Sediment erosion and transport is critical to the ecological and commercial health of aquatic habitats from watershed to sea. There is now a consensus that microorganisms inhabiting the system mediate the erosive response of natural sediments ('ecosystem engineers') along with physicochemical properties. The biological mechanism is through secretion of a microbial organic glue (EPS: extracellular polymeric substances) that enhances binding forces between sediment grains to impact sediment stability and post-entrainment flocculation. The proposed work will elucidate the functional capability of heterotrophic bacteria, cyanobacteria and eukaryotic microalgae for mediating freshwater sediments to influence sediment erosion and transport. The potential and relevance of natural biofilms to provide this important 'ecosystem service' will be investigated for different niches in a freshwater habitat. Thereby, variations of the EPS 'quality' and 'quantity' to influence cohesion within sediments and flocs will be related to shifts in biofilm composition, sediment characteristics (e.g. organic background) and varying abiotic conditions (e.g. light, hydrodynamic regime) in the water body. Thus, the proposed interdisciplinary work will contribute to a conceptual understanding of microbial sediment engineering that represents an important ecosystem function in freshwater habitats. The research has wide implications for the water framework directive and sediment management strategies.
Fällt ein Regentropfen auf eine Wasseroberfläche oder platzt dort eine Gasblase, so wird in einem komplizierten strömungsmechanischen Prozess eine Vielzahl kleinster Tröpfchen produziert und in die Luft geschleudert. Diese Tröpfchen können ursprünglich im Wasser vorhandene Mikroplastikpartikel in die Luft übertragen. Da sowohl Regen als auch platzende Gasblasen in natürlichen und technischen Systemen wie Ozeanen, Pfützen oder Kläranlagen extrem häufige Ereignisse sind, liegt hier ein potenziell hochrelevanter Migrationspfad von Mikroplastik aus der Hydro- in die Atmosphäre vor. Dieser Prozess soll im vorliegenden Projekt durch eine Kombination aus Modell-Experimenten und Computersimulationen im Detail untersucht und verstanden werden.
Up to recent years, the study of trends and variability of the salinity (and freshwater) distributions was hampered by the lack of temporal and spatial resolution of the available observations (Wang DFG form 54.011 - 1/12 page 3 of 6 et al., 2010). With the onset of the Argo programme, the number of observed salinity profiles have significantly increased. The many Argo profiles distributed evenly over the year provide not only the means to calculate seasonally averaged salinity (and freshwater) distributions, but they can also be used to calculate regional Gravest Empirical Modes (GEMs) parameterized by pressure and dynamic height. Dynamic height is measured by altimetry and high quality altimeter data are available since 1992. GEMs will be used to construct from altimetry high resolution (in time and space) salinity, temperature and density fields. The objectives of the proposal are to - combine Argo/CTD profiles and altimetry to calculate temporal and spatial high resolution salinity fields in the mixed layer and in the upper 1500-2000m for the time period 1992 - 2013 for the subpolar and the subtropical Atlantic. - Construct regional freshwater budgets for the mixed layer and the upper 1500-2000m and estimate the contributions of the main processes to the observed change - Follow salinity anomalies from their origin along their circulation pathways, and study involved mechanisms (for instance role of eddies, mean circulation) for shallow, intermediate and deep water masses - Investigate changes in the formation of North Atlantic mode waters in the subpolar and subtropical gyre
Verschiedene Modell-MP-Partikel sowie Modellpartikel für natürlich vorkommendes partikulares Material werden in Süßwasser und Boden inkubiert und daraus resultierende Oberflächenveränderungen werden biomolekular und physikalisch-chemisch charakterisiert. Daraufhin werden unterschiedliche Polyelektrolyt-Multilagen-beschichtete Modellpartikel hergestellt, welche in jeweils einer Eigenschaft (z.B. identische Mechanik oder Ladungsdichte) den inkubierten Partikeln gleichen. Durch einen Vergleich der verschiedenen Partikel wird daraufhin die Relevanz dieser Eigenschaft für die Adhäsion der Partikel an Zellen und die Internalisierung in Zellen quantitativ untersucht.
Cydia pomonella granulovirus (CpGV, Baculoviridae) is one of the most important agents for the control of codling moth (CM, Cydia pomonella, L.) in both biological and integrated pest management. The rapid emergence of resistance against CpGV-M, which was observed in about 40 European CM field populations from 2003 on, could be traced back to a single, dominant, sex-linked gene. Since then, resistance management has been based on mixtures of new CpGV isolates (CpGV-I12, -S), which are able to overcome this resistance. Recently, resistance even to these novel isolates was observed in CM field populations. This resistance does not follow the described dominant, sex-linked inheritance trait. At the same time, another isolate CpGV-V15 was identified showing high virulence against these resistant populations. To elucidate this novel resistance mechanism and to identify the resistance gene(s) involved, we propose a comprehensive analysis of this resistance on the cellular and genomic level of codling moth. Because of the lack of previous knowledge of the molecular mechanisms of virus resistance in insects, several different and complementary approaches will be pursued. This study will not only give an in-depth insight into the genetic possibilities for development of baculovirus resistance in CM field populations and how the virus overcomes it, but can also serve as an important model for other baculovirus-host interaction systems.
The decomposition of terrestrial organic material such as leaf litter represents a fundamental ecosystem function in streams that delivers energy for local and downstream food webs. Although agriculture dominates most regions in Europe and fungicides are applied widely, effects of currently used fungicides on the aquatic decomposer community and consequently the leaf decomposition rate are largely unknown. Also potential compensation of such hypothesised adverse effects due to nutrients or higher average water temperatures associated with climate change are not considered. Moreover, climate change is predicted to alter the community of aquatic decomposers and an open question is, whether this alteration impacts the leaf decomposition rate. The current projects follows a tripartite design to answer these research questions. Firstly, a field study in a vine growing region where fungicides are applied in large amounts will be conducted to whether there is a dose-response relationship between the exposure to fungicides and the leaf decomposition rate. Secondly, experiments in artificial streams with field communities will be carried out to assess potential compensatory mechanisms of nutrients and temperature for effects of fungicides. Thirdly, field experiments with communities exhibiting a gradient of taxa sensitive to climate change will be used to investigate potential climate-related effects on the leaf decomposition rate.
Farm structures are often characterized by regional heterogeneity, agglomeration effects, sub-optimal farm sizes and income disparities. The main objective of this study is to analyze whether this is a result of path dependent structural change, what the determinants of path dependence are, and how it may be overcome. The focus is on the German dairy sector which has been highly regulated and subsidized in the past and faces severe structural deficits. The future of this sector in the process of an ongoing liberalization will be analyzed by applying theoretical concepts of path dependence and path breaking. In these regards, key issues are the actual situation, technological and market trends as well as agricultural policies. The methodology will be based on a participative use of the agent-based model AgriPoliS and participatory laboratory experiments. On the one hand, AgriPoliS will be tested as a tool for stakeholder oriented analysis of mechanisms, trends and policy effects. This part aims to analyze whether and how path dependence of structural change can be overcome on a sector level. In a second part, AgriPoliS will be extended such that human players (farmers, students) can take over the role of agents in the model. This part aims to compare human agents with computer agents in order to overcome single farm path dependence.
The energetic efficiency of C4 photosynthesis is strongly affected by bundle sheath leakiness, which is commonly assessed with the 'linear version' of the Farquhar model of 13C discrimination, and leaf gas exchange and 13C composition data. But, the linear Farquhar model is a simplification of the full mechanistic theory of ? in C4 plants, potentially generating errors in the estimation of leakiness. In particular, post-photosynthetic C isotope fractionation could cause large errors, but has not been studied in any detail. The present project aims to improve the understanding of the ecological and developmental/physiological factors controlling discrimination and leakiness of the perennial grass Cleistogenes squarrosa. C. squarrosa is the most important member of the C4 community which has spread significantly in the Mongolia grasslands in the last decades. It has an unusually high and variable discrimination, which suggests very high (and potentially highly variable) leakiness. Specifically, we will conduct the first systematic study of respiratory 13C fractionation in light and dark at leaf- and stand-scale in this C4 species, and assess its effect on discrimination and estimates of leakiness. These experiments are conducted in specialized 13CO2/12CO2 gas exchange mesocosms using ecologically relevant scenarios, testing specific hypotheses on effects of environmental drivers and plant and leaf developmental stage on discrimination and leakiness.
Verlässliche Vorhersagen von Wetter und Klimawandel erfordern ein gutes Verständnis der Eisbildung in troposphärischen Wolken. Von besonderer Bedeutung ist dabei die sogenannte heterogene Eisnukleation durch atmosphärische Aerosolpartikel. Das hier beantragte Projekt beinhaltet eine umfassende Untersuchung der heterogenen Eisnukleation in Zirruswolken und Mischphasenwolken, gemeinsam mit 8 weiteren Projekten der Forschergruppe INUIT. Eisbildung durch Kontaktgefrieren wird für einzelne Tröpfchen in einem elektrodynamischen Levitator (Paulfalle) untersucht. Experimente zum Einfluss von Aerosolen auf Immersionsgefrieren, Kontaktgefrieren und Depositionsnukleation werden in der AIDA-Wolkenkammer und einer neuen dynamischen Wolkenkammer durchgeführt, falls diese wie geplant bis Anfang 2016 zur Verfügung stehen wird. Hauptziele und Arbeitspakete des Projekts sind (a) Untersuchungen zum Immersionsgefrieren, Kontaktgefrieren und zur Depositionsnukleation von INUIT-2 Referenzaerosolen in enger Zusammenarbeit mit allen anderen lNUlT-2-Partnern, (b) AIDA-Wolkensimulationsexperimente mit redispergierten atmosphärischen Aerosolen die auf Filtern gesammelt wurden (in Zusammenarbeit mit RP8), (c) AIDA-Experimente mit porösen Partikeln zur Untersuchung des Einflusses von Kapillarkondensation und Prä-aktivierung auf Eisnukleationsprozesse, (d) EDB-Experimente zur Kontaktnukleation mit atmosphärisch relevanten und komplexen Aerosolen, (e) Untersuchungen zu den grundlegenden Mechanismen des Kontaktgefrierens, (f) die Entwicklung einer umfassenden und einheitlichen Parametrisierung heterogener Eisnukleation in enger Zusammenarbeit mit RP3 und RP5, (g) erste Experimente zur Kontaktnukleation in einer neuen Wolkenkammer unter Nutzung der Expertise aus langjährigen Experimenten zum Kontaktgefrieren und mit der Wolkensimulationskammer, (h) die Durchführung von zwei AIDA-Messkampagnen, eine nur für die INUIT-2- Partner und eine mit internationaler Beteiligung, bei denen Labormethoden und Feld Instrumente für die Messung von Aerosolen und eisbildenden Partikeln getestet und miteinander verglichen werden um hohe internationale Standards in der Eisnukleationsforschung zu entwickeln und zu erhalten. Die Aktivitäten an der AIDA-Wolkenkammer bieten auch eine gute Verknüpfung der Labor-, Feld und Modellieraktivitäten innerhalb der Forschergruppe INUIT und mit externen Partnern. In Ergänzung der laufenden INUIT-Arbeiten möchten wir in weiteren drei Jahren der Forschergruppe folgende neue Schwerpunkte setzen: die Eisnukleationseigenschaften von porösen Partikeln, Immersionsgefrieren und Depositionsnukleation von größenselektierten Partikeln mit Durchmessern bis zu einigen Mikrometern, die Quantifizierung von Kontaktgefrierraten von atmosphärisch relevanten komplexen Aerosolpartikeln, und erste Wolkenkammerexperimente zum Kontaktgefrieren. Außerdem werden wir die Erstellung und Pflege einer neuen Datenbank für Laborergebnisse zur heterogenen Eisnukleation unterstützen.
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