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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Mass Conservation Analysis For The Lower St. Johns River Using Continuous And Discontinuous Galerkin Finite Element Methods

Thomas, Lillie E 01 January 2011 (has links)
This thesis provides a mass conservation analysis of the Lower St. Johns River for the purpose of providing basis for future salinity transport modeling. The analysis provides an assessment of the continuous (CG) and discontinuous (DG) Galerkin finite element methods with respect to their mass conservation properties. The following thesis also presents a rigorous literature review pertaining to salinity transport in the Lower St. Johns River, from which this effort generates the data used to initialize and validate numerical simulations. Two research questions are posed and studied in this thesis: can a DG-based modeling approach produce mass conservative numerical solutions; and what are the flow interactions between the river and the marshes within the coastal region of the Lower St. Johns River? Reviewing the available data provides an initial perspective of the ecosystem. For this, salinity data are obtained and assembled for three modeling scenarios. Each scenario, High Extreme, Most Variable, and Low Extreme, is 30 days long (taken from year 1999) and represents a unique salinity regime in the Lower St. Johns River. Time-series of salinity data is collected at four stations in the lower and middle reaches of the Lower St. Johns River, which provides a vantage point for assessing longitudinal variation of salinity. As an aside, precipitation and evaporation data is presented for seven stations along the entire St. Johns River, which provides added insight into salinity transport in the river. A mass conservation analysis is conducted for the Lower St. Johns River. The analysis utilizes a segmentation of the Lower St. Johns River, which divides the domain into sections iv based on physical characteristics. Mass errors are then calculated for the CG and DG finite element methods to determine mass conservative abilities. Also, the flow interactions (i.e., volume exchange) between the river and marshes are evaluated through the use of tidal prisms. The CG- and DG- finite element methods are then tested in tidal simulation performance, which the results are then compared to observed tides and tidal currents at four stations within the lower portion of the Lower St. Johns River. Since the results show that the DG model outperforms the CG model, the DG model is used in the tidally driven salinity transport simulations. Using four stations within the lower and middle part of the Lower St. Johns River, simulated and observed water levels and salinity concentrations are compared.
62

The Causeway: Bridging Disaster Relief, Recovery, and Climate Adaptation in the Anton Ruiz Watershed

Schiavoni, Alexandra Elizabeth 10 July 2019 (has links)
The impact of natural disasters is often exacerbated by a disparity between resources for relief and recovery. When the barrio of Punta Santiago in Puerto Rico was devastated by Hurricane Maria in September of 2017, many of its residents lived in the remains of their homes for over a year while they rebuilt from wind damage and flood waters that rose over 6 feet. As climate change leads to an even more constrained timeline for response with increasingly frequent and intense storms, the future of Punta Santiago and other coastal communities worldwide will necessitate strategies ranging from nature-based shore protection systems, coastal setbacks, and managed retreat. This thesis investigates the time disparate processes of disaster relief, recovery, and climate adaptation through the lens of their impact upon the interdependent identities of people and place as informed by theorists and designers including J.B. Jackson and Patrick Geddes. My approach works from the scale of the Antón Ruíz watershed to the delta to uncover the historical and contemporary processes that knit people in the region to the land. I identify commonalities in the immediate recovery needs and long-term resiliency of the community and ecosystems, and seek to support ongoing globally significant research of the rare coastal systems surrounding Punta Santiago. The proposed design, a causeway linking the coast to the hills, dovetails disaster relief and recovery with climate adaptation by providing a persistent connection that restores and reveals the dynamic coastal landscape. / Master of Landscape Architecture / Global warming is correlated with an increase in sea level rise, atmospheric moisture (water content in the air), and surface sea temperatures. The body of research around the complex interaction of these factors is growing, but current projections are that warmer seas will cause more intense hurricanes. Coastal communities, particularly those with fewer economic resources, bear the brunt of this trend and recovery is more difficult with each passing storm. After Hurricane Maria struck in September 2017, many residents of the barrio of Punta Santiago in Puerto Rico lived in the remains of their homes for over a year with little resources to rebuild from the severe wind damage and flood waters that rose over 6 feet. Recovery is still underway almost two years later. A sustainable way forward for Punta Santiago and other coastal communities worldwide necessitates strategies ranging from natural shore stabilization techniques like mangrove buffers and living reefs to restrictions on coastal development, and even the relocation of communities. This thesis investigates the time disparate processes of disaster relief, recovery, and climate adaptation through the lens of their impact upon the interdependent identities of people and place as informed by theorists and designers including J.B. Jackson and Patrick Geddes. My approach works from the scale of the Antón Ruíz watershed to the delta to uncover the historical and contemporary land use that knit people in the region to the land. I identify commonalities in the immediate recovery needs and long-term resiliency of the community and ecosystems, and seek to support ongoing globally significant research of the rare coastal systems surrounding Punta Santiago. The proposed design, a causeway linking the coast to the hills, dovetails disaster relief and recovery with climate adaptation by providing a persistent connection that restores and reveals the dynamic coastal landscape.
63

INDICADORES POPULACIONAIS E ECOLÓGICOS DE PEIXES-BOIS-MARINHOS (Trichechus manatus manatus) EM DUAS ÁREAS DE MANGUEZAIS E MARISMAS NO MARANHÃO / POPULATION AND ECOLOGICAL INDEX FOR MANATEES (Trichechus manatus manatus) IN TWO MANGROVES AND SALT-MARSHES AREAS OF MARANHÃO

Alvite, Carolina Mattosinho de Carvalho 28 September 2008 (has links)
Made available in DSpace on 2016-08-19T18:20:37Z (GMT). No. of bitstreams: 1 Carolina Mattosinho de Carvalho Alvite.pdf: 6763080 bytes, checksum: d171930fac0eadfa71fb881a91e48018 (MD5) Previous issue date: 2008-09-28 / INSTITUTO INTERNACIONAL DE EDUCAÇÃO DO BRASIL / The Brazilian north coast has the largest continuous area of mangroves on the planet and hosts large groups of manatees, aquatic mammal critically endangered. This research examines the efforts of fix point methodology of observation of manatees on relevant sites of occurrence, from data collected while on the beach in Guarapiranga (GUA), São José de Ribamar and on Ilha do Gato (IGA), Baía do Tubarão. This article discusses the application of population index for manatees in a ecological-environmental study on IGA (02°31'09, 81"S, 43°37'09,13" W), Mapari estuary, serving as a methodological basis to be replicated in other parts of the coast. From the application of index developed with data from fixed point and the characterization of the environmental area, the study provides evidence to infer the relative abundance of the population and it trends over the years, discussing aspects of spatial and temporal use of estuary. Was characterized: temperature, salinity, pH, conductivity, depth, current speed, tides fluctuations, rainfall, biomass of salt-marsh (Spartina alterniflora), and density of plants/seedlings of mangrove. The region showed a seasonal variation marked by two regimes of water, rain (January-July) and dry (August-December), with annual rainfall of 1,704mm. The oceanographic parameters ranged from tides: salinity (FLOOD=14.8; EBB=1.5), conductivity (FLOOD=27.1; EBB=6.3mS/cm), speed of current (FLOOD=46; EBB=88m/s). The tide height ranged from 0.0-5.4m. Biomass of S. alterniflora ranged from 860g/m2(RAIN) to 430g/m2(DRY) and density of plants/seedlings of 74ind/m2(RAIN) to 21ind/m2(DRY). Variations between rain/dry seasons influenced the availability of fresh water and food resources, important factors in the choice of areas for manatees. The estuary was shown with strong influence of daily tide fluctuations, reflecting changes in salinity, current speed, depth and access to plant resources by manatees. Between 2004/2007, manatees were monitored in 1241 days (GUA = 625, IGA = 616). The population analysis carried out in two sites of Maranhão indicated a trend of reducing population between 2004 and 2006, with stabilization between 2006 and 2007. The IGA had the highest relative abundance and showed to be important site of occurrence of manatees, which used as an area of reproduction, parental care, food and rest. IGA in the number of manatees seems to have relation with the seasons, being sighted in greater numbers in the rainy season. Variations during the tides also shown to influence the pattern of use of the IGA, and the manatees were more frequent in the tides ebb and flood. The main type of human activity in the IGA was not motorized boat and it had no negative influence on the occurrence of fish-horse. Knowledge about characteristics of coastal ecosystems is essential for development of appropriate conservation strategies for manatees in the Brazilian north coast. / O litoral norte do Brasil possui a maior área contínua de manguezais do planeta e abriga importantes grupos de peixes-bois-marinhos, mamífero aquático criticamente ameaçado de extinção. Esta pesquisa analisa o esforço da metodologia de observação de peixes-bois por meio de plataformas fixas em sítios de relevante ocorrência, a partir dos dados coletados simultaneamente na praia de Guarapiranga (GUA), São José de Ribamar, e na barra da Ilha do Gato (IGA), Baía do Tubarão. Também é discutida a aplicação de indicadores populacionais e ecológicos para peixes-bois em estudo de caso na barra da Ilha do Gato (02°31 09,81 S; 43°37 09,13 W), estuário do rio Mapari, servindo de base metodológica para ser replicada em outros pontos da costa. A partir da aplicação dos indicadores elaborados com os dados de ponto fixo e da caracterização ambiental da área, a pesquisa fornece elementos para inferir a abundância relativa da população e como esta se comporta ao longo dos anos, discutindo aspectos da utilização espacial e temporal do estuário. Para caracterização ambiental da IGA, foram levantados os seguintes parâmetros: temperatura (ar-água), salinidade, pH, condutividade, profundidade, velocidade de corrente, amplitude de marés, precipitação pluviométrica, biomassa de marisma (Spartina alterniflora), densidade de plântulas de mangue. A região mostrou uma variação sazonal do regime hidrológico: chuva (janeiro-julho) e seca (agosto-dezembro), com precipitação pluviométrica anual de 1704mm. Os parâmetros oceanográficos médios variaram entre as marés: salinidade (ENCH=14,8, VAZ=1,5), condutividade (ENCH=27,1, VAZ=6,3 mS/cm), velocidade de corrente (ENCH=46; VAZ=88 m/s). A altura da maré variou entre 0,0-5,4m. A biomassa de S. alterniflora variou de 860g/m2(chuva) a 430g/m2(seca) e a densidade de plântulas de 74 ind/m2(chuva) a 21 ind/m2(seca). As variações entre os períodos de seca e chuva influenciaram na disponibilidade de água doce e recursos vegetais, fatores determinantes na escolha de áreas pelos peixes-bois. O estuário mostrou-se com forte influência da variação diária nos regimes de maré, refletindo em mudanças na salinidade, velocidade de corrente, profundidade e acesso aos recursos vegetais pelos peixes-bois. Entre 2004/2007, os peixes-bois foram monitorados em 1.241 dias (GUA=625, IGA=616). As análises populacionais realizadas nos dois sítios do Maranhão indicaram uma tendência de redução populacional entre 2004 e 2006, com estabilização entre 2006 e 2007. A Ilha do Gato apresentou a maior abundância relativa e mostrou ser importante sítio de ocorrência de peixes-bois, sendo utilizada como área de reprodução, cuidado parental, alimentação e repouso. Na IGA o número de peixes-bois parece ter relação com as estações do ano, sendo avistados em maior número no período chuvoso. As variações nas fases de maré também mostraram ter influência no padrão de utilização da IGA, sendo que os peixesbois estiveram mais freqüentes nas marés vazantes e cheias. A ocorrência de embarcações não motorizadas foram a atividade humana com maior freqüência na IGA e não teve influência negativa na ocorrência dos peixes-bois. O conhecimento sobre as características dos ecossistemas costeiros é essencial para a elaboração de estratégias de conservação adequadas para o peixe-boi-marinho na região norte do Brasil.
64

The Influence of Seawater and Sulfate Reduction on Phosphate Release from Tidal Wetland Soils in the St. John’s River, Florida

Williams, Asher 01 January 2012 (has links)
Climate change and increasing sea level elevation are predicted to increase salinity in estuarine tidal wetlands in the Southeastern United States. Since much of the ecosystem function in these areas is predicated upon salinity regimes, many fundamental changes are likely to occur as a result. The influence of salinity and SO4 2- reduction on PO4 3- release from tidal wetland soils was evaluated along a salinity gradient at three sites in The St. John’s River, Florida using both field and laboratorybased methods. Porewater was sampled over the course of 10 months to determine ambient levels of SO4 2- and PO4 3-. Lab-based experiments, soils samples were subjected to seawater and SO4 2- treatments in an attempt to induce PO4 3- release. Salinity was lowest at Sixmile Creek (0.45 ± 0.1 g kg-1) and Goodby’s Creek (2.05 ± 2.3 g kg-1) and much higher at Sister’s Creek (27.81 ± 3.1 g kg-1). The organic content of soils was highest (82.35% ± 5.11) at Sixmile Creek, intermediate at Goodby’s Creek (64.45% ± 7.02) and lowest at Sister’s Creek (32.11% ± 9.61). Total soil P was highest at the freshwater Sixmile Creek (1101.64 ± 220.2 μg g-1), intermediate at the brackish Goodby’s Creek (719.61 ± 114.3 μg g-1) and lowest at the Sister’s Creek saltmarsh (475.85 ± 110.9 μg g-1). Porewater PO4 3- was higher at Sixmile and Goodby’s Creek sites (9.44 ± 15.6, 8.99 ± 14.7 !g L-1, respectively) compared to Sister’s Creek (0.6 ± 3.1 !g L-1). Porewater SO4 2- was lower at Sixmile (70.73± 57.58 !g L-1) and Goodby’s Creeks (124.35 ± 152.5 !g L-1) compared to Sister’s Creek (1931.41 ± 557.82 !g L-1). Temporal and spatial trends indicated that SO4 2- and PO4 3- in porewater was likely due to floodwater content and that direct reaction between analytes in soils was unlikely. The addition of aerated seawater failed to cause PO4 3- release from any sites. The incubation of soils under anaerobic conditions, in the presence of Na2SO4 induced SO4 2- reduction, but inhibited PO4 3- flux from both Sixmile and Goodby’s Creek, which is attributed here to likely S- toxicity (Roychoudhury et al., 1999). PO4 3- flux from Sister’s Creek increased in association with Na2SO4 concentration, likely due to more Fe availability to mitigate Stoxicity. Ambient seawater additions to soils under anaerobic conditions followed a similar trend, but the results were not statistically conclusive. Overall, both field and labbased data indicated that Tidal wetland porewater PO4 3- likely originates from floodwaters and that increased salinity and SO4 2- reduction did not directly enhance soil PO4 3- fluxes.
65

Limnological characteristics and zooplankton community structure of Mediterranean coastal lagoons undergoing restoration

Badosa i Salvador, Anna 06 March 2007 (has links)
Entre 1999 i 2003 es va desenvolupar un projecte Life de restauració a la maresma de La Pletera, afectada per un pla urbanització, i a la llacuna del Ter Vell, amb un elevat grau d'eutròfia (aiguamolls del Baix Ter, NE Península Ibèrica). L'objectiu d'aquesta tesi és establir el funcionament d'ambdós ecosistemes, analitzar-ne la problemàtica ambiental i avaluar els efectes de la restauració. A la maresma de la Pletera, es va analitzar el paper de la hidrologia en la composició i dinàmica dels nutrients i del zooplàncton en cinc llacunes, tres de les quals havien estat creades dins el projecte de restauració com a nous refugis per una espècie de peix amenaçada (Aphanius iberus). La hidrologia es va caracteritzar per un llarg període de confinament sense entrades d'aigua, interromput de manera irregular per inundacions puntuals. La dinàmica del nitrogen inorgànic es va relacionar amb les entrades d'aigua, mentre que la del fòsfor, del nitrogen total i de la matèria orgànica es va relacionar amb els processos d'acumulació i reciclatge intern durant el confinament. El zooplàncton es va analitzar mitjançant la combinació d'aproximacions taxonòmiques i de mides. L'estructura de mides de la comunitat es va veure més afectada per les interaccions tròfiques (depredació i competència) mentre que l'estructura taxonòmica va ser més sensible a factors abiòtics (nutrients). El ràpid creixement de la població A. iberus en les noves llacunes va suggerir que aquestes havien proporcionat l'hàbitat adequat per a l'espècie, almenys a curt termini. Les actuacions de restauració a la llacuna del Ter Vell es van centrar en la millora de la qualitat de l'aigua mitjançant (1) la construcció d'uns aiguamolls per depurar l'aigua d'entrada i (2) el dragat del sediment en diversos punts. Simultàniament a la restauració, però de forma independent, la gestió agrícola de l'aigua va reduir dràsticament el cabal d'entrada d'aigua dolça a la llacuna, provocant un canvi en el règim hídric. Es van analitzar els efectes a curt termini d'aquest canvi sobre la limnologia i el zooplàncton de la llacuna. Abans del canvi, la hidrologia era artificial ja que s'havia prolongat l'entrada d'aigua dolça d'acord amb la demanda agrícola, i per tant la llacuna presentava una elevada taxa de renovació de l'aigua i majors concentracions de nutrients. Després del canvi, la hidrologia va dependre més del clima, es van reduir les entrades d'aigua i es va allargar el període de confinament. La composició y dinàmica dels nutrients va tendir a assemblar-se a l'observada a les llacunes de la maresma, mentre que la comunitat del zooplàncton no ho va fer. L'estat ecològic de la llacuna va millorar després del canvi en el règim hídric. / Between 1999 and 2003, a restoration Life project was developed in La Pletera salt marshes, affected by an urbanisation plan, and in the Ter Vell lagoon, a highly eutrophic lagoon (Baix Ter Wetlands, NE Iberian Peninsula). The aim of this thesis is to establish the natural functioning of both ecosystems, analyze their environmental problematic and also to evaluate the effects of the restoration measures.In La Pletera salt marshes, the role of the hydrological regime in the nutrient and zooplankton composition and dynamics was analysed in five brackish lagoons. Three of them were created in the framework of the restoration project as new refuges for an endangered fish species (A. iberus). The hydrology was determined by a prolonged period of confinement without water inputs, irregularly interrupted by sudden flooding events. While the dynamics of inorganic nitrogen depended on the water inputs variability, dynamics of phosphorus, total nitrogen and organic matter was related more to the cumulative mechanisms and internal recycling during the confinement periods. The zooplankton community structure was analysed by means of the combination of taxon- and size-based approaches. Whereas the community size structure was more affected by trophic interactions (predation and competition), the taxonomic structure appeared to be more sensitive to abiotic factors (nutrients). The fast growth of the size population of A. iberus in the new lagoons suggested that they had provided a suitable refuge for this species, at least in the short-term.Restoration actions in the Ter Vell lagoon were focused on the improvement of the water quality by means of (1) wetlands construction to reduce nutrient inputs and (2) sediment dredging. Simultaneously, but independent of the restoration activities, water management in agriculture drastically reduced the freshwater inflow to the lagoon and, therefore, changed the hydrological regime. The short-term effects of this hydrological change on the limnological characteristics and the zooplankton of the lagoon were analysed. Before the change, the hydrology was artificial since the freshwater flooding period was prolonged due to the high agricultural demand. As a result, the lagoon showed a high water turnover rate and high nutrient concentrations. After the change, hydrology was climate-dependent, with scarce water inputs and prolonged confinement periods. Then, the nutrient composition and dynamics tended to be more similar to those observed in the salt marsh lagoons. However, zooplankton did not tend to resemble to that of the salt marsh lagoons. The ecological status of the Ter Vell lagoon was improved after the hydrological change.
66

Studium autekologie vybraných taxonů křídových rostlin pomocí izotopů uhlíku / Autecological study of selected Cretaceous plants using stable Carbon isotopes

Zahajská, Petra January 2016 (has links)
1 Abstract This thesis presents an analysis of fossil plants from the Cenomanian Peruc-Korycany Formation of the Bohemian Cretaceous Basin and from the Bückeberg Formation of the Lower Saxony Basin in Germany. Based on earlier studies, both areas provide sediments that are considered to have developed in tidally influenced fluvial systems. Studied fossil plants are represented by ginkgoalean plant leaves (Ertemophyllum, Tritaenia), branches of conifers (Frenelopsis) and lauroid angiosperms (Eucalyptolaurus). Frenelopsis, Eretmophyllum and Tritaenia are considered to be halophytic plants, while Lauroid angiosperms were considered to grow in fresh water conditions. The fossil plants were studied using cuticle analysis and two methods of stable carbon isotope analysis: Bulk carbon isotope analysis and Compound Specific Isotope analysis. For cuticle analysis samples were observed and documented macroscopically and microscopically. To specify the environmental conditions, recent samples from three salt marshes in Great Britain were studied and analysed using the same methods as the fossil samples. The data from all observations and measurements were processed and their interpretation supported the modelled environment based on the sedimentological data. Frenelopsis were growing in a haline environment with low...

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