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Geophysical Monograph Series



  • Deep-sea ecology—Congresses
  • Mid-ocean ridges—Congresses

Index Terms

  • 8135 Tectonophysics: Hydrothermal systems
  • 3035 Marine Geology and Geophysics: Midocean ridge processes
  • 1050 Geochemistry: Marine geochemistry
  • 4840 Oceanography: Biological and Chemical: Microbiology



Sedimented ridges as a laboratory for exploring the subsurface biosphere

Robert A. Zierenberg

Department of Geology, University of California, Davis, Davis, California

Melanie E. Holland

Department of Geological Sciences, Arizona State University, Tempe, Arizona

Sediment-buried seafloor spreading centers offer one of the best environments for quantifying the extent and composition of the subsurface biosphere, particularly chemosynthetic and thermophilic organisms. Critical parameters that control microbial viability, including temperature, pore fluid composition and fluid advection rates, are routinely measured in sediments, but these same measurements are difficult or impossible to make in normal oceanic crust. Depth zonation of different metabolic pathways for organic carbon diagenesis based on availability of electron acceptors has been extensively investigated in the marine environment and is a fundamental aspect of the subsurface biosphere at sedimented ridges. Additional energy sources for microbial metabolism, including hydrothermal gases and thermogenic hydrocarbons are present at sedimented ridges. Stable isotopes provide a useful tool for distinguishing sources of electron donors and acceptors in this environment, but repeated cycling of compounds across redox boundaries due to burial and diffusion complicates the interpretation of isotope fractionation. Studies of the microbial ecology of sedimented ridges conducted to date demonstrate that interdisciplinary approaches that combine microbiology with geophysical and geochemical characterization of the subsurface environment are critical for understanding the controls on the extent and composition of the subsurface biosphere.

Citation: Zierenberg, R. A., and M. E. Holland (2004), Sedimented ridges as a laboratory for exploring the subsurface biosphere, in The Subseafloor Biosphere at Mid-Ocean Ridges, Geophys. Monogr. Ser., vol. 144, edited by W. S. Wilcock et al., pp. 305–323, AGU, Washington, D. C., doi:10.1029/144GM19.


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