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Hydrothermal vents are underwater hot springs, in a sense. They are formed when cold seawater trickles down through fissures in places such as the subduction zone (where tectonic plates converge or diverge), hotspots, or other seismically active areas and meets up with hot magma. There the water is heated and rises back towards the surface, eventually making its way out from openings in the sea floor. The water that shoots out of these vents can reach temperatures of up to 340°C (700°F), but does not turn to steam due to the immense pressure at the ocean floor. In contrast to most other parts of the deep ocean, hydrothermal vents are hosts to an astonishing variety of lifeforms, many of which are unlike any other ever seen before.
Hydrothermal vents and black smokers edit
It isn't only the extremely high temperature of the water pouring forth from these vents that makes them unique. As the water makes its way down through the fissures, minerals such as sulfur, copper, iron, and zinc are transferred from the hot crust into the water. Later, as the superheated water makes its way back up, it carries these minerals with it, which separate as the water rapidly cools. They can accumulate in large quantities, creating some of the richest mineral deposits in the world.
Because the vents are located at such depths, the water pressure pushing down around it is incredible. This pressure is what allows the water to reach temperatures so far above boiling yet still retain its liquid form. This is important to the life that thrives around these vents, as the water can carry dissolved minerals in liquid form that otherwise would not be possible as a steam.
The vents themselves are originally just openings in the ocean floor, and do not possess the chimney shape that is commonly associated with them. Instead, that shape is due to the accumulation of these dissolved minerals. They begin with deposits of anhydrite, which forms the basis. Then the sulfides precipitate through the gaps, closing up larger openings and forming the chimney shape. These vents can grow to rapidly, up to 30 centimeters a day, to enormous sizes. One vent chimney, dubbed "Godzilla", in the Pacific Ocean off the coast of Oregon grew to the size of a fifteen story building before finally toppling, and is rapidly regrowing today.
The water from the vents is also highly acidic, with the pH levels reaching as low as 2.9, around the same acidity as vinegar. This in combination with the sulfides makes the environment highly toxic to almost all known animals that live elsewhere.
Black smokers is the name given to the hottest of these vents, and are named such because the water is colored black due to the high concentration of sulfides in it. They are also amongst the hottest of the vents, with water temperatures averaging around 407°C. Despite the incredible heat and toxic chemicals, it is around these black smokers that a truly amazing amount of biodiversity is found.
A variety of biological life edit
Life has often been thought to have derived its energy from the sun. On land and in the ocean, the source of food for all larger creatures begins with photosynthesizing organisms, such as plants or phytoplankton. However, no light reaches the ocean floor along the abyssal plains, so it was thought for the longest time that very little life could survive, and they would rely on scavenging food that fell from the higher depths.
However, when the first hydrothermal vent was discovered in 1977, scientists discovered with it an environment teeming with life. Bacteria that exist in large numbers within the organisms living near the vents are capable of chemosynthesis. They can use sulfur compounds, which are normally toxic to known organisms, and convert them into energy instead.
Tube worms are particularly important to this ecosystem, as they host the vast majority of he bacteria. They are purely parasitic, having no digestive system of their own, and so absorb nutrient from the bacteria, which live directly in their tissue. These tube worms and bacteria in turn support a wide range of life, including but not limited to amphipods, copepods, and then larger organisms such as snails, shrimp, crabs, fish, and octopuses. Since no sunlight reaches these depths, many of these creatures are blind, some having even lost their eyes completely.
One unique species found nowhere else is the scaly-foot gastropod, a species of snail and the only known organism to reinforce its exoskeleton with metal, namely iron. Or the Pompeii worm, which can live in temperatures of up to 80°C. And while these lifeforms rely on the energy from chemosynthesis, there actually is photosynthesis occurring, even at these depths. A new type of phototrophic bacteria was discovered at a black smoker off the coast of Mexico that used the light coming off of the black smokers for photosynthesis. This is the first known organism that is capable of using a light source other than sunlight for photosynthesis.
The sheer diversity of life is staggering, with over 300 new species having already been discovered at vents. Despite often being separated by hundreds of miles, each vent is host to a large community of life, many often being sister species to those found in other vents. And the lifespan of these vents are not long, averaging out be be only a few decades. After the vent dies, the organisms need to find some way to move to a new feeding ground.
Theories on the origin of life edit
Though the first hydrothermal vent was discovered not much more than thirty years ago, the unique ecosystem that thrives around it found nowhere else has given rise to many new hypothesis concerning the origin of life. Life on earth is carbon based, comprised of amino-acids. The chemicals necessary for their formation, however, weren't naturally available in Earth's primitive atmosphere and ocean. Initially, theories such as lightning setting of a chain of chemical reactions were used to explain how life could come to be in such conditions.
However, there is an excess of methane and ammonia around the hydrothermal vents, which contain the necessary elements for the formation of peptides and protocells, which could then go on to form more complex organisms. While there is no definitive proof, these theories are very possible and, if true, would give scientists new insight on the origin and nature of all living organisms.