title: Hypoxia causes preservation of labile organic matter and changes seafloor microbial community composition (Black Sea).
abstract: Bottom-water oxygen supply is a key factor governing the biogeochemistry and community composition of marine sediments. Whether it also determines carbon burial rates remains controversial. We investigated the effect of varying oxygen concentrations (170 to 0 μM O2) on microbial remineralization of organic matter in seafloor sediments and on community diversity of the northwestern Crimean shelf break. This study shows that 50% more organic matter is preserved in surface sediments exposed to hypoxia compared to oxic bottom waters. Hypoxic conditions inhibit bioturbation and decreased remineralization rates even within short periods of a few days. These conditions led to the accumulation of threefold more phytodetritus pigments within 40 years compared to the oxic zone. Bacterial community structure also differed between oxic, hypoxic, and anoxic zones. Functional groups relevant in the degradation of particulate organic matter, such asFlavobacteriia,Gammaproteobacteria, andDeltaproteobacteria, changed with decreasing oxygenation, and the microbial community of the hypoxic zone took longer to degrade similar amounts of deposited reactive matter. We conclude that hypoxic bottom-water conditions-even on short time scales-substantially increase the preservation potential of organic matter because of the negative effects on benthic fauna and particle mixing and by favoring anaerobic processes, including sulfurization of matter.
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.; HGF MPG Joint Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, Bremerhaven, Germany.
authors.forename: Gerdhard L
authors.identifier: 0000-0002-2602-6052
authors.initials: GL
authors.lastname: Jessen
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.; HGF MPG Joint Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, Bremerhaven, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Lichtschlag
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.; HGF MPG Joint Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, Bremerhaven, Germany.
authors.forename: Alban
authors.identifier: 0000-0002-3437-4639
authors.initials: A
authors.lastname: Ramette
authors.affiliation: Department of Oceanography and COPAS Sur-Austral, University of Concepción, Concepción, Chile.
authors.forename: Silvio
authors.initials: S
authors.lastname: Pantoja
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.; HGF MPG Joint Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, Bremerhaven, Germany.; Research Group for Marine Geochemistry (ICBM-MPI Bridging Group), Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Oldenburg, Germany.
authors.forename: Pamela E
authors.initials: PE
authors.lastname: Rossel
authors.affiliation: Department of Surface Waters-Research and Management, Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland.
authors.forename: Carsten J
authors.initials: CJ
authors.lastname: Schubert
authors.affiliation: Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Struck
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.; HGF MPG Joint Research Group for Deep-Sea Ecology and Technology, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, Bremerhaven, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Boetius
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D059038:Black Sea; D002244:Carbon / Q000378:metabolism; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D017753:Ecosystem; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D059014:High-Throughput Nucleotide Sequencing; D009930:Organic Chemicals / Q000737:chemistry*; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D017422:Sequence Analysis, DNA
chemical_list: D009930:Organic Chemicals; D002734:Chlorophyll; D002244:Carbon; D010100:Oxygen; D000077194:Chlorophyll A
keywords: Benthic microbial communities; Black Sea; dissolved organic matter; hypoxia; organic matter quality; sediments; sulfurization