Black smoker
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Black smokers are a type of hydrothermal vent found on the ocean floor. Generally hundreds of meters wide, black smokers are formed when superheated water from below the Earth's crust comes through the ocean floor. They are rich in dissolved minerals from the crust, most notably sulfides, which crystallize to create a chimney-like structure around the vent. When the superheated water in the vent comes in contact with the frigid ocean water, many minerals are precipitated, creating the distinctive black color. The metal sulfides that are deposited can become massive sulfide ore deposits in time.
Black smokers were first discovered in 1977 around the Galapagos Islands by the National Oceanic and Atmospheric Administration. They were observed using a small submersible vehicle called Alvin. Today, black smokers are known to exist in the Atlantic and Pacific Oceans, at an average depth of 2100 meters. The temperature of the water they vent can reach 400 °C, but does not boil due to the high pressure it is under at that depth. The water is also extremely acidic, often having a pH value as low as 2.8 — approximately that of vinegar.
Although life is very sparse at these depths, black smokers are the center of entire ecosystems. Sunlight is nonexistent, so many organisms — such as archaea and extremophiles — must convert the heat, methane, and sulfur compounds provided by black smokers into energy through a process called chemosynthesis. In turn, more complex life forms like clams and tubeworms feed on these organisms. The organisms at the base of the food chain also deposit minerals into the base of the black smoker, thus completing the life cycle.
New and unusual species are constantly being discovered in the neighborhood of black smokers: for instance, the Pompeii worm in the 1980s, and, in 2001, during an expedition to Indian Ocean's Kairei hydrothermal vent field, an armor-plated gastropod. The latter uses iron sulfides (pyrite and greigite) for the structure of its dermal sclerites (hardened body parts), instead of calcium carbonate. The extreme pressure of 2500 m of water (approximately 25 megapascals) is thought to play a role in stabilizing iron sulfide for biological purposes. This armor plating probably serves as a defense against the venomous radula (teeth) of predatory snails, co-existing in the same community. This snail, which is unique in its kind, has not yet been named.
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See Also
Reference
- Van Dover et al., Biogeography and Ecological Setting of Indian Ocean Hydrothermal Vents, Science 2001 0: 10645741-1
- Cindy Lee Van Dover : The Ecology of Deep-Sea Hydrothermal Vents. Princeton University Press 2000