title: Survey of sediment oxygenation in rhizospheres of the saltmarsh grass - Spartina anglica.
abstract: Although transport of oxygen via the aerenchyma tissue and subsequent oxygen loss across root surfaces is well-documented for salt marsh grasses, only few studies have measured the oxygenation of sediment surrounding roots and rhizomes. In this study, sediment oxygenation was assessed in situ in rhizospheres of the intertidal salt marsh grass, Spartina anglica - an invading species, vigorously spreading in many wetlands around the world. The rhizospheres of two populations of S. anglica with differing plant morphology growing in different sediment types were investigated in situ using a novel multifiber optode system with 100 oxygen probes. No oxygen was detected inside the rhizospheres at any depth in either location, indicating a limited impact of plant-mediated sediment oxygenation on the bulk anoxic sediment. Subsequent planar optode studies imaging the oxygen content around the roots substantiated these findings showing that sediment oxygenation was present in both locations, but it was confined only to the immediate vicinity of the root tips. The size of the oxic zones surrounding the root tips differed between sediment-types: in S. anglica growing in permeable sandy sediment, oxic root zones extended 1.5mm away from the roots surface compared to only 0.4mm in muddy tidal flat deposit, which had a substantially higher oxygen demand. The oxygen concentration inside the oxic root zones remained stable during continuous light and air-exposure of the aboveground biomass. In comparison, sediment oxygenation generated by burrowing infauna (Hediste diversicolor) showed to be markedly more temporally variability, reaching anoxic conditions multiple times during a 5-h period.
authors.affiliation: MARUM - Center for Marine Environmental Sciences, University of Bremen, Leobener Str., D-28359 Bremen, Germany; HGF MPG Joint Research Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany. Electronic address: Kjakobsen@marum.de.
authors.forename: Ketil
authors.initials: K
authors.lastname: Koop-Jakobsen
authors.affiliation: HGF MPG Joint Research Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Fischer
authors.affiliation: HGF MPG Joint Research Group for Deep Sea Ecology and Technology, Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany; HGF MPG Joint Research Group for Deep Sea Ecology and Technology, Alfred-Wegener-Institute Helmholtz Center for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Wenzhöfer
mesh_terms: D000818:Animals; D018533:Biomass; D063366:Estuaries; D019015:Geologic Sediments / Q000737:chemistry*; D010100:Oxygen / Q000032:analysis*; D018517:Plant Roots; D006109:Poaceae; D058441:Rhizosphere; D053833:Wetlands
chemical_list: D010100:Oxygen
keywords: Hediste Diversicolor; Oxic root zones; Oxygen transport; Planar optode; Plant morphology; Wetland plants