Authors: Jennifer L Lowell Nathan Gordon Dale Engstrom Jack A Stanford William E Holben James E Gannon
Publish Date: 2009/05/22
Volume: 58, Issue: 3, Pages: 611-620
Abstract
The Nyack floodplain is located on the Middle Fork of the Flathead River an unregulated pristine fifthorder stream in Montana USA bordering Glacier National Park The hyporheic zone is a nutritionally heterogeneous floodplain component harboring a diverse array of microbial assemblages essential in fluvial biogeochemical cycling riverine ecosystem productivity and trophic interactions Despite these functions microbial community structure in pristine hyporheic systems is not well characterized The current study was designed to assess whether physical habitat heterogeneity within the hyporheic zone of the Nyack floodplain was sufficient to drive bacterial β diversity between three different hyporheic flow path locations Habitat heterogeneity was assessed by measuring soluble reactive phosphorous nitrate dissolved organic carbon dissolved oxygen and soluble total nitrogen levels seasonally at surface water infiltration advection and exfiltration zones Significant spatial differences were detected in dissolved oxygen and nitrate levels and seasonal differences were detected in dissolved oxygen nitrate and dissolved organic carbon levels Denaturing gradient gel electrophoresis DGGE and cell counts indicated that bacterial diversity increased with abundance and DGGE fingerprints covaried with nitrate levels where water infiltrated the hyporheic zone The ribosomal gene phylogeny revealed that hyporheic habitat heterogeneity was sufficient to drive β diversity between bacterial assemblages Phylogenetic P tests detected sequence disparity between the flow path locations Small distinct lineages of Firmicutes Actinomycetes Planctomycetes and Acidobacteria defined the infiltration zone and α and βproteobacterial lineages delineated the exfiltration and advection zone communities These data suggest that spatial habitat heterogeneity drives hyporheic microbial community development and that attempts to understand functional differences between bacteria inhabiting nutritionally heterogeneous hyporheic environments might begin by focusing on the biology of these taxaFunding was provided by the National Science Foundation Microbial Observatory Program grant MCB0348773 We thank Scott Relyea Phil Matson and the laboratory staff from the Flathead Lake Biological Station for technical support Dan Mummey from the University of Montana provided insightful discussion comments and analytical support We also thank the John Dalimata family for access to the study site
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