Microbial Ecology

, Volume 52, Issue 3, pp 389–398

Hypolithic Cyanobacteria, Dry Limit of Photosynthesis, and Microbial Ecology in the Hyperarid Atacama Desert

  • Kimberley A. Warren-Rhodes
  • Kevin L. Rhodes
  • Stephen B. Pointing
  • Stephanie A. Ewing
  • Donnabella C. Lacap
  • Benito Gómez-Silva
  • Ronald Amundson
  • E. Imre Friedmann
  • Christopher P. McKay
Article

DOI: 10.1007/s00248-006-9055-7

Cite this article as:
Warren-Rhodes, K.A., Rhodes, K.L., Pointing, S.B. et al. Microb Ecol (2006) 52: 389. doi:10.1007/s00248-006-9055-7

Abstract

The occurrence of hypolithic cyanobacteria colonizing translucent stones was quantified along the aridity gradient in the Atacama Desert in Chile, from less arid areas to the hyperarid core where photosynthetic life and thus primary production reach their limits. As mean rainfall declines from 21 to ≤2 mm year−1, the abundance of hypolithic cyanobacteria drops from 28 to <0.1%, molecular diversity declines threefold, and organic carbon residence times increase by three orders of magnitude. Communities contained a single Chroococcidiopsis morphospecies with heterotrophic associates, yet molecular analysis revealed that each stone supported a number of unique 16S rRNA gene-defined genotypes. A fivefold increase in steady-state residence times for organic carbon within communities in the hyperarid core (3200 years turnover time) indicates a significant decline in biological carbon cycling. Six years of microclimate data suggest that the dry limit corresponds to ≤5 mm year−1 rainfall and/or decadal periods of no rain, with <75 h year−1 of liquid water available to cyanobacteria under light conditions suitable for photosynthesis. In the hyperarid core, hypolithic cyanobacteria are rare and exist in small spatially isolated islands amidst a microbially depauperate bare soil. These findings suggest that photosynthetic life is extremely unlikely on the present-day surface of Mars, but may have existed in the past. If so, such microhabitats would probably be widely dispersed, difficult to detect, and millimeters away from virtually lifeless surroundings.

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Kimberley A. Warren-Rhodes
    • 1
    • 2
  • Kevin L. Rhodes
    • 3
  • Stephen B. Pointing
    • 4
  • Stephanie A. Ewing
    • 2
  • Donnabella C. Lacap
    • 4
  • Benito Gómez-Silva
    • 5
  • Ronald Amundson
    • 2
  • E. Imre Friedmann
    • 1
  • Christopher P. McKay
    • 1
  1. 1.NASA-Ames Research CenterMoffett FieldUSA
  2. 2.Department of Environmental Science, Policy and Management, Ecosystem Sciences DivisionThe University of California at BerkeleyBerkeleyUSA
  3. 3.Department of Agriculture, Forestry and Natural Resource ManagementThe University of Hawaii at HiloHiloUSA
  4. 4.Department of Ecology and BiodiversityThe University of Hong KongHong Kong SARChina
  5. 5.Departmento de Biomédico and Instituto del DesiertoUniversidad de AntofagastaAntofagastaChile

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