A Return to the Lost City: This Time it’s Microbial

A research group led by Susan Lang and William Brazelton embark on a new expedition to the Lost City hydrothermal field. The researchers will investigate the microbial food chain and the geochemical reactions occurring at this unique seafloor site.

For the first time since 2008 U.S. scientists will thoroughly explore the Lost City hydrothermal field with a dedicated expedition entitled Return to Lost City 2018. 

The field is located on the Atlantis Massif, a dome of peridotite rock from the mantle near the Mid-Atlantic Ridge. On the massif, dozens of chimneys spew alkaline fluids rich in methane and hydrogen, which support a diverse community of microbes, mussels, snails, crustaceans, and worms. These fluids result from serpentinization reactions occurring between peridotite rock and seawater. Scientists aboard the research cruise aim to further investigate microbes living at the site, and how they consume deep carbon seeping from hydrothermal vents along the seafloor.

DCO Deep Life Community members Susan Lang (University of South Carolina, USA) and William Brazelton (University of Utah, USA) lead the expedition, in collaboration with DCO members Gretchen Früh-Green (ETH-Zurich, Switzerland), Marvin Lilley, and Deborah Kelley (both at University of Washington, USA). 

“Lost City is unique because it’s an outstanding example of water reacting with this rock type and the associated serpentinization reactions, whichc are so fascinating,” said Lang. “It’s thought that this rock composition was more prevalent on early Earth, and it’s also potentially driving the fluid chemistry of extraterrestrial bodies, like Saturn’s moon Enceladus.” 

The group departed from Woods Hole, Massachusetts on September 8 aboard the R/V Atlantis and will dock in San Juan, Puerto Rico on October 1. A team from the Woods Hole Oceanographic Institute (WHOI) will be aboard to control Jason, the remotely operated vehicle that will collect large volumes of hydrothermal fluids and rock samples from the field.

Lost City
During their previous expedition, researchers captured fluid and rock samples from the Lost City hydrothermal field. Now, they’re going back for more. Credit: D.S. Kelley, and M. Elend, University of Washington; URI-IOA and ROV Hercules, NOAA Ocean Exploration.

These samples will enable the researchers to test new hypotheses and use the advanced lab techniques they developed since their last trip to the Lost City. DCO helped fund the development of a hydrothermal water sampler that can collect large volumes of fluids, through a grant to Lang. For the first time, these new samplers should provide enough material for analyzing viruses in the ecosystem in collaboration with DCO member Rika Anderson (Carleton College, USA). DCO also funded Früh-Green to collaborate with Lilley to develop large-volume pressurized gas-tight samplers that can collect substantial amounts of dissolved gases, which will allow the measurement of clumped isotopes in dissolved methane to help determine how the methane formed. 

The researchers want to find out which microbes live in different locations throughout the hydrothermal vent field and how they’re making a living. These experiments may also determine which species are at the base of the food web, transforming components of the vent fluids into biomass. “That link from the geochemistry to the biochemistry is probably provided by just one or a very small number of microbial species. If that’s true, then the rest of archaeal, bacterial, and eukaryotic species associated with these systems are dependent on them,” said Brazelton.

Another big question is how the geochemical processes occurring at Lost City transform inorganic carbon into organic compounds independent of microbial life. Such reactions may have been an important step on the path to life’s beginnings on Earth. 

Funding for the expedition comes from the U.S. National Science Foundation, with additional support from the Swiss National Science Foundation, the Center for Dark Energy Biosphere Investigations (C-DEBI), the NASA Astrobiology Institute, and the DCO.

To learn more about this expedition, and to follow along with the team as they explore Lost City, check out the website, or read updates on the blog.

Lost City 1
Credit: D.S. Kelley, University of Washington; URI-IOA and ROV Hercules, Lost City Science Party; NOAA Ocean Exploration.


Main image: At the Lost City hydrothermal field, the manipulator from the ROV Jason reaches out to sample the Beehive chimney. Credit: Image courtesy of Deborah Kelley, University of Washington

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