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- Fachbereich 7 (93) (remove)
A fundamental understanding of attachment of engineered nanoparticles to environmentalrnsurfaces is essential for the prediction of nanoparticle fate and transport in the environment.
The present work investigates the attachment of non-coated silver nanoparticles and citraterncoated silver nanoparticles to different model surfaces and environmental surfaces in thernpresence and absence of humic acid. Batch sorption experiments were used for this investigation.
The objective of this thesis was to investigate how silver nanoparticles interactrnwith surfaces having different chemical functional groups. The effect of presence of HA, on the particle-surface interactions was also investigated. In the absence of humic acid, nanoparticle-surface interactions or attachment was influencedrnby the chemical nature of the interacting surfaces. On the other hand, in the presence ofrnhumic acid, nanoparticle-surface attachment was influenced by the specific surface area of the sorbent surfaces. The sorption of non-coated silver nanoparticles and citrate coatedrnnanoparticles to all the surfaces was nonlinear and best described by Langmuir isotherm, indicating monolayer sorption of nanoparticles on to the surfaces. This can be explained as due to the blocking effect generated by the particle-particle repulsion. In the presence of humic acid, sorption of nanoparticles to the surfaces was linear. When the humic acid was present in the interacting medium, both the nanoparticles and surfaces were getting coated with humic acid and this masks the chemical functionalities of the surfaces. This leads to the change in particle-surface interactions, in the presence of humic acid. For the silver nanoparticle sorption from an unstable suspension, the sorption isotherms did not follow any classical sorption models, suggesting interplay between aggregation and sorption. Citrate coated silver nanoparticles and humic acid coated silver nanoparticles showed arndepression in sorption compared to the sorption of non-coated silver nanoparticles. In therncase of citrate coated silver nanoparticles the decrease in sorption can be explained by thernmore negative zeta potential of citrate coated nanoparticles compared to non-coated ones. For humic acid coated nanoparticles the sorption depression can be due to the steric hindrance caused by the free humic acid molecules which may coat the sorbent surface or due to the competition for sorption sites between the nanoparticle and free humic acid molecules present in the suspension. Thus nanoparticle surface chemistry is an important factor that determines the attachment of nanoparticles towards surfaces and it makes the characterization of nanoparticle surface an essential step in the study of their fate in the environment.
Another aim of this study was to introduce the potential of chemical force microscopy for nanoparticle surface characterization. With the use of this technique, it was possible to distinguish between bare silver nanoparticles, citrate coated silver nanoparticles, and humic acid coated silver nanoparticles. This was possible by measuring the adhesion forces between the nanoparticles and five different AFM probes having different chemical functionalization.
Vertebrate biodiversity is rapidly decreasing worldwide with amphibians being the most endangered vertebrate group. In the EU, 21 of 89 amphibian species are recognized as being endangered. The intensively used European agricultural landscape is one of the major causes for these declines. As agriculture represents an essential habitat for amphibians, exposure to pesticides can have adverse effects on amphibian populations. Currently, the European risk assessment of pesticides for vertebrates requires specific approaches for fish regarding aquatic vertebrate toxicity and birds as well as mammals for terrestrial vertebrate toxicity but does not address the unique characteristics of amphibians. Therefore, the overall goal of this thesis was to investigate the ecotoxicological effects of pesticides on Central European anuran amphibians. For this, effects on aquatic and terrestrial amphibian life stages as well as on reproduction were investigated. Then, in anticipation of a risk assessment of pesticides for amphibians, this thesis discussed potential regulatory risk assessment approaches.
For the investigated pesticides and amphibian species, it was observed that the acute aquatic toxicity of pesticides can be addressed using the existing aquatic risk assessment approach based on fish toxicity data. However, lethal as well as sublethal effects were observed in terrestrial juveniles after dermal exposure to environmentally realistic pesticide concentrations, which cannot be covered using an existing risk assessment approach. Therefore, pesticides should also be evaluated for potential terrestrial toxicity using risk assessment tools before approval. Additionally, effects of co-formulants and adjuvants of pesticides need specific consideration in a future risk assessment as they can increase toxicity of pesticides to aquatic and terrestrial amphibian stages. The chronic duration of combined aquatic and terrestrial exposure was shown to affect amphibian reproduction. Currently, such effects cannot be captured by the existing risk assessment as data involving field scenarios analysing effects of multiple pesticides on amphibian reproduction are too rare to allow comparison to data of other terrestrial vertebrates such as birds and mammals. In the light of these findings, future research should not only address acute and lethal effects, but also chronic and sublethal effects on a population level. As pesticide exposure can adversely affect amphibian populations, their application should be considered even more carefully to avoid further amphibian declines. Overall, this thesis emphasizes the urgent need for a protective pesticide risk assessment for amphibians to preserve and promote stable amphibian populations in agricultural landscapes.
The bio-insecticide Bacillus thuringiensis israelensis (Bti) has worldwide become the most commonly used agentin mosquito control programs that pursue two main objectives: the control of vector-borne diseases and the reduction of nuisance, mainly coming frommosquitoes that emerge in large quantities from seasonal wetlands. The Upper Rhine Valley, a biodiversity hotspot in Germany, has been treated withBti for decades to reduce mosquito-borne nuisance and increase human well-being.Although Btiis presumed to be an environmentally safe agent,adverse effects on wetland ecosystems are still a matter of debate especially when it comes to long-term and indirect effects on non-target organisms. In light of the above, this thesis aims at investigating direct and indirect effects of Bti-based mosquito control on non-target organisms within wetland food chains.Effects were examinedin studies with increasingeco(toxico)logical complexity, ranging from laboratory over mesocosm to field approaches with a focus on the non-biting Chironomidae and amphibian larvae (Rana temporaria, Lissotriton sp.).In addition, public acceptance of environmentally less invasive alternative mosquito control methods was evaluated within surveys among the local population.
Chironomids were the most severely affected non-target aquatic invertebrates. Bti substantially reduced larval and adult chironomid abundances and modified their species composition. Repeated exposures to commonly used Bti formulations induced sublethal alterations of enzymatic biomarkers activityin frog tadpoles. Bti-induced reductions of chironomid prey availability indirectly decreased body size of newts at metamorphosis and increased predation on newt larvae in mesocosm experiments. Indirect effects of severe reductions in midge biomassmight equally be passed through aquatic but also terrestrial food chains influencing predators of higher trophic levels. The majority ofaffectedpeople in the Upper Rhine Valley expressed a high willingness to contributefinancially to environmentally less harmful mosquito control.Alternative approaches could still include Bti applications excepting treatment of ecologically valuable areas. Potentially rising mosquito levels could be counteracted with local acting mosquito traps in domestic and urban areas because mosquito presence was experienced as most annoying in the home environment.
As Bti-based mosquito control can adversely affect wetland ecosystems, its large-scale applications, including nature conservation areas, should be considered more carefully to avoid harmful consequences for the environmentat the Upper Rhine Valley.This thesis emphasizesthe importance to reconsiderthe current practice of mosquito control and encourage research on alternative mosquito control concepts that are endorsed by the local population. In the context ofthe ongoing amphibian and insect declinesfurther human-induced effects onwetlands should be avoided to preserve biodiversity in functioning ecosystems.
Recent estimates have confirmed that inland waters emit a considerable amount of CH4 and CO2 to the atmosphere at the regional and global scale. But these estimates are based on extrapolated measured data and lack of data from inland waters in arid and semi-arid regions and carbon sources from wastewater treatment plants (WWTPs) as well insufficient resolution of the spatiotemporal variability of these emissions.
Through this study, we analyzed monthly hydrological, meteorological and water quality data from three irrigation and drinking water reservoirs in the lower Jordan River basin and estimated the atmospheric emission rates of CO2. We investigated the effect of WWTPs on surrounding aquatic systems in term of CH4 and CO2 emission by presenting seasonally resolved data for dissolved concentrations of both gases in the effluents and in the receiving streams at nine WWTPs in Germany.
We investigated spatiotemporal variability of CH4 and CO2 emission from aquatic ecosystems by using of simple low-cost tools for measuring CO2 flux and bubble release rate from freshwater systems. Our estimates showed that reservoirs in semi-arid regions are oversaturated with CO2 and acted as net sources to the atmosphere. The magnitude of observed fluxes at the three water reservoirs in Jordan is comparable to those from tropical reservoirs (3.3 g CO2 m-2 d-1). The CO2 emission rate from these reservoirs is linked to changes of water surface area, which is the result of water management practices. WWTPs have been shown to discharge a considerable amount of CH4 (30.9±40.7 kg yr-1) and CO2 (0.06±0.05 Gg yr-1) to their surrounding streams, and emission rates of CH4 and CO2 from these streams are significantly enhanced by effluents of WWTPs up to 1.2 and 8.6 times, respectively.
Our results showed that both diffusive flux and bubble release rate varied in time and space, and both of emission pathways should be included and variability should be resolved adequately in further sampling and measuring strategies. We conclude that future emission measurements and estimates from inland waters may consider water management practices, carbon sources from WWTPs as well spatial and temporal variability of emission.
For decades a worldwide decline of biological diversity has been reported. Landscapes are influenced by several kinds of anthropogenic disturbances. Agricultural land use, application of fertilizers and pesticides and the removal of corridors simplify and homogenize a landscape whereas others like road constructions lead to fragmentation. Both kinds lead to a constraint of habitats, reduce living environment and gene pool, hinder gene flow and change the functional characteristics of species. Furthermore, it facilitates the introduction of alien species. On the other hand, disturbances of different temporal and spatial dimensions lead to a more diverse landscape because they prevent competitive exclusion and create niches where species are able to coexist.
This study focuses on the complexity of disturbance regimes and its influence on phytodiversity. It differs from other studies that mostly select one or few disturbance types in including all identifiable disturbances. Data were derived from three study sites in the north of Bavaria and are subject to different land-use intensities. Two landscapes underlie agriculture and forestry, of which one is intensively used and the second one rather moderate and small-scaled. The third dataset was collected on an actively used military training area. The first part of the study deals with the influence of disturbance regimes on phytodiversity, first with the focus on military disturbances, afterwards in comparison with the agricultural landscapes. The second part examines the influence of disturbance regimes on red-listed species, the distribution of neophytes and generalist plant species and the homogenization of the landscape. All analyses were conducted on landscape and local scale.
A decisive role was played by the variety of disturbance types, especially in different temporal and spatial dimensions and not by single kinds of disturbances, which significantly was proven in the military training area with its multiple and undirected disturbance regime. Homogeneous disturbance regimes that typically are found in agricultural landscapes led to a reduced species number. On local scale, the abiotic heterogeneity which originated of recent and historical disturbances superimposed the positive effects of disturbance regimes, whereas dry and nutrient-poor sites showed a negative effect. Due to a low tree density and moderate treatment species numbers were significantly higher in forest in the training area than in the two agricultural landscapes.
Numbers of red-listed species were positively correlated to the total number of species in all three sites. However, the military training area showed a significantly higher abundance within the area in comparison to the agricultural landscapes where rare species were mostly found on marginal strips. Furthermore, numbers of neophytes and generalist species were lower and consequently homogenization.
In conclusion, the military training area is an ideal landscape from a nature conservation point of view. The moderately used agricultural area showed high species numbers and agricultural productivity. However, yield is too low to withstand either abandonment or land-use intensification.
The role of alternative resources for pollinators and aphid predators in agricultural landscapes
(2021)
The world wide decline of insects is often associated with loss of natural and semi-natural habitat caused by intensified land-use. Many insects provide important ecosystem services to agriculture, such as pest control or pollination. To efficiently promote insects on remaining semi-natural habitat we need precise knowledge of their requirements to non-crop habitat. This thesis focuses on identifying
the most important semi-natural habitats (forest edges, grasslands, and semi-open habitats) for pollinators and natural enemies of crop pests with respect to their food resource requirements. Special
attention is given to floral resources and their spatio-temporal distribution in agricultural landscapes.
Floral resource maps might get closer at characterizing landscapes the way they are experienced by insects compared to classical habitat maps. Performance of the two map types was compared on the prediction of wild bees and natural enemies that consume nectar and pollen, identifying habitats of special importance in the process. In wild bees, influences of spatio-temporal floral resource availability were analysed as well as habitat preferences of specific groups of bees. Understanding dietary needs of natural enemies of crop pests requires additional knowledge on prey use. To this end, ladybird gut contents have been analysed by means of high-throughput sequencing for insight into aphid prey-use.
Results showed, that wild bees were predicted better by floral resource maps compared to classical habitat maps. Forest edge area, as well as floral resources in forest edges had positive effects on abundance and diversity of rare bees and important crop pollinators. Similar patterns were retained for grassland diversity. Especially early floral resources seemed to have positive effects on wild bees. Crops and fruit trees produced a resource pulse in April that exceeded floral resource availability in May and June by tenfold. Most floral resources in forest edges appeared early in the season, with the highest floral density per area. Grasslands provided the lowest amount of floral resources but highest diversity, which was evenly distributed over the season.
Despite natural enemies need for floral resources, classical habitat maps performed better at predicting natural enemies of crop pests compared to floral resource maps. Classical habitat maps revealed a positive effect of forest edge habitat on the abundance of pest enemies, which translated into improved aphid control. Results from gut content analysis reveal high portions of pest aphid species and nettle aphids as well as a broader insight into prey spectra retained from ladybirds collected from sticky traps compared to individuals collected by hand. The aphid specific primer designed for this purpose will be helpful for identifying aphid consumption by ladybirds in future studies.
Findings of this thesis show the potential of floral resource maps for understanding interactions of wild bees and the landscape but also indicate that natural enemies are limited by other resources. I would like to highlight the positive effects of forest edges for different groups of bees as well as natural enemies and their performance on pest control.
Während es eine Vielzahl von Arbeiten zu der technologischen Entwicklung im Bereich der erneuerbaren Energien gibt, fehlt es jedoch bislang an einer mikroökonomischen Analyse
der Verhaltensmuster der Akteure im Umfeld von Anlagen nach dem EEG. Als Akteure kommen hier in erster Linie der Anlagenbetreiber selbst und der Staat in Betracht.
Im Hinblick auf Anlagenbetrieb und Vergütung der erzeugten Energie können beide mit unterschiedlichsten Interessen und Nutzenkalkülen aufeinander treffen. Diese Arbeit untersucht
mikroökonomische Aspekte des EEG-Förderungssystems. Im Mittelpunkt der Betrachtung stehen die Förderungsmechanismen für Biogasanlagen, die im Hinblick auf mögliche Prinzipal-Agenten-Konflikte einer Untersuchung unterzogen werden.
Fate and effects of insecticides in vegetated agricultural drainage ditches and constructed wetlands
(2006)
Studies have shown that runoff and spray-drift are important sources of nonpoint-source pesticide pollution of surface waters. Owing to this, public concern over the presence of pesticides in surface and ground water has resulted in intensive scientific efforts to find economical, yet environmentally sound solutions to the problem. The primary objective of this research was to assess the effectiveness of vegetated aquatic systems in providing buffering between natural aquatic ecosystems and agricultural landscape following insecticide associated runoff and spray-drift events. The first set of studies were implemented using vegetated agricultural ditches, one in Mississippi, USA, using pyrethroids (bifenthrin, lambda-cyhalothrin) under simulated runoff conditions and the other in the Western Cape, South Africa using the organophosphate insecticide, azinphos-methyl (AZP), under natural runoff and spray-drift conditions. The second set of studies were implemented using constructed wetlands, one in the Western Cape using AZP under natural spray-drift conditions and the other in Mississippi, USA using the organophosphate MeP under simulated runoff conditions. Results from the Mississippi-ditch study indicated that ditch lengths of less than 300 m would be sufficient to mitigate bifenthrin and lambda-cyhalothrin. In addition, data from mass balance calculations determined that the ditch plants were the major sink (generally > 90%) and/or sorption site for the rapid dissipation of the above pyrethroids from the water column. Similarly, results from the ditch study in South Africa showed that a 180 m vegetated system was effective in mitigating AZP after natural spray drift and low flow runoff events. Analytical results from the first wetland study show that the vegetated wetland was more effective than the non-vegetated wetland in reducing loadings of MeP. Mass balance calculations indicated approximately 90% of MeP mass was associated with the plant compartment. Ninety-six hours after the contamination, a significant negative acute effect of contamination on abundances was found in 8 out of the 15 macroinvertebrate species in both wetland systems. Even with these toxic effects, the overall reaction of macroinvertebrates clearly demonstrated that the impact of MeP in the vegetated wetland was considerably lower than in the non-vegetated wetland. Results from the constructed wetland study in South Africa revealed that concentrations of AZP at the inlet of the 134 m wetland system were reduced by 90% at the outlet. Overall, results from all of the studies in this thesis indicate that the presence of the plant compartment was essential for the effective mitigation of insecticide contamination introduced after both simulated and natural runoff or spray-drift events. Finally, both the vegetated agricultural drainage ditch and vegetated constructed wetland systems studied would be effective in mitigating pesticide loadings introduced from either runoff or spray-drift, in turn lowering or eliminating potential pesticide associated toxic effects in receiving aquatic ecosystems. Data produced in this research provide important information to reduce insecticide risk in exposure assessment scenarios. It should be noted that incorporating these types of best management practices (BMPs) will decrease the risk of acute toxicity, but chronic exposure may still be an apparent overall risk.
The transport of pesticides from agricultural land into surface waters via diffuse entry pathways such as runoff is a major threat to aquatic ecosystems and their communities. Although certain risk mitigation measures are currently stipulated during pesticide product authorisation, further approaches might be needed to manage hot spots of pesticide exposure. Such a management is, for example, required by the European Union- directive for the sustainable use pesticides (2009/128/EC).
The need for mitigation measures was investigated within the present thesis at stream sites draining an arable and a vineyard region in Germany by characterising pesticide exposure following edge-of-field runoff and (expected) effects on the aquatic macroinvertebrates. The results of these field studies showed, that streams in both regions were exposed to pesticide concentrations suggesting effects on the macroinvertebrate community. In the arable region the observed toxicity was mainly attributed to the insecticides lambda-cyhalothrin (in the water-phase samples) and alpha-cypermethrin (in the suspended particle samples), whereas in the vineyard region fungicides were most important. Furthermore stream water and suspended particles sampled in the vineyard region showed critical copper concentrations, which might cause ecotoxicological effects in the field. In addition to pesticide exposure, in the arable region also the effects on aquatic macroinvertebrates were assessed in the field. Generally, invertebrate fauna was dominated by pesticide-tolerant species, which suggested a high pesticide exposure at almost all sites. The elevated levels of suspended particle contamination in terms of maximum toxic units per sample (logTUMax > -2) reflect also this result. At two sites that received high aqueous-phase entries of the insecticide lambda-cyhalothrin (logTUMax > -0.6), the abundance and number of sensitive species (indicated by the SPEcies At Risk index) decreased during the pesticide application period. In contrast, at sites characterised by low water-phase toxicity (logTUMax < -3.5), no acute significant negative effects on macroinvertebrates were observed. In conclusion these data showed that in both regions the implementation of risk mitigation measures is needed to protect the aquatic communities.
To mitigate runoff-related pesticide entries, riparian buffer strips are often recommended. However, the mitigating influence with increasing buffer strip width could not be demonstrated for riparian buffers which were already present in the arable and vineyard region. This result was attributed in the vineyard region to the high number of paved field paths associated with artificial erosion rills, which concentrate and rapidly transport receiving edge-of-field runoff in stream direction. Consequently the pesticide reduction efficiency of buffer strips is considerably reduced. We assumed that a similar process occurred in the arable region, due to a high number of erosion rills, which complicate a laminar sheet flow of edge-of-field runoff through the riparian buffer strip. Additionally also the presence of ephemeral drainage ditches, which led surface runoff from the agricultural fields to the streams may have contributed to observed pesticide entries despite wide buffers.
Effective risk mitigation measures should address these identified most important input pathways in the study areas. As possible measures the implementation of grassed field paths and vegetated ditches or wetlands were suggested. In general also the improvement of currently present riparian buffer strips regarding their efficiency to reduce pesticide runoff entries should be taken into account. In conclusion the results of the field studies underline the importance that risk mitigation measures are identified specifically for the respective pollution situation in stream catchments. To facilitate this process, a user guide was developed within the present thesis for identifying appropriate mitigation measures at high-risk sites. Based on a survey of exposure relevant landscape parameter a set of risk mitigation measures is suggested that focus on the specific pollution situation. Currently the guide includes 12 landscape- and six application-related measures and presents an overview of these measures" efficiency to reduce pesticide entries via runoff and spray drift, their feasibility and expected acceptability to farmers. Based on this information the user can finally choose the mitigation measures for implementation. The present guide promotes the practical implementation of appropriate risk mitigation measures in pesticide-polluted streams, and thus the protection of aquatic stream communities against pesticide entries.
In the new epoch of Anthropocene, global freshwater resources are experiencing extensive degradation from a multitude of stressors. Consequently, freshwater ecosystems are threatened by a considerable loss of biodiversity as well as substantial decrease in adequate and secured freshwater supply for human usage, not only on local scales, but also on regional to global scales. Large scale assessments of human and ecological impacts of freshwater degradation enable an integrated freshwater management as well as complement small scale approaches. Geographic information systems (GIS) and spatial statistics (SS) have shown considerable potential in ecological and ecotoxicological research to quantify stressor impacts on humans and ecological entitles, and disentangle the relationships between drivers and ecological entities on large scales through an integrated spatial-ecological approach. However, integration of GIS and SS with ecological and ecotoxicological models are scarce and hence the large scale spatial picture of the extent and magnitude of freshwater stressors as well as their human and ecological impacts is still opaque. This Ph.D. thesis contributes novel GIS and SS tools as well as adapts and advances available spatial models and integrates them with ecological models to enable large scale human and ecological impacts identification from freshwater degradation. The main aim was to identify and quantify the effects of stressors, i.e climate change and trace metals, on the freshwater assemblage structure and trait composition, and human health, respectively, on large scales, i.e. European and Asian freshwater networks. The thesis starts with an introduction to the conceptual framework and objectives (chapter 1). It proceeds with outlining two novel open-source algorithms for quantification of the magnitude and effects of catchment scale stressors (chapter 2). The algorithms, i.e. jointly called ATRIC, automatically select an accumulation threshold for stream network extraction from digital elevation models (DEM) by assuring the highest concordance between DEM-derived and traditionally mapped stream networks. Moreover, they delineate catchments and upstream riparian corridors for given stream sampling points after snapping them to the DEM-derived stream network. ATRIC showed similar or better performance than the available comparable algorithms, and is capable of processing large scale datasets. It enables an integrated and transboundary management of freshwater resources by quantifying the magnitude of effects of catchment scale stressors. Spatially shifting temporal points (SSTP), outlined in chapter 3, estimates pooled within-time series (PTS) variograms by spatializing temporal data points and shifting them. Data were pooled by ensuring consistency of spatial structure and temporal stationarity within a time series, while pooling sufficient number of data points and increasing data density for a reliable variogram estimation. SSTP estimated PTS variograms showed higher precision than the available method. The method enables regional scale stressors quantification by filling spatial data gaps integrating temporal information in data scarce regions. In chapter 4, responses of the assumed climate-associated traits from six grouping features to 35 bioclimatic indices for five insect orders were compared, their potential for changing distribution pattern under future climate change was evaluated and the most influential climatic aspects were identified (chapter 4). Traits of temperature preference grouping feature and the insect order Ephemeroptera exhibited the strongest response to climate as well as the highest potential for changing distribution pattern, while seasonal radiation and moisture were the most influential climatic aspects that may drive a change in insect distribution pattern. The results contribute to the trait based freshwater monitoring and change prediction. In chapter 5, the concentrations of 10 trace metals in the drinking water sources were predicted and were compared with guideline values. In more than 53% of the total area of Pakistan, inhabited by more than 74 million people, the drinking water was predicted to be at risk from multiple trace metal contamination. The results inform freshwater management by identifying potential hot spots. The last chapter (6) synthesizes the results and provides a comprehensive discussion on the four studies and on their relevance for freshwater resources conservation and management.
Abdriftbedingte Pflanzenschutzmittelrückstände in unbehandelten Kulturen auf angrenzenden Flächen
(2020)
Die vorliegende Arbeit beschäftigt sich mit der Abdrift von Pflanzenschutzmitteln (PSM), die auf Lebensmittelkulturen in angrenzenden Flächen, insbesondere in benachbarte Haus- und Kleingärten, gelangt. In einer Reihe von Windtunnelversuchen wurde die Abdrift von PSM aus Flächen- und Raumkulturen während der Applikation mit zwei verschiedenen Testsystemen nachgestellt. Das Testsystem Flächenkultur simuliert die Applikation auf Flächenkulturen, das Testsystem Raumkultur die auf Raumkulturen. Auf der Nicht-Zielfläche wurden die auf Grund von Abdrift entstandenen Rückstände des verwendeten Tracers Pyranin nach der Applikation entfernungsabhängig auf den Lebensmittelkulturen Kopfsalat, Erdbeeren und Tomaten gemessen. Durch die gleichzeitige Messung der Bodendeposition konnten die Messwerte mit Hilfe von Regressionsgleichungen (R² = 0,88 bis 0,97) in Bezug zu den Abdrifteckwerten (AEW) gebracht werden. Dadurch war es möglich, erste Abschätzungen der Höhe von Rückständen vorzunehmen, die über Abdrift von landwirtschaftlichen Flächen auf benachbarte Lebensmittelkulturen im Freiland gelangen können. Diese Abschätzung ist zunächst limitiert auf die drei Versuchspflanzen. Die Versuche zeigen, dass sich die meisten durch Abdrift entstehenden Rückstände auf Salatköpfen wieder finden, gefolgt von Erdbeeren und Tomaten.
Neben dem experimentellen Teil wurden Analysen mit Geoinformationssystemen (GIS) durchgeführt, um die Nachbarschaftsverhältnisse zwischen landwirtschaftlich genutzten Flächen und Gartenflächen für ganz Deutschland und speziell für Rheinland-Pfalz (RLP) zu analysieren. Dazu wurden für die deutschlandweiten Berechnungen die Daten des amtlichen topographisch-kartographischen Informationssystems (ATKIS) und für die RLP-weiten Berechnungen die Daten des amtlichen Liegenschaftskatasterinformationssystem (ALKIS) verwendet. Beachtet werden muss, dass auf Grund der Datenbeschaffenheit eine Abgrenzung der Gartenflächen zu Wohnflächen nicht möglich ist. Deutschlandweit liegen etwa 1,1 % aller potentiellen Gartenflächen innerhalb eines 5 m Pufferbereichs um Raumkulturen bzw. innerhalb eines 2 m Pufferbereichs um Flächenkulturen. Für RLP sind es 0,75 %. Mit Hilfe eines Landbedeckungsdatensatzes der Fa. RLP AgroScience GmbH und den ALKIS-Daten konnte jedoch die exakte Gartenfläche für RLP auf 47.437 ha bestimmt werden. Basierend auf dieser Datengrundlage liegen 1,2 % der Gartenfläche von RLP innerhalb der genannten Pufferbereiche. Des Weiteren ergaben Berechnungen, dass 3 % der Gärten in RLP direkt angrenzend zu landwirtschaftlich genutzten Flächen liegen.
Im Rahmen dieser Arbeit wurden nicht nur Gärten betrachtet, die an landwirtschaftliche Flächen grenzen, sondern auch Nachbarschaftsverhältnisse zwischen ökologisch und konventionell bewirtschafteten Flächen untersucht. Diese Berechnungen erfolgten mit den Daten des Integrierten Verwaltungs- und Kontrollsystems (InVeKoS). Insgesamt grenzen in RLP 47,1 % aller ökologisch bewirtschafteten Flächen unmittelbar an konventionell bewirtschaftete Flächen an.
Gel effect induced by mucilage in the pore space and consequences on soil physical properties
(2020)
Water uptake, respiration and exudation are some of the biological functions fulfilled by plant roots. They drive plant growth and alter the biogeochemical parameters of soil in the vicinity of roots, the rhizosphere. As a result, soil processes such as water fluxes, carbon and nitrogen exchanges or microbial activity are enhanced in the rhizosphere in comparison to the bulk soil. In particularly, the exudation of mucilage as a gel-like substance by plant roots seems to be a strategy for plants to overcome drought stress by increasing soil water content and soil unsaturated hydraulic conductivity at negative water potentials. Although the variations of soil properties due to mucilage are increasingly understood, a comprehensive understanding of the mechanisms in the pore space leading to such variations is lacking.
The aim of this work was to elucidate the gel properties of mucilage in the pore space, i.e. interparticulate mucilage, in order to link changes of the physico-chemical properties in the rhizosphere to mucilage. The fulfilment of this goal was confronted to the three following challenges: The lack of methods for in situ detection of mucilage in soil; The lack of knowledge concerning the properties of interparticulate mucilage; The unknown relationship between the composition and the properties of model substances and root mucilage produced by various species. These challenges are addressed in several chapters.
In a first instance, a literature review picked information from various scientific fields about methods enabling the characterization of gels and gel phases in soil. The variation of soil properties resulting from biohydrogel swelling in soil was named the gel effect. The combined study of water entrapment of gels and gel phases in soil and soil structural properties in terms of mechanical stability or visual structures proved promising to disentangle the gel effect in soil.
The acquired methodical knowledge was used in the next experiments to detect and characterize the properties of interparticulate gel. 1H NMR relaxometry allows the non-invasive measure of water mobility in porous media. A conceptual model based on the equations describing the relaxation of water protons in porous media was developed to integrate the several gel effects into the NMR parameters and quantify the influence of mucilage on proton relaxation. Rheometry was additionally used to assess mucilage viscosity and soil microstructural stability and ESEM images to visualize the network of interparticulate gel. Combination of the results enabled to identify three main interparticulate gel properties: The spider-web effect restricts the elongation of the polymer chains due to the grip of the polymer network to the surface of soil particles. The polymer network effect illustrates the organization of the polymer network in the pore space according to the environment. The microviscosity effect describes the increased viscosity of interparticulate gel in contrast to free gel. The impact of these properties on soil water mobility and microstructural stability were investigated. Consequences on soil hydraulic and soil mechanical properties found in the literature are further discussed.
The influence of the chemical properties of polymers on gel formation mechanism and gel properties was also investigated. For this, model substances with various uronic acid content, degree of esterification and amount of calcium were tested and their amount of high molecular weight substances was measured. The substances investigated included pectic polysaccharides and chia seed mucilage as model polymers and wheat and maize root mucilage. Polygalacturonic acid and low-methoxy pectin proved as non-suitable model polymers for seed and root mucilage as ionic interactions with calcium control their properties. Mucilage properties rather seem to be governed by weak electrostatic interactions between the entangled polymer chains. The amount of high molecular weight material varies considerably depending on mucilage´s origin and seems to be a straight factor for mucilage’s gel effect in soil. Additionally to the chemical characterization of the high molecular weight compounds, determination of their molecular weight and of their conformation in several mucilages types is needed to draw composition-property profiles. The variations measured between the various mucilages also highlight the necessity to study how the specific properties of the various mucilages fulfill the needs of the plant from which they are exuded.
Finally, the integration of molecular interactions in gel and interparticulate gel properties to explain the physical properties of the rhizosphere was discussed. This approach offers numerous perspectives to clarify for example how water content or hydraulic conductivity in the rhizosphere vary according to the properties of the exuded mucilage. The hypothesis that the gel effect is general for all soil-born exudates showing gel properties was considered. As a result, a classification of soil-born gel phases including roots, seeds, bacteria, hyphae and earthworm’s exuded gel-like material according to their common gel physico-chemical properties is recommended for future research. An outcome could be that the physico-chemical properties of such gels are linked with the extent of the gel effect, with their impact on soil properties and with the functions of the gels in soil.
Non-Consumptive Effects of Spiders and Ants: Does Fear Matter in Terrestrial Interaction Webs?
(2014)
Most animals suffer from predators. Besides killing prey, predators can affect prey physiology, morphology and behaviour. Spiders are among the most diverse and frequent predators in terrestrial ecosystems. Our behavioural arena experiments revealed that behavioural changes under spider predation risk are relatively scarce among arthropods. Wood crickets (Nemobius sylvestris), in particular, changed their behaviour in response to cues of various spider species. Thereby, more common and relatively larger spider species induced stronger antipredator behaviour in crickets.
Behavioural changes under predation risk are expected to enhance predator avoidance, but they come at a cost. Crickets previously confronted with cues of the nursery web spider (Pisaura mirabilis) were indeed more successful in avoiding predation. Surprisingly, crickets slightly increased food uptake and lost less weight under predation risk, indicating that crickets are able to compensate for short-term cost under predation risk. In a following plant choice experiment, crickets strongly avoided plants bearing spider cues, which in turn reduced the herbivory on the respective plants.
Similar to spiders, ants are ubiquitous predators and can have a strong impact on herbivores, but also on other predators. Juvenile spiders increased their propensity for long-distance dispersal if exposed to ant cues. Thus, spiders use this passive dispersal through the air (ballooning) to avoid ants and colonise new habitats.
In a field experiment, we compared arthropod colonisation between plants bearing cues of the nursery web spider and cue-free plants. We followed herbivory during the experimental period and sampled the arthropod community on the plants. In accordance with the plant choice experiment, herbivory was reduced on plants bearing spider cues. In addition, spider cues led to changes in the arthropod community: smaller spiders and black garden ants (Lasius niger) avoided plants bearing spider cues. In contrast, common red ants (Myrmica rubra) increased the recruitment of workers, possibly to protect their aphids.
Although behavioural changes were relatively rare on filter papers bearing spider cues, more natural experimental setups revealed strong and far-reaching effects of predation risk. We further suggest that risk effects influence the spatial distribution of herbivory, rather than reduce overall herbivory that is expected if predators kill herbivores. Consequently, the relative importance of predation and risk effects is crucial for the way predators affect lower trophic levels.
Studies have shown that wastewater treatment plant (WWTP) effluents are the major pathways of organic and inorganic chemicals of anthropogenic use (=micropollutants) into aquatic environments. There, micropollutants can be transferred to ground water bodies - and may finally end up in drinking water - or cause various effects in aquatic organisms like multiple resistances of bacteria. Hence, the upgrading of WWTPs with the aim to reduce the load of those micropollutants is currently under discussion.
Therefore, the primary objective of this thesis was to assess ecotoxicological effects of wastewater ozonation, a tertiary treatment method, using specifically developed toxicity tests with Gammarus fossarum (Koch) at various levels of ecological complexity. Several studies were designed in the laboratory and under semi-field conditions to cope with this primary objective. Prior to the investigations with ozone treated wastewater, the ecotoxicity of secondary treated (=non-ozone treated) wastewater from WWTP Wüeri, Switzerland, for the test species was assessed by a four-week experiment. This experiment displayed statistically significant impairments in feeding, assimilation and physiological endpoints related to population development and reproduction. The first experiment investigating ecotoxicological implications of ozone application in wastewater from the same WWTP displayed a preference of G. fossarum for leaf discs conditioned in ozone treated wastewater when offered together with leaf discs conditioned in non-ozone treated wastewater. This effect seems to be mainly driven by an alteration in the leaf associated microbial community. Another series of laboratory experiments conducted also with wastewater from WWTP Wüeri treated with ozone at the lab- or full-scale, revealed significantly increased feeding rates of G. fossarum exposed to ozone treated wastewater compared to non-ozone treated wastewater. These laboratory experiments also indicated that any alteration in the organic matrix potentially caused by ozone treatment is not related to the effects in feeding as this endpoint showed only negligible deviation in secondary treated wastewater, which contained hardly any (micro)pollutants (i.e. pharmaceuticals), from the same wastewater additionally treated with ozone. Moreover, it was shown that shifts in the dissolved organic carbon (DOC) profile do not affect the feeding rate of gammarids. In situ bioassays conducted in the receiving stream of the WWTP Wüeri confirmed the results of the laboratory experiments by displaying significantly reduced feeding rates of G. fossarum exposed below the WWTP effluent if non-ozone treated wastewater was released. However, at the time the ozonation was operating, no adverse effects in feeding rates were observed below the effluent compared to the unaffected upstream sites. Also population studies in on-site flow-through stream microcosms displayed an increased feeding and a statistically significantly higher population size after ten weeks when exposed to ozone treated wastewater compared to non-ozone treated wastewater.
In conclusion, the present thesis documents that ozonation might be a suitable tool to reduce both the load of micropollutants as well as the ecotoxicity of wastewaters. Thus, this technology may help to meet the requirements of the Water Framework Directive also under predicted climate change scenarios, which may lead to elevated proportions of wastewater in the receiving stream during summer discharge. However, as ozone application may also produce by-products with a higher toxicity than their parent compounds, the implementation of this technique should be assessed further both via chemical analysis and ecotoxicological bioassays.
The adoption of the EU Water Framework Directive (WFD) in 2000 marked the beginning of a new era of European water policy. However, more than a decade later, the majority of European rivers are still failing to meet one of the main objectives of the WFD: the good ecological status. Pesticides are a major stressor for stream ecosystems. This PhD thesis emphasises the need for WFD managers to consider all main agricultural pesticide sources and influencing landscape parameters when setting up River Basin Management Plans and Programmes of Measures. The findings and recommendations of this thesis can help to successfully tackle the risk of pesticide contamination to achieve the WFD objectives.
A total of 663 sites that were situated in the German Federal States of Saxony, Saxony-Anhalt, Thuringia and Hesse were studied (Chapter 3 and 4). In addition to an analysis of the macroinvertebrate data of the governmental WFD monitoring network, a detailed GIS analysis of the main agricultural pesticide sources (arable land and garden allotments as well as wastewater treatment plants (WWTPs)) and landscape elements (riparian buffer strips and forested upstream reaches) was conducted. Based on the results, a screening approach was developed that allows an initial rapid and cost-effective identification of those sites that are potentially affected by pesticide contamination. By using the trait-based bioindicator SPEARpesticides, the insecticidal long-term effects of the WWTP effluents on the structure of the macroinvertebrate community were identified up to at least 1.5 km downstream (in some cases even 3 km) of the WWTPs. The results of the German Saprobic Index revealed that the WWTPs can still be important sources of oxygen-depleting substances. Furthermore, the results indicate that forested upstream reaches and riparian buffer strips at least 5 m in width can be appropriate measures in mitigating the effects and exposure of pesticides.
There are concerns that the future expansion of energy crop cultivation will lead to an increased pesticide contamination of ecosystems in agricultural landscapes. Therefore, the potential of energy crops for pesticide contamination was examined based on an analysis of the development of energy crop cultivation in Germany and a literature search on perennial energy crops (Chapter 5). The results indicate that the future large-scale expansion of energy crop cultivation will not necessarily cause an increase or decrease in the amounts of pesticides that are released into the environment. The potential effects will depend on the future design of the agricultural systems. Instead of creating energy monocultures, annual energy crops should be integrated into the existing food production systems. Financial incentives and further education are needed to encourage the use of sustainable crop rotations, innovative cropping systems and perennial energy crops, which may contribute to crop diversity and generate lower pesticide demands than do intensive farming systems.
Sediment transport contributes to the movement of inorganic and organic material in rivers. The construction of a dam interrupts the continuity of this sediment transport through rivers, causing sediments to accumulate within the reservoir. Reservoirs can also act as carbon sinks and methane can be released when organic matter in the sediment is degraded under anoxic conditions. Reservoir sedimentation poses a great threat to the sustainability of reservoirs worldwide, and can emit the potent greenhouse gas methane into the atmosphere. Sediment management measures to rehabilitate silted reservoirs are required to achieve both better water quantity and quality, as well as to mitigate greenhouse gas emissions.
This thesis aims at the improvement of sediment sampling techniques to characterize sediment deposits as a basis for accurate and efficient water jet dredging and to monitor the dredging efficiency by measuring the sediment concentration. To achieve this, we investigated freeze coring as a method to sample (gas-bearing) sediment in situ. The freeze cores from three reservoirs obtained were scanned using a non-destructive X-Ray CT scan technique. This allows the determination of sediment stratification and character-ization of gas bubbles to quantify methane emissions and serve as a basis for the identi-fication of specific (i.e. contaminated) sediment layers to be dredged. The results demon-strate the capability of freeze coring as a method for the characterization of (gas-bearing) sediment and overcomes certain limitations of commonly used gravity cores. Even though the core’s structure showed coring disturbances related to the freezing process, the general core integrity seems to not have been disturbed. For dredging purposes, we analyzed the impact pressure distribution and spray pattern of submerged cavitating wa-ter jets and determined the effects of impinging distances and angles, pump pressures and spray angles. We used an adapted Pressure Measurement Sensing technique to enhance the spatial distribution, which proved to be a comparatively easy-to-use meas-urement method for an improved understanding of the governing factors on the erosional capacity of cavitating water jets. Based on this data, the multiple linear regression model can be used to predict the impact pressure distribution of those water jets to achieve higher dredging accuracy and efficiency. To determine the dredging operational efficien-cy, we developed a semi-continuous automated measurement device to measure the sediment concentration of the slurry. This simple and robust device has lower costs, compared to traditional and surrogate sediment concentration measurement technolo-gies, and can be monitored and controlled remotely under a wide range of concentrations and grain-sizes, unaffected by entrained gas bubbles
Wild bees are essential for the pollination of wild and cultivated plants. However, within the
last decades, the increasing intensification of modern agriculture has led to both a reduction and fragmentation as well as a degradation of the habitats wild bees need. The resulting loss of pollinators and their pollination poses an immense challenge to global food production. To support wild bees, the availability of flowering resources is essential. However, the flowering period of each resource is temporally limited and has different effects on pollinators and their pollination, depending on the time of their flowering.
Therefore, to efficiently promote and manage wild bee pollinators in agricultural landscapes, we identified species-specific key floral resources of three selected wild bee species and their spatial and temporal availability (CHAPTERS 2, 3 & 4). We examined, which habitat types predominantly provide these resources (CHAPTERS 3 & 4). We also investigated whether floral resource maps based on the use of these key resources and their spatial and temporal availability explain the abundance and development of the selected wild bees (CHAPTERS 3 & 4) and pollination (CHAPTER 5) better than habitat maps, that only indirectly account for the availability of floral resources.
For each of the species studied, we were able to identify different key pollen sources, predominantly woody plants in the early season (April/May) and increasingly herbaceous plants in the later season (June/July; CHAPTERS 2, 3 & 4). The open woody semi-natural habitats of our agricultural landscapes provided about 75% of the floral resources for the buff-tailed bumblebees, 60% for the red mason bees, and 55% for the horned mason bees studied, although they accounted for only 3% of the area (CHAPTERS 3 & 4). In addition, fruit orchards provided about 35% of the floral resources for the horned mason bees on 4% of the landscape area (CHAPTER 3). We showed that both mason bee species benefited from the resource availability in the surrounding landscapes (CHAPTER 3). Yet this was not the case for the bumblebees (CHAPTER 4). Instead, the weight gain of their colonies, the number of developed queen cells and their colony survival were higher with increasing proximity to forests. The proximity to forests also had a positive effect on the mason bees studied (CHAPTER 3). In addition, the red mason bees benefited from herbaceous semi-natural habitats. The proportion of built-up areas had a negative effect on the horned mason bees, and the proportion of arable land on the red mason bees. The habitat maps explained horned mason bee abundances equally well as the floral resource maps, but red mason bee abundances were distinctly better explained by key floral resources. The pollination of field bean increased with higher proportions of early floral resources, whereas synchronous floral resources showed no measurable reduction in their pollination (CHAPTER 5). Habitat maps also explained field bean pollination better than floral resource maps. Here, pollination increased with increasing proportions of built-up areas in the landscapes and decreased with increasing proportions of arable land.
Our results highlight the importance of the spatio-temporal availability of certain key species as resource plants of wild bees in agricultural landscapes. They show that habitat maps are ahead of, or at least equal to, spatio-temporally resolved floral resource maps in predicting wild bee development and pollination. Nevertheless, floral resource maps allow us to draw more accurate conclusions between key floral resources and the organisms studied. The proximity to forest edges had a positive effect on each of the three wild bee species studied. However, besides pure food availability, other factors seem to co-determine the occurrence of wild bees in agricultural landscapes.
Recent EU-frameworks enforce the implementation of risk mitigation measures for nonpoint-source pesticide pollution in surface waters. Vegetated surface flow treatments systems (VTS) can be a way to mitigate risk of adverse effects in the aquatic ecosystems following unavoidable pollution after rainfall-related runoff events. Studies in experimental wetland cells and vegetated ditch mesocosms with common fungicides, herbicides and insecticides were performed to assess efficiency of VTS. Comprehensive monitoring of fungicide exposure after rainfall-related runoff events and reduction of pesticide concentrations within partially optimised VTS was performed from 2006-2009 at five vegetated detention ponds and two vegetated ditches in the wine growing region of the Southern Palatinate (SW-Germany).
Influence of plant density, size related parameters and pesticide properties in the performance of the experimental devices, and the monitored systems were the focus of the analysis. A spatial tool for prediction of pesticide pollution of surface waters after rainfall-related runoff events was programmed in a geographic information system (GIS). A sophisticated and high resolution database on European scale was built for simulation. With the results of the experiments, the monitoring campaign and further results of the EU-Life Project ArtWET mitigation measures were implemented in a georeferenced spatial decision support system. The database for the GIS tools was built with open data. The REXTOX (ratio of exposure to toxicity) Risk Indicator, which was proposed by the OECD (Organisation for Economic Co-operation and Development), was extended, and used for modeling the risk of rainfall-related runoff exposure to pesticides, for all agricultural waterbodies on European scale. Results show good performance of VTS. The vegetated ditches and wetland cells of the experimental systems showed a very high reduction of more than 90% of pesticide concentrations and potential adverse effects. Vegetated ditches and wetland cells performed significantly better than devices without vegetation. Plant density and sorptivity of the pesticide were the variables with the highest explanatory power regarding the response variable reduction of concentrations. In the experimental vegetated ditches 65% of the reduction of peak concentrations was explained with plant density and KOC. The monitoring campaign showed that concentrations of the fungicides and potential adverse effects of the mixtures were reduced significantly within vegetated ditches (Median 56%) and detention ponds (Median 38%) systems. Regression analysis with data from the monitoring campaign identified plant density and size related properties as explanatory variables for mitigation efficiency (DP: R²=0.57, p<0.001; VD:
R²=0.19, p<0.001). Results of risk model runs are the input for the second tool, simulating three risk mitigation measures. VTS as risk mitigation measures are implemented using the results for plant density and size related performance of the experimental and monitoring studies, supported by additional data from the ArtWET project. Based on the risk tool, simulations can be performed for single crops, selected regions, different pesticide compounds and rainfall events. Costs for implementation of the mitigation measures are estimated. Experiments and monitoring, with focus on the whole range of pesticides, provide novel information on VTS for pesticide pollution. The monitoring campaign also shows that fungicide pollution may affect surface waters. Tools developed for this study are easy to use and are not only a good base for further spatial analysis but are also useful as decision support of the non-scientific community. On a large scale, the tools on the one hand can help to compute external costs of pesticide use with simulation of mitigation costs on three levels, on the other hand feasible measures mitigating or remediating the effects of nonpoint-source pollution can be identified for implementation. Further study of risk of adverse effects caused by fungicide pollution and long-time performance of optimised VTS is needed.
Die Arbeit stellt die Frage nach den Effekten einer tertiären Präventionsmaßnahme in Bezug auf Schmerzbewältigung und Schmerzveränderung bei chronischen Lumbalgiepatienten. Im Rahmen der Überprüfung werden ausdifferenzierte psychophysische Interventionsmaßnahmen aus den Bereichen der Physiotherapie/Krankengymnastik und Psychologie eingesetzt. Die Gruppenunterteilung erfolgt in eine behandelte Versuchsgruppe und eine unbehandelte Warte-Kontrollgruppe mit jeweils 100 Probanden (N=200). Die Ergebnisse der tertiären Präventionsmaßnahme zeigen statistisch und klinisch relevante sowie positive Veränderungen in den Bereichen der Schmerzbewältigung und Schmerzveränderung.
Agriculture covers one third of the world land area and has become a major source of water pollution due to its heavy reliance on chemical inputs, namely fertilisers and pesticides. Several thousands of tonnes of these chemicals are applied worldwide annually and partly reach freshwaters. Despite their widespread use and relatively unspecific modes of action, fungicides are the least studied group of pesticides. It remains unclear whether the taxonomic groups used in pesticide risk assessment are protective for non-target freshwater fungi. Fungi and bacteria are the main microbial decomposers converting allochthonous organic matter (litter) into a more nutritious food resource for leaf-shredding macroinvertebrates. This process of litter decomposition (LD) is central for aquatic ecosystem because it fuels local and downstream food webs with energy and nutrients. Effects of fungicides on decomposer communities and LD have been mainly analysed under laboratory conditions with limited representation of the multiple factors that may moderate effects in the field.
In this thesis a field study was conducted in a German vineyard area to characterise recurrent episodic exposure to fungicides in agricultural streams (chapter 2) and its effects on decomposer communities and LD (chapter 3). Additionally, potential interaction effects of nutrient enrichment and fungicides on decomposer communities and LD were analysed in a mesocosm experiment (chapter 4).
In the field study event-driven water sampling (EDS) and passive sampling with EmporeTM styrene-divinylbenzene reverse phase sulfonated disks (SDB disks) were used to assess exposure to 15 fungicides and 4 insecticides. A total of 17 streams were monitored during 4 rainfall events within the local application period of fungicides in 2012. EDS exceeded the time-weighted average concentrations provided by the SDB disks by a factor of 3, though high variability among compounds was observed. Most compounds were detected in more than half of the sites and mean and maximum peak (EDS) concentrations were under 1 and 3 µg/l, respectively. Besides, SDB disk-sampling rates and a free-software solution to derive sampling rates under time-variable exposure were provided.
Several biotic endpoints related to decomposers and LD were measured in the same sampling sites as the fungicide monitoring, coinciding with the major litter input period. Our results suggest that polar organic fungicides in streams change the structure of the fungal community. Causality of this finding was supported by a subsequent microcosm experiment. Whether other effects observed in the field study, such as reduced fungal biomass, increased bacterial density or reduced microbial LD can be attributed to fungicides remains speculative and requires further investigation. By contrast, neither the invertebrate LD nor in-situ measured gammarid feeding rates correlated with water-borne fungicide toxicity, but both were negatively associated with sediment copper concentrations. The mesocosm experiment showed that fungicides and nutrients affect microbial decomposers differently and that they can alter community structure, though longer experiments are needed to determine whether these changes may propagate to invertebrate communities and LD. Overall, further studies should include representative field surveys in terms of fungicide pollution and physical, chemical and biological conditions. This should be combined with experiments under controlled conditions to test for the causality of field observations.