Black smoker

A black smoker or sea vent, is a type of hydrothermal vent found on the ocean floor. They are formed in fields hundreds of meters wide when superheated water from below Earth's crust comes through the ocean floor. This water is rich in dissolved minerals from the crust, most notably sulfides. When it comes in contact with cold ocean water, many minerals precipitate, forming a black chimney-like structure around each vent. The metal sulfides that are deposited can become massive sulfide ore deposits in time.

Black smokers were discovered in 1977 on the East Pacific Rise by scientists from Scripps Institution of Oceanography. They were observed using a small submersible vehicle called Alvin. Now black smokers are known to exist in the Atlantic and Pacific Oceans, at an average depth of 2100 meters. The most northerly black smokers are a cluster of five named Loki's Castle, [cite web |url=http://www.livescience.com/environment/080724-black-smokers.html |title=Boiling Hot Water Found in Frigid Arctic Sea |accessdate=2008-07-25 |publisher=livescience.com |date=2008-07-24 ] discovered in 2008 by scientists from the University of Bergen at 73 degrees north, on the Mid-Atlantic Ridge between Greenland and Norway. These black smokers are of interest as they are in a more stable area of the earth's crust, where tectonic forces are less and consequently fields of hydrothermal vents are relatively less common. [cite web |url=http://www.sciencedaily.com/releases/2008/07/080724153941.htm |title=Scientists Break Record By Finding Northernmost Hydrothermal Vent Field |accessdate=2008-07-25 |publisher="Science Daily" |date=2008-07-24 ]

The water at a vent can reach C to F|400|wiki=yes, but does not usually boil at the seafloor because the water pressure at that depth exceeds the vapor pressure of the aqueous solution. The water is also extremely acidic, often having a pH value as low as 2.8 — approximately that of vinegar. Each year 1.4 × 10¹⁴ kg (370 trillion gallons) of water is passed through black smokers.

Ecosystems

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 — convert the heat, methane, and sulfur compounds provided by black smokers into energy through a process called chemosynthesis. 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, therefore completing the life cycle.

A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of m to ft|2500. No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organism discovered in nature to use a light other than sunlight for photosynthesis. [Beatty, "et al.", 2005]

New and unusual species are constantly being discovered in the neighborhood of black smokers: for instance, the Pompeii worm in the 1980s, and a scaly-foot gastropod in 2001 during an expedition to Indian Ocean's Kairei hydrothermal vent field. 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 or 246.73 atmosphere) 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 in that community. This snail, which is unique in its kind, has not yet been named.

References

* PMID 11557843
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* PMID 15967984

ee also

*Cold seep
*Hydrothermal vent
*Alvin submersible
*Lost City (hydrothermal field)
*Loki's Castle (hydrothermal field)
*Robert Ballard

External links

* [http://oceanexplorer.noaa.gov Ocean Explorer (www.oceanexplorer.noaa.gov)] - Public outreach site for explorations sponsored by the Office of Ocean Exploration.
* [http://oceanexplorer.noaa.gov/gallery/gallery.html NOAA, Ocean Explorer Gallery] , [http://oceanexplorer.noaa.gov/explorations/06fire/logs/photolog/photolog.html Submarine Ring of Fire 2006 Gallery] , [http://oceanexplorer.noaa.gov/explorations/04fire/logs/photolog/photolog.html Submarine Ring of Fire 2004 Gallery] - A rich collection of images, video, audio and [http://oceanexplorer.noaa.gov/explorations/podcast/oceanexplorer_podcast.xml podcast] .
* [http://www.youtube.com/oceanexplorergov NOAA, Ocean Explorer YouTube Channel]
* [http://oceanexplorer.noaa.gov/explorations/06fire/background/marianaarc/marianaarc.html Submarine Ring of Fire, Mariana Arc] - Explore the volcanoes of the Mariana Arc, Submarine Ring of Fire.
* [http://www.whoi.edu/institutes/doei/viewTopic.do?o=read&id=119 Hydrothermal Vent Systems Information from the Deep Ocean Exploration Institute] , Woods Hole Oceanographic Institution
* [http://www.whoi.edu/oceanus/viewArticle.do?id=2400&archives=true How to Build a Hydrothermal Vent Chimney]
* [http://www.csiro.au/files/mediarelease/mr2000/Smokera.htm Giant black smoker retrieved from abyss] - a vent chimney retrieved by an Australian CSIRO Research Vessel north of Papua New Guinea in April-May 2000.