Mysterious life discovered in the smoke of Arctic underwater volcanoes

An unusual new species is found to be thriving off hydrogen more than 2500 below Arctic sea ice.
Sade Agard
Hydrothermal vents at Gakkel Ridge
Hydrothermal vents at Gakkel Ridge

Cruise report 

Inhabiting the freezing, dark, yet explosive environment of underwater volcanoes might seem like a precarious place to make yourself at home. However, according to a study, scientists have identified a strange new species thriving off hydrogen more than 2500 below arctic sea ice.

Survival at deep ocean hydrothermal vents

The underwater volcanoes being referred to are actually known as hydrothermal ventsThese fissures develop deep within the ocean at the boundary of tectonic plates, spewing heated fluids devoid of oxygen and rich in metals like iron, manganese, or copper. Some may also carry hydrogen, methane, and sulfides.

So-called hydrothermal plumes with smoke-like metal sulfide particles form when the hot water combines with the cold, oxygenated ocean around it. These plumes spread thousands of kilometers from their source and soar hundreds of meters above the ocean surface. 

First author Massimiliano Molari from the Max Planck Institute for Marine Microbiology in Bremen, Germany, and colleagues embarked on a challenging sampling trip to hydrothermal plumes in the Central Arctic and South Atlantic Ocean. 

"We sampled plumes in extremely remote areas of ultraslow spreading ridges that were never studied before. Collecting hydrothermal plume samples is very complicated, as they are not easy to locate," explained group leader Antje Boetius in a press release.

He further explained that sampling becomes more complicated when the plume is located at depths more than 2500 meters below Arctic sea ice. Even more tricky is when the plume is in the Southern Ocean's stormy zones.

Onboard the research vessel Polarstern the arctic team gathered samples to examine the makeup and metabolism of bacteria in this water.

Mysterious life discovered in the smoke of Arctic underwater volcanoes
The study was carried out onboard the vessel Polarstern

They discovered that the cold, oxygen-saturated hydrothermal plumes were home to a brand-new Sulfurimonas species known as USulfurimonas pluma (the superscript "U" refers to uncultivated). As the name implies, Sulfurimonas bacteria have only been observed to utilize sulfide as an energy source thus far. 

The new species has a significantly reduced genome

Surprisingly, this new microorganism uses hydrogen from the plume as an energy source. The genome of the bacteria was also examined by the researchers, who discovered that it was significantly reduced, lacking genes typical of their relatives- yet, otherwise well-equipped to support growth in this dynamic environment.

"We think that the hydrothermal plume does not only disperse microorganisms from hydrothermal vents, but it might also ecologically connect the open ocean with seafloor habitats," Molari stated. 

A look at genome data from other plumes revealed that USulfurimonas pluma grows in these environments globally. 

"We have to rethink our ideas on the ecological role of Sulfurimonas in the deep ocean – they might be much more important than we previously thought," Molari concluded.

The study was published today in Nature.

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