Bacterial community composition and extracellular enzyme activity in temperate streambed sediment during drying and rewetting

Droughts are among the most important disturbance events for stream ecosystems; they not only affect stream hydrology but also the stream biota. Although desiccation of streams is common in Mediterranean regions, phases of dryness in headwaters have been observed more often and for longer periods in extended temperate regions, including Central Europe, reflecting global climate change and enhanced water withdrawal. The effects of desiccation and rewetting on the bacterial community composition and extracellular enzyme activity, a key process in the carbon flow of streams and rivers, were investigated in a typical Central European stream, the Breitenbach (Hesse, Germany). Wet streambed sediment is an important habitat in streams. It was sampled and exposed in the laboratory to different drying scenarios (fast, intermediate, slow) for 13 weeks, followed by rewetting of the sediment from the fast drying scenario via a sediment core perfusion technique for 2 weeks. Bacterial community structure was analyzed using CARD-FISH and TGGE, and extracellular enzyme activity was assessed using fluorogenic model substrates. During desiccation the bacterial community composition shifted toward composition in soil, exhibiting increasing proportions of Actinobacteria and Alphaproteobacteria and decreasing proportions of Bacteroidetes and Betaproteobacteria. Simultaneously the activities of extracellular enzymes decreased, most pronounced with aminopeptidases and less pronounced with enzymes involved in the degradation of polymeric carbohydrates. After rewetting, the general ecosystem functioning, with respect to extracellular enzyme activity, recovered after 10 to 14 days. However, the bacterial community composition had not yet achieved its original composition as in unaffected sediments within this time. Thus, whether the bacterial community eventually recovers completely after these events remains unknown. Perhaps this community undergoes permanent changes, especially after harsh desiccation, followed by loss of the specialized functions of specific groups of bacteria

Conclusion: Half-hearted Multilaterisation of a Unilateral Doctrine

This concluding chapter draws the central threads of the book together. It proceeds in five steps, providing conclusions, first, on the limitation of military intervention by invitation and, second, on the institutionalisation triggered by the increased importance of the UN Security Council in the operation of the law. It then takes up the question of whether Council practice may contribute to the development of the law, and it addresses the politicisation of the practice of consensual military intervention. Finally, it argues that while practice has been multilateralised as a result of the increased role the Security Council plays, we are in fact witness only to a ‘half-hearted multilateralisation’

Low flow controls on benthic and hyporheic macroinvertebrate assemblages during supra-seasonal drought

Despite the widely accepted importance of the hyporheic zone as a habitat for stream macroinvertebrates during floods, few data exist regarding community composition and distribution during periods of low flow or drought in perennial streamsi Integrating research on hyporheic invertebrates with results from a long-term study of a U K river provided the opportunity to examine how surface and hyporheic macroinvertebrate communities respond to inter-annual variability in river flow and periods of groundwater drought. Changes in the riverine macroinvertebrate community associated with low flow included a reduction in species richness and the number of individuals per sample, particularly aquatic insects. The hyporheic community was characterized by a relatively homogeneous composition during a period of severe low flow, punctuated by short-term changes associated with variation in water temperature rather than changes in discharge. We present a conceptual model of the processes influencing benthic and hyporheic invertebrates under low-flow conditions. Previous studies have seldom integrated these two assemblages and their interactions. The model presented highlights the potential importance of surface water and hyporheic zone linkages for riverine invertebrate communities under a range of flow conditions

Lowering Real Interest Rates Could Slow Global Warming

Carbon dioxide emissions from fossil fuel combustion have increased markedly in this century. Increased carbon dioxide concentrations in the atmosphere are thought likely to help produce a warming of global climate. Many strategies to reduce or reverse the anticipated global warming point to reductions of fossil fuel combustion as a primary ingredient. This paper examines the possibility of obtaining a decrease in world petroleum supply as a result of reducing interest rates relative to the rate of inflation

Norm Contestation in the Law Against War: Towards an Interdisciplinary Analytical Framework

According to a widely shared perception, international peace and security law is in crisis. Yet it often remains unclear what the constitutive features of this crisis are, how novel it really is, and what its sources, forms, and effects are. In the introduction to this symposium, we unpack the current crisis narrative by focussing on norm contestation in the law against war: Which norms are contested? Who are the actors that contest these norms and how? What are the effects of these contestations on peace and security law as a whole? To answer these questions, we draw on recent scholarship on illegality in Public International Law (PIL) and on contestation in International Relations (IR); we propose an interdisciplinary analytical framework that distinguishes between applicatory, legislative, and systemic contestation. Challenges to the application of norms and the factual basis are a common theme in legal disputes that specify international norms. Legislative contestation challenges the content of norms on a more abstract level, aiming to change its boundaries. Systemic contestation fundamentally questions the cornerstones of the international order. This typology invites PIL and IR scholars to study how different forms of contestation shape international norms in the law against war

Introduction: International Law Governing Armed Conflict

Wars are emergency situations, but in contrast to the saying according to which necessity knows no law, they are not lawless situations at all. Quite to the contrary, an extensive body of international treaties and customary international law provides detailed regulations. However, which rules do and should apply to what kinds of situation is a hotly debated issue and the subject of this book. Different regulatory paradigms are competing for how wartime situations shall be regulated – with significant legal, practical and institutional implications. This book approaches the legal issue in a Trialogue. The characteristic feature of a Trialogue is to approach questions of international law from three perspectives, which differ in terms of their regional background, technical method, professional specialisation and worldview of the co-authors. The three authors (who are embedded in their particular social and cultural context) approach the law from their particular perspective, which invariably influences what they identify as the relevant rules and how they interpret and apply those. The core method of the ‘Max Planck Trialogues on the Law of Peace and War’ is to positively acknowledge the diversity of perspectives, and to make constructive use of them (multi-perspectivism)

Bacterial Community Composition in Central European Running Waters Examined by Temperature Gradient Gel Electrophoresis and Sequence Analysis of 16S rRNA Genes

The bacterial community composition in small streams and a river in central Germany was examined by temperature gradient gel electrophoresis (TGGE) with PCR products of 16S rRNA gene fragments and sequence analysis. Complex TGGE band patterns suggested high levels of diversity of bacterial species in all habitats of these environments. Cluster analyses demonstrated distinct differences among the communities in stream and spring water, sandy sediments, biofilms on stones, degrading leaves, and soil. The differences between stream water and sediment were more significant than those between sites within the same habitat along the stretch from the stream source to the mouth. TGGE data from an entire stream course suggest that, in the upper reach of the stream, a special suspended bacterial community is already established and changes only slightly downstream. The bacterial communities in water and sediment in an acidic headwater with a pH below 5 were highly similar to each other but deviated distinctly from the communities at the other sites. As ascertained by nucleotide sequence analysis, stream water communities were dominated by Betaproteobacteria (one-third of the total bacteria), whereas sediment communities were composed mainly of Betaproteobacteria and members of the Fibrobacteres/Acidobacteria group (each accounting for about 25% of bacteria). Sequences obtained from bacteria from water samples indicated the presence of typical cosmopolitan freshwater organisms. TGGE bands shared between stream and soil samples, as well as sequences found in bacteria from stream samples that were related to those of soil bacteria, demonstrated the occurrence of some species in both stream and soil habitats. Changes in bacterial community composition were correlated with geographic distance along a stream, but in comparisons of different streams and rivers, community composition was correlated only with environmental conditions