de Beer Dirk

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Now showing 1 - 6 of 6
  • Article
    Microbial communities under distinct thermal and geochemical regimes in axial and off-axis sediments of Guaymas Basin
    (Frontiers Media, 2021-02-12) Teske, Andreas P. ; Wegener, Gunter ; Chanton, Jeffrey P. ; White, Dylan ; MacGregor, Barbara J. ; Hoer, Daniel ; de Beer, Dirk ; Zhuang, Guangchao ; Saxton, Matthew A. ; Joye, Samantha B. ; Lizarralde, Daniel ; Soule, S. Adam ; Ruff, S. Emil
    Cold seeps and hydrothermal vents are seafloor habitats fueled by subsurface energy sources. Both habitat types coexist in Guaymas Basin in the Gulf of California, providing an opportunity to compare microbial communities with distinct physiologies adapted to different thermal regimes. Hydrothermally active sites in the southern Guaymas Basin axial valley, and cold seep sites at Octopus Mound, a carbonate mound with abundant methanotrophic cold seep fauna at the Central Seep location on the northern off-axis flanking regions, show consistent geochemical and microbial differences between hot, temperate, cold seep, and background sites. The changing microbial actors include autotrophic and heterotrophic bacterial and archaeal lineages that catalyze sulfur, nitrogen, and methane cycling, organic matter degradation, and hydrocarbon oxidation. Thermal, biogeochemical, and microbiological characteristics of the sampling locations indicate that sediment thermal regime and seep-derived or hydrothermal energy sources structure the microbial communities at the sediment surface.
  • Article
    Thermal stress reduces pocilloporid coral resilience to ocean acidification by impairing control over calcifying fluid chemistry
    (American Association for the Advancement of Science, 2021-01-22) Guillermic, Maxence ; Cameron, Louise P. ; De Corte, Ilian ; Misra, Sambuddha ; Bijma, Jelle ; de Beer, Dirk ; Reymond, Claire E. ; Westphal, Hildegard ; Ries, Justin B. ; Eagle, Robert A.
    The combination of thermal stress and ocean acidification (OA) can more negatively affect coral calcification than an individual stressors, but the mechanism behind this interaction is unknown. We used two independent methods (microelectrode and boron geochemistry) to measure calcifying fluid pH (pHcf) and carbonate chemistry of the corals Pocillopora damicornis and Stylophora pistillata grown under various temperature and pCO2 conditions. Although these approaches demonstrate that they record pHcf over different time scales, they reveal that both species can cope with OA under optimal temperatures (28°C) by elevating pHcf and aragonite saturation state (Ωcf) in support of calcification. At 31°C, neither species elevated these parameters as they did at 28°C and, likewise, could not maintain substantially positive calcification rates under any pH treatment. These results reveal a previously uncharacterized influence of temperature on coral pHcf regulation—the apparent mechanism behind the negative interaction between thermal stress and OA on coral calcification.
  • Article
    Eruption of a deep-sea mud volcano triggers rapid sediment movement
    (Nature Publishing Group, 2014-11-11) Feseker, Tomas ; Boetius, Antje ; Wenzhofer, Frank ; Blandin, Jerome ; Olu, Karine ; Yoerger, Dana R. ; Camilli, Richard ; German, Christopher R. ; de Beer, Dirk
    Submarine mud volcanoes are important sources of methane to the water column. However, the temporal variability of their mud and methane emissions is unknown. Methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we show non-steady-state situations of vigorous mud movement that are revealed through variations in fluid flow, seabed temperature and seafloor bathymetry. Time series data for pressure, temperature, pH and seafloor photography were collected over 431 days using a benthic observatory at the active Håkon Mosby Mud Volcano. We documented 25 pulses of hot subsurface fluids, accompanied by eruptions that changed the landscape of the mud volcano. Four major events triggered rapid sediment uplift of more than a metre in height, substantial lateral flow of muds at average velocities of 0.4 m per day, and significant emissions of methane and CO2 from the seafloor.
  • Article
    The Guaymas Basin hiking guide to hydrothermal mounds, chimneys, and microbial mats : complex seafloor expressions of subsurface hydrothermal circulation
    (Frontiers Media, 2016-02-18) Teske, Andreas ; de Beer, Dirk ; McKay, Luke J. ; Tivey, Margaret K. ; Biddle, Jennifer F. ; Hoer, Daniel ; Lloyd, Karen G. ; Lever, Mark A. ; Røy, Hans ; Albert, Daniel B. ; Mendlovitz, Howard P. ; MacGregor, Barbara J.
    The hydrothermal mats, mounds, and chimneys of the southern Guaymas Basin are the surface expression of complex subsurface hydrothermal circulation patterns. In this overview, we document the most frequently visited features of this hydrothermal area with photographs, temperature measurements, and selected geochemical data; many of these distinct habitats await characterization of their microbial communities and activities. Microprofiler deployments on microbial mats and hydrothermal sediments show their steep geochemical and thermal gradients at millimeter-scale vertical resolution. Mapping these hydrothermal features and sampling locations within the southern Guaymas Basin suggest linkages to underlying shallow sills and heat flow gradients. Recognizing the inherent spatial limitations of much current Guaymas Basin sampling calls for comprehensive surveys of the wider spreading region.
  • Article
    Evidence for fungal and chemodenitrification based N2O flux from nitrogen impacted coastal sediments
    (Nature Publishing Group, 2017-06-05) Wankel, Scott D. ; Ziebis, Wiebke ; Buchwald, Carolyn ; Charoenpong, Chawalit N. ; de Beer, Dirk ; Dentinger, Jane ; Xu, Zhenjiang ; Zengler, Karsten
    Although increasing atmospheric nitrous oxide (N2O) has been linked to nitrogen loading, predicting emissions remains difficult, in part due to challenges in disentangling diverse N2O production pathways. As coastal ecosystems are especially impacted by elevated nitrogen, we investigated controls on N2O production mechanisms in intertidal sediments using novel isotopic approaches and microsensors in flow-through incubations. Here we show that during incubations with elevated nitrate, increased N2O fluxes are not mediated by direct bacterial activity, but instead are largely catalysed by fungal denitrification and/or abiotic reactions (e.g., chemodenitrification). Results of these incubations shed new light on nitrogen cycling complexity and possible factors underlying variability of N2O fluxes, driven in part by fungal respiration and/or iron redox cycling. As both processes exhibit N2O yields typically far greater than direct bacterial production, these results emphasize their possibly substantial, yet widely overlooked, role in N2O fluxes, especially in redox-dynamic sediments of coastal ecosystems.
  • Article
    Reactive oxygen species affect the potential for mineralization processes in permeable intertidal flats
    (Nature Research, 2023-02-20) van Erk, Marit R. ; Bourceau, Olivia M. ; Moncada, Chyrene ; Basu, Subhajit ; Hansel, Colleen M. ; de Beer, Dirk
    Intertidal permeable sediments are crucial sites of organic matter remineralization. These sediments likely have a large capacity to produce reactive oxygen species (ROS) because of shifting oxic-anoxic interfaces and intense iron-sulfur cycling. Here, we show that high concentrations of the ROS hydrogen peroxide are present in intertidal sediments using microsensors, and chemiluminescent analysis on extracted porewater. We furthermore investigate the effect of ROS on potential rates of microbial degradation processes in intertidal surface sediments after transient oxygenation, using slurries that transitioned from oxic to anoxic conditions. Enzymatic removal of ROS strongly increases rates of aerobic respiration, sulfate reduction and hydrogen accumulation. We conclude that ROS are formed in sediments, and subsequently moderate microbial mineralization process rates. Although sulfate reduction is completely inhibited in the oxic period, it resumes immediately upon anoxia. This study demonstrates the strong effects of ROS and transient oxygenation on the biogeochemistry of intertidal sediments.