Weighing the deep continental biosphere

Sean McMahon*, John Parnell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

146 Citations (Scopus)


There is abundant evidence for widespread microbial activity in deep continental fractures and aquifers, with important implications for biogeochemical cycling on Earth and the habitability of other planetary bodies. Whitman etal. (P Natl Acad Sci USA, 95, 1998, 6578) estimated a continental subsurface biomass on the order of 10(16)-10(17)g C. We reassess this value in the light of more recent data including over 100 microbial population density measurements from groundwater around the world. Making conservative assumptions about cell carbon content and the ratio of attached and free-living microorganisms, we find that the evidence continues to support a deep continental biomass estimate of 10(16)-10(17)g C, or 2-19% of Earth's total biomass.

Original languageEnglish
Pages (from-to)113-120
Number of pages8
JournalFEMS Microbiology Ecology
Issue number1
Early online date19 Sep 2013
Publication statusPublished - Jan 2014


  • subsurface
  • biomass
  • groundwater
  • aquifer
  • subsurface microbial communities
  • introduced organic-compounds
  • bacterial communities
  • granitic groundwater
  • Fennoscandian Shield
  • crystalline bedrock
  • Southeastern Sweden
  • basalt aquifier
  • carbon content
  • South-Africa


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