Tube worms wriggle at the Fava Flow Suburbs, a site in the mid-Pacific Ocean that’s 2,500 meters deep. Experiments testing the theory of species dispersal through cracks in the Earth’s crust were performed in this area. Photo courtesy of ROV SuBastian/Schmidt Ocean Institute

World - Scientists Discover a Labyrinth of Life Hidden in the Deep

A deep-sea expedition in Central America uncovers symbiotic bacteria and tube worm nurseries thriving below the seafloor.

There may be no ecosystem on Earth that seems less hospitable than hydrothermal vents. In the perpetual darkness, cold, and relentless pressures of the deep sea, these volcanic seeps spew piping hot water so loaded with particles and metals that it looks like black smoke billowing from a chimney. But even these hellish habitats are crawling with life, ranging from giant clams and ravenous crabs to spindly octopuses and ghostly eelpout fish.

And those are just the creatures lurking above the vents. Using a deep-sea remotely operated vehicle (ROV), researchers recently flipped over slabs of seafloor to uncover a hidden ecosystem teeming with tiny life beneath the vents themselves. According to Monika Bright, a zoologist at the University of Vienna in Austria who led the expedition, the assortment of worms, snails, and microscopic larvae and bacteria that reside down here adds a new layer of complexity to hydrothermal vent ecosystems, which scientists have studied since 1977.

“We’ve known about the vents above for a long time, but this is basically a completely new ecosystem below,” Bright says. “It’s especially strange that we found it in a place that is very well studied.”

Last month, Bright and an international team of collaborators boarded the nonprofit Schmidt Ocean Institute’s research vessel Falkor (too) in Panama. The scientists plumbed the depths off Central America’s Pacific coast to study species ranging from symbiotic bacteria in deep-sea clams to the temperature limits of tiny copepod crustaceans.

The team focused its ROV dives on an area where diverging tectonic platescreate a string of deep-sea volcanoes known as the East Pacific Rise. As the plates drift apart, magma bubbles up from the rift and cools to create new oceanic floor.

These volatile conditions fuel hydrothermal vents. Frigid water percolates through fissures in the splintering oceanic crust and meets the scalding magma below. When the seawater is heated to temperatures of more than 400 °C, chemical reactions create a supercharged fluid that is rich in chemicals such as sulfur, and it spews out of openings in the ocean floor.

These geyser-like vents are hotspots of deep-sea diversity that can thrive in the dark, thanks to bacteria that convert chemicals into energy-providing sugars. Some of these bacteria reside inside the elongated bodies of giant tube worms (Riftia pachyptila). These worms, whose exposed bright-red, feathery gills make them look like two-meter-long lipstick tubes, grow in dense patches around the vents and provide habitats for other vent dwellers.

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