Life persists when undersea vents go cold

Undersea thermal vents that go dormant still support marine life even after their blistering, life-sustaining warmth turns to frigid cold, U.S. researchers say. University of Southern California researchers found the microbes that thrive on the hot fluid methane and sulfur spewed by active hydrothermal vents are replaced by different microbes that can survive in the cold by feeding on the solid iron and sulfur that make up the vents themselves. The phenomenon is known as ecological succession, wherein one form of life takes the place of another as conditions in an environment change, a USC release said Tuesday. Scientists have long known active vents provide heat and nutrients necessary to maintain microbes, but dormant vents were thought to be devoid of life. Hydrothermal vents are formed on the ocean floor when hot magma below the surface creates a fissure that spews geothermally heated water at temperatures of more than 750 degrees Fahrenheit. After a (geologically) brief time of activity, seafloor spreading moves them away from magma hot spots and they grow cold and dormant, researchers said. "Hydrothermal vents are really ephemeral in nature," USC microbiologist Katrina Edwards said. Microbial communities on seafloor vents have been studied since the vents themselves were first discovered in the late 1970s, although little attention had been paid to them once they stopped venting.