Seasonal Changes in Nitrogen, Free Amino Acids, and C/N Ratio in Mediterranean Seagrasses

Abstract. Seasonal changes in nitrogen, free amino acids, and carbon were investigated in the three Mediterranean seagrasses Posidonia oceanica, Cymodocea nodosa , and Zostera noltii. Leaves, rhizomes, roots, as well as dead plant material were analysed separately. Highest N-concentrations were obtained in the winter months, regardless of species or plant part. In contrast to the other two species, the N-content in Posidonia was higher in the rhizomes than in the leaves.
In the investigated species, marked differences in the free amino acid (FAA) composition were detected between species: Proline, lacking in Posidonia , was the main component in Cymodocea. In Posidonia , FAA decreased from 320umol g^-1 (dry wt) in leaf sheaths to 1.5 umol g^-1 (dry wt) in the leaf tips. The function of proline as a possible storage and/or stress metabolite is discussed.
High C/N values in dead P. oceanica and C. nodosa rhizomes as well as in P. oceanica wrack seem to be related to considerable resistance to decomposition. Low C/N ratios did not increase in detached C. nodosa and Z. noltii leaves, which began to decompose shortly after detachment from the plants.     

Pyrolysis-high resolution gas chromatography and pyrolysis gas chromatography-mass spectrometry of kerogens and kerogen precursors

A series of kerogens and kerogen precursors isolated from DSDP samples, oil shales and Recent algal mats have been examined by Curie point pyrolysis-high resolution gas chromatography and gas chromatography-mass spectrometry. This study has shown that the three main types of kerogens (marine, terrestrial and mixtures of both) can be characterized using these techniques. The marine (algal) kerogens yield principally aliphatic products and the terrestrial kerogens yield more aromatic and phenolic products with some n-alkanes and n-alkenes. The yields of n-alkanes and n-alkenes increase and phenols decrease with increasing geologic age, however, pyrolysis-GC cannot be used to characterize the influence of short term diagenesis on the kerogen structure.     

Towards high‐resolution 3D marine seismic surveying using Boomer sources

The use of Boomer sources for 3D seismic imaging of shallow marine structures was investigated in a feasibility study. Boomers show sufficient stability to be used in multichannel seismic surveys. The acquisition of a high-frequency, densely sampled seismic data volume was successfully performed in the Baltic Sea. A Pleistocene fluvial channel system and shallow gas accumulations were revealed beneath the unconsolidated sediments which constitute the sea-floor in the southern Kiel Bay.     

Realization of X-ray telescopes–from design to performance

For more than 45 years the building of X-ray telescopes for solar and astronomical observations has been practised with significant performance improvement. The various techniques applied are reviewed emphazising the impact of proper mirror material choice, grinding and polishing improvements and the role of metrology.     

A high‐resolution relative time scale for the Viséan Stage (Carboniferous) of the Kulm Basin (Rhenish Mountains,Germany)

The Viséan (Carboniferous) sedimentary succession of the basinal Kulm facies (Rhenish Mountains) was investigated in detail in order to achieve a high‐resolution stratigraphic subdivision and correlation. Additionally, the ranges of fossil index taxa (ammonoids), fossil marker beds, volcaniclastic horizons and sedimentary features (e.g. colour changes) were integrated in the correlation. As a result, a comprehensive database was compiled, which contains 190 stratigraphic events of the Viséan interval of this area. Several sections are almost completely composed of shales, which are regarded to represent a slow but constant basinal background sedimentation of the Kulm facies. The thickness of lithological homogeneous sections thus indicates an approximately linear record of time and the average thicknesses of biozones and positions of stratigraphic events can easily be calculated from the compiled database. The result is an approximately time‐linear biostratigraphic scale for the Viséan Stage of the Kulm Basin. Given a numerical length of the Viséan Stage of ca. 19 Ma, 190 stratigraphic events give a mean resolution of 100 000 years. This is unique in Palaeozoic stratigraphy. Copyright © 2008 John Wiley & Sons, Ltd.     

Diterpenoid compounds and other lipids in deep-sea sediments and their geochemical significance

Cyclic diterpenoid compounds have been found by various investigators in the geosphere (e.g. fossil resins, coals, soil, shale and deep-sea sediments). These compounds occur in significant amounts only in higher plants and are therefore potential markers of terrigenous plant lipids.Diterpenoids with the abietane skeleton (mainly dehydroabietic acid) have been identified in the lipids of sediment samples from the northeast Pacific Ocean, Black Sea and North Atlantic Ocean. The presence of these resin-derived compounds correlated with the terrigenous clay components and with the presence of pollen. The presence of polycyclic diterpenoids was also correlated with the distribution patterns and inferred sources of other sediment lipid constituents (e.g. n-alkanes, n-fatty acids, etc.).Potamic transport, followed by turbidite redistribution are the probable input mechanisms of these resin-derived compounds to the deep-sea sediments. These diterpenoids appear to be excellent biological markers of resinous higher plants.     

Interactive Visualization to Advance Earthquake Simulation

The geological sciences are challenged to manage and interpret increasing volumes of data as observations and simulations increase in size and complexity. For example, simulations of earthquake-related processes typically generate complex, time-varying data sets in two or more dimensions. To facilitate interpretation and analysis of these data sets, evaluate the underlying models, and to drive future calculations, we have developed methods of interactive visualization with a special focus on using immersive virtual reality (VR) environments to interact with models of Earth’s surface and interior. Virtual mapping tools allow virtual “field studies” in inaccessible regions. Interactive tools allow us to manipulate shapes in order to construct models of geological features for geodynamic models, while feature extraction tools support quantitative measurement of structures that emerge from numerical simulation or field observations, thereby enabling us to improve our interpretation of the dynamical processes that drive earthquakes. VR has traditionally been used primarily as a presentation tool, albeit with active navigation through data. Reaping the full intellectual benefits of immersive VR as a tool for scientific analysis requires building on the method’s strengths, that is, using both 3D perception and interaction with observed or simulated data. This approach also takes advantage of the specialized skills of geological scientists who are trained to interpret, the often limited, geological and geophysical data available from field observations.