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Photo, caption follows:

Pictured is a colony of giant tubeworms with vent fish and crabs, all highly specialized for and found only in the extreme environment of the hydrothermal vent ecosystem.
Credit: Richard Lutz, Rutgers University; Stephen Low Productions; Woods Hole Oceanographic Institution.

Title: How Can Organisms Live Without Sunlight?
Scientists once thought sunlight, like water, was crucial to sustain life on Earth. But we now know of deep-sea communities of organisms that use chemical energy, rather than energy from sunlight, as the basis for their food. Communities of bacteria that tap the energy in hydrogen sulfide molecules, for example, cluster around deep-sea hydrothermal vents. There, such bacteria are the primary producers that provide key nutrients other organisms depend on.

At the vents, water seeping under the ocean floor picks up dissolved minerals and nutrients. Undersea volcanic activity superheats the water where new crust is being formed. After seeping through cracks in the Earth’s crust and reaching a temperature of almost 600 degrees Fahrenheit, the acidic water dissolves minerals, such as hydrogen sulfide, from surrounding rocks. Finally, according to scientists affiliated with NSF’s Ridge 2000 project, the hot mineral-laden water is spewed back out into the surrounding cold ocean waters.

Researchers wanted to learn how hydrothermal-vent organisms live deeper in the oceans than sunlight can possibly reach. Bacteria-like organisms, called Archaea, have developed a unique means of converting hydrogen sulfide into food by a process called chemosynthesis, which makes them the producers that sustain a diverse community of animals at the vents.

Each hydrothermal vent differs in the number and type of creatures found there, but most are composed of

  • Archaea, which produce sugars needed for life through chemosynthesis, and live within tubeworms and mollusks, in turn providing these animals with a food source
  • fish, crabs, shrimp and octopi that prey on the tubeworms and mollusks

These incredible ecosystems extend along the sea floor only in the reaches of a vent’s hydrogen-sulfide plume because inhabitants need concentrated chemicals to thrive.

Even more unbelievably, NSF-supported scientists have discovered that much of our planet’s biodiversity may exist under the sea floor, as microbes that live in the spaces between grains of sediment.

To learn more:

How do long-term changes affect Earth's ecosystems? [Next]