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- Aquatic Guidance Document (1)
- Bestäubung (1)
- Biodiversität (1)
- Environmental organic chemistry (1)
- Micropollutants (1)
- Natürliche Schädlingskontrolle (1)
- Nährstoffverfügbarkeit (1)
- Staubewässerung (1)
- Transformation products (1)
- Wastewater (1)
The Web contains some extremely valuable information; however, often poor quality, inaccurate, irrelevant or fraudulent information can also be found. With the increasing amount of data available, it is becoming more and more difficult to distinguish truth from speculation on the Web. One of the most, if not the most, important criterion used to evaluate data credibility is the information source, i.e., the data origin. Trust in the information source is a valuable currency users have to evaluate such data. Data popularity, recency (or the time of validity), reliability, or vagueness ascribed to the data may also help users to judge the validity and appropriateness of information sources. We call this knowledge derived from the data the provenance of the data. Provenance is an important aspect of the Web. It is essential in identifying the suitability, veracity, and reliability of information, and in deciding whether information is to be trusted, reused, or even integrated with other information sources. Therefore, models and frameworks for representing, managing, and using provenance in the realm of Semantic Web technologies and applications are critically required. This thesis highlights the benefits of the use of provenance in different Web applications and scenarios. In particular, it presents management frameworks for querying and reasoning in the Semantic Web with provenance, and presents a collection of Semantic Web tools that explore provenance information when ranking and updating caches of Web data. To begin, this thesis discusses a highly exible and generic approach to the treatment of provenance when querying RDF datasets. The approach re-uses existing RDF modeling possibilities in order to represent provenance. It extends SPARQL query processing in such a way that given a SPARQL query for data, one may request provenance without modifying it. The use of provenance within SPARQL queries helps users to understand how RDF facts arederived, i.e., it describes the data and the operations used to produce the derived facts. Turning to more expressive Semantic Web data models, an optimized algorithm for reasoning and debugging OWL ontologies with provenance is presented. Typical reasoning tasks over an expressive Description Logic (e.g., using tableau methods to perform consistency checking, instance checking, satisfiability checking, and so on) are in the worst case doubly exponential, and in practice are often likewise very expensive. With the algorithm described in this thesis, however, one can efficiently reason in OWL ontologies with provenance, i.e., provenance is efficiently combined and propagated within the reasoning process. Users can use the derived provenance information to judge the reliability of inferences and to find errors in the ontology. Next, this thesis tackles the problem of providing to Web users the right content at the right time. The challenge is to efficiently rank a stream of messages based on user preferences. Provenance is used to represent preferences, i.e., the user defines his preferences over the messages' popularity, recency, etc. This information is then aggregated to obtain a joint ranking. The aggregation problem is related to the problem of preference aggregation in Social Choice Theory. The traditional problem formulation of preference aggregation assumes a I fixed set of preference orders and a fixed set of domain elements (e.g. messages). This work, however, investigates how an aggregated preference order has to be updated when the domain is dynamic, i.e., the aggregation approach ranks messages 'on the y' as the message passes through the system. Consequently, this thesis presents computational approaches for online preference aggregation that handle the dynamic setting more efficiently than standard ones. Lastly, this thesis addresses the scenario of caching data from the Linked Open Data (LOD) cloud. Data on the LOD cloud changes frequently and applications relying on that data - by pre-fetching data from the Web and storing local copies of it in a cache - need to continually update their caches. In order to make best use of the resources (e.g., network bandwidth for fetching data, and computation time) available, it is vital to choose a good strategy to know when to fetch data from which data source. A strategy to cope with data changes is to check for provenance. Provenance information delivered by LOD sources can denote when the resource on the Web has been changed last. Linked Data applications can benefit from this piece of information since simply checking on it may help users decide which sources need to be updated. For this purpose, this work describes an investigation of the availability and reliability of provenance information in the Linked Data sources. Another strategy for capturing data changes is to exploit provenance in a time-dependent function. Such a function should measure the frequency of the changes of LOD sources. This work describes, therefore, an approach to the analysis of data dynamics, i.e., the analysis of the change behavior of Linked Data sources over time, followed by the investigation of different scheduling update strategies to keep local LOD caches up-to-date. This thesis aims to prove the importance and benefits of the use of provenance in different Web applications and scenarios. The exibility of the approaches presented, combined with their high scalability, make this thesis a possible building block for the Semantic Web proof layer cake - the layer of provenance knowledge.
Grünland in Europa wurde über die Jahrhunderte hinweg durch steigende Intensivierung der Landnutzung geprägt. Die agrarischen Veränderungen und Weiterentwicklungen formten und veränderten die Biodiversität und führten letztlich zu massivem Artenrückgang. Heutzutage ist davon auszugehen, dass die planetare Belastungsgrenze für die globale Biodiversität und insbesondere die Biodiversität von Grünland bereits erreicht wurde. Politische Entscheidungsträger und Umweltschützer suchen daher Maßnahmen, die den agrarökonomischen Zweck der Biomasseproduktion mit dem Schutz und Erhalt von Biodiversität sowie der Aufrechterhaltung von Ökosystemprozessen vereinen. In früheren Zeiten und insbesondere vor der Einführung mineralischer Stickstoffdünger war Landnutzung im Wesentlichen von den strukturellen Gegebenheiten der Landschaft abhängig. Die Entwicklung regionalspezifischer Bewirtschaftungsmaßnahmen förderte durch die Schaffung von Habitaten für speziell angepasste Arten und Artenzusammensetzungen eine hohe Diversität auf Landschaftsebene.
Staubewässerung war seit dem frühen Mittelalter bis ins 20. Jahrhundert eine europaweit verbreitete Bewirtschaftungsmaßnahme zur Ertragssteigerung. Diese Form der Bewässerung, bei der angrenzende Flüsse systematisch aufgestaut werden, um das Wasser in die Wiesen zu leiten und durch im Wasser geführte Sedimente einen Düngeeffekt hervorzurufen, war typisch für Wiesenbewirtschaftung im Flachland. Abhängig von den strukturellen Gegebenheiten wurden regionaltypische Abwandlungen der Bewässerungssysteme entwickelt und prägten somit die Flora und Fauna dieser sogenannten Wässerwiesen. Mineralische Dünger machten diese arbeitsintensive Bewirtschaftungsform weitestgehend unprofitabel, sodass diese heutzutage nur noch in wenigen Regionen reliktartig als Tradition erhalten blieb.
In den Queichwiesen nahe Landau in der Pfalz wird mit zwischenzeitlichen Unterbrechungen seit dem 15. Jahrhundert traditionelle Staubewässerung betrieben. Die vorliegende Studie nutzte die Queichwiesen als Modellregion, um sowohl Langzeit- als auch Kurzzeiteffekte der Staubewässerung auf die Biodiversität und Nährstoffverfügbarkeit zu
untersuchen. In einer umfassenden Vegetationskartierung konnten wir einen positiven Effekt der Bewässerung auf die Diversität sowohl auf lokaler als auch auf Landschaftsebeneverzeichnen. Eine höhere strukturelle Vielfalt durch die Förderung niedrigwüchsiger Arten legt zwar einen positiven Effekt auf die Diversität von Arthropoden (Orthodoptera, Carabidae, Spinnen) nahe, dieser konnte jedoch nicht gefunden werden. Nichtsdestotrotz zeigten sich die bewässerten Wiesen als ökologisch bedeutsames Habitat für Arthropodenarten feuchter Biotope. In einem kombinierten Labor- und Feldexperiment untersuchten wir die Veränderung der Nährstoffverfügbarkeit durch Bewässerung. Zwar ist heutzutage nicht mehr von einem
direkten Düngeeffekt durch im Wasser geführte Schlacken auszugehen, aber dennoch zeigte sich ein indirekter Düngeeffekt der Bewässerung durch eine kurzzeitig stark erhöhte Pflanzenverfügbarkeit von Makro- und Mikronährstoffen. Die Ausprägung dieses Nährstoffpeaks und somit die Ausnutzung des sekundären Düngeeffekts zeigte eine graduelle Abhängigkeit auf Artebene, die eine spezifische Vegetationsentwicklung durch die Bewässerung untermauern. Diese Resultate legen daher nahe, dass Staubewässerung von Wiesen eine extensive Bewirtschaftungsform ist, die Biodiversität auf verschiedenen Skalenebenen fördert und gleichzeitig den Einsatz von Düngern reduzieren kann. Die Abstimmung von Düngung und Bewässerung bedarf jedoch der lokalspezifischen Evaluation abiotischer und biotischer Gegebenheiten.
Introduction:
In March 2012 a secessionist-Islamist insurgency gained momentum in Mali and quickly took control of two-thirds of the state territory. Within weeks radical Islamists, drug smugglers and rebels suddenly ruled over a territory bigger than Germany. News of the abuse of the population and the introduction of harsh Sharia law spread soon, and word got out that the Malian Army had simply abandoned the land. The general echo of the IC was surprise, a reaction that was, as this research will show, as unfunded as it was unconstructive*. When Malian state structures collapsed, the world watched in shock, even though the developments couldhave been anticipated –and prevented. Ultimately, the situation had to be resolved by international forces (most notably French troops), who are still in Mali at the time of writing (Arieff 2013a: 5; Lohmann 2012: 3; Walther and Christopoulos 2015: 514f.; Shaw 2013: 204; Qantara, Interview, 2012;L’Express, Mali, 2015; Deutscher Bundestag, MINUSMA und EUTM Mali, 2016; UN, MUNISMA, 2016; Boeke and Schuurmann 2015: 801; Chivvis 2016: 93f.).
This research will show that the developments in Mali in 2012 have been developing for a long time and could have been avoided. In doing so, it will also show why state security can never be analyzed or consolidated in an isolated manner. Instead, it is necessary to take into account regional dynamics and developments in order to find a comprehensive approach to security in individual states. Once state failure occurs, not only does the state itself fail, but the surrounding region equally failed to prevent the failure.
Weak states are a growing concern in many world regions, particularly in Africa. As international intervention often proves unsustainable for various reasons*, the author believes that states which cannot stabilize themselves need a regional agent to support them. This regional agent should be a Regional Security Complex (RSC) asdefined by Barry Buzan and Ole Waever (Buzan and Waever 2003). As the following analysis will show, Mali is a case in point. The hope is that this study will help avoid similar failures in the future by making a strong case for the establishment of RSC’s.
…
For a comprehensive understanding of evolutionary processes and for providing reliable prognoses about the future consequences of environmental change, it is essential to reveal the genetic basis underlying adaptive responses. The importance of this goal increases in light of ongoing climate change, which confronts organisms worldwide with new selection pressures and requires rapid evolutionary change to avoid local extinction. Thereby, freshwater ectotherms like daphnids are particularly threatened. Unraveling the genetic basis of local adaptation is complicated by the interplay of forces affecting patterns of genetic divergence among populations. Due to their key position in freshwater communities, cyclic parthenogenetic mode of reproduction and resting propagules (which form biological archives), daphnids are particularly suited for this purpose.
The aim of this thesis was to assess the impact of local thermal selection on the Daphnia longispina complex and to reveal the underlying genetic loci. Therefore, I compared genetic differentiation among populations containing Daphnia galeata, Daphnia longispina and their interspecific hybrids across time, space, and species boundaries. I revealed strongly contrasting patterns of genetic differentiation between selectively neutral and functional candidate gene markers, between the two species, and among samples from different lakes, suggesting (together with a correlation with habitat temperatures) local thermal selection acting on candidate gene TRY5F and indicating adaptive introgression. To reveal the candidate genes’ impact on fitness, I performed association analyses among data on genotypes and phenotypic traits of D. galeata clones from seven populations. The tests revealed a general temperature effect as well as inter-population differences in phenotypic traits and imply a possible contribution of the candidate genes to life-history traits. Finally, utilizing a combined population transcriptomic and reverse ecology approach, I introduced a methodology with a wide range of applications in evolutionary biology and revealed that local thermal selection was probably a minor force in shaping sequence and gene expression divergence among four D. galeata populations, but contributed to sequence divergence among two populations. I identified many transcripts possibly under selection or contributing strongly to population divergence, a large amount thereof putatively under local thermal selection, and showed that genetic and gene expression variation is not depleted specifically in temperature-related candidate genes.
In conclusion, I detected signs of local adaptation in the D. longispina complex across space, time, and species barriers. Populations and species remained genetically divergent, although increased gene flow possibly contributed, together with genotypes recruited from the resting egg bank, to the maintenance of standing genetic variation. Further work is required to accurately determine the influence of introgression and the effects of candidate genes on individual fitness. While I found no evidence suggesting a response to intense local thermal selection, the high resilience and adaptive potential regarding environmental change I observed suggest positive future prospects for the populations of the D. longispina complex. However, overall, due to the continuing environmental degradation, daphnids and other aquatic invertebrates remain vulnerable and threatened.
Natürliche Schädlingskontrolle und Bestäubung sind wichtige Ökosystemdienstleistungen für die Landwirtschaft. Diese können durch ökologische Landwirtschaft und naturnahe Lebensräume in der näheren oder weiteren Umgebung gefördert werden.
Das Potential naturnaher Lebensräume räuberische Fliegen(Kapitel 2 und 3)und Bienen (Kapitel 7) auf lokaler und Landschaftsebene zu fördern wurde in naturnahen Lebensräumen untersucht. Räuberische Fliegen bevorzugten verholzte Habitate und reagierten positiv auf die andschaftskomplexizität. Die Vielfalt von Bienen und die Häufigkeit von Honig- und Wildbienen in den naturnahen Lebensräumen wurde vor allem positiv von den vorhandenen Blütenressourcen beeinflusst.
Der Einfluss von ökologischer Landwirtschaft, angrenzenden naturnahen Lebensräumen und Landschaftskomplexizität auf natürliche Schädlingskontrolle (Kapitel 4) und Bestäubung (Kapitel 6) wurde in 18 Kürbisfeldern untersucht. Ökologische Landwirtschaft hatte keine starken Effekte auf die natürliche Schädlingskontrolle oder die Bestäubung von Kürbis. Die natürliche Schädlingskontrolle kann vor allem lokal durch das Blütenangebot in den angrenzenden Lebensräumen gefördert werden, weil dieses die Dichten der natürlichen Läusefeinde positiv beeinflusste und tendenziell die Läusedichte in den Kürbisfeldern reduzierte.
Kürbis ist ein beeindruckendes Beispiel für eine Schlüsselrolle von Wildbienen für den Bestäubungserfolg, weil Kürbis in Deutschland vor allem von Hummeln bestäubt wird trotz der höheren Besuchsdichten von Honigbienen. Die Bestäubung kann am besten durch Landschaftskomplexizität gefördert werden. Die Anzahl von Blütenbesuchen von Hummeln und infolgedessen auch die übertragene Pollenmenge wurden negativ von der landwirtschaftlich genutzten Fläche in der umgebenden Landschaft beeinflusst.
Der Einfluss von Läusedichten (Kapitel 8) und Bestäubung (Kapitel 5) auf den Kürbisertrag wurde ermittelt. Der Kürbisertrag wurde nicht beeinflusst von den beobachteten Läusedichten und war nicht bestäubungslimitiert bei der derzeitigen Menge an Bienenbesuchen.
Insbesondere naturnahe Lebensräume, die stetige und vielfältige Blütenressourcen bereitstellen, sind wichtig für Schädlingskontrolleure und Bestäuber. In Agrarlandschaften sollte ein ausreichender Anteil an verschiedenen Typen von naturnahen Lebensräumen erhalten und wiederhergestellt werden. Dadurch können natürliche Schädlingskontrolleure wie räuberische Fliegen, Bestäuber wie Hummeln,und die von ihnen geleistete Schädlingskontrolle und Bestäubung in Agrarlandschaften gefördert werden.
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 Anwendung von Chemikalien führt in vielen Fällen zu deren Emission in die Umwelt. Besonders organische Substanzen wie zum Beispiel Pharmazeutika, Biozide und Waschmittelinhaltsstoffe wurden in den letzten Jahren vermehrt als Umweltkontaminanten in Oberflächengewässern nachgewiesen. Die organischen Umweltkontaminanten, auch Spurenstoffe genannt, haben oftmals i) unbekannte ökotoxikologische Wirkungen, ii) unbekannte Verteilungsverhalten, und iii) sind bisher hinsichtlich der Emission kaum reguliert. Wie bei allen Substanzen können Spurenstoffe in der Umweltmatrix und insbesondere auch in der Kläranlage zu sogenannten Transformationsprodukten (TPs) umgewandelt werden. Um den durch Spurenstoffe verursachten Herausforderungen technologisch begegnen zu können, wird ein besseres Verständnis über diese Transformationsprozesse benötigt. Diese Dissertationsarbeit befasst sich deshalb mit der Aufklärung von Transformationsprozessen ausgewählter Spurenstoffe während der biologischen Abwasserreinigung.
Für die Untersuchung des Abbaus von Trimethoprim wurden Inkubationsversuche angewendet und die Auswirkung der steigenden Dotierungskonzentrationen systematisch untersucht. Es wurden insgesamt sechs TPs charakterisiert. Die Dotierungskonzentration hatte sowohl Auswirkungen auf die kinetischen Konstanten, als auch auf die Transformationsreaktionen. Ein solcher Einfluss der experimentellen Bedingungen wurde bisher in der Literatur noch nicht berichtet. Nur bei niedriger Dotierungskonzentration wurde am Ende des Transformationswegs ein stabiles TP gebildet, die 2,4-Diaminopyrimidin-5-carbonsäure (DAPC). Diese Substanz konnte in Laborversuchen den Großteil der abgebauten Menge von Trimethoprim erklären. Durch Untersuchungen an einer Referenzkläranlage konnte festgestellt werden, dass nur die Inkubationsversuche bei niedriger Dotierungskonzentration die realen Prozesse adäquat abbilden konnten. Die Anwendung hoher Dotierungskonzentrationen führte in Laborversuchen zu einer veränderten TP-Bildung.
Drei phenolische Spurenstoffe wurden in Bezug auf ihre Transformation, insbesondere hin zu potenziell toxischen nitrophenolischen TPs, untersucht: das Desinfektionsmittel ortho-Phenylphenol (OPP), das Kunststoffadditiv Bisphenol-A (BPA) und das Hustenmittel Dextrorphan. Nitrit wurde als ein potenzieller Auslöser für die Nitrierung postuliert. Inkubationsversuche in Reinstwasser wurden mit OPP in Anwesenheit von Nitrit durchgeführt und bestätigten, dass nitro-(und nitroso-) phenolische TPs unter leicht sauren Bedingungen gebildet werden. Da in kommunalen Kläranlagen der pH-Wert in Belebtschlamm zumeist zwischen 7,5 und 8,5 liegt und Nitrit als Zwischenprodukt oft nur in niedrigen Konzentration vorhanden ist, wurde die Bildung von signifikanten Konzentrationen nitrophenolischer TPs als unwahrscheinlich eingestuft. Aufgrund der Ergebnisse von Inkubationsversuchen mit inokulierten Belebtschlamm war festzustellen, dass die drei untersuchten Spurenstoffe schnell zu biologischen TPs umgewandelt wurden. Die Studie zeigte wie das Bildungspotenzial von nitrophenolischen TPs gesteigert wird, wenn bestimmte Bedingungen im Belebtschlamm vorliegen: saurer pH und erhöhte Nitritkonzentration. Zudem wurde auch gezeigt, dass die Bildung von nitrophenolischen TPs durch das Ansäuern oder das Einfrieren von Proben initiiert werden kann.
Die Transformation vom Antiphlogistikum Diclofenac wurde in zwei unterschiedlichen Kläranlagen verglichen. Die erste Kläranlage verwendet Aufwuchskörper für ein verstärktes Biofilmwachstum, während die zweite mit einer konventionellen nitrifizierenden Belebtschlammbehandlung ausgestattet ist. Trotz der unterschiedlichen Behandlungstechniken konnten in beiden Fällen ähnliche Transformationsreaktionen festgestellt werden. Der wesentliche Unterschied bestand in den veränderten Kinetiken: Geschwindigkeitskonstanten (kbiol) waren ca. 50 Mal höher in Kontakt mit Aufwuchskörpern als im konventionellen Belebtschlamm. Der Transformationsweg führte zur Bildung einer Vielzahl an gering konzentrierten TPs. Monitoring-Kampagnen an den zwei Kläranlagen wurden zur Bestätigung der Ergebnisse angeschlossen. In der konventionellen Kläranlage wurde keine signifikante Diclofenac Entfernung gemessen. Wohingegen im Aufwuchskörperreaktor eine mittlere Entfernung von 88% gemessen wurde. Damit wäre die vorgeschlagene Umweltqualitätsnorm von 0.05 μg/L möglicherweise auch ohne die Anwendung von weiteren Behandlungsschritten wie z.B. Aktivkohlefiltration oder Ozonung erreichbar.
The European weatherfish (Misgurnus fossilis) is a benthic freshwater fish species belonging to the family Cobitidae, that is subjected to a considerable decline in many regions across its original distribution range. Due to its cryptic behavior and low economic value, the causes of threat to weatherfish remained partly unknown and the species is rarely at the center of conservation efforts. In order to address these concerns, the overall aim of the present thesis was to provide a comprehensive approach for weatherfish conservation, including the development of stocking measures, investigations on the species autecology and the evaluation of potential threats. The first objective was to devise and implement a regional reintroduction and stock enhancement program with hatchery-reared weatherfish in Germany. Within this program (2014-2016), a total number of 168,500 juvenile weatherfish were stocked to seven water systems. Recaptures of 45 individuals at two reintroduction sites supported the conclusion that the developed stocking strategy was appropriate. In order to broaden the knowledge about weatherfish autecology and thereby refining the rearing conditions and the selection of appropriate stocking waters, the second objective was to investigate the thermal requirements of weatherfish larvae. Here, the obtained results revealed that temperatures higher than previously suggested were tolerated by larvae, whereas low temperatures within the range of likely habitat conditions increased mortality rates. As weatherfish can be frequently found in agriculturally impacted waters (e.g. ditch systems), they are assumed to have an increased probability to be exposed to chemical stress. Since the resulting risk has not yet been investigated with a focus on weatherfish, the third objective was to provide a methodical foundation for toxicity testing that additionally complies with the requirements of alternative test methods. For this purpose, the acute fish embryo toxicity test was successfully transferred to weatherfish and first results exhibited that sensitivity of weatherfish towards a tested reference substance (3,4-dichloroaniline) was highest compared to other species. On the basis of these findings, the fourth objective was to apply weatherfish embryos for multiple sediment bioassays in order to investigate teratogenic effects derived from sediment-associated contaminants. In this context, weatherfish revealed particular sensitivity to water extractable substances, indicating that sediment contamination might pose a considerable risk. Moreover, as an endangered benthic fish species with high ecological relevance for European waters that are specifically exposed to hazardous contaminants, the weatherfish might be a prospective species for an ecological risk assessment of sediment toxicity. Overall, the present thesis contributed to the conservation of weatherfish by considering a variety of aspects that interact and reinforce one another in order to achieve improvements for the species situation.
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.
Key mechanisms for the release of metal(loid)s from a construction material in hydraulic engineering
(2017)
Hydraulic engineering and thus construction materials are necessary to enable the navigability of water ways. Since, a variety of natural as well as artificial materials are used, this materials are world wide tested on a potential release of dangerous substances to prevent adverse effects on the environment. To determine the potential release, it is important to identify and to understand key mechanisms which are decisive for the release of hazardous substances. A limited correlation between the conditions used in regulatory tests and those found in environmental systems is given and hence, often the significance of results from standardised tests on construction materials is questioned, since they are not designed to mimic environmental conditions.
In Germany industrial by-products are used as armour stones in hydraulic engineering. Especially the by-product copper slag is used during the last 40 years for the construction of embankments, groynes and coastal protection. On the one hand, this material has a high density and natural resources (landscape) are protected. One the other hand, the material contains high quantities of metal(loid)s. Therefore the copper slag (product name: iron silicate stones) is very suitable as test material. Metal(loid)s examined were As, Sb and Mo as representatives for (hydr)oxide forming elements and Cd, Co, Cu, Fe, Ni, Pb and Zn were studied as representatives for elements forming cations during the release.
Questions addressed in this Thesis were: (i) can we transfer the results from batch experiments to construction scenarios under the prevalent environmental conditions, (ii) which long-term trends exist for the release of metal(loid)s from copper slags and (iii) how environmental conditions influence the leaching of metal(loid)s from water construction materials?
To answer the first question the surface depending release of the metal(loid)s from the construction materials was examined. Therefore, batch leaching experiments with different particle sizes and a constant liquid/solid ratio were performed. In a second step a comparison between different methods for the determination of the specific surface area of armour stones with a 3D laser scanning method as a reference were performed. In a last step it was possible to show that via a roughness factor the results of the specific surface area from small stones, measured with gas adsorption, can be connected with the results from armour stones, determined with an aluminium foil method. Based on calculations of the specific surface area, it was possible to significantly improve catchment scale calculation about the release of metal(loid)s and to evaluate a potential impact of construction materials in hydraulic engineering on the water chemistry of rivers and streams.
To answer the second question long-term leaching diffuse gradient in thin films supported experiments were performed for half a year. Diffuse gradients in thin films (DGT) is an in situ method to passive sample metal(loid)s in water, sediments and soils. They were used as a sink for metal(loid)s in the eluate to provide solution equilibriums. Thus the exchange of the eluent, which is performed normally in long-term experiments, was superfluous and long-term effects under undisturbed conditions were studied. The long-term leaching experiments with DGT have proven to be capable (i) to differentiate between the depletion of the material surface and the solution equilibriums and (ii) to study sorption processes with or without a further release of the analytes. This means for the practically relevant test material copper slag that: (i) the cations Cd, Co, Cu, Ni and Pb are confirmed to be released from the slag over the whole time period of six months, (ii) a surface depletion of Zn was detected, and (iii) that the (hydr)oxide forming elements As, Mo and Sb were released from the slag over the hole periods of six months but the release was masked by adsorption to Fe-oxide colloids, which were formed during the leaching experiments. It was confirmed, that sulphide minerals are the main source for long-term release of Cd, Cu, Ni, Pb and Mo.
To answer the third question short-term leaching experiments simulating environmental conditions in hydraulic engineering were performed. One factor is the salinity. The influence of this parameter was tested in batch experiments with sea salt solution (30 g/l), river Rhine water, ultra pure water and in addition with different NaCl concentration (5, 10, 20 and 30 g/l). In general, the ionic strength is an important factor for the metal(loid) release but the composition of the water (e.g. the HCO3- content) may superimpose this effect. Therefore, the concentrations of the metal(loid)s in the experiments with ultra-pure water spiked with sea salt or native river water and the ultra-pure water spiked with NaCl were significantly different. In a second experiment the influence of the environmental parameters and the interactions between the environmental parameters pH (4–10), sediment content (0 g–3.75 g), temperature (4 °C–36 °C) and ionic strength (0 g/l–30 g/l NaCl) on the release of metal(loid)s from the test material was examined. The statistical Design of Experiments (DoE) was used to study the influence of these factors as well as their interactions. All studied factors may impact the release of metal(loid)s from the test material to the eluent, whereas the release and the partitioning between sediment and eluate of metal(loid)s was impacted by interactions between the studied factors. The main processes were sorption, complexation, solubility, buffering and ion exchange. In addition, by separating the sediment from the slag after the experiments by magnetic separation, the enrichment of metal(loid)s in the sediment was visible. Thus, the sediment was the most important factor for the release of the metal(loid)s, via pH, temperature and ionic strength, because the sediment acted as a sink.
Agricultural land-use may lead to brief pulse exposures of pesticides in edge-of-field streams, potentially resulting in adverse effects on aquatic macrophytes, invertebrates and ecosystem functions. The higher tier risk assessment is mainly based on pond mesocosms which are not designed to mimic stream-typical conditions. Relatively little is known on exposure and effect assessment using stream mesocosms.
Thus the present thesis evaluates the appliacability of the stream mesocosms to mimic stream-typical pulse exposures, to assess resulting effects on flora and fauna and to evaluate aquatic-terrestrial food web coupling. The first objective was to mimic stream-typical pulse exposure scenarios with different durations (≤ 1 to ≥ 24 hours). These exposure scenarios established using a fluorescence tracer were the methodological basis for the effect assessment of an herbicide and an insecticide. In order to evaluate the applicability of stream mesocosms for regulatory purposes, the second objective was to assess effects on two aquatic macrophytes following a 24-h pulse exposure with the herbicide iofensulfuron-sodium (1, 3, 10 and 30 µg/L; n = 3). Growth inhibition of up to 66 and 45% was observed for the total shoot length of Myriophyllum spicatum and Elodea canadensis, respectively. Recovery of this endpoint could be demonstrated within 42 days for both macrophytes. The third objective was to assess effects on structural and functional endpoints following a 6-h pulse exposure of the pyrethroid ether etofenprox (0.05, 0.5 and 5 µg/L; n = 4). The most sensitive structural (abundance of Cloeon simile) and functional (feeding rates of Asellus aquaticus) endpoint revealed significant effects at 0.05 µg/L etofenprox. This concentration was below field-measured etofenprox concentrations and thus suggests that pulse exposures adversely affect invertebrate populations and ecosystem functions in streams. Such pollutions of streams may also result in decreased emergence of aquatic insects and potentially lead to an insect-mediated transfer of pollutants to adjacent food webs. Test systems capable to assess aquatic-terrestrial effects are not yet integrated in mesocosm approaches but might be of interest for substances with bioaccumulation potential. Here, the fourth part provides an aquatic-terrestrial model ecosystem capable to assess cross-ecosystem effects. Information on the riparian food web such as the contribution of aquatic (up to 71%) and terrestrial (up to 29%) insect prey to the diet of the riparian spider Tetragnatha extensa was assessed via stable isotope ratios (δ13C and δ15N). Thus, the present thesis provides the methodological basis to assess aquatic-terrestrial pollutant transfer and effects on the riparian food web.
Overall the results of this thesis indicate, that stream mesocosms can be used to mimic stream-typical pulse exposures of pesticides, to assess resulting effects on macrophytes and invertebrates within prospective environmental risk assessment (ERA) and to evaluate changes in riparian food webs.
Die Verwendung physiologischer Indikatoren, welche die Reaktion von Organismen auf Veränderungen ihrer Umwelt widerspiegeln, bietet ein großes Potenzial für ökologische Studien. Durch die Analyse des physiologischen Zustandes von Organismen ermöglichen diese Indikatoren eine schnellere Erfassung von Veränderungen in aquatischen Ökosystemen als es durch die Betrachtung ökologischer Indikatoren, wie z. B. der Struktur der Benthosgemeinschaft oder des Reproduktionserfolges einzelner Arten, möglich ist. Dieser Zeitvorteil kann sowohl die Effektivität der Habitatbewertung als auch experimenteller Studien in der aquatischen Ökologie erhöhen. In diesem Zusammenhang konzentriert sich die vorliegende Arbeit auf physiologische Messgrößen, wie die Konzentration von Energiespeicherstoffen, den zellulären Energiestatus (Adenylate Energy Charge) oder die Stoffwechselaktivität in vivo, die den energetischen Zustand oder den aktuellen Energieverbrauch von Organismen charakterisieren, sowie auf das RNA:DNA-Verhältnis als Wachstumsindikator. Obwohl diese Indikatoren in der marinen Ökologie, und in jüngerer Zeit auch in der Ökotoxikologie, regelmäßig verwendet werden, haben sie in der limnischen Ökologie bisher wenig Anwendung gefunden. Um die Anwendung physiologischer Indikatoren in diesem Bereich zu verstärken verfolgt die Dissertation zwei Ziele. Zum einen verdeutlicht sie das Potenzial der einzelnen physiologischen Indikatoren, zum anderen stellt sie Grundlagenwissen zu ausgewählten ökophysiologischen Aspekten einheimischer und gebietsfremder Arten der Ordnung Amphipoda bereit, die als Schlüsselarten aquatischer Lebensräume als besonders geeignet für die Bestimmung physiologischer Indikatoren angesehen werden. In diesem Sinne werden in Kapitel 2 sowohl die grundlegenden Annahmen, als auch die theoretischen und methodischen Grundlagen für die Bestimmung physiologischer Indikatoren aufgezeigt und ihre Anwendbarkeit in Fallstudien verdeutlicht. Die durchgeführten Experimentalstudien (Kapitel 3−5) liefern Informationen zu (i) den art- und geschlechtsspezifischen Unterschieden in der saisonalen Variation des energetischen Zustandes natürlicher Gammarus Populationen (G. fossarum, G. pulex), (ii) den Unterschieden in der Stoffwechsel- und Bewegungsaktivität verschiedener Amphipoda-Arten (G. fossarum, G. roeselii und D. villosus), sowie (iii) den direkten Auswirkungen von Ammoniak auf die Physiologie und die Bewegungsaktivität von D. villosus. In Kapitel 6 werden abschließend die grundlegenden Schlussfolgerungen aus den durchgeführten Feld- und Laborstudien, sowie ihre Relevanz und Auswirkungen für die Anwendung physiologischer Indikatoren in der limnischen Ökologie diskutiert.
Pelagic oxyclines, the transition zone between oxygen rich surface waters and oxygen depleted deep waters, are a common characteristic of eutrophic lakes during summer stratification. They can have tremendous effects on the biodiversity and the ecosystem functioning of lakes and, to add insult to injury, are expected to become more frequent and more pronounced as climate warming progresses. On these grounds, this thesis endeavors to advance the understanding of formation, persistence, and consequences of pelagic oxyclines: We test, whether the formation of metalimnetic oxygen minima is intrinsically tied to a locally enhanced oxygen consuming process, investigate the relative importance of vertical physical oxygen transport and biochemical oxygen consumption for the persistence of pelagic oxyclines, and finally assess their potential consequences for whole lake cycling. To pursue these objectives, the present thesis nearly exclusively resorts to in situ measurements. Field campaigns were conducted at three lakes in Germany featuring different types of oxyclines and resolved either a short (hours to days) or a long (weeks to months) time scale. Measurements comprised temperature, current velocity, and concentrations of oxygen and reduced substances in high temporal and vertical resolution. Additionally, vertical transport was estimated by applying the eddy correlation technique within the pelagic region for the first time. The thesis revealed, that the formation of metalimnetic oxygen minima does not necessarily depend on locally enhanced oxygen depletion, but can solely result from gradients and curvatures of oxygen concentration and depletion and their relative position to each other. Physical oxygen transport was found to be relevant for oxycline persistence when it considerably postponed anoxia on a long time scale. However, its influence on oxygen dynamics was minor on short time scales, although mixing and transport were highly variable. Biochemical consumption always dominated the fate of oxygen in pelagic oxyclines. It was primarily determined by the oxidative breakdown of organic matter originating from the epilimnion, whereas in meromictic lakes, the oxidation of reduced substances dominated. Beyond that, the results of the thesis emphasize that pelagic oxyclines can be a hotspot of mineralization and, hence, short-circuit carbon and nutrient cycling in the upper part of the water column. Overall, the present thesis highlights the importance of considering physical transport as well as biochemical cycling in future studies.