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Cold-water coral sensitivity: growth, morphology and reef-forming potential of Desmophyllum pertusum in response to environmental factors
No full textThe deep ocean is home to vast and flourishing cold-water coral (CWC) reefs, formed by a handful of widely distributed scleractinian CWC species. These structurally complex habitats host a rich diversity of associated species (ranging from microbes to fish), contribute significantly to the carbon cycle and deeply affect local sediment deposition. Over thousands and millions of years, CWC buildups can develop into massive carbonate mounds. All these fundamental geo-ecological functions are intimately tied to the morphology of CWCs, because the skeletal framework of these ecosystem engineers directly shapes the reef habitat. Hence, understanding how reef-building CWCs grow in response to environmental conditions can shed light on deep-sea reef formation, ecosystem functioning and vulnerability to environmental (including human-induced) change. CWCs exhibit a high degree of morphological variability (often regarded as plasticity), but despite its ecosystem significance, patterns and drivers of this variability are still poorly understood and challenging to study, due to the limited accessibility and slow growth of these species. This thesis aims to improve our understanding of how the growth, morphology and reef-forming potential of CWCs vary in response to their environmental setting. To this end, the focus is on Desmophyllum pertusum (syn. Lophelia pertusa), one of the most widespread and best-known reef-building CWC species, which occurs over a broad range of environmental conditions. The intraspecific variation in growth and morphology of D. pertusum and its physicochemical hydrographic drivers were qualitatively and quantitatively investigated across multiple structural levels (from individual polyps to whole colonies) and geographic scales (from microhabitat to ocean basin), using a large Atlantic-wide collection of underwater imagery and skeletal samples. Characterisation of global patterns of morphological variation in D. pertusum led to the identification of three main colony morphotypes, which indicate that polyp budding is a key mechanism of colony shape determination and suggest a major influence of hydrodynamics on coral growth. This latter hypothesis was explicitly tested by creating digital 3D models of corals from adjacent Norwegian sites with contrasting flow regimes and comparing their 3D framework architecture. Polyp phenotypic variation in relation to flow speed and other physiologically relevant hydrographic factors was then analysed on a global scale. Findings reveal high phenotypic plasticity and suggest that variation in polyp budding and corallite morphology are widespread responses of D. pertusum to various hydrographic factors (dissolved oxygen, temperature and flow speed in particular). Such responses are highly relevant for the growth and morphology of the CWC reef framework, although CWC sensitivity to hydrographic factors seems to somewhat differ among regions, and the interaction between multiple forcing factors may also play an important role. In particular, climate change stressors (ocean warming and deoxygenation) and increasing current speeds could have contrasting effects on CWC reef growth, by respectively hampering and favouring polyp growth and framework compactness. The present work represents the first characterisation of species-wide morphological variation and its environmental drivers in a reef-building CWC, and advances our knowledge of the relationship between CWCs and their physicochemical environment. This knowledge can be used to model CWC reef responses to environmental change and, vice versa, to infer past and present environmental conditions and reef health from CWC phenotypic traits
Many paths to qualified work in Germany - key features of an intransparent school system
No full textDas Schulsystem ist in den 16 deutschen Bundesländern unterschiedlich ausgestaltet. Dadurch ist es kompliziert und unübersichtlich. Einige zentrale zentrale Merkmale lassen sich identifizieren. Es gibt ein System von Schulabschlüssen. Zu diesen Abschlüssen führt Unterricht mit unterschiedlichen Schwierigkeitsgraden. Abschlüsse können an allgemein- und berufsbildenden Schulen erreicht werden, in der Pflichtschulzeit oder nach einer Phase der Berufstätigkeit. Unterrichts- und Prüfungssprache ist in der Regel Deutsch
Honor, dignity, and migration: navigating cultural norms and threat responses among native Indians, Germans, and Indian migrants in Germany
No full textThe present dissertation examines the role of honor and dignity norms in individual reactions to threats against one’s reputation and intrinsic sense of being among two distinct groups: natives of honor and dignity cultures, and migrants transitioning from honor to dignity cultures. In doing so, it addresses three key research questions: how are honor and dignity perceived as distinct aspects of self-worth in honor and dignity cultures; are there differences in the endorsement of these norms between natives of these cultures and migrants who move between them; and what role do these norms play in one’s reactions when their honor and dignity are threatened.
To address these questions, the thesis employs a mixed-methods approach. It begins with a qualitative exploratory study involving focus group discussions conducted in India and Germany, which were chosen as representative cases of honor and dignity cultures, respectively. This study aimed to explore what people in these cultural contexts mean when they act in the name of honor or strive to uphold dignity. Building on the insights from this qualitative work, a subsequent quantitative study was conducted which tested the norm endorsement and reactions to different threat scenarios, developed from the qualitative findings, among native Indians, Germans, and Indian migrants in Germany.
The findings from both studies make important contributions to two broad areas: acculturation within the honor-dignity paradigm; and the understanding of dignity as a facet of self-worth. These contributions have important implications for broader research in cross-cultural psychology, particularly within the honor-dignity framework, as well as practical applications in the context of migrant integration and cross-culturally sensitive interpersonal behavior
The far-reaching effect of the production, degradation, and trophic transfer of organic arsenic species in the cycle of arsenic
No full textSeveral organic compounds in aquatic environments contain arsenic, despite of its toxicity. Lipid-soluble arsenic-containing compounds, also known as arsenolipids, are the least studied. In fact, the metabolic origin, purpose and fate of arsenolipids remain shrouded in mystery. Particularly within the microbial realm their role in the arsenic cycle, and significance within trophic webs is still unknown. This thesis aims at improving our understanding about arsenolipids in terms of: 1) the factors that govern their production in microorganisms, 2) their lability, and 3) their trophic transfer from microbial primary producers to eukaryotic grazers. Considering these three approaches, this doctoral thesis follows the path of arsenic starting from cellular pathways to the aquatic environment, and ultimately through food webs, with the aim of assessing how the microbial production of arsenolipids influences arsenic cycling, and which are the factors that affect them.
Arsenic methylation is a key process in the arsenic cycle, converting inorganic arsenic into methylated organic products that can evaporate, altering arsenic mobility. Evidence shows that the subsequent methylation of the highly toxic monomethylarsine (MMA) to a less toxic dimethylarsine (DMA) is regulated by thioredoxin (TRX), which in phototrophs TRX is tightly modulated by oxygenic photosynthesis and light. In Chapter I of this thesis, we investigated how light influences arsenic methylation in phototrophic microorganisms, and what effects could this have on arsenolipid production and arsenic mobility in the environment. We hypothesized that light would drive arsenic methylation and boost DMA production, while production of MMA will predominate in darkness. Using model cyanobacterial cultures and samples from natural arsenic-rich lakes, we found that light stimulates DMA production, while dark anoxic conditions promote toxic MMA production, possibly serving as an antibiotic. Dark oxic settings had no overall influence. This finding provides the first evidence of a physical factor such as light that can influence arsenic methylation, which can also impact arsenolipid production, as DMA is a crucial precursor for their synthesis. These results provide insights as to why arsenolipids are found to be synthesized by phototrophs, with the influence of light on arsenic methylation having an important role. This can also impact arsenic cycling, as the final methylated organic products that can evaporate out of the water column and remove arsenic from the system. Ultimately, this study found that light and oxygenic photosynthesis can be important regulators in the production of methylated arsenic species, which can influence the production of arsenolipids and arsenic cycling.
So how can arsenolipids affect the arsenic cycle? And can light also have an effect on their abundance? In Chapter II, we delved deeper into these questions by characterizing how light affects the occurrence and concentration of arsenolipids within a naturally arsenic-rich microbial mat, as well as their degradation under laboratory conditions. We found arsenolipids in both the mat and water column, predominantly as novel phytyl 2-O-methyl arsenoribosides (arsenosugar phytols/AsPhy). The initial parent arsenosugar phytol (AsPhy 547) was rare in the mat, whereas its shorter chain degradation product (AsPhy 521) was abundant at the mat's surface but absent at greater depths. Given the absence of the initial parent AsPhy 547 on the light-exposed top of the mat and the high abundance of the shorter chain AsPhy 521, we hypothesized that light could degrade AsPhy 547 to AsPhy 521. Results showed light-driven degradation of AsPhy 547 within 24 hours, while AsPhy 521 was more resistant and increased in abundance, suggesting that it is a degradation product. In the dark, all AsPhy were preserved over 63 days. These results could explain the absence of the initial arsenosugar phytol in the illuminated surface layers of the mat, as well as the higher abundance of its degradation products there. AsPhy are so far only known to be made by microalgae, and since the studied mats were cyanobacteria-dominated, we suspect a microalgal-pelagic origin of these AsPhy, with their presence in sediment as detritus. The recalcitrant nature of degraded AsPhy that they can be a sink of arsenic, which eventually degrade over very long period of time with continued burial. These results show that the production of arsenolipids by microorganisms can impact arsenic cycling, as some of their degradation products can be highly refractile, and that light can be an important factor modulating their mobility.
To better understand the role of arsenolipids in the arsenic cycle, studying their transport through the trophic web, from microbial producers to eucaryotes, is crucial. In the arsenic-rich hypersaline lakes of our studies, the aquatic grazer artemia are the main link between microalgae and larger eucaryotes. In Chapter III, we examined artemia's accumulation of arsenolipids during the diel cycle, considering reproductive sex. We conducted feeding experiments on both captured and commercial artemia with arsenic-enriched or non-enriched microalgal food, or under fasting conditions. Results showed that artemia primarily contained arsenosugar phytols (AsPhy) 547 and 521, similar to those in microorganisms from the same lakes, indicating uptake through feeding. In one site, female artemia contained higher amounts of arsenolipids than males, while arsenolipid content was similar between sexes in another site, hinting that environmental factors influence uptake. Long-term fasting and feed-washing incubations showed no significant decrease in arsenolipids, suggesting they are not stored in energy reserves affected during catabolism. Fecal pellets also contained arsenolipids, demonstrating artemia’s role actively in transportation arsenic from microalgae in the water column into the sediment. Thus, we show that the transfer of arsenolipids to eukaryotic grazers can influence arsenic cycling through transport of arsenolipids from the water column to the sediment, as well as their retention in tissue.
Overall, the findings of this study show that microbial organisms, through the production of organic arsenic species, affect arsenic cycling across different scales and facets, starting from the molecular in their synthesis and degradation, to the interaction between organisms as antibiotics, and finally at ecosystem level throughout the food web
Detecting animals in challenging outdoor environments
No full textMonitoring wildlife is vital for sustainable coexistence between humans, flora, and fauna. Do we have a healthy population? Is an animal near extinction, or did new species arrive in the habitat? Where do the animals stay, hunt, and live? Forest rangers, livestock owners, and other interested people place camera traps to answer those questions. Those camera traps automatically take photos if motion is detected, which easily leads to many images to be analyzed.
The quality of those photos often varies and depends on the environment. Animals usually do not stand directly close in front of the lens but are partly covered by the fauna or only barely visible in the distance. Furthermore, precipitation, fog, dirt, and many other conditions additionally decrease the image quality and hinder the detection of animals.
Our interest comes from our mAInZaun project. The idea is to place cameras on the poles of pasture fences. Deterrents are automatically activated using artificial intelligence if predators like wolves, golden jackals, stray dogs, etc., are detected. Ideally, this approach should reduce the predator attacks on grazing animals in a non-lethal way. The automatic activation of the deterrents requires a good detection of predators. Both, false alarms and undetected predators, must be prevented and require a good detection model.
Training a model detecting animals requires a certain amount of training data in the form of labeled images. The interest is not only in the clearly visible animals but especially in the hard-to-see ones. Furthermore, the model has to be adapted occasionally to ensure good performance in different environments or if new species have to be detected.
This work addresses those challenges with our ShadowWolf framework, which offers an assisted approach for automatically labeling camera trap images. Using state-of-the-art machine-learning algorithms in combination with internet-based crowdsourcing significantly increases the detection of animals and reduces the workload for individual domain experts simultaneously. The outcome is a training dataset that can be used to train arbitrary object detection and classification algorithms. The user can select the appropriate model to run on different devices -- from constrained edge devices to a high-end server.
We also collected and analyzed our dataset containing more than 100,000 camera trap images to evaluate our ShadowWolf framework. We also discuss deploying a sensor network tailored for our agriculture application.
In the end, this work benefits everybody dealing with real-world wildlife camera trap images: Counting animals, detecting predators, and optimizing automatic machine learning models are simplified and also usable by non-technical people
Das Battlefield der Legitimität: Wie bewaffnete Gruppen Gewalt und Werte im Kampf um internationale Anerkennung nutzen
No full textHow armed groups legitimise themselves on the international stage is a critical question given the considerable influence they wield in global politics. Yet, it has seldom been systematically investigated. By addressing this question, this thesis fills a gap on the empirical understanding and theorisation of the rebels’ international legitimacy politics. This lacuna persists at the intersection of International Relations (IR), legitimacy theory, and conflict research. The study challenges the marginalisation of armed groups in legitimacy research in IR and exposes the limitations of classical legitimacy theory in contexts of political disorder where armed groups are the agents seeking legitimacy. The study also critiques traditional IR and conflict research perspectives in which rebels’ foreign politics is often viewed from a state-centric lens or compartmentalised. While emerging debates in conflict research have paid attention to rebel legitimacy beyond the domestic terrain, these debates have fallen short of advancing a holistic understanding of the matter. The thesis, by contrast, eschews the outside-in analysis of armed groups as it develops a heuristic framework—integrating armed action, identity projection, and communication strategies—to unravel the intricacies of their legitimacy. Through a comparative case study of the key conflict players, the Syrian Kurdish People’s Defence Units (YPG) and the Afghan Taliban, utilising in-depth interviews and textual analysis of primary sources, this thesis yields four key insights. First, moving beyond the classical dyadic (two-actor) conceptualisation of legitimacy relations, rebel legitimacy is best understood as a triadic (three-actor) dynamic. Second, regional support serves as a stepping stone for international recognition. Third, although violence is a double-edged sword, it remains armed groups’ primary repertoire for contesting legitimacy. Fourth, rebels with values and identities deviating from Western norms face additional hurdles in their quest for international integration. Finally, the thesis’ emphasis on armed groups as agents co-shaping international relations, reveals two promising future research avenues. One of them is how armed groups influence inter-state relations. The other is how rebels act simultaneously as disruptors and reproducers of established power and normative configurations in international order. Exploring these avenues holds the potential for opening up new ways for understanding international relations and interrogating mainstream IR theorisation
Regional Variation in German Real Estate Prices: Socio-Economic and Pandemic Influences
No full textThis study examines the real estate market in Germany at the district level, focusing on 401 NUTS 3 regions from 2012 to 2022. Using spatial econometric models, the analysis explores how socio-economic variables and COVID-19-related factors—including infection rates and mobility restrictions—affected regional property prices. Our results indicate that high infection rates and containment measures served as significant housing price drivers, with both direct effects within regions and indirect spillover effects to neighbouring regions. We find that these factors, along with socio-economic variables such as average age and childcare provision, contribute to spatial dynamics in property markets. Robustness checks across regional subgroups and different model specifications support these fin dings. The research contributes to the literature by quantifying the influence of socio-economic and pandemic-related factors on regional real estate price variations and providing evidence of spatial spillover effects. The findings highlight the need for regionally tailored real estate policies to address the diverse impacts of these factors on property markets in Germany, while also offering a framework for analysing similar dynamics in other countries.240213
Agentiver und Nonagentiver Widerspruch – Eine Kartographie der linguistischen Widerspruchsforschung
No full textPublikation der U Bremen und U Wien internationalen Studierendenkonferenz »Debattieren, Opponieren, Protestieren – Interdisziplinäre Perspektiven auf sprachliche Praktiken des Widersprechens« 2023.668
Deciphering gas phase synthesis of sulfide nanoparticles
No full textWith the ever-increasing need for impressively engineered materials, research has taken a shine to nanosized materials. This has been predominantly because matter on a nanoscale exhibits behaviours unusual to their bulk counterparts. Taking advantage of these properties on the nanoscale has been applied in many areas of research.
This thesis is focused on a particular group of nanomaterials – metal sulfides and their production through combustion synthesis. Metal sulfide nanoparticles are attractive materials for a wide range of applications. The synthesis of metal sulfide nanoparticles has predominantly been through liquid-phase synthesis. Although it can be highly versatile, challenges of scaling up production and the requirement for post-processing exist. Combustion of liquid precursors using a flame set-up is an established and highly scalable route of synthesis for metal oxide nanoparticles. As combustion requires oxygen, the synthesis of metal sulfides through this route is a challenge. This thesis delves into sources of metal and sulfur sources that are ideal for producing metal sulfide nanoparticles through combustion, tailored precursor-solvent solutions and mechanisms of breakdown and formation. Here, tetrahydrothiophene (THT) is used as an effective source of sulfur to produce metal sulfide nanoparticles such as those of copper and iron.
In addition, specific components formed on the high-temperature breakdown of the sulfur source are investigated. Precursor-solvent solutions are poked and prodded using evaporation and distillation, the results of which were unexpected nor have been reported in prior studies
Surfing the heatwave: Understanding the influence of marine heatwaves in driving community dynamics and species performance in the North Sea
No full textAs a consequence of anthropogenic climate change, the frequency, duration and magnitude of extreme weather events are increasing and expected to rise further in the coming decades. Among them, marine heatwaves (MHWs) are driving significant ecological changes worldwide, including mass mortalities, shifts in species distributions, and biodiversity loss. Growing concerns about MHW impacts have led to intensified research efforts to define, categorize, and assess their consequences across different levels of biological organisation.
Despite this increasing attention, key knowledge gaps remain. The unpredictable nature of MHWs makes it challenging to quantify their effects on marine communities. Moreover, most studies on climate change focus on rising mean temperatures, often overlooking biological responses to thermal fluctuations, which can differ from those under constant conditions. Research has also largely concentrated on coral reefs and fish, with less attention to plankton, a key component of marine food webs.
This thesis quantifies MHW effects on individuals, populations and communities using zooplankton as model organisms. It consists of two main blocks: (1) analysing historical time series data to assess MHW impacts on mesozooplankton in the North Sea and (2) conducting laboratory experiments to evaluate how present and future MHWs affect the survival, growth, and phenology of meroplankton larvae.
Findings reveal that MHW impacts on zooplankton communities vary by season, emphasizing the need for season-specific studies. Copepods, a key zooplankton group, are unable to adjust their phenology in response to MHWs occurring before their bloom. The lack of a phenological shift, combined with rising MHW days and temperature increase rates, can lead to faster and more or less intense blooms, with potential repercussions for higher trophic levels. The thesis also shows that MHW effects on species performance differ from those of general warming, as MHW components interact in complex ways. Species resilient to warmer temperature or invasive species may benefit from MHWs, often at the expense of native species. As MHWs continue to grow stronger, more frequent and longer, understanding the link between their components and their ecological and socio-economic consequences will become increasingly crucial