The role of biophysical interactions within the ijzermonding tidal flat sediment dynamics

This paper focuses on the importance of biophysical interactions on short-term and long-term sediment dynamics. Therefore, various biological (macrobenthos, photopigments, colloidal EPS) and physical parameters (grain size, water content, sediment stability, bed level) were determined (bi)monthly in nine sampling plots on the IJzermonding tidal flat (Belgium, 51°08′N, 2°44′E) during three consecutive years (July 2005–June 2008). Results showed that sediment stability varied on the short timescale and was directly influenced by biota, while bed level varied mainly on the long-term due to interannual variability. The short-term dynamic relationships between mud content, water content, fucoxanthin and macrobenthos density resulted in a seasonal mud deposition and erosion cycle, and directly influenced sediment stability. Moreover, macrobenthos was proven to be the most important parameter determining sediment stability. On the long-term, a shift was observed from high fucoxanthin/chla concentration, high mud content and zero to moderate densities of Corophium volutator towards low fucoxanthin/chl a and mud content and high Corophium densities, which resulted in a transition from net accretion to net erosion. However, most measured variables proved to be poor predictors for these long-term bed level changes, indicating that external physical forces, such as waves and storminess, probably were the most important factors triggering long-term sediment dynamics. Nevertheless, biota indirectly influenced bed level changes by mediating short-term changes in sediment stability, thereby influencing the erodability of the sediment. The macrobenthos, and especially the mud shrimp Corophium, was suggested as the (indirect) driving destabilising factor for the sampling plots in the IIzermonding when considering the long-term evolution.     

Sulphide ooids from the proterozoic Siyeh Formation of Alberta,Canada

Sulphide ooids from 0.5 to 4 mm in diameter occur over a large area in a thin arenite bed near the base of the Proterozoic Siyeh Formation in southwestern Alberta. Examination by optical microscope, scanning electron microscope, and electron microprobe, reveals that the ooids are composed of concentric layers, a few micrometers to a few tens of micrometers thick, of pyrite and chalcopyrite. Covellite is also present in several ooids. Copper sulphides are more abundant towards the centre of the ooids than in the outer shells where pyrite is predominant. A slightly eccentric nucleus of chalcopyrite and/or titanium oxide occurs in several ooids. It is speculated that the ooids grew during early diagenesis of the arenite, and that the source of metals were black argillaceous sediments above and below the arenite. The nucleation of sulphides around detrital grains of chalcopyrite and titanium oxide has an important bearing on metallogenetic models of stratiform copper deposits.     

Alter-geopolitics: Other securities are happening

In an age of increasing state (in)security, some are coming together on their own to build alternative nonviolent securities. They are making connections across distance and difference which focus on the safety of bodies (often by actually moving bodies), and ground geopolitics in everyday life. The term anti-geopolitics focuses on resistance to hegemonic geopolitics (material or discursive), rather than this sort of effort to build something new. Feminist geopolitics is a form of anti-geopolitics that not only takes apart but also puts the pieces together in new ways - with broader definitions of security for more bodies in more places. Yet it has not generally looked at that practice as engaged in outside of academia. I propose the term alter-geopolitics for a type of feminist geopolitics as a way to extend both the concepts of anti- and feminist geopolitics. I argue for the term as a reminder to look to grassroots practice, to the ways that groups are doing geopolitics in the streets, in homes, in jungles, and in many other spaces ‘off the page’. Though they may not think of their work as geopolitics, framing it in this way can open fruitful conversations. As academics we have much to learn and offer through collaboratively thinking with such groups about security. I have been doing this with international accompaniers in Colombia and discuss their work, and the peace community of San José that they accompany, as forms of alter-geopolitics.     

A search for shocked quartz grains in the Allerød‐Younger Dryas boundary layer

The Younger Dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the Allerød interstadial resulted in the Younger Dryas cold period. So far, no reproducible, diagnostic evidence has, however, been reported. Quartz grains containing planar deformation features (known as shocked quartz grains), are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting. Although alleged shocked quartz grains have been reported at a possible Allerød‐Younger Dryas boundary layer in Venezuela, the identification of shocked quartz in this layer is ambiguous. To test whether shocked quartz is indeed present in the proposed impact layer, we investigated the quartz fraction of multiple Allerød‐Younger Dryas boundary layers from Europe and North America, where proposed impact markers have been reported. Grains were analyzed using a combination of light and electron microscopy techniques. All samples contained a variable amount of quartz grains with (sub)planar microstructures, often tectonic deformation lamellae. A total of one quartz grain containing planar deformation features was found in our samples. This shocked quartz grain comes from the Usselo palaeosol at Geldrop Aalsterhut, the Netherlands. Scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging, however, show that the planar deformation features in this grain are healed and thus likely to be older than the Allerød‐Younger Dryas boundary. We suggest that this grain was possibly eroded from an older crater or distal ejecta layer and later redeposited in the European sandbelt. The single shocked quartz grain at this moment thus cannot be used to support the Younger Dryas impact hypothesis.     

The influence of changes in tidal asymmetry on residual sediment transport in the Western Scheldt

This study fits into a wider research program from RWS RIKZ concerning the exchange of sediment between the coast and the tidal basins, Western Scheldt and Wadden Sea, which are the largest basins along the Dutch Coast, over different time-scales. For both basins, questions about the evolution of the import/export at the mouth recently arose. In case of the Western Scheldt, which is the subject of this study, mainly the uncertainty about the future developments after the change from import to export at the mouth was noticed in the 1990s, which necessitated a more detailed study of this area.     

Ecology and fluvial dynamics of an Early Holocene medium‐sized European lowland river valley (Upper Scheldt,northern Belgium)

The fluvial environment of Early Holocene small‐ to middle‐sized lowland rivers in northwest Europe is mostly unstudied due to a lack of preserved and accessible deposits. A rescue excavation in the Scheldt valley in northern Belgium offered the opportunity to study a Boreal alluvial succession in detail. The results of palaeoecological and sedimentological analyses (diatoms, pollen, botanical macro‐remains, molluscs, grain size) characterize the biotic and physical environment in the middle reach of this medium‐sized river system. Although the Early Holocene in the Scheldt Basin has often been portrayed as a period of fluvial stability with marshy conditions and diffuse discharge, this study showed evidence of point bar formation by a small, low‐energy meandering river between ~9.5 and ~8.8 cal. ka BP. The point bar was at least temporarily vegetated and shows a shift from herbaceous riparian vegetation to an open willow‐dominated alluvial forest. This evidence points to a more open vegetation and a more energetic environment than traditionally described for rivers of this size and age. A link to the 9.3 ka BP cooling event is suggested and possible reasons for the scarcity of records of this type of deposits are discussed.     

Topographical distribution of lipids inside the mandibular fat bodies of odontocetes: remarkable complexity and consistency

Odontocetes possess unusual and specialized mandibular fat bodies in and around their lower jaws. These tissues have been proposed to facilitate sound reception and are composed of unusual endogenously synthesized lipids. Little is known about how the topographical arrangement of the lipid molecules in these tissues influences sound reception. We examined the lipid composition of the mandibular fat bodies, using a fine-scale approach, on six specimens (representing four odontocete families). We show that odontocete jaw lipids exhibit a complex structural three-dimensional topography. Different odontocetes synthesize and deposit slightly different molecules, but the relative arrangement of the lipids within each head showed marked consistency. Mandibular fats of beaked whales were uniquely dominated by isolauric acid (i-12:0). In contrast, the dolphin and porpoise biosynthesized isovaleric acid (i-5:0), while the pygmy sperm whale deposited medium-length (10-14 carbons) straight-chain lipids. In all heads examined, the shortest and branched-chain ("i") fatty acids were concentrated in the center of the jaw fats, which connect intimately with the ears. We hypothesize that in odontocete jaws, this arrangement may serve to channel an incoming sound to the ears because sound travels slower through shorter branched-chain fatty acids than through longer straight-chain fatty acids.     

Information systems playground—the target infrastructure

The Target infrastructure has been specially built as a storage and compute infrastructure for the information systems derived from Astro-WISE. This infrastructure will be used by several applications that collaborate in the area of information systems within the Target project. It currently consists of 10 PB of storage and thousands of computational cores. The infrastructure has been constructed based on the requirements of the applications. The storage is controlled by the Global Parallel File System of IBM. This file system takes care of the required flexibility by combining storage hardware with different characteristics into a single file system. It is also very scalable, which allows the system to be extended into the future, while replacing old hardware with new technology.     

Links between bacterial communities in marine sediments and trace metal geochemistry as measured by in situ DET/DGT approaches

Our current view about the relationship between metals and bacteria in marine sediments might be biased because most studies only use ex situ approaches to quantify metals. The aim of the present research was to compare ex situ and in situ methods of metal measurement (DET and DGT--diffusive equilibration or diffusive gradients in thin-films) and relate the results with two commonly used microbiological variables (bacterial biomass and bacterial diversity as revealed by DGGE). No previous studies have used such in situ approaches in microbial ecology. For biomass and most of the investigated trace metals (Ag, Cd, Sn, Cr, Ni, Cu, Pb, and Al) no significant correlations were found. The exceptions were Fe, Mn, Co, and As which behave like micronutrients. For bacterial diversity, no relevant relationships were found. We conclude that in situ methods are more adapted tools for microbial ecologists but that ex situ approaches are still necessary.