Hydrothermal vents are holes that form in areas of seamounts and inject heat from mantle wedge. Most of them are located along continental plate boundaries. There is a core in the middle of the earth. At divide into two parts call inner core and outer core. The inner core is made up of iron and nickel. It is about 1,220 km thick and unlikely the outer core; the inner core is mostly solid. The outer core is about 2,400 km thick and made up of iron and nickel. The outer core is lies between the inner core and the mantle of the earth. The mantle is made off of silicate rocks that rich in magnesium and iron. The mantle also divides into 2 layers call mantle and upper mantle. There is a semi-solid, moveable layer call Asthenosphere between the upper mantle and the mantle. Asthenosphere has no strength. The lithosphere is located above the asthenosphere. The lithosphere is made up of the upper mantle and crust. Crush is 0-100 m thick, the stony layer that divided into two different types. They are oceanic lithosphere and continental lithosphere. Those hydrothermal vents are located on the oceanic lithosphere. The internal heat is formed in the core of the earth. Heat is absorbed by silicate rocks and they form into the magmatic fluid. They go upwards through the mantle, asthenosphere, and the upper mantle. The oxygenated, cold sea-water is coming through the fissures that located on the oceanic crust around the hydrothermal vent. This cold water clashes magmatic fluid, absorb heat and release as hot steam through the hydrothermal vents. Those hydrothermal vents are located between tectonic plates that float above the asthenosphere.
In 1977 Richard Von Herzen and Robert Ballard of the Woods Hole Oceanographic Institute has conducted an expedition calls Galapagos Hydrothermal Expedition and they confirmed their existence. But many geologists and marine scientists had been actively searching for hydrothermal vents since the early 1960s. The latest deep-diving technologies, new chemical, biological and mapping sensors improved the searching of hydrothermal vents and allowed scientists greater access to the seafloor. Until today, about 250 of hydrothermal vents have been discovered using robots, human-occupied, remotely-operated, and autonomous vehicles. These discoveries continue until today and the future. There are two types of hydrothermal vents. One of them is releasing black smoke and others are releasing white smoke. Those hydrothermal vents that release black smoke are the hottest of all and it releases mainly sulfides and iron. White smokers are less in heat and the smoke contains barium, calcium, and silicon. Usually, hydrothermal vents are about 1,000 – 2,000 m deep, and the deepest known one was discovered in 2013 in the Caribbean and the depth was 5,000m. hydrothermal vents are divided into two parts call the lower part and upper part. The lower part is located in the mantle and the upper part is located in the lithosphere. The hole that releases smoke is called the chimney. All of the chimneys are located between tectonic plates.
There are two types of primary producers according to their energy source. They are phototrophs and chemotrophs. Phototrophs use solar energy to convert carbon dioxide into carbohydrates. Chemotrophs use energy by the oxidation of inorganic molecules. In hydrothermal vents’ ecosystems, the primary producers are chemosynthetic bacteria. The hydrothermal vent microbial community includes all unicellular organisms that live and reproduce in a chemically distinct area around hydrothermal vents. These include organisms in the microbial mat, free-floating cells, or bacteria in an endosymbiotic relationship with animals. Chemosynthesis bacteria derive nutrients and energy from the geological activity at hydrothermal vents to fix carbon into organic forms. Chemosynthesis is one way in which organisms can produce their own food by converting chemicals into useable nutrients. They use energy from inorganic chemical compounds to make food. This is similar to photosynthesis but not use light. Bacteria that live in the deep ocean, near hydrothermal vents, also produce food through chemosynthesis.
Hydrogen sulfide Chemosynthesis: 12H2S + 6CO2 → C6H12O6 + 6H2O + 12S
Energetically favorable reactions available to chemolithotropic: Methanotrophy: CH4 + 2O2 → CO2 + 2H2O
Methanogenesis: H2 + 1/4CO2 → 1/4CH4 + 1/2H2O
Sulfur reduction: H2 + 1/4SO42- + 1/2H+ → 1/4H2S + H2O
Sulfur oxidation: H2S + 2O2 → SO42- + 2H+
Sulfur oxidation: S + H2O + 31/5O2 + → SO42- + 2H+
Sulfur oxidation: S2O3– + 10OH– + O2 + 4H+ → 2SO42- + 7H2O
Sulfur oxidation: S2O3– + 6OH– + 4/5NO3– + 4/5H+ → 2SO42- + 17/5H2O + 2/5N2
There is a dark environment near the thermal vents. Because light cannot reach that much deep in the ocean. Hence, phototrophs cannot produce food and chemotrophs are the main primary producers of the ecosystem of hydrothermal vents. There are a lot of food webs in the hydrothermal vent ecosystem. These are the major levels of an ecosystem, primary producers, primary consumers, secondary consumers, and tertiary consumers. In a land ecosystem, most of the time the primary producers are photosynthetic plants or algae. But, in hydrothermal ecosystems, chemotroph bacteria are the main primary producers. Because there is no sun-light to occur photosynthesis. Primary consumers are mostly herbivores. They only eat autotrophs such as chemotrophs and phototrophs. In hydrothermal vent ecosystems, the most common primary consumers are The giant tube worm (Riftia pachyptila), The large white clam (Calyptogena magnifica), an undescribed mytilid musel and the Pompeii worm (Alvinella pompejana). Secondary consumers are organisms that gain energy by eating primary consumers. Always secondary consumers are carnivores or omnivores. There are two types of main secondary consumers; fish, and crabs. They are Zoarcid fish(Zoarcidae spp.), Blind crabs(Munidopsis polymorpha), Galatheid crab, Vent ratfish(Hydrolagus colliei), and Vent shrimps (Family Alvinocarididae). Tertiary consumers feed on secondary consumers. Most of the time they are carnivores and sometimes they also be omnivores. They show predatory behaviors. Unlike primary consumers, tertiary consumers gain only a few percentages of energy from food. Vent Ratfish(Hydrolagus colliei), Oysters(Family Ostreidae), Larger crabs, Eels, Moray Eels(Family Muraenidae), Starfish(Family Asteroidea), Vent Octopus(Vulcanoctopus hydrothermalis), and Eelpout fish(Lota lota) are a few examples for tertiary consumers in hydrothermal vent ecosystems.
By learning about hydrothermal vents we can teach about the evolution of life on earth and the possibility of life elsewhere in the solar system and the universe. Some metabolic processes that occur in hydrothermal vents could also have commercial uses one day. And also the compounds found from hydrothermal vents can be valuable in the future. Hydrothermal vents also connected to the beginning of earth and the beginning of life. So, even at present hydrothermal vents provide a lot of pieces of evidence to the scientists to carry their researches on.
