15 research outputs found
Unusual distributions of long-chain alkenones and tetrahymanol from the highly alkaline Lake Van, Turkey
No full textLong-chain C37 to C40 alkenones with di-, tri-, and tetra-unsaturation are very abundant in sediment trap material and Holocene to Late Pleistocene core samples from the Earth's largest soda lake, Lake Van (Turkey). Thus, the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments. The observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra-unsaturated compounds, especially the C37:4 methyl ketone. Their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation. Using published U37K calibrations, no reliable absolute temperatures were obtained for the Lake Van samples. Accordingly, marine sea surface temperature determinations based on long-chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded. The presence of tetrahymanol and gammacer-3-one in the Lake Van materials is attributed to organic matter contributions of ciliates. The relative abundance of long-chain alkenones and of tetrahymanol/gammacer-3-one is considered to reflect changes in the environmental conditions, in particular in the hydrological setting. We suggest that times of pronounced stagnation are recognised by very high tetrahymanol/gammacer-3-one concentrations together with drastically increased stanol/stenol ratios, and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions
Microbial carbonate crusts - a key to the environmental analysis of fossil spongiolites?
No full textresearc
Mid-chain branched alkanoic acids from "living fossil" demosponges: a link to ancient sedimentary lipids?
No full textThe lipid assemblages of the "living fossil" stromatoporoid Astrosclera willeyana (Great Barrier Reet) and the demosponge Agelas aroides (Mediterranean Sea) were investigated. Large amounts of branched carboxylic acids are present in the sponges studied. These compounds include terminally branched carboxylic acids (isa -/anteisa-) and abundant mid-chain branched carboxylic acids (MBCA) wh ich are characterized by an intriguing variety of structural isomers present in the C 15- C25 range. The most prominent MBCA are comprised of isomeric methylhexadecanoic acids and methyloctadecanoic acids. A second cluster of MBCA includes methyldocosanoic acids and methyltetracosanoic acids, but other homologues are also present. Methyl branching points were generally observed between the w5- and w9-positions. These complex isomeric mixtures apparently derive from symbiotic bacteria living exclusively in demosponges. Comparison with hydrocarbon compositions of ancient carbonates reveals evidence that the MBCA found are potential lipid precursors of mid-chain branched monomethylalkanes often observed in fossil sediments and oils. As a working hypo thesis, we suggest that their bacterial source organisms have been widespread in the geological past, and are found " inherited" in the protective environment of distinctive sponge hosts in recent marine ecosystems. Furthermore, both sponges contain abundant linear, longchain C24- C26 dienoic "demospongic" acids. The demospongic acid distribution and the presence of phytanic acid in A. willeyana match the patterns found in A. aroides and other members of the Agelasida. These findings confirm the systematic position of A. willeyana within this demosponge taxon
Mid-chain branched alkanoic acids from "living fossil" demosponges: a link to ancient sedimentary lipids?
No full textThe lipid assemblages of the "living fossil" stromatoporoid Astrosclera willeyana (Great Barrier Reet) and the demosponge Agelas aroides (Mediterranean Sea) were investigated. Large amounts of branched carboxylic acids are present in the sponges studied. These compounds include terminally branched carboxylic acids (isa -/anteisa-) and abundant mid-chain branched carboxylic acids (MBCA) wh ich are characterized by an intriguing variety of structural isomers present in the C 15- C25 range. The most prominent MBCA are comprised of isomeric methylhexadecanoic acids and methyloctadecanoic acids. A second cluster of MBCA includes methyldocosanoic acids and methyltetracosanoic acids, but other homologues are also present. Methyl branching points were generally observed between the w5- and w9-positions. These complex isomeric mixtures apparently derive from symbiotic bacteria living exclusively in demosponges. Comparison with hydrocarbon compositions of ancient carbonates reveals evidence that the MBCA found are potential lipid precursors of mid-chain branched monomethylalkanes often observed in fossil sediments and oils. As a working hypo thesis, we suggest that their bacterial source organisms have been widespread in the geological past, and are found " inherited" in the protective environment of distinctive sponge hosts in recent marine ecosystems. Furthermore, both sponges contain abundant linear, longchain C24- C26 dienoic "demospongic" acids. The demospongic acid distribution and the presence of phytanic acid in A. willeyana match the patterns found in A. aroides and other members of the Agelasida. These findings confirm the systematic position of A. willeyana within this demosponge taxon
Bridging the Gap for Seabed Mining: Preparatory Instruments for the New Law of the Sea Convention
No full textThis Article discusses the need for, and structure of, a temporary preparatory commission to begin work on the International Seabed Authority once the Draft Treaty on the Law of the Sea has been ratified. Acknowledging that the Authority will require a preparatory commission to pay the way for their early stages, the author examines the possible permutations of such an authority and concludes that the debate over the structuring of the Preparatory Commission will be another obstacle to convention ratification
Staking the Self. Transitions from truth-books to experience-books in Mariella Mehr- prose
No full textMichel Foucaults Überlegungen zu Wahrheits- und Erfahrungsbüchern zugrunde legend, untersucht die Promotionsschrift Wechselwirkungen von Fremd- und Selbstrepräsentation, von Repräsentation und Subjektkonstitution und fragt ausgehend von diesen Zusammenhängen nach einer möglichen Poetik entsubjektivierender Erfahrungsbücher. Exemplarisch nachgezeichnet werden die oft paradoxalen Effekte dieser Wechselwirkungen zunächst anhand des kriminalisierenden und pathologisierenden Diskurses über Jenische und der daran anknüpfenden Ausarbeitung jenischer Subjektpositionen im Zuge der politischen Selbstrepräsentation der Schweizer Minderheit seit den 1970er Jahren. Die in diesem Kontext entstandenen literarisch-publizistischen Texte der Schweizer Autorin und ehemaligen jenischen Bürgerrechtlerin Mariella Mehr, in denen sich ebenfalls normalisierende, am Wahrheitsdiskurs orientierte Ausarbeitungen jenischer Subjektpositionen finden, werden als Wahrheitsbücher im Sinne Foucaults gelesen. An Mehrs späten Texten wird daran anschließend gezeigt, wie mittels einer Hyperbolisierung des Wahrheitsdiskurses in Kombination mit sich durchkreuzenden auto- und heteroreferentiellen Erzählverfahren der von Foucault im Interview mit Ducio Trombadori beschriebene entsubjektivierende Effekt eines Erfahrungsbuches erreicht werden kann.Based on Michel Foucault- concept of "truth"- versus "experience"-books, the thesis explores the interdependence of subaltern self-representation/hegemonic representation as well as of representation/subjectivation (assujettissement) and, taking these interconnections as a vantage point, outlines a possible poetics of desubjectivating experience-books. To exemplify the paradoxical effects inherent in the interdependence of hegemonic representation and subaltern self-representation/subjectivation, the thesis first traces the process of discursive pathologizing of the allegedly innate nomadic lifestyle and criminal disposition of the "Jenisch" minority in Switzerland in the late 19th and much throughout the 20th century. (Political) Jenisch self-representation from the 1970s onwards drew largely on these discursive hegemonic "truths", albeit in an effort to at least partly disprove them by creating normalised Jenisch subject positions and thus alternative "truths". A similar effort to create normalised Jenisch subject positions can also be found in early literary and journalistic texts of Swiss-born author and former member of the Jenisch civil rights movement, Mariella Mehr " texts which are therefore read and classified as "truth"-books. The thesis finally goes on to show that Mehr- recent texts, however, hyperbolize the aforementioned discursive hegemonic "truths", which in combination with an intricate use of heteroreferential and autoreferential narrative techniques (such as metanarrative/metafiction) allows them to function as "experience"-books as described by Foucault in an interview with Ducio Trombadori
Hydrothermal petroleum generation in Red Sea sediments from the Kebrit and Shaban deeps
No full textPetroleum impregnated sediments and massive sulfides have been found in two deeps of the northerns Red Sea. Biological marker distributions in extracts and polar fraction degradation products were analyzed in order to elucidate the source of the petroliferous material. Two organic phases could be distinguished according to their source and maturity.
The amounts of n-alkanes show a marked decrease with depth, whereas the concentrations of various branched and cyclic hydrocarbons increase, resulting in a humpof unresolvable compounds in a depth as shallow as 300 cm. Changes in concentrations and distributions of hopanoids in the Kebrit Deep sediments indicate a rapid increase of maturity with depth. The deepest core section (300 cm) and the masive sulfide reveal comparable maturation indices typical for mature oils.
By chemical degradation of the polar fractions a series of C40-isoprenoids was obtained, which reveals a considerable contribution from methanogenic and thermophilic archapbacteria to the immature organic matter. The data suggest that petroliferous material ofthermogenic origin migrates through the younger sequences, superimposes the autochthonous organic substances in the sediments and furthermore, forms asphaltic impregnations in the massive sulfides
Coastal and sea space development
No full textThe group proceeded in selecting a range of existing, planned or proposed projects relevant to its goal and representative for the state-of-the-art. So far 4 projects related to the coastline and 1 project in the coastal shelf have been selected. Furthermore the field of offshore renewable energy has been outlined; in addition a possible supporting project on earth observation, one which could provide important feedback of data on the quality of the environment and the morphology o f the coastline, is included. These projects are considered to be representative for the variety of challenges, techniques and theoretical insights necessary : they should form a valid basis for defining innovation needs and development trends
