Black smoker
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.
A black smoker
in the Atlantic Ocean
Black smokers were first discovered in 1977 around the Galápagos
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.
Black smoker ecosystem
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.
Deep sea vent biogeochemical
cycle diagram
A bacterium that uses photosynthesis has been found living near a
black smoker off the coast of Mexico. At a depth of 2,500 m, no
sunlight penetrates the waters. Instead, the bacterium, part of the
Green sulfur bacteria family, use the faint glow from the black
smoker for photosynthesis making it the first organism found in
nature to use a light other than sunlight for the process. (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, 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 2,500 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.
Issue #200
