Drilling into the deep biosphere

Studies of microorganisms and their activity deep down in the seabed require advanced coring technology and rigorous contamination control. Sediment samples must be recovered from tens to hundreds of meters below seafloor without contamination by bacteria from the surface world. This is possible through the International Ocean Discovery Program (IODP) which provides access to such sediments throughout the world oceans.

Scientific drilling is not exactly a sterile operation. Yet, sediment cores with uncontaminated interior can be recovered by advanced piston coring technique in transparent plastic liners and sectioned for microbiological and biogeochemical research.  The consistent enumeration of cells in carefully cored marine sediments is accompanied by rigorous contamination controls, whereby a dissolved perfluorocarbon tracer is introduced into the seawater which is pumped down into the drill hole to flush out suspended sediment. The least contaminated sediment is then used for microbiology research.

Center staff on-board IODP-drilling expeditions

Since its establishment in 2007, the Center for Geomicrobiology has participated on board in five drilling expeditions organized by the IODP:

  • #323 Bering Sea Paleoceanography 2009,
  • #327 Juan de Fuca Hydrogeology in the Northeast Pacific 2010,
  • #329 South Pacific Gyre Subseafloor Life 2010,
  • #336 Mid-Atlantic Ridge Microbiology 2011
  • #337 Deep Coalbed Biosphere off Shimokita 2012.
  • #347 Baltic Sea Paleoenvironment 2013

2012: Pacific Ocean

The expedition #337 to the Northwest Pacific offshore Shimokita Peninsula was the first expedition dedicated to subseafloor microbiology that used riser drilling technology. Scientists on board the Japanese vessel, Chikyu, explored 50 million years old coal layers that are buried two kilometers deep beneath the seafloor. Among the scientific questions was whether, after so many years of burial and degradation, the high concentration of organic matter in the lignite still provides extra food and energy to sustain microbial communities. Due to the geothermal gradient of ca 24°C per km, gradual heating may accelerate the bioavailability of this buried hydrocarbon reservoir. Microbiologists and geochemists among the Science Party studied the diversity of microorganisms and analyze how this unique chemical environment affects their metabolic activity.

2013: Baltic Sea

In September-October 2013 a two-month expedition took place in the Baltic Sea with the head of the Center, Bo Barker Jørgensen, as co-chief together with the Swedish geologist Thomas Andrén. Also Ian Marshall and Andrea Torti from the Center participated. The cruise was organized as the fifth expedition of the European Consortium for Ocean Research Drilling (ECORD), the European branch of the IODP. The drilling vessel, Greatship Manisha, was chartered as a platform for 17 scientists, 14 ECORD Science Operator staff, and about 35 members of the drill team and crew. This was the first time scientific drilling was carried out in the Baltic Sea region and the target was the relatively young seabed deposited during the glacial (Weichselian) and post-glacial (Holocene) periods. During the past tens of thousands of years the Baltic Sea was alternately covered by a kilometer of ice, enclosed as a great lake, and opened to the sea as one of the world’s largest brackish water systems. These dramatic variations in climate are preserved in the sediment archive under the Baltic Sea and witness the large environmental shifts in sedimentation, salinity, temperature, productivity and oxygen. Studies of the microbial communities and of extant and fossil DNA will reveal how subsurface life has adapted to conditions of today and, possibly, how it adapted to conditions of the past (www.eso.ecord.org/expeditions/347/347.php).