U.S. researchers say they've discovered what may be the world's largest methane seep on the ocean floor, where life thrives under extreme conditions.

A marine research expedition sponsored by the U.S. Bureau of Ocean Energy Management and the National Oceanic and Atmospheric Administration located the seep deep in the western North Atlantic Ocean, far from the life-sustaining energy of the sun.

Life exists in the seep using a process known as chemosynthesis, which begins with bacteria that use the methane to make energy, researchers said.

That forms the basis for life in the harsh environment and could help scientists better understand how organisms can survive under these types of extreme conditions, they said.

"Studies of this kind and of these communities help scientists understand how life thrives in harsh environments, and perhaps even on other planets," researcher Steve Ross of the University of North Carolina Wilmington said.

The unique ecosystem, almost two-thirds of a mile long and hundreds or yards across, is host to a variety of sea creatures including sea cucumbers, mussels, shrimp and a variety of fish, the researchers said.