title: Flooding forested groundwater recharge areas modifies microbial communities from top soil to groundwater table.
abstract: Subsurface microorganisms are crucial for contaminant degradation and maintenance of groundwater quality. This study investigates the microbial biomass and community composition [by phospholipid fatty acids (PLFAs)], as well as physical and chemical soil characteristics at woodland flooding sites of an artificial groundwater recharge system used for drinking water production. Vertical soil profiles to c. 4 m at two watered and one nonwatered site were analyzed. The microbial biomass was equal in watered and nonwatered sites, and considerable fractions (25-42%) were located in 40-340 cm depth. The microbial community structure differed significantly between watered and nonwatered sites, predominantly below 100 cm depth. Proportions of the bacterial PLFAs 16:1omega5, 16:1omega7, cy17:0 and 18:1omega9t, and the long-chained PLFAs 22:1omega9 and 24:1omega9 were more prominent at the watered sites, whereas branched, saturated PLFAs (iso/anteiso) dominated at the nonwatered site. PLFA community indices indicated stress response (trans/cis ratio), higher nutrient availability (unsaturation index) and changes in membrane fluidity (iso/anteiso ratio) due to flooding. In conclusion, water recharge processes led to nutrient input and altered environmental conditions, which resulted in a highly active and adapted microbial community residing in the vadose zone that effectively degraded organic compounds.
authors.affiliation: Department of Environmental Sciences, Institute of Biogeography, University of Basel, Basel, Switzerland. kirsten.schuetz@unibas.ch
authors.forename: Kirsten
authors.initials: K
authors.lastname: Schütz
authors.forename: Peter
authors.initials: P
authors.lastname: Nagel
authors.forename: Walter
authors.initials: W
authors.lastname: Vetter
authors.forename: Ellen
authors.initials: E
authors.lastname: Kandeler
authors.forename: Liliane
authors.initials: L
authors.lastname: Ruess
mesh_terms: D001419:Bacteria / Q000737:chemistry / Q000145:classification / Q000254:growth & development / Q000378:metabolism; D018533:Biomass; D017753:Ecosystem; D005227:Fatty Acids / Q000032:analysis; D055868:Floods; D005618:Fresh Water; D009930:Organic Chemicals / Q000378:metabolism; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology; D014197:Trees
chemical_list: D005227:Fatty Acids; D009930:Organic Chemicals; D012987:Soil