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How do deep-sea vent ecosystems survive without photosynthesis?

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Diagram illustrating Earth's environmental spheres, with labeled sections showing the geosphere (land and crust), biosphere (living things), atmosphere (air), and hydrosphere (water), each extending vertically from the Earth's surface. — Biosphere Earth's environment includes the atmosphere, the hydrosphere, the lithosphere, and the biosphere.

Deep-sea vent ecosystems survive without photosynthesis by relying on chemosynthesis, a process where organisms derive energy from chemical reactions rather than sunlight.12

At these hydrothermal vents, specialized bacteria oxidize sulfur compounds (sulfides) emerging from the ocean floor to produce organic carbon. This chemical energy serves as the foundation for the entire food web. Many vent animals, such as mussels, clams, and vestimentiferan worms, host these bacteria in symbiotic relationships, allowing them to thrive in the aphotic zone. Additionally, free-living bacteria form mats around the vents, providing a direct food source for various crabs, anemones, and other deep-sea fauna.12

By utilizing the chemical energy released from the Earth's crust, these unique communities maintain primary production entirely independent of the Sun.12