title: Reduction-oxidation cycles of organic matter increase bacterial activity in the pelagic oxycline.
abstract: Dissolved organic matter (DOM) in aquatic ecosystems contains redox-active moieties, which are prone to oxidation and reduction reactions. Oxidized moieties feature reduction potentials Eh, so that the moieties may be used as terminal electron acceptors (TEAs) in microbial respiration with a thermodynamic energy yield between nitrate and sulfate reduction. Here, we study the response of pelagic freshwater bacteria to exposure to native DOM with varying availabilities of oxidized moieties and hence redox state. Our results show that the prevalence of oxidized DOM favors microbial production and growth in anoxic waters. Reduced DOM in stratified lakes may be oxidized when fluctuations of the oxycline expose DOM in previously anoxic water to epilimnetic oxygen. The resulting oxidized DOM may be rapidly used as TEAs in microbial respiration during subsequent periods of anoxia. We further investigate if the prevalence of these organic electron sinks in anaerobic incubations can induce changes in the microbial community. Our results reveal that DOM traversing transient redox interfaces selects for species that profit from such spatially confined and cyclically restored TEA reservoirs.
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Chemical Analytics and Biogeochemistry, Mueggelseedamm 301, Berlin, Germany.|Universität Greifswald, Institute of Biochemistry, Felix-Hausdorff-Straße 4, 17487, Greifswald, Germany.
authors.forename: Maximilian P
authors.initials: MP
authors.lastname: Lau
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Chemical Analytics and Biogeochemistry, Mueggelseedamm 301, Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hupfer
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Department of Experimental Limnology, Alte Fischerhuette 2, 16775, Stechlin, Berlin, Germany.|University of Potsdam, Institute of Biology and Biochemistry, Karl-Liebknecht-Straße 24-25, 14476, Potsdam, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Grossart
mesh_terms: D000693:Anaerobiosis / Q000502:physiology*; D001419:Bacteria / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology*; D060106:Lakes / Q000032:analysis / Q000382:microbiology; D009566:Nitrates / Q000737:chemistry; D009573:Nitrites / Q000737:chemistry; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry
chemical_list: D009566:Nitrates; D009573:Nitrites; D013431:Sulfates