocean Exploration (OOE), the world's first national program for ocean discovery. In coming months, the OOE plans to launch deep-sea expeditions into never-before-plumbed regions of the bathypelagic--to understand further how the almost-unbearable conditions of Earth's underwater frontier have produced some of the planet's strangest biodiversity imaginable.

EXTREME SQUID

Last year, NOAA researchers piloted the deep-sea submersible ALVIN 1,920 m (6,300 ft) beneath the Gulf of Mexico and aimed a video camera through a porthole. What did they spy? A squid completely unlike any known species: "It has extremely long, slender arms and tentacles with `elbows,' and very large fins extending beyond the end of the body," says Vecchione.

Researchers think this translucent creature feeds by hovering vertically in the water, raising its elbows to dangle 10 sticky 2-m (6.5-ft)-long appendages in a kind of squid "spider web." The arms' suction cups snare shrimp and other prey floating past. Though the mystery squid has been sighted 8 times in the past 13 years, it has yet to be classified or even named--a task left to whomever captures one first.

How can such a delicate, passive creature survive the relentless bathypelagic environment? "If you can stand the first year there, you can stand the next 99," says ichthyologist (fish scientist) Douglas Long at the California Academy of Sciences in San Francisco. The zone may be extreme, but it's also surprisingly stable: Below 100 m (328 ft), surface currents no longer influence the water movement of the open ocean.

Thus, deep-sea currents drag along at a snail's pace. "This zone is also not affected by ocean storms or major temperature changes," Long says. Stagnant bathypelagic waters make for safe meandering by frail creatures that would normally be torn apart by surface waves or foul weather.

What's more, the squid's flabby constitution is actually common among bathypelagic invertebrates (animals without backbones), explains Long. Unlike the upper layers of the ocean, where most fish are fast and muscular, toned muscles aren't necessary in the deep sea. That's because its residents don't often need to flee predators. Since few creatures are adapted to survive in this brutal environment, there simply aren't many predators or prey. "The creatures here aren't that active." Long says. "They don't need much food to survive, and rely on oils or their lack of skeletons to maintain buoyancy."

Bathypelagic beasts with bones tend to contain delicate skeletons at best: "Because it's a nutrient-poor place, it often takes too much energy to produce a skeleton," Long says.

SURVIVAL OF THE MEANEST

The bizarre mystery squid shares the bathypelagic with zone some of Earth's most alien creatures, including anglerfish, razorfish, and dragonfish. Deep-sea female anglerfish (see photo, p. 14) are among the zone's most savage predators. Their expandable jaws open double wide to swallow fish, shrimp, squid, and prey twice their own size. Worse, blade-sharp teeth warp toward the throat to prevent any victim's unlikely escape.

Like many deep-water fish, mate anglerfish skin is grimy black or gray, fragile, and without scales. In fact, their skin is so thin it can slip off their bodies when touched by human hands retrieving them from deep-ocean nets! In the bathypelagic, nature has sacrificed fish scales for a more urgent need: oxygen. Plants, from single-celled algae to huge kelp, produce oxygen in the shallow ocean--but no plants live in the bathypelagic. And oxygen doesn't readily filter down to the deep sea. "Some researchers believe a thin skin increases a fish's ability to absorb oxygen from the water," says Long. The lack of scales also maximizes the skin's available surface area (along with gills) to absorb oxygen.