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Applied and Environmental Microbiology, February 2009, p. 735-747, Vol. 75, No. 3
0099-2240/09/$08.00+0 doi:10.1128/AEM.01469-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado 80309,1 Conservation International, La Paz, Bolivia,2 Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309,3 Stratus Consulting Inc., Boulder, Colorado 803024
Received 30 June 2008/ Accepted 21 November 2008
Fumarolic activity supports the growth of mat-like photoautotrophic communities near the summit (at 6,051 m) of Socompa Volcano in the arid core of the Andes mountains. These communities are isolated within a barren, high-elevation landscape where sparse vascular plants extend to only 4,600 m. Here, we combine biogeochemical and molecular-phylogenetic approaches to characterize the bacterial and eucaryotic assemblages associated with fumarolic and nonfumarolic grounds on Socompa. Small-subunit rRNA genes were PCR amplified, cloned, and sequenced from two fumarolic soil samples and two reference soil samples, including the volcanic debris that covers most of the mountain. The nonfumarolic, dry, volcanic soil was similar in nutrient status to the most extreme Antarctic Dry Valley or Atacama Desert soils, hosted relatively limited microbial communities dominated by Actinobacteria and Fungi, and contained no photoautotrophs. In contrast, modest fumarolic inputs were associated with elevated soil moisture and nutrient levels, the presence of chlorophyll a, and 13C-rich soil organic carbon. Moreover, this soil hosted diverse photoautotroph-dominated assemblages that contained novel lineages and exhibited structure and composition comparable to those of a wetland near the base of Socompa (3,661-m elevation). Fumarole-associated eucaryotes were particularly diverse, with an abundance of green algal lineages and a novel clade of microarthropods. Our data suggest that volcanic degassing of water and 13C-rich CO2 sustains fumarole-associated primary producers, leading to a complex microbial ecosystem within this otherwise barren landscape. Finally, we found that human activities have likely impacted the fumarolic soils and that fumarole-supported photoautotrophic communities may be exceptionally sensitive to anthropogenic disturbance.
Published ahead of print on 12 December 2008.
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