Cette thèse étudie par trois modèles et une expérience les effets des interactions entre le réseau vert (basé sur la production primaire) et brun (basé sur la décomposition) sur le fonctionnement des écosystèmes. Trois interactions entre les deux réseaux sont étudiées: 1) les nutriments recyclés par tous les organismes couplent les réseaux verts et bruns par une relation de mutualisme/compétition entre les producteurs primaires et les décomposeurs; 2) les consommateurs généralistes se nourrissent de proies des deux réseaux trophiques et 3) les connexions spatiales par les consommateurs généralistes mobiles en haut des réseaux trophiques et les flux de nutriments et de détritus en bas. Les résultats montrent que ces interactions peuvent affecter le fonctionnement des écosystèmes y compris les cascades trophiques, la stabilité et l'importance relative de la chaîne verte et brune. Ces résultats conduisent à (1) de nouvelles perspectives sur la modélisation du fonctionnement des réseaux trophiques, (2) des prédictions originales, (3) des nouvelles interprétations de résultats empiriques, (4) des idées sur des différences fondamentales de fonctionnement entre types d’écosystèmes, (5) des prédictions sur la réponses des écosystèmes aux changements globaux. / This thesis studies through three models and an experiment the important effects of the interactions between the green (based on primary production) and brown (based on decomposition) food webs on ecosystem functioning. Three interactions between the two food webs are studied: 1) nutrients recycled from all organisms in the food web couple the green and brown food webs through mutualistic/competitive interaction between primary producers and decomposers; 2) generalist consumers feed on prey from both food webs; and 3) the spatial connections between the two food webs through mobile generalist consumers at the top and through nutrient and detritus fluxes at the bottom of the food webs. The results show that these interactions may affect the ecosystems functioning including trophic cascades, stability and the relative importance of green and brown food chains. These results lead to new (1) insights on the way to model food webs, (2) predictions on food web functioning, (3) interpretation of empirical results, (4) ideas to compare the functioning of different ecosystem types and (5) predictions on food web responses to global changes.

The feasibility of in situ bioremediation of Cr(VI) in groundwater and aquifer media was investigated using microcosm and mesocosm reactors inoculated with indigenous species of bacteria from dry sludge. Microcosm cores were used to simulate contaminant movement in the vadose and aquifer zones of the aquifer system. Cr(VI) breakthrough analysis through the experimental cores demonstrated successful Cr(VI) immobilisation in simulated barrier systems. Cr(VI) reduction was continuously monitored and microbial culture dynamics were evaluated using 16S rRNA genomic fingerprinting. A culture shift was observed in the microcosm cores with the emerging predominance of known Cr(VI) reducers - Enterococci from soil and Lysinibacilli from sludge - after operation for 45 days. The Cr(VI) reduction process in the columns was determined to be enzyme mediated and non-competitively inhibited by Cr(VI). The microbial cultures under microaerobic conditions depicted a threshold Cr(VI) concentration (Cr) of approximately 100 mg/L which was much higher than the target operation concentration of 40 mg/L at the proposed remediation sites. Using the Computer Program for the Identification and Simulation of Aquatic Systems (Aquasim), it was possible to predict Cr(VI) removal efficiency and the impact of Cr(VI) toxicity on culture dynamics in the barrier. The study demonstrates the potential of applying selected Cr(VI) reducing bacteria in biological permeable reactive barrier systems in preventing the spread of the pollutant into adjacent water supply aquifers. The impact of the presence of natural carbon sources was also evaluated by filtering the feed water through a saw dust bed. Reactors without added carbon source removed up to 70% Cr(VI), and no removal was observed in sterile controls. In the packed mesocosm reactor, the areas before the reactive barrier had no chromium reduction whereas most of the areas after the barrier achieved near 100% reduction. The microbial dynamics were monitored by the 16S rRNA fingerprinting after exposure to Cr(VI). After operating the microcosm reactors under oxygen stressed conditions in the presence of other soil bacteria, a community shift was expected. The soil from inoculated reactors contained a wide range of soil dwelling species of bacteria as well as the newly introduced bacteria from the dried sludge. There was a noted presence of Cr(VI) reducing bacteria, Microbacterium, Acinetobacter, Arthrobacter, Brevibacterium, Rumen bacteria, and several Enterococci in the sludge culture and Arthrobacter spp., Clostridium spp., and Klebsella spp. were amongst the evident among identified species. A non-competitive inhibition model was used for the evaluation of aerobic performances in batch experimental studies, whereas the inhibition threshold term C0-Cr/C0, was introduced for the anaerobic model performance for the reduction of chromium in batch studies. In sterile packed soil columns a model for saturated soil column with dispersion was adopted from AQUASIM 2.0. This model was used in combination with the chromium reduction rate adopted from the anaerobic batch modelling for most non sterile reactors in the microcosm performance. The study demonstrates the potential of applying selected Cr(VI) reducing bacteria in biological permeable reactive barrier systems in restraining the spread of the pollutant into adjacent water supply aquifers. The outcome of this exercise could be useful in the formulation of biological permeable barriers for protection against the spread of the pollutant from hot spots in the area. This is serves as a significant step towards a pilot study. / Thesis (PhD)--University of Pretoria, 2010. / Chemical Engineering / unrestricted

No description available.

No description available.

Multiple problems caused by urban runoff have emerged as a consequence to the continuing development of urban areas in recent decades. The increase of impervious land areas can significantly alter watershed hydrology and water quality. Typical impacts to downstream hydrologic regimes include higher peak flows and runoff volumes, shorter concentration times, and reduced infiltration. Urban runoff increases the transport of pollutants and nutrients and thus degrades water bodies adjacent to urban areas. One of the most frequently used practices to restore the hydrology and water quality of urban watersheds is bioretention (also known as a rain garden). Despite its wide applicability, an understanding of its multiple physiochemical and biological treatment processes remains an active research area. To provide a wide ability to evaluate the hydrologic input to bioretention systems, spatial and temporal distribution of storm events in Virginia were studied. Results generated from long-term frequency analysis of 60-year precipitation data demonstrate that the 90 percentile, or 10-year return period rainfall depth and dry duration in Virginia are between 22.9 – 35.6 mm and 15.3 – 25.8 days, respectively. Monte-Carlo simulations demonstrated that sampling programs applied in different regions would likely encounter more than 30% of precipitation events less than 2.54 mm, and 10% over 25.4 mm. Further experimental research was conducted to evaluate bioretention recipes for retaining stormwater nitrogen (N) and phosphorus (P). A mesocosm experiment was performed to simulate bioretention facilities with 3 different bioretention blends as media layers with underdrain pipes for leachate collection. A control group with 3 duplicates for each media was compared with a replicated vegetated group. Field measurement of dissolved oxygen (DO), oxidation-reduction potential (ORP), pH, and total dissolved solids (TDS) was combined with laboratory analyses of total suspended solids (TSS), nitrate (NO3), ammonium (NH4), phosphate (PO4), total Kjeldahl nitrogen (TKN) and total phosphorus (TP) to evaluate the nutrient removal efficacies of these blends. Physicochemical measurements for property parameters were performed to determine characteristics of blends. Isotherm experiments to examine P adsorption were also conducted to provide supplementary data for evaluation of bioretention media blends. The results show that the blend with water treatment residuals (WTR) removed >90% P from influent, and its effluent had the least TDS / TSS. Another blend with mulch-free compost retained the most (50 – 75%) total nitrogen (TN), and had the smallest DO / ORP values, which appears to promote denitrification under anaerobic conditions. Increase of hydraulic retention time (HRT) to 6 h could influence DO, ORP, TKN, and TN positively. Plant health should also be considered as part of a compromise mix that sustains vegetation. Two-way analysis of variance (ANOVA) found that single and interaction effects of HRT and plants existed, and could affect water quality parameters of mesocosm leachate. Based upon the understanding of the physiochemical and hydrologic conditions mentioned previously, a design model of a bioretention system became the next logical step. The computational model was developed within the Matlab® programming environment to describe the hydraulic performance and nutrient removal of a bioretention system. The model comprises a main function and multiple subroutines for hydraulics and treatment computations. Evapotranspiration (ET), inflow, infiltration, and outflow were calculated for hydrologic quantitation. Biomass accumulation, nitrogen cycle and phosphorus fate within bioretention systems were also computed on basis of the hydrologic outputs. The model was calibrated with the observed flow and water quality data from a field-scale bioretention in Blacksburg, VA. The calibrated model is capable of providing quantitative estimates on flow pattern and nutrient removal that agree with the observed data. Sensitivity analyses determined the major factors affecting discharge were: watershed width and roughness for inflow; pipe head and diameter for outflow. Nutrient concentrations in inflow are very influential to outflow quality. A long-term simulation demonstrates that the model can be used to estimate bioretention performance and evaluate its impact on the surrounding environment. This research advances the current understanding of bioretention systems in a systematic way, from hydrologic behavior, monitoring, design criteria, physiochemical performance, and computational modeling. The computational model, combined with the results from precipitation frequency analysis and evaluation of bioretention blends, can be used to improve the operation, maintenance, and design of bioretention facilities in practical applications. / Ph. D.

Les tests écotoxicologiques en conditions écosystémiques, tels que ceux que l’on peut réaliser en mésocosmes,présentent une plus grande pertinence écologique que les tests normalisés en laboratoire. Ilspermettent d’intégrer les interactions complexes entre les espèces, entre le biotope et la biocénose. Cependant,en contrepartie de leur complexité, ces systèmes présentent une variabilité importante qu’il s’agitde réduire, par une standardisation expérimentale poussée, ou d’identifier les facteurs explicatifs pourmieux mettre en lumière des différences entre traitements. Dans le cadre de cette thèse, nous avons enoutre fait le choix d’une espèce sur laquelle focaliser nos efforts, le poisson, ici l’épinoche à trois épines,Gasterosteus aculeatus, en le considérant comme un bon indicateur de l’état de santé du mésocosme. Ilnous est apparu plus judicieux, dans le cadre des études en mésocosmes, de se concentrer sur une espèceintégratrice en parallèle d’une analyse globale d’abondance des espèces.L’objectif de cette thèse était donc de mieux comprendre la dynamique de populations de l’épinoche àtrois épines dans les mésocosmes de l’Ineris afin d’améliorer les protocoles utilisés et l’analyse des donnéesobtenues lors des études écotoxicologiques. Pour y parvenir, des expériences ont été réalisées afinde caractériser les processus et les traits d’histoire de vie de l’espèce dans notre site d’étude ; un protocolea été proposé pour effectuer des expériences en mésocosmes ciblées sur l’étude de la dynamique despoissons ; deux années d’expérience ont permis d’acquérir des données en conditions témoins et de mieuxsaisir les facteurs confondants ; nous avons mis en application nos connaissances en évaluant les effets dubisphénol A (BPA) sur la dynamique de population de poissons exposés à 0, 1, 10 et 100 μg/L de BPA.Nous avons ainsi pu décrire et expliquer la dynamique de la population de l’épinoche dans les mésocosmespar quatre phases distinctes : une augmentation massive des effectifs en raison de la reproduction desfondateurs ; une diminution importante des effectifs en raison d’une saturation des capacités du système ;une faible reprise ; une nouvelle chute à la fin de la période de reproduction. S’agissant du BPA, des effetssignificatifs ont été mis en évidence sur les individus (atrophie des gonades), mais également à l’échellede la population (structure de la population). / Ecotoxicity tests in ecosystemic conditions, such as those that can be performed in mesocosms, providea substantial ecological relevance. They permit to integrate complex inter-species interactions, interactionsbetween the organisms and the environmental conditions, and permit to assess perturbations witha systemic view. However, in return, these systems present a high variability that should be reduced,through experimental standardization or by identifying explicative factors, to better assess the differencebetween the outputs of the different treatments. In this thesis, we also focused on one species, of fish,the three-spined stickleback (Gasterosteus aculeatus), considering that it is good indicator of the healthstatus of the experimental ecosystem. We suggest that is more appropriate to focus on an integrativespecies in parallel to a global analysis in the context of mesocosms studies.The goal of this thesis was thus to better understand sticklebacks population dynamics in INERIS mesocosmsto improve the experimental protocols and the data analysis in ecotoxicity studies. To achieve thisgoal, studies were performed to characterize life cycle traits and processes of the species ; an experimentalprotocol was proposed to perform mesocosms studies with a focus on fish population dynamics; the datafrom two years of mesocosms studies in control conditions permitted to better understand the confoundingfactors ; we applied the methodolgoy to assess the effects of bisphenol A (BPA) on fish populationdynamics with expsoure concentrations 0, 1, 10 and 100 μg/L BPA.We could describe and explain stickleback population dynamics divided by four periods: first a massiveabundance increase due to the first reproduction of the founders in the mesocosms; second an importantdecrease due to the saturation of the system ; third a short increase ; finaly a new drop due to the endof reproduction. For BPA, effects were observed both at individual and at population levels.

Periphyton biomass on artificial strips was observed monthly to see the impacts of nutrient differences on periphyton and periphyton-macroinvertebrates interaction. The experiment was conducted for four months in a mesocosm which were runned at six countries at the same time and with the same steps. Eight enclosures at two meters depth were used that four of them had high nutrient level and the other four had low nutrient level. Sediment, macrophyte, fish, plankton, benthic invertebrates and water were added at the same time and with the same way in all of the countries. Periphyton growth which formed on artificial 32 cm2 strips for June, July, August and September were brushed to filtered mesocosm water and dry mass, ash free dry mass, phosphorus content and chlorophyl-a concentrations were measured. Grazer pressure on the periphyton was observed with a laboratory experiment for July, August and September months. At the end of the mesocosm experiment macrophytes and fish were harvested. Macrophytes&rsquo / dry mass and fish&rsquo / abundance were measured. Moreover at the end of the experiment epiphyton was also measured. Three kajak cores were taken from sediment for macroinvertebrates at the end of the experiment and identified. All physical features of mesocosm enclosures and PVI data were recorded for every 2 weeks. Periphyton biomass was higher concentrations in HN enclosures than LN tanks. Only dry mass of periphyton biomass showed the opposite because of the marl deposition in LN tanks. This finding was also reinforced by epiphyton samples which was taken at the end of the experiment. LN enclosures had the more abundance of macroinvertebrate. The groups we found in sediment which had big grazer effect on periphyton such as gastropods and Chironomidae. Grazer experiment showed that grazer effect on periphyton increased in time. Although this raise, periphyton growth also increased in LN enclosures with nutrient increasing. This may be indicate that nutrient effect has a stronger effect than grazer pressure on periphyton. As it is explained before in the beginning of the experiment all of the conditions were the same except nutrient level. Thus, bottom-up effect changed the top-down control and at the end of the experiment we saw the more periphyton less macroinvertebrate and more fish in HN tanks while the opposite was seen in LN tanks.

Triclosan (TCS) is a personal care product with many fields of application and is of public interest for several years now. Monitoring studies showed that TCS is a ubiquitous chemical in the aquatic environment. Aquatic organisms are exposed to TCS in a broad range of concentrations, from ng L-1 up to lower μg L-1. TCS has a bactericidal effect for various types of gram-positive and gram negative bacteria. TCS targets a specific bacterial fatty acid biosynthetic enzyme, enoyl-[acyl-carrier protein] reductase (Schweizer, 2001). Therefore the terminal reaction in the fatty acid elongation cycle is inhibited (Levy et al., 1999). Although effects on non-target organisms are reported, the Mode of Action (MoA) of TCS is not well examined for those organisms. The aim of this PhD thesis was to investigate effects of TCS on non-target autotrophic organisms at different levels of biological complexity in the aquatic environment. In this thesis microalgae have been found to be very sensitive to TCS. In some cases even higher sensitivities than in bacteria were observed, which is in accordance with published effect data (Harada et al., 2008; Orvos et al., 2002). Similarly to bacteria, high species sensitivity differences were observed for algae (Franz et al., 2008). In bacteria these sensitivity differences can be ascribed to several resistance mechanisms reported in Schweizer (2001). These findings lead to the question about the reasons for species sensitivity differences in algae. A mesocosm study was performed to detect effects of TCS across levels of biological organization and to investigate the impact of sensitivity differences on complex aquatic communities. For that purpose, structural and functional effects parameters were observed.

Um die Effekte von Umweltchemikalien auf Populationen von Fließgewässerorganismen zu untersuchen, sind an der TU Dresden Fließrinnen entwickelt worden. Die Komplexität wurde bewusst reduziert, um die beobachteten Effekte besser kausal analysieren zu können. Nach einer Erweiterung des Nahrungsnetzes um Grazer (Eintagsfliegen-Larven) und der weiteren Optimierung der Methode zur Bestimmung des Aufwuchses (Periphyton) wurden 2 Experimenten mit einem Pflanzenschutzmittel (Fenoxycarb) und einer Industriechemikalie (Bisphenol A) durchgeführt, um die Effekte dieser Chemikalien auf den Aufwuchs, die Eintagsfliegen-Larven Rhithrogena semicolorata und Seratella ignita, sowie Oligochaeten der Art Lumbriculus variegatus zu erfassen. Die Wirkung von Fenoxycarb in 4 Konzentrationen von 0,05 bis 50 µg L-1 wurde über eine Dauer von 101 Tagen untersucht. Auf die physiko-chemischen Parameter, den Aufwuchs und L. variegatus wurden keine Effekte festgestellt. Bei R. semicolorata wurden Effekte auf das Überleben und die Emergenz beobachtet. Für den Endpunkt "Anzahl der toten Larven in der Fließrinne" wurde eine LC50 von 3,3 µg L-1 bestimmt. Die akute Toxizität (48 h LC50) von Fenoxycarb für S. ignita ist größer als 5 mg L-1. Bei Larven von S. ignita wurden 72 Tage nach Applikation Effekte beobachtet werden, die dem Wirkmechanismus von Fenoxycarb entsprechen. In der höchsten Konzentration zeigten ca. 80 % der emergierten Tiere morphologische Abnormalitäten an 4 Segmenten des Abdomens. Die Exposition erfolgte möglicherweise durch an Aufwuchs bzw. Detritus gebundene Substanz oder deren Metabolite, da die Substanz 19 Tage nach Applikation im Wasser nicht mehr nachweisbar war. Im zweiten Experiment wurde Wirkung von Bisphenol A in 3 Konzentrationen von 5 bis 500 µg L-1 (effektiv 0,24 bis 24,1 µg L-1) über eine Dauer von 103 Tagen untersucht. Auf die physiko-chemischen Parameter wurde kein Einfluss festgestellt. Der Aufwuchs in der höchsten Konzentration erreichte nur die Hälfte des Biomasse-Maximums der Kontrolle. Die EC10 beträgt 1,8 und die EC50 21,7 µg L-1 (effektiv). Das Populationswachstum von Lumbriculus variegatus war in den beiden höchsten Konzentrationen im Vergleich zur Kontrolle um ca. 50 % reduziert. Die akute Toxizität (LC50 96 h) für L. variegatus beträgt 5,3 mg L-1. Für das Populationswachstum in den Fließrinnen wurde eine EC10 von 0,11 µg L-1 (effektiv) ermittelt, die um den Faktor 48184 unter der akuten Toxizität liegt. - Anlage: Rohdaten (0,53 MB)- Nutzung: Referat Informationsvermittlung der SLUB"

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-15T20:39:20Z No. of bitstreams: 1 monalisadeoliveiranascimento.pdf: 941297 bytes, checksum: 0ab9b6d24b97368a8b471da73b2ddc50 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-17T16:13:19Z (GMT) No. of bitstreams: 1 monalisadeoliveiranascimento.pdf: 941297 bytes, checksum: 0ab9b6d24b97368a8b471da73b2ddc50 (MD5) / Made available in DSpace on 2017-05-17T16:13:19Z (GMT). No. of bitstreams: 1 monalisadeoliveiranascimento.pdf: 941297 bytes, checksum: 0ab9b6d24b97368a8b471da73b2ddc50 (MD5) Previous issue date: 2012-09-05 / Estudos sobre saturação de espécies buscam conhecer o papel relativo de fatores locais e regionais sobre a estruturação das comunidades. No caso de comunidades zooplanctônicas, os resultados encontrados são bastante divergentes, tornando necessário o preenchimento de certas lacunas. Uma destas está na comparação entre diferentes tipos de ambiente, como perenes e temporários, que apresentam comunidades com características bem distintas. Lagoas temporárias passam periodicamente por eventos de seca e, considerando organismos aquáticos, este é um dos mais fortes distúrbios experimentados, pois impõe severas restrições fisiológicas e comportamentais. Baseado nestes fatos, este estudo tem como hipótese principal que lagoas temporárias apresentam comunidades zooplanctônicas insaturadas, enquanto lagoas perenes apresentam comunidades zooplanctônicas saturadas. Para testá-la, foi realizado um experimento em mesocosmos onde as comunidades zooplanctônicas destes dois tipos de lagoas foram manipuladas, bem como o evento de dispersão. Os resultados indicam que ambas apresentam-se saturadas e que, portanto, fatores locais são predominantemente mais importantes do que a dispersão (fator regional) sobre a estruturação destas comunidades. Dentre estes fatores locais, os fatores abióticos atuam como filtros selecionadores de espécies e parecem ser mais importantes do que as interações bióticas com as comunidades residentes. / Many studies about species saturation try to find out the relative role of the local and regional factors on the communities structure. Regarding to zooplankton communities, the results obtained are very divergent requiring the filling of certain gaps. One of these gaps is on the comparison between different types of environments, like perennial and temporary which have communities with very different features. Temporary ponds are periodically affected by drought events and, considering the aquatic organisms, this is one of the strongest disturbs that they experienced because it imposes physiological and behavioral restrictions. Based on these facts, the principal hypothesis of this study is that temporary ponds have unsaturated zooplankton communities while permanent ponds have saturated zooplankton communities. To test it, an experiment was made in mesocosms where the communities of both ponds were manipulated as well as the dispersion event. The results indicate that both communities are saturated and therefore local factors are predominantly more important than the dispersion (regional factor) on the structuring of these communities. Among these local factors, the abiotic factors act as species selectors filters and seems to be more relevant than the biotic interactions with the resident species.