Environmental Microbiology

Microbial Ecology

, Volume 61, Issue 1, pp 166-181

Molecular Characterization and Geological Microenvironment of a Microbial Community Inhabiting Weathered Receding Shale Cliffs

  • Charles S. CockellAffiliated withGeomicrobiology Research Group, Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), The Open University Email author 
  • , David PybusAffiliated withCleveland Potash Ltd.
  • , Karen Olsson-FrancisAffiliated withGeomicrobiology Research Group, Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), The Open University
  • , Laura KellyAffiliated withGeomicrobiology Research Group, Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), The Open University
  • , David PetleyAffiliated withDepartment of Geography, Durham University
  • , Nick RosserAffiliated withDepartment of Geography, Durham University
  • , Kieren HowardAffiliated withMeteoritics and Cosmic Mineralogy, Department of Mineralogy, Natural History Museum
  • , Fred MosselmansAffiliated withDiamond Light Source, Harwell Science and Innovation Campus

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Abstract

Shales play an important role in many earth system processes including coastal erosion, and they form the foundations of many engineering structures. The geobiology of the interior of pyrite-containing receding shale cliffs on the coast of northeast England was examined. The surface of the weathered shales was characterised by a thin layer of disordered authigenic iron oxyhydroxides and localised acicular, platy and aggregated gypsum, which was characterised by Raman spectroscopy, XAS and SEM. These chemical changes are likely to play an important role in causing rock weakening along fractures at the micron scale, which ultimately lead to coastal retreat at the larger scale. The surface of the shale hosts a novel, low-diversity microbial community. The bacterial community was dominated by Proteobacteria, with phylotypes closely associating with Methylocella and other members of the γ-subdivision. The second largest phylogenetic group corresponded to Nitrospira. The archaeal 16S rRNA phylotypes were dominated by a single group of sequences that matched phylotypes reported from South African gold mines and possessed ammonia monooxygenase (amoA) genes. Both the phylogenetic and the mineral data show that acidic microenvironments play an important role in shale weathering, but the shale has a higher microbial diversity than previously described pyritic acid mine drainage sites. The presence of a potentially biogeochemically active microbial population on the rock surface suggests that microorganisms may contribute to early events of shale degradation and coastal erosion.