The Nanocluster Trap endstation at BESSY II

The Nanocluster Trap endstation at BESSY II combines a cryogenic linear radio-frequency ion trap with an applied magnetic field for x-ray magnetic circular dichroism studies of cold and size-selected trapped ions. Applications include atomic, molecular, and cluster ions as well as ionic complexes

Declining calcium concentration drives shifts toward smaller and less nutritious zooplankton in northern lakes

Zooplankton community composition of northern lakes is changing due to the interactive effects of climate change and recovery from acidification, yet limited data are available to assess these changes combined. Here, we built a database using archives of temperature, water chemistry and zooplankton data from 60 Scandinavian lakes that represent broad spatial and temporal gradients in key parameters: temperature, calcium (Ca), total phosphorus (TP), total organic carbon (TOC), and pH. Using machine learning techniques, we found that Ca was the most important determinant of the relative abundance of all zooplankton groups studied, while pH was second, and TOC third in importance. Further, we found that Ca is declining in almost all lakes, and we detected a critical Ca threshold in lake water of 1.3 mg L-1, below which the relative abundance of zooplankton shifts toward dominance of Holopedium gibberum and small cladocerans at the expense of Daphnia and copepods. Our findings suggest that low Ca concentrations may shape zooplankton communities, and that current trajectories of Ca decline could promote widespread changes in pelagic food webs as zooplankton are important trophic links from phytoplankton to fish and different zooplankton species play different roles in this context.Among five environmental variables tested, we found that low lake calcium (Ca) concentrations shape most zooplankton communities in northern lakes. When lake water Ca falls below a threshold of 1.3 mg L-1, the relative abundance of zooplankton shifts toward dominance of Holopedium and small cladocerans at the expense of Daphnia and cyclopoid and calanoid copepods. The current trajectory of Ca declines found in northern lakes implies community shifts toward dominance of smaller and less nutritious zooplankton. Ca declines potentially have strong repercussions for lake food webs and productivity as zooplankton are important trophic links from phytoplankton to fish.imag

Phytoplankton biomass in northern lakes reveals a complex response to global change

Global change may introduce fundamental alterations in phytoplankton biomass and community structure that can alter the productivity of northern lakes. In this study, we utilized Swedish and Finnish monitoring data from lakes that are spatially (135 lakes) and temporally (1995-2019, 110 lakes) extensive to assess how phytoplankton biomass (PB) of dominant phytoplankton groups related to changes in water temperature, pH and key nutrients [total phosphorus (TP), total nitrogen (TN), total organic carbon (TOC), iron (Fe)] along spatial (Fennoscandia) and temporal (25 years) gradients. Using a machine learning approach, we found that TP was the most important determinant of total PB and biomass of a specific species of Raphidophyceae - Gonyostomum semen - and Cyanobacteria (both typically with adverse impacts on food-webs and water quality) in spatial analyses, while Fe and pH were second in importance for G. semen and TN and pH were second and third in importance for Cyanobacteria. However, in temporal analyses, decreasing Fe and increasing pH and TOC were associated with a decrease in G. semen and an increase in Cyanobacteria. In addition, in many lakes increasing TOC seemed to have generated browning to an extent that significantly reduced PB. The identified discrepancy between the spatial and temporal results suggests that substitutions of data for space-for-time may not be adequate to characterize long-term effects of global change on phytoplankton. Further, we found that total PB exhibited contrasting temporal trends (increasing in northern- and decreasing in southern Fennoscandia), with the decline in total PB being more pronounced than the increase. Among phytoplankton, G. semen biomass showed the strongest decline, while cyanobacterial biomass showed the strongest increase over 25 years. Our findings suggest that progressing browning and changes in Fe and pH promote significant temporal changes in PB and shifts in phytoplankton community structures in northern lakes

Zooplankton in northern lakes show taxon-specific responses in fatty acids across climate-productivity and ecosystem size gradients

Northern lakes are facing rapid environmental alterations-including warming, browning, and/or changes in nutrient concentrations-driven by climate change. These environmental changes can have profound impacts on the synthesis and trophic transfer of polyunsaturated fatty acids (PUFA), which are important biochemical molecules for consumer growth and reproduction. Zooplankton are a key trophic link between phytoplankton and fish, but their biochemical responses to environmental change are not well understood. In this study, we assess the trends in fatty acid (FA) composition of zooplankton taxa among 32 subarctic and temperate lakes across broad climate-productivity and ecosystem size gradients. We found that genus-level taxonomy explained most FA variability in zooplankton (54%), suggesting that environmental changes that alter the taxonomic composition also affect the FA composition of zooplankton communities. Furthermore, the FA responses and their underlying environmental drivers differed between cladocerans and copepods. Cladocerans, including widespread Bosmina spp. and Daphnia spp., showed pronounced responses across the climate-productivity gradient, with abrupt declines in PUFA, particularly eicosapentaenoic acid and arachidonic acid in warmer, browner, and more eutrophic lakes. Conversely, calanoid copepods had high and relatively stable PUFA levels across the gradient. In addition, all zooplankton taxa increased in stearidonic acid levels in larger lakes where PUFA-rich cryptophytes were more abundant. Overall, our results suggest that climate-driven environmental alterations pose heterogeneous impacts on PUFA levels among zooplankton taxa, and that the negative impacts of climate warming are stronger for cladocerans, especially so in small lakes

Den kollektive læsnings anarki

Denne artikel analyserer, hvordan kunstnerkollektivet Sort Samvittighed bearbejder og bruger litterære tekster i deres forestilling I et forhold fra 2019. Den beskriver deres metode som grundlæggende prattein (van Eikels) med et fokus på forbindelser, kollaborationer og reaktioner frem for forfatternes eventuelle intentioner. Den argumenterer for, at denne praksis skaber et åbent værk, der etablerer fællesskab (Nancy) mellem kunstnerne, forfatterne og publikum

A Policy-Oriented Narrative Approach to IR

Yamin and Depledge (2004) argue that the UNFCCC regime is characterised by formal and informal coalitions, alliances, and political groups. Blaxekjær and Nielsen (2014) have demonstrated how new groups since COP15 have transformed the narrative positions and negotiations space in the UNFCCC, creating bridges as well as new trenches between North and South in relation to the principle of Common But Differentiated Responsibility. As the UNFCCC regime readjusts after COP21, these new narrative positions and negotiations space should be re-examined. Through original data such as official statements from groups, observations at UN climate conferences (2011-2015), and interviews with delegates and experts, the paper analyses the narrative position of the Like Minded group of Developing Countries (LMDC), an influential political group under the UNFCCC established in 2012. Following Blaxekjær and Nielsen’s (2014) policy-oriented narrative approach to IR the paper analyses LMDC’s identity, the problems identified by LMDC and the solutions to these problems, and the paper identifies five central characteristics of the dominant LMDC narrative. The analysis also touches upon what narrative techniques are used in constructing the LMDC identity. This framework reveals the embeddedness of narratives in practice as they unfold in the formation of new alliances and ruptures in old ones. This paper contributes to the emerging Narrative in IR research agenda with a policy-oriented model of analysis. The paper also contributes to the broader research agenda on the post-Paris UNFCCC regime, and argues that as long as CBDR/RC is a major unresolved issue – an essentially contested concept – as long will the LMDC play a prominent role in the UNFCCC regime

Atomtronic multi-terminal Aharonov-Bohm interferometer

We study a multi-functional device for cold atoms consisting of a three-terminal ring circuit pierced by a synthetic magnetic flux. The flux controls the atomic current through the ring via the Aharonov-Bohm effect. Our device can measure the flux in-situ via a flux-induced transition of the reflections from an Andreev-like negative density to positive density. In the non-equilibrium regime, the flux directs the atomic current into specific output ports, realizing a flexible non-reciprocal switch to connect multiple atomic systems. By changing the flux linearly in time, we convert constant matter wave currents into alternating currents. This effect can be used to realize an atomic frequency generator and study fundamental problems related to the Aharonov-Bohm effect. We demonstrate the viability of the setup by loading a Bose-Einstein condensate into a light-shaped optical potential of the three-terminal ring. Our work opens up novel atomtronic devices for practical applications in quantum technologies.Comment: 11 pages, 9 figure