Sediment oxygen consumption: Role in the global marine carbon cycle

The seabed plays a key role in the marine carbon cycle as a) the terminal location of aerobic oxidation of organic matter, b) the greatest anaerobic bioreactor, and c) the greatest repository for reactive organic carbon on Earth. We compiled data on the oxygen uptake of marine sediments with the objective to understand the constraints on mineralization rates of deposited organic matter and their relation to key environmental parameters. The compiled database includes nearly 4000 O 2 uptake data and is available as supplementary material. It includes also information on bottom water O 2 concentration, O 2 penetration depth, geographic position, water depth, and full information on the data sources. We present the different in situ and ex situ approaches to measure the total oxygen uptake (TOU) and the diffusive oxygen uptake (DOU) of sediments and discuss their robustness towards methodological errors and statistical uncertainty. We discuss O 2 transport through the benthic and diffusive boundary layers, the diffusion- and fauna-mediated O 2 uptake, and the coupling of aerobic respiration to anaerobic processes. Five regional examples are presented to illustrate the diversity of the seabed: Eutrophic seas, oxygen minimum zones, abyssal plains, mid-oceanic gyres, and hadal trenches. A multiple correlation analysis shows that seabed O 2 uptake is primarily controlled by ocean depth and sea surface primary productivity. The O2 penetration depth scales with the DOU according to a power law that breaks down under the abyssal ocean gyres. The developed multiple correlation model was used to draw a global map of seabed O2 uptake rates. Respiratory coefficients, differentiated for depth regions of the ocean, were used to convert the global O 2 uptake to organic carbon oxidation. The resulting global budget shows an oxidation of 212 Tmol C yr − 1 in marine sediments with a 5-95% confidence interval of 175-260 Tmol C yr − 1 . A comparison with the global flux of particulate organic carbon (POC) from photic surface waters to the deep sea, determined from multiple sediment trap studies, suggests a deficit in the sedimentation flux at 2000 m water depth of about 70% relative to the carbon turnover in the underlying seabed. At the ocean margins, the flux of organic carbon from rivers and from vegetated coastal ecosystems contributes greatly to the budget and may even exceed the phytoplankton production on the inner continental shelf

Biogeochemie, Fluide, Gashydrate und Paläoklima des Schwarzen Meers = Biogeochemistry, fluids, gas hydrates and paleo climate of the Black Sea : Istanbul, Trabzon, Istanbul ; Forschungsschiff Meteor, Reise Nr. M72 ; 07.02.2007 – 04.06.2007

Das Schwarze Meer ist das größte anoxische Meeresbecken der Erde. Hohe biologische Produktion in der Deckschicht und ein tiefer anoxischer Wasserkörper unterhalb der Chemokline in 100-150 m Wassertiefe füh-ren zu einzigartigen Bedingungen für mikrobielles Leben, geochemische Kreis-läufe und Sedimentationsprozesse. Gas- und Fluidemissionen aus verschiedenen geolo-gischen Formationen wie z.B. Methanaus-tritt entlang der Schelfkante oder Ausstoß von kohlenwasserstoffhaltigen Fluiden aus Schlammvulkanen in Tiefseeregionen lie-fern ein einzigartiges Umfeld für die Erfor-schung von geologischen Tiefenprozessen, geochemischen Kreisläufen, mikrobiellen Habitaten und den kontrollierenden Bedin-gungen für mikrobielle Schlüsselprozesse der Elementkreisläufe in einer permanent anoxischen Welt. Fahrtabschnitt M72/1 untersucht unter der Leitung von Dr. R. Seifert geochemische Kreisläufe und mikrobielles Leben an akti-ven Gasquellen innerhalb der Statbilitäts-zone von Gashydrat ab ca. 700 m Wasser-tiefe im Paläo-Djnepr-Gebiet. Der anschlie-ßende Fahrtabschnitt M 72/2 findet im Rahmen des EU-Projekts HERMES und des deutschen Geotechnologien-Projekts MUMM II unter der Leitung von Prof. Dr. A. Boetius statt und untersucht die Kontrol-len und Mechanismen der mikrobiellen Transporte und Umsätze chemischer Ele-mente an Methanquellen auf der Schelfkante und an Fluidaustritten von Schlammvulka-nen. Als Aktivität eines weiteren Geotech-nologienprojekts METRO widmet sich Fahrtabschnitt M 72/3 unter der Leitung von Prof. Dr. G. Bohrmann der Erforschung von Herkunft, Verteilung und Dynamik von Methan und Gashydraten in Sedimenten sowie der Untersuchung von Methanflüssen von den Sedimenten in die Wassersäule. Anschließend wird Fahrtabschnitt M 72/4seismische Untersuchungen der Migrationswege von Fluiden in den tiefen Unter-gründen des Djnepr-seep-Systems und der Schlammvulkane im Sorokin Trog unter der Leitung von Dr. J. Bialas vornehmen. Den Abschluss bildet Fahrtabschnitt M 72/5 un-ter der Leitung von Dr. C. Borowski mit Untersuchungen der geochemischen und mikrobiellen Prozesse in der geschichteten Wassersäule und in Sedimenten um die Chemokline wie in den tiefen anoxischen Becken. Die Reise M 72 wird am 07. Februar 2007 in Istanbul (Türkei) beginnen und am 04. Juni 2007 ebenfalls in Istanbul enden.The Black Sea is the largest anoxic basin on earth. High biological productivity in the oxygenated surface waters and a deep anoxic water body below the chemocline at 100–150 m water depth provide unique conditions for anaerobic microbial life, geochemical cycling and sedimentation processes which make the present day Black Sea a modern type locality for TOC-rich sedimentation and element cycling processes in the geological past. Hydrocarbon emissions from various geological settings such as methane gas seepage along large stretches of the shelf break and fluid discharges from mud volcanoes in deep-sea regions provide unique environmental conditions for studying geological subsurface processes, geochemical cycling, microbial habitats and controls on microbial key processes for element cycling in a permanent anoxic world. Geochemical cycling and microbial life at active gas seeps located in the stability zone of gas hydrates below 700 m water depth in the paleo Dnepr area will be investigated by leg M 72/1 with Dr. R. Seifert as a chief scientist. In the frame of the EU project HERMES and the German “Geotechnologies” project MUMM II, leg M 72/2 with Prof. Dr. A. Boetius as a chief scientist will focus on the controls and mechanisms of chemical element transport and breakdown by seep microbiota at shelf break gas seeps and fluid discharges of mudvolcanoes in the Sorokin Trough. As an activity of another “Geotechnologies” project METRO, leg M 72/3 with Prof. Dr. G. Bohrmann as a chief scientist will study in various geological settings, mainly of the eastern Black Sea, the origins, distributions and dynamics of methane and gas hydrates in sediments and also methane fluxes from the sediment to the water column. This will be followed by seismic investigations of fluid migration pathways in the subsurface of Sorokin Trough mud volcanoes and the paleo-Dnepr seepage system during M 72/4 with Dr. J. Bialas as a chief scientist. The final leg M 72/5 with Dr. C. Borowski as a chief scientist will lead to various areas in the western and eastern Black Sea and will focus on geochemical and microbiological processes in the stratified water column and in sediments around the chemocline and in the anoxic basins. Cruise M 72 will start on 07th February in Istanbul (Turkey) and end on 04th June again in Istanbul

Property liability insurance firm performance under regulation in Germany

SIGLEUuStB Koeln(38)-861100089 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman