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.
Mikroplastik wird zwischen Land- und Wasseroberflächen und der Atmosphäre ausgetauscht und kann luftgetragen über weite Strecken transportiert werden, bevor die Mikroplastikpartikel wieder aus der Atmosphäre entfernt und abgelagert werden. Obwohl diese Transportprozesse für die Verteilung und die wirksamen Abbaumechanismen von Mikroplastik sehr wichtig sind, gibt es bislang keine systematischen Untersuchungen zum atmosphärischen Transport von Mikroplastik. Der luftgetragene Transport von Mikroplastik wird im vorliegenden Teilprojekt in einem Windkanal als idealisiertem Modellsystem experimentell untersucht und mit einem strömungsauflösenden Transportmodell numerisch simuliert, um die grundlegenden Prozesse verstehen und quantifizieren zu können.
Soil microorganisms can mobilize and immobilize phosphorus (P), and therefore strongly affect the availability of P to plants. In this project we hypothesize that the ratio of labile P to microbial P increases during the transition from acquiring to recycling ecosystems. Microbial and plant P uptake will be studied with 33P that will be quantified in microbial and plant biomass as well as in lipids. To what extent microorganisms immobilize and mobilize P during decomposition of soil organic matter will be explored with a 14C/33P labeled monoester. Seasonal dynamics of actual and potential P mineralization (33P dilution and phosphatase activity), and microbial P immobilization will be studied with soils of the transition from acquiring to recycling ecosystems. The contribution of litter-derived P will be explored in a litter exclusion experiment in the field. Spatial patterns of microbial and plant P mineralization in the rhizosphere will be explored by analyses of areas of high acid and alkaline (=microbial-derived) phosphatase activity by soil zymography, and their relations with areas of high rhizodeposition (14C imaging). In conclusion, we will analyse mechanisms of actual and potential microbial P mineralization and immobilization, localization, and consequences for P uptake by plants.
Die Nukleation von Eispartikeln spielt eine wichtige Rolle bei der Wolken- und Niederschlagsbildung, mit Konsequenten für die atmosphärische Chemie, die Wolkenphysik und das Erdklima. Für eine Quantifizierung und Vorhersage des Einflusses von Wolken in Wettervorhersage- und Klimamodellen muss die Bildung von Eispartikeln daher in einer realistischen Art und Weise beschrieben werden. Einer der wichtigen Bildungsmechanismen ist dabei die heterogene Eisnukleation im Immersionsmodus, bei dem Eis an der Oberfläche eines in einem wässrigen Tröpfchen suspendierten Eiskeims - zum Beispiel eines Mineralstaub- Partikels - gebildet wird. Wir werden im Rahmen dieses Forschungsprojekts zahlreiche Gefrierexperimente im Immersionsmodus durchführen. So werden eine Reihe verschiedener, als Aerosolpartikel in der Atmosphäre vorkommende Materialien auf ihre Eisnukleationseigenschaften hin untersucht werden. Insbesondere sollen hier die Temperatur- und Zeitabhängigkeit der von diesen Materialien ausgelösten Eisnukleation quantifiziert werden. Dabei werden wir spezielles Augenmerk auf die systematische Untersuchung der von porösen Materialien ausgelösten Eisnukleation legen. Es sollen sowohl synthetische Materialien wie beispielsweise mesoporöse Silikate untersucht werden, als auch natürlich vorkommende Materialien wie etwa mikroporöse Zeolithe.
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.
B06 untersucht im SFB 1357 den Transport von chemisch komplexen und realitätsnahen Mikroplastik (MP)-Partikeln auf Bodenoberflächen und im Boden durch Wasser und Bioturbation in natürlichen gestörten und ungestörten Böden. Das Projekt liefert dadurch essenzielle Daten für ein Verständnis der Transport- und Akkumulationsmechanismen von unterschiedlichen umweltrelevanten Sorten von MP-Partikeln. Die Erkenntnisse zu potenziellen Akkumulationsbereichen und somit zur Expositionswahrscheinlichkeit für Organismen bilden die Grundlage für eine realitätsnahe ökologische Risikobewertung.
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.
Cherry leaf roll virus (CLRV) is a plant pathogen of economic and ecologic importance. It is globally distributed in a wide range of forest, fruit, and ornamental trees and shrubs. In several areas of cherry and walnut production CLRV causes severe losses in yield and quality. With current reference to the rapid dissemination and strong symptom expression in Finnish birches and the Germany-wide distribution of CLRV in birches and elderberry, we continuously investigate and gradually reveal CLRV transmission pathways as by pollen, seeds or water. However, modes and interactions responsible for the wide intergeneric host transmission as well as for the exceptional CLRV epidemic in Fennoscandia still remain unknown. In this project systematic studies shall investigate biological vectors as a causal agent to finally derive control mechanisms and strategies to avoid new epidemics in different hosts and geographic regions. Detailed monitoring of the invertebrate fauna of birch stands/forests and elderberry plantations in Germany and Finland shall reveal potential vectors to subsequently study them in detail by approved virus detection methods and transmission experiments. Molecular analyses of the CLRV coat protein shall prove its role as a viral determinant for a virus/vector interaction. Consequently, this project essentially will contribute important answers on the CLRV epidemiology, and this will be a key element within the first network of research on plant viral pathogens in forest trees.
Changes in agroecosystem management (e.g. landscape diversity, management intensity) affect the natural control of pests. The effects of agricultural change on this ecosystem service, however, are not universal and the mechanisms affecting it remain to be understood. As biological control is effectively the product of networks of interactions between pests and their natural enemies, food web analysis provides a versatile tool to address this gap of knowledge. The proposed project will utilize a molecular food web approach and examine, for the first time, how changes in plant fertilisation and landscape complexity affect quantitative aphid-parasitoid-hyperparasitoid food webs on a species-specific level to unravel how changes in food web interactions affect parasitoid aphid control. Based on the fieldderived data, cage experiments will be conducted to assess how parasitoid diversity and identity affect parasitoid interactions and pest control, complementing the field results. The work proposed here will take research on parasitoid aphid control one step further, as it will provide a clearer understanding of how plant fertilization affects whole aphid-parasitoid food webs in both simple and complex landscapes, allowing for further improvements in natural pest control.
Deviant behaviour on various levels of the food supply chain may cause food risks. It entails irregular technological procedures which cause (increased probabilities of) adverse outcomes for buyers and consumers. Besides technological hazards and hitherto unknown health threats, moral hazard and malpractice in food businesses represent an additional source of risk which can be termed 'behavioural food risk'. From a regulatory perspective, adverse outcomes associated with deviance represent negative externalities that are caused by the breaking of rules designed to prevent them. From a rational choice perspective, the probability of malpractice increases with the benefits for its authors. It decreases with the probability of detection and resulting losses. It also decreases with bonds to social norms that protect producers from yielding to economic temptations. The design of mechanisms that reduce behavioural risks and prevent malpractice requires an understanding of why food businesses obey or do not obey the rules. This project aims to contribute to a better understanding of malpractice on the restaurant/retail level through comparative case studies and statistical analyses of food inspection and survey data. Accounting for the complexity of economic behaviour, we will not only look at economic incentives but consider all relevant behavioural determinants, including social context factors.
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