Scientists discovered a new class of hydrothermal vents in the Atlantic
as recently as December of 2000. Geologists performing a deep-water
camera survey of the terrain near the under-sea mountain known as
Atlantis Massif serendipitously recorded the Lost City site (Kelly, 2005). The geological
processes that drive venting at Lost City are different from those
at other known sites. Consequently, the physical and chemical characteristics
are also different. Generally, when searching for hydrothermal sites,
scientists concentrate on the margins within 1-5 km of spreading
The Lost City hydrothermal field is located 15 km from the Mid Atlantic Ridge spreading center at the latitude of 30 degrees N. Instead of the black smoker formations built up by the precipitating fluids exposed to basalt, Lost City's formations are composed of large white carbonate chimneys. Here vent fluids are exposed to uplifted peridotites and are serpentinized. The pH is higher-basic rather that acidic-- carbon dioxide levels are extremely low, and the temperature of vent fluids ranges only between 40-90 degrees C rather then in excess of 300 degrees C. Microorganisms acquire their energy from methane and pure hydrogen instead of the oxidation of hydrogen sulfide. Carbon 14 studies indicate that the vent field has been around for approximately 30,000 years. Scientists speculate that these newly discovered vent fields may last for hundreds of thousands of years (Boetius, 2005).
Due to differences in the geology and chemistry of this vent site, the nature
of the community associated with Lost City is substantially different
from black smoker communities. Instead of large clusters of sessile
invertebrates, organisms are smaller and are found in less densely
aggregated groups (Kelly, 2005). Currently,
no evidence suggests the existence of symbiotic relationships between
animals and the chemoautotrophic microorganisms forming the bottom
of the food chain. Instead it appears that the marine invertebrates
gain energy from grazing on vent-associated carbonates and microbial
and amphipods have been found living in channels of actively venting
carbonate sites that range in temperatures between 10-40 degrees
C. Polycheates, nematodes, ostracods, stromatopods and bivalves
inhabit hydrothermally active flanges and spires. Larger, more mobile
animals found at the site include wreckfish, cut-throat eels, and
geryonid crabs (Kelley et al, 2005).
At this point, no one knows how common serpentine hydrothermal vent systems may be. Peridotites can exist in extensive ranges and, with the right geological conditions, it is possible there may be many as yet undiscovered hydrothermal vent systems and communities similar to those found at Lost City.
GO TO Why study hydrothermal vents?
List of Visuals
- Map showing location of Lost City
whyfiles.org (University of Wisconsin, Board of Regents)
- Carbonate chimney from Lost City
Ocean Explorer, National Oceanic and Atmospheric Administration
(14th Street & Constitution Avenue NW, Room 6217, Washington,