Seafloor Fauna

By Dr. Sherwood B. Idso

Imagine yourself descending through the depths of the sea in a submarine with windows of thick glass. As you submerge and begin your descent, you see schools of small fish darting about, occasionally startled by a larger fish such as a shark prowling about for a meal. Down and down you go, and your sightings become less and less frequent. After a while you are not able to see at all, as the sunlight that strikes the surface is completely filtered out by the water above you.

Descending still further, you begin to notice the eerie fluorescence of deep-sea creatures that inhabit the depths of perpetual midnight. But your voyage is not yet ended. Down you go again. One mile, two … down to where no life can possibly survive—or can it?

In February and March of 1977, a team of geologists and chemists made twenty-four deep dives off the coast of Ecuador at a site known as the Galapagos Rift. This is a “spreading center,” where new ocean floor material is being formed from undersea volcanic activity. The scientists went down in search of hot spots along the rift, where they could observe the crust’s creation process in action. To their delight, they were successful in locating five warm-water vents, spewing out a milky white fluid that shimmered in the gleam of their spotlights. But equally exciting—and even more unexpected—they were greeted with a view of a whole new undersea ecosystem or community of living things.

They saw giant clams and mussels, crabs, seaworms, and limpets of new and varied forms. There were fields of red-tipped tubeworms waving in the turbulent waters surrounding the vents. It was a biologist’s dream to see species never before seen by man. Indeed, never before even imagined to exist!

Think of the basic requirement of all animal life—food. On land and in waters where sunlight penetrates, the ultimate source of all food is the process of photosynthesis, whereby plants combine raw materials in their environment to form the basic building blocks of life. But lacking the all-important ingredient of sunlight here in the depths of the sea, this process cannot operate. So how do these exotic communities of animals sustain themselves?

The answer was found in laboratory work performed on some of the animals retrieved for study. Living in the stomachs of many of them was a special type of bacteria capable of producing food by a completely different means and concentrating nutrients from the mineral-rich waters coming out of the undersea vents.

Are such deep-sea animal communities as these unusual? The scientists wondered about this question, and so they set off to investigate another area of seafloor spreading near the mouth of the Gulf of California. The rate of crustal formation there was greater; and the vents found were much larger and more violent. Whereas the warm water from the Galapagos Rift vents measured about 20 degrees centigrade, that spewing out of the Gulf of California vents measured 350 to 400 degrees centigrade. It was so hot that the first attempt to measure it actually melted the submarine’s heat probe!

Upon contacting the much colder surrounding water (near 2 degrees centigrade), the hot geysers deposited their dissolved minerals in large clumps rich in copper, iron, zinc, sulfur, cobalt, lead, silver, etc. And clustered in groups interspersed among these clumps were magnificent communities of creatures like those previously observed at the Galapagos Rift. But these were even more spectacular, with red-tipped tubeworms growing to lengths of ten feet or more.

So what does the future hold? Scientists are now planning an expedition to yet another seafloor spreading center near Easter Island, whose rate of crustal formation is three times faster than those previously studied. Who knows what surprises await them in Heavenly Father’s magnificent and wonderful undersea world? We will all be looking forward to their discoveries with great anticipation.

Illustrated by Shauna Mooney

The research submarine Alvin on a dive to the sunless depths of the sea.

A “black smoker” or hot water vent erupts into the cold waters of the ocean bottom. (Photo by Robert Ballard, WHOI.)

The submarine Alvin returns to its mother ship Lulu after a dive. (Photo by Lawrence Shumaker, WHOI.)

The camera system that was used by the scientists to locate the hot water vents was towed along the ocean bottom and returned about 70,000 photographs. (Photo by David Clark, WHOI.)

A fish moves among the mounds of mineral deposits surrounding a hot water vent. Several shells are also scattered about the area. (Photo by Ruth Turner, WHOI.)

A colony of giant red-tipped tubeworms never before seen by man. (Photo by Jack Donnelly, WHOI.)

On board the research vessel Lulu, a scientist examines one of the long tubeworms returned for study. (Photo by Jack Donnelly, WHOI.)