Articles | Volume 13, issue 18
https://doi.org/10.5194/bg-13-5379-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/bg-13-5379-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Research article
| 
27 Sep 2016
Research article |
| 27 Sep 2016
Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean)
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL,
CEA-CNRS-UVSQ-Université Paris Saclay, 91198 Gif-sur-Yvette, France
Bruno Lansard
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL,
CEA-CNRS-UVSQ-Université Paris Saclay, 91198 Gif-sur-Yvette, France
Lara Pozzato
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL,
CEA-CNRS-UVSQ-Université Paris Saclay, 91198 Gif-sur-Yvette, France
Institut Méditerranéen d'Océanologie,
CNRS-IRD-Université de Toulon-Aix Marseille, 13288 Marseille, France
Christophe Rabouille
Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL,
CEA-CNRS-UVSQ-Université Paris Saclay, 91198 Gif-sur-Yvette, France
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It remains challenging to fully understand what controls carbon burial in marine sediments globally. Thus, we use a model–data approach to identify patterns of organic matter reactivity at the seafloor across distinct environmental conditions. Our findings support the notion that organic matter reactivity is a dynamic ecosystem property and strongly influences biogeochemical cycling and exchange. Our results are essential to improve predictions of future changes in carbon cycling and climate.
Jens Rassmann, Eryn M. Eitel, Bruno Lansard, Cécile Cathalot, Christophe Brandily, Martial Taillefert, and Christophe Rabouille
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In this paper, we use a large set of measurements made using in situ and lab techniques to elucidate the cause of dissolved inorganic carbon fluxes in sediments from the Rhône delta and its companion compound alkalinity, which carries the absorption capacity of coastal waters with respect to atmospheric CO2. We show that sediment processes (sulfate reduction, FeS precipitation and accumulation) are crucial in generating the alkalinity fluxes observed in this study by in situ incubation chambers.
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The study provides new insights by examining the short-term impact of winter floods on biogeochemical sediment processes near the Rhône River (NW Mediterranean Sea). This is the first winter monitoring of sediment and porewater in deltaic areas. The coupling of these data with a new model enables us to quantify the evolution of biogeochemical processes. It also provides new perspectives on the benthic carbon cycle in river deltas considering climate change, whereby flooding should intensify.
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V. Sanial, P. van Beek, B. Lansard, M. Souhaut, E. Kestenare, F. d'Ovidio, M. Zhou, and S. Blain
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A glacial–interglacial methane-fuelled redistribution of reactive phosphorus between the oceanic and sedimentary phosphorus reservoirs can occur in the ocean when falling sea level lowers the pressure on the seafloor, destabilizes methane hydrates, and triggers the dissolution of P-bearing iron oxides. The mass of phosphate potentially mobilizable from the sediment is similar to the size of the current oceanic reservoir. Hence, this process may play a major role in the marine phosphorus cycle.
Florian Lauryssen, Philippe Crombé, Tom Maris, Elliot Van Maldegem, Marijn Van de Broek, Stijn Temmerman, and Erik Smolders
Biogeosciences, 19, 763–776, https://doi.org/10.5194/bg-19-763-2022, https://doi.org/10.5194/bg-19-763-2022, 2022
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Surface waters in lowland regions have a poor surface water quality, mainly due to excess nutrients like phosphate. Therefore, we wanted to know the phosphate levels without humans, also called the pre-industrial background. Phosphate binds strongly to sediment particles, suspended in the river water. In this research we used sediments deposited by a river as an archive for surface water phosphate back to 1800 CE. Pre-industrial phosphate levels were estimated at one-third of the modern levels.
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Sebastiaan J. van de Velde, Rebecca K. James, Ine Callebaut, Silvia Hidalgo-Martinez, and Filip J. R. Meysman
Biogeosciences, 18, 1451–1461, https://doi.org/10.5194/bg-18-1451-2021, https://doi.org/10.5194/bg-18-1451-2021, 2021
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Some 540 Myr ago, animal life evolved in the ocean. Previous research suggested that when these early animals started inhabiting the seafloor, they retained phosphorus in the seafloor, thereby limiting photosynthesis in the ocean. We studied salt marsh sediments with and without animals and found that their impact on phosphorus retention is limited, which implies that their impact on the global environment might have been less drastic than previously assumed.
Martijn Hermans, Nils Risgaard-Petersen, Filip J. R. Meysman, and Caroline P. Slomp
Biogeosciences, 17, 5919–5938, https://doi.org/10.5194/bg-17-5919-2020, https://doi.org/10.5194/bg-17-5919-2020, 2020
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This paper demonstrates that the recently discovered cable bacteria are capable of using a mineral, known as siderite, as a source for the formation of iron oxides. This work also demonstrates that the activity of cable bacteria can lead to a distinct subsurface layer in the sediment that can be used as a marker for their activity.
Torben Windirsch, Guido Grosse, Mathias Ulrich, Lutz Schirrmeister, Alexander N. Fedorov, Pavel Y. Konstantinov, Matthias Fuchs, Loeka L. Jongejans, Juliane Wolter, Thomas Opel, and Jens Strauss
Biogeosciences, 17, 3797–3814, https://doi.org/10.5194/bg-17-3797-2020, https://doi.org/10.5194/bg-17-3797-2020, 2020
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To extend the knowledge on circumpolar deep permafrost carbon storage, we examined two deep permafrost deposit types (Yedoma and alas) in central Yakutia. We found little but partially undecomposed organic carbon as a result of largely changing sedimentation processes. The carbon stock of the examined Yedoma deposits is about 50 % lower than the general Yedoma domain mean, implying a very hetererogeneous Yedoma composition, while the alas is approximately 80 % below the thermokarst deposit mean.
Anna Plass, Christian Schlosser, Stefan Sommer, Andrew W. Dale, Eric P. Achterberg, and Florian Scholz
Biogeosciences, 17, 3685–3704, https://doi.org/10.5194/bg-17-3685-2020, https://doi.org/10.5194/bg-17-3685-2020, 2020
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We compare the cycling of Fe and Cd in sulfidic sediments of the Peruvian oxygen minimum zone. Due to the contrasting solubility of their sulfide minerals, the sedimentary Fe release and Cd burial fluxes covary with spatial and temporal distributions of H2S. Depending on the solubility of their sulfide minerals, sedimentary trace metal fluxes will respond differently to ocean deoxygenation/expansion of H2S concentrations, which may change trace metal stoichiometry of upwelling water masses.
Biqing Zhu, Manuel Kübler, Melanie Ridoli, Daniel Breitenstein, and Martin H. Schroth
Biogeosciences, 17, 3613–3630, https://doi.org/10.5194/bg-17-3613-2020, https://doi.org/10.5194/bg-17-3613-2020, 2020
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We provide evidence that the greenhouse gas methane (CH4) is enclosed in calcareous glacier-forefield sediments across Switzerland. Geochemical analyses confirmed that this ancient CH4 has its origin in the calcareous parent bedrock. Our estimate of the total quantity of CH4 enclosed in sediments across Switzerland indicates a large CH4 mass (~105 t CH4). We produced evidence that CH4 is stable in its enclosed state, but additional experiments are needed to elucidate its long-term fate.
Matteo Puglini, Victor Brovkin, Pierre Regnier, and Sandra Arndt
Biogeosciences, 17, 3247–3275, https://doi.org/10.5194/bg-17-3247-2020, https://doi.org/10.5194/bg-17-3247-2020, 2020
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A reaction-transport model to assess the potential non-turbulent methane flux from the East Siberian Arctic sediments to water columns is applied here. We show that anaerobic oxidation of methane (AOM) is an efficient filter except for high values of sedimentation rate and advective flow, which enable considerable non-turbulent steady-state methane fluxes. Significant transient methane fluxes can also occur during the building-up phase of the AOM-performing biomass microbial community.
Kyle Delwiche, Junyao Gu, Harold Hemond, and Sarah P. Preheim
Biogeosciences, 17, 3135–3147, https://doi.org/10.5194/bg-17-3135-2020, https://doi.org/10.5194/bg-17-3135-2020, 2020
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In this study, we investigate whether bubbles transport sediments containing arsenic and cyanobacteria from the bottom to the top of a polluted lake. We measured arsenic and cyanobacteria from bubble traps in the lake and from an experimental bubble column in the laboratory. We found that bubble transport was not an important source of arsenic in the surface waters but that bubbles could transport enough cyanobacteria to the surface to exacerbate harmful algal blooms.
Nathaniel Kemnitz, William M. Berelson, Douglas E. Hammond, Laura Morine, Maria Figueroa, Timothy W. Lyons, Simon Scharf, Nick Rollins, Elizabeth Petsios, Sydnie Lemieux, and Tina Treude
Biogeosciences, 17, 2381–2396, https://doi.org/10.5194/bg-17-2381-2020, https://doi.org/10.5194/bg-17-2381-2020, 2020
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Our paper shows how sedimentation in a very low oxygen setting provides a unique record of environmental change. We look at the past 250 years through the filter of sediment accumulation via radioisotope dating and other physical and chemical analyses of these sediments. We conclude, remarkably, that there has been very little change in net sediment mass accumulation through the past 100–150 years, yet just prior to 1900 CE, sediments were accumulating at 50 %–70 % of today's rate.
Dario Fussmann, Avril Jean Elisabeth von Hoyningen-Huene, Andreas Reimer, Dominik Schneider, Hana Babková, Robert Peticzka, Andreas Maier, Gernot Arp, Rolf Daniel, and Patrick Meister
Biogeosciences, 17, 2085–2106, https://doi.org/10.5194/bg-17-2085-2020, https://doi.org/10.5194/bg-17-2085-2020, 2020
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Dolomite (CaMg(CO3)2) is supersaturated in many aquatic settings (e.g., seawater) on modern Earth but does not precipitate directly from the fluid, a fact known as the dolomite problem. The widely acknowledged concept of dolomite precipitation involves microbial extracellular polymeric substances (EPSs) and anoxic conditions as important drivers. In contrast, results from Lake Neusiedl support an alternative concept of Ca–Mg carbonate precipitation under aerobic and alkaline conditions.
Aurèle Vuillemin, André Friese, Richard Wirth, Jan A. Schuessler, Anja M. Schleicher, Helga Kemnitz, Andreas Lücke, Kohen W. Bauer, Sulung Nomosatryo, Friedhelm von Blanckenburg, Rachel Simister, Luis G. Ordoñez, Daniel Ariztegui, Cynthia Henny, James M. Russell, Satria Bijaksana, Hendrik Vogel, Sean A. Crowe, Jens Kallmeyer, and the Towuti Drilling Project
Science team
Biogeosciences, 17, 1955–1973, https://doi.org/10.5194/bg-17-1955-2020, https://doi.org/10.5194/bg-17-1955-2020, 2020
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Ferruginous lakes experience restricted primary production due to phosphorus trapping by ferric iron oxides under oxic conditions. We report the presence of large crystals of vivianite, a ferrous iron phosphate, in sediments from Lake Towuti, Indonesia. We address processes of P retention linked to diagenesis of iron phases. Vivianite crystals had light Fe2+ isotope signatures and contained mineral inclusions consistent with antecedent processes of microbial sulfate and iron reduction.
Sonja Geilert, Patricia Grasse, Kristin Doering, Klaus Wallmann, Claudia Ehlert, Florian Scholz, Martin Frank, Mark Schmidt, and Christian Hensen
Biogeosciences, 17, 1745–1763, https://doi.org/10.5194/bg-17-1745-2020, https://doi.org/10.5194/bg-17-1745-2020, 2020
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Marine silicate weathering is a key process of the marine silica cycle; however, its controlling processes are not well understood. In the Guaymas Basin, silicate weathering has been studied under markedly differing ambient conditions. Environmental settings like redox conditions or terrigenous input of reactive silicates appear to be major factors controlling marine silicate weathering. These factors need to be taken into account in future oceanic mass balances of Si and in modeling studies.
Jessica B. Volz, Laura Haffert, Matthias Haeckel, Andrea Koschinsky, and Sabine Kasten
Biogeosciences, 17, 1113–1131, https://doi.org/10.5194/bg-17-1113-2020, https://doi.org/10.5194/bg-17-1113-2020, 2020
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Potential future deep-sea mining of polymetallic nodules at the seafloor is expected to severely harm the marine environment. However, the consequences on deep-sea ecosystems are still poorly understood. This study on surface sediments from man-made disturbance tracks in the Pacific Ocean shows that due to the removal of the uppermost sediment layer and thereby the loss of organic matter, the geochemical system in the sediments is disturbed for millennia before reaching a new equilibrium.
Ralf Conrad, Melanie Klose, and Alex Enrich-Prast
Biogeosciences, 17, 1063–1069, https://doi.org/10.5194/bg-17-1063-2020, https://doi.org/10.5194/bg-17-1063-2020, 2020
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Lake sediments release the greenhouse gas CH4. Acetate is an important precursor. Although Amazonian lake sediments all contained acetate-consuming methanogens, measurement of the turnover of labeled acetate showed that some sediments converted acetate not to CH4 plus CO2, as expected, but only to CO2. Our results indicate the operation of acetate-oxidizing microorganisms couples the oxidation process to syntrophic methanogenic partners and/or to the reduction of organic compounds.
Jens Rassmann, Eryn M. Eitel, Bruno Lansard, Cécile Cathalot, Christophe Brandily, Martial Taillefert, and Christophe Rabouille
Biogeosciences, 17, 13–33, https://doi.org/10.5194/bg-17-13-2020, https://doi.org/10.5194/bg-17-13-2020, 2020
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In this paper, we use a large set of measurements made using in situ and lab techniques to elucidate the cause of dissolved inorganic carbon fluxes in sediments from the Rhône delta and its companion compound alkalinity, which carries the absorption capacity of coastal waters with respect to atmospheric CO2. We show that sediment processes (sulfate reduction, FeS precipitation and accumulation) are crucial in generating the alkalinity fluxes observed in this study by in situ incubation chambers.
Sophie A. L. Paul, Matthias Haeckel, Michael Bau, Rajina Bajracharya, and Andrea Koschinsky
Biogeosciences, 16, 4829–4849, https://doi.org/10.5194/bg-16-4829-2019, https://doi.org/10.5194/bg-16-4829-2019, 2019
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We studied the upper 10 m of deep-sea sediments, including pore water, in the Peru Basin to understand small-scale variability of trace metals. Our results show high spatial variability related to topographical variations, which in turn impact organic matter contents, degradation processes, and trace metal cycling. Another interesting finding was the influence of dissolving buried nodules on the surrounding sediment and trace metal cycling.
Sarah Paradis, Antonio Pusceddu, Pere Masqué, Pere Puig, Davide Moccia, Tommaso Russo, and Claudio Lo Iacono
Biogeosciences, 16, 4307–4320, https://doi.org/10.5194/bg-16-4307-2019, https://doi.org/10.5194/bg-16-4307-2019, 2019
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Chronic deep bottom trawling in the Gulf of Castellammare (SW Mediterranean) erodes large volumes of sediment, exposing over-century-old sediment depleted in organic matter. Nevertheless, the arrival of fresh and nutritious sediment recovers superficial organic matter in trawling grounds and leads to high turnover rates, partially and temporarily mitigating the impacts of bottom trawling. However, this deposition is ephemeral and it will be swiftly eroded by the passage of the next trawler.
Zhichao Zhou, Bo Liang, Li-Ying Wang, Jin-Feng Liu, Bo-Zhong Mu, Hojae Shim, and Ji-Dong Gu
Biogeosciences, 16, 4229–4241, https://doi.org/10.5194/bg-16-4229-2019, https://doi.org/10.5194/bg-16-4229-2019, 2019
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This study shows a core bacterial microbiome with a small proportion of shared operational taxonomic units of common sequences among all oil reservoirs. Dominant methanogenesis shifts from the hydrogenotrophic pathway in water phase to the acetoclastic pathway in the oil phase at high temperatures, but the opposite is true at low temperatures. There are also major functional metabolism differences between the two phases for amino acids, hydrocarbons, and carbohydrates.
Annika Fiskal, Longhui Deng, Anja Michel, Philip Eickenbusch, Xingguo Han, Lorenzo Lagostina, Rong Zhu, Michael Sander, Martin H. Schroth, Stefano M. Bernasconi, Nathalie Dubois, and Mark A. Lever
Biogeosciences, 16, 3725–3746, https://doi.org/10.5194/bg-16-3725-2019, https://doi.org/10.5194/bg-16-3725-2019, 2019
Hanni Vigderovich, Lewen Liang, Barak Herut, Fengping Wang, Eyal Wurgaft, Maxim Rubin-Blum, and Orit Sivan
Biogeosciences, 16, 3165–3181, https://doi.org/10.5194/bg-16-3165-2019, https://doi.org/10.5194/bg-16-3165-2019, 2019
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Microbial iron reduction participates in important biogeochemical cycles. In the last decade iron reduction has been observed in many aquatic sediments below its classical zone, in the methane production zone, suggesting a link between the two cycles. Here we present evidence for microbial iron reduction in the methanogenic depth of the oligotrophic SE Mediterranean continental shelf using mainly geochemical and microbial sedimentary profiles and suggest possible mechanisms for this process.
Haoyi Yao, Wei-Li Hong, Giuliana Panieri, Simone Sauer, Marta E. Torres, Moritz F. Lehmann, Friederike Gründger, and Helge Niemann
Biogeosciences, 16, 2221–2232, https://doi.org/10.5194/bg-16-2221-2019, https://doi.org/10.5194/bg-16-2221-2019, 2019
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How methane is transported in the sediment is important for the microbial community living on methane. Here we report an observation of a mini-fracture that facilitates the advective gas transport of methane in the sediment, compared to the diffusive fluid transport without a fracture. We found contrasting bio-geochemical signals in these different transport modes. This finding can help to fill the gap in the fracture network system in modulating methane dynamics in surface sediments.
Laura A. Casella, Sixin He, Erika Griesshaber, Lourdes Fernández-Díaz, Martina Greiner, Elizabeth M. Harper, Daniel J. Jackson, Andreas Ziegler, Vasileios Mavromatis, Martin Dietzel, Anton Eisenhauer, Sabino Veintemillas-Verdaguer, Uwe Brand, and Wolfgang W. Schmahl
Biogeosciences, 15, 7451–7484, https://doi.org/10.5194/bg-15-7451-2018, https://doi.org/10.5194/bg-15-7451-2018, 2018
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Biogenic carbonates record past environmental conditions. Fossil shell chemistry and microstructure change as metastable biogenic carbonates are replaced by inorganic calcite. Simulated diagenetic alteration at 175 °C of different shell microstructures showed that (nacreous) shell aragonite and calcite were partially replaced by coarse inorganic calcite crystals due to dissolution–reprecipitation reactions. EBSD maps allowed for qualitative assessment of the degree of diagenetic overprint.
Wytze K. Lenstra, Matthias Egger, Niels A. G. M. van Helmond, Emma Kritzberg, Daniel J. Conley, and Caroline P. Slomp
Biogeosciences, 15, 6979–6996, https://doi.org/10.5194/bg-15-6979-2018, https://doi.org/10.5194/bg-15-6979-2018, 2018
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We show that burial rates of phosphorus (P) in an estuary in the northern Baltic Sea are very high. We demonstrate that at high sedimentation rates, P retention in the sediment is related to the formation of vivianite. With a reactive transport model, we assess the sensitivity of sedimentary vivianite formation. We suggest that enrichments of iron and P in the sediment are linked to periods of enhanced riverine input of Fe, which subsequently strongly enhances P burial in coastal sediments.
Jiarui Liu, Gareth Izon, Jiasheng Wang, Gilad Antler, Zhou Wang, Jie Zhao, and Matthias Egger
Biogeosciences, 15, 6329–6348, https://doi.org/10.5194/bg-15-6329-2018, https://doi.org/10.5194/bg-15-6329-2018, 2018
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Our work provides new insights into the biogeochemical cycling of iron, methane and phosphorus. We found that vivianite, an iron-phosphate mineral, is pervasive in methane-rich sediments, suggesting that iron reduction at depth is coupled to phosphorus and methane cycling on a much greater spatial scale than previously assumed. Acting as an important burial mechanism for iron and phosphorus, vivianite authigenesis may be an under-considered process in both modern and ancient settings alike.
Marc A. Besseling, Ellen C. Hopmans, R. Christine Boschman, Jaap S. Sinninghe Damsté, and Laura Villanueva
Biogeosciences, 15, 4047–4064, https://doi.org/10.5194/bg-15-4047-2018, https://doi.org/10.5194/bg-15-4047-2018, 2018
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Benthic archaea comprise a significant part of the total prokaryotic biomass in marine sediments. Here, we compared the archaeal diversity and intact polar lipid (IPL) composition in both surface and subsurface sediments with different oxygen regimes in the Arabian Sea oxygen minimum zone. The oxygenated sediments were dominated by Thaumarchaeota and IPL-GDGT-0. The anoxic sediment contained highly diverse archaeal communities and high relative abundances of IPL-GDGT-1 to -4.
Georgina Robinson, Thomas MacTavish, Candida Savage, Gary S. Caldwell, Clifford L. W. Jones, Trevor Probyn, Bradley D. Eyre, and Selina M. Stead
Biogeosciences, 15, 1863–1878, https://doi.org/10.5194/bg-15-1863-2018, https://doi.org/10.5194/bg-15-1863-2018, 2018
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This study examined the effect of adding carbon to a sediment-based effluent treatment system to treat nitrogen-rich aquaculture waste. The research was conducted in incubation chambers to measure the exchange of gases and nutrients across the sediment–water interface and examine changes in the sediment microbial community. Adding carbon increased the amount of nitrogen retained in the treatment system, thereby reducing the levels of nitrogen needing to be discharged to the environment.
Daniele Brigolin, Christophe Rabouille, Bruno Bombled, Silvia Colla, Salvatrice Vizzini, Roberto Pastres, and Fabio Pranovi
Biogeosciences, 15, 1347–1366, https://doi.org/10.5194/bg-15-1347-2018, https://doi.org/10.5194/bg-15-1347-2018, 2018
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We present the result of a study carried out in the north-western Adriatic Sea by combining two different types of models with field sampling. A mussel farm was taken as a local source of perturbation to the natural flux of particulate organic carbon to the sediment. Differences in fluxes were primarily associated with mussel physiological conditions. Although restricted, these changes in particulate organic carbon fluxes induced visible effects on sediment biogeochemistry.
Volker Brüchert, Lisa Bröder, Joanna E. Sawicka, Tommaso Tesi, Samantha P. Joye, Xiaole Sun, Igor P. Semiletov, and Vladimir A. Samarkin
Biogeosciences, 15, 471–490, https://doi.org/10.5194/bg-15-471-2018, https://doi.org/10.5194/bg-15-471-2018, 2018
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We determined the aerobic and anaerobic degradation rates of land- and marine-derived organic material in East Siberian shelf sediment. Marine plankton-derived organic carbon was the main source for the oxic dissolved carbon dioxide production, whereas terrestrial organic material significantly contributed to the production of carbon dioxide under anoxic conditions. Our direct degradation rate measurements provide new constraints for the present-day Arctic marine carbon budget.
Jack J. Middelburg
Biogeosciences, 15, 413–427, https://doi.org/10.5194/bg-15-413-2018, https://doi.org/10.5194/bg-15-413-2018, 2018
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Organic carbon processing at the seafloor is studied by geologists to better understand the sedimentary record, by biogeochemists to quantify burial and respiration, by organic geochemists to elucidate compositional changes, and by ecologists to follow carbon transfers within food webs. These disciplinary approaches have their strengths and weaknesses. This award talk provides a synthesis, highlights the role of animals in sediment carbon processing and presents some new concepts.
Craig Smeaton, William E. N. Austin, Althea L. Davies, Agnes Baltzer, John A. Howe, and John M. Baxter
Biogeosciences, 14, 5663–5674, https://doi.org/10.5194/bg-14-5663-2017, https://doi.org/10.5194/bg-14-5663-2017, 2017
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Fjord sediments are recognised as hotspots for the burial and long-term storage of carbon. In this study, we use the Scottish fjords as a natural laboratory. Using geophysical and geochemical analysis in combination with upscaling techniques, we have generated the first full national sedimentary C inventory for a fjordic system. The results indicate that the Scottish fjords on a like-for-like basis are more effective as C stores than their terrestrial counterparts, including Scottish peatlands.
Perran Louis Miall Cook, Adam John Kessler, and Bradley David Eyre
Biogeosciences, 14, 4061–4069, https://doi.org/10.5194/bg-14-4061-2017, https://doi.org/10.5194/bg-14-4061-2017, 2017
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Nitrogen is the key nutrient that typically limits productivity in coastal waters. One of the key controls on the amount of bioavailable nitrogen is the process of denitrification, which converts nitrate (bioavailable) into nitrogen gas. Previous studies suggest high rates of denitrification may take place within carbonate sediments, and one explanation for this is that this process may take place within the sand grains. Here we show evidence to support this hypothesis.
Chris T. Parsons, Fereidoun Rezanezhad, David W. O'Connell, and Philippe Van Cappellen
Biogeosciences, 14, 3585–3602, https://doi.org/10.5194/bg-14-3585-2017, https://doi.org/10.5194/bg-14-3585-2017, 2017
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Phosphorus (P) has accumulated in sediments due to past human activities. The re-release of this P to water contributes to the growth of harmful algal blooms. Our research improves our mechanistic understanding of how P is partitioned between different chemical forms and between sediment and water under dynamic conditions. We demonstrate that P trapped within iron minerals may be less mobile during anoxic conditions than previously thought due to reversible changes to P forms within sediment.
Clint M. Miller, Gerald R. Dickens, Martin Jakobsson, Carina Johansson, Andrey Koshurnikov, Matt O'Regan, Francesco Muschitiello, Christian Stranne, and Carl-Magnus Mörth
Biogeosciences, 14, 2929–2953, https://doi.org/10.5194/bg-14-2929-2017, https://doi.org/10.5194/bg-14-2929-2017, 2017
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Continental slopes north of the East Siberian Sea are assumed to hold large amounts of methane. We present pore water chemistry from the 2014 SWERUS-C3 expedition. These are among the first results generated from this vast climatically sensitive region, and they imply that abundant methane, including gas hydrates, do not characterize the East Siberian Sea slope or rise. This contradicts previous modeling and discussions, which due to the lack of data are almost entirely based assumption.
Laura A. Casella, Erika Griesshaber, Xiaofei Yin, Andreas Ziegler, Vasileios Mavromatis, Dirk Müller, Ann-Christine Ritter, Dorothee Hippler, Elizabeth M. Harper, Martin Dietzel, Adrian Immenhauser, Bernd R. Schöne, Lucia Angiolini, and Wolfgang W. Schmahl
Biogeosciences, 14, 1461–1492, https://doi.org/10.5194/bg-14-1461-2017, https://doi.org/10.5194/bg-14-1461-2017, 2017
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Mollusc shells record past environments. Fossil shell chemistry and microstructure change as metastable biogenic aragonite transforms to stable geogenic calcite. We simulated this alteration of Arctica islandica shells by hydrothermal treatments. Below 175 °C the shell aragonite survived for weeks. At 175 °C the replacement of the original material starts after 4 days and yields submillimetre-sized calcites preserving the macroscopic morphology as well as the original internal micromorphology.
Jung-Ho Hyun, Sung-Han Kim, Jin-Sook Mok, Hyeyoun Cho, Tongsup Lee, Verona Vandieken, and Bo Thamdrup
Biogeosciences, 14, 941–958, https://doi.org/10.5194/bg-14-941-2017, https://doi.org/10.5194/bg-14-941-2017, 2017
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The surface sediments of the Ulleung Basin (UB) in the East Sea are characterized by high organic carbon contents (> 2.5 %, dry wt.) and very high concentrations of Mn oxides (> 200 μmol cm−3) and Fe oxides (up to 100 μmol cm−3). For the first time in deep offshore sediments on the Asian margin with water depth over 2000 m, we report that Mn reduction and Fe reduction were the dominant organic carbon (Corg) oxidation pathways, comprising 45 % and 20 % of total Corg oxidation, respectively.
Matthias Egger, Peter Kraal, Tom Jilbert, Fatimah Sulu-Gambari, Célia J. Sapart, Thomas Röckmann, and Caroline P. Slomp
Biogeosciences, 13, 5333–5355, https://doi.org/10.5194/bg-13-5333-2016, https://doi.org/10.5194/bg-13-5333-2016, 2016
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By combining detailed geochemical analyses with diagenetic modeling, we provide new insights into how methane dynamics may strongly overprint burial records of iron, sulfur and phosphorus in marine systems subject to changes in organic matter loading or water column salinity. A better understanding of these processes will improve our ability to read ancient sediment records and thus to predict the potential consequences of global warming and human-enhanced inputs of nutrients to the ocean.
Jianlin Zhao, Kristof Van Oost, Longqian Chen, and Gerard Govers
Biogeosciences, 13, 4735–4750, https://doi.org/10.5194/bg-13-4735-2016, https://doi.org/10.5194/bg-13-4735-2016, 2016
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We used a novel approach to reassess erosion rates on the CLP. We found that both current average topsoil erosion rates and the maximum magnitude of the erosion-induced carbon sink are overestimated on the CLP. Although average topsoil losses on the CLP are still high, a major increase in agricultural productivity occurred since 1980. Hence, erosion is currently not a direct threat to agricultural productivity on the CLP but the long-term effects of erosion on soil quality remain important.
Heiko Sahling, Christian Borowski, Elva Escobar-Briones, Adriana Gaytán-Caballero, Chieh-Wei Hsu, Markus Loher, Ian MacDonald, Yann Marcon, Thomas Pape, Miriam Römer, Maxim Rubin-Blum, Florence Schubotz, Daniel Smrzka, Gunter Wegener, and Gerhard Bohrmann
Biogeosciences, 13, 4491–4512, https://doi.org/10.5194/bg-13-4491-2016, https://doi.org/10.5194/bg-13-4491-2016, 2016
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We were excited about nature’s diversity when we discovered spectacular flows of heavy oil at the seafloor with the remotely operated vehicle QUEST 4000 m in Campeche Bay, southern Gulf of Mexico. Vigorous methane gas bubble emissions lead to massive gas hydrate deposits at water depth as deep as 3420 m. The hydrates formed metre-sized mounds at the seafloor that were densely overgrown by vestimentiferan tubeworms and other seep-typical organisms.
Clare Woulds, Steven Bouillon, Gregory L. Cowie, Emily Drake, Jack J. Middelburg, and Ursula Witte
Biogeosciences, 13, 4343–4357, https://doi.org/10.5194/bg-13-4343-2016, https://doi.org/10.5194/bg-13-4343-2016, 2016
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Estuarine sediments are important locations for carbon cycling and burial. We used tracer experiments to investigate how site conditions affect the way in which seafloor biological communities cycle carbon. We showed that while total respiration rates are primarily determined by temperature, total carbon processing by the biological community is strongly related to
its biomass. Further, we saw a distinct pattern of carbon cycling in sandy sediment, in which uptake by bacteria dominates.
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Short summary
In situ O2 and pH measurements as well as determination of porewater concentrations of dissolved inorganic carbon, total alkalinity, sulfate and calcium have been measured in the sediments of the Rhône prodelta. Biogeochemical activity decreased with distance from the river mouth. Oxic processes decreased the carbonate saturation state (Ω) by lowering pH, whereas anaerobic organic matter degradation, dominated by sulfate reduction, was accompanied by increasing Ω and carbonate precipitation.
In situ O2 and pH measurements as well as determination of porewater concentrations of dissolved...
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