<p>This dissertation presents the first findings of aerosol indirect effect in the foothills of the Himalayas (Central Nepal), through a systematic research approach involving satellite data analysis, field campaign, growth factor estimation and numerical modeling studies. Satellite retrieved aerosol optical depth data over the region were first used to identify the dominant modes of spatial/temporal variability of aerosols in the region. Based on the observed dominant spatial mode of aerosol in the pre-monsoon season (Shrestha and Barros 2010, ACP), a field campaign was organized under the Joint Aerosol Monsoon Experiment (JAMEX09) at Dhulikhel and Besisahar to simultaneously measure dry and ambient aerosols size spectra using SMPS and chemical composition using filters (Shrestha et al. 2010, ACP). The diurnal cycle of aerosol number concentration exhibited a consistent peak in the morning and evening period, which was found to be associated with increase in local emission and the delay in ventilation of aerosol through upslope flows and mixing (inferred from an idealized numerical study over Besisahar). The aerosol size distribution was mostly unimodal at night and bimodal during the day, with a consistent larger mode around 100nm and a smaller mode located around 20nm. The chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64~68%) of the aerosol concentration followed by ionic species (24~26%, mainly and ). Elemental Carbon (EC) compromised 7~10% of the total composition and 27% of OC was found to be water soluble at both sites. The aerosol number concentration increased and decreased in the presence of synoptic scale aerosol plumes and after rainfall events respectively.</p><p>A simple model based on Köhler theory was used to explain the observed growth factor using an assumption of (NH4)2SO4 aqueous solution including the presence of slightly soluble organic compounds (SSC) with an insoluble core as a function of molality and mass-fraction. The measured growth factors suggest that the aerosols are in metastable state due to the strong diurnal cycle of relative humidity (RH). The bulk hygroscopic parameter estimated from the DGF and chemical composition of aerosols suggests less hygroscopic aerosols at both locations as compared to previous studies. The dry aerosol size distribution and the bulk hygroscopic parameters were used to estimate the cloud condensation nuclei (CCN) spectrum, which was vertically scaled up to lifting condensation level (LCL) assuming that the shape and chemical properties of aerosol remains unchanged (Shrestha et al. 2011, submitted to JGR). Finally, these regional CCN spectra for polluted and clean conditions as well as standard continental and marine spectra used in numerical weather prediction models (Cohard et al. 1998) were used to probe CCN sensitivity for a pre-monsoon storm system in Central Nepal during JAMEX09. A significant shift in the maxima of the accumulated precipitation was observed between the continental aerosol spectra (Cohard et al. 1998) and the polluted spectra for Dhulikhel. This shift caused the displacement of rainfall maximum away from the Kulekhani water reserve catchment, which is key to hydropower in Nepal. Detailed analysis of the simulations suggests that simgnificant differences in the space-time variability and intensity of precipitation, if not areally integrated amounts, can be explained by differences in the timing and intensity of latent heat release and absorption due to freezing/melting of hydrometers and evaporative cooling of droplets, strengthening cold pool formation and associated circulations. This numerical study provides the first look on the aerosol indirect effect over Nepal for a single pre-monsoon rainfall event, and how aerosols can potentially affect the precipitation distribution (to be submitted to JGR). In addition, it shows the importance of using regionally consistent CCN spectra in model parameterizations of aerosol-cloud interactions. At local places, the differences in simulated precipitation between marine, JAMEX09 clean and polluted air spectra were smaller (up tp ± 50%) than the difference between those simulations and the standard continental aerosol spectra (±200%).</p> / Dissertation

Permafrost thaw slumping along lakeshores in lakes of the Mackenzie Delta Uplands, NT is known to alter water chemistry significantly. Its impact on benthic communities and persistent organic pollutant (POP) behaviour in lakes is not known. Benthic invertebrate communities responded to slumps through changes to community composition and size spectra. Larger taxa tended to dominate in lakes with slumps. Variability in biomass size spectra was related to total dissolved nitrogen concentration and slump size. Concentrations of POPs in Gammarus were negatively correlated with total phosphorus and positively correlated with the percentage of the catchment slumped. Lakes with slumps generally had higher mean concentrations of POPs in Gammarus (ex. ΣPCBsDisturbed = 27.54 ng/g lipid, ΣPCBsUndisturbed = 16.97 ng/g lipid; ΣDDT Disturbed =18.47 ng/g lipid and ΣDDTUndisturbed =10.86 ng/g lipid). Benthic invertebrate biomass was also negatively correlated with concentrations of contaminants in Gammarus, supporting the biomass dilution hypothesis. Thaw slumps have large enough impacts on the physico-chemical characteristics of lakes that they alter benthic invertebrate community composition and size-structure, and contaminant concentrations in Gammarus.

Um dos principais problemas relacionados aos estudos limnológicos realizados manualmente em laboratório consiste no grande esforço, tempo de análise e trabalho especializado necessário. Esses fatores limitam a quantidade de amostras possíveis de serem analisadas em um determinado estudo, já que recursos sejam eles reagentes, recursos financeiros ou tempo são limitados. No presente trabalho foi utilizado um sistema semi-automatizado de medidas de variáveis físicas e químicas da água. O sistema é composto por uma sonda multi-parâmetro (Horiba U-22) e um sistema de posicionamento global (GPS) acoplados a um micro-computador, que realizam medidas georeferenciadas em curtos intervalos de tempo, permitindo um rastreamento horizontal das características da água. Foi ainda desenvolvido um sistema semi-automático para coleta fracionada da comunidade planctônica por meio de bomba de sucção operada por bateria e filtro coletor com rede de plâncton de diferentes aberturas de malha. O material coletado foi fotografado por meio de sistema de aquisição digital de imagens (microscópio Zeiss equipado com câmera AxionCan). Neste trabalho foi produzido um software (Planktonscan) que a partir da análise das imagens capturadas permite produzir dados com estimativas das medidas e dimensões dos organismos, calcular biovolumes e, utilizando fatores de conversão, estimar os valores de biomassa. O software apresenta uma interface para identificação, calcula a densidade dos organismos e produz relatório gráfico com informações sobre os organismos individuais e sobre a comunidade. Os equipamentos e o software foram testados em análises limnológicas e amostragem de plâncton no reservatório do Monjolinho, São Carlos, SP, em dezembro de 2005. Os resultados obtidos foram comparados com os disponíveis na literatura e demonstraram a aplicabilidade do sistema. / A major problem associated with the study of planktonic communities lies on the difficulties of analyzing the collected material, a long time-consuming procedure. Biomass determination is also a step requiring great effort and is subjected to large errors. In the present work a semi-automated system for measuring physical and chemical variables in the water was developed. The system is made up by a flow-pump, a multi-parameter probe and a global positioning system coupled to a microcomputer that performs measurements at short time intervals, allowing a horizontal tracking of the water quality, in much shorter times than traditional methods. Another semi-automated device was developed for collecting separate plankton size fractions. It uses a battery operating suction-pump coupled to a filter with different mesh nets. The collected materials are then submitted to image computer acquisition (Axion Vision Zeiss System). Additionally, in this study a software was produced (Planktonscan), that taking the measures of individuals dimensions (length, width and height) calculates biovolume and using conversion factors calculate the biomass for each zooplankton organism identified in the sample. Both systems were tested, regarding the measurement of limnological variables and plankton sampling, in the Monjolinho Reservoir, SP. The performance was good, resulting in a larger number of points sampled (60) in a shorter sampling time (1 hour) than those usually required. The biomass results provided by Planktonscan software were compared to data from literature, obtained by the traditional gravimetric method for dry weight determination and also with data generated from the use of mathematical models (length dry-weight regressions) available. The results were expressed as species population densities, biomasses and size spectra, evidencing the applicability of the models here developed.

As land use transformations are the main driver of biological diversity loss at the global scale, it is essential to provide predictions and understanding of their impacts in order to improve the mitigation of ecosystem perturbations. The first objective of this project was to describe the response of biological assemblages along a gradient of urbanization and to compare metrics of watershed imperviousness in order to determine, as has been suggested in the literature, whether effective imperviousness, which represents the proportion of impervious area directly connected to the stream by storm sewers, is a better predictor of stream impairement than total imperviousness in the watershed. Decline in sensitive taxa abundance is initiated at 14% total imperviousness and 3% effective imperviousness in the Ottawa-Carleton region and, total and effective imperviousness have equivalent predictive power. The second objective of this project was to describe how the structure of metazoan assemblages in urban streams, as described by size spectra attributes (i.e. slopes, intercepts, number of logarithmic size classes occupied, and residual variance), varies with watershed size, land use and water quality. Streams size spectra of the Ottawa-Gatineau region have relatively shallow slopes, reflecting relatively higher densities of organisms in the larger size classes compared to other ecosystem types (e.g. lakes, oceans, soils, coastal waters). Size spectra slopes, density corrected for size, number of size classes, and residual variance vary predictably along gradients of watershed size, watershed proportion of natural land use and periphyton chlorophyll a. A systematic trend of declining spectra slopes with increasing periphyton biomass suggests that ecological efficiency declines in urban eutrophic streams.

The biomass size spectrum - the power-law scaling relationship between average individual size and total biomass - has often been studied in lake and marine ecosystems, but rarely in lotic systems. The objective of this study was to test for characteristic biomass spectra in small temperate streams. Seasonal fish and macroinvertebrate data, including population abundance and biomass estimates, were collected in three wadeable, southern West Virginia streams from October 2013 to May 2015. Fish abundances were estimated with 3-pass electrofishing (depletion) surveys and individuals were weighed in the field. Macroinvertebrates were collected with a Hess sampler and returned to the lab for identification to the lowest practical level (usually genus). Published length-mass regressions were then used to estimate individual mass. All size spectra relationships (linear regression of log-log data) were highly significant (p<0.001). Size spectra intercepts were variable and may reflect seasonal differences in fish and invertebrate densities. Size spectra slopes were more consistent, with a mean slope of approximately -0.73, suggesting a common scaling relationship between stream consumers at differing trophic levels.

Made available in DSpace on 2017-07-10T14:38:26Z (GMT). No. of bitstreams: 1 louise.pdf: 1784422 bytes, checksum: 60f4897ec789c94dd1c7ec0eda64a208 (MD5) Previous issue date: 2015-02-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / 1. The size spectrum associates the abundance of individuals with the size of their body. The main objective was to investigate the influence of reservoir operation regime on the process of energy transfer in fishes assemblage, testing the hypothesis that the reservoir operation modify the spatial variability of the slopes of the size spectra. 2. For this, samples were carried out the period from January 2005 to December 2007. Data were obtained in eight reservoir with different operation regime, located in the state of Paraná, southern Brazil. To calculate the slopes of fish size spectra we used Pareto I model. The effects of operation regime on the size spectra were evaluate from the paired t test. 3. The results showed that the reservoir operation regime presents significant effect on the size spectra of the fish assemblages, wherein the slopes of spectra indicated that the reservoirs tend to present higher proportions of the small individuals. This effect were more pronounced in the reservoirs that operate in accumulation, indicating less efficient energy transfer through food webs in these environments / O espectro de tamanho associa a abundância de indivíduos com o tamanho do corpo destes. O objetivo principal foi investigar o efeito do regime de operação de reservatórios, sobre o processo de transferência de energia em assembleias ictiícas, testando-se a hipótese de que o regime de operação do reservatório altera a variabilidade espacial das inclinações dos espectros de tamanho, influenciando o fluxo de energia nos distintos reservatórios. Para isso, as amostras foram coletadas no período de janeiro de 2005 a dezembro de 2007. Os dados foram obtidos de oito reservatórios, com diferentes regimes de operação localizados no estado do Paraná, região sul do Brasil. Para calcular as inclinações dos espectros de tamanho de peixes foi utilizado um modelo de Pareto tipo I. Os efeitos dos regimes de operação sobre os espectros de tamanho foram avaliados através do Teste t pareado. Com a análise dos resultados evidenciou-se que o regime de operação do reservatório apresenta efeito significativo sobre os espectros de tamanho das assembleias de peixes, sendo que as inclinações dos espectros indicaram que os reservatórios tendem a apresentar maiores proporções de indivíduos pequenos, sendo esse efeito mais pronunciado nos reservatórios que operam em regime de acumulação, indicando menor eficiência na transferência de energia nesses ambientes

As land use transformations are the main driver of biological diversity loss at the global scale, it is essential to provide predictions and understanding of their impacts in order to improve the mitigation of ecosystem perturbations. The first objective of this project was to describe the response of biological assemblages along a gradient of urbanization and to compare metrics of watershed imperviousness in order to determine, as has been suggested in the literature, whether effective imperviousness, which represents the proportion of impervious area directly connected to the stream by storm sewers, is a better predictor of stream impairement than total imperviousness in the watershed. Decline in sensitive taxa abundance is initiated at 14% total imperviousness and 3% effective imperviousness in the Ottawa-Carleton region and, total and effective imperviousness have equivalent predictive power. The second objective of this project was to describe how the structure of metazoan assemblages in urban streams, as described by size spectra attributes (i.e. slopes, intercepts, number of logarithmic size classes occupied, and residual variance), varies with watershed size, land use and water quality. Streams size spectra of the Ottawa-Gatineau region have relatively shallow slopes, reflecting relatively higher densities of organisms in the larger size classes compared to other ecosystem types (e.g. lakes, oceans, soils, coastal waters). Size spectra slopes, density corrected for size, number of size classes, and residual variance vary predictably along gradients of watershed size, watershed proportion of natural land use and periphyton chlorophyll a. A systematic trend of declining spectra slopes with increasing periphyton biomass suggests that ecological efficiency declines in urban eutrophic streams.

Um dos principais problemas relacionados aos estudos limnológicos realizados manualmente em laboratório consiste no grande esforço, tempo de análise e trabalho especializado necessário. Esses fatores limitam a quantidade de amostras possíveis de serem analisadas em um determinado estudo, já que recursos sejam eles reagentes, recursos financeiros ou tempo são limitados. No presente trabalho foi utilizado um sistema semi-automatizado de medidas de variáveis físicas e químicas da água. O sistema é composto por uma sonda multi-parâmetro (Horiba U-22) e um sistema de posicionamento global (GPS) acoplados a um micro-computador, que realizam medidas georeferenciadas em curtos intervalos de tempo, permitindo um rastreamento horizontal das características da água. Foi ainda desenvolvido um sistema semi-automático para coleta fracionada da comunidade planctônica por meio de bomba de sucção operada por bateria e filtro coletor com rede de plâncton de diferentes aberturas de malha. O material coletado foi fotografado por meio de sistema de aquisição digital de imagens (microscópio Zeiss equipado com câmera AxionCan). Neste trabalho foi produzido um software (Planktonscan) que a partir da análise das imagens capturadas permite produzir dados com estimativas das medidas e dimensões dos organismos, calcular biovolumes e, utilizando fatores de conversão, estimar os valores de biomassa. O software apresenta uma interface para identificação, calcula a densidade dos organismos e produz relatório gráfico com informações sobre os organismos individuais e sobre a comunidade. Os equipamentos e o software foram testados em análises limnológicas e amostragem de plâncton no reservatório do Monjolinho, São Carlos, SP, em dezembro de 2005. Os resultados obtidos foram comparados com os disponíveis na literatura e demonstraram a aplicabilidade do sistema. / A major problem associated with the study of planktonic communities lies on the difficulties of analyzing the collected material, a long time-consuming procedure. Biomass determination is also a step requiring great effort and is subjected to large errors. In the present work a semi-automated system for measuring physical and chemical variables in the water was developed. The system is made up by a flow-pump, a multi-parameter probe and a global positioning system coupled to a microcomputer that performs measurements at short time intervals, allowing a horizontal tracking of the water quality, in much shorter times than traditional methods. Another semi-automated device was developed for collecting separate plankton size fractions. It uses a battery operating suction-pump coupled to a filter with different mesh nets. The collected materials are then submitted to image computer acquisition (Axion Vision Zeiss System). Additionally, in this study a software was produced (Planktonscan), that taking the measures of individuals dimensions (length, width and height) calculates biovolume and using conversion factors calculate the biomass for each zooplankton organism identified in the sample. Both systems were tested, regarding the measurement of limnological variables and plankton sampling, in the Monjolinho Reservoir, SP. The performance was good, resulting in a larger number of points sampled (60) in a shorter sampling time (1 hour) than those usually required. The biomass results provided by Planktonscan software were compared to data from literature, obtained by the traditional gravimetric method for dry weight determination and also with data generated from the use of mathematical models (length dry-weight regressions) available. The results were expressed as species population densities, biomasses and size spectra, evidencing the applicability of the models here developed.

As land use transformations are the main driver of biological diversity loss at the global scale, it is essential to provide predictions and understanding of their impacts in order to improve the mitigation of ecosystem perturbations. The first objective of this project was to describe the response of biological assemblages along a gradient of urbanization and to compare metrics of watershed imperviousness in order to determine, as has been suggested in the literature, whether effective imperviousness, which represents the proportion of impervious area directly connected to the stream by storm sewers, is a better predictor of stream impairement than total imperviousness in the watershed. Decline in sensitive taxa abundance is initiated at 14% total imperviousness and 3% effective imperviousness in the Ottawa-Carleton region and, total and effective imperviousness have equivalent predictive power. The second objective of this project was to describe how the structure of metazoan assemblages in urban streams, as described by size spectra attributes (i.e. slopes, intercepts, number of logarithmic size classes occupied, and residual variance), varies with watershed size, land use and water quality. Streams size spectra of the Ottawa-Gatineau region have relatively shallow slopes, reflecting relatively higher densities of organisms in the larger size classes compared to other ecosystem types (e.g. lakes, oceans, soils, coastal waters). Size spectra slopes, density corrected for size, number of size classes, and residual variance vary predictably along gradients of watershed size, watershed proportion of natural land use and periphyton chlorophyll a. A systematic trend of declining spectra slopes with increasing periphyton biomass suggests that ecological efficiency declines in urban eutrophic streams.

Le plancton constitue l’essentiel de la biomasse pélagique et est un acteur majeur des cycles biogéochimiques globaux qui régulent le système Terre. Il comprend l'ensemble des organismes portés par les courants, des bactéries aux méduses géantes. La communauté n'est que très rarement étudiée dans son ensemble mais plutôt par fraction. L’expédition Tara Oceans constitue le premier effort de collecte simultané de toutes les classes de taille de plancton à l’échelle de l’océan global. Pour démontrer la faisabilité de cette approche à grande échelle, des échantillons hebdomadaires de plancton, depuis les bactéries jusqu’au macroplancton gélatineux, ont d’abord été analysés en combinant plusieurs instruments d’imagerie sur une période de 10 mois, en un site de référence (point B) dans la rade de Villefranche sur mer. L’imagerie nous a permis de comparer 1) l’information fonctionnelle définie comme l’agrégation de taxons en 18 Groupes Ecologiques de Plancton (GEP), et 2) la structure en taille des communautés échantillonnées sur un intervalle de taille de 6 ordres de grandeur (0.1 µm à 10000 µm). La communauté planctonique au point B évolue en une succession écologique complexe impliquant tous les groupes planctoniques, depuis les bactéries jusqu’aux prédateurs gélatineux du macroplancton. Des évènements impulsifs, tels que des coups de vent, déclenchent des réorganisations de la communauté par un jeu d’interactions entre des contrôles « bottom-up » et « top-down ». Toutefois, le biovolume planctonique total ne varie que d’un seul ordre de grandeur au cours de la période échantillonnée. De même, la structure en taille des communautés planctoniques totales ne varie pas significativement au cours du temps. La stabilité du biovolume total et de la structure en taille suggère que des mécanismes structurant et de compensation forts maintiennent les communautés planctoniques dans un intervalle de biomasse restreint. Le couplage entre données de taille et de taxonomie révèle une réorganisation du réseau trophique entre l’été et l’hiver. En hiver, Le réseau trophique microplancton-zooplancton est dominé par la fonction de broutage. En été, le réseau trophique microplancton-zooplancton est dominé par la fonction de prédation (chaetognathes et gélatineux carnivores). En été, ce réseau trophique s’organise en deux chaines trophiques parallèles et distinctes discriminées par des relations de taille entre proies et prédateurs. Cette réorganisation souligne le rôle clef du zooplancton et de la prédation dans la structuration des communautés planctoniques. Parallèlement à cette analyse temporelle en un point fixe, nous avons montré l’existence de types caractéristiques de communautés zooplanctoniques, associés à des conditions environnementales distinctes, à partir des échantillons de l’expédition Tara Oceans, à l’échelle globale. En utilisant la même méthodologie que pour l’analyse de la dynamique temporelle, nous avons identifié trois types de communautés mésozooplanctoniques à l’échelle globale selon le type d’environement: 1) des communautés associées aux environnements productifs (upwellings côtiers et équatoriaux), 2) des communautés associées aux zones de minimum d’oxygène (OMZs, « Oxygen Minimum Zones »), et 3) des communautés associées aux gyres océaniques oligotrophes. Ce travail constitue une première typologie des communautés zooplanctoniques, structurées en taille et GEP, à l’échelle globale. Il sera complété dans le futur par l’intégration de données issus des autres compartiments planctoniques, et de données d’export vertical de matière organique particulaire pour affiner les estimations des relations qui existent entre phytoplancton, zooplancton et flux biogéochimiques. / Plankton constitutes the bulk of pelagic biomass and plays a major role in the global biogeochemical cycles that regulate the earth system. It encompasses all the organisms that drift with the water masses movements, from bacteria to giant medusae. Studies of the entire community are scarce, and plankton has been traditionally studied by fractions. The Tara Oceans expedition is the first attempt to simultaneously collect plankton in every size classes at the global scale. To demonstrate the feasibility of this approach, samples of plankton from bacteria to gelatinous macroplankton were collected weekly over ten months at a reference site (point B), in Villefranche Bay, northwestern Mediterranean, and analyzed using imaging techniques. Imaging enabled us to compare 1) the functional taxonomic information as derived from the analysis of 18 Plankton Ecological Groups (PEGs), and 2) the size structure of the same planktonic community over 6 orders of magnitude in size. The plankton dynamics at point B are driven by a complex succession process involving all plankton groups, from bacteria to macroplanktonic gelatinous predators. Environmental impulsive events such as wind events trigger sharp community level reorganizations via interplay of bottom-up controls followed by top-down controls. However, the total biovolume of the planktonic community varies within only one order of magnitude over the period studied. In addition, the size structure of the entire community does not vary significantly over time. The total biovolume and size structure stability suggest that strong and compensative mechanisms drive community dynamics within a narrow range of biomass variation. The use of both taxonomic and size structured data reveals a reorganization of the food web between winter and summer. In winter and spring the microplanktoniczooplanktonic food web is shaped by the grazing function. In summer, it is shaped by the predation function (chaetognaths and gelatinous predators). In summer, the food web self organizes in two distinct food chains discriminated by size relations between predators and preys. This reorganization underlines the key role of zooplankton and predation in structuring planktonic communities. In parallel to this temporal dynamics study, we used the Tara Oceans expedition samples to study the global scale distribution of mesozooplankton. We showed that characteristic mesozooplanktonic communities were associated with distinct environmental conditions, at the global scale. Using a similar methodology as for the temporal study we found that three different mesozooplanktonic communities were associated with 1) productive environments (e.g. upwellings), 2) Oxygen Minimum Zones, and 3) Oligotrophic oceanic gyres. This work is the first typology of mesozooplanktonic communities at the global scale. It will be further developed in the future by the integration of other planktonic compartments and particulate organic matter fluxes data, to improve our knowledge on the relations between phytoplankton, zooplankton and particulate organic matter fluxes.