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- Pesticides (3)
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- ecotoxicology (3)
- Wastewater treatment plants (2)
- decomposition (2)
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- traits (2)
- Abwasserreinigung (1)
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- Endokrine Regulation (1)
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- Fungizid (1)
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- SPEAR (1)
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- aquatic ecotoxicology (1)
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- chemical risk assessment (1)
- endocrine disrupting chemicals (1)
- endokrine Regulation (1)
- freshwater ecosystem (1)
- fungicide (1)
- invertebrates (1)
- life cycle test (1)
- macroinvertebrates (1)
- methane (1)
- mitigation (1)
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- monitoring (1)
- organic pollution (1)
- pesticide (1)
- pesticides (1)
- point source (1)
- pollution (1)
- runoff (1)
- stream (1)
- streams (1)
- vegetated treatment systems (1)
- Ökosystem (1)
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Streams are coupled with their riparian area. Emerging insects from streams can be an important prey in the riparian area. Such aquatic subsidies can cause predators to switch prey or increase predator abundances. This can impact the whole terrestrial food web. Stressors associated with agricultural land use can alter insect communities in water and on land, resulting in complex response patterns of terrestrial predators that rely on prey from both systems.
This thesis comprises studies on the impact of aquatic nsects on a terrestrial model ecosystem (Objective 1, hapter 2), the influence of agricultural land use on riparian spiders’ traits and community (Objective 2, Chapter 3), and on the impact of agricultural land use on the contribution of different prey to spider diet (Objective 3, Chapter 4).
In chapter 2, I present a study where we conducted a mesocosm experiment to examine the effects of aquatic subsidies on a simplified terrestrial food web consisting of two types of herbivores (leafhoppers and weevils), plants and predators (spiders). I focused on the prey choice of the spiders by excluding predator immigration and reproduction. In accordance with predator switching, survival of leafhoppers increased in the presence of aquatic subsidies. By contrast, the presence of aquatic subsidies indirectly reduced weevils and herbivory.
In chapter 3, I present the results on the taxonomic and trait response of riparian spider communities to gradients of agricultural stressors and environmental variables, with a particular emphasis on pesticides. To capture spiders with different traits and survival strategies, we used multiple collection methods. Spider community composition was best explained by in-stream pesticide toxicity and shading of the stream bank, a proxy for the quality of the habitat. Species richness and the number of spider individuals, as well as community ballooning ability, were negatively associated with in-stream pesticide toxicity. In contrast, mean body size and shading preference of spider communities responded strongest to shading,
whereas mean niche width (habitat preference for moisture and shading) responded strongest to other environmental variables.
In chapter 4, I describe aquatic-terrestrial predator-prey relations with gradients of agricultural stressors and environmental variables. I sampled spiders, as well as their aquatic and terrestrial prey along streams with an assumed pesticide pollution gradient and determined their stable carbon and nitrogen signals. Potential aquatic prey biomass correlated positively with an increasing aquatic prey contribution of T. montana. The contribution of aquatic prey to the diet of P. amentata showed a positive relationship with increasing toxicity in streams.
Overall, this thesis contributes to the emerging discipline of cross-ecosystem ecology and shows that aquatic-terrestrial linkages and riparian food webs can be influenced by land use related stressors. Future manipulative field studies on aquatic-terrestrial linkages are required that consider the quality of prey organisms, fostering mechanistic understanding of such crossecosystem effects. Knowledge on these linkages is important to improve understanding of consequences of anthropogenic stressors and to prevent further losses of ecosystems and their biodiversity.
Agricultural pesticides, especially insecticides, are an integral part of modern farming. However, these may often leave their target ecosystems and cause adverse effects in non- target, especially freshwater ecosystems, leading to their deterioration. In this thesis, the focus will be on Insect Growth Regulators (IGRs) that can in many ways cause disruption of the endocrine system of invertebrates. Freshwater invertebrates play important ecological, economic and medical roles, and disruption of their endocrine systems may be crucial, considering the important role hormones play in the developmental and reproductive processes in organisms. Although Endocrine Disruption Chemicals (EDCs) can affect moulting, behaviour, morphology, sexual maturity, time to first brood, egg development time, brood size (fecundity), and sex determination in invertebrates, there is currently no agreement upon how to characterize and assess endocrine disruption (ED). Current traditional ecotoxicity tests for Ecological Risk Assessment (ERA) show limitations on generating data at the population level that may be relevant for the assessment of EDCs, which effects may be sublethal, latent and persist for several generations of species (transgenerational).
It is therefore the primary objective of this thesis to use a test method to investigate adverse effects of EDCs on endpoints concerning development and reproduction in freshwater invertebrates. The full life-cycle test over two generations that includes all sensitive life stages of C. riparius (a sexual reproductive organism) allows an assessment of its reproduction and should be suitable for the investigation of long-term toxicity of EDCs in freshwater invertebrates. C. riparius is appropriate for this purpose because of its short life cycle that enables the assessment of functional endpoints of the organism over several generations. Moreover, the chironomid life cycle consists of a complete metamorphosis controlled by a well-known endocrine mechanism and the endocrine system of insects has been most investigated in great detail among invertebrates. Hence, the full life-cycle test with C. riparius provides an approach to assess functional endpoints (e.g. reproduction, sex ratio) that are population-relevant as a useful amendment to the ERA of EDCs. In the laboratory, C. riparius was exposed to environmentally-relevant concentrations of the selected IGRs in either spiked water or spiked sediment scenario over two subsequent generations.
The results reported in this thesis revealed significant effects of the IGRs on the development and the reproduction of C. riparius with the second (F1) generation showing greater sensitivity. These findings indicated for the first time the suitability of multigenerational testing for various groups of EDCs and strongly suggested considering the full life-cycle of C. riparius as an appropriate test method for a better assessment of EDCs in the freshwater environment. In conclusion, this thesis helps to detect additional information that can be extrapolated at population level and, thus, might contribute to better protection of freshwater ecosystems against the risks of Endocrine Disrupting Chemicals (EDCs.) It may furthermore contribute to changes in the ERA process that are necessary for a real implementation of the new European chemical legislation, REACH (Registration, Evaluation Authorization and Restriction of Chemicals). Finally, significant interactions between temperature, chemical exposure and generation were reported for the first time and, may help predict impacts that may occur in the future, in the field, under predicted climate change scenarios.
Change of ecosystems and the associated loss of biodiversity is among the most important environmental issues. Climate change, pollution, and impoundments are considered as major drivers of biodiversity loss. Organism traits are an appealing tool for the assessment of these three stressors, due to their ability to provide mechanistic links between organism responses and stressors, and consistency over wide geographical areas.
Additionally, traits such as feeding habits influence organismal performance and ecosystem processes. Although the response of traits of specific taxonomic groups to stressors is known, little is known about the response of traits of different taxonomic groups to stressors. Additionally, little is known about the effects of small impoundments on stream ecosystem processes, such as leaf litter decomposition, and food webs.
After briefly introducing the theoretical background and objectives of the studies, this thesis begins by synthesizing the responses of traits of different taxonomic groups to climate change and pollution. Based on 558 peer-reviewed studies, the uniformity (i.e., convergence) in trait response across taxonomic groups was evaluated through meta-analysis (Chapter 2). Convergence was primarily limited to traits related to tolerance.
In Chapter 3, the hypothesis that small impoundments would modify leaf litter decomposition rates at the sites located within the vicinity of impoundments, by altering habitat variables and invertebrate functional feeding groups (FFGs) (i.e., shredders), was tested. Leaf litter decomposition rates were significantly reduced at the study sites located immediately upstream (IU) of impoundments, and were significantly related to the abundance of invertebrate shredders.
In Chapter 4, the invertebrate FFGs were used to evaluate the effect of small impoundments on stream ecosystem attributes. The results showed that heterotrophic production was significantly reduced at the sites IU. With regard to food webs, the contribution of methane gas derived carbon to the biomass of chironomid larvae was evaluated through correlation of stable carbon isotope values of chironomid larvae and methane gas concentrations.
The results indicated that the contribution of methane gas derived carbon into stream benthic food web is low. In conclusion, traits are a useful tool in detecting ecological responses to stressors across taxonomic groups, and the effects of small impoundments on stream ecological integrity and food web are limited.
World’s ecosystems are under great pressure satisfying anthropogenic demands, with freshwaters being of central importance. The Millennium Ecosystem Assessment has identified anthropogenic land use and associated stressors as main drivers in jeopardizing stream ecosystem functions and the
biodiversity supported by freshwaters. Adverse effects on the biodiversity of freshwater organisms, such as macroinvertebrates, may propagate to fundamental ecosystem functions, such as organic matter breakdown (OMB) with potentially severe consequences for ecosystem services. In order to adequately protect and preserve freshwater ecosystems, investigations regarding potential and observed as well as direct and indirect effects of anthropogenic land use and associated stressors (e.g. nutrients, pesticides or heavy metals) on ecosystem functioning and stream biodiversity are needed. While greater species diversity most likely benefits ecosystem functions, the direction and magnitude of changes in ecosystem functioning depends primarily on species functional traits. In this context, the functional diversity of stream organisms has been suggested to be a more suitable predictor of changes in ecosystem functions than taxonomic diversity.
The thesis aims at investigating effects of anthropogenic land use on (i) three ecosystem functions by anthropogenic toxicants to identify effect thresholds (chapter 2), (ii) the organic matter breakdown by three land use categories to identify effects on the functional level (chapter 3) and (iii)on the stream community along an established land-use gradient to identify effects on the community level.
In chapter 2, I reviewed the literature regarding pesticide and heavy metal effects on OMB, primary production and community respiration. From each reviewed study that met inclusion criteria, the toxicant concentration resulting in a reduction of at least 20% in an ecosystem function was standardized based on laboratory toxicity data. Effect thresholds were based on the relationship between ecosystem functions and standardized concentration-effect relationships. The analysis revealed that more than one third of pesticide observations indicated reductions in ecosystem functions at concentrations that are assumed being protective in regulation. However, high variation within and between studies hampered the derivation of a concentration-effect relationship and thus effect thresholds.
In chapter 3, I conducted a field study to determine the microbial and invertebrate-mediated OMB by deploying fine and coarse mesh leaf bags in streams with forested, agricultural, vinicultural
and urban riparian land use. Additionally, physicochemical, geographical and habitat parameters were monitored to explain potential differences in OMB among land use types and sites. Regarding results, only microbial OMB differed between land use types. The microbial OMB showed a negative relationship with pH while the invertebrate-mediated OMB was positively related to tree cover. OMB responded to stressor gradients rather than directly to land use.
In chapter 4, macroinvertebrates were sampled in concert with leaf bag deployment and after species identification (i) the taxonomic diversity in terms of Simpson diversity and total taxonomic
richness (TTR) and (ii) the functional diversity in terms of bio-ecological traits and Rao’s quadratic entropy was determined for each community. Additionally, a land-use gradient was established and the response of the taxonomic and functional diversity of invertebrate communities along this gradient was investigated to examine whether these two metrics of biodiversity are predictive for the rate of OMB. Neither bio-ecological traits nor the functional diversity showed a significant relationship with
OMB. Although, TTR decreased with increasing anthropogenic stress and also the community structure and 26 % of bio-ecological traits were significantly related to the stress gradient, any of these shifts propagated to OMB.
Our results show that the complexity of real-world situations in freshwater ecosystems impedes the effect assessment of chemicals and land use for functional endpoints, and consequently our potential to predict changes. We conclude that current safety factors used in chemical risk assessment may not be sufficient for pesticides to protect functional endpoints. Furthermore, simplifying real-world stressor gradients into few land use categories was unsuitable to predict and quantify losses in OMB. Thus, the monitoring of specific stressors may be more relevant than crude land use categories to detect effects on ecosystem functions. This may, however, limit the large scale assessment of the status of OMB. Finally, despite several functional changes in the communities the functional diversity over several trait modalities remained similar. Neither taxonomic nor functional diversity were suitable predictors of OMB. Thus, when understanding anthropogenic impacts on the linkage between biodiversity and ecosystem functioning is of main interest, focusing on diversity metrics that are clearly linked to the stressor in question (Jackson et al. 2016) or integrating taxonomic and functional metrics (Mondy et al., 2012) might enhance our predictive capacity.
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.
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.
Aquatische Ökosysteme sind einer Vielzahl an Umweltstressoren sowie Mischungen chemischer Substanzen ausgesetzt, darunter Petroleum und Petrochemikalien, Metalle und Pestizide. Aquatische Gemeinschaften wirbelloser Arten werden als Bioindikatoren genutzt,
um Langzeit- sowie integrale Effekte aufzuzeigen. Die Information über das Vorkommen von Arten kann dabei um weitere Informationen zu Eigenschaften dieser Arten ergänzt werden.
SPEAR-Bioindikatoren fassen diese Informationen für Artengemeinschaften zusammen.
Ziel der vorliegenden Doktorarbeit war es, die Spezifität von SPEAR-Indikatoren gegenüber
einzelnen Chemikaliengruppen zu verbessern – speziell für Ölsand-Bestandteile,
Kohlenwasserstoffe und Metalle.
Für die Entwicklung eines Bioindikators für diskontinuierliche Belastung mit organischen Ölbestandteilen wurde eine Freilandbeprobung in der kanadischen Ölsand-Abbauregion im nördlichen Alberta durchgeführt. Die Arteneigenschaften „physiologische Sensitivitiät
gegenüber organischen Chemikalien“ sowie „Generationszeit“ wurden in einem Indikator,
SPEARoil, integriert, welcher die Sensitivität der Artengemeinschaften gegenüber Ölsand-Belastung in Abhängigkeit von luktuierenden hydrologischen Bedingungen aufzeigt.
Äquivalent zum SPEARorganic-Ansatz wurde eine Rangliste der physiologischen Sensitivität einzelner Arten gegenüber Kohlenwasserstoff-Belastung durch Rohöl oder Petroleum
entwickelt. Hierfür wurden Informationen aus ökotoxikologischen Kurzzeit-Laborversuchen durch Ergebnisse aus Schnell- und Mesokosmen-Tests ergänzt. Die daraus entwickelten
Shydrocarbons-Sensitivitätswerte können in SPEAR-Bioindikatoren genutzt werden.
Um Metallbelastung in Gewässern mittels Bioindikatoren spezifisch nachweisen zu können,
wurden die Arteneigenschaften „physiologische Metallsensitivität“ und „Ernährungsweise“
von Artengemeinschaften in australischen Feldstudien ausgewertet. Sensitivitätswerte für
Metalle erklärten die Effekte auf die Artengemeinschaften im Gewässer jedoch unzureichend.
Die „Ernährungsweise“ hingegen war stark mit der Metallbelastung korreliert. Der Anteil räuberischer Invertebratenarten in einer Gemeinschaft kann daher als Indikator für Metallbelastung in Gewässern dienen.
Weiterhin wurden verschiedene Belastungsanzeiger für Chemikalien-Cocktails in der Umwelt anhand von Pestizid-Datensätzen verglichen. Belastungsanzeiger, die auf der 5%-Fraktion
einer Species-Sensitivity-Distribution beruhen, eigneten sich am besten, gefolgt von Toxic Unit-Ansätzen, die auf der sensitivsten Art einer Gemeinschaft oder Daphnia magna beruhen.
Mathematical models of species dispersal and the resilience of metapopulations against habitat loss
(2021)
Habitat loss and fragmentation due to climate and land-use change are among the biggest threats to biodiversity, as the survival of species relies on suitable habitat area and the possibility to disperse between different patches of habitat. To predict and mitigate the effects of habitat loss, a better understanding of species dispersal is needed. Graph theory provides powerful tools to model metapopulations in changing landscapes with the help of habitat networks, where nodes represent habitat patches and links indicate the possible dispersal pathways between patches.
This thesis adapts tools from graph theory and optimisation to study species dispersal on habitat networks as well as the structure of habitat networks and the effects of habitat loss. In chapter 1, I will give an introduction to the thesis and the different topics presented in this thesis. Chapter 2 will then give a brief summary of tools used in the thesis.
In chapter 3, I present our model on possible range shifts for a generic species. Based on a graph-based dispersal model for a generic aquatic invertebrate with a terrestrial life stage, we developed an optimisation model that models dispersal directed to predefined habitat patches and yields a minimum time until these patches are colonised with respect to the given landscape structure and species dispersal capabilities. We created a time-expanded network based on the original habitat network and solved a mixed integer program to obtain the minimum colonisation time. The results provide maximum possible range shifts, and can be used to estimate how fast newly formed habitat patches can be colonised. Although being specific for this simulation model, the general idea of deriving a surrogate can in principle be adapted to other simulation models.
Next, in chapter 4, I present our model to evaluate the robustness of metapopulations. Based on a variety of habitat networks and different generic species characterised by their dispersal traits and habitat demands, we modeled the permanent loss of habitat patches and subsequent metapopulation dynamics. The results show that species with short dispersal ranges and high local-extinction risks are particularly vulnerable to the loss of habitat across all types of networks. On this basis, we then investigated how well different graph-theoretic metrics of habitat networks can serve as indicators of metapopulation robustness against habitat loss. We identified the clustering coefficient of a network as the only good proxy for metapopulation robustness across all types of species, networks, and habitat loss scenarios.
Finally, in chapter 5, I utilise the results obtained in chapter 4 to identify the areas in a network that should be improved in terms of restoration to maximise the metapopulation robustness under limited resources. More specifically, we exploit our findings that a network’s clustering coefficient is a good indicator for metapopulation robustness and develop two heuristics, a Greedy algorithm and a deducted Lazy Greedy algorithm, that aim at maximising the clustering coefficient of a network. Both algorithms can be applied to any network and are not specific to habitat networks only.
In chapter 6, I will summarize the main findings of this thesis, discuss their limitations and give an outlook of future research topics.
Overall this thesis develops frameworks to study the behaviour of habitat networks and introduces mathematical tools to ecology and thus narrows the gap between mathematics and ecology. While all models in this thesis were developed with a focus on aquatic invertebrates, they can easily be adapted to other metapopulations.
Aktuelle Entwicklungen in der Europäischen Gesetzgebung fordern die Umsetzung von Risikominderungsmaßnahmen, die diffuse Einträge von Pestiziden in Oberflächengewässer und deren Schadwirkung mindern sollen. Bepflanzte Gräben und Feuchtgebiete (vegetated treatment systems: VTS) bieten die Möglichkeit potenzielle Schadwirkung von Pestizideinträgen infolge von Oberflächenabflussereignissen zu mindern, die mit anderen Maßnahmen unvermeidbar wären. Versuche in experimentellen Feuchtgebieten und bepflanzten Gräben wurden durchgeführt, um die Funktionstüchtigkeit möglicher Systeme zu untersuchen. In fünf Rückhaltebecken und zwei bepflanzten Gräben in der Weinbauregion Südpfalz (Südwestdeutschland) wurde von 2006 bis 2009 eine umfangreiche Beprobung von belastetem Wasser nach Starkregenereignissen vorgenommen und die Reduktionsleistung der Systeme bezüglich der eingetragenen Konzentrationen ermittelt. Der Einfluss von Pflanzendichte, Größe der Systeme und Eigenschaften der eingetragenen, bzw. experimentell eingespeisten Substanzen war Schwerpunkt bei der Auswertung der Ergebnisse. Zur Vorhersage der Gewässerbelastung nach niederschlagsbezogenem Oberflächenabfluss wurde in einer Geoinformationsumgebung (GIS) ein Simulationswerkzeug entwickelt. Das Werkzeug arbeitet mit einer sehr exakten Datenbank von hoher räumlicher Auflösung auf Europäischer Ebene. Basierend auf den Erkenntnissen der Experimente, den Ergebnissen der beprobten Gewässer und weiteren Daten von anderen Systemen, die im EU-Life Projekt ArtWET erhoben wurden, ist ein zweites räumliches Werkzeug entstanden, das zur Entscheidungsunterstützung dient und mit dem Risikominderungsmaßnahmen simuliert werden können. Ergebnisse der Experimente und Feldstudien zeigen, dass in experimentellen Feuchtgebieten und bepflanzten Gräben Reduktionen von über 90% der eingetragenen Pestizidkonzentrationen möglich sind. Bepflanzte Gräben und Feuchtgebiete zeigten signifikant bessere Reduktion als unbepflanzte. Pflanzendichte und Sorptivität an organischen Kohlenstoff wurden als Variablen mit der größten Erklärungskraft für die Zielvariable Reduktion der Pestizidkonzentrationen identifiziert (im Gräben-Mesokosmos konnten 65% der Variabilität mit den Variablen Pflanzendichte und KOC erklärt werden. In der Feldstudie wurde gezeigt, dass Fungizidkonzentrationen innerhalb der Rückhaltebecken (Median 38%) und bepflanzten Gräben (Median 56%) signifikant reduziert wurden. Die Regressionsanalyse mit diesen Daten zeigte, dass neben der Pflanzendichte auch die Größe der Systeme Einfluss auf die Reduktion der Pestizidkonzentrationen hat (DP: R²=0.57, p<0.001; VD:
R²=0.19, p<0.001). Die Datenbank für die GIS Werkzeuge wurde mit frei verfügbaren Europäischen Daten aufgebaut. Der erweiterte, von der OECD empfohlene REXTOX Risikoindikator wurde modifiziert und für die Risikomodellierung für alle Agrargewässer auf Europäischer Ebene angewandt. Die Ergebnisse der Risikosimulationen bieten die Datenbasis für das zweite Werkzeug, in dem auch die VTS als Risikominderungsmaßnahme eingearbeitet sind. Die Berechnung der Risikominderungsmaßnahmen kann für die einzelnen Kulturen, ausgewählte Gebiete und unterschiedliche Pestizide durchgeführt werden. Kosten für die Risikominderungsmaßnahmen werden ermittelt. Die Ergebnisse liefern wichtige neue Erkenntnisse zur Nutzung von bepflanzten Systemen als Risikominderungsmaßnahmen für diffuse Pestizideinträge in Agrargewässer. Die Proben der Weinbaugewässer zeigen, dass auch die bisher schlecht untersuchte Gruppe der Fungizide nachteilige Auswirkungen auf aquatische Ökosysteme haben kann. Die entwickelten GIS Werkzeuge sind leicht anwendbar und damit nicht nur als Basis für zukünftige Untersuchungen geeignet, sondern auch als Entscheidungsunterstützung in der praktischen Umsetzung außerhalb der Forschung hilfreich. Auf Europäischer Ebene können die GIS-Werkzeuge einerseits externe Kosten der Gewässerverschmutzung durch diffuse Pflanzenschutzmitteleinträge berechnen, indem die Kosten der unterschiedlichen Risikominderungsmaßnahmen abgeschätzt werden. Andererseits kann die Simulation der Maßnahmen bei der Entscheidungsfindung zur Umsetzung der Vorgaben der Wasserrahmenrichtlinie helfen. Zukünftige Studien sind insbesondere im Bereich der Fungizidbelastung von Oberflächengewässern und der langfristigen Funktionstüchtigkeit von bewachsenen Gräben und Feuchtgebieten als Risikominderungsmaßnahmen notwendig.
Die Verabschiedung der Europäischen Wasserrahmenrichtlinie (WRRL) in 2000 markierte den Beginn einer neuen Ära in der europäischen Wasserpolitik. Mehr als ein Jahrzehnt später, verfehlt jedoch weiterhin die Mehrheit der europäischen Flüsse den guten ökologischen Zustand, eines der wichtigsten WRRL-Ziele.
Ein bedeutender Belastungsfaktor für Fließgewässerökosysteme sind Pflanzenschutzmittel (PSM). Die vorliegende Doktorarbeit unterstreicht die Notwendigkeit, alle wichtigen land-wirtschaftlichen PSM-Quellen und beeinflussenden Landschaftsfaktoren bei der Erstellung von WRRL-Bewirtschaftungsplänen und Maßnahmenprogrammen zu berücksichtigen. Die Ergebnisse und Empfehlungen dieser Doktorarbeit verbessern das Verständnis für eine zielgerichtete Bekämpfung von PSM-Belastungen zur Erreichung der WRRL-Ziele. Insgesamt wurden 663 Messstellen in den Bundesländern Sachsen, Sachsen-Anhalt, Thüringen und Hessen untersucht (Kapitel 3 und 4). Neben einer Analyse der Makrozoobenthos-Daten aus dem WRRL-Monitoringnetz, erfolgte eine detaillierte GIS-Analyse der wichtigsten landwirtschaftlichen PSM-Quellen (Ackerland, Kleingärten sowie kommunale Abwasserreinigungsanlagen) sowie Landschaftsfaktoren (Gewässerrandstreifen und bewaldete Abschnitte im Oberlauf). Basierend auf den Ergebnissen wurde eine Screening-Methode zur schnellen und kostengünstigen Identifizierung von potenziell mit PSM belasteten Stellen entwickelt. Mit Hilfe des Bioindikators SPEARpesticides konnten insektizide Langzeitwirkungen der Abwässer von Abwasserreinigungsanlagen auf die Struktur der Makrozoobenthos-Gemeinschaft bis in 1,5 km Entfernung flussabwärts (in einigen Fällen sogar 3 km) aufgezeigt werden. Die Ergebnisse für den Deutschen Saprobienindex zeigen zudem, dass Abwasserreinigungsanlagen weiterhin eine bedeutende Quelle für sauerstoffzehrende Substanzen sind. Als geeignete Maßnahmen zur Verminderung der Belastung und der Auswirkungen von PSM wurden Gewässerrandstreifen (mindestens 5 m breit) und bewaldete Oberläufe identifiziert.
Es wird befürchtet, dass die zukünftige Ausdehnung des Energiepflanzenanbaus zu einem Anstieg der diffusen PSM-Belastung von Ökosystemen in Agrarlandschaften führen könnte. Diese Fragestellung wurde im Rahmen der vorliegenden Doktorarbeit basierend auf einer Analyse der Entwicklung des Energiepflanzenanbaus in Deutschland und anhand einer Literaturrecherche zu mehrjährigen Energiepflanzen untersucht (Kapitel 5). Die Ergebnisse zeigen, dass eine großflächige Ausdehnung des Energiepflanzenanbaus nicht unbedingt zu einer Erhöhung oder Verringerung der Menge an PSM, die in die Umwelt gelangen, führen muss. Die potenziellen Auswirkungen hängen vielmehr von der zukünftigen Ausgestaltung der Agrarsysteme ab. Anstelle des Anbaus von einjährigen Energiepflanzen in Monokulturen, sollten diese in die bereits vorhandenen Nahrungsmittelanbausysteme integriert werden. Zudem könnten finanzielle Anreize sowie eine verstärkte Aus- und Fortbildung der Bauern dazu beitragen, die Nutzung von nachhaltigen Fruchtfolgen, innovativen Anbausystemen und mehrjährigen Energiepflanzen zu erhöhen. Dies würde die Vielfalt der Feldfrüchte erhöhen und könnte helfen, den PSM-Bedarf der bisherigen intensiven Nahrungsmittelanbausysteme zu verringern.
This thesis examined two specific cases of point and diffuse pollution, pesticides and salinisation, which are two of the most concerning stressors of Germany’s freshwater bodies. The findings of this thesis were organized into three major components, of which the first component presents the contribution of WWTPs to pesticide toxicity (Chapter 2). The second component focuses on the current and future background salt ion concentrations under climate change with the absence of anthropogenic activities (Chapter 3). Finally, the third major component shows the response of invertebrate communities in terms of species turnover to levels of salinity change, considered as a proxy for human-driven salinisation (Chapter 4).
The increasing, anthropogenic demand for chemicals has created large environmental problems with repercussions for the health of the environment, especially aquatic ecosystems. As a result, the awareness of the public and decision makers on the risks from chemical pollution has increased over the past half-century, prompting a large number of studies in the field of ecological toxicology (ecotoxicology). However, the majority of ecotoxicological studies are laboratory based, and the few studies extrapolating toxicological effects in the field are limited to local and regional levels. Chemical risk assessment on large spatial scales remains largely unexplored, and therefore, the potential large-scale effects of chemicals may be overlooked.
To answer ecotoxicological questions, multidisciplinary approaches that transcend classical chemical and toxicological concepts are required. For instance, the current models for toxicity predictions - which are mainly based on the prediction of toxicity for a single compound and species - can be expanded to simultaneously predict the toxicity for different species and compounds. This can be done by integrating chemical concepts such as the physicochemical properties of the compounds with evolutionary concepts such as the similarity of species. This thesis introduces new, multidisciplinary tools for chemical risk assessments, and presents for the first time a chemical risk assessment on the continental scale.
After a brief introduction of the main concepts and objectives of the studies, this thesis starts by presenting a new method for assessing the physiological sensitivity of macroinvertebrate species to heavy metals (Chapter 2). To compare the sensitivity of species to different heavy metals, toxicity data were standardized to account for the different laboratory conditions. These rankings were not significantly different for different heavy metals, allowing the aggregation of physiological sensitivity into a single ranking.
Furthermore, the toxicological data for macroinvertebrates were used as input data to develop and validate prediction models for heavy metal toxicity, which are currently lacking for a wide array of species (Chapter 3). Apart from the toxicity data, the phylogenetic information of species (evolutionary relationships among species) and the physicochemical parameters for heavy metals were used. The constructed models had a good explanatory power for the acute sensitivity of species to heavy metals with the majority of the explained variance attributed to phylogeny. Therefore, the integration of evolutionary concepts (relatedness and similarity of species) with the chemical parameters used in ecotoxicology improved prediction models for species lacking experimental toxicity data. The ultimate goal of the prediction models developed in this thesis is to provide accurate predictions of toxicity for a wide range of species and chemicals, which is a crucial prerequisite for conducting chemical risk assessment.
The latter was conducted for the first time on the continental scale (Chapter 4), by making use of a dataset of 4,000 sites distributed throughout 27 European countries and 91 respective river basins. Organic chemicals were likely to exert acute risks for one in seven sites analyzed, while chronic risk was prominent for almost half of the sites. The calculated risks are potentially underestimated by the limited number of chemicals that are routinely analyzed in monitoring programmes, and a series of other uncertainties related with the limit of quantification, the presence of mixtures, or the potential for sublethal effects not covered by direct toxicity.
Furthermore, chemical risk was related to agricultural and urban areas in the upstream catchments. The analysis of ecological data indicated chemical impacts on the ecological status of the river systems; however, it is difficult to discriminate the effects of chemical pollution from other stressors that river systems are exposed to. To test the hypothesis of multiple stressors, and investigate the relative importance of organic toxicants, a dataset for German streams is used in chapter 5. In that study, the risk from abiotic (habitat degradation, organic chemicals, and nutrients enrichment) and biotic stressors (invasive species) was investigated. The results indicated that more than one stressor influenced almost all sites. Stream size and ecoregions influenced the distribution of risks, e.g., the risks for habitat degradation, organic chemicals and invasive species increased with the stream size; whereas organic chemicals and nutrients were more likely to influence lowland streams. In order to successfully mitigate the effects of pollutants in river systems, co-occurrence of stressors has to be considered. Overall, to successfully apply integrated water management strategies, a framework involving multiple environmental stressors on large spatial scales is necessary. Furthermore, to properly address the current research needs in ecotoxicology, a multidisciplinary approach is necessary which integrates fields such as, toxicology, ecology, chemistry and evolutionary biology.
Statistical eco(-toxico)logy
(2017)
Freshwaters are of immense importance for human well-being.
Nevertheless, they are currently facing unprecedented levels of threat from habitat loss and degradation, overexploitation, invasive species and
pollution.
To prevent risks to aquatic ecosystems, chemical substances, like agricultural pesticides, have to pass environmental risk assessment (ERA) before entering the market.
Concurrently, large-scale environmental monitoring is used for surveillance of biological and chemical conditions in freshwaters.
This thesis examines statistical methods currently used in ERA.
Moreover, it presents a national-scale compilation of chemical monitoring data, an analysis of drivers and dynamics of chemical pollution in streams and, provides a large-scale risk assessment by combination with results from ERA.
Additionally, software tools have been developed to integrate different datasets used in ERA.
The thesis starts with a brief introduction to ERA and environmental monitoring and gives an overview of the objectives of the thesis.
Chapter 2 addresses experimental setups and their statistical analyses using simulations.
The results show that current designs exhibit unacceptably low statistical power, that statistical methods chosen to fit the type of data provide higher power and that statistical practices in ERA need to be revised.
In chapter 3 we compiled all available pesticide monitoring data from Germany.
Hereby, we focused on small streams, similar to those considered in ERA and used threshold concentrations derived during ERA for a large-scale assessment of threats to freshwaters from pesticides.
This compilation resulted in the most comprehensive dataset on pesticide exposure currently available for Germany.
Using state-of-the-art statistical techniques, that explicitly take the limits of quantification into account, we demonstrate that 25% of small streams are at threat from pesticides.
In particular neonicotinoid pesticides are responsible for these threats.
These are associated with agricultural intensity and can be detected even at low levels of agricultural use.
Moreover, our results indicated that current monitoring underestimates pesticide risks, because of a sampling decoupled from precipitation events.
Additionally, we provide a first large-scale study of annual pesticide exposure dynamics.
Chapters 4 and 5 describe software solutions to simplify and accelerate the integration of data from ERA, environmental monitoring and ecotoxicology that is indispensable for the development of landscape-level risk assessment.
Overall, this thesis contributes to the emerging discipline of statistical ecotoxicology and shows that pesticides pose a large-scale threat to small streams.
Environmental monitoring can provide a post-authorisation feedback to ERA.
However, to protect freshwater ecosystems ERA and environmental monitoring need to be further refined and we provide software solutions to utilise existing data for this purpose.
Die heutige Landwirtschaft ist in hohem Maße auf den Einsatz von Pestiziden angewiesen, um verschiedene Schädlinge zu bekämpfen und die Ernteerträge zu maximieren. Trotz detaillierter Vorschriften für den Einsatz von Pestiziden, die auf einem komplexen System der Risikobewertung beruhen, hat sich gezeigt, dass der weit verbreitete Einsatz dieser biologisch aktiven Substanzen eine Gefahr für die Umwelt darstellt. In Oberflächengewässern wurde beobachtet, dass die Pestizidbelastung die als noch umweltverträglich angesehenen Konzentrationen übersteigt und sich negativ auf die Ökologie der Fließgewässer auswirkt, was die Frage aufwirft, ob die derzeitige Risikobewertung einen nachhaltigen Einsatz von Pestiziden gewährleistet. Um diese Frage zu beantworten, hat das umfassende "Kleingewässer-Monitoring" (KgM) in den Jahren 2018 und 2019 das Vorkommen von Pestiziden und die damit verbundenen ökologischen Auswirkungen in 124 Fließgewässern in ganz Deutschland untersucht.
Basierend auf fünf wissenschaftlichen Publikationen, die aus dem KgM hervorgegangen sind, werden in dieser Arbeit die Pestizidbelastung in Fließgewässern, die ökologischen Auswirkungen und die regulatorischen Implikationen bewertet. Mehr als 1000 Wasserproben wurden auf über 100 Pestizid-Analyten untersucht, um das Vorkommen zu charakterisieren (Publikation 1). Die gemessenen Konzentrationen und Auswirkungen wurden zur Validierung der in der Risikobewertung vorhergesagten Umweltkonzentrationen und Wirkungschwellen verwendet (Veröffentlichung 2). Durch die gemeinsame Analyse von realen Pestizidanwendungsdaten und gemessenen Pestizidmischungen in Fließgewässern wurde die Missachtung von Pestizidmischungen in der Umwelt in der Risikobewertung beurteilt (Veröffentlichung 3). Das Risikopotenzial von Mischungen in Fließgewässern wurde zusätzlich mit Hilfe eines Verdachtsscreenings für 395 Chemikalien und einer Batterie von In-vitro-Bioassays untersucht (Publikation 4). Schließlich wurden die Ergebnisse des KgM verwendet, um die Eignung staatlicher Monitoringprogramme zur Identifizierung von Pestizidrisiken in Oberflächengewässern zu bewerten (Publikation 5).
Die Ergebnisse dieser Arbeit zeigen das weit verbreitete Vorkommen von Pestiziden in den Nichtzielökosystemen der Fließgewässer. Die Wasserproben wiesen eine Vielzahl von Pestiziden auf, die in komplexen Mischungen vor allem in kurzzeitigen Spitzenwerten nach Niederschlagsereignissen auftraten (Veröffentlichungen 1 & 4). Die jeweiligen Höchstwerte der Pestizidkonzentration wurden mit dem Rückgang empfindlicher Wirbellosenarten in Verbindung gebracht und überstiegen in etwa 80 % der landwirtschaftlich geprägten Fließgewässer die gesetzlich zulässigen Konzentrationen, welche als Schwellenwerte zum Teil noch als unzureichend für den Schutz der Wirbellosengemeinschaft angesehen wurden (Publikation 2). Das gleichzeitige Vorkommen von Pestiziden in Fließgewässern führte zu einem Risiko, das in der auf eine einzelne Substanzen ausgerichteten Risikobewertung in realistischen Worst-Case-Szenarien um einen Faktor von etwa 3,2 unterschätzt wurde. Dies wird durch die hohe Häufigkeit, mit der Nichtzielorganismen den Pestiziden ausgesetzt sind, weiter verstärkt (Veröffentlichung 3). Wasserproben, die nach Regenfällen entnommen wurden, verursachten in den Bioassays deutliche Effekte, die nur zu einem geringen Teil durch die vielen detektierten Analyten erklärbar waren, was auf die Relevanz unbekannter chemischer oder biologischer Mischungskomponenten hinweist (Publikation 4). Schließlich wurde festgestellt, dass die behördliche Überwachung von Oberflächengewässern gemäß der Wasserrahmenrichtlinie (WRRL) die Risiken von Pestiziden erheblich unterschätzt, da hier etwa drei Viertel der kritischen Pestizide und mehr als die Hälfte der gefährdeten Gewässer übersehen worden wären (Veröffentlichung 5).
Im Wesentlichen liefert diese Arbeit eine neue Ebene der Validierung der Risikobewertung von Pestiziden in aquatischen Ökosystemen, indem das Auftreten von Pestiziden und ihre Auswirkungen auf die Umwelt in einem bisher einzigartigen Maßstab bewertet werden. Die Ergebnisse zeigen generell, dass der derzeitige landwirtschaftliche Einsatz von Pestiziden zu erheblichen Auswirkungen auf die Fließgewässerökologie führt, die über das von der Risikobewertung tolerierte Maß hinausgehen. In dieser Arbeit wurden die Unterschätzung der Pestizidexposition, die potenzielle Unzulänglichkeit der gesetzlichen Schwellenwerte und die allgemeine Trägheit des Zulassungsverfahrens als Hauptursachen dafür ermittelt, dass entsprechende gesetzlich verankerte, ökologische Zielsetzungen momentan erwiesenermaßen nicht erreicht werden. Um einen nachhaltigen Einsatz von Pestiziden zu gewährleisten, schlägt die Arbeit wesentliche Änderungen der Risikobewertung vor. Monitoringprogramme wie das KgM, die über die derzeitigen staatlichen Überwachungsbemühungen hinausgehen, werden weiterhin erforderlich sein, um die Regulierungsbehörden für Pestizide ständig über die Gültigkeit ihrer prospektiven Risikobewertung zu informieren, die immer mit Unsicherheiten behaftet sein wird.
Despite the significant presence of neuroactive substances in the environment, bioassays that allow to detect diverse groups of neuroactive mechanisms of action are not well developed and not properly integrated into environmental monitoring and chemical regulation. Therefore, there is a need to develop testing methods which are amenable for fast and high-throughput neurotoxicity testing. The overall goal of this thesis work is to develop a test method for the toxicological characterization and screening of neuroactive substances and their mixtures which could be used for prospective and diagnostic hazard assessment.
In this thesis, the behavior of zebrafish embryos was explored as a promising tool to distinguish between different neuroactive mechanisms of action. Recently, new behavioral tests have been developed including photomotor response (PMR), locomotor response (LMR) and spontaneous tail coiling (STC) tests. However, the experimental parameters of these tests lack consistency in protocols such as exposure time, imaging time, age of exposure, endpoint parameter etc. To understand how experimental parameters may influence the toxicological interpretation of behavior tests, a systematic review of existing behavioral assays was conducted in Chapter 2. Results show that exposure concentration and exposure duration highly influenced the comparability between different test methods and the spontaneous tail coiling (STC) test was selected for further testing based on its relative higher sensitivity and capacity to detect neuroactive substances (Chapter 2).
STC is the first observable motor activity generated by the developing neural network of the embryo which is assumed to occur as a result of the innervation of the muscle by the primary motor neurons. Therefore, STC could be a useful endpoint to detect effect on the muscle innervation and also the on the whole nervous system. Consequently, important parameters of the STC test were optimized and an automated workflow to evaluate the STC with the open access software KNIME® was developed (Chapter 3).
To appropriately interpret the observed effect of a single chemical and especially mixture effects, requires the understanding of toxicokinetics and biotransformation. Most importantly, the biotransformation capacity of zebrafish embryos might be limited and this could be a challenge for assessment of chemicals such as organophosphates which require a bioactivation step to effectively inhibit the acetylcholinesterase (AChE) enzyme. Therefore, the influence of the potential limited biotransformation on the toxicity pathway of a typical organophosphate, chlorpyrifos, was investigated in Chapter 5. Chlorpyrifos could not inhibit AChE and this was attributed to possible lack of biotransformation in 24 hpf embryos (Chapter 5).
Since neuroactive substances occur in the environment as mixtures, it is therefore more realistic to assess their combined effect rather than individually. Therefore, mixture toxicity was predicted using the concentration addition and independent action models. Result shows that mixtures of neuroactive substances with different mechanisms of action but similar effects can be predicted with concentration addition and independent action (Chapter 4). Apart
from being able to predict the combined effect of neuroactive substances for prospective risk assessment, it is also important to assess in retrospect the combined neurotoxic effect of environmental samples since neuroactive substances are the largest group of chemicals occurring in the environment. In Chapter 6, the STC test was found to be capable of detecting neurotoxic effects of a wastewater effluent sample. Hence, the STC test is proposed as an effect based tool for monitoring environmental acute and neurotoxic effects.
Overall, this thesis shows the utility and versatility of zebrafish embryo behavior testing for screening neuroactive substances and this allows to propose its use for prospective and diagnostic hazard assessment. This will enhance the move away from expensive and demanding animal testing. The information contained in this thesis is of great potential to provide precautionary solutions, not only for the exposure of humans to neuroactive chemicals but for the environment at large.