Zusammenfassung
Leg 201 of the Ocean Drilling Program was the first ocean drilling expedition dedicated to the study of life deep beneath the seafloor, a challenge that has since become an integral part of the Integrated Ocean Drilling Program. Seven sites were drilled in the Peru margin and the eastern equatorial Pacific, ranging in water depth from 150 to 5300 m and in sediment depth from 0 to 420 meters below seafloor (mbsf), corresponding to sediment ages of Holocene to late Eocene. Continuous contamination tests with perfluorocarbon and fluorescent microbead tracers were conducted during drilling, and improved shipboard procedures were developed for anaerobic and aseptic handling of sediment samples. Sufficiently uncontaminated sediment was thus obtained from all sites for detailed microbiological and biogeochemical analyses. Microbial cells were detected and enumerated in cores from the sediment surface down to oceanic basalt; the oldest sediment was ~35 Ma. The prokaryotic population size varies in relation to geochemical zonations and to sediment properties determined by oceanographic conditions at the time of deposition. Cell densities increase from the Pacific openocean sites to the upwelling region of the Peruvian shelf, where densities at a sulfate–methane transition zone reach 1010 cells/mL, the highest yet recorded in subsurface sediments. Molecular screening of the subsurface microbial communities reveals a large diversity of bacterial and archaeal phylogenetic lineages, most with no or very few cultured representatives. Only a few sequences related to classical sulfate-reducing bacteria and methanogenic archaea are represented in the clone libraries, even where sulfate reduction and methanogenesis are the 1Jorgensen, B.B., D’Hondt, S.L., and Miller, D.J., 2006. Leg 201 synthesis: Controls on microbial communities in deeply buried sediments. In Jorgensen, B.B., D’Hondt, S.L., and Miller, D.J. (Eds.), Proc. ODP, Sci. Results, 201, 1–45 [Online]. Available from World Wide Web: . [Cited YYYYMM-DD] 2Department of Biogeochemistry, Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany. bjoergen@mpibremen.de 3Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett RI 028821197, USA. 4Integrated Ocean Drilling Program, Texas A&M University, 1000 Discovery Drive, College Station TX
