title: The effects of sediment depth and oxygen concentration on the use of organic matter: An experimental study using an infiltration sediment tank.
abstract: Water flowing through hyporheic river sediments or artificial recharge facilities promotes the development of microbial communities with sediment depth. We performed an 83-day mesocosm infiltration experiment, to study how microbial functions (e.g., extracellular enzyme activities and carbon substrate utilization) are affected by sediment depth (up to 50 cm) and different oxygen concentrations. Results indicated that surface sediment layers were mainly colonized by microorganisms capable of using a wide range of substrates (although they preferred to degrade carbon polymeric compounds, as indicated by the higher β-glucosidase activity). In contrast, at a depth of 50 cm, the microbial community became specialized in using fewer carbon substrates, showing decreased functional richness and diversity. At this depth, microorganisms picked nitrogenous compounds, including amino acids and carboxyl acids. After the 83-day experiment, the sediment at the bottom of the tank became anoxic, inhibiting phosphatase activity. Coexistence of aerobic and anaerobic communities, promoted by greater physicochemical heterogeneity, was also observed in deeper sediments. The presence of specific metabolic fingerprints under oxic and anoxic conditions indicated that the microbial community was adapted to use organic matter under different oxygen conditions. Overall the heterogeneity of oxygen concentrations with depth and in time would influence organic matter metabolism in the sediment tank.
authors.affiliation: Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Girona, Spain. Electronic address: anna.freixa@udg.edu.
authors.forename: A
authors.initials: A
authors.lastname: Freixa
authors.affiliation: Civil Environmental and Mechanical Engineering, University of Trento, Trento, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Rubol
authors.affiliation: Hydrogeology Group, Dept. Geotechnical Engineering and Geosciences, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Carles-Brangarí
authors.affiliation: Hydrogeology Group, Dept. Geotechnical Engineering and Geosciences, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Fernàndez-Garcia
authors.affiliation: Department of Ecology, University of Barcelona, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Butturini
authors.affiliation: Hydrogeology Group, Dept. Geotechnical Engineering and Geosciences, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain.
authors.forename: X
authors.initials: X
authors.lastname: Sanchez-Vila
authors.affiliation: Institute of Aquatic Ecology, Department of Environmental Sciences, University of Girona, Girona, Spain.
authors.forename: A M
authors.initials: AM
authors.lastname: Romaní
mesh_terms: D019015:Geologic Sediments / Q000032:analysis* / Q000382:microbiology; D006812:Humic Substances; D010100:Oxygen / Q000032:analysis*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology
chemical_list: D006812:Humic Substances; D010100:Oxygen
keywords: Anoxia; Bacteria; Carbon substrate use; Extracellular enzyme activities