Life at Hydrothermal Vents

Hydrothermal vents have some of the harshest conditions on our planet. The water surrounding them is nearly 400ºC, and there also isn’t sunlight at all. However, there is still plenty of life near these hydrothermal vents, and in fact, scientists believe that life originated near them.

What are hydrothermal vents?

Hydrothermal vents are fissures on the seafloor where heated water with dissolved minerals comes out. They are located near volcanically active places: locations where two tectonic plates touch. Hydrothermal vents are also thought to exist on Jupiter’s moon, Europa, as well as Earth.

Hydrothermal vents form when water under the oceanic crust gets superheated by magma, and then rises out of the crust due to being less dense than its surrounding material. They are like underwater geysers in that way. The water that rises out of the crust is mineral rich, so it deposits minerals onto the bottom of the seafloor that eventually solidify to form a vent shape.

There are two types of hydrothermal vents: black smokers and white smokers. Black smokers are black and chimney-like. They emit a black cloud of material that includes a lot of sulfur. This material is superheated water from Earth’s crust that is also dissolved in crust. White smokers vent lighter colored materials, such as barium, calcium and silicon. They are also less hot than black smokers.

Life around hydrothermal vents

Because vents are located so deep in the ocean, no sunlight can reach the organisms living there. Therefore, the primary producers of the ecosystem, bacteria and archaea, must be able to create energy without sunlight; they do this through a process called chemosynthesis, where energy is obtained through chemicals such as methane and sulfur.

You may be wondering, what are archaea? They are the third domain of life, separate from bacteria and eukarya. They are prokaryotes like bacteria, but have differences in the composition of their cell wall and cell membrane. In addition, they are slightly similar to eukarya because they also replicate their DNA and synthesize proteins using molecular machines. Archaea are able to live in extreme temperatures, such as near hot springs or hydrothermal vents.

Since vents produce many minerals, it is easy for bacteria and archaea to perform chemosynthesis, and they often form a mat on the seafloor. Other animals such as giant tubeworms, yeti crabs, and giant vent mussels are able to populate the area because they have a source of food: the bacteria and archaea. Animals and these microorganisms can also form an endosymbiotic bond, when the microorganism lives inside the animal and it benefits both of the organisms. The bacteria or archaea is able to receive protection, and in return, the animal gets energy and organic molecules produced from chemosynthesis.

One of the animals that is able to form an endosymbiotic bond is the giant tube worm, also the world’s heaviest worm. Because of bacteria living inside it and producing energy for it, the giant worm does not have a gut, and it does not eat, either.

Giant tube worms can grow up to 6 feet long and also have a red gill which they can retract inside themselves if they are threatened. The red gill looks a lot like a feather and is also put in a place with cooler water because there is more oxygen in cooler water.

Above: the giant tube worm

They cannot move, so when a vent stops spewing water, an entire colony of worms can die off. However, their larvae are able to colonize a different hydrothermal vent very quickly.

The origin of life

Scientists believe that life may have originated near hydrothermal vents. Here are some of the reasons why:

  • The bacteria and archaea at hydrothermal vents are very primitive

  • Complex organic molecules are found near vents

  • The deep ocean could protect animals from the harsh radiation and meteorites

  • Tube-like fossils similar to organisms found near hydrothermal vents have been dated to be 3.77 million years old, almost as old as the Earth

  • Life originated 4 billion years ago, when land continents had not formed yet

  • Biologists have found that the most recent common ancestor to all life lived in extremely high temperatures, like the environment surrounding a hydrothermal vent

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