Biogeochemical probing of microbial communities in a basalt-hosted hot spring at Kverkfjöll volcano, Iceland

Authors Organisations
  • Claire Cousins(Author)
    University of St Andrews
  • Marilyn Fogel(Author)
    University of California, Riverside
  • Roxane Bowden(Author)
    Carnegie Institution of Washington
  • Ian A. Crawford(Author)
    Birkbeck, University of London
  • Adrian Boyce(Author)
    Scottish Universities Environmental Research Centre
  • Charles Cockell(Author)
    University of Edinburgh
  • Matt Gunn(Author)
Type Article
Original languageEnglish
Pages (from-to)507-521
Number of pages15
JournalGeobiology
Volume16
Issue number5
Early online date01 Jun 2018
DOI
Publication statusPublished - 01 Sep 2018
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Abstract

We investigated bacterial and archaeal communities along an ice‐fed surficial hot spring at Kverkfjöll volcano—a partially ice‐covered basaltic volcano at Vatnajökull glacier, Iceland, using biomolecular (16S rRNA, apsA, mcrA, amoA, nifH genes) and stable isotope techniques. The hot spring environment is characterized by high temperatures and low dissolved oxygen concentrations at the source (68°C and <1 mg/L (±0.1%)) changing to lower temperatures and higher dissolved oxygen downstream (34.7°C and 5.9 mg/L), with sulfate the dominant anion (225 mg/L at the source). Sediments are comprised of detrital basalt, low‐temperature alteration phases and pyrite, with <0.4 wt. % total organic carbon (TOC). 16S rRNA gene profiles reveal that organisms affiliated with Hydrogenobaculum (54%–87% bacterial population) and Thermoproteales (35%–63% archaeal population) dominate the micro‐oxic hot spring source, while sulfur‐oxidizing archaea (Sulfolobales, 57%–82%), and putative sulfur‐oxidizing and heterotrophic bacterial groups dominate oxic downstream environments. The δ13Corg (‰ V‐PDB) values for sediment TOC and microbial biomass range from −9.4‰ at the spring's source decreasing to −12.6‰ downstream. A reverse effect isotope fractionation of ~3‰ between sediment sulfide (δ34S ~0‰) and dissolved water sulfate (δ34S +3.2‰), and δ18O values of ~ −5.3‰ suggest pyrite forms abiogenically from volcanic sulfide, followed by abiogenic and microbial oxidation. These environments represent an unexplored surficial geothermal environment analogous to transient volcanogenic habitats during putative “snowball Earth” scenarios and volcano–ice geothermal environments on Mars