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  • Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
  • American Meteorological Society (AMS)
  • International Union of Crystallography (IUCr)
  • Nature Publishing Group
  • Periodicals Archive Online (PAO)
  • 2010-2014  (286)
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  • 1
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    Climate warming during Antarctic ice sheet expansion at the Middle Miocene transition (2014)
    Nature Publishing Group
    In:  EPIC3Nature Geoscience, Nature Publishing Group, 7(5), pp. 376-381, ISSN: 1752-0894
    Details
    Publikationsdatum: 2014-07-14
    Beschreibung: During the Middle Miocene climate transition about 14 million years ago, the Antarctic ice sheet expanded to near-modern volume. Surprisingly, this ice sheet growth was accompanied by a warming in the surface waters of the Southern Ocean, whereas a slight deep-water temperature increase was delayed by more than 200 thousand years. Here we use a coupled atmosphere–ocean model to assess the relative effects of changes in atmospheric CO2 concentration and ice sheet growth on regional and global temperatures. In the simulations, changes in the wind field associated with the growth of the ice sheet induce changes in ocean circulation, deep-water formation and sea-ice cover that result in sea surface warming and deep-water cooling in large swaths of the Atlantic and Indian ocean sectors of the Southern Ocean. We interpret these changes as the dominant ocean surface response to a 100-thousand-year phase of massive ice growth in Antarctica. A rise in global annual mean temperatures is also seen in response to increased Antarctic ice surface elevation. In contrast, the longer-term surface and deep-water temperature trends are dominated by changes in atmospheric CO2 concentration. We therefore conclude that the climatic and oceanographic impacts of the Miocene expansion of the Antarctic ice sheet are governed by a complex interplay between wind field, ocean circulation and the sea-ice system.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 2
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    A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch (2014)
    Nature Publishing Group
    In:  EPIC3Nature, Nature Publishing Group, ISSN: 0028-0836
    Details
    Publikationsdatum: 2014-07-17
    Beschreibung: Thermokarst lakes formed across vast regions of Siberia and Alaska during the last deglaciation and are thought to be a net source of atmospheric methane and carbon dioxide during the Holocene epoch1, 2, 3, 4. However, the same thermokarst lakes can also sequester carbon5, and it remains uncertain whether carbon uptake by thermokarst lakes can offset their greenhouse gas emissions. Here we use field observations of Siberian permafrost exposures, radiocarbon dating and spatial analyses to quantify Holocene carbon stocks and fluxes in lake sediments overlying thawed Pleistocene-aged permafrost. We find that carbon accumulation in deep thermokarst-lake sediments since the last deglaciation is about 1.6 times larger than the mass of Pleistocene-aged permafrost carbon released as greenhouse gases when the lakes first formed. Although methane and carbon dioxide emissions following thaw lead to immediate radiative warming, carbon uptake in peat-rich sediments occurs over millennial timescales. We assess thermokarst-lake carbon feedbacks to climate with an atmospheric perturbation model and find that thermokarst basins switched from a net radiative warming to a net cooling climate effect about 5,000 years ago. High rates of Holocene carbon accumulation in 20 lake sediments (47 ± 10 grams of carbon per square metre per year; mean ± standard error) were driven by thermokarst erosion and deposition of terrestrial organic matter, by nutrient release from thawing permafrost that stimulated lake productivity and by slow decomposition in cold, anoxic lake bottoms. When lakes eventually drained, permafrost formation rapidly sequestered sediment carbon. Our estimate of about 160 petagrams of Holocene organic carbon in deep lake basins of Siberia and Alaska increases the circumpolar peat carbon pool estimate for permafrost regions by over 50 per cent (ref. 6). The carbon in perennially frozen drained lake sediments may become vulnerable to mineralization as permafrost disappears7, 8, 9, potentially negating the climate stabilization provided by thermokarst lakes during the late Holocene.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev , info:eu-repo/semantics/article
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  • 3
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    Abrupt glacial climate shifts controlled by ice sheet changes (2014)
    Nature Publishing Group
    In:  EPIC3Nature, Nature Publishing Group, 512(7514), pp. 290-294, ISSN: 0028-0836
    Details
    Publikationsdatum: 2014-09-04
    Beschreibung: During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard–Oeschger (DO) events1. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (BP) in the ice core record2, and has drawn broad attention within the science and policy-making communities alike3. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Here we show, by using a comprehensive fully coupled model16, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere–ocean system and cause rapid glacial climate shifts closely resembling DO events. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence1, 3, 17. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere–ocean–sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and abrupt climate changes in the coupled atmosphere–ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 4
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    Polarforschung, Issues in low resolution (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, ISSN: 00322490
    Details
    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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  • 5
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    Ups and downs in western Crete (Hellenic subduction zone) (2014)
    Nature Publishing Group
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    Publikationsdatum: 2017-04-04
    Beschreibung: Studies of past sea-level markers are commonly used to unveil the tectonic history and seismic behavior of subduction zones. We present new evidence on vertical motions of the Hellenic subduction zone as resulting from a suite of Late Pleistocene - Holocene shorelines in western Crete (Greece). Shoreline ages obtained by AMS radiocarbon dating of seashells, together with the reappraisal of shoreline ages from previous works, testify a long-term uplift rate of 2.5-2.7 mm/y. This average value, however, includes periods in which the vertical motions vary significantly: 2.6-3.2 mm/y subsidence rate from 42 ka to 23 ka, followed by ~7.7 mm/y sustained uplift rate from 23 ka to present. The last ~5 ky shows a relatively slower uplift rate of 3.0-3.3 mm/y, yet slightly higher than the long-term average. A preliminary tectonic model attempts at explaining these up and down motions by across-strike partitioning of fault activity in the subduction zone.
    Beschreibung: Published
    Beschreibung: 5677
    Beschreibung: 2T. Tettonica attiva
    Beschreibung: JCR Journal
    Beschreibung: restricted
    Schlagwort(e): coastal geomorphology ; tectonic rates ; paleoshorelines ; subduction ; Crete ; 04. Solid Earth::04.04. Geology::04.04.03. Geomorphology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Lava flow hazards at Mount Etna: constraints imposed by eruptive history and numerical simulations (2014)
    Nature Publishing Group
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    Publikationsdatum: 2017-04-04
    Beschreibung: Improving lava flow hazard assessment is one of the most important and challenging fields of volcanology, and has an immediate and practical impact on society. Here, we present a methodology for the quantitative assessment of lava flow hazards based on a combination of field data, numerical simulations and probability analyses. With the extensive data available on historic eruptions of Mt. Etna, going back over 2000 years, it has been possible to construct two hazard maps, one for flank and the other for summit eruptions, allowing a quantitative analysis of the most likely future courses of lava flows. The effective use of hazard maps of Etna may help in minimizing the damage from volcanic eruptions through correct land use in densely urbanized area with a population of almost one million people. Although this study was conducted on Mt. Etna, the approach used is designed to be applicable to other volcanic areas.
    Beschreibung: This work was developed within the framework of TecnoLab, the Laboratory for Technological Advance in Volcano Geophysics organized by INGV-CT, DIEES-UNICT, and DMI-UNICT.
    Beschreibung: Published
    Beschreibung: 3493
    Beschreibung: 1V. Storia e struttura dei sistemi vulcanici
    Beschreibung: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Beschreibung: 3V. Dinamiche e scenari eruttivi
    Beschreibung: 4V. Vulcani e ambiente
    Beschreibung: 6A. Monitoraggio ambientale, sicurezza e territorio
    Beschreibung: 3IT. Calcolo scientifico e sistemi informatici
    Beschreibung: JCR Journal
    Beschreibung: restricted
    Schlagwort(e): Lava flow hazard ; Etna ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous ; 05. General::05.02. Data dissemination::05.02.99. General or miscellaneous ; 05. General::05.08. Risk::05.08.99. General or miscellaneous
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Recent thermochronological research in northern Victoria Land, Antarctica (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 84(1), pp. 59-66, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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  • 8
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    Sedimentological field investigations on Permian deposits (Beacon Supergroup) in northern Victoria Land, Antarctica (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 84(1), pp. 49-58, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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  • 9
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    A high resolution aeromagnetic survey over the Mesa Range, northern Victoria Land, Antarctica (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 84(1), pp. 1-13, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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  • 10
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    Micro-gravity measurements in northern Victoria Land, Antarctica; as contribution to geodynamic investigations – a feasibility study (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 84(1), pp. 15-21, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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  • 11
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    Minimal change in Antarctic Circumpolar Current flow speed between the last glacial and Holocene (2014)
    Nature Publishing Group
    In:  EPIC3Nature Geoscience, Nature Publishing Group, 7(2), pp. 113-116, ISSN: 1752-0894
    Details
    Publikationsdatum: 2018-08-10
    Beschreibung: The Antarctic Circumpolar Current is key to the mixing and ventilation of the world’s oceans1, 2, 3, 4, 5. This current flows from west to east between about 45° and 70° S (refs 1, 2, 3) connecting the Atlantic, Pacific and Indian oceans, and is driven by westerly winds and buoyancy forcing. High levels of productivity in the current regulate atmospheric CO2 concentrations6. Reconstructions of the current during the last glacial period suggest that flow speeds were faster7 or similar8 to present, and it is uncertain whether the strength and position of the westerly winds changed9, 10, 11. Here we reconstruct Antarctic Circumpolar Current bottom speeds through the constricting Drake Passage and Scotia Sea during the Last Glacial Maximum and Holocene based on the mean grain size of sortable silt from a suite of sediment cores. We find essentially no change in bottom flow speeds through the region, and, given that the momentum imparted by winds, and modulated by sea-ice cover, is balanced by the interaction of these flows with the seabed, this argues against substantial changes in wind stress. However, glacial flow speeds in the sea-ice zone12 south of 56° S were significantly slower than present, whereas flow in the north was faster, but not significantly so. We suggest that slower flow over the rough topography south of 56° S may have reduced diapycnal mixing in this region during the last glacial period, possibly reducing the diapycnal contribution to the Southern Ocean overturning circulation.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 12
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    Networks from Flows - From Dynamics to Topology (2014)
    Nature Publishing Group
    In:  EPIC3Scientific Reports, Nature Publishing Group, 4(4119), ISSN: 2045-2322
    Details
    Publikationsdatum: 2019-07-17
    Beschreibung: Complex network approaches have recently been applied to continuous spatial dynamical systems, like climate, successfully uncovering the system's interaction structure. However the relationship between the underlying atmospheric or oceanic flow's dynamics and the estimated network measures have remained largely unclear. We bridge this crucial gap in a bottom-up approach and define a continuous analytical analogue of Pearson correlation networks for advection-diffusion dynamics on a background flow. Analysing complex networks of prototypical flows and from time series data of the equatorial Pacific, we find that our analytical model reproduces the most salient features of these networks and thus provides a general foundation of climate networks. The relationships we obtain between velocity field and network measures show that line-like structures of high betweenness mark transition zones in the flow rather than, as previously thought, the propagation of dynamical information.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 13
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    Identification of photosynthetic plankton communities using sedimentary ancient DNA and their response to late-Holocene climate change on the Tibetan Plateau (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-25
    Beschreibung: © The Author(s), 2014]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 4 (2014): 6648, doi:10.1038/srep06648.
    Beschreibung: Sediments from Tibetan lakes in NW China are potentially sensitive recorders of climate change and its impact on ecosystem function. However, the important plankton members in many Tibetan Lakes do not make and leave microscopically diagnostic features in the sedimentary record. Here we established a taxon-specific molecular approach to specifically identify and quantify sedimentary ancient DNA (sedaDNA) of non-fossilized planktonic organisms preserved in a 5-m sediment core from Kusai Lake spanning the last 3100 years. The reliability of the approach was validated with multiple independent genetic markers. Parallel analyses of the geochemistry of the core and paleo-climate proxies revealed that Monsoon strength-driven changes in nutrient availability, temperature, and salinity as well as orbitally-driven changes in light intensity were all responsible for the observed temporal changes in the abundance of two dominant phytoplankton groups in the lake, Synechococcus (cyanobacteria) and Isochrysis (haptophyte algae). Collectively our data show that global and regional climatic events exhibited a strong influence on the paleoecology of phototrophic plankton in Kusai Lake.
    Beschreibung: This research was supported by grants from the National Natural Science Foundation of China (Grant Nos. 41030211 and 41302022), the National Basic Research Program of China (Grant No. 2011CB808800), and State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Nos GBL11410 and GBL11201).
    Repository-Name: Woods Hole Open Access Server
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  • 14
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    Permafrost thawing as a possible source of abrupt carbon release at the onset of the Bølling/Allerød (2014)
    Nature Publishing Group
    In:  EPIC3Nature Communications, Nature Publishing Group, 5, pp. 5520, ISSN: 2041-1723
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    Publikationsdatum: 2016-06-13
    Beschreibung: One of the most abrupt and yet unexplained past rises in atmospheric CO2 (〉10 p.p.m.v. in two centuries) occurred in quasi-synchrony with abrupt northern hemispheric warming into the Bølling/Allerød, ~14,600 years ago. Here we use a U/Th-dated record of atmospheric Δ14C from Tahiti corals to provide an independent and precise age control for this CO2 rise. We also use model simulations to show that the release of old (nearly 14C-free) carbon can explain these changes in CO2 and Δ14C. The Δ14C record provides an independent constraint on the amount of carbon released (~125 Pg C). We suggest, in line with observations of atmospheric CH4 and terrigenous biomarkers, that thawing permafrost in high northern latitudes could have been the source of carbon, possibly with contribution from flooding of the Siberian continental shelf during meltwater pulse 1A. Our findings highlight the potential of the permafrost carbon reservoir to modulate abrupt climate changes via greenhouse-gas feedbacks.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 15
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    Antarctic-wide array of high-resolution ice core records reveals pervasive lead pollution began in 1889 and persists today (2014)
    Nature Publishing Group
    In:  EPIC3Scientific Reports, Nature Publishing Group, 4, pp. 5848, ISSN: 2045-2322
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    Publikationsdatum: 2014-12-17
    Beschreibung: Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead pollution at South Pole and throughout Antarctica by 1889 – beating polar explorers by more than 22 years. Unlike the Arctic where lead pollution peaked in the 1970s, lead pollution in Antarctica was as high in the early 20th century as at any time since industrialization. The similar timing and magnitude of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19th century and remains a significant source today. An estimated 660 t of industrial lead have been deposited over Antarctica during the past 130 years as a result of mid-latitude industrial emissions, with regional-to-global scale circulation likely modulating aerosol concentrations. Despite abatement efforts, significant lead pollution in Antarctica persists into the 21st century.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 16
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    Geology of the Millen Thrust System, northern Victoria Land, Antarctica (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 84(1), pp. 39-47, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
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    Materialart: "Polarforschung" , peerRev
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  • 17
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    The Ross-orogenic Tiger Gabbro (northern Victoria Land, Antarctica): Insights into the lower crust of a Cambrian island arc? (2014)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 84(1), pp. 23-38, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
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    Materialart: "Polarforschung" , peerRev
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  • 18
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    Virtual finger boosts three-dimensional imaging and microsurgery as well as terabyte volume image visualization and analysis (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 5 (2014): 4342, doi:10.1038/ncomms5342.
    Beschreibung: Three-dimensional (3D) bioimaging, visualization and data analysis are in strong need of powerful 3D exploration techniques. We develop virtual finger (VF) to generate 3D curves, points and regions-of-interest in the 3D space of a volumetric image with a single finger operation, such as a computer mouse stroke, or click or zoom from the 2D-projection plane of an image as visualized with a computer. VF provides efficient methods for acquisition, visualization and analysis of 3D images for roundworm, fruitfly, dragonfly, mouse, rat and human. Specifically, VF enables instant 3D optical zoom-in imaging, 3D free-form optical microsurgery, and 3D visualization and annotation of terabytes of whole-brain image volumes. VF also leads to orders of magnitude better efficiency of automated 3D reconstruction of neurons and similar biostructures over our previous systems. We use VF to generate from images of 1,107 Drosophila GAL4 lines a projectome of a Drosophila brain.
    Beschreibung: This work was mainly supported by Howard Hughes Medical Institute. H.P. is currently supported by the Allen Institute for Brain Science. R.W.T. and A.M. were supported by a grant MH071739 (MERIT).
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  • 19
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    Eruption of a deep-sea mud volcano triggers rapid sediment movement (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 5 (2014): 5385, doi:10.1038/ncomms6385.
    Beschreibung: 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.
    Beschreibung: Participation of the Sentry AUV and TETHYS team from WHOI was funded by the Arctic Research Initiative of WHOI’s Ocean and Climate Change Institute and the NASA ASTEP grant NNX09AB76G. Additional funds were made available by the AWI, the Max Planck Society and the DFG METEOR/MERIAN programme, as well as the Leibniz programme to A.B.
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  • 20
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    Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 5 (2014): 4102, doi:10.1038/ncomms5102.
    Beschreibung: Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and δ18O for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1–2 °C larger temperature decrease between 17° and 20°S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought.
    Beschreibung: Funding was provided by Deutsche Forschungsgemeinschaft (FE 615/4-1), Australian Research Council (Discovery grant DP1094001), Australia and New Zealand IODP Consortium, Australian Institute of Nuclear Science and Engineering, Natural Environmental Research Council (NE/H014136/1, NE/H014268/1), the Cooperative Research Program of the Center for Advanced Marine Core Research (10B039, 11A013, 11B041), Ministry of Earth Sciences, Govt. of India (with partial support from DST & ISRO-GBP) and Japan Society for the Promotion of Science (JSPS NEXT-GR031).
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    Counting whales in a challenging, changing environment (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 4 (2014): 4170, doi:10.1038/srep04170.
    Beschreibung: Estimating abundance of Antarctic minke whales is central to the International Whaling Commission's conservation and management work and understanding impacts of climate change on polar marine ecosystems. Detecting abundance trends is problematic, in part because minke whales are frequently sighted within Antarctic sea ice where navigational safety concerns prevent ships from surveying. Using icebreaker-supported helicopters, we conducted aerial surveys across a gradient of ice conditions to estimate minke whale density in the Weddell Sea. The surveys revealed substantial numbers of whales inside the sea ice. The Antarctic summer sea ice is undergoing rapid regional change in annual extent, distribution, and length of ice-covered season. These trends, along with substantial interannual variability in ice conditions, affect the proportion of whales available to be counted by traditional shipboard surveys. The strong association between whales and the dynamic, changing sea ice requires reexamination of the power to detect trends in whale abundance or predict ecosystem responses to climate change.
    Beschreibung: This work received funding from the following institutions: Alfred Wegener Institute for Polar and Marine Research (AWI); Dutch Ministry of Agriculture, Nature and Food Quality (EL & I); German Federal Ministry of Food, Agriculture and Consumer Protection (BMELV); German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU); the Institute for Marine Resources and Ecosystem Studies (Wageningen IMARES); Johann Heinrich von Thu¨nen Institute (Federal Research Institute for Rural Areas, Forestry and Fisheries); the Netherlands Polar Programme (NPP) of the Netherlands Organisation for Scientific Research (NOW); Research and Technology Centre Westcoast (FTZ) of the University Kiel. RW was funded by a Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (proposal Nu 253407 (call reference: FP7- PEOPLE-2009-IIF).
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    MIxS-BE : a MIxS extension defining a minimum information standard for sequence data from the built environment (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in ISME Journal 8 (2014): 1-3, doi:10.1038/ismej.2013.176.
    Beschreibung: The need for metadata standards for microbe sampling in the built environment.
    Beschreibung: We would like to thank the Alfred P Sloan Foundation grant FP047325-01-PR for support for this project.
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  • 23
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    A reversal of fortunes : climate change ‘winners’ and ‘losers’ in Antarctic Peninsula penguins (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 4 (2014): 5024, doi:10.1038/srep05024.
    Beschreibung: Climate change is a major threat to global biodiversity. Antarctic ecosystems are no exception. Investigating past species responses to climatic events can distinguish natural from anthropogenic impacts. Climate change produces ‘winners’, species that benefit from these events and ‘losers’, species that decline or become extinct. Using molecular techniques, we assess the demographic history and population structure of Pygoscelis penguins in the Scotia Arc related to climate warming after the Last Glacial Maximum (LGM). All three pygoscelid penguins responded positively to post-LGM warming by expanding from glacial refugia, with those breeding at higher latitudes expanding most. Northern (Pygoscelis papua papua) and Southern (Pygoscelis papua ellsworthii) gentoo sub-species likely diverged during the LGM. Comparing historical responses with the literature on current trends, we see Southern gentoo penguins are responding to current warming as they did during post-LGM warming, expanding their range southwards. Conversely, Adélie and chinstrap penguins are experiencing a ‘reversal of fortunes’ as they are now declining in the Antarctic Peninsula, the opposite of their response to post-LGM warming. This suggests current climate warming has decoupled historic population responses in the Antarctic Peninsula, favoring generalist gentoo penguins as climate change ‘winners’, while Adélie and chinstrap penguins have become climate change ‘losers’.
    Beschreibung: We thank the Zoological Society of London, Quark Expeditions, Exodus Travels ltd., Oceanites, the Holly Hill Charitable Trust, the Charities Advisory Trust and an U.S. National Science Foundation (NSF) Office of Polar Programs grant (ANT-0739575) for funding.
    Schlagwort(e): Climate-change ecology ; Molecular ecology ; Molecular evolution ; Population genetics
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    Horizontal eddy energy flux in the world oceans diagnosed from altimetry data (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 4 (2014): 5316, doi:10.1038/srep05316.
    Beschreibung: During the propagation of coherent mesoscale eddies, they directly or indirectly induce many effects and interactions at different scales, implying eddies are actually serving as a kind of energy carrier or energy source for these eddy-related dynamic processes. To quantify this dynamically significant energy flow, the multi-year averaged horizontal eddy energy fluxes (EEFs) were estimated by using satellite altimetry data and a two-layer model based on hydrographic climatology. There is a strong net westward transport of eddy energy estimated at the mean value of ~13.3 GW north of 5°N and ~14.6 GW at the band 5°S ~ 44°S in the Southern Hemisphere. However, poleward of 44°S east-propagating eddies carry their energy eastward with an averaged net flux of ~3.2 GW. If confirmed, it would signify that geostrophic eddies not only contain the most of oceanic kinetic energy (KE), but also carry and spread a significant amount of energy with them.
    Beschreibung: This study is supported by Grants XDA11010202, 2011CB403505, 2013CB430303; Projects 41306016, U1033002, 40976021 of NNSFC and LTOZZ1304.
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    Oceanography : oxygen and climate dynamics (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Climate Change 4 (2014): 862-863, doi:10.1038/nclimate2386.
    Beschreibung: Low oxygen levels in tropical oceans shape marine ecosystems and biogeochemistry with climate change expected to expand these regions. Now, a study indicates that regional dynamics control tropical oxygen trends, bucking projected global reductions in ocean oxygen.
    Beschreibung: 2015-03-25
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  • 26
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    Extreme diving behaviour in devil rays links surface waters and the deep ocean (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 5 (2014): 4274, doi:10.1038/ncomms5274.
    Beschreibung: Ecological connections between surface waters and the deep ocean remain poorly studied despite the high biomass of fishes and squids residing at depths beyond the euphotic zone. These animals likely support pelagic food webs containing a suite of predators that include commercially important fishes and marine mammals. Here we deploy pop-up satellite archival transmitting tags on 15 Chilean devil rays (Mobula tarapacana) in the central North Atlantic Ocean, which provide movement patterns of individuals for up to 9 months. Devil rays were considered surface dwellers but our data reveal individuals descending at speeds up to 6.0 m s−1 to depths of almost 2,000 m and water temperatures 〈4 °C. The shape of the dive profiles suggests that the rays are foraging at these depths in deep scattering layers. Our results provide evidence of an important link between predators in the surface ocean and forage species occupying pelagic habitats below the euphotic zone in ocean ecosystems.
    Beschreibung: This research was partially supported by the Portuguese Foundation for Science and Technology/Ministry of Education and Science (FCT/MCTES-MEC) through individual support to P.A. (Cieˆncia 2008/POPH/QREN) and J.F. (SFRH/BPD/66532/2009) and the LARSyS Strategic Project (PEst/OE/EEI/LA00009/2011). This study was support by the US National Science Foundation (OCE 0825148 to S.R.T. and G.B.S.), The Harrison Foundation, Rodney and Elizabeth Berens, the King Abdullah University of Science and Technology (baseline research funds to M.L.B.) and the Woods Hole Oceanographic Institution.
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    Antarctic-wide array of high-resolution ice core records reveals pervasive lead pollution began in 1889 and persists today (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 4 (2014): 5848, doi:10.1038/srep05848.
    Beschreibung: Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead pollution at South Pole and throughout Antarctica by 1889 – beating polar explorers by more than 22 years. Unlike the Arctic where lead pollution peaked in the 1970s, lead pollution in Antarctica was as high in the early 20th century as at any time since industrialization. The similar timing and magnitude of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19th century and remains a significant source today. An estimated 660 t of industrial lead have been deposited over Antarctica during the past 130 years as a result of mid-latitude industrial emissions, with regional-to-global scale circulation likely modulating aerosol concentrations. Despite abatement efforts, significant lead pollution in Antarctica persists into the 21st century.
    Beschreibung: This work primarily was supported by the U.S. National Science Foundation Division of Polar Programs (research grants 9903744, 0538427, 0538416, 0968391, 1142166, 0632031; instrument grants 0216552, 0421412).
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    How unique was Hurricane Sandy? Sedimentary reconstructions of extreme flooding from New York Harbor (2014)
    Nature Publishing Group
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    Publikationsdatum: 2022-05-26
    Beschreibung: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 4 (2014): 7366, doi:10.1038/srep07366.
    Beschreibung: The magnitude of flooding in New York City by Hurricane Sandy is commonly believed to be extremely rare, with estimated return periods near or greater than 1000 years. However, the brevity of tide gauge records result in significant uncertainties when estimating the uniqueness of such an event. Here we compare resultant deposition by Hurricane Sandy to earlier storm-induced flood layers in order to extend records of flooding to the city beyond the instrumental dataset. Inversely modeled storm conditions from grain size trends show that a more compact yet more intense hurricane in 1821 CE probably resulted in a similar storm tide and a significantly larger storm surge. Our results indicate the occurrence of additional flood events like Hurricane Sandy in recent centuries, and highlight the inadequacies of the instrumental record in estimating current flood risk by such extreme events.
    Beschreibung: Funding for this work was provided by the Hudson River Foundation Expedited Grant #004/12E, the Hudson River Foundation Graduate Fellowship 02–13, the National Science Foundation (RAPID grant #1313859 and instrument and facility support via grant IF-0949313), and the Dalio Explore Fund.
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    Structural insight into activity enhancement and inhibition of H64A carbonic anhydrase II by imidazoles (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
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    Publikationsdatum: 2014-04-08
    Beschreibung: Human carbonic anhydrases (CAs) are zinc metalloenzymes that catalyze the hydration and dehydration of CO2 and HCO3−, respectively. The reaction follows a ping-pong mechanism, in which the rate-limiting step is the transfer of a proton from the zinc-bound solvent (OH−/H2O) in/out of the active site via His64, which is widely believed to be the proton-shuttling residue. The decreased catalytic activity (∼20-fold lower with respect to the wild type) of a variant of CA II in which His64 is replaced with Ala (H64A CA II) can be enhanced by exogenous proton donors/acceptors, usually derivatives of imidazoles and pyridines, to almost the wild-type level. X-ray crystal structures of H64A CA II in complex with four imidazole derivatives (imidazole, 1-methylimidazole, 2-methylimidazole and 4-methylimidazole) have been determined and reveal multiple binding sites. Two of these imidazole binding sites have been identified that mimic the positions of the `in' and `out' rotamers of His64 in wild-type CA II, while another directly inhibits catalysis by displacing the zinc-bound solvent. The data presented here not only corroborate the importance of the imidazole side chain of His64 in proton transfer during CA catalysis, but also provide a complete structural understanding of the mechanism by which imidazoles enhance (and inhibit when used at higher concentrations) the activity of H64A CA II.
    Schlagwort(e): human carbonic anhydraseH64Aactivity enhancementrescueactivationimidazole
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    The structure of a purple acid phosphatase involved in plant growth and pathogen defence exhibits a novel immunoglobulin-like fold (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
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    Publikationsdatum: 2014-04-08
    Beschreibung: Phosphatases function in the production, transport and recycling of inorganic phosphorus, which is crucial for cellular metabolism and bioenergetics, as well as in bacterial killing, since they are able to generate reactive oxygen species via Fenton chemistry. Diphosphonucleotide phosphatase/phosphodiesterase (PPD1), a glycoprotein plant purple acid phosphatase (PAP) from yellow lupin seeds, contains a bimetallic Fe–Mn catalytic site which is most active at acidic pH. Unlike other plant PAPs, PPD1 cleaves the pyrophosphate bond in diphosphonucleotides and the phosphodiester bond in various phosphodiesters. The homohexameric organization of PPD1, as revealed by a 1.65 Å resolution crystal structure and confirmed by solution X-ray scattering, is unique among plant PAPs, for which only homodimers have previously been reported. A phosphate anion is bound in a bidentate fashion at the active site, bridging the Fe and Mn atoms in a binding mode similar to that previously reported for sweet potato PAP, which suggests that common features occur in their catalytic mechanisms. The N-terminal domain of PPD1 has an unexpected and unique fibronectin type III-like fold that is absent in other plant PAPs. Here, the in vitro DNA-cleavage activity of PPD1 is demonstrated and it is proposed that the fibronectin III-like domain, which `overhangs' the active site, is involved in DNA selectivity, binding and activation. The degradation of DNA by PPD1 implies a role for PPD1 in plant growth and repair and in pathogen defence.
    Schlagwort(e): purple acid phosphatasediphosphonucleotide phosphatasephosphodiesterasePPD1bimetallic Fe–Mnfibronectin type III domaincrystal structureSAXS
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Acemetacin cocrystals and salts: structure solution from powder X-ray data and form selection of the piperazine salt (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
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    Publikationsdatum: 2014-04-08
    Beschreibung: Acemetacin (ACM) is a non-steroidal anti-inflammatory drug (NSAID), which causes reduced gastric damage compared with indomethacin. However, acemetacin has a tendency to form a less soluble hydrate in the aqueous medium. We noted difficulties in the preparation of cocrystals and salts of acemetacin by mechanochemical methods, because this drug tends to form a hydrate during any kind of solution-based processing. With the objective to discover a solid form of acemetacin that is stable in the aqueous medium, binary adducts were prepared by the melt method to avoid hydration. The coformers/salt formers reported are pyridine carboxamides [nicotinamide (NAM), isonicotinamide (INA), and picolinamide (PAM)], caprolactam (CPR), p-aminobenzoic acid (PABA), and piperazine (PPZ). The structures of an ACM–INA cocrystal and a binary adduct ACM–PABA were solved using single-crystal X-ray diffraction. Other ACM cocrystals, ACM–PAM and ACM–CPR, and the piperazine salt ACM–PPZ were solved from high-resolution powder X-ray diffraction data. The ACM–INA cocrystal is sustained by the acid...pyridine heterosynthon and N—H...O catemer hydrogen bonds involving the amide group. The acid...amide heterosynthon is present in the ACM–PAM cocrystal, while ACM–CPR contains carboxamide dimers of caprolactam along with acid–carbonyl (ACM) hydrogen bonds. The cocrystals ACM–INA, ACM–PAM and ACM–CPR are three-dimensional isostructural. The carboxyl...carboxyl synthon in ACM–PABA posed difficulty in assigning the position of the H atom, which may indicate proton disorder. In terms of stability, the salts were found to be relatively stable in pH 7 buffer medium over 24 h, but the cocrystals dissociated to give ACM hydrate during the same time period. The ACM–PPZ salt and ACM–nicotinamide cocrystal dissolve five times faster than the stable hydrate form, whereas the ACM–PABA adduct has 2.5 times faster dissolution rate. The pharmaceutically acceptable piperazine salt of acemetacin exhibits superior stability, faster dissolution rate and is able to overcome the hydration tendency of the reference drug.
    Schlagwort(e): cocrystalhydratemelt crystallizationpiperazinepowder X-ray diffractionstructure determination from powder data (SDPD)
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Serial crystallography on in vivo grown microcrystals using synchrotron radiation (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
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    Publikationsdatum: 2014-04-08
    Beschreibung: Crystal structure determinations of biological macromolecules are limited by the availability of sufficiently sized crystals and by the fact that crystal quality deteriorates during data collection owing to radiation damage. Exploiting a micrometre-sized X-ray beam, high-precision diffractometry and shutterless data acquisition with a pixel-array detector, a strategy for collecting data from many micrometre-sized crystals presented to an X-ray beam in a vitrified suspension is demonstrated. By combining diffraction data from 80 Trypanosoma brucei procathepsin B crystals with an average volume of 9 µm3, a complete data set to 3.0 Å resolution has been assembled. The data allowed the refinement of a structural model that is consistent with that previously obtained using free-electron laser radiation, providing mutual validation. Further improvements of the serial synchrotron crystallography technique and its combination with serial femtosecond crystallography are discussed that may allow the determination of high-resolution structures of micrometre-sized crystals.
    Schlagwort(e): protein microcrystallographyserial crystallographyin vivo grown microcrystals
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Femtosecond X-ray diffraction from two-dimensional protein crystals (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
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    Publikationsdatum: 2014-04-08
    Beschreibung: X-ray diffraction patterns from two-dimensional (2-D) protein crystals obtained using femtosecond X-ray pulses from an X-ray free-electron laser (XFEL) are presented. To date, it has not been possible to acquire transmission X-ray diffraction patterns from individual 2-D protein crystals due to radiation damage. However, the intense and ultrafast pulses generated by an XFEL permit a new method of collecting diffraction data before the sample is destroyed. Utilizing a diffract-before-destroy approach at the Linac Coherent Light Source, Bragg diffraction was acquired to better than 8.5 Å resolution for two different 2-D protein crystal samples each less than 10 nm thick and maintained at room temperature. These proof-of-principle results show promise for structural analysis of both soluble and membrane proteins arranged as 2-D crystals without requiring cryogenic conditions or the formation of three-dimensional crystals.
    Schlagwort(e): two-dimensional protein crystalfemtosecond crystallographysingle layer X-ray diffractionmembrane protein
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    New perspectives in biological crystallography (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
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    Publikationsdatum: 2014-04-08
    Schlagwort(e): biological crystallographyeditorialIUCrJ
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
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    Serial crystallography using synchrotron radiation (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-04-08
    Schlagwort(e): protein microcrystallographyserial crystallographyin vivo-grown microcrystals
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Anharmonicity and isomorphic phase transition: a multi-temperature X-ray single-crystal and powder diffraction study of 1-(2′-aminophenyl)-2-methyl-4-nitroimidazole (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-04-08
    Beschreibung: The harmonic model of atomic nuclear motions is usually enough for multipole modelling of high-resolution X-ray diffraction data; however, in some molecular crystals, such as 1-(2′-aminophenyl)-2-methyl-4-nitro-1H-imidazole [Paul, Kubicki, Jelsch et al. (2011). Acta Cryst. B67, 365–378], it may not be sufficient for a correct description of the charge-density distribution. Multipole refinement using harmonic atom vibrations does not lead to the best electron density model in this case and the so-called `shashlik-like' pattern of positive and negative residual electron density peaks is observed in the vicinity of some atoms. This slight disorder, which cannot be modelled by split atoms, was solved using third-order anharmonic nuclear motion (ANM) parameters. Multipole refinement of the experimental high-resolution X-ray diffraction data of 1-(2′-aminophenyl)-2-methyl-4-nitro-1H-imidazole at three different temperatures (10, 35 and 70 K) and a series of powder diffraction experiments (20 ≤ T ≤ 300 K) were performed to relate this anharmonicity observed for several light atoms (N atoms of amino and nitro groups, and O atoms of nitro groups) to an isomorphic phase transition reflected by a change in the b cell parameter around 65 K. The observed disorder may result from the coexistence of domains of two phases over a large temperature range, as shown by low-temperature powder diffraction.
    Schlagwort(e): anharmonicityisomorphic phase transitionexperimental charge densityX-ray closed-circuit helium cryostatHansen–Coppens modelmultiple-temperature powder diffraction
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    The enrichment ratio of atomic contacts in crystals, an indicator derived from the Hirshfeld surface analysis (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-04-08
    Beschreibung: The partitioning of space with Hirshfeld surfaces enables the analysis of fingerprint molecular interactions in crystalline environments. This study uses the decomposition of the crystal contact surface between pairs of interacting chemical species to derive an enrichment ratio. This quantity enables the analysis of the propensity of chemical species to form intermolecular interactions with themselves and other species. The enrichment ratio is obtained by comparing the actual contacts in the crystal with those computed as if all types of contacts had the same probability to form. The enrichments and contact tendencies were analyzed in several families of compounds, based on chemical composition and aromatic character. As expected, the polar contacts of the type H...N, H...O and H...S, which are generally hydrogen bonds, show enrichment values larger than unity. O...O and N...N contacts are impoverished while H...H interactions display enrichment ratios which are generally close to unity or slightly lower. In aromatic compounds, C...C contacts can display large enrichment ratios due to extensive π...π stacking in the crystal packings of heterocyclic compounds. C...C contacts are, however, less enriched in pure (C,H) hydrocarbons as π...π stacking is not so favourable from the electrostatic point of view compared with heterocycles. C...H contacts are favoured in (C,H) aromatics, but these interactions occur less in compounds containing O, N or S as some H atoms are then involved in hydrogen bonds. The study also highlights the fact that hydrogen is a prefered interaction partner for fluorine.
    Schlagwort(e): enrichment ratioHirshfeld surface analysiscrystal packingfingerprint plots
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 38
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    Chemical crystallography and crystal engineering (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Schlagwort(e): Editorialchemical crystallographycrystal engineering
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 39
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    Automated nucleic acid chain tracing in real time (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The crystallographic structure solution of nucleotides and nucleotide complexes is now commonplace. The resulting electron-density maps are often poorer than for proteins, and as a result interpretation in terms of an atomic model can require significant effort, particularly in the case of large structures. While model building can be performed automatically, as with proteins, the process is time-consuming, taking minutes to days depending on the software and the size of the structure. A method is presented for the automatic building of nucleotide chains into electron density which is fast enough to be used in interactive model-building software, with extended chain fragments built around the current view position in a fraction of a second. The speed of the method arises from the determination of the `fingerprint' of the sugar and phosphate groups in terms of conserved high-density and low-density features, coupled with a highly efficient scoring algorithm. Use cases include the rapid evaluation of an initial electron-density map, addition of nucleotide fragments to prebuilt protein structures, and in favourable cases the completion of the structure while automated model-building software is still running. The method has been incorporated into the Coot software package.
    Schlagwort(e): nucleic acid chain tracingCoot
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 40
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    Location of Cu2+ in CHA zeolite investigated by X-ray diffraction using the Rietveld/maximum entropy method (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Accurate structural models of reaction centres in zeolite catalysts are a prerequisite for mechanistic studies and further improvements to the catalytic performance. The Rietveld/maximum entropy method is applied to synchrotron powder X-ray diffraction data on fully dehydrated CHA-type zeolites with and without loading of catalytically active Cu2+ for the selective catalytic reduction of NOx with NH3. The method identifies the known Cu2+ sites in the six-membered ring and a not previously observed site in the eight-membered ring. The sum of the refined Cu occupancies for these two sites matches the chemical analysis and thus all the Cu is accounted for. It is furthermore shown that approximately 80% of the Cu2+ is located in the new 8-ring site for an industrially relevant CHA zeolite with Si/Al = 15.5 and Cu/Al = 0.45. Density functional theory calculations are used to corroborate the positions and identity of the two Cu sites, leading to the most complete structural description of dehydrated silicoaluminate CHA loaded with catalytically active Cu2+ cations.
    Schlagwort(e): CHA zeolitescatalytic activitylocation of Cu2+synchrotron powder X-ray diffractionRietveld/maximum entropy method
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 41
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    The indexing ambiguity in serial femtosecond crystallography (SFX) resolved using an expectation maximization algorithm (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Crystallographic auto-indexing algorithms provide crystal orientations and unit-cell parameters and assign Miller indices based on the geometric relations between the Bragg peaks observed in diffraction patterns. However, if the Bravais symmetry is higher than the space-group symmetry, there will be multiple indexing options that are geometrically equivalent, and hence many ways to merge diffraction intensities from protein nanocrystals. Structure factor magnitudes from full reflections are required to resolve this ambiguity but only partial reflections are available from each XFEL shot, which must be merged to obtain full reflections from these `stills'. To resolve this chicken-and-egg problem, an expectation maximization algorithm is described that iteratively constructs a model from the intensities recorded in the diffraction patterns as the indexing ambiguity is being resolved. The reconstructed model is then used to guide the resolution of the indexing ambiguity as feedback for the next iteration. Using both simulated and experimental data collected at an X-ray laser for photosystem I in the P63 space group (which supports a merohedral twinning indexing ambiguity), the method is validated.
    Schlagwort(e): indexing ambiguityserial femtosecond crystallography (SFX)XFELsprotein crystallographyexpectation maximization algorithm
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 42
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    Time dependence of X-ray polarizability of a crystal induced by an intense femtosecond X-ray pulse (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The time evolution of the electron density and the resulting time dependence of Fourier components of the X-ray polarizability of a crystal irradiated by highly intense femtosecond pulses of an X-ray free-electron laser (XFEL) is investigated theoretically on the basis of rate equations for bound electrons and the Boltzmann equation for the kinetics of the unbound electron gas. The photoionization, Auger process, electron-impact ionization, electron–electron scattering and three-body recombination have been implemented in the system of rate equations. An algorithm for the numerical solution of the rate equations was simplified by incorporating analytical expressions for the cross sections of all the electron configurations in ions within the framework of the effective charge model. Using this approach, the time dependence of the inner shell populations during the time of XFEL pulse propagation through the crystal was evaluated for photon energies between 4 and 12 keV and a pulse width of 40 fs considering a flux of 1012 photons pulse−1 (focusing on a spot size of ∼1 µm). This flux corresponds to a fluence ranging between 0.8 and 2.4 mJ µm−2. The time evolution of the X-ray polarizability caused by the change of the atomic scattering factor during the pulse propagation is numerically analyzed for the case of a silicon crystal. The time-integrated polarizability drops dramatically if the fluence of the X-ray pulse exceeds 1.6 mJ µm−2.
    Schlagwort(e): femtosecond pulseX-ray diffractionpolarizabilityelectron densityrate equations
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 43
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    Correlated changes in structure and viscosity during gelatinization and gelation of tapioca starch granules (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Melting of native tapioca starch granules in aqueous pastes upon heating is observed in situ using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) and solution viscometry. Correlated structure and viscosity changes suggest closely associated amylose and amylopectin chains in the semicrystalline layers, and the release of amylose chains for enhanced solution viscosity occurs largely after melting of the semicrystalline structure. Before melting, WAXS results reveal mixed crystals of A- and B-types (∼4:1 by weight), whereas SAXS results indicate that the semicrystalline layers are composed of lamellar blocklets of ca 43 nm domain size, with polydisperse crystalline (≃7.5 nm) and amorphous (≃1.1 nm) layers alternatively assembled into a lamellar spacing of ≃8.6 nm with 20% polydispersity. Upon melting, the semicrystalline lamellae disintegrate into disperse and molten amylopectin nanoclusters with dissolved and partially untangled amylose chains in the aqueous matrix which leads to increased solution viscosity. During subsequent cooling, gelation starts at around 347 K; successively increased solution viscosity coincides with the development of nanocluster aggregation to a fractal dimension ≃2.3 at 303 K, signifying increasing intercluster association through collapsed amylose chains owing to decreased solvency of the aqueous medium with decreasing temperature.
    Schlagwort(e): tapioca starch granulesgelatinizationgelationSAXS/WAXSviscosity
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 44
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    Molecular self-assembly of nylon-12 nanorods cylindrically confined to nanoporous alumina (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Molecular self-assembly of nylon-12 rods in self-organized nanoporous alumina cylinders with two different diameters (65 and 300 nm) is studied with transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) in symmetrical reflection mode. In a rod with a 300 nm diameter, the tendency of the hydrogen-bonding direction of a γ-form crystal parallel to the long axis of the rod is not clear because of weak two-dimensional confinement. In a rod with a diameter of 65 nm, the tendency of the hydrogen-bonding direction of a γ-form crystal parallel to the long axis of the rod is more distinct because of strong two-dimensional confinement. For the first time, selected-area electron diffraction (SAED) is applied in a transmission electron microscope to a polymer nanorod in order to determine the hydrogen-bond sheet and lamellar orientations. Results of TEM–SAED and WAXD showed that the crystals within the rod possess the γ-form of nylon-12 and that the b axis (stem axis) of the γ-form crystals is perpendicular to the long axis of the rod. These results revealed that only lamellae with 〈h0l〉 directions are able to grow inside the nanopores and the growth of lamellae with 〈hkl〉 (k ≠ 0) directions is stopped owing to impingements against the cylinder walls. The dominant crystal growth direction of the 65 nm rod in stronger two-dimensional confinement is in between the [−201] and [001] directions due to the development of a hydrogen-bonded sheet restricted along the long axis of the rod.
    Schlagwort(e): molecular self-assemblynanorodsselected-area electron diffractioncylindrical confinement
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 45
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    Viruses and viral proteins (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: For more than 30 years X-ray crystallography has been by far the most powerful approach for determining the structures of viruses and viral proteins at atomic resolution. The information provided by these structures, which covers many important aspects of the viral life cycle such as cell-receptor recognition, viral entry, nucleic acid transfer and genome replication, has extensively enriched our vision of the virus world. Many of the structures available correspond to potential targets for antiviral drugs against important human pathogens. This article provides an overview of the current knowledge of different structural aspects of the above-mentioned processes.
    Schlagwort(e): bacteriophagesgenome deliveryfusion proteinsRNA-dependent RNA polymerasesviral proteasesviral receptorsviruses
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 46
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    Contributions of charge-density research to medicinal chemistry (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: This article reviews efforts in accurate experimental charge-density studies with relevance to medicinal chemistry. Initially, classical charge-density studies that measure electron density distribution via least-squares refinement of aspherical-atom population parameters are summarized. Next, interaction density is discussed as an idealized situation resembling drug–receptor interactions. Scattering-factor databases play an increasing role in charge-density research, and they can be applied both to small-molecule and macromolecular structures in refinement and analysis; software development facilitates their use. Therefore combining both of these complementary branches of X-ray crystallography is recommended, and examples are given where such a combination already proved useful. On the side of the experiment, new pixel detectors are allowing rapid measurements, thereby enabling both high-throughput small-molecule studies and macromolecular structure determination to higher resolutions. Currently, the most ambitious studies compute intermolecular interaction energies of drug–receptor complexes, and it is recommended that future studies benefit from recent method developments. Selected new developments in theoretical charge-density studies are discussed with emphasis on its symbiotic relation to crystallography.
    Schlagwort(e): charge-density researchmedicinal chemistrydrug designinvariomHansen–Coppens multipole modelquantum theory of atoms in molecules
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 47
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    Capability of X-ray diffraction for the study of microstructure of metastable thin films (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Metastable phases are often used to design materials with outstanding properties, which cannot be achieved with thermodynamically stable compounds. In many cases, the metastable phases are employed as precursors for controlled formation of nanocomposites. This contribution shows how the microstructure of crystalline metastable phases and the formation of nanocomposites can be concluded from X-ray diffraction experiments by taking advantage of the high sensitivity of X-ray diffraction to macroscopic and microscopic lattice deformations and to the dependence of the lattice deformations on the crystallographic direction. The lattice deformations were determined from the positions and from the widths of the diffraction lines, the dependence of the lattice deformations on the crystallographic direction from the anisotropy of the line shift and the line broadening. As an example of the metastable system, the supersaturated solid solution of titanium nitride and aluminium nitride was investigated, which was prepared in the form of thin films by using cathodic arc evaporation of titanium and aluminium in a nitrogen atmosphere. The microstructure of the (Ti,Al)N samples under study was tailored by modifying the [Al]/[Ti] ratio in the thin films and the surface mobility of the deposited species.
    Schlagwort(e): metastable thin filmsmicrostructureX-ray diffraction
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 48
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    Binding site asymmetry in human transthyretin: insights from a joint neutron and X-ray crystallographic analysis using perdeuterated protein (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Human transthyretin has an intrinsic tendency to form amyloid fibrils and is heavily implicated in senile systemic amyloidosis. Here, detailed neutron structural studies of perdeuterated transthyretin are described. The analyses, which fully exploit the enhanced visibility of isotopically replaced hydrogen atoms, yield new information on the stability of the protein and the possible mechanisms of amyloid formation. Residue Ser117 may play a pivotal role in that a single water molecule is closely associated with the γ-hydrogen atoms in one of the binding pockets, and could be important in determining which of the two sites is available to the substrate. The hydrogen-bond network at the monomer–monomer interface is more extensive than that at the dimer–dimer interface. Additionally, the edge strands of the primary dimer are seen to be favourable for continuation of the β-sheet and the formation of an extended cross-β structure through sequential dimer couplings. It is argued that the precursor to fibril formation is the dimeric form of the protein.
    Schlagwort(e): transthyretinamyloid assemblyneutron crystallographydeuteration
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 49
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    The first X-ray diffraction measurements on Mars (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The Mars Science Laboratory landed in Gale crater on Mars in August 2012, and the Curiosity rover then began field studies on its drive toward Mount Sharp, a central peak made of ancient sediments. CheMin is one of ten instruments on or inside the rover, all designed to provide detailed information on the rocks, soils and atmosphere in this region. CheMin is a miniaturized X-ray diffraction/X-ray fluorescence (XRD/XRF) instrument that uses transmission geometry with an energy-discriminating CCD detector. CheMin uses onboard standards for XRD and XRF calibration, and beryl:quartz mixtures constitute the primary XRD standards. Four samples have been analysed by CheMin, namely a soil sample, two samples drilled from mudstones and a sample drilled from a sandstone. Rietveld and full-pattern analysis of the XRD data reveal a complex mineralogy, with contributions from parent igneous rocks, amorphous components and several minerals relating to aqueous alteration. In particular, the mudstone samples all contain one or more phyllosilicates consistent with alteration in liquid water. In addition to quantitative mineralogy, Rietveld refinements also provide unit-cell parameters for the major phases, which can be used to infer the chemical compositions of individual minerals and, by difference, the composition of the amorphous component.
    Schlagwort(e): X-ray diffractionMarsextraterrestrial mineralogyCuriosity rover
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 50
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    Beyond simple small-angle X-ray scattering: developments in online complementary techniques and sample environments (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Small- and wide-angle X-ray scattering (SAXS, WAXS) are standard tools in materials research. The simultaneous measurement of SAXS and WAXS data in time-resolved studies has gained popularity due to the complementary information obtained. Furthermore, the combination of these data with non X-ray based techniques, via either simultaneous or independent measurements, has advanced understanding of the driving forces that lead to the structures and morphologies of materials, which in turn give rise to their properties. The simultaneous measurement of different data regimes and types, using either X-rays or neutrons, and the desire to control parameters that initiate and control structural changes have led to greater demands on sample environments. Examples of developments in technique combinations and sample environment design are discussed, together with a brief speculation about promising future developments.
    Schlagwort(e): SAXSWAXSSANScomplementary techniquessample environment
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 51
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    Pressure effects on lipids and bio-membrane assemblies (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Membranes are amongst the most important biological structures; they maintain the fundamental integrity of cells, compartmentalize regions within them and play an active role in a wide range of cellular processes. Pressure can play a key role in probing the structure and dynamics of membrane assemblies, and is also critical to the biology and adaptation of deep-sea organisms. This article presents an overview of the effect of pressure on the mesostructure of lipid membranes, bilayer organization and lipid–protein assemblies. It also summarizes recent developments in high-pressure structural instrumentation suitable for experiments on membranes.
    Schlagwort(e): biological membraneslipidsbilayerslipid–protein assemblieshigh-pressure studies
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 52
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    Nanocrystalline materials: recent advances in crystallographic characterization techniques (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Most properties of nanocrystalline materials are shape-dependent, providing their exquisite tunability in optical, mechanical, electronic and catalytic properties. An example of the former is localized surface plasmon resonance (LSPR), the coherent oscillation of conduction electrons in metals that can be excited by the electric field of light; this resonance frequency is highly dependent on both the size and shape of a nanocrystal. An example of the latter is the marked difference in catalytic activity observed for different Pd nanoparticles. Such examples highlight the importance of particle shape in nanocrystalline materials and their practical applications. However, one may ask `how are nanoshapes created?', `how does the shape relate to the atomic packing and crystallography of the material?', `how can we control and characterize the external shape and crystal structure of such small nanocrystals?'. This feature article aims to give the reader an overview of important techniques, concepts and recent advances related to these questions. Nucleation, growth and how seed crystallography influences the final synthesis product are discussed, followed by shape prediction models based on seed crystallography and thermodynamic or kinetic parameters. The crystallographic implications of epitaxy and orientation in multilayered, core-shell nanoparticles are overviewed, and, finally, the development and implications of novel, spatially resolved analysis tools are discussed.
    Schlagwort(e): nanocrystalline materialsplasmonicsshape prediction models
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 53
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    Reconciling the regulatory role of Munc18 proteins in SNARE-complex assembly (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Membrane fusion is essential for human health, playing a vital role in processes as diverse as neurotransmission and blood glucose control. Two protein families are key: (1) the Sec1p/Munc18 (SM) and (2) the soluble N-ethylmaleimide-sensitive attachment protein receptor (SNARE) proteins. Whilst the essential nature of these proteins is irrefutable, their exact regulatory roles in membrane fusion remain controversial. In particular, whether SM proteins promote and/or inhibit the SNARE-complex formation required for membrane fusion is not resolved. Crystal structures of SM proteins alone and in complex with their cognate SNARE proteins have provided some insight, however, these structures lack the transmembrane spanning regions of the SNARE proteins and may not accurately reflect the native state. Here, we review the literature surrounding the regulatory role of mammalian Munc18 SM proteins required for exocytosis in eukaryotes. Our analysis suggests that the conflicting roles reported for these SM proteins may reflect differences in experimental design. SNARE proteins appear to require C-terminal immobilization or anchoring, for example through a transmembrane domain, to form a functional fusion complex in the presence of Munc18 proteins.
    Schlagwort(e): SM proteinsSNARE proteinssyntaxinMunc18membrane trafficking
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 54
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    Investigating increasingly complex macromolecular systems with small-angle X-ray scattering (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The biological solution small-angle X-ray scattering (BioSAXS) field has undergone tremendous development over recent decades. This means that increasingly complex biological questions can be addressed by the method. An intricate synergy between advances in hardware and software development, data collection and evaluation strategies and implementations that readily allow integration with complementary techniques result in significant results and a rapidly growing user community with ever increasing ambitions. Here, a review of these developments, by including a selection of novel BioSAXS methodologies and recent results, is given.
    Schlagwort(e): biological solution small-angle X-ray scattering (BioSAXS)synchrotron radiationbeamlinesstructural complexitybiostructural research
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 55
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    Diffuse scattering and partial disorder in complex structures (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The study of single-crystal diffuse scattering (SCDS) goes back almost to the beginnings of X-ray crystallography. Because SCDS arises from two-body correlations, it contains information about local (short-range) ordering in the sample, information which is often crucial in the attempt to relate structure to function. This review discusses the state of the field, including detectors and data collection and the modelling of SCDS using Monte Carlo and ab initio techniques. High-quality, three-dimensional volumes of SCDS data can now be collected at synchrotron light sources, allowing ever more detailed and quantitative analyses to be undertaken, and opening the way to approaches such as three-dimensional pair distribution function studies (3D-PDF) and automated refinement of a disorder model, powerful techniques that require large volumes of low-noise data.
    Schlagwort(e): single-crystal diffuse scatteringdisordersynchrotron light sources
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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  • 56
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    X-ray techniques for innovation in industry (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The smart specialization declared in the European program Horizon 2020, and the increasing cooperation between research and development found in companies and researchers at universities and research institutions have created a new paradigm where many calls for proposals require participation and funding from public and private entities. This has created a unique opportunity for large-scale facilities, such as synchrotron research laboratories, to participate in and support applied research programs. Scientific staff at synchrotron facilities have developed many advanced tools that make optimal use of the characteristics of the light generated by the storage ring. These tools have been exceptionally valuable for materials characterization including X-ray absorption spectroscopy, diffraction, tomography and scattering, and have been key in solving many research and development issues. Progress in optics and detectors, as well as a large effort put into the improvement of data analysis codes, have resulted in the development of reliable and reproducible procedures for materials characterization. Research with photons has contributed to the development of a wide variety of products such as plastics, cosmetics, chemicals, building materials, packaging materials and pharma. In this review, a few examples are highlighted of successful cooperation leading to solutions of a variety of industrial technological problems which have been exploited by industry including lessons learned from the Science Link project, supported by the European Commission, as a new approach to increase the number of commercial users at large-scale research infrastructures.
    Schlagwort(e): X-ray techniquesindustryinnovation
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Structure and function of dioxygenases in histone demethylation and DNA/RNA demethylation (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Iron(II) and 2-oxoglutarate (2OG)-dependent dioxygenases involved in histone and DNA/RNA demethylation convert the cosubstrate 2OG and oxygen to succinate and carbon dioxide, resulting in hydroxylation of the methyl group of the substrates and subsequent demethylation. Recent evidence has shown that these 2OG dioxygenases play vital roles in a variety of biological processes, including transcriptional regulation and gene expression. In this review, the structure and function of these dioxygenases in histone and nucleic acid demethylation will be discussed. Given the important roles of these 2OG dioxygenases, detailed analysis and comparison of the 2OG dioxygenases will guide the design of target-specific small-molecule chemical probes and inhibitors.
    Schlagwort(e): dioxygenaseshistone demethylationDNA/RNA demethylationN6-methyladenosineALKBH5
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    EXAFS and XANES analysis of oxides at the nanoscale (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Worldwide research activity at the nanoscale is triggering the appearance of new, and frequently surprising, materials properties in which the increasing importance of surface and interface effects plays a fundamental role. This opens further possibilities in the development of new multifunctional materials with tuned physical properties that do not arise together at the bulk scale. Unfortunately, the standard methods currently available for solving the atomic structure of bulk crystals fail for nanomaterials due to nanoscale effects (very small crystallite sizes, large surface-to-volume ratio, near-surface relaxation, local lattice distortions etc.). As a consequence, a critical reexamination of the available local-structure characterization methods is needed. This work discusses the real possibilities and limits of X-ray absorption spectroscopy (XAS) analysis at the nanoscale. To this end, the present state of the art for the interpretation of extended X-ray absorption fine structure (EXAFS) is described, including an advanced approach based on the use of classical molecular dynamics and its application to nickel oxide nanoparticles. The limits and possibilities of X-ray absorption near-edge spectroscopy (XANES) to determine several effects associated with the nanocrystalline nature of materials are discussed in connection with the development of ZnO-based dilute magnetic semiconductors (DMSs) and iron oxide nanoparticles.
    Schlagwort(e): EXAFSXANESoxide nanomaterialsnanocrystalline materials
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    High pressure and multiferroics materials: a happy marriage (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: The community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. The in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities.
    Schlagwort(e): high pressuremultiferroicsmaterials science
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Crystallography of metal–organic frameworks (2014)
    International Union of Crystallography (IUCr)
    In: IUCrJ
    Details
    Publikationsdatum: 2014-11-12
    Beschreibung: Metal–organic frameworks (MOFs) are one of the most intensely studied material types in recent times. Their networks, resulting from the formation of strong bonds between inorganic and organic building units, offer unparalled chemical diversity and pore environments of growing complexity. Therefore, advances in single-crystal X-ray diffraction equipment and techniques are required to characterize materials with increasingly larger surface areas, and more complex linkers. In addition, whilst structure solution from powder diffraction data is possible, the area is much less populated and we detail the current efforts going on here. We also review the growing number of reports on diffraction under non-ambient conditions, including the response of MOF structures to very high pressures. Such experiments are important due to the expected presence of stresses in proposed applications of MOFs – evidence suggesting rich and complex behaviour. Given the entwined and inseparable nature of their structure, properties and applications, it is essential that the field of structural elucidation is able to continue growing and advancing, so as not to provide a rate-limiting step on characterization of their properties and incorporation into devices and applications. This review has been prepared with this in mind.
    Schlagwort(e): MOFsnon-ambient crystallographycrystal growth
    Digitale ISSN: 2052-2525
    Thema: Geologie und Paläontologie , Physik
    Publiziert von International Union of Crystallography (IUCr)
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    Master recyclers: features and functions of bacteria associated with phytoplankton blooms (2014)
    Nature Publishing Group
    In:  Nature Reviews Microbiology, 12 (10). pp. 686-698.
    Details
    Publikationsdatum: 2020-06-23
    Beschreibung: Marine phytoplankton blooms are annual spring events that sustain active and diverse bloom-associated bacterial populations. Blooms vary considerably in terms of eukaryotic species composition and environmental conditions, but a limited number of heterotrophic bacterial lineages — primarily members of the Flavobacteriia, Alphaproteobacteria and Gammaproteobacteria — dominate these communities. In this Review, we discuss the central role that these bacteria have in transforming phytoplankton-derived organic matter and thus in biogeochemical nutrient cycling. On the basis of selected field and laboratory-based studies of flavobacteria and roseobacters, distinct metabolic strategies are emerging for these archetypal phytoplankton-associated taxa, which provide insights into the underlying mechanisms that dictate their behaviours during blooms.
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    Biosynthesis of magnetic nanostructures in a foreign organism by transfer of bacterial magnetosome gene clusters (2014)
    Nature Publishing Group
    In:  Nature Nanotechnology, 9 (3). pp. 193-197.
    Details
    Publikationsdatum: 2020-06-24
    Beschreibung: The synthetic production of monodisperse single magnetic domain nanoparticles at ambient temperature is challenging. In nature, magnetosomes--membrane-bound magnetic nanocrystals with unprecedented magnetic properties--can be biomineralized by magnetotactic bacteria. However, these microbes are difficult to handle. Expression of the underlying biosynthetic pathway from these fastidious microorganisms within other organisms could therefore greatly expand their nanotechnological and biomedical applications. So far, this has been hindered by the structural and genetic complexity of the magnetosome organelle and insufficient knowledge of the biosynthetic functions involved. Here, we show that the ability to biomineralize highly ordered magnetic nanostructures can be transferred to a foreign recipient. Expression of a minimal set of genes from the magnetotactic bacterium Magnetospirillum gryphiswaldense resulted in magnetosome biosynthesis within the photosynthetic model organism Rhodospirillum rubrum. Our findings will enable the sustainable production of tailored magnetic nanostructures in biotechnologically relevant hosts and represent a step towards the endogenous magnetization of various organisms by synthetic biology.
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    Master recyclers: features and functions of bacteria associated with phytoplankton blooms (2014)
    Nature Publishing Group
    In:  Nature Reviews Microbiology, 12 (10). pp. 686-698.
    Details
    Publikationsdatum: 2020-06-23
    Beschreibung: Marine phytoplankton blooms are annual spring events that sustain active and diverse bloom-associated bacterial populations. Blooms vary considerably in terms of eukaryotic species composition and environmental conditions, but a limited number of heterotrophic bacterial lineages — primarily members of the Flavobacteriia, Alphaproteobacteria and Gammaproteobacteria — dominate these communities. In this Review, we discuss the central role that these bacteria have in transforming phytoplankton-derived organic matter and thus in biogeochemical nutrient cycling. On the basis of selected field and laboratory-based studies of flavobacteria and roseobacters, distinct metabolic strategies are emerging for these archetypal phytoplankton-associated taxa, which provide insights into the underlying mechanisms that dictate their behaviours during blooms.
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    Life cycles, fitness decoupling and the evolution of multicellularity (2014)
    Nature Publishing Group
    In:  Nature, 515 (7525). pp. 75-79.
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    Publikationsdatum: 2018-04-03
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  • 65
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    Carbon isotope equilibration during sulphate-limited anaerobic oxidation of methane (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (3). pp. 190-194.
    Details
    Publikationsdatum: 2015-07-24
    Beschreibung: Collectively, marine sediments comprise the largest reservoir of methane on Earth. The flux of methane from the sea bed to the overlying water column is mitigated by the sulphate-dependent anaerobic oxidation of methane by marine microbes within a discrete sedimentary horizon termed the sulphate–methane transition zone. According to conventional isotope systematics, the biological consumption of methane leaves a residue of methane enriched in 13C (refs 1, 2, 3). However, in many instances the methane within sulphate–methane transition zones is depleted in 13C, consistent with the production of methane, and interpreted as evidence for the intertwined anaerobic oxidation and production of methane4, 5, 6. Here, we report results from experiments in which we incubated cultures of microbial methane consumers with methane and low levels of sulphate, and monitored the stable isotope composition of the methane and dissolved inorganic carbon pools over time. Residual methane became progressively enriched in 13C at sulphate concentrations above 0.5 mM, and progressively depleted in 13C below this threshold. We attribute the shift to 13C depletion during the anaerobic oxidation of methane at low sulphate concentrations to the microbially mediated carbon isotope equilibration between methane and carbon dioxide. We suggest that this isotopic effect could help to explain the 13C-depletion of methane in subseafloor sulphate–methane transition zones.
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    Three-dimensional organotypic culture: experimental models of mammalian biology and disease (2014)
    Nature Publishing Group
    In:  Nature Reviews Molecular Cell Biology, 15 (10). pp. 647-664.
    Details
    Publikationsdatum: 2020-06-23
    Beschreibung: Mammalian organs are challenging to study as they are fairly inaccessible to experimental manipulation and optical observation. Recent advances in three-dimensional (3D) culture techniques, coupled with the ability to independently manipulate genetic and microenvironmental factors, have enabled the real-time study of mammalian tissues. These systems have been used to visualize the cellular basis of epithelial morphogenesis, to test the roles of specific genes in regulating cell behaviours within epithelial tissues and to elucidate the contribution of microenvironmental factors to normal and disease processes. Collectively, these novel models can be used to answer fundamental biological questions and generate replacement human tissues, and they enable testing of novel therapeutic approaches, often using patient-derived cells.
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    Bumpy path to a warmer world (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (3). pp. 160-161.
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    Publikationsdatum: 2019-09-23
    Beschreibung: Decadal climate variability has long received limited attention. With the slow-down in surface warming since the late 1990s, the decadal scale has rightly become a focus of attention: for assessing climate change and its impacts, it is of critical importance
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    Persistent link between solar activity and Greenland climate during the Last Glacial Maximum (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (9). pp. 662-666.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: Changes in solar activity have previously been proposed to cause decadal- to millennial-scale fluctuations in both the modern and Holocene climates1. Direct observational records of solar activity, such as sunspot numbers, exist for only the past few hundred years, so solar variability for earlier periods is typically reconstructed from measurements of cosmogenic radionuclides such as 10Be and 14C from ice cores and tree rings2, 3. Here we present a high-resolution 10Be record from the ice core collected from central Greenland by the Greenland Ice Core Project (GRIP). The record spans from 22,500 to 10,000 years ago, and is based on new and compiled data4, 5, 6. Using 14C records7, 8 to control for climate-related influences on 10Be deposition, we reconstruct centennial changes in solar activity. We find that during the Last Glacial Maximum, solar minima correlate with more negative δ18O values of ice and are accompanied by increased snow accumulation and sea-salt input over central Greenland. We suggest that solar minima could have induced changes in the stratosphere that favour the development of high-pressure blocking systems located to the south of Greenland, as has been found in observations and model simulations for recent climate9, 10. We conclude that the mechanism behind solar forcing of regional climate change may have been similar under both modern and Last Glacial Maximum climate conditions.
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    Adaptation of a globally important coccolithophore to ocean warming and acidification (2014)
    Nature Publishing Group
    In:  Nature Climate Change, 4 (11). pp. 1024-1030.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: Although ocean warming and acidification are recognized as two major anthropogenic perturbations of today’s oceans we know very little about how marine phytoplankton may respond via evolutionary change. We tested for adaptation to ocean warming in combination with ocean acidification in the globally important phytoplankton species Emiliania huxleyi. Temperature adaptation occurred independently of ocean acidification levels. Growth rates were up to 16% higher in populations adapted for one year to warming when assayed at their upper thermal tolerance limit. Particulate inorganic (PIC) and organic (POC) carbon production was restored to values under present-day ocean conditions, owing to adaptive evolution, and were 101% and 55% higher under combined warming and acidification, respectively, than in non-adapted controls. Cells also evolved to a smaller size while they recovered their initial PIC:POC ratio even under elevated CO2. The observed changes in coccolithophore growth, calcite and biomass production, cell size and elemental composition demonstrate the importance of evolutionary processes for phytoplankton performance in a future ocean.
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    The evolution of cichlid fish egg-spots is linked with a cis-regulatory change (2014)
    Nature Publishing Group
    In:  Nature Communications, 5 (5149).
    Details
    Publikationsdatum: 2018-11-09
    Beschreibung: The origin of novel phenotypic characters is a key component in organismal diversification; yet, the mechanisms underlying the emergence of such evolutionary novelties are largely unknown. Here we examine the origin of egg-spots, an evolutionary innovation of the most species-rich group of cichlids, the haplochromines, where these conspicuous male fin colour markings are involved in mating. Applying a combination of RNAseq, comparative genomics and functional experiments, we identify two novel pigmentation genes, fhl2a and fhl2b, and show that especially the more rapidly evolving b-paralog is associated with egg-spot formation. We further find that egg-spot bearing haplochromines, but not other cichlids, feature a transposable element in the cis-regulatory region of fhl2b. Using transgenic zebrafish, we finally demonstrate that this region shows specific enhancer activities in iridophores, a type of pigment cells found in egg-spots, suggesting that a cis-regulatory change is causally linked to the gain of expression in egg-spot bearing haplochromines
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    Atlantic origin of observed and modelled freshwater anomalies in the Nordic Seas (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (11). pp. 801-805.
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    Publikationsdatum: 2018-04-03
    Beschreibung: Between 1965 and 1990, the waters of the Nordic Seas and the subpolar basins of the North Atlantic Ocean freshened substantially1. The Arctic Ocean also became less saline over this time, as a consequence of increasing runoff1, 2, 3, 4, but it is not clear whether flow from the Arctic Ocean was the main source of the Nordic Seas salinity anomaly. As a region of deep-water formation, the Nordic Seas are central to the Atlantic meridional overturning circulation, but this process is inhibited if the surface salinity is too low2. Here we use the instrumental record of Nordic Seas hydrography, along with a global ocean–sea-ice model hindcast simulation, to identify the sources and magnitude of freshwater that has accumulated in the Nordic Seas since 1950. We find that the freshwater anomalies within the Nordic Seas can mostly be explained by less salt entering the southern part of the basin with the relatively saline Atlantic inflow, with seemingly little contribution from the Arctic Ocean. We conclude that hydrographic changes in the Nordic Seas are primarily related to changes in the Atlantic Ocean. We infer that if the Atlantic inflow and Nordic Seas both freshen similarly, this would render the Atlantic meridional overturning circulation relatively insensitive to Nordic Seas freshwater content.
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    Hybrid shallow on-axis and deep off-axis hydrothermal circulation at fast-spreading ridges (2014)
    Nature Publishing Group
    In:  Nature, 508 (7497). pp. 508-512.
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    Publikationsdatum: 2019-09-23
    Beschreibung: Hydrothermal flow at oceanic spreading centres accounts for about ten per cent of all heat flux in the oceans and controls the thermal structure of young oceanic plates. It also influences ocean and crustal chemistry, provides a basis for chemosynthetic ecosystems, and has formed massive sulphide ore deposits throughout Earth’s history. Despite this, how and under what conditions heat is extracted, in particular from the lower crust, remains largely unclear. Here we present high-resolution, whole-crust, two- and three-dimensional simulations of hydrothermal flow beneath fast-spreading ridges that predict the existence of two interacting flow components, controlled by different physical mechanisms, that merge above the melt lens to feed ridge-centred vent sites. Shallow on-axis flow structures develop owing to the thermodynamic properties of water, whereas deeper off-axis flow is strongly shaped by crustal permeability, particularly the brittle–ductile transition. About 60 per cent of the discharging fluid mass is replenished on-axis by warm (up to 300 degrees Celsius) recharge flow surrounding the hot thermal plumes, and the remaining 40 per cent or so occurs as colder and broader recharge up to several kilometres away from the axis that feeds hot (500–700 degrees Celsius) deep-rooted off-axis flow towards the ridge. Despite its lower contribution to the total mass flux, this deep off-axis flow carries about 70 per cent of the thermal energy released at the ridge axis. This combination of two flow components explains the seismically determined thermal structure of the crust and reconciles previously incompatible models favouring either shallower on-axis or deeper off-axis hydrothermal circulation.
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    Facets of diazotrophy in the oxygen minimum zone waters off Peru (2014)
    Nature Publishing Group
    In:  The ISME Journal, 8 (11). pp. 2180-2192.
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    Publikationsdatum: 2017-03-09
    Beschreibung: Nitrogen fixation, the biological reduction of dinitrogen gas (N2) to ammonium (NH4+), is quantitatively the most important external source of new nitrogen (N) to the open ocean. Classically, the ecological niche of oceanic N2 fixers (diazotrophs) is ascribed to tropical oligotrophic surface waters, often depleted in fixed N, with a diazotrophic community dominated by cyanobacteria. Although this applies for large areas of the ocean, biogeochemical models and phylogenetic studies suggest that the oceanic diazotrophic niche may be much broader than previously considered, resulting in major implications for the global N-budget. Here, we report on the composition, distribution and abundance of nifH, the functional gene marker for N2 fixation. Our results show the presence of eight clades of diazotrophs in the oxygen minimum zone (OMZ) off Peru. Although proteobacterial clades dominated overall, two clusters affiliated to spirochaeta and archaea were identified. N2 fixation was detected within OMZ waters and was stimulated by the addition of organic carbon sources supporting the view that non-phototrophic diazotrophs were actively fixing dinitrogen. The observed co-occurrence of key functional genes for N2 fixation, nitrification, anammox and denitrification suggests that a close spatial coupling of N-input and N-loss processes exists in the OMZ off Peru. The wide distribution of diazotrophs throughout the water column adds to the emerging view that the habitat of marine diazotrophs can be extended to low oxygen/high nitrate areas. Furthermore, our statistical analysis suggests that NO2− and PO43− are the major factors affecting diazotrophic distribution throughout the OMZ. In view of the predicted increase in ocean deoxygenation resulting from global warming, our findings indicate that the importance of OMZs as niches for N2 fixation may increase in the futur
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    Potential climate engineering effectiveness and side effects during a high CO2-emissions scenario (2014)
    Nature Publishing Group
    In:  Nature Communications, 5 (3304).
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    Publikationsdatum: 2019-09-23
    Beschreibung: The realization that mitigation efforts to reduce CO2 emissions have, until now, been relatively ineffective has led to an increasing interest in climate engineering as a possible means of preventing potentially catastrophic consequences of climate change. While many studies have addressed the potential effectiveness of individual methods there have been few attempts to compare them. We use an Earth system model to compare the effectiveness and side effects of afforestation, artificial ocean upwelling, ocean iron fertilization, ocean alkalinization, and solar radiation management during a high CO2-emissions scenario. We find that even when applied continuously and at scales as large as currently deemed possible, all methods are, individually, either relatively ineffective with limited (〈8%) warming reductions, or they have severe side effects and cannot be stopped without causing rapid climate change. Our simulations suggest that the potential for these types of climate engineering to make up for failed mitigation may be very limited.
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    Helium anomalies suggest a fluid pathway from mantle to trench during the 2011 Tohoku-Oki earthquake (2014)
    Nature Publishing Group
    In:  Nature Communications, 5 . p. 3084.
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    Publikationsdatum: 2015-07-24
    Beschreibung: Geophysical evidence suggests that fluids along fault planes have an important role in generating earthquakes; however, the nature of these fluids has not been well defined. The 2011 magnitude 9.0 Tohoku-Oki earthquake ruptured the interface between the subducting Pacific plate and the overlying Okhotsk plate. Here we report a sharp increase in mantle-derived helium in bottom seawater near the rupture zone 1 month after the earthquake. The timing and location indicate that fluids were released from the mantle on the seafloor along the plate interface. The movement of the fluids was rapid, with a velocity of ~4 km per day and an uncertainty factor of four. This rate is much faster than what would be expected from pressure-gradient propagation, suggesting that over-pressurized fluid is discharged along the plate interface.
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    The impact of ocean deoxygenation on iron release from continental margin sediments (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (6). pp. 433-437.
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    Publikationsdatum: 2019-09-23
    Beschreibung: In the oceans’ high-nitrate–low-chlorophyll regions, such as the Peru/Humboldt Current system and the adjacent eastern equatorial Pacific1, primary productivity is limited by the micronutrient iron. Within the Peruvian upwelling area, bioavailable iron is released from the reducing continental margin sediments2. The magnitude of this seafloor source could change with fluctuations in the extension or intensity of the oxygen minimum zones3, 4. Here we show that measurements of molybdenum, uranium and iron concentrations can be used as a proxy for sedimentary iron release, and use this proxy to assess iron release from the sea floor beneath the Peru upwelling system during the past 140,000 years. We observe a coupling between levels of denitrification, as indicated by nitrogen isotopes, trace metal proxies for oxygenation, and sedimentary iron concentrations. Specifically, periods with poor upper ocean oxygenation are characterized by more efficient iron retention in the sediment and a diminished iron supply to the water column. We attribute efficient iron retention under more reducing conditions to widespread sulphidic conditions in the surface sediment and concomitant precipitation of iron sulphides. We argue that iron release from continental margin sediments is most effective in a narrow redox window where neither oxygen nor sulphide is present. We therefore suggest that future deoxygenation in the Peru upwelling area would be unlikely to result in increased iron availability, whereas in weaker oxygen minimum zones partial deoxygenation may enhance the iron supply.
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    Stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (9). pp. 671-676.
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    Publikationsdatum: 2019-09-23
    Beschreibung: Animal burrowing and sediment-mixing (bioturbation) began during the run up to the Ediacaran/Cambrian boundary1, 2, 3, initiating a transition4, 5 between the stratified Precambrian6 and more well-mixed Phanerozoic7 sedimentary records, against the backdrop of a variable8, 9 global oxygen reservoir probably smaller in size than present10, 11. Phosphorus is the long-term12 limiting nutrient for oxygen production via burial of organic carbon13, and its retention (relative to carbon) within organic matter in marine sediments is enhanced by bioturbation14, 15, 16, 17, 18. Here we explore the biogeochemical implications of a bioturbation-induced organic phosphorus sink in a simple model. We show that increased bioturbation robustly triggers a net decrease in the size of the global oxygen reservoir—the magnitude of which is contingent upon the prescribed difference in carbon to phosphorus ratios between bioturbated and laminated sediments. Bioturbation also reduces steady-state marine phosphate levels, but this effect is offset by the decline in iron-adsorbed phosphate burial that results from a decrease in oxygen concentrations. The introduction of oxygen-sensitive bioturbation to dynamical model runs is sufficient to trigger a negative feedback loop: the intensity of bioturbation is limited by the oxygen decrease it initially causes. The onset of this feedback is consistent with redox variations observed during the early Cambrian rise of bioturbation, leading us to suggest that bioturbation helped to regulate early oxygen and phosphorus cycles.
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    Insights from Antarctica on volcanic forcing during the Common Era (2014)
    Nature Publishing Group
    In:  Nature Climate Change, 4 (8). pp. 693-697.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: Assessments of climate sensitivity to projected greenhouse gas concentrations underpin environmental policy decisions, with such assessments often based on model simulations of climate during recent centuries and millennia1, 2, 3. These simulations depend critically on accurate records of past aerosol forcing from global-scale volcanic eruptions, reconstructed from measurements of sulphate deposition in ice cores4, 5, 6. Non-uniform transport and deposition of volcanic fallout mean that multiple records from a wide array of ice cores must be combined to create accurate reconstructions. Here we re-evaluated the record of volcanic sulphate deposition using a much more extensive array of Antarctic ice cores. In our new reconstruction, many additional records have been added and dating of previously published records corrected through precise synchronization to the annually dated West Antarctic Ice Sheet Divide ice core7, improving and extending the record throughout the Common Era. Whereas agreement with existing reconstructions is excellent after 1500, we found a substantially different history of volcanic aerosol deposition before 1500; for example, global aerosol forcing values from some of the largest eruptions (for example, 1257 and 1458) previously were overestimated by 20–30% and others underestimated by 20–50%.
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    Eddy transport as a key component of the Antarctic overturning circulation (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 . pp. 879-884.
    Details
    Publikationsdatum: 2017-02-20
    Beschreibung: The exchange of water masses across the Antarctic continental shelf break regulates the export of dense shelf waters to depth as well as the transport of warm, mid-depth waters towards ice shelves and glacial grounding lines1. The penetration of the warmer mid-depth waters past the shelf break has been implicated in the pronounced loss of ice shelf mass over much of west Antarctica2, 3, 4. In high-resolution, regional circulation models, the Antarctic shelf break hosts an energetic mesoscale eddy field5, 6, but observations that capture this mesoscale variability have been limited. Here we show, using hydrographic data collected from ocean gliders, that eddy-induced transport is a primary contributor to mass and property fluxes across the slope. Measurements along ten cross-shelf hydrographic sections show a complex velocity structure and a stratification consistent with an onshore eddy mass flux. We show that the eddy transport and the surface wind-driven transport make comparable contributions to the total overturning circulation. Eddy-induced transport is concentrated in the warm, intermediate layers away from frictional boundaries. We conclude that understanding mesoscale dynamics will be critical for constraining circumpolar heat fluxes and future rates of retreat of Antarctic ice shelves.
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    Vertical structure of stratospheric water vapour trends derived from merged satellite data (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (10). pp. 768-776.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: Stratospheric water vapour is a powerful greenhouse gas. The longest available record from balloon observations over Boulder, Colorado, USA shows increases in stratospheric water vapour concentrations that cannot be fully explained by observed changes in the main drivers, tropical tropopause temperatures and methane. Satellite observations could help resolve the issue, but constructing a reliable long-term data record from individual short satellite records is challenging. Here we present an approach to merge satellite data sets with the help of a chemistry-climate model nudged to observed meteorology. We use the models' water vapour as a transfer function between data sets that overcomes issues arising from instrument drift and short overlap periods. In the lower stratosphere, our water vapour record extends back to 1988 and water vapour concentrations largely follow tropical tropopause temperatures. Lower and mid-stratospheric long-term trends are negative, and the trends from Boulder are shown not to be globally representative. In the upper stratosphere, our record extends back to 1986 and shows positive long-term trends. The altitudinal differences in the trends are explained by methane oxidation together with a strengthened lower-stratospheric and a weakened upper-stratospheric circulation inferred by this analysis. Our results call into question previous estimates of surface radiative forcing based on presumed global long-term increases in water vapour concentrations in the lower stratosphere.
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    Seismic precursors linked to super-critical fluids at oceanic transform faults (2014)
    Nature Publishing Group
    In:  Nature Geoscience, 7 (10). pp. 757-761.
    Details
    Publikationsdatum: 2015-07-24
    Beschreibung: Large earthquakes on mid-ocean ridge transform faults are commonly preceded by foreshocks1, 2, 3 and changes in the seismic properties of the fault zone3. These seismic precursors could be linked to fluid-related processes2, 3. Hydrothermal fluids within young, hot crust near the intersection of oceanic transform faults are probably in a supercritical condition4. At constant temperature, supercritical fluids become significantly more compressible with decreasing pressure, with potential impacts on fault behaviour. Here we use a theoretical model to show that oceanic transform faults can switch from dilatant and progressive deformation to rupture in response to fluid-related processes. We assume that the fault core material behaves according to a Cam-clay-type5 constitutive law, which is commonly used to account for the behaviour of clays. According to our model, we find that the fault is initially stable, with stresses gradually increasing over a timescale of years in response to tectonic loading. The fault evolves into a metastable phase, lasting a few days, during which the fault rocks dilate and pore pressures decrease, causing the compressibility of the supercritical fluids to increase. This in turn triggers fault-slip instability that creates foreshock swarms. In the final phase, the fault fails in the mainshock rupture. Our results imply that seismic precursors are caused by changes in fluid pressure which result in variations in fluid compressibility, in response to rock deformation just before rupture.
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    Madagascar corals track sea surface temperature variability in the Agulhas Current core region over the past 334 years (2014)
    Nature Publishing Group
    In:  Scientific Reports, 4 . p. 4393.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: The Agulhas Current (AC) is the strongest western boundary current in the Southern Hemisphere and is key for weather and climate patterns, both regionally and globally. Its heat transfer into both the midlatitude South Indian Ocean and South Atlantic is of global significance. A new composite coral record (Ifaty and Tulear massive Porites corals), is linked to historical AC sea surface temperature (SST) instrumental data, showing robust correlations. The composite coral SST data start in 1660 and comprise 200 years more than the AC instrumental record. Numerical modelling exhibits that this new coral derived SST record is representative for the wider core region of the AC. AC SSTs variabilities show distinct cooling through the Little Ice Age and warming during the late 18th, 19th and 20th century, with significant decadal variability superimposed. Furthermore, the AC SSTs are teleconnected with the broad southern Indian and Atlantic Oceans, showing that the AC system is pivotal for inter-ocean heat exchange south of Africa.
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    Subduction of the oceanic Hikurangi Plateau and its impact on the Kermadec arc (2014)
    Nature Publishing Group
    In:  Nature Communications, 5 (Article 4923).
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: Large igneous province subduction is a rare process on Earth. A modern example is the subduction of the oceanic Hikurangi Plateau beneath the southern Kermadec arc, offshore New Zealand. This segment of the arc has the largest total lava volume erupted and the highest volcano density of the entire Kermadec arc. Here we show that Kermadec arc lavas south of B32°S have elevated Pb and Sr and low Nd isotope ratios, which argues, together with increasing seafloor depth, forearc retreat and crustal thinning, for initial Hikurangi Plateau—Kermadec arc collision B250 km north of its present position. The combined data set indicates that a much larger portion of the Hikurangi Plateau (the missing Ontong Java Nui piece) than previously believed has already been subducted. Oblique plate convergence caused southward migration of the thickened and buoyant oceanic plateau crust, creating a buoyant ‘Hikurangi’ me´lange beneath the Moho that interacts with ascending arc melts.
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    Alternatives to vitamin B 1 uptake revealed with discovery of riboswitches in multiple marine eukaryotic lineages (2014)
    Nature Publishing Group
    In:  The ISME Journal, 8 (12). pp. 2517-2529.
    Details
    Publikationsdatum: 2019-03-05
    Beschreibung: Vitamin B 1 (thiamine pyrophosphate, TPP) is essential to all life but scarce in ocean surface waters. In many bacteria and a few eukaryotic groups thiamine biosynthesis genes are controlled by metabolite-sensing mRNA-based gene regulators known as riboswitches. Using available genome sequences and transcriptomes generated from ecologically important marine phytoplankton, we identified 31 new eukaryotic riboswitches. These were found in alveolate, cryptophyte, haptophyte and rhizarian phytoplankton as well as taxa from two lineages previously known to have riboswitches (green algae and stramenopiles). The predicted secondary structures bear hallmarks of TPP-sensing riboswitches. Surprisingly, most of the identified riboswitches are affiliated with genes of unknown function, rather than characterized thiamine biosynthesis genes. Using qPCR and growth experiments involving two prasinophyte algae, we show that expression of these genes increases significantly under vitamin B 1 -deplete conditions relative to controls. Pathway analyses show that several algae harboring the uncharacterized genes lack one or more enzymes in the known TPP biosynthesis pathway. We demonstrate that one such alga, the major primary producer Emiliania huxleyi, grows on 4-amino-5-hydroxymethyl-2-methylpyrimidine (a thiamine precursor moiety) alone, although long thought dependent on exogenous sources of thiamine. Thus, overall, we have identified riboswitches in major eukaryotic lineages not known to undergo this form of gene regulation. In these phytoplankton groups, riboswitches are often affiliated with widespread thiamine-responsive genes with as yet uncertain roles in TPP pathways. Further, taxa with 'incomplete' TPP biosynthesis pathways do not necessarily require exogenous vitamin B 1, making vitamin control of phytoplankton blooms more complex than the current paradigm suggests. © 2014 International Society for Microbial Ecology. All rights reserved.
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    Hollow rhodoliths increase Svalbard's shelf biodiversity (2014)
    Nature Publishing Group
    In:  Scientific Reports, 4 (Article number: 6972).
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    Publikationsdatum: 2020-09-07
    Beschreibung: Rhodoliths are coralline red algal assemblages that commonly occur in marine habitats from the tropics to polar latitudes. They form rigid structures of high-magnesium calcite and have a good fossil record. Here I show that rhodoliths are ecosystem engineers in a high Arctic environment that increase local biodiversity by providing habitat. Gouged by boring mussels, originally solid rhodoliths become hollow ecospheres intensely colonised by benthic organisms. In the examined shelf areas, biodiversity in rhodolith-bearing habitats is significantly greater than in habitats without rhodoliths and hollow rhodoliths yield a greater biodiversity than solid ones. This biodiversity, however, is threatened because hollow rhodoliths take a long time to form and are susceptible to global change and anthropogenic impacts such as trawl net fisheries that can destroy hollow rhodoliths. Rhodoliths and other forms of coralline red algae play a key role in a plurality of environments and need improved management and protection plans.
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    Eruption of a deep-sea mud volcano triggers rapid sediment movement (2014)
    Nature Publishing Group
    In:  Nature Communications, 5 (5385).
    Details
    Publikationsdatum: 2019-07-10
    Beschreibung: 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 Hakon 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 0.4m per day, and significant emissions of methane and CO2 from the seafloor.
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    Concentrations and ratios of particulate organic carbon, nitrogen, and phosphorus in the global ocean (2014)
    Nature Publishing Group
    In:  Scientific Data, 1 (1). Art.Nr. 140048.
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    Publikationsdatum: 2020-05-13
    Beschreibung: Knowledge of concentrations and elemental ratios of suspended particles are important for understanding many biogeochemical processes in the ocean. These include patterns of phytoplankton nutrient limitation as well as linkages between the cycles of carbon and nitrogen or phosphorus. To further enable studies of ocean biogeochemistry, we here present a global dataset consisting of 100,605 total measurements of particulate organic carbon, nitrogen, or phosphorus analyzed as part of 70 cruises or time-series. The data are globally distributed and represent all major ocean regions as well as different depths in the water column. The global median C:P, N:P, and C:N ratios are 163, 22, and 6.6, respectively, but the data also includes extensive variation between samples from different regions. Thus, this compilation will hopefully assist in a wide range of future studies of ocean elemental ratios.
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    Self-recognition in corals facilitates deep-sea habitat engineering (2014)
    Nature Publishing Group
    In:  Scientific Reports, 4 . p. 6782.
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    Publikationsdatum: 2017-02-02
    Beschreibung: The ability of coral reefs to engineer complex three-dimensional habitats is central to their success and the rich biodiversity they support. In tropical reefs, encrusting coralline algae bind together substrates and dead coral framework to make continuous reef structures, but beyond the photic zone, the cold-water coral Lophelia pertusa also forms large biogenic reefs, facilitated by skeletal fusion. Skeletal fusion in tropical corals can occur in closely related or juvenile individuals as a result of non-aggressive skeletal overgrowth or allogeneic tissue fusion, but contact reactions in many species result in mortality if there is no ‘self-recognition’ on a broad species level. This study reveals areas of ‘flawless’ skeletal fusion in Lophelia pertusa, potentially facilitated by allogeneic tissue fusion, are identified as having small aragonitic crystals or low levels of crystal organisation, and strong molecular bonding. Regardless of the mechanism, the recognition of ‘self’ between adjacent L. pertusa colonies leads to no observable mortality, facilitates ecosystem engineering and reduces aggression-related energetic expenditure in an environment where energy conservation is crucial. The potential for self-recognition at a species level, and subsequent skeletal fusion in framework-forming cold-water corals is an important first step in understanding their significance as ecological engineers in deep-seas worldwide.
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    An environmental bacterial taxon with a large and distinct metabolic repertoire (2014)
    Nature Publishing Group
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    Publikationsdatum: 2023-02-14
    Beschreibung: Cultivated bacteria such as actinomycetes are a highly useful source of biomedically important natural products. However, such ‘talented’ producers represent only a minute fraction of the entire, mostly uncultivated, prokaryotic diversity. The uncultured majority is generally perceived as a large, untapped resource of new drug candidates, but so far it is unknown whether taxa containing talented bacteria indeed exist. Here we report the single-cell- and metagenomics-based discovery of such producers. Two phylotypes of the candidate genus ‘Entotheonella’ with genomes of greater than 9 megabases and multiple, distinct biosynthetic gene clusters co-inhabit the chemically and microbially rich marine sponge Theonella swinhoei. Almost all bioactive polyketides and peptides known from this animal were attributed to a single phylotype. ‘Entotheonella’ spp. are widely distributed in sponges and belong to an environmental taxon proposed here as candidate phylum ‘Tectomicrobia’. The pronounced bioactivities and chemical uniqueness of ‘Entotheonella’ compounds provide significant opportunities for ecological studies and drug discovery.
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    Pan genome of the phytoplankton Emiliania underpins its global distribution (2013)
    Nature Publishing Group
    In:  EPIC3Nature, Nature Publishing Group, ISSN: 0028-0836
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    Publikationsdatum: 2019-03-08
    Beschreibung: Coccolithophores have influenced the global climate for over 200 million years1. These marine phytoplankton can account for 20 per cent of total carbon fixation in some systems2. They form blooms that can occupy hundreds of thousands of square kilometres and are distinguished by their elegantly sculpted calcium carbonate exoskeletons (coccoliths), rendering themvisible fromspace3.Although coccolithophores export carbon in the form of organic matter and calcite to the sea floor, they also release CO2 in the calcification process. Hence, they have a complex influence on the carbon cycle, driving either CO2 production or uptake, sequestration and export to the deep ocean4. Here we report the first haptophyte reference genome, from the coccolithophore Emiliania huxleyi strain CCMP1516, and sequences from 13 additional isolates. Our analyses reveal a pan genome (core genes plus genes distributed variably between strains) probably supported by an atypical complement of repetitive sequence in the genome. Comparisons across strains demonstrate thatE. huxleyi, which has long been considered a single species, harbours extensive genome variability reflected in different metabolic repertoires. Genome variability within this species complex seems to underpin its capacity both to thrive in habitats ranging from the equator to the subarctic and to form large-scale episodic blooms under a wide variety of environmental conditions.
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    Clues from joint inversion of tsunami and geodetic data of the 2011 Tohoku-oki earthquake (2013)
    Nature Publishing Group
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    Publikationsdatum: 2017-04-04
    Beschreibung: The 2011 Tohoku-oki (Mw 9.1) earthquake is so far the best-observed megathrust rupture, which allowed the collection of unprecedented offshore data. The joint inversion of tsunami waveforms (DART buoys, bottom pressure sensors, coastal wave gauges, and GPS-buoys) and static geodetic data (onshore GPS, seafloor displacements obtained by a GPS/acoustic combination technique), allows us to retrieve the slip distribution on a non-planar fault. We show that the inclusion of near-source data is necessary to image the details of slip pattern (maximum slip ,48 m, up to ,35 m close to the Japan trench), which generated the large and shallow seafloor coseismic deformations and the devastating inundation of the Japanese coast. We investigate the relation between the spatial distribution of previously inferred interseismic coupling and coseismic slip and we highlight the importance of seafloor geodetic measurements to constrain the interseismic coupling, which is one of the key-elements for long-term earthquake and tsunami hazard assessment.
    Beschreibung: Published
    Beschreibung: 385
    Beschreibung: 3.1. Fisica dei terremoti
    Beschreibung: N/A or not JCR
    Beschreibung: restricted
    Schlagwort(e): Tohoku ; Subduction ; Tsunami ; Inverse problem ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Sea Surface Temperature of the mid-Piacenzian Ocean: A Data-Model Comparison (2013)
    Nature Publishing Group
    In:  EPIC3Scientific Reports, Nature Publishing Group, 3(2013), ISSN: 2045-2322
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    Publikationsdatum: 2019-07-17
    Beschreibung: The mid-Piacenzian climate represents the most geologically recent interval of long-term average warmth relative to the last million years, and shares similarities with the climate projected for the end of the 21st century. As such, it represents a natural experiment from which we can gain insight into potential climate change impacts, enabling more informed policy decisions for mitigation and adaptation. Here, we present the first systematic comparison of Pliocene sea surface temperature (SST) between an ensemble of eight climate model simulations produced as part of PlioMIP (Pliocene Model Intercomparison Project) with the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) Project mean annual SST field. Our results highlight key regional and dynamic situations where there is discord between the palaeoenvironmental reconstruction and the climate model simulations. These differences have led to improved strategies for both experimental design and temporal refinement of the palaeoenvironmental reconstruction.
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    Challenges in reconstructing terrestrial warming of the Pliocene revealed by data-model discord (2013)
    Nature Publishing Group
    In:  EPIC3Nature Climate Change, Nature Publishing Group, ISSN: 1758-678X
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    Publikationsdatum: 2019-07-17
    Beschreibung: Comparing simulations of key warm periods in Earth history with contemporaneous geological proxy data is a useful approach for evaluating the ability of climate models to simulate warm, high-CO2 climates that are unprecedented in the more recent past. Here we use a global data set of confidence-assessed, proxy-based temperature estimates and biome reconstructions to assess the ability of eight models to simulate warm terrestrial climates of the Pliocene epoch. The Late Pliocene, 3.6–2.6 million years ago, is an accessible geological interval to understand climate processes of a warmer world. We show that model-predicted surface air temperatures reveal a substantial cold bias in the Northern Hemisphere. Particularly strong data–model mismatches in mean annual temperatures (up to 18 °C) exist in northern Russia. Our model sensitivity tests identify insufficient temporal constraints hampering the accurate configuration of model boundary conditions as an important factor impacting on data–model discrepancies. We conclude that to allow a more robust evaluation of the ability of present climate models to predict warm climates, future Pliocene data–model comparison studies should focus on orbitally defined time slices.
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    Eemian interglacial reconstructed from a Greenland folded ice core (2013)
    Nature Publishing Group
    In:  EPIC3Nature, Nature Publishing Group, 493(7433), pp. 489-494, ISSN: 0028-0836
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    Publikationsdatum: 2017-10-18
    Beschreibung: Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling (‘NEEM’) ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 ± 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 ± 250 metres, reaching surface elevations 122,000 years ago of 130 ± 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.
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    Terrestrische Habitate in Arktis und Antarktis Botanische, mikrobiologische und bodenkundliche Forschungen am Institut für Polarökologie (IPÖ) (2013)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 83(1), pp. 35-45, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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    Das Institut für Polarökologie der Christian-Albrechts-Universität und die Polarforschung in Kiel (2013)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 83(1), pp. 1-15, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
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    Biologie der Polarmeere: Dreißig Jahre biologische Meeresforschung am Institut für Polarökologie (IPÖ) in Kiel (2013)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 83(1), pp. 17-33, ISSN: 00322490
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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    Call characteristics of high-double trill leopard seal (Hydrurga leptonyx) vocalizations from three Antarctic locations (2013)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 83(2), pp. 63-71, ISSN: 00322490
    Details
    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
    Format: application/pdf
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    Towards collective circum-Antarctic passive acoustic monitoring: The Southern Ocean Hydrophone Network (SOHN) (2013)
    Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research
    In:  EPIC3Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 83(2), pp. 47-61, ISSN: 00322490
    Details
    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: "Polarforschung" , peerRev
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    First biological measurements of deep-sea corals from the Red Sea (2013)
    Nature Publishing Group
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Scientific Reports 3 (2013): 2802, doi:10.1038/srep02802.
    Beschreibung: It is usually assumed that metabolic constraints restrict deep-sea corals to cold-water habitats, with ‘deep-sea’ and ‘cold-water’ corals often used as synonymous. Here we report on the first measurements of biological characters of deep-sea corals from the central Red Sea, where they occur at temperatures exceeding 20°C in highly oligotrophic and oxygen-limited waters. Low respiration rates, low calcification rates, and minimized tissue cover indicate that a reduced metabolism is one of the key adaptations to prevailing environmental conditions. We investigated four sites and encountered six species of which at least two appear to be undescribed. One species is previously reported from the Red Sea but occurs in deep cold waters outside the Red Sea raising interesting questions about presumed environmental constraints for other deep-sea corals. Our findings suggest that the present understanding of deep-sea coral persistence and resilience needs to be revisited.
    Schlagwort(e): Ecosystem ecology ; Biodiversity ; Genetics ; Metabolism
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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    Format: application/msword
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