Lost City (hydrothermal field)
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Lost City is a field of hydrothermal vents in the mid-Atlantic ocean that differ significantly from the black smoker vents found in the late 1970s. The vents were discovered in December 2000 during a National Science Foundation expedition to the mid-Atlantic. A second expedition mounted in 2003 used the Alvin submersible to explore the vents. The details of the chemistry and biology of the Lost City hydrothermal field were published in March 2005.
The vents are located on the seafloor mountain Atlantis Massif, where reactions between seawater and upper mantle peridotite produce methane- and hydrogen-rich fluids that are highly alkaline (pH 9 to 11) , with temperatures ranging from <40° to 90° celsius. There is a field of about 30 chimneys made of calcium carbonate 30 to 60 meters tall, with a number of smaller chimneys.
Lost City vents release methane and hydrogen into the surrounding water; they do not produce significant amounts of carbon dioxide, hydrogen sulfide or metals, which are the major outputs of volcanic black smoker vents. The temperature and pH of water surrounding the two types of vent is also significantly different. Strontium, carbon, and oxygen isotope data and radiocarbon ages document at least 30,000 years of hydrothermal activity driven by serpentinization reactions at Lost City, making the Lost City older than known black smoker vents by at least two orders of magnitude. Correspondingly Lost City and black smoker vents support vastly different lifeforms.
The Lost City supports a variety of small invertebrates associated with the carbonate structures, including snails, bivalves, polychaetes, amphipods, and ostracods. A variety of microorganisms lives in on and around the vents. Methanosarcina-like archaea live inside the vents and oxidise methane; bacteria related to the Firmicutes also live inside the vents. External to the vents archaea, including the newly described ANME-1 and bacteria including proteobacteria oxidise methane, sulfur and hydrogen as their primary source of energy. The Lost City vents lack the high biomass of chemosynthetic microorganisms that are typical of volcanically driven black smoker vents.
Lost City provides geologists, chemists and biologists, a working ecosystem for the study of life and other processes driven by abiotic methane and hydrogen.
Lost City was featured in the Disney 3D IMAX film Aliens of the Deep, directed by James Cameron and Steven Quale.
[edit] References
- Boetius, A. 2005. Lost City Life. Science, 307(5714): 1420-1422
- EurekAlert! Hydrogen and methane provide raw energy for life at 'Lost City', March 3, 2005
- Früh-Green, G.L. 2003. 30,000 Years of Hydrothermal Activity at the Lost City Vent Field. Science, 301(5632):495-498
- Kelly, S. et al. 2005. A Serpentinite-Hosted Ecosystem: The Lost City Hydrothermal Field. Science, 307(5714):1428-1434
