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  • Springer  (408)
  • 2015-2019  (408)
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  • 1
    Publication Date: 2024-06-07
    Description: Marine sponges and other sessile macro-organisms were collected at a shallow water hydrothermal site in Eyjafjörður, Iceland. Bacteria were isolated from the organisms using selective media for actinomycetes, and the isolates were screened for antimicrobial activity. A total of 111 isolates revealed antimicrobial activity displaying different antimicrobial patterns which indicates production of various compounds. Known test strains were grown in the presence of ethyl acetate extracts from one selected isolate, and a clear growth inhibition of Staphylococcus aureus was observed down to 0.1 % extract concentration in the medium. Identification of isolates shows different species of Actinobacteria with Streptomyces sp. playing the largest role, but also members of Bacilli, Alphaproteobacteria and Gammaproteobacteria. Sponges have an excellent record regarding production of bioactive compounds, often involving microbial symbionts. At the hydrothermal vents, however, the majority of active isolates originated from other invertebrates such as sea anemones or algae. The results indicate that antimicrobial assays involving isolates in full growth can detect activity not visible by other methods. The macro-organisms inhabiting the Eyjafjörður hydrothermal vent area host diverse microbial species in the phylum Actinobacteria with antimicrobial activity, and the compounds responsible for the activity will be subject to further research.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2023-12-12
    Description: Purpose: The consequential inventory modeling approach for life cycle assessment implies that an increase in the demand for a specific product is met by the marginal suppliers within the market. The identification of marginal suppliers is however complicated by difficulties in defining appropriate geographical market delimitations. In this study, an advanced system thinking approach is proposed to address this challenge in the identification of marginal supplying countries of wood products. Methods: Groups of countries which represent geographical markets are identified from trade data by using a network analysis-based clustering technique. Within these markets, marginal supplying countries are selected based on positive historical increments. The analysis covers 12 different products and all countries in the world using trade data for the period 1998–2013. Results and discussion: Global indices allow differentiating how product-specific trade networks are separated into communities and how interconnected these networks are. Large differences between products and minor differences between trade years are observed. Communities identified for each product tend to overlap with existing geographical regions and seem thus realistic. By combining this information with product-specific production increment rankings, marginal supplying countries of wood products were identified. Conclusions: The identified geographical market delimitation is a key for proper consequential life cycle assessment (LCA) inventory modeling in areas such as timber-based construction and biomass-based energy production. The method can in principle be applied to any product for which trade network data are available and ideally should be accompanied by a detailed analysis of technological constrains within the identified supplying country.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2023-11-08
    Description: The dynamics of the Loop Current (LC) in the Gulf of Mexico (GoM) during transient climates and interglacials, and its interaction with changes in sea level, atmospheric circulation, and Mississippi River (MR) discharge were studied. Geochemical proxy records and numerical modeling indicate that LC eddy shedding and its related heat transport into the GoM increased during the deglaciation. The model simulations imply decreased LC eddy shedding at lowered sea levels, while transports through Yucatan and Florida straits increased due to the southward migration of the Intertropical Convergence Zone (ITCZ) and increased wind-driven transport in the North Atlantic. Consistent with the model, (isotope) geochemical proxy records from the northern GoM show glacial/interglacial amplitudes significantly larger than in the Caribbean and extreme cooling during the Last Glacial Maximum (LGM) due to the vanishing LC eddy shedding. Prominent deglacial melt water releases observed south and west of the MR delta are neither present in the northeastern GoM, nor in sea-surface salinity-records in the subtropical North Atlantic. The freshwater signals were either a regionally restricted phenomenon or due to changes in the isotopic composition of the discharged water. Our results question the impact of MR megadischarges on the large-scale overturning circulation.
    Type: Book chapter , NonPeerReviewed
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  • 4
    Publication Date: 2023-11-08
    Description: The North Atlantic cold bias, associated with the misplacement of the North Atlantic Current (NAC) and typically extending from the surface to 1000 m depth, is a common problem in coupled models that compromises model fidelity. We investigate the use of a flow field correction (FFC) to adjust the path of the NAC and alleviate the cold bias. The FFC consists of three steps. First, climatological potential temperature (T) and salinity (S) fields for use with the model are produced using a three-dimensional restoring technique. Second, these T, S fields are used to modify the momentum equations of the ocean model. In the third stage, the correction term is diagnosed to construct a flow-independent correction. Results using the Kiel Climate Model show that the FFC allows the establishment of a northwest corner, substantially alleviating the subsurface cold bias. A cold bias remains at the surface but can be eliminated by additionally correcting the surface freshwater flux, without adjusting the surface heat flux seen by the ocean model. A model version in which only the surface fluxes of heat and freshwater are corrected continues to exhibit the incorrect path of the NAC and a strong subsurface bias. We also show that the bias in the atmospheric circulation is reduced in some corrected model versions. The FFC can be regarded as a way to correct for model error, e.g. associated with the deep water mass pathways and their impact on the large-scale ocean circulation, and unresolved processes such as eddy momentum flux convergence.
    Type: Article , PeerReviewed
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  • 5
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    Springer
    Publication Date: 2023-11-08
    Description: Definition: Seamounts are literally mountains rising from the seafloor. More specifically, they are “any geographically isolated topographic feature on the seafloor taller than 100 m, including ones whose summit regions may temporarily emerge above sea level, but not including features that are located on continental shelves or that are part of other major landmasses” (Staudigel et al., 2010). The term “guyot” can be used for seamounts having a truncated cone shape with a flat summit produced by erosion at sea level (Hess, 1946), development of carbonate reefs (e.g., Flood, 1999), or partial collapse due to caldera formation (e.g., Batiza et al., 1984). Seamounts 〈1,000 m tall are sometimes referred to as “knolls” (e.g., Hirano et al., 2008). “Petit spots” are a newly discovered subset of sea knolls confined to the bulge of subducting oceanic plates of oceanic plates seaward of deep-sea trenches (Hirano et al., 2006).
    Type: Book chapter , NonPeerReviewed
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  • 6
    Publication Date: 2023-11-08
    Description: Upper Apoyeque Tephra (UAq) was formed by a rhyodacitic plinian eruption in west-central Nicaragua at 12.4 ka BP. The fallout tephra was dispersed from a progressively rising plinian eruption column that became exposed to different wind speeds and directions at different heights in the stratosphere, leading to an asymmetric tephra fan with different facies in the western and southern sector. Tephra dispersal data integrated with geochemical compositions of lava flows in the area facilitate delimitation of the source vent to the south of Chiltepe Peninsula. UAq, Lower Apoyeque Tephra, Apoyeque Ignimbrite, and two lithic clasts in San Isidro Tephra together form a differentiation trend distinct from that of the younger tephras and lavas at Chiltepe Volcanic Complex in a TiO2 versus K2O diagram, compositionally precluding a genetic relationship of UAq with the present-day Apoyeque stratovolcano. Apoyeque Volcano in its present shape did not exist at the time of the UAq eruption. The surface expression of the UAq vent is now obscured by younger eruption products and lake water. Pressure-temperature constraints based on mineral-melt equilibria and fluid inclusions in plagioclase indicate at least two magma storage levels. Clinopyroxenes crystallised in a deep crustal reservoir at ~24 km depth as inferred from clinopyroxene-melt inclusion pairs. Chemical disequilibrium between clinopyroxenes and matrix glasses indicates rapid magma ascent to the shallower reservoir at ~5.4 km depth, where magnesiohornblendes and plagioclase fractionated at a temperature of ~830°C. Water concentrations were ~5.5 wt. % as derived from congruent results of amphibole and plagioclase-melt hygrometry. The eruption was triggered by injection of a hotter, more primitive melt into a water-supersaturated reservoir.
    Type: Article , PeerReviewed
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  • 7
    Publication Date: 2023-09-27
    Description: The Earth will exhibit continued global surface warming in response to a sustained increase of atmospheric carbon dioxide (CO2) levels. Massive meltwater input from the Antarctic ice sheet into the Southern Ocean could be one consequence of this warming. Here we investigate the impacts which this meltwater input may have on Earth’s surface climate and ocean circulation in a warming world. To this end a set of ensemble experiments has been conducted with a global climate model forced by increasing atmospheric CO2-concentration and an idealized Antarctic meltwater input to the Southern Ocean with varying amplitude and spatial pattern. As long as the atmospheric CO2-concentration stays moderate, i.e. below approximately twice the preindustrial concentration, and if a strong meltwater forcing of either 0.05 or 0.1 Sv is applied, enhanced Antarctic sea–ice cover and surface air temperature cooling over most parts of the Southern Ocean is observed. When the atmospheric CO2-concentration becomes larger than twice the preindustrial concentration, the meltwater only plays a minor role. The Antarctic meltwater drives significant slowing of the Southern Ocean meridional overturning circulation (MOC). Again, the meltwater influence only is detectable as long as the CO2-forcing is moderate. Much larger MOC changes develop in response to highly elevated atmospheric CO2-levels independent of whether or not a meltwater forcing is applied. The response of the Antarctic circumpolar current (ACC) is nonlinear. Substantial and persistent ACC slowing is simulated when solely the meltwater forcing of 0.1 Sv is applied, which is due to the halt of Weddell Sea deep convection and subsequent collapse of the Southern Ocean MOC. When the increasing atmospheric CO2-concentration additionally drives the model the ACC partly recovers in the long run. The partial recovery is due to strengthening westerly wind stress over the Southern Ocean, which intensifies the Ekman Cell. This study suggests that Southern Hemisphere climate projections for the twenty-first century could benefit from incorporating interactive Antarctic ice sheet.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2023-08-15
    Description: This book is an update of the first BACC assessment, published in 2008. It offers new and updated scientific findings in regional climate research for the Baltic Sea basin. These include climate changes since the last glaciation (approx. 12,000 years ago), changes in the recent past (the last 200 years), climate projections up until 2100 using state-of-the-art regional climate models and an assessment of climate-change impacts on terrestrial, freshwater and marine ecosystems. There are dedicated new chapters on sea-level rise, coastal erosion and impacts on urban areas. A new set of chapters deals with possible causes of regional climate change along with the global effects of increased greenhouse gas concentrations, namely atmospheric aerosols and land-cover change. The evidence collected and presented in this book shows that the regional climate has already started to change and this is expected to continue. Projections of potential future climates show that the region will probably become considerably warmer and wetter in some parts, but dryer in others. Terrestrial and aquatic ecosystems have already shown adjustments to increased temperatures and are expected to undergo further changes in the near future. The BACC II Author Team consists of 141 scientists from 12 countries, covering various disciplines related to climate research and related impacts. BACC II is a project of the Baltic Earth research network and contributes to the World Climate Research Programme.
    Type: Book , NonPeerReviewed
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  • 9
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    Springer
    In:  Strategies for Sustainability
    Publication Date: 2023-07-18
    Description: Here, expert authors delineate approaches that can support both decision makers as well as their concerned populations in overcoming unwarranted fears and in elaborating policies based on scientific evidence. Four exemplary focus areas were chosen for in-depth review, namely: - The scientific basis of risk management - Risk management in the area of environmental and ecological policy - Risk management in radiation medicine - Risk management in context with digitalization and robotics General as well as specific recommendations are summarized in a memorandum. Fundamental thoughts on the topic are presented in the introductory part of the book. The idea for and contents of the book were developed at a workshop on “Sustainable Risk Management: How to manage risks in a sensible and responsible manner?” held in Feldafing at Lake Starnberg (Germany) on April 14 to 16, 2016. The book offers important information and advice for scientists, entrepreneurs, administrators and politicians.
    Language: English
    Type: info:eu-repo/semantics/book
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  • 10
    Publication Date: 2023-07-18
    Description: Front Matter Pages I-XVII Einleitung Kathrin Stephen, Sebastian Knecht, Golo M. Bartsch Pages 1-18 Akteure innerhalb und außerhalb der Region Kathrin Stephen, Sebastian Knecht, Golo M. Bartsch Pages 19-43 Institutionen und Governance-Strukturen Kathrin Stephen, Sebastian Knecht, Golo M. Bartsch Pages 45-66 Wissenschaftliche Zugänge: Die Arktis im Fokus der Internationalen Beziehungen Kathrin Stephen, Sebastian Knecht, Golo M. Bartsch Pages 67-121 Empirische Beispiele Kathrin Stephen, Sebastian Knecht, Golo M. Bartsch Pages 123-170 Schlussbetrachtung Kathrin Stephen, Sebastian Knecht, Golo M. Bartsch Pages 171-173 Back Matter Pages 175-181
    Language: German
    Type: info:eu-repo/semantics/book
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