Benthic community productivity in the Magellan region and in the Weddell Sea

Our comparison of macrobenthic biomass, production and productivity of the Magellan region (14 - 349 m water depth) and the Weddell Sea (132 - 548 m water depth) is based on multi box corer samples collected in both areas. Biomass is slightly but not significantly lower in the Magellan region (7.3 g C m-2) than in the Weddell Sea (12.0 g C m-2). Annual production and P/B ratio are higher in the Magellan region (5.1 g C m-2 y-1, 0.7 y-1) as compared to the Weddell Sea (3.6 g C m-2 y-1, 0.3 y-1). In the Magellan region, Mollusca, Polychaeta and Arthropoda dominate benthic production, whereas in the Weddell Sea Polychaeta, Porifera and Echinodermata are the most productive taxa

Dual citizenship as a path-dependent process

Faist T, Gerdes J, Rieple B. Dual citizenship as a path-dependent process. COMCAD Arbeitspapiere - working papers, 7. Bielefeld: COMCAD - Center on Migration, Citizenship and Development; 2004

Eine Analyse von Positionspapieren und Entwicklungsperspektiven

Die Bedeutung von Open Science für wissenschaftliche Bibliotheken steht im Mittelpunkt dieser Untersuchung. Sie geht zunächst den Aussagen zum Thema Open Science in für wissenschaftliche Bibliotheken relevanten Positionspapieren nach. Daraufhin wird anhand ausgewählter Fallbeispiele dargestellt, inwieweit die wissenschaftlichen Bibliotheken in Deutschland und der EU bereits im Bereich Open Science aktiv sind. Schließlich ist es Ziel dieser Untersuchung, Möglichkeiten für die weitere Entwicklung von Open Science in wissenschaftlichen Bibliotheken aufzuzeigen

Mechanisms of fast-ice development in the south-eastern Laptev Sea: a case study for winter of 2007/08 and 2009/10

Accurate representation of fast ice in numerical models is important for realistic simulation of numerous sea-ice and ocean variables. In order to simulate seasonal and interannual variability of fast-ice extent, the mechanisms controlling fast-ice development need to be thoroughly understood. The objective of this paper is to investigate mechanisms contributing to the advance of fast-ice edge to its winter location in the south-eastern Laptev Sea. The study is based on time series of synthetic aperture radar (SAR) imagery for winter 2007/08 and 2009/10. A detailed examination of SAR-based ice drift showed that several grounded ice features are formed offshore prior to fast-ice expansion. These features play a key role in offshore advance of the fast-ice edge and serve as stabilizing points for surrounding pack ice as it becomes landfast. Electromagnetic ice thickness measurements suggest that the grounded ice ridges over water depths of ca. 20 m water might be responsible for interannual variations in fast-ice edge position. Contrary to previous studies, we conclude that grounding is a key mechanism of fast-ice development in the south-eastern Laptev Sea

A glimpse beneath Antarctic sea ice: observation of platelet-layer thickness and ice-volume fraction with multi-frequency EM

In Antarctica, ice crystals (platelets) form and grow in supercooled waters below ice shelves. These platelets rise, accumulate beneath nearby sea ice, and subsequently form a several meter thick, porous sub-ice platelet layer. This special ice type is a unique habitat, influences sea-ice mass and energy balance, and its volume can be interpreted as an indicator of the health of an ice shelf. Although progress has been made in determining and understanding its spatio-temporal variability based on point measurements, an investigation of this phenomenon on a larger scale remains a challenge due to logistical constraints and a lack of suitable methodology. In the present study, we applied a lateral constrained Marquardt-Levenberg inversion to a unique multi-frequency electromagnetic (EM) induction sounding dataset obtained on the ice-shelf influenced fast-ice regime of Atka Bay, eastern Weddell Sea. We adapted the inversion algorithm to incorporate a sensor specific signal bias, and confirmed the reliability of the algorithm by performing a sensitivity study using synthetic data. We inverted the field data for sea-ice and platelet-layer thickness and electrical conductivity, and calculated ice-volume fractions within the platelet layer using Archie’s Law. The thickness results agreed well with drillhole validation datasets within the uncertainty range, and the ice-volume fraction yielded results comparable to other studies. Both parameters together enable an estimation of the total ice volume within the platelet layer, which was found to be comparable to the volume of landfast sea ice in this region, and corresponded to more than a quarter of the annual basal melt volume of the nearby Ekström Ice Shelf. Our findings show that multi-frequency EM induction sounding is a suitable approach to efficiently map sea-ice and platelet-layer properties, with important implications for research into ocean/ice-shelf/sea-ice interactions. However, a successful application of this technique requires a break with traditional EM sensor calibration strategies due to the need of absolute calibration with respect to a physical forward model

Growth and age of the Antarctic bryozonan Cellaria incula on the Weddell Sea shelf

*tbrey~a~~z-bremerhaven de Abstract: We analysed growth of the arborescent Antarctic cheilostoine bryozoan Cellaria incula by stable carbon and oxygen isotope analysis. The growth of one complete branch of C. incula takes one year, i.e. owing to the bifurcate colony structure two new branches grow froin each branch of the previous generation, The maximum age of a C. incula colony is likely to be more than 14 years. Annual production-to-biomass ratio is 0.67, the highest value hitherto measured for any benthic invertebrate south of 62"s. Comparatively fast growth and high productivity identi @ C. zncula as a pioneer species which is able to quickly occupy spatial niches produced by iceberg scouring on the Antarctic shelf

The bimodality of the East Siberian fast ice extent: mechanisms and changes

Using operational sea-ice maps, we provide first insight into the seasonal evolution of fast ice in the East Siberian Sea for the period between 1999 and 2021. The fast ice season tends to start later by 4.7 d per decade and to end earlier by 9.7 d per decade. As a result, there is a trend towards a shorter length of fast ice season by 2 weeks per decade. The analysis of air temperatures indicates that onset and end of the fast ice season are largely driven by thermodynamic processes. Two spatial modes (large, L-mode and small, S-mode) of East Siberian fast ice cover which have significant areal differences were distinguished. The occurrence of L- and S-modes was linked to the polarity of the Arctic Oscillation (AO) index. Negative AO phase leads to increased sea-ice convergence in the region, which in turn favours sea-ice grounding and promotes the development of large fast ice extent (L-mode). Lower deformation rates in the region during positive AO phase does not allow the formation of grounded features which results in small fast ice extent (S-mode). An analysis of sea-ice divergence confirms that L-mode seasons are characterised by higher on-shore convergence compared with S-mode seasons

Hans Steffen (1865-1936): Grenzerfahrungen eines deutschen Geografen in Chile

Der Nachlass des deutschen Geografen Hans Steffen (1865–1936) ist heute in der Bibliothek des Ibero-Amerikanischen Instituts (IAI) in Berlin archiviert. 2013 wurde er dort im Rahmen eines vom Beauftragten der Bundesregierung für Kultur und Medien geförderten Projekts inhaltlich und formal erschlossen. Große Teile des Nachlasses wurden der Forschung zudem als Digitalisate in den Digitalen Sammlungen des IAI online zugänglich gemacht. Die vorliegende Biobibliografie möchte interessierten Wissenschaftlerinnen und Wissenschaftlern einen ersten Einblick in Leben und Werk Hans Steffens anbieten sowie Orientierungspunkte für weitere Forschungen aufzeigen. Dazu erfolgt zunächst eine Übersicht über die wichtigsten Lebensdaten Steffens. Ergänzt wird die Biografie durch einige Anmerkungen zum Weg seines Nachlasses in das IAI. In dem Nachlass findet sich sehr umfangreiches Material zu Steffens Patagonien-Expeditionen, die er im Kontext des chilenisch-argentinischen Grenzstreites am Ende des 19. Jahrhunderts unternahm. Daher erscheint es interessant, auf diesen Teil seiner Forschungstätigkeit näher einzugehen. Abschließend dient der Plagiatsvorwurf Hans Steffens gegen Paul Krüger als aufschlussreiches Beispiel für die Zusammenarbeit, aber auch für die Konkurrenz der zeitgenössischen Wissenschaftler.Ibero-Bibliographien, Vol. 1

Genomic and experimental evidence for multiple metabolic functions in the RidA/YjgF/YER057c/UK114 (Rid) protein family.

BackgroundIt is now recognized that enzymatic or chemical side-reactions can convert normal metabolites to useless or toxic ones and that a suite of enzymes exists to mitigate such metabolite damage. Examples are the reactive imine/enamine intermediates produced by threonine dehydratase, which damage the pyridoxal 5'-phosphate cofactor of various enzymes causing inactivation. This damage is pre-empted by RidA proteins, which hydrolyze the imines before they do harm. RidA proteins belong to the YjgF/YER057c/UK114 family (here renamed the Rid family). Most other members of this diverse and ubiquitous family lack defined functions.ResultsPhylogenetic analysis divided the Rid family into a widely distributed, apparently archetypal RidA subfamily and seven other subfamilies (Rid1 to Rid7) that are largely confined to bacteria and often co-occur in the same organism with RidA and each other. The Rid1 to Rid3 subfamilies, but not the Rid4 to Rid7 subfamilies, have a conserved arginine residue that, in RidA proteins, is essential for imine-hydrolyzing activity. Analysis of the chromosomal context of bacterial RidA genes revealed clustering with genes for threonine dehydratase and other pyridoxal 5'-phosphate-dependent enzymes, which fits with the known RidA imine hydrolase activity. Clustering was also evident between Rid family genes and genes specifying FAD-dependent amine oxidases or enzymes of carbamoyl phosphate metabolism. Biochemical assays showed that Salmonella enterica RidA and Rid2, but not Rid7, can hydrolyze imines generated by amino acid oxidase. Genetic tests indicated that carbamoyl phosphate overproduction is toxic to S. enterica cells lacking RidA, and metabolomic profiling of Rid knockout strains showed ten-fold accumulation of the carbamoyl phosphate-related metabolite dihydroorotate.ConclusionsLike the archetypal RidA subfamily, the Rid2, and probably the Rid1 and Rid3 subfamilies, have imine-hydrolyzing activity and can pre-empt damage from imines formed by amine oxidases as well as by pyridoxal 5'-phosphate enzymes. The RidA subfamily has an additional damage pre-emption role in carbamoyl phosphate metabolism that has yet to be biochemically defined. Finally, the Rid4 to Rid7 subfamilies appear not to hydrolyze imines and thus remain mysterious