HYDROTHERMAL VENTS
A
Prior to the 1970’s, scientists assumed that no life could possibly survive the harsh environment of the ocean floor, the principle reason being the lack of sunlight needed for the photosynthesis of plant life. Scientists envisioned this area as a barren abyss-like wasteland and put little time or effort into exploration. Serious attempts to study the ocean floor began in the late nineteenth century, but researchers were faced with several challenges. The first problem was the vessels they travelled in were not equipped to withstand the extreme pressure of the ocean floor. The second problem was these excursions were very dangerous, as some vessels were unable to return to the ocean surface once submerged. All of this changed in the 1970s, however, with the introduction of submersibles, or vehicles designed to withstand the extreme conditions deep under the ocean. What researchers have discovered with this new technology are vast ecosystems that are made possible by towering formations called hydrothermal vents.
B
Hydrothermal vents exist in all oceans within the boundaries of tectonic plates. Where the tectonic plates spread apart, magma rises and cools to form new crust and volcanic mountain chains. As the oceanic crust stretches, it thins and large cracks appear in these chains. These cracks have created the ideal conditions for ocean water to penetrate into the depths of the earth’s crust. The water then returns to the surface via the chimney-like formations of the hydrothermal vents as a mineral-rich solution of water that feeds the organisms in the surrounding ecosystems.
C
As the mineral-rich water is an integral aspect of the vents, scientists have begun spending more time researching this water cycle to determine how far the water has to enter the earth’s crust in order to acquire minerals. Scientists in Kiel, Germany have recently recreated a model to simulate a 6 kilometre-deep and 16 kilometre-wide section of the ocean floor in the Pacific Ocean. They found that there are actually two different types of water flow paths. In one, the water seeps superficially into the vents but does not travel deep into the earth’s crust. In the second type, water seeps in at greater distances and travels several kilometres under the seafloor before coming out years later. It is this second path that allows the water to enrich itself with minerals in the crust.
D
Once the water travels deep into the crust it comes into contact with magma and reaches extremely high temperatures. As pressure in the crust builds, the seawater warms and then rises to the ocean floor, dissolving minerals in the earth’s crust along the way. Before the water spurts forth from the vents, its temperature can reach as high as 400 degrees Celsius, although it ends up cooling down relatively quickly as it combines with the freezing temperatures of the ocean. As the hot and cold waters meet, minerals suspended in the hot water clump together and drop down right at the vent opening. This causes an accumulation of minerals, creating large formations called chimneys.
E
The presence of minerals around the vents on the ocean floor allows the surrounding areas to sustain ecosystems flourishing with life. Bacteria convert the minerals into energy, thus providing nutrients to the surrounding species. Scientists refer to the process of converting minerals into energy as chemosynthesis. It is of particular interest to them because the energy is made without sunlight. Scientists are also interested in this process because one of the chief minerals converted into energy is hydrogen sulphide, a mineral highly toxic to most plant-based life. Scientists hope to understand how this mineral is processed by the bacteria as it can shed more light on how species survived millions of years ago on earth with little oxygen.
F
In addition to relying on hydrogen sulphide for energy, another distinguishing characteristic of these species that intrigues scientists is gigantism, where species that live in shallow waters take on gigantic proportions when they live in the areas close to the vents. Huge species of crab, tubeworms, shrimp, clams and fish have all been discovered, some measuring several metres in length. Scientists do not fully understand why this phenomenon takes place, but they theorise that as species adapt to freezing temperatures and increased water pressure, their cells end up expanding, leading to an extreme increase in size.