August 11, 2011
Deep-sea hydrothermal vents are formed at mid-ocean spreading centers where tectonic plates drift apart and new oceanic crust is created by magma rising from deep within the Earth. When seawater interacts with hot rock and rising magma, it becomes superheated, dissolving minerals out of the Earth’s crust. At hydrothermal vents, this superheated energy-laden seawater gushes back out into the ocean at temperatures of up to 400 degrees Celsius, forming black smoker chimneys where it comes into contact with cold deep-sea water. These hot fluids deliver inorganic compounds such as hydrogen sulfide, ammonium, methane, iron and hydrogen to the oceans. The organisms living at hydrothermal vents oxidize these inorganic compounds to gain the energy needed to create organic matter from carbon dioxide. Unlike on land, where sunlight provides the energy for photosynthesis, in the dark depths of the sea, inorganic chemicals provide energy for life in a process called chemosynthesis.
When hydrothermal vents were first discovered more than 30 years ago, researchers were astounded to find that they were inhabited by lush communities of animals such as worms, mollusks and crustaceans, most of which were completely unknown to science. The first to investigate these animals quickly realized that the key to their survival was their symbiotic association with chemosynthetic microbes, which are the on-board power plants for hydrothermal vent animals. Until now, only two sources of energy were known to power chemosynthesis by symbiotic bacteria at hydrothermal vents: Hydrogen sulfide, used by sulfur-oxidizing symbionts, and methane, used by methane-oxidizing symbionts. “We have now discovered a third energy source” says Nicole Dubilier from the Max Planck Institute of Marine Microbiology in Bremen, who led the team responsible for this discovery.