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Title: Geochemical and Microbial Community Attributes in Relation to Hyporheic Zone Geological Facies

The hyporheic zone (HZ) is the active ecotone between the surface stream and groundwater, where exchanges of water, nutrients, and organic matter occur in response to variations in discharge and riverbed properties. Within this region, a confluence of surface-derived organic carbon and subsurface nitrogen (in the form of nitrate) has been shown to stimulate microbial activity and transformations of carbon and nitrogen species. For example, production of gases such as CO 2, N 2 and N 2O indicate hyporheic zones might have a significant effect on energy and nutrient flows between the atmosphere and the subsurface. Managed and seasonal river stage changes and geomorphology-controlled sediment texture drive water flow within the HZ of the Columbia River. To examine the relationship between sediment texture, biogeochemistry, and biological activity in the HZ, the grain size distributions for sediment samples taken across 320 m of shoreline were characterized to define geological facies, and the relationships among physical properties of the facies, physicochemical attributes of the local environment, and the structure and activity of associated microbial communities were examined. Mud and sand content and the presence of carbon and nitrogen oxidizers were found to explain the variability in many biogeochemical attributes. Microbial community analysismore » revealed a high relative abundance of putative ammonia-oxidizing Thaumarchaeota and nitrite-oxidizing Nitrospirae, together comprising ~20% of the total community across all samples, but scant ammonia-oxidizing Bacteria. Network analysis of operational taxonomic units and the measured geophysical, chemical, and functional parameters showed negative relationships between abundance-based modules of organisms and sand and mud contents, and positive relationships with total organic carbon. The relationships identified in this work indicate grain size distribution is a good predictor of biogeochemical properties, and that subsets of the overall microbial community respond to different sediment texture. Some member populations of these sub-communities appear to respond directly to environmental conditions, while others may be dependent on the function of the first group. For example, nitrification is a strong primary response to the observed conditions, and this activity appears to support a larger heterotrophic community. Relationships between facies and hydrobiogeochemical properties enables facies-based conditional simulation/mapping of these properties to inform multiscale modeling of hyporheic exchange and biogeochemical processes.« less
 [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [2] ;  [5]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy and Environment Directorate
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental and Biological Sciences Directorate
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Graphic Design
  4. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental and Biological Sciences Directorate; Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
  5. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical and Computational Sciences Directorate
Publication Date:
Report Number(s):
Journal ID: ISSN 2045-2322; 48473; KP1702030
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Nature Publishing Group
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; Hyporheic Zone; Biogeochemistry; Facies; Microbial Communities; Environmental Molecular Sciences Laboratory
OSTI Identifier: