Once considered a barren plain with the odd hydrothermal vent, the seafloor appears to be teeming with microbial life, according to a paper being published May 29 in Nature.
A 60,000 kilometer seam of basalt is exposed along the mid-ocean ridge spreading system, representing potentially the largest surface area for microbes to colonize on Earth, said USC geomicrobiologist Katrina Edwards, the studys corresponding author.
While seafloor microbes have been detected before, this is the first time they have been quantified. Using genetic analysis, Edwards and colleagues found thousands of times more bacteria on the seafloor than in the water above.
Surprised by the abundance, the scientists tested another Pacific site and arrived at consistent results. This makes it likely that rich microbial life extends across the ocean floor, Edwards said.
The scientists also found higher microbial diversity on the rocks compared with other vibrant systems, such as those found at hydrothermal vents.
Even compared with the microbial diversity of farm soilviewed by many as the richestdiversity on the basalt is statistically equivalent.
These scientists used modern molecular methods to quantify the diversity of microbes in remote deep-sea environments, said David L. Garrison, director of the National Science Foundations biological oceanography program.
As a result, we now know that there are many more such microbes than anyone had guessed, he added.
These findings raise the question of where these bacteria find their energy.
We scratched our heads about what was supporting this high level of growth when the organic carbon content is pretty darn low, Edwards recalled.
With evidence that the oceanic crust supports more bacteria compared with overlying water, the scientists hypothesized that reactions with the rocks themselves might offer fuel for life.
Back in the lab, they calculat
|Contact: Terah DeJong|
University of Southern California