Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2017-08-18T19:11:56Z No. of bitstreams: 1 Viviane Manozzo 2016.pdf: 3333567 bytes, checksum: ebe7b9726675839238cfd3ee3c4ed3ca (MD5) / Made available in DSpace on 2017-08-18T19:11:56Z (GMT). No. of bitstreams: 1 Viviane Manozzo 2016.pdf: 3333567 bytes, checksum: ebe7b9726675839238cfd3ee3c4ed3ca (MD5) Previous issue date: 2016-08-29 / The whole world is experiencing an energy crisis, though a lot of potential is wasted because it is necessary to develop technologies for the utilization of biomass as a raw material capable of producing energy. Municipal waste, wood waste, agricultural crop residues, plants and algae, breeding animal waste, food processing and organic waste are considered the main sources of production and biomass and boost research in the energy sector in search responses to the crises faced. The objective of this study was to obtain experimental data of thermal decomposition of biomass Pistia stratiotes and Eichhornia crassipes to determine the kinetic parameters through the pyrolysis process. Thus, laboratory studies were conducted in order to determine the chemical and physical properties: particle size, moisture, volatile matter, ash, cellulose, lignin and superior calorific value (PCS), to obtain the thermal decomposition curve by thermogravimetric analysis for biomasses studied ; and determine the kinetic parameters during pyrolysis of biomass decomposition methods using non-isothermal differential. The thermogravimetric analysis was performed under an inert nitrogen atmosphere at temperatures ranging from 60ºC to 990ºC for four heating rates of 5, 10, 15 and 20 °C / min. Results as 10.83 MJ / kg and 12, 96 MJ / kg were found for PCS of biomasses Pistia stratiotes and Eichhornia crassipes respectively. The determination of the kinetic parameters we used the methods: Flyn Wall Osawa, Kissinger and Friedman. The mass loss of biomass Pistia stratiots presented in the temperature range 244-823 ° C. The Eichhornia crassipes in the range 241-991°C. To Pistia stratiotes the activation energy calculated by the FWO method foinde 178.60 kJ / mol - 332.79 kJ / mol. Kissinger 155.89 kJ / mol. Friedman in the range of 153.75 kJ / mol - 369.09 kJ / mol. For Eichhornia crassipes the activation energy calculated by the method presented FWO in the range of 156.59 kJ / mol - 531 80 kJ / mol. Kissinger 130.46 kJ / mol. Friedman in the range of 156.53 kJ / mol - 349.47 kJ / mol. The results obtained were of the same order of magnitude. The kinetic data confirm that the molecular structures are represented by different mechanisms thermal decomposition reaction rate and the decomposition rate with the temperature in the pyrolysis showing that this technique is a powerful tool for transforming biomass into products which contribute to generation of energy. / O mundo todo vive uma crise energética, no entanto um grande potencial é desperdiçado, pois é preciso que se desenvolvam tecnologias para o aproveitamento de biomassas como matéria prima capaz de produzir energia. Os resíduos urbanos, restos de madeira, resíduos de culturas agrícolas, plantas e algas, resíduos de criadouros de animais, de processamento de alimentos e de resíduos orgânicos se apresentam como as principais fontes de produção e biomassa e impulsionam as pesquisas no setor energético em busca de respostas para as crises enfrentadas. Assim, o objetivo deste estudo foi obter dados experimentais de decomposição térmica das biomassas Pistia stratiotes e Eichhornia crassipes visando determinar os parâmetros cinéticos por meio do processo de pirólise. Desta forma, estudo laboratoriais foram desenvolvidos visando determinar as propriedades químicas e físicas: granulometria, umidade, material volátil, cinzas, celulose, lignina e poder calorífico superior (PCS), obter as curvas de decomposição térmica através de análises termogravimétricas para as biomassas em estudo; e determinar os parâmetros cinéticos durante a pirólise de decomposição das biomassas utilizando métodos não isotérmicos diferenciais. A termogravimetria foi realizada em atmosfera inerte de nitrogênio, com temperaturas variando de 60ºC a 990ºC, para quatro taxas de aquecimento: 5, 10, 15 e 20ºC / min. Resultados como 10,83 MJ/kg e 12, 96 MJ/kg foram encontradas para o PCS das biomassas Pistia stratiotes e Eichhornia crassipes respectivamente. A determinação dos parâmetros cinéticos utilizou–se dos métodos: Flyn Wall Osawa, Kissinger e o Friedman. A perda de massa da biomassa Pistia stratiotes apresentou na faixa de temperatura de 244 – 823 °C. A Eichhornia crassipes na faixa de 241 – 991 °C. Para Pistia stratiotes a energia de ativação calculada pelo método FWO foi de 178,60 kJ / mol – 332,79 kJ / mol. Por Kissinger 155,89 kJ / mol. Por Friedman na faixa de 153,75 KJ / mol – 369,09 kJ / mol. Para Eichhornia crassipes a energia de ativação calculada pelo método FWO apresentou na faixa de 156,59 kJ / mol – 531, 80 kJ / mol. Por Kissinger 130,46 kJ / mol. Por Friedman na faixa de 156,53 kJ / mol – 349,47 kJ / mol. Os resultados obtidos foram da mesma ordem de grandeza. Os dados cinéticos obtidos confirmam que as estruturas moleculares são representadas por diferentes mecanismos de decomposição térmica, taxas de reação e taxa de decomposição com a temperatura no processo de pirólise comprovando que a técnica é uma poderosa ferramenta para transformar biomassas em produtos que contribuem para geração de energia.

A presença de macrófitas em reservatórios possui tanto aspectos positivos como negativos para os ecossistemas aquáticos tornando-se, assim, essencial o estudo dessa comunidade para o adequado manejo dos recursos hídricos. O principal objetivo do presente estudo foi verificar a variação sazonal das características limnológicas do reservatório Itupararanga-SP e relacioná-las com a variação da biomassa de macrófitas e com a taxa de decomposição dessas plantas. Sendo assim, selecionaram-se quatro braços no reservatório, com presença relevante de macrófitas. Amostras de água e sedimento foram coletadas sazonalmente e analisadas. Nos mesmos períodos as plantas foram amostradas e a biomassa determinada. Avaliou-se ainda, a decomposição in situ e em laboratório de duas espécies (Polygonum lapathifolium e Eichhornia azurea) com o intuito de comparar as taxas de decomposição sob condições naturais e controladas. Empregou-se um modelo cinético para obtenção dos coeficientes de decaimento de massa. Os resultados obtidos foram analisados estatisticamente através do teste ANOVA e Análise de Correspondência Canônica (CCA). As análises limnológicas revelaram a formação de um gradiente espaço-temporal no reservatório que provavelmente influenciou a distribuição e o desenvolvimento da biomassa nas diferentes estações de amostragem. Verificou-se que Eichhornia crassipes e Pistia stratiotes foram influenciadas pela concentração de nutrientes. A CCA evidenciou a relação entre Polygonum lapathifolium, pH, oxigênio dissolvido, matéria orgânica e nutrientes no sedimento, enquanto Eichhornia azurea e Myriophyllum aquaticum foram influenciados, de forma diferente, por compostos inorgânicos. O processo de decomposição foi mais rápido em condições naturais, tanto para E. azurea como para P. lapathifolium, com maior mineralização da matéria orgânica particulada e refratária. Sob condições controladas, o decaimento da matéria orgânica dissolvida foi mais lento em temperaturas mais baixas e o coeficiente Q10 indicou que o incremento da temperatura interferiu no decaimento de massa. Esse fato ficou mais evidente nos resultados obtidos para E. azurea. A decomposição revelou elevada quantidade de matéria orgânica refratária em ambas as espécies, as quais contribuem ao aporte de carbono com, aproximadamente 200g de carbono de refratário. / The occurrence of aquatic macrophytes in reservoirs plays positive and negative effects to aquatic ecosystems, therefore the study of macrophyte community is essential to the aquatic resources management. This study aimed to evaluate the seasonal variation of limnological conditions of Itupararanga Reservoir, Sao Paulo State, to associate them with macrophyte biomass and with the decomposition rates of the plants. So four arms in the reservoir, where the presence of macrophytes was relevant, were selected to perform this study. Water and sediment along with macrophytes were sampled in different seasons and analyzed. Decomposition experiments of two macrophyte species (Polygonum lapathifolium and Eichhornia azurea) were carried out in situ and in laboratory conditions in order to compare the decomposition rates in different conditions. A kinetic model was adopted to explain the organic matter decay. The results were statistically analyzed with ANOVA and Canonical Correspondence Analyses (CCA). The limnological results showed a spatial and temporal variation which probably influenced the distribution and development of macrophyte biomass. The nutrient concentration influenced Eichhornia crassipes and Pistia stratiotes. Moreover the CCA showed a relationship among Polygonum lapathifolium, pH, dissolved oxygen, sediment organic matter and sediment nutrients, while Eichhornia azurea and Myriophyllum aquaticum were associated in different way with inorganic compounds. The decomposition process was faster in natural conditions with high mineralization coefficient for both E. azurea and P. lapathifolium. Under laboratory conditions the dissolved organic matter decay was slower for low temperatures and Q10 coefficient showed the temperature interference in the mass breakdown mainly for E. azurea assay. Both species have high refractory contents, which contributes, approximately, with 200g of refractory carbon.

Orientador: Lúcia Helena Sipaúba-Tavares / Banca: Silvano Bianco / Banca: Rodrigo Ney Millan / Resumo: O estudo do cultivo de microalgas na aquicultura é importante para incrementar o conhecimento da biologia das espécies, favorecendo posterior produção em ambientes controlados. O objetivo deste trabalho foi avaliar o crescimento da microalga Ankistrodesmus gracilis em meio de cultura composto por biomassa de Azolla caroliniana e Lemna minor e utilizar a microalga na alimentação do Xiphophorus maculatus visando melhorar o desempenho zootécnico. O experimento com a microalga durou 28 dias em condições controladas e os parâmetros físicos e químicos foram mensurados semanalmente com a avaliação diária do crescimento. A planta L. minor apresentou melhores resultados para macro e micronutrientes, e o crescimento também foi maior no meio de cultura para a microalga A. gracilis (552 x 105 cel mL-1) do que no meio de A. caroliniana (292 x 105 cel mL-1). No meio de cultura de L. minor a microalga A. gracilis apresentou maiores teores de clorofila-a, taxa de crescimento, densidade celular média e máxima e fósforo total. O teor de lipídio foi maior no meio de L. minor e o de proteína foi igual em ambos os meios. O uso de microalga A. gracilis crescida no meio de macrófita, foi utilizada para a alimentação do peixe ornamental Platy (X. maculatus). Para preparação da ração a microalga crescida nos dois meios de cultura diferentes foi liofilizada e adicionada na ração na proporção de 10%. Os tratamentos foram alimento inerte, somente ração (controle); alimento inerte com microalga A. gracil... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Studies on the cultivation of microalgae are greatly relevant for in-depth analysis of species' biology and for highlighting production in controlled environments. Current analysis assesses growth of the Ankistrodesmus gracilis microalgae in a culture medium composed of Azolla caroliniana and Lemna minor biomass and to use a microalga in the feeding of Xiphophorus maculatus aiming to improve the zootechnical performance. Assay with microalga lasted 28 days in controlled conditions, and physical and chemical parameters were measured weekly, coupled to daily growth evaluation. Macrophyte L. minor had better results macro and micronutrients. and growth was also higher in the culture medium for microalgae A. gracilis (552 x 105 cell mL-1 ) than in A. caroliniana medium (292 x 105 cell mL-1 ). Microalga A. gracilis had higher rates of chlorophyll-, growth and medium, maximum cell density rates and total phosphorus in this culture medium. Lipid rates were greater in L. minor medium. Protein rate was equal in the two media. The use of microalga A. gracilis grown in macrophyte medium was employed for the feeding of the ornamental fish Platy (X. maculatus). To prepare the feed the microalgae grown in the two different culture media were lyophilized and added to the ration in the ratio at 10%. Treatments consisted of inert feed, ration only (control); inert feed plus microalga A. gracilis cultivated in A. caroliniana medium; inert feed plus microalga A. gracilis cultivated in L. minor... (Complete abstract click electronic access below) / Mestre

Twentieth century human settlement within the Tampa Bay watershed was linked to a dramatic mid-century decline in bay water quality and loss of seagrass acreage. Decades of direct and indirect nutrient discharges to the bay from phosphorus mining, fertilizer manufacturing, and wastewater treatment, as examples, impaired the estuary. In the past twenty years, regional stakeholders have worked to improve the bay water quality by reducing point and non-point source nutrient loading to the bay. Lakes within the Tampa Bay watershed may play an important role in attenuating the flow of nutrients into the bay. This study hypothesized that between 1990 and 2007 lake water concentrations of total phosphorus (TP) and chlorophyll-a, as well as the ratio of total nitrogen to total phosphorus (TN:TP), have changed for selected lakes in the Tampa Bay watershed. During this period, the watershed underwent a rapid shift in land use as groves and farms became shopping malls and new homes. A two-way analysis of variance (ANOVA) revealed that for 10 lakes clustered in the northern portion of the Tampa Bay watershed and classified as oligotrophic or mesotrophic, observed increases in water concentrations of TP and chlorophyll-a were statistically significant. For 6 lakes classified as hypereutrophic and scattered across the watershed, observed decreases in water TP concentrations were statistically significant, while chlorophyll-a concentrations did not change. For both groups of lakes, the TN:TP ratio declined significantly; however, oligotrophic and mesotrophic lakes were phosphorus-limited but hypereutrophic lakes were nitrogen-limited, based on this ratio. A second hypothesis of this study was that lake water concentrations of TP, total nitrogen (TN) and chlorophyll-a were lower in lakes that had more coverage of submerged aquatic vegetation, as vegetation suppresses re-suspension of sediments and is a reservoir for nitrogen and phosphorus and a surface for biofilms. The results of a one-way ANOVA showed that for 34 lakes within the Tampa Bay watershed, lakes with a greater than 20 percent volume infested by macrophytes (PVI), water concentrations of TP and chlorophyll-a but not TN were statistically lower than for lakes with a less than 20 PVI.

Lake Waikare is a large, shallow eutrophic lake devoid of submerged macrophytes. I investigated potential methods for re-establishing submerged macrophytes in the lake. Specifically, I subjected charophyte (Chara corallina) plantlets to two treatments of exposure in the lake (in areas exposed and sheltered from wind) to test for survival and growth under these conditions, and inside and outside fish exclosures to test for growth and survival in the presence of fish. While plantlets grew outside the exclosures in winter, their accumulated biomass over 21 days was less than protected plantlets. In winter, the accumulated biomass was lower outside than inside exclosures (by ~40%) at the sheltered site and was lower outside than inside exclosures (by 43%) at the exposed site. Overall, growth rates in winter were higher at the sheltered site (compared to the exposed site) by ~7%. In summer, charophyte accumulated biomass inside the exclosures increased by 85%, while at the sheltered site accumulated biomass increased by 58%. Outside the exclosures in summer the plantlets were completely removed at both sites. Overall, growth rates where higher at the exposed site than the sheltered site by 31%. Fish were responsible for the partial removal of plantlets in winter and total removal of plantlets in summer, and therefore affect the survival and growth of charophytes in Lake Waikare. The embayment at the sheltered site provides the best location in winter for re-establishment of charophytes from oospores because better growth rates were obtained there, and its sheltered location provides protection from severe wave action found at the exposed site. Oospores did not germinate after being submersed in the lake for 90 days due to heavy sedimentation. To induce an improvement in the present light climate, Alum was tested to determine its effectiveness and longevity for settling lake sediments to allow charophytes to establish and grow. Examining the settling rates of Lake Waikare sediments and water treated with Alum over a range of suspended sediment concentrations and time intervals, sediments settled faster with Alum than without for at least 15 days (at 200 g l^1 suspended sediment concentration) and it remained active to 60 days but at reduced effectiveness. At the other concentrations tested (100 g l^1 and 300 g l^1 suspended sediment concentration), Alum responses were insignificant. An improved light climate achieved by fish removal or Alum treatment will likely not be sufficient to permit the re-establishment of submerged macrophytes due to the turbid, algal-dominated state of the lake. The present nutrient and sediment levels, wave climate and fish influence must be mitigated so charophyte plantlets can be established.

La production animale augmente continuellement à l'échelle mondiale depuis quelques décennies, dans les pays développés d'abord et maintenant dans les pays en développement. Des systèmes industriels ont donc été développés pour améliorer la productivité des élevages, pour augmenter rapidement la production animale et pour fournir la nourriture consommée par les villes. Ils sont efficaces en termes de biosécurité et d'efficacité de conversion des aliments du bétail mais ils ont des incidences sur l'environnement telles que les émissions d'odeur, les émissions d'ammoniac ou de gaz à effet de serre, ou la pollution de l'eau. La durabilité de ces systèmes dépend de leur capacité à limiter leurs impacts sur la raréfaction des ressources naturelles et à limiter leurs fuites de sorte que l'environnement naturel et la biodiversité puissent être préservés près des élevages. Des systèmes de traitement onéreux ne pouvant pas être employés pour des raisons économiques, l'ingénierie écologique fournit les concepts qui peuvent aider à trouver des solutions plus efficientes économiquement et écologiquement. Notre travail a commencé avec la mise en route d'un système associant un bâtiment d'élevage de porcs, une séparation de phase liquide/solide de l'effluent du bâtiment, un lombrifiltre et un ensemble de zones humides artificielles. Destiné à augmenter l'efficacité de recyclage de l'eau et à produire des biomasses utilisables pour la nutrition animale, la fertilisation, la production d'énergie, etc., ce système combine donc la dilution élevée des effluents, permettant la diminution des émissions, à la réutilisation de l'eau et des nutriments. L'eau utilisée pour l'évacuation fréquente des déjections est ainsi recyclée. Les nutriments sont réutilisés sur l'exploitation agricole ou exportés. L'emprise au sol du système est environ 50 fois inférieure à celle requise pour l'épandage des effluents. L'objectif fondamental de la thèse était d'améliorer la compréhension du système pour en préciser les avantages et les limites. L'objectif finalisé était d'étudier si les connaissances produites permettaient d'améliorer la conception et la gestion du système. Des méthodes spécifiques ont été développées pour étudier, sous l'angle des processus et sous l'angle systémique, un dispositif dont les dimensions ne permettaient pas une reproduction dans un laboratoire. Elles ont été appliquées aux émissions gazeuses du lombrifiltre et à l'efficacité de traitement des zones humides artificielles. Nos résultats permettent de définir une " quantité optimale " d'effluent qui maximise la population de vers de terre (preferendum). Au-dessus de ce seuil, les vers de terre meurent en raison de conditions anoxiques. Quand la population de vers de terre est maximale, les émissions d'ammoniac et de gaz à effet de serre sont limitées en regard du flux d'intrant. Par conséquent, l'abondance de vers de terre peut être employée comme bioindicateur de faibles émissions dans les systèmes de transformation d'effluent. L'effet des lombriciens sur les émissions gazeuses est surtout indirect, par leur influence sur la structure de la couche organique, sa porosité, les transferts de matière et sa population microbienne. La " quantité optimale " transférée entre deux niveaux successifs peut être définie pour la production de végétation des zones humides artificielles. Par rapport à un système ouvert, le recyclage de l'eau induit un changement de la stoechiométrie des nutriments, en raison d'efficacités de traitement différentes de ces nutriments : par exemple, le taux de réduction du potassium est inférieur à celui de l'azote ; cette différence induit une augmentation de concentration en potassium dans l'eau par rapport à l'azote. La concentration en potassium se stabilise lorsque la rétention par tous les compartiments correspond à une diminution de masse équivalente au flux de potassium excrété par les animaux. Cela montre que la stoechiométrie des nutriments devrait changer dans les milieux agricoles et probablement dans les productions où l'efficacité du recyclage est augmentée. L'estimation du bilan de matière du système, montre que les émissions d'ammoniac et de gaz à effet de serre sont réduites par rapport aux flux d'azote, et que les produits organiques (lombricomposts et boues des lagunes) contribuent majoritairement à l'abattement des nutriments. Des recommandations pour la conception et la gestion des systèmes qui améliorent le recyclage des effluents sont proposées à partir de ces connaissances. Nos résultats ont été et pourront être mobilisés pour des buts socio-économiques.

The Tibetan Plateau is the largest elevated landmass in the world and profoundly influences atmospheric circulation patterns such as the Asian monsoon system. Therefore this area has been increasingly in focus of palaeoenvironmental studies. This thesis evaluates the applicability of organic biomarkers for palaeolimnological purposes on the Tibetan Plateau with a focus on aquatic macrophyte-derived biomarkers. Submerged aquatic macrophytes have to be considered to significantly influence the sediment organic matter due to their high abundance in many Tibetan lakes. They can show highly 13C-enriched biomass because of their carbon metabolism and it is therefore crucial for the interpretation of δ13C values in sediment cores to understand to which extent aquatic macrophytes contribute to the isotopic signal of the sediments in Tibetan lakes and in which way variations can be explained in a palaeolimnological context. Additionally, the high abundance of macrophytes makes them interesting as potential recorders of lake water δD. Hydrogen isotope analysis of biomarkers is a rapidly evolving field to reconstruct past hydrological conditions and therefore of special relevance on the Tibetan Plateau due to the direct linkage between variations of monsoon intensity and changes in regional precipitation / evaporation balances. A set of surface sediment and aquatic macrophyte samples from the central and eastern Tibetan Plateau was analysed for composition as well as carbon and hydrogen isotopes of n-alkanes. It was shown how variable δ13C values of bulk organic matter and leaf lipids can be in submerged macrophytes even of a single species and how strongly these parameters are affected by them in corresponding sediments. The estimated contribution of the macrophytes by means of a binary isotopic model was calculated to be up to 60% (mean: 40%) to total organic carbon and up to 100% (mean: 66%) to mid-chain n-alkanes. Hydrogen isotopes of n-alkanes turned out to record δD of meteoric water of the summer precipitation. The apparent enrichment factor between water and n-alkanes was in range of previously reported ones (≈-130‰) at the most humid sites, but smaller (average: -86‰) at sites with a negative moisture budget. This indicates an influence of evaporation and evapotranspiration on δD of source water for aquatic and terrestrial plants. The offset between δD of mid- and long-chain n-alkanes was close to zero in most of the samples, suggesting that lake water as well as soil and leaf water are affected to a similar extent by those effects. To apply biomarkers in a palaeolimnological context, the aliphatic biomarker fraction of a sediment core from Lake Koucha (34.0° N; 97.2° E; eastern Tibetan Plateau) was analysed for concentrations, δ13C and δD values of compounds. Before ca. 8 cal ka BP, the lake was dominated by aquatic macrophyte-derived mid-chain n-alkanes, while after 6 cal ka BP high concentrations of a C20 highly branched isoprenoid compound indicate a predominance of phytoplankton. Those two principally different states of the lake were linked by a transition period with high abundances of microbial biomarkers. δ13C values were relatively constant for long-chain n-alkanes, while mid-chain n-alkanes showed variations between -23.5 to -12.6‰. Highest values were observed for the assumed period of maximum macrophyte growth during the late glacial and for the phytoplankton maximum during the middle and late Holocene. Therefore, the enriched values were interpreted to be caused by carbon limitation which in turn was induced by high macrophyte and primary productivity, respectively. Hydrogen isotope signatures of mid-chain n-alkanes have been shown to be able to track a previously deduced episode of reduced moisture availability between ca. 10 and 7 cal ka BP, indicated by a 20‰ shift towards higher δD values. Indications for cooler episodes at 6.0, 3.1 and 1.8 cal ka BP were gained from drops of biomarker concentrations, especially microbial-derived hopanoids, and from coincidental shifts towards lower δ13C values. Those episodes correspond well with cool events reported from other locations on the Tibetan Plateau as well as in the Northern Hemisphere. To conclude, the study of recent sediments and plants improved the understanding of factors affecting the composition and isotopic signatures of aliphatic biomarkers in sediments. Concentrations and isotopic signatures of the biomarkers in Lake Koucha could be interpreted in a palaeolimnological context and contribute to the knowledge about the history of the lake. Aquatic macrophyte-derived mid-chain n-alkanes were especially useful, due to their high abundance in many Tibetan Lakes and their ability to record major changes of lake productivity and palaeo-hydrological conditions. Therefore, they have the potential to contribute to a fuller understanding of past climate variability in this key region for atmospheric circulation systems. / Das tibetische Hochplateau ist die größte gehobene Landmasse der Erde und beeinflusst maßgeblich atmosphärische Zirkulationsmuster wie den Asiatischen Monsun. Um die Auswirkungen zukünftiger Schwankungen der Monsundynamik auf das regionale Klima besser einschätzen zu können, ist es wichtig, ein fundiertes Verständnis vergangener Klimaänderungen zu entwickeln. Daher ist das Tibetplateau in den letzten Jahren mehr und mehr in den Fokus paläoklimatischer Studien gerückt. Die große Anzahl an Seen in der Region bietet ein unerschöpfliches Klimaarchiv und viele Studien haben sich bereits mit Seesedimenten zur Klimarekonstruktion befasst. Dabei wurde in erster Linie auf biologische, sedimentologische und geochemische Parameter zurückgegriffen, wohingegen organische Biomarker bisher recht selten benutzt wurden. Die vorliegende Arbeit untersucht die Anwendbarkeit dieser potentiellen Klimaindikatoren auf dem Tibetplateau. Hierbei wurde ein Schwerpunkt auf die Analyse kutikularer Blattwachse von Wasserpflanzen gelegt, da diese wegen ihres starken Auftretens in tibetischen Seen einen erheblichen Beitrag zur organischen Substanz im Sediment leisten. Um den Einfluss von Wasserpflanzen auf das Sediment über einen weiten klimatischen Gradienten zu untersuchen, wurden Oberflächensedimente und Wasserpflanzen vom zentralen und östlichen Tibetplateau auf ihre Biomarkerzusammensetzung sowie auf ihre Kohlen- und Wasserstoffisotopensignatur untersucht. Dadurch wurde das Verständnis über beeinflussende Faktoren auf diese Parameter in Sedimenten vertieft. In einem Sedimentbohrkern des Koucha-Sees (östliches Tibetplateau) konnten diese Parameter dann im Hinblick auf Änderungen der Produktivität im See sowie der hydrologischen und klimatischen Bedingungen der letzten 15000 Jahre interpretiert werden. Es zeigte sich, dass der See bis 8000 Jahre vor Heute stark mit Wasserpflanzen bewachsen war, während die letzten 6000 Jahre Algen dominierten. Mit Hilfe von Wasserstoffisotopen wurden eine Zunahme des Monsuns und steigende Niederschläge zwischen 15000 und 10000 Jahren vor Heute sowie eine relativ trockene Periode zwischen 10000 und 7000 Jahren vor Heute rekonstruiert. Durch Kombination von Biomarkerkonzentrationen sowie deren Kohlenstoffisotopensignal wurden außerdem kurzzeitige Kälteperioden um ca. 6000, 3100 und 1800 Jahren vor Heute nachgewiesen, die vorher bereits in anderen Klimaarchiven in Tibet sowie auf der nördlichen Hemisphäre belegt wurden. Mit Hilfe von organischen Biomarkern konnte so ein detailliertes Bild über die Entwicklung des Koucha-Sees seit dem letzten Glazial gewonnen werden. Organische Biomarker haben sich somit als geeignet erwiesen, einen Beitrag zur Klimarekonstruktion auf dem Tibetplateau zu leisten.

Bacteria, nanoflagellates and ciliates constitute the microbial loop and it is a model of the pathways of carbon and nutrient cycling through microbial components of pelagic aquatic communities. The current study comprised of a comparative study of the microbial food web community along north to south latitudinal gradient using space for time susbtitute, monitoring and mesocosms experiments with contrasting nutrient and predation states. We investigated effect of fish predation through different zooplankton taxa on microbial loop community with in situ food web experiments in 14 lakes along north to south latitudinal gradient. The effect of seasonality was also determined by monitoring in Lakes Eymir and Mogan between 2010 and 2011. Effects of hydrology and fish through microbial community was studied in mesocosms in Lake Eymir. An implication of global warming along with eutrophication on microbial community was further explored in warmed and nutrient enriched artificial ponds during 4 months in Silkeborg, Denmark. Our results revealed that temperature, hydrology, fish, macrophytes and seasonality affected the top down control of zooplankton and bottom up control of nutrients on microbial loop and interactions between controls and increase in these controls had a strong negative impact on the contribution and biomass of microbial loop and change the interactions within microbial community. Global warming may also effect the impact of top down and bottom up controls through increasing eutrophication, temperature, change in hydrology and zooplankton composition and in a consequence of that efficiency of microbial loop may decrease in the future warmer, drier and eutrophic conditions.

Decreasing the nitrogen transport from land to surrounding seas is a major task throughout the world to limit eutrophication of the coastal areas. Several approaches are currently used, including the establishment of wetlands, to decrease the transport of nitrogen. Wetlands represent ecosystems where the nitrogen removal from water can be efficient given that they are appropriately designed. The aim of this thesis was to investigate and quantify the effect of critical factors that regulate the nitrogen removal in wetlands, and to develop better guidelines for wetland design. Studies were performed at different scales, from microcosms to full scale wetlands, and methods included modelling, mass balance calculations and process studies. A first order rate model was used to simulate the nitrogen transformations in two large wetlands treating wastewater containing both ammonium and nitrate nitrogen. It was found that the dynamics of the main itrogen transformation processes could not be satisfactorily described using this approach. Large wetlands containing vegetation are complex ecosystems, and the process rates vary in both time and space. The great diversity of microenvironments favours different nitrogen processes, and large differences in potential nitrification and denitrification rates were found between different surface structures within a wetland. The results from microcosms measurements showed that the highest potential for nitrification was on surfaces in the water column, while the denitrification capacity was highest in the sediment. For the sediment denitrification capacity, the plant community composition was shown to be of major importance primarily by supplying litter serving as a carbon and energy source, and/or attachment surfaces, for denitrifying bacteria. Denitrification rates may be affected more than three fold by different types of litter and detritus in the sediments. Intact sediment cores from stands of the emergent plants Glyceria maxima and Typha latifolia had higher denitrification potential than sediment cores from stands of the submersed plant Potamogeton pectinatus. However, the quality of the organic material for the denitrifying bacteria was highest in G. maxima and P. pectinatus stands. All sediment cores from the wetland were limited by carbon, and the lower denitrification capacity of the submersed plant, P. pectinatus, was likely due to lower amounts of organic matter. However, in another wetland, intact cores from stands of the submersed plant Elodea canadensis had a higher denitrification capacity than the cores from stands of T. latifolia and Phragmites australis. This was possibly due to a larger biomass, and better quality, of the organic matter from that submersed specie, or to epiphytic biofilms on the living plants. Those microcosms studies showed that both the quality of the organic matter as a substrate for the microbial communities, and the amount of organic material produced were important for the denitrification capacity. In pilot scale wetlands, the composition of the plant community was also a more important factor for high nitrate removal than the differences in hydraulic loads (equivalent of 1 or 3 d retention time), despite the cold climate. The greatest removal was found in wetlands with emergent vegetation dominated by P. australis and G. maxima, rather than in wetlands with submersed vegetation. In brief, the results presented in this thesis emphasize the importance of dense emergent vegetation for high annual nitrate removal in treatment wetlands.

Shallow lake wetlands, for which aquatic plants (macrophytes) and water clarity are the key indicators of ecological status, provide valuable services to wildlife and humanity. Conservation of these ecosystems requires development of rapid and large scale monitoring strategies, where remote sensing and Geographic Information Systems (GIS) can be advantageous. In this study, high spatial resolution Quickbird and IKONOS and medium spatial resolution Landsat and Aster images were used for monitoring the aquatic plants and water clarity in Lakes Mogan and Eymir. Classification of emergent plants with high spatial resolution data yielded overall accuracies greater than 90% for both lakes, while overall accuracies obtained from the medium spatial resolution data ranged between 80% and 93% for Lake Mogan and between 70% and 78% for Lake Eymir. It was found that there was 23ha reed bed loss in Lake Mogan between 2002 and 2005 and an additional 14ha was lost between 2005 and 2006. In Lake Eymir, no significant change in reed bed area was detected from high spatial resolution images / however medium spatial resolution images revealed 8ha of change which was attributed to the presence of mixed pixels due to low resolution. The overall accuracies for submerged plant coverage classification from Quickbird images in Lake Mogan were 83% (2005) and 79% (2006) and for classification of submerged plants species were 72% (2005) and 69% (2006). Moreover, it was found that blue band together with the ratio of red band to blue band, were the best predictors of Secchi disc depth.