Fish populations are increasingly being subjected to anthropogenic changes to their sensory environments. The impact of these changes on inter- and intra-specific communication, and its evolutionary consequences, has only recently started to receive research attention. A disruption of the sensory environment is likely to impact communication, especially with respect to reproductive interactions that help to maintain species boundaries. Aquatic ecosystems around the world are being threatened by a variety of environmental stressors, causing dramatic losses of biodiversity and bringing urgency to the need to understand how fish respond to rapid environmental changes. Here, we discuss current research on different communication systems (visual, chemical, acoustic, electric) and explore the state of our knowledge of how complex systems respond to environmental stressors using fish as a model. By far the bulk of our understanding comes from research on visual communication in the context of mate selection and competition for mates, while work on other communication systems is accumulating. In particular, it is increasingly acknowledged that environmental effects on one mode of communication may trigger compensation through other modalities. The strength and direction of selection on communication traits may vary if such compensation occurs. However, we find a dearth of studies that have taken a multimodal approach to investigating the evolutionary impact of environmental change on communication in fish. Future research should focus on the interaction between different modes of communication, especially under changing environmental conditions. Further, we see an urgent need for a better understanding of the evolutionary consequences of changes in communication systems on fish diversity.

Arsenic contamination of shallow groundwater is among the biggest health threats in the developing world. Targeting uncontaminated deep aquifers is a popular mitigation option although its long-term impact remains unknown. Here we present the alarming results of a large-scale groundwater survey covering the entire Red River Delta and a unique probability model based on three-dimensional Quaternary geology. Our unprecedented dataset reveals that ∼7 million delta inhabitants use groundwater contaminated with toxic elements, including manganese, selenium, and barium. Depth-resolved probabilities and arsenic concentrations indicate drawdown of arsenic-enriched waters from Holocene aquifers to naturally uncontaminated Pleistocene aquifers as a result of > 100 years of groundwater abstraction. Vertical arsenic migration induced by large-scale pumping from deep aquifers has been discussed to occur elsewhere, but has never been shown to occur at the scale seen here. The present situation in the Red River Delta is a warning for other As-affected regions where groundwater is extensively pumped from uncontaminated aquifers underlying high arsenic aquifers or zones.

Lake Powell is a large reservoir in Utah and Arizona that has experienced large changes in water level during a recent drought. As a first step in assessing the connection between hydrologic and chemical changes at Lake Powell, we characterized the particle size and solid-phase bulk concentrations for 31 elements and 25 minerals in sediment from the inflow region and some shoreline locations by using laser diffractometry, X-ray fluorescence, elemental analysis, and X-ray diffraction. Our results are consistent with previous results that show a negative correlation between particle size and concentrations of most elements and most minerals other than quartz and some feldspars. In our samples, however, solid-phase iron, rather than particle size or organic carbon, is the best predictor variable for the solid-phase concentrations of elements and minerals. Sediment characteristics vary on a scale of tens of kilometers, with fine sediment that is enriched in trace elements nearer to the dam. These trends allow formulation of an algorithm for determining a water-level threshold below which sediment resuspension may alter water chemistry in a generic reservoir with a long and narrow sediment delta.

Groundwater resources in the Pannonian Basin (Hungary, Romania, Croatia and Serbia) are known to contain elevated naturally occurring As. Published estimates suggest nearly 500,000 people are exposed to levels greater than the EU maximum admissible concentration of 10μg/L in their drinking water, making it the largest area so affected in Europe. In this study, a variety of groundwaters were collected from Romania and Hungary to elucidate the general geochemistry and identify processes controlling As behaviour. Concentrations ranged from <0.5 to 240μg/L As(tot), with As predominantly in the reduced As(III) form. Using cluster analysis, four main groups of water were identified. Two groups (1 and 2) showed characteristics of water originating from reducing aquifers of the area with both groups having similar ranges of Fe concentrations, indicating that Fe-reduction occurs in both groups. However, As levels and other redox characteristics were very different. Group 1, indicative of waters dominated by methanogenesis contained high As levels (23-208μg/L, mean 123μg/L), with group 2 indicative of waters dominated by SO42--reduction containing low As levels (<0.5-58μg/L, mean 11.5μg/L). The remaining two groups were influenced either by (i) geothermal and saline or (ii) surface contamination and rain water inputs. Near absence of As in these groups, combined with positive correlations between δ<SUP>7</SUP>Li (an indicator of geothermal inputs) and As(tot) in geothermal/saline influenced waters indicate that elevated As is not from an external input, but is released due to an in-aquifer process. Geochemical reasoning, therefore, implies As mobilisation is controlled by redox processes, most likely microbially mediated reductive dissolution of As bearing Fe-oxides, known to occur in sediments from the area. More important is an overlying retention mechanism determined by the presence or absence of SO<SUB>4</SUB><SUP>2-</SUP>. Ongoing SO<SUB>4</SUB><SUP>2-</SUP>-reduction will release S<SUP>2-</SUP>, removing As from solution either by the formation of As-sulfides, or from sorption onto Fe-sulfide phases. In methanogenic waters, As released by reductive dissolution is not removed from solution and can rise to the high levels observed. Levels of organic C are thought to be the ultimate control on the redox conditions in these 2 groups. High levels of organic C (as found in group 1) would quickly exhaust any SO<SUB>4</SUB><SUP>2-</SUP> present in the waters, driving the system to methanogenesis and subsequent high levels of As. Group 2 has much lower concentrations of organic C and so SO<SUB>4</SUB><SUP>2-</SUP> is not exhausted. Therefore, As levels in waters of the Pannonian Basin are controlled not by release but by retention mechanisms, ultimately controlled by levels of TOC and SO<SUB>4</SUB><SUP>2-</SUP> in the waters.δD and δ<SUP>18</SUP>O analysis showed that groundwaters containing elevated As dated mostly from the last ice-age, and are sourced from Late Pliocene to Quaternary aquifers. The importance of TOC and retention capabilities of SO<SUB>4</SUB><SUP>2-</SUP>-reduction have only previously been suggested for recent (Holocene) sediments and groundwater, most notably those in SE Asia as these are the most likely to contain the right combination of factors to drive the system to a redox situation leading to high aqueous As concentrations. In contrast, it is shown here that a much older system containing As bearing Fe-oxides, also has the potential to produce elevated levels of As if the TOC is suitable for the microbial population to drive the system to the correct redox situation and SO<SUB>4</SUB><SUP>2-</SUP> is either absent or wholly consumed.

In situ rates of reductive dissolution in submerged shoreline sediments at Lake Tegel (Berlin, Germany) were measured with a novel hydrous manganese (Mn) oxide-doped gel probe sampler in concert with equilibrium gel probe and sequential extraction measurements. Rates were low in the top 8 cm, then showed a peak from 8 to 14 cm, with a maximum at 12 cm depth. This rate corresponded with a peak in dissolved porewater iron (Fe) at 11 cm depth. Below 14 cm, the reductive dissolution rate reached an intermediate steady value. Lower rates at depth corresponded with increases in operationally defined fractions of carbonate-bound and organic- and sulfide-bound Mn and Fe as detected by sequential extraction. Observed rates of reductive dissolution, which reflect a capacity for Mn reduction rather than actual rates under ambient conditions, appear to correlate with porewater chemistry and sequential extraction fractions as expected in early sediment diagenesis, and are consistent with previous measurements of in situ reductive dissolution rates. Significant downward advection in this bank filtration setting depletes the Mn and Fe oxides in the sediments and enhances the transport of dissolved Fe and Mn into the infiltrating water.

Reductive dissolution of redox-sensitive minerals such as manganese (Mn) oxides in natural sediments is an important mechanism for trace element mobilization into groundwater. A gel probe sampler has been constructed to study in situ reductive dissolution of Mn oxides. The gel consists of a polyacrylamide polymer matrix doped with hydrous Mn oxide (HMO). Gel slabs are mounted into a probe, which is designed to be inserted into the sediments. The amount of Mn released from the gel by reductive dissolution is determined by comparing the amount of Mn initially embedded into the gel with the amount remaining in the gel after exposure to conditions in the sediments or, in laboratory studies, to reducing agents. In this laboratory study, the performance of the gel probes was examined using the model reductant ascorbate and the Mn-reducing bacteria <I>Shewanella oneidensis</I> strain MR-1. In addition, a 1-D model was used to relate the reaction rates observed for HMO embedded in gels to those for HMO in suspension. One limitation of the HMO-doped gels for assessing microbial reduction rates is that the gels prevent direct contact between the microbes and the HMO and hence preclude enzymatic reduction at the cell surface. Nonetheless, the HMO-doped gel probes offer the possibility to establish a lower bound for Mn-reduction capacity in sediments.

Despite the importance of the nitrogen (N) cycle on marine productivity, little is known about variability in N sources and cycling in the ocean in relation to natural and anthropogenic climate change. Beyond the last few decades of scientific observation, knowledge depends largely on proxy records derived from nitrogen stable isotopes (<I>δ</I><SUP>15</SUP>N) preserved in sediments and other bioarchives. Traditional bulk <I>δ</I><SUP>15</SUP>N measurements, however, represent the combined influence of N source and subsequent trophic transfers, often confounding environmental interpretation. Recently, compound-specific analysis of individual amino acids (<I>δ</I><SUP>15</SUP>N-AA) has been shown as a means to deconvolve trophic level versus N source effects on the <I>δ</I><SUP>15</SUP>N variability of bulk organic matter. Here, we demonstrate the first use of <I>δ</I><SUP>15</SUP>N-AA in a paleoceanographic study, through analysis of annually secreted growth rings preserved in the organic endoskeletons of deep-sea gorgonian corals. In the Northwest Atlantic off Nova Scotia, coral <I>δ</I><SUP>15</SUP>N is correlated with increasing presence of subtropical versus subpolar slope waters over the twentieth century. By using the new <I>δ</I><SUP>15</SUP>N-AA approach to control for variable trophic processing, we are able to interpret coral bulk <I>δ</I><SUP>15</SUP>N values as a proxy for nitrate source and, hence, slope water source partitioning. We conclude that the persistence of the warm, nutrient-rich regime since the early 1970s is largely unique in the context of the last approximately 1,800 yr. This evidence suggests that nutrient variability in this region is coordinated with recent changes in global climate and underscores the broad potential of <I>δ</I><SUP>15</SUP>N-AA for paleoceanographic studies of the marine N cycle.

The spectacular diversity in sexually selected traits among animal taxa has inspired the hypothesis that divergent sexual selection can drive speciation. Unfortunately, speciation biologists often consider sexual selection in isolation from natural selection, even though sexually selected traits evolve in an ecological context: both preferences and traits are often subject to natural selection. Conversely, while behavioural ecologists may address ecological effects on sexual communication, they rarely measure the consequences for population divergence. Herein, we review the empirical literature addressing the mechanisms by which natural selection and sexual selection can interact during speciation. We find that convincing evidence for any of these scenarios is thin. However, the available data strongly support various diversifying effects that emerge from interactions between sexual selection and environmental heterogeneity. We suggest that evaluating the evolutionary consequences of these effects requires a better integration of behavioural, ecological and evolutionary research.

With the worldwide intensification of agriculture, non-point source pollution of surface waters has become a pressing issue. Conventional river water quality models consider non-point sources as accumulated entries into the rivers and do not investigate into the processes generating the pollution at its source, thus preventing the determination of effective mitigation measures. The models require extensive data inputs, which is a deficiency in many developing and emerging countries with limited data availability. The current study applies a Material Flow Model as a complementary approach to quantify non-point source pollution from agricultural areas. Rice farming in the Thachin River Basin is presented as a case study, with a focus on nutrients. The total nitrogen and phosphorus flows from rice farming to the river system are quantified, the key parameters influencing these flows are determined and potential mitigation measures are discussed. The results show that rice contributes considerable nutrient loads to the Thachin River Basin. Scenario simulations demonstrate that a significant nutrient load reduction could be achieved by following the official recommendations for fertilizer application, thus confirming the local efforts to introduce best management practice. Our results underline the importance of non-point source pollution control in intensive agricultural areas, particularly of tropical lowland delta areas such as the Central Plains of Thailand. The specific benefit of applying a Material Flow Model in this context is that with limited data availability, one can reach an understanding of the system and gain a first overview over its key pollution problems. This can serve as supportive basis for determining consecutive in-depth research requirements.

A simple method to automatically measure the date of ice-on, the date of ice-off, and the duration of lake ice cover is described. The presence of ice cover is detected by recording water temperature just below the ice/water interface and just above the lake bottom using moored temperature sensors. The occurrence of ice-on rapidly leads to detectible levels of inverse stratification, defined as existing when the upper sensor records a temperature at least 0.1°C below that of the bottom sensor, whereas the occurrence of ice-off leads to the return of isothermal mixing. Based on data from 10 lakes over a total of 43 winter seasons, we found that the timing and duration of inverse stratification monitored by recording temperature sensors compares well with ice cover statistics based on human observation. The root mean square difference between the observer-based and temperature-based estimates was 7.1 d for ice-on, 6.4 d for ice-off, and 10.0 d for the duration of ice cover. The coefficient of determination between the two types of estimates was 0.93, 0.86, and 0.91, respectively. The availability of inexpensive self-contained temperature loggers should allow expanded monitoring of ice cover in a large and diverse array of lakes. Such monitoring is needed to improve our ability to monitor the progression of global climate change, and to improve our understanding of the relationship between climate and ice cover over a wide range of temporal and spatial scales

A natural carbon dioxide (CO<SUB>2</SUB>) seep was discovered during an expedition to the southern German North Sea (October 2008). Elevated CO<SUB>2</SUB> levels of ∼10–20 times above background were detected in seawater above a natural salt dome ∼30 km north of the East-Frisian Island Juist. A single elevated value 53 times higher than background was measured, indicating a possible CO<SUB>2</SUB> point source from the seafloor. Measured pH values of around 6.8 support modeled pH values for the observed high CO<SUB>2</SUB> concentration. These results are presented in the context of CO<SUB>2</SUB> seepage detection, in light of proposed subsurface CO<SUB>2</SUB> sequestering and growing concern of ocean acidification. We explore the boundary conditions of CO<SUB>2</SUB> bubble and plume seepage and potential flux paths to the atmosphere. Shallow bubble release experiments conducted in a lake combined with discrete-bubble modeling suggest that shallow CO<SUB>2</SUB> outgassing will be difficult to detect as bubbles dissolve very rapidly (within meters). Bubble-plume modeling further shows that a CO<SUB>2</SUB> plume will lose buoyancy quickly because of rapid bubble dissolution while the newly CO<SUB>2</SUB>-enriched water tends to sink toward the seabed. Results suggest that released CO<SUB>2</SUB> will tend to stay near the bottom in shallow systems (<200 m) and will vent to the atmosphere only during deep water convection (water column turnover). While isotope signatures point to a biogenic source, the exact origin is inconclusive because of dilution. This site could serve as a natural laboratory to further study the effects of carbon sequestration below the seafloor.

Based on a unique dataset of more than 50 000 observations of ice phenology from 1213 lakes and 236 rivers in 12 different countries, we show that interannual variations in the timing of ice-on and ice-off on lakes and rivers are not equally pronounced over the entire Northern Hemisphere, but increase strongly towards geographical regions that experience only short periods during which the air temperature falls below 0 °C. We explain our observations by interannual fluctuation patterns of air temperature and suggest that lake and river ecosystems in such geographical regions are particularly vulnerable to global warming, as high interannual variability is known to have important ramifications for ecosystem structure and functioning. We estimate that the standard deviation of the duration of ice cover, viewed as a measure of interannual variability, exceeds 25 days for lakes and rivers located on 7% of the land area of the Northern Hemisphere. Such high variability might be an early warning signal for a critical transition from strictly dimictic, ice-covered systems to monomictic, open-water systems. Using the Global Lake and Wetland Database, we suggest that 3.7% of the world's lakes larger than 0.1 km<SUP>2</SUP> are at high risk of becoming open-water systems in the near future, which will have immediate consequences for global biogeochemical cycles.

Drinking water was treated with ozone, chlorine, chlorine dioxide, monochloramine, ferrate(VI), and permanganate to investigate the kinetics of membrane damage of native drinking water bacterial cells. Membrane damage was measured by flow cytometry using a combination of SYBR Green I and propidium iodide (SGI+PI) staining as indicator for cells with permeabilized membranes and SGI alone to measure total cell concentration. SGI+PI staining revealed that the cells were permeabilized upon relatively low oxidant exposures of all tested oxidants without a detectable lag phase. However, only ozonation resulted in a decrease of the total cell concentrations for the investigated reaction times. Rate constants for the membrane damage reaction varied over seven orders of magnitude in the following order: ozone > chlorine > chlorine dioxide ≈ ferrate > permanganate > chloramine. The rate constants were compared to literature data and were in general smaller than previously measured rate constants. This confirmed that membrane integrity is a conservative and therefore safe parameter for disinfection control. Interestingly, the cell membranes of high nucleic acid (HNA) content bacteria were damaged much faster than those of low nucleic acid (LNA) content bacteria during treatment with chlorine dioxide and permanganate. However, only small differences were observed during treatment with chlorine and chloramine, and no difference was observed for ferrate treatment. Based on the different reactivity of these oxidants it was suggested that HNA and LNA bacterial cell membranes have a different chemical constitution.

Vor zehn Jahren wurde die Internationale Ultraviolet Association (IUVA; www.iuva.org) gegründet. Sie hat sich zum Ziel gesetzt, ein Diskussionsforum anzubieten für alle wissenschaftlichen und technischen Fragen, die die Verwendung von UV-Licht betreffen, wobei die Desinfektion von Trink- und Abwasser sowie von Luft mittels UV-Strahlung im Vordergrund steht. Hierzu veröffentlicht die IUVA die IUVANews und organisiert Konferenzen und Workshops zu verschiedenen Themen betreffend UV-Technologien. Schliesslich engagiert sich die IUVA auch für die Einführung vernünftiger nationaler Richtlinien und Regeln, die die Anwendung von UV-Techniken fördern.

Saxitoxins (STXs) are carbamate alkaloid neurotoxins produced by marine "red tide" dinoflagellates and several species of freshwater filamentous cyanobacteria, including <em>Anabaena circinalis</em>, <em>Aphanizomenon</em> spp., <em>Lyngbya wollei</em>, and <em>Cylindrospermopsis raciborskii</em>. A specific quantitative PCR (qPCR) method based on SYBR green chemistry was developed to quantify saxitoxin-producing <em>Anabaena circinalis</em> cyanobacteria, which are major bloom-forming freshwater cyanobacteria. The aim of this study was to infer the potential toxigenicity of samples by determining the copy number of a unique and unusual polyketide synthase (PKS) sequence (<em>sxtA</em>) in the STX biosynthesis gene cluster identified in cyanobacteria. Our qPCR approach was applied to water samples collected from different Australian lakes, dams, and rivers. The STX concentration and cyanobacterial cell density of these blooms were also determined by high-pressure liquid chromatography (HPLC) and microscopic cell counting, respectively. STX concentrations correlated positively with STX gene copy numbers, indicating that the latter can be used as a measure of potential toxigenicity in <em>Anabaena circinalis</em> and possibly other cyanobacterial blooms. The qPCR method targeting STX genes can also be employed for both monitoring and ecophysiological studies of toxic <em>Anabaena circinalis</em> blooms and potentially several other STX-producing cyanobacteria.

Broad scale monitoring of estrogenic compounds was performed at 19 sampling points throughout the Yeongsan and Seomjin river basins and 5 wastewater treatment plants (WWTPs) adjacent to the Gwangju area, Korea, from December 2005 to August 2007. The concentrations of estrogenic compounds, including estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), bisphenol-A, nonylphenol (NP) and 4-octylphenol (OP), in the samples was measured with gas chromatography/mass spectrometry (GC-MS). In addition, the estrogenic activities throughout the river were investigated using the <I>E</I>-screen assay. Of the six estrogenic chemicals, NP (114.6–336.1 ng L<SUP>−1</SUP>) and EE2 (0.23–1.90 ng L<SUP>−1</SUP>) were detected at the highest and lowest levels, respectively in both the river waters and the WWTP effluents. Bisphenol-A showed the largest concentration range, from 7.5 to 335 ng L<SUP>−1</SUP>. The concentrations of E1, E2 and octylphenol ranges were 3.6–69.1, 1.2–10.7, and 2.2–16.9 ng L<SUP>−1</SUP>, respectively. According to the calculated estradiol equivalent concentration (EEQ); however, no estrogenic contribution was observed due to the phenolic compounds in the river waters and effluents. E1 and E2 dominated in both the river water and effluent samples, with contributions to the calculated EEQ of over 79 and 77%, respectively. Conversely, EE2 was rarely detected in the river waters (21%) and effluents (0%). The largest contribution of EE2 to the calculated EEQ was 21% in the river water at S-7. The levels of E1, E2, and EE2 were remarkably decreased in the effluents, indicating that the 5 WWTPs did not contribute to the estrogenic effect of the receiving streams. Overall, the WWTPs did not contributed to the estrogenic activity of the receiving waters, but the livestock industry or wildlife may play an important role in the estrogenic contribution to river water.

Both host susceptibility and parasite infectivity commonly have a genetic basis, and can therefore be shaped by coevolution. However, these traits are often sensitive to environmental variation, resulting in genotype-by-environment interactions. We tested the influence of temperature on host–parasite genetic specificity in the <I>Daphnia longispina</I> hybrid complex, exposed to the protozoan parasite <I>Caullerya mesnili</I>. Infection rates were higher at low temperature. Furthermore, significant differences between host clones, but not between host taxa, and a host genotype-by-temperature interaction were observed.

Parasite life cycle variation can shape parasite evolution, by predisposing them towards different population genetic structures. We compared the population genetic structure of two co-occurring parasite species of <I>Daphnia</I>, to collect evidence for their expected transmission modes. The ichthyosporean <I>Caullerya mesnili</I> has a direct life cycle, whereas the microsporidian <I>Berwaldia schaefernai</I> is hypothesized to require passage through a secondary host. The parasites were collected from three geographically isolated <I>Daphnia</I> populations. The nucleotide variation in the internal transcribed spacer (ITS) region was assessed at the within-individual, within-population and among-population levels, using AMOVA. We detected significant partitioning at all levels, except for a lack of among-population variation in <I>Berwaldia</I>. This was confirmed by neighbour-joining and principal component analyses; <I>Caullerya</I> populations were distinct from each other, while there was much overlap among parasite isolates representing different populations of <I>Berwaldia</I>. This all implies a higher amount of gene flow for <I>Berwaldia</I>, consistent with the hypothesized transmission mode.

Changes in the hydrological regime of the saline closed basin Lake Van, a large, deep lake in eastern Turkey, resulted in a lake level increase by about 2 m between 1988 and 1995, followed by a 1.5 m decrease until 2003 and a relatively constant lake level thereafter. Based on measurements of transient tracers (sulfur hexafluoride, CFC-12, <SUP>3</SUP>H, <SUP>3</SUP>He, <SUP>4</SUP>He, Ne), dissolved oxygen, light transmission, conductivity-temperature-depth profiles, and thermistor data, we investigate the implications associated with lake level fluctuations for deep-water renewal and oxygenation. Our data suggest that deep-water renewal was significantly reduced in Lake Van between 1990 and 2005. This change in mixing conditions resulted in the formation of a more than 100 m thick anoxic deep-water body below 325 m depth. Apparently, the freshwater inflows responsible for the lake level rise between 1988 and 1995 decreased the salinity of the surface water sufficiently that the generation of density plumes during winter cooling was substantially reduced compared to that in the years before the lake level rise. Significant renewal and oxygenation of the deep water did not occur until at least 2005, although by 2003 the lake level was back to almost the same level as in 1988. This study suggests that short-term changes in the hydrological regime, resulting in lake level changes of a couple of meters, can lead to significant and long-lasting changes in deep-water renewal and oxic conditions in deep saline lakes.

Many problems related to groundwater supply and quality, as well as groundwater-dependent ecosystems require some understanding of the timescales of flow and transport. For example, increased concern about the vulnerabilities of 'young' groundwaters (less than ∼ 1000 years) to overexploitation, contamination, and land use/climate change effects are driving the need to understand flow and transport processes that occur over decadal, annual, or shorter timescales. Over the last few decades, a powerful suite of environmental tracers has emerged that can be used to interrogate a wide variety of young groundwater systems and provide information about groundwater ages/residence times appropriate to the timescales over which these systems respond. These tracer methods have distinct advantages over traditional approaches providing information about groundwater systems that would likely not be obtainable otherwise. The objective of this paper is to discuss how environmental tracers are used to characterise young groundwater systems so that more researchers, water managers, and policy-makers are aware of the value of environmental tracer approaches and can apply them in appropriate ways. We also discuss areas where additional research is required to improve ease of use and extend quantitative interpretations of tracer results.

1. Plant–soil feedbacks can influence the success of non-native plant invasions. We investigated if these feedbacks and the underlying invasion effects on soil microbes and nutrients depend on the species composition of the invaded vegetation, and whether these effects are related to differences in the invasibility of native plant communities.<BR/>2. We carried out a mesocosm experiment simulating the invasion of <I>Solidago gigantea</I> into three wetland plant communities (<I>Molinion</I>, <I>Magnocaricion</I> and <I>Filipendulion</I>), each composed of five plant species but differing in productivity. To study plant–soil feedbacks, we used different soil inoculum types from invaded and non-invaded field sites of the corresponding communities and a reference site. Invasion success was assessed by measuring the biomass of <I>S. gigantea</I> after three growing seasons and by analysing soil properties several times during the experiment.<BR/>3. Invasion success varied significantly among communities and soil inoculum types. <I>Solidago gigantea</I> produced more biomass in the <I>Molinion</I> than in the two more productive communities. In all three communities, it exhibited a negative feedback upon itself, producing 31–46% less biomass when the substrate was inoculated with soil from a stand invaded with <I>S. gigantea</I>.<BR/>4. The presence of <I>S. gigantea</I> did not influence total biomass in any community nor N and P availability in soil. However, it led to a decrease in soil bacterial and an increase in soil fungal biomasses. These changes were similar in the three communities and unrelated to the biomass of <I>S. gigantea</I> biomass in the invaded communities.<BR/>5. <I>Synthesis</I>. The experimental comparison between effects of an invasive plant species on soil properties in different native communities showed similar effects despite pronounced differences in the ability of the invasive species to grow in the different communities. In this system, plant–soil interactions may thus affect invasion, but not explain differences in the invasibility of different communities. The invasive species increased soil fungal biomass, particularly in its own soil, compared to native species and experienced a negative feedback, suggesting that the course of its invasion might be affected by species-specific soil pathogens.

During wastewater treatment, many organic micropollutants undergo microbially mediated reactions resulting in the formation of transformation products (TPs). Little is known on the reaction pathways that govern these transformations or on the occurrence of microbial TPs in surface waters. Large sets of biotransformation data for organic micropollutants would be useful for assessing the exposure potential of these TPs and for enabling the development of structure-based biotransformation prediction tools. The objective of this work was to develop an efficient procedure to allow for high-throughput elucidation of TP structures for a broad and diverse set of xenobiotics undergoing microbially mediated transformation reactions. Six pharmaceuticals and six pesticides were spiked individually into batch reactors seeded with activated sludge. Samples from the reactors were separated with HPLC and analyzed by linear ion trap-orbitrap mass spectrometry. Candidate TPs were preliminarily identified with an innovative post-acquisition data processing method based on target and non-target screenings of the full-scan MS data. Structures were proposed following interpretation of MS spectra and MS/MS fragments. Previously unreported microbial TPs were identified for the pharmaceuticals bezafibrate, diazepam, levetiracetam, oseltamivir, and valsartan. A variety of previously reported and unreported TPs were identified for the pesticides. The results showed that the complementary use of the target and non-target screening methods allowed for a more comprehensive interpretation of the TPs generated than either would have provided individually.

Aims: The objective was to analyse the impact of growth conditions, in particular of the specific growth rate, on the resistance of <I>Escherichia coli</I> towards UV-C irradiation.<BR/>Methods and Results: <I>Escherichia coli</I> K12 wild-type bacteria (and in some experiments also a mutant not expressing RpoS, the global regulator of the general stress response; <I>rpoS<SUP>−</SUP></I> mutant) were cultivated either in batch culture until stationary phase was reached or in continuous culture at different specific growth rates (μ) and then irradiated with UV-C light. Inactivation was determined by plating. The specific growth rate had a profound effect on UV-C resistance. Stationary phase or very slowly growing cells (0 ≤ μ < 0·1 h<SUP>−1</SUP>) as well as fast-growing cells exhibited a high resistance compared to bacteria growing at an intermediate rate (between 0·2 and 0·4 h<SUP>−1</SUP>). The <I>rpoS<SUP>−</SUP></I> mutant was more susceptible to UV irradiation than the wild-type when obtained from stationary phase, while mutant cells from continuous culture (μ = 0·2 h<SUP>−1</SUP>) revealed a UV-C resistance similar to the wild-type grown under the same conditions.<BR/>Conclusions: Antecedent growth conditions determine the physiological state of bacteria including the resistance towards UV-C irradiation. In particular, the specific growth rate was shown to markedly affect UV-C resistance of <I>E. coli</I>. The observed pattern of UV-C resistance exhibiting a minimum at intermediate specific growth rates must be explained by two or several counteracting mechanisms. For lower specific growth rates, the regulator of the global stress response, RpoS, is at least partly involved in the physiological processes responsible for UV-C resistance.<BR/>Significance and Impact of the Study: The observed impact of antecedent growth conditions on UV-C resistance of <I>E. coli</I> stresses the necessity to use clearly defined cultivation conditions and to report them to gather meaningful and comparable data on the UV-C resistance of micro-organisms.

The use of groundwater as drinking water resource requires knowledge of its microbiological quality. Samples collected at sites of the National Groundwater Monitoring NAQUA revealed the presence of bacteria, viruses and protozoa, none of which, however, were proved to be infectious. The occurrence of these microorganisms could be linked to the aquifer type. Least affected were unconsolidated porous aquifers while karst aquifers were most affected. These findings represent a snapshot of the microbiological status at the monitoring sites and provide an overview of the type and occurrence of microorganisms in Swiss groundwater.

Solar disinfection (SODIS) is a simple drinking water treatment method that improves microbiological water quality where other means are unavailable. It makes use of the deleterious effect of solar irradiation on pathogenic microbes and viruses. A positive impact on health has been documented in several epidemiological studies. However, the molecular mechanisms damaging cells during this simple treatment are not yet fully understood. Here we show that protein damage is crucial in the process of inactivation by sunlight. Protein damages in UVA-irradiated <I>Escherichia coli</I> cells have been evaluated by an immunoblot method for carbonylated proteins and an aggregation assay based on semi-quantitative proteomics. A wide spectrum of structural and enzymatic proteins within the cell is affected by carbonylation and aggregation. Vital cellular functions like the transcription and translation apparatus, transport systems, amino acid synthesis and degradation, respiration, ATP synthesis, glycolysis, the TCA cycle, chaperone functions and catalase are targeted by UVA irradiation. The protein damage pattern caused by SODIS strongly resembles the pattern caused by reactive oxygen stress. Hence, sunlight probably accelerates cellular senescence and leads to the inactivation and finally death of UVA-irradiated cells.

Global change results in fast and severe alterations of environmental parameters. New environmental conditions that call for adaptations are created. For the Baltic Sea, a decrease in salinity is predicted and in particular shallow ocean habitats are highly influenced by the expected higher precipitation rates and temperatures due to the low water depth. Especially interactions between two species, such as host-parasite interactions, can be disrupted by environmental changes if the interacting species respond differently to the environmental changes. A resulting imbalance can possibly be deleterious for one of the species. Here, we investigated how the host-parasite interaction of pipefish (<em>Syngnathus typhle</em>), a small coastal marine fish, and bacteria of the genus <em>Vibrio </em>is influenced by changing salinities. Three salinity levels were used - highly brackish water (6 PSU), their habitual salinity (18 PSU), and an oceanic salinity (30 PSU). After acclimatisation to the new environment, the fish were injected with <em>Vibrio</em>. Pipefish up-regulated their immune defence upon salinity change, in particular if salinity was decreased. These environmentally stressed fish later lacked resources for an immune activation to fight the bacterial infection. This might decrease the survival rate and ultimately affect population size and distribution of <em>Syngnathus typhle</em>.<br /><br /> Globaler Wandel hat schnelle und schwerwiegende Veränderungen von Umweltparametern zur Folge. Neue Umweltbedingungen werden geschaffen, die Adaptationen verlangen. Für die Ostsee wird eine Senkung des Salzgehaltes im Wasser vorhergesagt und vor allem untiefe Meeresstandorte werden stark von der erwarteten hohen Niederschlagsmenge und von hohen Temperaturen beeinflusst. Insbesondere Wechselwirkungen zwischen zwei Spezies, wie z.B. Wirt-Parasit-Beziehungen, können durch Umweltveränderungen gestört werden, wenn die Spezies verschieden auf die Veränderungen reagieren. Das resultierende Ungleichgewicht in der Wechselwirkung kann für eine der Arten schädliche Folgen haben. In diesem Projekt haben wir untersucht wie die Wirt-Parasit Beziehung zwischen der Grasnadel (<em>Syngnathus typhle</em>), einem kleinen Küstenfisch, und Bakterien von der Gattung <em>Vibrio </em>durch verändernde Salinitäten beeinflusst wird. Drei Salinitäten wurden für die Experimente benutzt - leicht salziges Wasser (6 PSU), die gewohnte Salinität der Fische (18 PSU), und ozeanische Salinität (30 PSU). Nach einer Angewöhnung an die neue Umgebung wurde den Fischen <em>Vibrio </em>Bakterien injiziert. Die Grasnadeln haben ihr Immunsystem als Antwort auf die Salinitätsveränderungen aktiviert, vor allem wenn der Salzgehalt des Wassers gesenkt wurde. Die durch die veränderten Umweltbedingungen beanspruchten Tiere hatten nicht mehr genug Ressourcen, um das Immunsystem nach einer bakteriellen Infektion zu aktivieren. Die Überlebensrate der Fische könnte dadurch beeinflusst werden, was schlussendlich die Populationsgrösse und Verbreitung von <em>Syngnathus typhle</em> beeinträchtigt.

Heute werden in der Schweiz rund 60 % des erzeugten Stroms aus Wasserkraft produziert (BFE, 2011). Wasserkraftwerke verbrauchen keine natürlichen Ressourcen und sind C0₂-neutral, jedoch verändern sie den natürlichen Abfluss von Fliessgewässern und behindern die Fische bei der Wanderung. Mit dem geplanten Atomausstieg und der dadurch steigenden Nachfrage nach erneuerbaren Energien, wächst der Druck auf Schweizer Fliessgewässer und deren Lebewesen weiter. Zudem unterbrechen mehr als 100‘000 Querbauwerke (&gt;50 cm) die longitudinale Konnektivität der Gewässer, so dass viele Fische nicht oder nur erschwert wandern können (Zeh Weissmann et al., 2009). Um die Wanderung der Fische wieder zu gewährleisten und der stetigen Zunahme an gefährdeten Fischarten entgegenzuwirken, wurden vielerorts Fischaufstiegshilfen installiert. Dadurch konnte das Problem der Aufwanderung ansatzweise verbessert werden. Ob die Fische jedoch stromabwärts Hindernisse passieren können, war weitgehend nicht zur Diskussion gestellt. Seit Inkrafttreten der neuen Gewässerschutzgesetzgebung 2011 müssen die Kantone Massnahmen ergreifen, welche die freie Fischwanderung bei Wasserkraftwerken in beiden Richtungen gewährleisten: Dazu gehören sowohl Fischaufstiegshilfen als auch Fischabstiegshilfen (Hefti, 2012). [...]

Riverine floodplains are among the most biologically diverse and productive ecosystems worldwide. They consist of a mosaic of different habitat types ranging from terrestrial floodplain forests to aquatic channels. They can serve as model ecosystems to investigate the linkage between environmental heterogeneity and ecosystem functioning. In this study, the alpine floodplain of the Urbach in the Bernese Alps in Switzerland was investigated. It is characterized by high volume of hyporheic flow which leads to a downand upwelling dynamic within the whole system. Upwelling groundwater is frequently enriched by nutrients relative to the surface water, which can influence ecosystem processes in these areas.<br /> We measured soil and sediment respiration, bacterial abundance and enzyme activities throughout an annual cycle in four terrestrial (gravel, island, alluvial forest and meadow) and one aquatic (channel) habitats in the floodplain of the Urbach. Additionally, the down- and upwelling dynamic of the system was monitored.<br /> The investigated habitat types differed greatly in their substratum composition, water content and temperature. The results display a highly heterogeneous system with low values of respiration, bacterial abundance and enzyme activities in the channel and gravel habitats and distinctly higher values in the alluvial forest, island and meadow habitats. Temperature and bacterial abundance were the most important predictors of soil and sediment respiration.<br /> The down- and upwelling dynamic could be demonstrated and respiration, bacterial abundance and enzyme activities revealed in several habitats higher values in the upwelling zone. This indicates the importance of upwelling water towards enhancement of ecosystem processes.<br /> These results underline the highly heterogeneous character of riverine floodplains and contribute to a more detailed and holistic understanding of the relationship between environmental heterogeneity and ecosystem processes.

Lakes play a significant role as a sink in the global carbon cycle, as their sediments can store carbon even more efficiently than marine systems. The fate of amino sugars and amino acids is particularly interesting because they are involved in the carbon and nitrogen cycle. Amino sugars and amino acids account for large fractions of primarily produced organic matter (OM) and can be used to determine OM freshness and diagenetic state. By the same token, the contribution of bacteria to the OM pool can be studied with amino biomarkers. [...]<br /><br />Da Seesedimente organischen Kohlenstoff effizienter speichern als marine Systeme, spielen sie eine signifikante Rolle als Kohlenstoffsenke im globalen Kohlenstoffkreislauf. Insbesondere der Verbleib von Aminozuckern und Aminosäuren ist dabei von speziellem Interesse, da sie sowohl im Kohlen- als auch im Stickstoffkreislauf involviert sind. Ein grosser Teil des während der Photosynthese aufgebauten organischen Materials (OM) besteht aus Aminozuckern und Aminosäuren, die zur Bestimmung des diagenetischen Status des OMs genutzt werden können. Weitherhin kann der Beitrag von Bakterien zum OM ebenfalls mit Amino-Biomarkern abgeschätzt werden. [...]

Almost 800 million people worldwide lack access to improved drinking water sources. As a consequence, water-borne diseases, including chronic illness and increased mortality from geogenic contaminants in groundwater pose severe threats to human health and well-being worldwide. The situation in developing countries is particularly dire, as central water supply is rare, and mitigation therefore more complex. In rural Bangladesh, millions of people are at risk of drinking water with elevated arsenic, despite the fact that many have gained awareness of the health risks, and over 100’000 safe water options have been installed in recent years. It is being increasingly recognized that without people’s compliance, health risks, including water-related risks cannot be mitigated. The social cognition approach proposes that behavior is best explained by an individual’s perceptions of objective reality. Moreover, these determinants are assumed to be modifiable, wherefore interventions targeting the behavioral determinants should increase behavior change effects of standard interventions that are developed without theoretical considerations. This thesis aims at applying this approach to promote safe water consumption. [...]

One strategy to feed the human population in a sustainable manner is to increase the agricultural productivity through improved management of locally available resources. To address the challenges of high rainfall variability and low soil fertility in Sub-Saharan Africa, low-cost soil moisture and soil fertility enhancing technologies, such as water harvesting (WH) and ecological sanitation (Ecosan), are particularly favoured. In this dissertation, crop growth constraints in smallholder rain-fed agriculture are analysed on river basin and regional scales in Southern Africa. The dissertation proceeds with a quantification of the potential impacts of WH, Ecosan, and other irrigation and fertilization technologies on maize yield (the local staple food crop), evaporation, transpiration, and river flow regimes. Building on this, it indentifies locations and conditions where such technologies could be suitable, and analyses their potential to improve agricultural productivity and food security.<br /> A scenario analysis is used together with the SWAT agro-hydrological computer model (Soil and Water Assessment Tool). The Sequential Uncertainty Fitting algorithm is applied to calibrate the model against river discharge and maize yield, and to quantify prediction uncertainty. The dissertation consists of four studies detailing baseline conditions, model performance, data processing methods, and potential impacts of WH and Ecosan technologies in the Thukela River basin (29,000 km2) and throughout Southern Africa (1.8x10⁶ km²).<br /> The first study quantifies the model performance and estimates the water availability for in situ WH, supplemental water demand (SWD) in smallholder agriculture, and the reliability of in situ WH in the Thukela River basin. On average, 0–17 mm of runoff water is available for in situ WH each year (95% prediction uncertainty range (95PPU)). This may meet some but not all of the SWD (median: 0–113 mm a⁻¹, 95PPU). The reliability of in situ WH (the percentage of years in which the water availability ≥ SWD) is highly location specific and overall rather low. Of the 1850 km² of smallholder lands, 20–28% display a reliability ≥ 25%, 13–16% a reliability ≥ 50%, and 4–5% a reliability ≥ 75% (95PPU). Hence, the risk of failure of in situ WH is relatively high in many areas. These results build on a satisfactorily performing model. The Root Mean Squared Error for smallholder maize yield was 0.02 t ha⁻¹ during both the calibration and evaluation periods. The range in the coefficient of determination (R²) for discharge during the calibration (evaluation) period was 0.42–0.83 (0.28–0.72).<br /> The second study explores the potential impacts of application of in situ WH and fertilization with stored human urine (Ecosan) in the Thukela River basin. Based on the model results, the impacts on smallholder maize yields are likely to be small with in situ WH (median change: 0%) but significant with Ecosan (median increase: 30%). The primary causes for these effects were high nitrogen stress on crop growth, and low or untimed soil moisture enhancement with in situ WH. However, the impacts varied significantly in time and space, occasionally resulting in yield increases of up to 40% with in situ WH. Full fertilization increased yields by a factor of five, whereas full irrigation reduced spatial yield variability by a third. Fertilization significantly improved the productivity of the evaporative fluxes by increasing transpiration (Ecosan median: +2.8%, 4.7 mm season^-1) and reducing soil and canopy evaporation (Ecosan median: −1.7%, −4.5 mm season^-1). In situ WH did not generally affect the river flow regimes. Occasionally, significant regime changes occurred due to enhanced lateral and shallow aquifer return flows, such as higher risk of flooding and increased low flows.<br /> The third study focuses on improving model performance through a more efficient use of sparse climatic data. Two approaches to obtain climatic time series for SWAT were compared: the conventional centroid method and time-dynamic Voronoi tessellation. Climatic time series were estimated with each method for each sub-basin in Southern Africa. The Voronoi method utilized all available precipitation and temperature data, but the centroid method used only 14.5% and 82.5%, respectively. With the centroid method, sub-basin time series were on average 42% and 63% incomplete, respectively. With the Voronoi method, all sub-basin time series were complete. SWAT was fed with each climate dataset. Each model setup was independently calibrated and validated against 213 discharge stations and smallholder maize yields from eight provinces in South Africa. A similar performance was obtained for maize yield with both methods, but discharge simulations improved significantly with the Voronoi method. The R² between observed and simulated daily discharge increased from 0.23 to 0.39 in the calibration period and from 0.41 to 0.48 in the validation period on average. The Voronoi method improved the simulation of the river flow regime (i.e. the magnitude, frequency, timing, and flashiness of flow). The largest improvements were obtained in data scarce situations, and at relatively high spatial and temporal resolutions. In essence, the Voronoi method provides a more robust climatic dataset for assessing impacts of agricultural management alterations with the SWAT model in Southern Africa.<br /> The fourth study quantifies the potential impacts of in situ WH, external WH, and Ecosan in Southern Africa. Ecosan significantly improved the maize yields and crop water productivity across Southern Africa, while in situ WH and external WH were only beneficial in specific seasons and locations. On average, Ecosan increased maize yields by 12.4% and transpiration by 2.2% (p-values: &lt;2.2x10⁻¹⁶). WH did not significantly affect the yield, transpiration or river flow regimes on the Southern Africa scale (pvalues: &gt;0.7). However, external WH more than doubled the yields in specific situations, with a supplemental irrigation amount of less than 40 mm season⁻¹. The areas where in situ WH and external WH were most beneficial are located in the Limpopo River basin, the central Free State, and along the southeast coast in KwaZulu-Natal and Eastern Cape. WH was particularly beneficial for the lowest yields. External WH generally had a larger impact than in situ WH. Significant water and nutrient demands remained even with Ecosan and WH management. By fully addressing these demands, the yields increased by a factor of four. Fertility enhancements raised yield levels but also the yield variability, while soil moisture enhancements particularly improved the temporal yield stability.<br /> In conclusion, enhanced management of locally available water and nutrient resources with WH and Ecosan technologies can increase smallholder agricultural productivity and food production: moisture enhancements in specific conditions (typically for the lowest yields), and fertility enhancements throughout Southern Africa. To use the available water more productively, it is paramount to increase soil fertility. To reduce spatial and temporal yield variabilities, it is necessary to address crop water demands. Simultaneous approaches are the most promising.

Dissolved organic matter (DOM) is a heterogenous, hard to define mixture of organic compounds that is present in natural waters and consists of degradation- and transformation products of biomass. DOM, which comprises humic and fulvic acids as the main components, has an important influence on a large variety of chemical reactions in the environment.<br />Chromophoric moieties of DOM, also termed colored dissolved organic matter (CDOM) are the most important light-absorbers in natural waters and are for example responsible for the yellowbrownish color of many humic-influenced lakes and rivers. Absorption by DOM leads to attenuation of the light-intensity in deeper layers of the water column. However, in the upper parts of the column, near the surface, DOM participates in the production of numerous reactive species such as excited triplet states of DOM (³DOM^*), singlet oxygen (¹O₂) and hydroxyl radical (^•OH), that all have an important impact on the photochemical transformation of aqueous contaminants. Thus, in many cases DOM acts as photosensitizer, meaning that it accelerates photochemical processes. [...]<br /><br />Gelöstes organisches Material (dissolved organic matter, DOM) ist ein heterogenes, schwer zu definierendes Stoffgemisch, das sich aus den Abbau- und Umwandlungsprodukten von Biomasse zusammensetzt. DOM ist allgegenwärtig in natürlichen Gewässern und kommt dort in unterschiedlicher Konzentration vor. Es besteht hauptsächlich aus Humin- und Fulvinsäuren und hat einen grossen Einfluss auf verschiedenste chemische Reaktionen in der Umwelt.<br />Die Chromophore des DOM, auch gefärbtes organisches Material (colored dissolved organic matter, CDOM) genannt, sind die wichtigsten lichtabsorbierenden Bestandteile natürlicher Gewässer und sind zum Beispiel für die gelb-bräunliche Farbe von vielen von Huminstoffen beeinflussten Seen und Flüssen verantwortlich. Die Absorption des DOM sorgt für eine Abschwächung der Lichtintensität in tieferen Wasserschichten. In den oberen Bereichen der Gewässer bilden sich jedoch unter der Beteiligung von DOM zahlreiche kurzlebige reaktive Spezies, wie zum Beispiel angeregte Triplettzustände des DOM (³DOM^*), Singulett-Sauerstoff (¹O₂) und das Hydroxyl-Radikal (^•OH), die alle für den indirekten photochemischen Abbau von Schadstoffen eine grosse Bedeutung haben. In vielen Fällen wirkt DOM daher als Photosensibilisator, also als Beschleuniger des photochemischen Abbaus von Schadstoffen. [...]

In many regions of the world, diffuse phosphorus (P) losses from agricultural land cause eutrophication of surface waters, leading to a loss of their ecosystem functions. In Switzerland, severe eutrophication problems occur in some lakes on the Swiss Plateau, such as Lake Sempach and Lake Baldegg. A reduction of diffuse P losses is needed to enhance the water quality of these lakes. Various international studies reported that P found in runoff of a catchment outlet originated from a small fraction of the catchment only. Directing mitigation options to those critical source areas (CSA) is considered to be the most costeffective and efficient way to reduce diffuse P losses. Therefore, tools that enable reliable predictions of CSAs, preferably on the basis of easily available data, are needed to guide the implementation of mitigation measures. The main objective of this study was to assess and enhance the predictive capabilities of the parsimonious Rainfall-Runoff-Phosphorus (RRP) model, which determines CSAs using a low amount of input data. The model was developed for catchments dominated by grassland with low permeability subsoils. We improved the model and tested the reliability of its predictions, applying it to the Stägbach catchment which delivers high P loads to Lake Baldegg and was not used for calibration. [...]<br /><br />Weltweit verursachen diffuse Phosphorverluste aus landwirtschaftlichen Gebieten die Eutrophierung von Gewässern, was zu einem Verlust ihrer Ökosystemfunktionen führt. In der Schweiz treten derartige Eutrophierungsprobleme in einigen Seen des Schweizer Mittellandes auf, wie zum Beispiel dem Sempachersee und dem Baldeggersee. Eine Reduzierung des Phosphorverlustes ist nötig, um die Gewässerqualität in diesen Seen zu verbessern. Verschiedene internationale Studien berichten, dass Phosphor (P) im Gebietsabfluss häufig nur aus einem kleinen Teil des Einzugsgebietes stammt. Es wird angenommen, dass die Implementierung von Massnahmen in diesen beitragenden Gebieten (critical source areas CSA) die kostengünstigste und effizienteste Methode ist, um P Einträge in Gewässern zu verringern. Um derartige gezielte Massnahmen zu ermöglichen, braucht es Werkzeuge, die zuverlässige Vorhersagen von CSAs ermöglichen, vorzugsweise auf der Grundlage von verfügbaren Daten. Das Ziel dieser Arbeit war es, die Vorhersagefähigkeit des Niederschlags-Abfluss-Phosphor Modells RRP (Rainfall-Runoff-Phosphorus Model), welches nur wenig Eingangsdaten benötigt, zu bewerten und zu verbessern. Das Modell wurde für Einzugsgebiete entwickelt, in denen Graslandflächen und schlecht drainierte Böden dominieren. Wir verbesserten das Modell und testeten die Zuverlässigkeit der Modellvorhersagen, indem wir das Modell auf das Stägbach Einzugsgebiet, welches hohe PFrachten in den Baldeggersee liefert und nicht für die Kalibration verwendet wurde, anwendeten. [...]

Climate change and eutrophication are main reasons for large-scale alterations of aquatic ecosystems. Dramatically increased or persistent appearances of hypoxia and anoxia have caused mass mortality events or even species extinction. More specifically, human induced eutrophication since the industrial revolution has been a major driver for a dramatic decline of hypolimnetic oxygen concentrations in lakes. Although water treatment and remediation efforts have largely reduced nutrient levels and eutrophication, oxygen depletion still exists. The goal of this thesis was to reconstruct past oxygen depletion and eutrophication with sedimentary proxies. These reconstructions help to understand factors and processes that lead to oxygen depletion, which is a basis for the development of remediation strategies and the assessment of future impacts. Sedimentary proxies were studied in selected Swiss lakes (Rotsee, Lake Zurich), Amvrakikos Gulf (Greece) and the Black Sea (Romanian Shelf). [...]<br /><br />Klimawandel und Eutrophierung sind Hauptgründe für grossräumliche Veränderungen aquatischer Ökosysteme. Vor allem die dramatische Abnahme der Sauerstoffgehalte wird zunehmend als Grund für das häufigere Auftreten von Massen- und Artensterben erkannt. In Seen hat durch Eutrophierung seit der industriellen Revolution eine dauerhafte Abnahme der Sauerstoffgehalte im Hypolimnion stattgefunden. Obwohl Abwasserreinigungs- und Sanierungsmassnahmen zu einer Reduktion der Nährstoffgehalte geführt haben, haben sich die Sauerstoffgehalte nicht wie erhofft erhöht. Das Hauptziel dieser Dissertation war die Rekonstruktion von Gewässereutrophierung und Sauerstoffverarmung mithilfe sedimentärer Indikatoren. Hierzu wurden sedimentäre Indikatoren in den Schweizer Seen Rotsee und Zürichsee, sowie im Ambrakischen Golf und dem Schwarzen Meer untersucht. [...]

The role aquatic systems play in the global carbon cycle has become more relevant in recent years since it has been shown that they bury and transform more carbon than the whole of the oceans. Moreover, at least half of the natural sediment load to the oceans is now trapped by manmade impoundments, which are steadily increasing and thus retaining and remineralizing even more of the carbon that once reached the oceans. The efflux of carbon-based greenhouse gases from natural and artificial aquatic systems is an important negative climatic feedback. In particular, the dynamics of methane (CH₄), a much more potent greenhouse gas than carbon dioxide, has been studied in various systems and is of particular importance for reservoirs, which should be a more-or-less carbon-neutral energy source. Surface diffusion of CH₄ has been studied often and recently attention has turned to the release of CH₄-rich water through large tropical dams. A few studies have shown that CH₄ ebullition (bubbling) is likely the most efficient and dominant emission pathway in natural shallow systems, but less research has been done on its role in efflux from reservoirs. In general, ebullition dynamics is understudied relative to its potential significance in the carbon cycle of natural and manmade aquatic systems, mostly due to its stochastic and episodic nature complicating its accurate assessment. [...]<br /><br />In den letzten Jahren konnte gezeigt werden, dass aquatische Systeme für den globalen Kohlenstoffkreislauf relevant sind, da sie mehr Kohlenstoff ablagern und transformieren als die Ozeane. Zusätzlich wird zur Zeit mindestens die Hälfte der natürlichen Sedimentfracht in die Ozeane in künstlichen Stauseen zurückgehalten, und da deren Zahl kontinuierlich zunimmt, wird sogar mehr Kohlenstoff zurückgehalten und remineralisiert als früher die Ozeane erreicht hat. Der Ausstoss von kohlenstoffartigen Treibhausgasen aus natürlichen und künstlichen aquatischen Systemen ist eine wichtige negative Klimarückkopplung. Im Besonderen ist die Dynamik von Methan (CH₄), das ein viel wirksameres Treibhausgas als Kohlendioxid ist, in verschiedenen Systemen untersucht worden und ist von spezieller Wichtigkeit in Stauseen, die eine mehr oder weniger kohlenstoffneutrale Energieressource sein sollten. Die Oberflächendiffusion von CH₄ ist oft untersucht worden, wobei sich in letzter Zeit die Aufmerksamkeit auf den Abfluss von CH₄-reichem Wasser aus grossen tropischen Stauseen konzentriert hat. Einige Studien haben gezeigt, dass CH₄-Blasenströme wahrscheinlich der effizienteste und dominante Emissionsweg in natürlichen untiefen Systemen ist, es gibt jedoch weniger Untersuchungen zu deren Rolle für die Emissionen aus Stauseen. Generell ist die Blasenstromdynamik aufgrund ihrer stochastischen und episodischen Charakteristik, die eine genaue Beurteilung kompliziert macht, im Verhältnis zu ihrer potentiellen Signifikanz bezüglich des Kohlenstoffkreislaufs in natürlichen und künstlichen aquatischen Systemen nicht genügend untersucht. [...]

Floodplains are among the most valuable ecosystems on the planet because they provide important ecosystem services such as flood mitigation, water purification, and habitat formation. Floodplains also act as biogeochemical reactors that impact particle, nutrient and carbon (C) transport between headwaters and oceans. However, the effect of floodplain carbon and nutrient cycling on river biogeochemistry is not well constrained, particularly in the tropics. The functioning of floodplains strongly depends on alternating water levels that cause water flows from the river to the floodplain and back. This hydrological river-floodplain exchange is a key process for deposition and mobilization of organic matter (OM) and nutrients, and the migration of biota. Any changes in the hydrology can thus compromise the natural functioning of such systems. Dams built along rivers with floodplains, whether for hydropower generation or irrigation, have the potential to impact the flooding regime and nutrient cycles. Ultimately, dam impacts on floodplains in temperate and boreal systems have been studied in much greater detail than in the tropics, but the increasing number of dams in tropical catchments requires better understanding of these processes. [...]<br /><br />Die nützlichen Funktionen von Flussauen wie Hochwasserschutz, Wasserreinigung, oder Lebensraum machen diese zu äusserst wertvollen Ökosystemen. Auengebiete beeinflussen auch den Partikel, Nähr- und Kohlenstoff (C)-Transport zwischen Oberläufen von Flüssen und Ozeanen. Dieser Einfluss ist bislang wenig erforscht, vor allem in tropischen Gebieten. Auen sind auf sich ändernde Wasserstände angewiesen, die dazu führen, dass Wasser vom Fluss in die Aue und wieder zurück fliesst. Dieser hydrologische Austausch ist ein wichtiger Prozess für die Ablagerung und Mobilisierung von organischem Material (OM), Nährstoffen und für die Migration von Lebewesen. Veränderungen der Hydrologie, zum Beispiel durch Staudämme (für Wasserkraft oder Bewässerung) oberhalb von Auengebieten, können daher die natürlichen Funktionen von Auen beeinträchtigen und dabei Nährstoffkreisläufe beeinflussen. Die Auswirkungen von Staudämmen auf Auengebiete wurden bisher vor allem in gemässigten und borealen Systemen erforscht, aber die zunehmende Anzahl von Staudämmen verlangt nach einem besseren Verständnis dieser Prozesse in tropischen Gebieten. [...]

In a world increasingly modified by human activities, studying successional trajectories can aid in the interpretation and prediction of ecosystem responses to anthropogenic disturbances, such as changes in biodiversity and fluxes of matter and energy. Emphasis in the past has been placed on the importance of plant community succession, whereas the role of microbial communities as drivers of, and respondent to, ecosystem succession has been largely neglected, in spite of the ubiquity of microbes on earth and their importance for biogeochemical cycles. Owing to their limited complexity, early successional stages of ecosystems may also provide excellent opportunities for testing central ecological questions, such as the linkage between biodiversity and ecosystem functioning. [...]<br /><br />Dans un monde de plus en plus modifié par les activités humaines, l’étude de la succession des écosystèmes peut se révéler très utile pour prédire et interpréter les réponses aux perturbations subies par les écosystèmes. Jusqu’à récemment, les recherches faites dans ce domaine ont placés beaucoup d’importance dans l’étude de la succession des communautés végétales. Toutefois les communautés microbiennes, à cause de leur ubiquité sur terre et de leur importance dans les cycles biogéochimiques, sont des facteurs potentiels de changement importants dans la succession des écosystèmes. D’autre part, la complexité limitée des écosystèmes dans les premiers stades de développements fait de ces systèmes d’excellentes opportunités pour tester des questions centrales en écologie, comme la relation entre biodiversité et fonctionnement des écosystèmes. [...]

Environmental models are useful tools to test hypotheses about and enhance the understanding of biogeochemical and ecological processes in the environment. If carefully designed, these tools can quantify the knowledge of the scientific community about the future state of ecosystems under various driving conditions. Such forecasts are important for the design of ecosystem preservation plans and for the assessment of suggested management alternatives.<br />Lakes are one example of ecosystems that are strongly affected by anthropogenic influences. Important examples of such influencing factors are nutrient loads, toxic chemicals and climate. The explanation and prediction of a lake’s biogeochemistry and directly related plankton dynamics, especially under changes in these influencing factors, is of particular interest if drinking water is extracted from the lake. But also the preservation of biodiversity and the achievement of a good ecological state of the lake are important motivations for the monitoring and modeling of lake ecosystems. On the one hand, a model used for this purpose should be universal and accurate in the sense that it should represent the reality reasonably well, even if driving forces move into ranges that have not been observed in the past. On the other hand, such a model should not be too complex to facilitate its application even if only scarce data are available and to limit its computation time. [...]<br /><br />Umweltmodelle sind nützliche Werkzeuge, um das Verständnis von biogeochemischen und ökologischen Prozessen in der Umwelt zu verbessern und Hypothesen zu testen. Sorgfältig entwickelt können diese Modelle auch das Wissen über den zukünftigen Zustand von Ökosystemen unter verschiedenen Änderungen von Einflussfaktoren quantifizieren. Solche Vorhersagen sind für die Planung von Umweltschutzmaßnahmen und die Bewertungen von vorgeschlagenen Managementalternativen wichtig.<br />Seen sind ein Beispiel für Ökosysteme, die stark durch anthropogene Einfüsse beeinträchtigt werden. Wichtige Beispiele für solche Einflussfaktoren sind die Einträge von Nährstoffen und toxischen Chemikalien und das Klima. Die Erklärung und Vorhersage der Biogeochemie und damit direkt verbundenen Planktondynamik eines Sees, vor allem unter Änderungen solcher Einflussgrößen, sind speziell von Interesse, falls Trinkwasser aus dem See gewonnen wird. Wichtige Motivationen für die Beobachtung und Modellierung von See-Ökosystemen sind allerdings auch die Erhaltung der Artenvielfalt und das Erreichen eines guten ökologischen Zustandes der Seen. Zum einen sollten die dafür verwendeten Modelle möglichst universell und präzise sein, in dem Sinne, dass sie die Realität angemessen abbilden, auch falls sich Einflussgrößen in Zukunft in Bereiche ändern die zuvor noch nicht beobachtet wurden. Zum anderen sollte ein Modell dennoch nicht zu komplex sein, um seine Anwendung auch bei wenigen verfügbaren Daten zu ermöglichen und seine Rechenzeit zu limitieren. [...]

Growing concern about the consequences of current global biodiversity loss has led to numerous research initiatives addressing relationships between biodiversity and ecosystem functioning. Streams and rivers are harbouring high numbers of species compared to other ecosystems, especially in relation to their cumulative size. At the same time, biodiversity in streams and rivers is threatened by multiple anthropogenic impacts. Despite considerable research efforts, the roles of biodiversity for funtioning of stream ecosystems remain unclear and studies addressing these questions provide mixed results. In part, this situation is a consequence of lack of detailed information on the mechanisms by which biodiversity acts on processes including assessment of the effects of various aspects of biodiversity in addition to species richness. Different environmental situations further contribute to variations in the outcomes of such studies. [...]<br /><br />Die zunehmende Besorgnis über die Konsequenzen des globalen Artensterben hat in den letzten Jahrzehnten zu vielen Forschungsinitiativen geführt mit dem Ziel, die Bedeutung der Biodiversität für Ökosystemen, gleichzeitig sind viele Organismen in Bächen und Flüssen durch verschiedene menschliche Einflüsse bedroht. Trotz vielfältigen Untersuchungen sind die Rollen der Biodiversität für das Funktionieren von Bachökosystemen unklar, auch weil bisherige Untersuchungen zu unterschiedlichen Schlussfolgerungen gekommen sind. Zum Teil sind die unterschiedlichen Resultate auf fehlende Information über die zugrundliegenden Mechanismen, mit denen Biodiversität Ökosystemfunktionen beeinflusst, zurückführen. Diese Mechanismen beinhalten auch verschiedene Aspekte der Biodiversität neben der Anzahl Arten, welche unabhängige Effekte auf Prozesse haben können. Zusätzlich könnten weitere Eigenschaften des Ökosystems (z.B. Umweltbedingungen) die Resultate von solchen Studien beeinflussen. [...]

Bacteria belonging to the genus of <em>Listeria </em>are Gram-positive, rod-shaped, non sporeforming<br />cells. They can be found ubiquitously in nature. Within this genus two species, <em>L. monocytogenes </em>and<em> L. ivanovii</em>, are of particular interest since they are described to be pathogenic to humans and animals, respectively. Frequent signs of a listeriosis, the disease caused by <em>Listeria </em>infection, are general flu-like symptoms and in severe cases, meningitis, encephalitis, septicaemia or stillbirth in pregnant women. With 30 to 40% the disease’s mortality rate is high, although listeriosis has a rather low incidence in human. The disease especially threatens young, old, pregnant and immunocompromised people. Ingestion of contaminated food products is the main route of infection by <em>Listeria</em>. In many European countries human listeriosis is reported to be a disease of increasing relevance that is becoming, due to its high mortality rate, one of the most perilous food-related infectious diseases. [...]<br /><br />Bei Bakterien der Gattung <em>Listeria </em>handelt es sich um Gram-positive, stäbchenförmige, nicht sporenbildende Zellen. <em>Listerien </em>kommen in der Natur ubiquitär vor. Innerhalb dieser Gattung sind vor allem die beiden Arten <em>L. monocytogenes</em>, als Krankheitserreger für Menschen und<em> L. ivanovii</em>, als Tierpathogene von Bedeutung. Häufige Symptome einer Listeriose, der durch <em>Listerien </em>verursachten Krankheit, sind Grippe-ähnliche Symptome, in schweren Fällen Meningitis, Enzephalitis, oder auch Totgeburten bei Schwangeren. Obwohl die Inzidenz der humanen Listeriose gering ist, ist die Sterblichkeitsrate mit 30 bis 40% sehr hoch. Junge, Alte, Schwangere und Menschen mit geschwächtem Immunsystem sind besonders von der Krankheit betroffen. [...]

Benzo(a)pyrene (BaP) is a ubiquitous pollutant derived by incomplete combustion of organic matter. BaP is classified by the International Agency of Cancer (IARC) as carcinogenic to humans and is controlled in drinking water in the United States and Europe. BaP needs to be metabolized to become carcinogenic. Its metabolism is induced by the interaction between  BaP and the aryl hydrocarbon receptor (AhR) and subsequent gene regulation. Despite this general knowledge, details about BaP entry into cells, distribution and internal concentrations able to elicit a cellular response are largely unexplored and mechanisms of actions incompletely understood. This PhD thesis therefore aims to investigate in a time and concentration dependent manner the molecular response of a murine hepatoma cell line, Hepa1c1c7, exposed to BaP, combining high throughput techniques, bioinformatics, phenotype characterization and chemical analysis. [...]

Drinking water with elevated fluoride (F) concentrations affects the health of millions of people world-wide. Several techniques have been developed to remove F from drinking water. One viable, effective and inexpensive option, particularly for developing countries, is filtering using bone char. Fluoride uptake on bone char is primarily controlled by the main compound of bones, calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP), which forms fluorapatite (Ca₁₀(PO₄)₆F₂, FAP) in presence of F. The addition of solid calcium-phosphate pellets to the bone char filter media has significantly improved the F uptake capacity in these contact precipitation filters. The pellets dissolve, releasing calcium (Ca) and phosphate (PO₄) to solution, which then can precipitate as a new phase incorporating F. However, these filters could still be optimized to improve their efficiency.<br />This thesis investigates the uptake of F in apatitic systems under environmentally relevant conditions. The main aim of this work is to gain insights into the predominant processes controlling F uptake in bone char and contact precipitation filter systems to provide a basis for filter optimization. [...]<br /><br />Erhöhte Fluoridkonzentrationen in Trinkwasser gefährden weltweit die Gesundheit von Millionen von Menschen. Viele Technologien wurden entwickelt, um das Fluorid (F) aus dem Trinkwasser zu entfernen. Eine praktikable, effektive und gleichzeitig relativ kostengünstige Methode ist die Nutzung von Knochenkohle als Filtermaterial, welche besonders für Entwicklungsländer interessant ist. Die Fluoridaufnahme auf Knochenkohle wird vorrangig durch den Hauptbestandteil der Knochen bestimmt, dem Calciumphosphat-Mineral Hydroxyapatit (Ca₁₀(PO₄)₆(OH)₂, HAP), welches sich in Anwesenheit von Fluoridionen zu Fluorapatit (Ca₁₀(PO₄)₆F₂, FAP) umwandelt. Die Ergänzung von Calciumphosphat-Pellets zur Knochenkohle als Filtermaterial verbessert signifikant die Fluoridaufnahme in diesen <em>Contact Precipitation Filtern</em>. Die Pellets lösen sich auf, gegeben Calcium (Ca) und Phosphat (PO₄) in Lösung, so dass diese Ionen als neue Mineralphasen ausfallen und dabei F binden können. Jedoch können diese Filter noch bezüglich ihrer Fluoridaufnahmekapazität optimiert werden.<br />Diese Arbeit untersucht die Aufnahme von F in apatitischen Systemen unter Umweltbedingungen. Das Hauptziel der Arbeit ist der Einblick in die dominierenden Prozesse, welche die Aufnahme von F auf Knochenkohle und in <em>Contact Precipitation</em> Filtersystemen kontrollieren, um eine Basis zur Filteroptimierung zu schaffen. [...]

Microbes, such as heterotrophic bacteria, are crucial in the functional ecology of terrestrial and aquatic ecosystems, being the driving force behind metabolic processes, nutrient retention and cycling, and trophic links with secondary consumers. Bacterial biodiversity, including the actual genetic and functional spectrum, has only recently been investigated and knowledge about alpine lotic ecosystems and their local bacterial communities, in particular, is even scarcer. The ongoing climate-induced change in ecosystems is very likely to influence bacterial communities and consequently ecosystem functioning. To what extent shifts in ecosystem functioning due to future landscape transformation will be buffered by a potential resistance/resilience of bacterial communities is mostly unknown. Glaciated alpine floodplains provide excellent opportunities to test such fundamental ecological questions as they have a high degree of insularity, biotic endemicity and are sensitive to environmental change. In addition, these landscapes harbor structured, hydrologically interconnected and spatio-temporally heterogeneous landscape features such as different stream types or interspersed lakes. These features can provide additional mechanistic understanding of how structures within landscapes drive biodiversity and ecosystem functioning in space and time. Such knowledge could be extrapolated to similar ecosystems that potentially undergo future landscape changes induced by climate change and would improve models of ecosystem services. [...]<br /><br />Mikroorganismen, wie heterotrophe Bakterien, spielen eine entscheidende Rolle in der funktionellen Ökologie von terrestrischen und aquatischen Ökosystemen. Sie stellen die treibende Kraft hinter metabolischen Prozessen, Nährstoffrückhaltung und Wiederverwertung wie auch die Verbindung mit höheren trophischen Stufen dar. Bakterielle Biodiversität, welche die genetische als auch funktionelle Vielfalt darstellt, ist erst seit relativ kurzer Zeit im Fokus der Wissenschaft. Dies gilt insbesondere für alpine Fliessgewässer und ihre bakteriellen Gemeinschaften.<br />Die durch den fortschreitenden Klimawandel induzierte Veränderung von Ökosystemen wird höchst wahrscheinlich die bakteriellen Gemeinschaften beeinflussen und konsequenterweise die mit ihnen verbundenen Ökosystemprozesse. Zu welchem Teil Veränderungen von Ökosystemfunktionen durch die zukünftigen Landschaftsveränderungen von einer potentiellen Resistenz/Anpassungsfähigkeit der bakteriellen Gemeinschaft abgefedert wird, ist mehrheitlich unbekannt. Vergletscherte alpine Überschwemmungsebenen bieten eine ausgezeichnete Möglichkeit, solchen fundamentalen ökologischen Fragen nachzugehen, da sie durch ein hohes Mass an Abgeschlossenheit, Endemismus und Sensitivität für Umweltveränderungen charakterisiert sind. Zusätzlich beinhalten sie strukturierte, hydrologisch verbundene, räumlich und zeitlich heterogene Landschaftsmerkmale, wie z.B. verschiedene Flusstypen oder zwischengeschaltete Stillgewässer. Die Erforschung dieser Aspekte kann zusätzliches Verständnis für die landschaftsgebundenen Faktoren generieren, welche die bakterielle und funktionelle Biodiversität beeinflussen. Dieses Wissen könnte man auf ähnliche Ökosysteme übertragen, die durch den Klimawandel beeinflusst werden und dadurch Modelle, welche Ökosystemdienstleistungen voraussagen, verbessern. [...]

The industrial and domestic use of chemicals has led to large emissions of organic micropollutants into the environment. Knowledge of contaminants’ degradability in environmental systems is essential for proper risk assessment and further development of adequate remediation strategies for contaminated sites. Transformation processes of contaminants can be identified and quantified by means of compound-specific isotope analysis (CSIA). Depending on the chemical bond(s) that are cleaved or formed during a reaction, the isotopic ratio of the reactant changes systematically as a consequence of kinetic isotope effects (KIE). This change can be indicative for the occurring reaction and the derived apparent KIEs provide important information on the reaction mechanism. Although many emerging micropollutants exhibit reactive N-containing functional groups, only few studies have used CSIA to assess their transformation. This PhD thesis focuses on the transformation of aromatic N-alkyl amines, which are widely used in the chemical industry and can also represent the reactive moiety in larger contaminant molecules. Once present in the environment they are subject to oxidative transformation via multiple reaction pathways, which may occur simultaneously. [...]<br /><br />Der verbreitete Einsatz von Chemikalien in der Industrie, der Landwirtschaft sowie in Haushalten hat zur Belastung der Umwelt mit organischen Mikroverunreinigungen geführt. Die Risikoabschätzung der Umweltverschmutzung sowie die Entwicklung von entsprechenden Sanierungsstrategien setzen fundierte Kenntnisse über das Verhalten der Schadstoffe in der Umwelt voraus. Die Auswirkungen der organischen Schadstoffe auf das Ökosystem und die Menschen wird weitgehend durch deren Abbau bestimmt. Ein qualitativer und quantitativer Nachweis von solchen Abbauprozessen wird durch die Einzelstoff-Isotopenanalyse (Compound-Specific Isotope Analysis, CSIA) ermöglicht. Die CSIA basiert darauf, dass die Bildung und/oder Spaltung einer chemischen Bindung während einer Reaktion dem kinetischen Isotopeneffekt (KIE) unterliegt. Der KIE führt zu einer systematischen Änderung der stabilen Isotopenzusammensetzung des Reaktanden, die charakteristisch für diese Reaktion ist. Obwohl zahlreiche organische Mikroverunreinigungen reaktive stickstoffhaltige funktionelle Gruppen enthalten, existieren bisher nur sehr wenige Studien, die die relevanten Transformationsprozesse mittels CSIA untersucht haben. Diese Arbeit befasst sich mit der Schadstoffklasse der aromatischen N-alkylierten Amine, weil diese in der chemischen Industrie sehr verbreitet eingesetzt werden und weil sie zudem als reaktive Strukturen in grösseren, strukturell komplexeren Schadstoffmolekülen, wie z.B. Antibiotika, vorkommen. Aromatische Amine werden in der Umwelt mittels verschiedener Oxidationsreaktionen zu Transformationprodukten umgesetzt, wobei viele dieser Prozesse auch gleichzeitig stattfinden können. [...]

Infectious diseases are a natural process that reflects a long evolutionary history between host and parasites. Therefore a sustainable balance between host and parasites in nature is presumably an indication for a “normal” functioning and “healthy” ecosystem. There is increasing evidence that anthropogenic induced stresses may disrupt this natural balance thereby increasing the impact of disease on host populations. Host genetic diversity can play an important role in buffering populations against environmental stresses and disease spread.<br />In my doctoral research, I explored how an anthropogenic pollutant (herbicide) affects the strength and direction of host-parasite interactions. I used a host-parasite system, consisting of the diatom <em>Asterionella formosa</em> Hassall and its obligatory host-specific chytrid parasite <em>Zygorhizidium planktonicum</em>. I also characterized the genetic diversity and population structure of the host A. formosa on different spatial scales. [...]<br /><br />Les maladies infectieuses sont un processus naturel qui révèle une longue histoire évolutionnaire entre hôtes et parasites. De ce fait, un équilibre durable entre hôtes et parasites dans la nature doit être l'indicateur d'un écosystème "en bonne santé" qui fonctionne "normalement". Il est de plus en plus évident que les divers stress anthropiques peuvent créer un déséquilibre et ainsi accroître l'impact d'une épidémie sur les populations d'hôtes. La diversité génétique au sein des hôtes peut aussi jouer un rôle tampon important contre les stress environnementaux et la propagation des infections.<br />Au cours de mes recherches doctorales, j'ai cherché à savoir de quelle façon un polluant anthropique (un herbicide) affectait la force et la direction des interactions entre hôtes et parasites. Pour cela, j'ai utilisé un système hôte-parasite composé de la diatomée Asterionella formosa et de son parasite obligatoire spécifique, le chytride Zygorhizidium planctonicum. J'ai également caractérisé la diversité génétique et la structure de la population de l'hôte A. formosa à différentes échelles spatiales. [...]

This thesis focuses on the use of the short-lived radon isotope ²²⁰Rn (half-life 55.6 s) as environmental tracer in groundwater and soil gas. Radon is a natural radioactive noble gas and its isotopes are produced by alpha decay of their precursor radium isotopes. From radium bearing minerals in the subsurface, radon isotopes are released to the environment, i.e. groundwater and soil gas.<br />The longer-lived ²²²Rn (half-life 3.8 d) is used for decades as environmental tracer in subsurface fluids The short lived ²²⁰Rn, however, gained much less interest in environmental sciences and was only in soil gas rarely applied as a tracer. The initial motivation of this thesis, therefore, focused on the determination and use of ²²⁰Rn as a tracer in aquatic systems. Here, ²²⁰Rn could be used to study small scale processes and as a co-tracer for the long-lived ²²²Rn in aquatic systems. In order to enable the use of ²²⁰Rn as a tracer in aquatic systems, the sampling and measurement technique of ²²⁰Rn-in-water concentrations had to be optimized. As the used radon isotope detector is an radon-in-air detection system, the water to be analyzed has to be degassed before analysis. By testing and modifying different degassing devices and by adding an additional air loop with an adjustable air pump to the detection system, the travel time of water and air between sampling and radon analysis was reduced. Consequently, the feasibility of ²²⁰Rn-in-water detection was proven in laboratory experiments. When the system was applied to the fiel to sample natural groundwater, however, significan concentrations ²²⁰Rn were measured only in one special case, in which water was sampled directly from a pipe with inner coatings of ²²⁰Rn-producing material. In all other cases, no ²²⁰Rn was detected in water. [...]

Temperature, suspended-particle distribution and sedimentation were surveyed and modeled in two pumped-storage hydropower plants, both located in Switzerland.<br />One of them, the Grimselsee-Oberaarsee plant, consists of two reservoirs connected with a pumped-storage scheme since more than 30 years. Due to different glacier coverage of the catchment, the two reservoirs exhibit different particle concentration and sedimentation. Our investigation performed between 2007 and 2009 shows that the originally clearer reservoir (Oberaarsee) has become colder, more turbid and subject to higher sedimentation, while pumped-storage operations have decreased these parameters in the formerly more turbid reservoir (Grimselsee). However, pumped-storage operations show no direct effect on particles, as particlesize changes due to the turbulent shear stress occurring in the penstocks could not be determined. [...]<br /><br />Temperatura, particelle in sospensione e sedimentazione sono state oggetto di studio in due diversi sistemi di pompaggio/turbinaggio, entrambi situati in Svizzera.<br />Il primo, Grimselsee-Oberaarsee, consiste in due laghi artificiali connessi ormai da più di 30 anni. A causa della presenza dei ghiacciai, che variano da un bacino imbrifero all’altro, la concentrazione di particelle e la sedimentazione risulta essere differente nei due laghi. Le nostre campagne di studio (periodo 2007-2009) mostrano infatti che, causa pompaggio/turbinaggio il lago inizialmente più limpido (Oberaarsee) si è intorbidito, raffreddato ed è aumentata la sedimentazione mentre che nel lago originariamente più torbido (Grimselsee) i parametri appena elencati sono diminuti. L’effetto delle pompe/turbine resta confinato ai due laghi artificiali, anche perché una analisi del diametro delle particelle prima e dopo il passaggio attraverso le macchine idrauliche (origine di sforzi turbulenti di taglio) non ha evidenziato variazioni. [...]

This work focuses on the combined measurement of (stable) noble gas and oxygen concentrations in riparian groundwaters. The aim of this work is to study the oxygen dynamics in such groundwaters in terms of separating biogeochemical mediated concentration changes from physical exchange and transport mechanisms, in order to both quantify oxygen input into and oxygen turnover of riparian groundwaters.<br />Noble gases are generally not affected by biogeochemical reactions, hence their dissolved concentrations depend on physical processes only. One significant characteristic of such a process is the temperature dependence of atmospheric solubility, i.e. the equilibrium of gas exchange between an open water body and the atmosphere, which is used in reconstructing past temperatures that prevailed during last air/water partitioning. However, noble gases in groundwater are often found to be super saturated with respect to atmospheric solubility. Due to the air-like composition and the actual atmospheric origin of this concentration surplus, the term “excess air” is commonly used to denote it. In the last decade the mechanism of excess air formation, i.e. the complete or partial dissolution of entrapped air into the groundwater body, was thoroughly studied. The thereby developed models are widely used to improve quantitative interpretation of measured noble gas concentrations in terms of temperature reconstruction and groundwater age determination. [...]<br /><br />Diese Arbeit befasst sich mit der Beschreibung und Entwicklung einer Messmethode, welche erlaubt gleichzeitig Sauerstoff- und Edelgaskonzentrationen in Grundwasser zu quantifizieren. Ziel dieser Arbeit ist es, die Sauerstoffdynamik im flussnahen Grundwasser zu untersuchen, wobei physikalische und biogeochemische Prozesse, welche die Sauerstoffkonzentration ändern, gesondert quantifiziert werden müssen, um den Sauerstoffeintrag und den mikrobiellen Sauerstoffumsatz zu bestimmen.<br />Edelgase sind chemisch inert. Folglich werden Konzentrationsänderungen von in Wasser gelöster Edelgase ausschliesslich durch physikalische Prozesse verursacht. Der Bekannteste dieser Prozesse ist der Gasaustausch eines Wasserkörpers mit der Atmosphäre. Die Löslichkeit der Gase, d.h. die im Gleichgewicht des Gasaustausches eingestellte Konzentration, ist abhängig von der Wassertemperatur. Im Grundwasser sind die meisten Edelgaskonzentrationen bezüglich dieser Löslichkeit allerdings übersättigt, wobei die elementare Zusammensetzung dieses Überschusses oft ähnlich derjenigen der Atmosphäre ist. Deswegen wird dieser Überschuss als “Excess Air” bezeichnet, was dem deutschen Begriff “Luftüberschuss” entspricht. Modelle, welche die Bildung von “Excess Air”, durch das Einschliessen und (partielle) Aufl¨osen von Luftblasen beschreiben, wurden mehrheitlich im letzten Jahrzehnt entwickelt. Methoden, zur Datierung von Grundwässern, sowie zur Rekonstruktion von Temperaturen des Wassers in der Vergangenheit, welche auf der Bestimmung der Edelgaskonzentrationen basieren, vertrauen auf diese Modelle. [...]

Communities in the wild are subject to a multitude of abiotic and biotic stressors. In turn, environmental stressors acting on the individual level can further influence population and community structure. In my doctoral research, I studied the effect of parasites and pesticides on host individuals as well as on hosts in experimental communities. I used several <em>Daphnia </em>(water flea) taxa and their endoparasites, as well as the pesticide diazinon. <em>Chapter 1</em> introduces these animals and the pesticide, and additionally includes a short review about host-parasite-environment interactions.<br /><br />Populationen in natürlichen Habitaten sind häufig einer Vielzahl von abiotischen und biotischen Stressoren ausgesetzt. Diese Umweltstressoren, agierend auf einzelne Individuen, können Auswirkungen auf die Struktur und Dynamik von Populationen und Gemeinschaften haben. Während meinem Doktorat habe ich den Effekt solcher Umweltstressoren, in Form von Parasiten und Pestiziden, auf einzelne Wirte als auch auf experimentelle Wirtsgemeinschaften untersucht. Als Modelsystem habe ich verschiedene <em>Daphnien </em>Arten und ihren Endoparasiten sowie das Pestizid Diazinon benutzt. Dieses Modelsystem wird zusammen mit Grundlagentheorie zum Thema Wirt-Parasiten Interaktion und deren Effekt auf die Umwelt in <em>Kapitel 1</em> beleuchtet.

In wastewater treatment plants (WWTPs), much effort and money is invested in operating and maintaining dense plant-wide measuring networks. The network primarily serves as input for the advanced control scenarios that are implemented in the supervisory control and data acquisition (SCADA) system to satisfy the stringent effluent quality constraints. Due to new developments in information technology, long-term archiving has become practicable, and specialized process information systems are now available. The steadily growing amount of plant data available, however, is not systematically exploited for plant optimization because of the lack of specialized tools that allow operators and engineers alike to extract meaningful and valuable information efficiently from the massive amount of high-dimensional data. As a result, most information contained in the data is eventually lost. [...]<br /><br />In Kläranlagen wird viel Aufwand und Geld in den Betrieb und die Wartung eines anlagenweiten Messnetzes gesteckt. Dieses Messnetz dient in erster Linie als Input für die Regelungsvorgänge, die im Prozessleitsystem definiert sind, um die strengen Grenzwerte bezüglich der Ablaufqualität zu erfüllen. Neue Errungenschaften im Bereich der Informationstechnologie ermöglichen nun eine wirtschaftliche Langzeitarchivierung und es stehen mittlerweile sogar spezialisierte Prozessinformationssysteme zur Verfügung. Allerdings wird die stetig wachsende Menge an verfügbaren Anlagedaten nicht systematisch ausgenutzt und zur Optimierung der Anlagen herangezogen. Dies ist auf das Fehlen von spezialisierten Instrumenten zurückzuführen, die es sowohl Betreibern als auch Ingenieuren ermöglichten, aussagekräftige und wertvolle Informationen aus der gewaltigen Menge hochdimensionaler Daten zu extrahieren. Folglich geht ein Grossteil der in den Daten enthaltenen Informationen verloren. [...]