Think of bacteria eating rock. Now think of bacteria eating rock below the ocean floor. How about experimenting on bacteria in that rock 15,000 feet underwater?
With a $3.9 million grant from the Gordon and Betty Moore
Foundation, University of Southern
California researcher Katrina Edwards will lead a
first-of-its-kind drilling expedition to study subseafloor life. This time next
year, she expects to be aboard the German research vessel for deep-sea coring,
R/V Merian, cruising above the Mid-Atlantic Ridge in the tropical Atlantic
Recently discovered subseafloor microbes, which live on
chemical reactions with rock and water, may affect ocean chemistry, the marine
food web and global climate. That’s because the entire volume of Earth’s oceans
appears to circulate through the seabed every 200,000 years – lightning fast,
by geologic standards.
“The ocean crust is more like fractured hard sponge cake
than what we think of as truly solid,” Edwards explains.
Yet scientists know little about this “deep biosphere,” so
Edwards and more than 30 colleagues have pushed for an observatory and at least
a decade of research, which the grant helps make possible.
“Dr. Edwards is pursuing one of the most fascinating
problems in science,” says David Kingsbury, chief program officer of science at
the Moore Foundation, based in San Francisco.
“With the recognition that the subseafloor ocean may teem
with microbial life comes new, fundamental questions about the evolution and
distribution of life and the operation of the carbon cycle,” he adds.
The grant will fund complex engineering and instrumentation
needed for long-term experiments at and below the seafloor. The drilling will
occur under the auspices of the Integrated Ocean Drilling Program, an
international marine research program funded by the National Science Foundation
and Asian government agencies. Shallow drilling is expected to begin in 2009,
and deeper drilling in 2010.
The deep biosphere is uniquely suited for a geobiological
approach, Edwards says, since a proper understanding requires genomics,
analysis of microbe-rock chemical interactions and a timescale in the millions
Edwards and colleagues will drill at a site near Bermuda
through sediments that have accumulated for more than 7 million years. In
addition, they will drill into the basalt below, and then conduct long-term
experiments in both rock types.
The observatory is expected to uncover new details about the
microbes – details impossible to obtain using only rock samples, lab cultures
and other traditional methods. In addition, the unique site – with its deep bed
of sediments enclosed by basalt – will allow researchers to understand where
the bacteria came from.
“The bacteria could have ‘swum’ up into the sediments from
below or they could have floated down from above,” Edwards explains.
Genetic and metabolic pathway data will help the scientists
understand how bacteria at different depths in the sediment are related to each
other and to other known species.
This, in turn, could offer clues about how the bacteria
evolved, perhaps shedding light on the origin of life.
Still, the scientists are unsure of what they will
ultimately discover. “No one has ever done a project like this before, so we
really don’t know,” Edwards says.