title: High spatial resolution analysis of the distribution of sulfate reduction and sulfide oxidation in hypoxic sediment in a eutrophic estuary.
abstract: Bottom hypoxia and consequential hydrogen sulfide (H2S) release from sediment in eutrophic estuaries is a major global environmental issue. We investigated dissolved oxygen, pH and H2S concentration profiles with microsensors and by sectioning sediment cores followed by colorimetric analysis. The results of these analyses were then compared with the physicochemical properties of the bottom water and sediment samples to determine their relationships with H2S production in sediment. High organic matter and fine particle composition of the sediment reduced the oxidation-reduction potential, stimulating H2S production. Use of a microsensor enabled measurement of H2S concentration profiles with submillimetre resolution, whereas the conventional sediment-sectioning method gave H2S measurements with a spatial resolution of 10 mm. Furthermore, microsensor measurements revealed H2S consumption occurring at the sediment surface in both the microbial mat and the sediment anoxic layer, which were not observed with sectioning. This H2S consumption prevented H2S release into the overlying water. However, the microsensor measurements had the potential to underestimate H2S concentrations. We propose that a combination of several techniques to measure microbial activity and determine its relationships with physicochemical properties of the sediment is essential to understanding the sulfur cycle under hypoxic conditions in eutrophic sediments.
authors.affiliation: Department of Civil Engineering, Faculty of Engineering, University of Peradeniya, 20400, Sri Lanka.
authors.forename: Rathnayake M L D
authors.initials: RM
authors.lastname: Rathnayake
authors.affiliation: Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue, Shimane 690-8504, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Sugahara
authors.affiliation: National Institute for Environmental Studies (NIES), 16-2, Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Maki
authors.affiliation: National Institute for Environmental Studies (NIES), 16-2, Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Kanaya
authors.affiliation: Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue, Shimane 690-8504, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Seike
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Sapporo 060-8628, Japan E-mail: qsatoh@eng.hokudai.ac.jp.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Satoh
mesh_terms: D004784:Environmental Monitoring; D063366:Estuaries; D005068:Eutrophication; D019015:Geologic Sediments; D006801:Humans; D006862:Hydrogen Sulfide; D000860:Hypoxia; D010084:Oxidation-Reduction; D013431:Sulfates / Q000032:analysis / Q000737:chemistry*; D013440:Sulfides / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D013431:Sulfates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D006862:Hydrogen Sulfide