Chemosynthesis
Chemosynthesis is the process by which organisms use chemical energy, rather than sunlight, to make organic matter from carbon compounds.
What chemosynthesis is
Chemosynthesis is a way of building organic matter using chemical energy. Instead of capturing sunlight like plants and algae do in photosynthesis, chemosynthetic microbes use energy released when inorganic chemicals are oxidized or reduced.
How it differs from photosynthesis
Photosynthesis uses light as its energy source. Chemosynthesis uses chemical reactions involving substances such as hydrogen sulfide, hydrogen, methane, ammonia, or iron compounds. Both processes can fix carbon into molecules that living things can use, but they draw energy from very different places.
Deep-sea vents made it famous
Chemosynthesis became widely known after scientists found rich animal communities around deep-sea hydrothermal vents. Sunlight cannot reach those depths, yet tubeworms, mussels, shrimp, crabs, and microbes thrive there because vent fluids supply chemical energy.
Microbes form the base
At vents and seeps, bacteria and archaea are the primary producers. Some live freely on rocks, in microbial mats, or below the seafloor. Others live as symbionts inside animals, turning chemicals from the environment into food that supports both the microbe and its host.
Not only at vents
Chemosynthetic communities also occur at cold seeps, whale falls, some low-oxygen sediments, caves, and certain hot springs. The setting changes, but the pattern is similar: chemical gradients provide energy for microbes that can support a wider food web.
The chemistry is local
There is no single chemosynthesis recipe. A vent microbe may oxidize hydrogen sulfide, while a seep microbe may use methane. What matters is that the organism can tap a chemical imbalance in its environment and use that energy to fix carbon or grow.
Why animals need partners
Large vent animals do not perform chemosynthesis in the same way microbes do. Many depend on bacteria living in or on their bodies. Giant tubeworms, for example, lack a normal digestive system as adults and rely on internal symbiotic bacteria for nutrition.
Why it matters
Chemosynthesis shows that ecosystems can be powered without sunlight. It reshaped ideas about deep-ocean life, the limits of habitability, early Earth environments, and where life might exist on ocean worlds beyond Earth.