Worms and Mollusks in Deep Marine Environments
Posted February 1, 1998
Diving in small research submarines called submersibles, biologists are exploring the depths of the oceans and finding unique and previously unknown organisms. A
new segmented worm with a transparent body has been found in the Japan Trench in the Western Pacific. In the Gulf of Mexico, pink segmented polychaete worms have been found living in
ice-like methane hydrate deposits on the ocean floor. Among the surprises found by biologists are the amazing communities that live around deep ocean hydrothermal vents. Hydrothermal
vents are volcanic fissures in the ocean floor where lava and hot gases from Earth's interior flow into the frigid depths of the ocean. Because no light penetrates to these depths, scientists
did not think any life would be found there. However, the food chain in vent communities begins with bacteria that use hydrogen sulfide as an energy source. Although hydrogen sulfide
is toxic to most species, the vent bacteria thrive on it. In turn, the bacteria provide energy for other vent organisms, such as tube worms and mollusks. Scientists are studying these
vent communities to find out how life can exist where no photosynthesis occurs.
The East Pacific Rise is an undersea volcanic ridge 500 miles southwest of Acapulco, Mexico. In 1991 a hydrothermal vent on that ridge exploded, killing the unique
life forms that lived there. Since that time, biologists have been studying the reappearance of life at this hydrothermal vent. Hydrogen sulfide consuming bacteria were the first organisms
to reappear at the vent site. Small tube worms and other invertebrates established themselves next, feeding on the bacteria. Tube worms are segmented worms that anchor themselves by
building tubes that are attached to the sea floor. By 1993, giant tube worms appeared at the site. These worms grow one or two millimeters per day, reaching heights of two meters very
quickly. In 1994, mussels and bristleworms appeared at the site. Scientists are now waiting for the appearance of giant white clams. These clams are thought to be a dominant species
in hydrothermal vent communities. Biologists hypothesize that these clams must colonize the vent at a later stage of development.
References
"A New Denizen of the Deep?" Science, August 8, 1997, Vol. 277, p. 771.
Menon, Shanti. "Deep Sea Rebirth." Discover, July 1997, p. 34.
Mlot, C. "Newfound Worm's World Under the Sea." Science News, August 9, 1991, Vol. 152, p. 86.
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