If you learned in high school biology class that all life is ultimately dependent on energy from the sun, I’ve got some news for you. Your biology teacher failed to account for the knowledge gained after 1977, when the first hydrothermal vent was discovered at the Galapagos Rift.
Hydrothermal vents are hot springs deep in the ocean (2,000 to 7,700 meters down) that spew fluid and minerals. They are produced by underwater volcanoes or tectonic activity and support suites of organisms that are collectively called hydrothermal vent communities.
Geologists naturally find hydrothermal vents fascinating, but biologists found them paradigm-shifting because their discovery changes the way we understand life on our planet. These vents support many life forms that don’t rely on the sun’s energy as other life on earth does. Rather than using the energy in sunlight to convert carbon dioxide and water into sugars and oxygen the way that plants do via photosynthesis, bacteria and archaea around these vents use chemical energy released from the vents to make food via a process called chemosynthesis. The most common chemical pathway involves using chemical energy to convert oxygen, carbon dioxide and hydrogen sulfide into sugar, sulphur and water.
It was originally thought that organisms at thermal vents depended on “marine snow” for sustenance. Marine snow is a mix of organic debris from dead and decaying organisms that falls deep into the ocean from the upper levels of the sea. It collects into fluffy snowflake-like clumps, and can take weeks to reach the ocean floor. It provides a major food source for many deep-sea animals, but is not the source of nutrition for organisms at hydrothermal vents. We now know that microbes are the primary producers that form the base of the complex food webs that support the abundance of life at hydrothermal vents.
There are many white crabs around vents as well as miniature lobsters. Eyeless shrimp that can sense heat with specialized regions of their head also live there. Dozens of amphipod species flourish around hydrothermal vents, including one common type with a clear body.
A multitude of mollusks live at hydrothermal vents, such as three-foot long white octopuses, barnacles, copepods, mussels, snails and limpets. White or semi-transparent shells are commonplace among vent animals, including in a clam that grows to over a foot. Worms are one of the most abundant types of animals. There are large sessile worms that can grow to five feet long as well as feather duster worms. The Pompeii worm was named after the volcano in recognition of its ability to tolerate temperatures up to 175 degrees Fahrenheit. A fish called an eelpout lives at hydrothermal vents, swimming close to the floor of the ocean eating primarily crustaceans and mollusks. These slow-swimming fish are less than a foot long, white in color and lack scales.
Hydrothermal vents have taught us that sunlight is not necessary for life, a lesson which is not only fascinating, but also has implications for our search for life on other planets.