• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 334
  • 25
  • 22
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • Tagged with
  • 448
  • 448
  • 175
  • 174
  • 156
  • 150
  • 145
  • 112
  • 54
  • 43
  • 36
  • 32
  • 32
  • 30
  • 29
  • 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.
321

Dynamics of phytoplankton in relation to tuna fish farms in Boston Bay and near-shore Spencer Gulf, South Australia

Paxinos, Rosemary, January 2007 (has links)
Thesis (Ph.D.)--Flinders University, School of Biological Sciences. / Typescript bound. Includes bibliographical references: (leaves 149-166) Also available online.
322

The potential of a stratified ontology for developing materials in community-based coastal marine environmental education processes /

Davies, Siân May. January 2009 (has links)
Thesis (M.Ed. (Education)) - Rhodes University, 2009.
323

The application of integrated environmental management to improve storm water quality and reduce marine pollution at Jeffreys Bay (South Africa) /

Seebach, Rudi Dieter. January 2006 (has links)
Thesis (M. Sc. (Environmental Science))--Rhodes University, 2006.
324

Implicações de políticas de conservação e desenvolvimento na pesca artesanal costeira em uma área marinha protegida da Baía da Ilha Grande / Implications of environment and development policies on coastal artisanal fishery in a marine protected area in Ilha Grande Bay

Freitas, Rodrigo Rodrigues de, 1978- 06 April 2014 (has links)
Orientadores: Cristiana Simão Seixas, Sônia Regina da Cal Seixas / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Filosofia e Ciências Humanas / Made available in DSpace on 2018-08-25T21:46:05Z (GMT). No. of bitstreams: 1 Freitas_RodrigoRodriguesde_D.pdf: 8112880 bytes, checksum: 36ac3284fd1100d88509d1ebc45d979d (MD5) Previous issue date: 2014 / Resumo: Quase todo território dos municípios do litoral sul do Rio de Janeiro (Paraty e Angra dos Reis) está incluído em alguma categoria de Área Protegida. Este estudo visa investigar as implicações das políticas de conservação da biodiversidade e de desenvolvimento na pesca artesanal em uma Área Marinha Protegida, a Estação Ecológica (ESEC) de Tamoios. Para tanto, foram analisadas as respostas das instituições (formais e informais) de gestão da pesca artesanal costeira às mudanças socioecológicas ocorridas nos últimos cinqüenta anos no nível local e regional (Baía da Ilha Grande). Um segundo objetivo foi investigar quais mudanças no arranjo institucional da ESEC de Tamoios possuem potencial para promover o aumento na robustez institucional da pesca artesanal costeira e contribuir com as dinâmicas territoriais de desenvolvimento em curso no sistema socioecológico. O trabalho de campo foi realizado nas duas comunidades mais afetadas pela ESEC de Tamoios durante cento e cinquenta e quatro dias distribuídos ao longo de dois anos e oito meses entre fevereiro de 2011e setembro de 2013. O método de pesquisa foi baseado na teoria fundamentada na prática, e as técnicas de coleta de dados incluíram: (i) entrevistas semiestruturadas e abertas com cento e quarenta e oito indivíduos; (ii) revisão de políticas e análise de fontes documentais; (iii) observação direta em arenas de tomada de decisão e; (iv) observação participante em pescarias. Os desafios e oportunidades para o desenvolvimento territorial da Baía da Ilha Grande são discutidos com base nas respostas do Estado à crise nos recursos pesqueiros e na literatura sobre sistemas socioecológicos. No nível local são apresentadas as inovações técnicas nas artes de pesca, no comércio e nas instituições de gestão dos recursos pesqueiros. Os princípios para o design de instituições robustas foram comparados com a situação da pesca artesanal nas comunidades e com as reivindicações dos pescadores artesanais. São discutidos os desafios e as oportunidades para processos de cogestão adaptativa envolvidos na análise do jogo de atores para promover mudanças nos arranjos institucionais da ESEC de Tamoios / Abstract: Almost the entire territory of municipalities in the Rio de Janeiro State South litoral (Paraty e Angra dos Reis) is included in some Protected Area category. This study investigates the implications of biodiversity conservation and development policies on artisanal fisheries at a Marine Protected Area, namely the Ecological Station (ESEC) of Tamoios. Coastal fisheries management institutions responses (formal or informal) to changes in the last fifty years were analysed in local and regional (Ilha Grande Bay) levels. A second objective was to investigate which changes in the institutional arrangement ESEC of Tamoios have the potential to increase institutional roubustness of coastal artisanal fisheries and contribute to on-going territorial development dynamics in the socio-ecological system. Field work was undertaken at two of the most affected communities by the ESEC of Tamoios during one hundred and fifty-four days distributed along two years and eight months between February 2011 and September 2013. The research method was based in grounded theory and techniques employed for data collection included: (i) semi-structured and open interviews with one hundred and forty-eight individuals; (ii) policies review and analysis of documented sources; (iii) direct observation in decision making arenas and; (iv) participant observation in fishing activities. The challenges and opportunities for territorial development at Ilha Grande Bay are discussed based in responses by the State to the crisis in fishery resources and in socio-ecological systems literature. Local level technical inovations in fishing gears, commerce and fisheries resources management institutions are also presented. The principles for designing roubust institutions are compared to the current condition of artisanal fisheries in the studied communities and with artisanal fisheries claims. The potential for adaptive co-management processes related to the analysis of stakeholders interactions to promote changes in the institutional arrangement of the ESEC of Tamoios are discussed / Doutorado / Aspectos Biológicos de Sustentabilidade e Conservação / Doutor em Ambiente e Sociedade
325

Variation génétique et persistance des populations en milieu marin : implications pour la conservation / Genetic variation and population persistence in marine systems : implications for conservation

Dalongeville, Alicia 22 September 2017 (has links)
Les écosystèmes marins sont soumis à des changements environnementaux rapides sous l’impact des pressions anthropiques croissantes qui menacent la persistance des espèces et des populations locales. Comprendre les effets de la variabilité génétique et des capacités de dispersion sur la persistance des espèces marines, est donc un enjeu majeur pour la conservation de la biodiversité. Mes travaux de doctorat répondent ainsi à deux objectifs principaux : (i) évaluer la distribution spatiale et les déterminants de la variation génétique de populations de poissons marins côtiers (ii) estimer les réponses des populations aux changements climatiques afin de mieux comprendre leur capacité de persistance.J’ai d’abord montré, à partir d’une synthèse bibliographique réalisée sur 31 espèces de poissons méditerranéens, que les traits écologiques liés à la mobilité et à la taille des populations influencent fortement le niveau de diversité génétique intra-populationnelle des espèces. Ensuite, j’ai étudié les déterminants de la variation génétique spatiale à partir des données récoltées sur 727 individus de rouget de roche (Mullus surmuletus) issus de 72 sites autour la Mer Méditerranée et regroupés en 47 groupes génotypés pour 1153 marqueurs SNP. Des analyses de génétique du paysage ont montré que la dispersion larvaire structure la variation génétique de l’espèce à moyenne et petite échelle spatiale (<1 000km), alors que l’isolement géographique, possiblement dû à l’histoire démographique des populations ou à l’adaptation, est le principal facteur structurant à plus large échelle. Finalement, l’étude de la variation génétique adaptative de M. surmuletus réalisée à l’aide d’un criblage génomique a mis en évidence une potentielle réponse adaptative de l’espèce au gradient Est-Ouest de salinité en Méditerranée.Dans un second temps, un modèle démo-génétique simulant la dynamique et la résilience des populations de coraux dans l’Indopacifique a montré qu’un mécanisme de « sauvetage évolutif » permet aux génotypes adaptés aux eaux les plus chaudes de diffuser entre les populations grâce à la connectivité larvaire. Ce mécanisme favorise la persistance des populations en permettant leur adaptation à des changements environnementaux qui conduiraient sans cela à des déclins, voir des extinctions locales.Finalement, l’ensemble de ces travaux ont mis en évidence la nécessité de considérer la connectivité et le potentiel évolutif des espèces dans les stratégies de conservation, afin de maximiser leur capacité de résilience et de persistance à long terme en dépit des crises environnementales de plus en plus prononcées. / World marine ecosystems are experiencing unprecedented anthropic pressures inducing rapid environmental changes that threaten the persistence of wild species and their local populations. Hence, understanding the effects of genetic variability and dispersal capacities on marine population persistence is a key issue for the conservation of biodiversity. My PhD work had two main objectives: (i) evaluate the spatial distribution and drivers of genetic variation across coastal marine fish populations, and (ii) estimate the response of populations to climate changes in order to better understand their ability to persist.First, by performing a synthesis of published literature on 31 Mediterranean fish species, I showed that ecological traits related to mobility and population size strongly influence the level of within-population genetic diversity across species. Then, I studied the drivers of spatial genetic variation using genetic data from 727 individuals of the stripped red-mullet (Mullus surmuletus) collected in 72 sites around the Mediterranean Sea, and grouped into 47 pools genotyped for 1153 single nucleotide polymorphism (SNP) markers. Seascape genetic analyses showed that larval dispersal predominantly structures M. surmuletus genetic variation at intermediate and local spatial scales (<1000 km), whereas geographic isolation, due to population demographic history or adaptation, is the main driver at larger spatial scale. Lastly, studying the adaptive genetic variation of M. surmuletus using genome scan revealed a potential adaptive response of this species to the East-West gradient in salinity across the Mediterranean Sea.Subsequently, using a demo-genetic model to simulate coral population dynamics and resilience across the Indo-pacific corals, I showed that the process of ‘evolutionary rescue’ can help genotypes adapted to warm ocean waters to move and migrate between populations thanks to larval connectivity. Evolutionary rescue can thus promote the persistence of populations by allowing them to adapt to environmental changes that would otherwise lead to population declines or even local extinctions.Finally, all of these results highlighted the need to better consider connectivity and the evolutionary potential of species in conservation strategies, in order to maximize their resilience capacity and long-term persistence in the face of more severe environmental crises.
326

Marine Seaweed Invasions : the Ecology of Introduced <i>Fucus evanescens</i>

Wikström, Sofia A. January 2004 (has links)
<p>Biological invasions are an important issue of global change and an increased understanding of invasion processes is of crucial importance for both conservation managers and international trade. In this thesis, I have studied the invasion of the brown seaweed <i>Fucus evanescens</i>, to investigate the fate and effect of a perennial, habitat-forming seaweed introduced to a coastal ecosystem. A long-term study of the spread of <i>F. evanescens</i> in Öresund (southern Sweden) showed that the species was able to expand its range quickly during the first 20 years after the introduction, but that the expansion has been slow during the subsequent 30 years. Both in Öresund and in Skagerrak, the species is largely restricted to sites where native fucoids are scarce. Laboratory experiments showed that the restricted spread of <i>F. evanescens</i> cannot be explained by the investigated abiotic factors (wave exposure and salinity), although salinity restricts the species from spreading into the Baltic Sea. Neither did I find evidence for that herbivores or epibiota provide biotic resistance to the invader. On the contrary, <i>F. evanescens</i> was less consumed by native herbivores, both compared to the native fucoids and to <i>F. evanescens</i> populations in its native range, and little overgrown by epiphytes. Instead, the restricted spread may be due to competition from native seaweeds, probably by pre-occupation of space, and the establishment has probably been facilitated by disturbance. </p><p>The studies provided little support for a general enemy release in introduced seaweeds. The low herbivore consumption of <i>F. evanescens</i> in Sweden could not be explained by release from specialist herbivores. Instead, high levels of chemical anti-herbivore defence metabolites (phlorotannins) could explain the pattern of herbivore preference for different fucoids. Likewise, the low epibiotic colonisation of <i>F. evanescens </i>plants could be explained by high resistance to epibiotic survival. This shows that colonisation of invading seaweeds by native herbivores and epibionts depends on properties of the invading species. The large differences between fucoid species in their quality as food and habitat for epibionts and herbivores imply that invasions of such habitat-forming species may have a considerable effect on a number of other species in shallow coastal areas. However, since <i>F. evanescens</i> did not exclude other fucoids in its new range, its effect on the recipient biota is probably small.</p>
327

Ecological connectivity, adult animal movement, and climate change: implications for marine protected area design when data are limited

Friesen, Sarah K 15 July 2019 (has links)
Marine protected areas (MPAs) are important conservation tools that can support the resilience of marine ecosystems. Many countries, including Canada, have committed to protecting at least 10% of their marine areas under the Convention on Biological Diversity’s Aichi Target 11, which includes connectivity as a key aspect. Connectivity, the movement of individuals among habitats, can enhance population stability and resilience within and among MPAs. This thesis aimed to understand regional spatial patterns of marine ecological connectivity, specifically through the mechanism of adult movement, and how these patterns may be affected by climate change. I used the Northern Shelf Bioregion in British Columbia, Canada, as a case study for four objectives: (1) evaluate potential connectivity via adult movement for the entire bioregion, using habitat proxies for distinct ecological communities; (2) assess potential connectivity via adult movement among existing and potential MPAs, using the same habitat proxies; (3) model potential connectivity via adult movement among marine protected areas for two focal species (Metacarcinus magister and Sebastolobus alascanus) and predict how this interconnectedness may shift based on projected ocean temperature changes; and (4) contribute the results of these analyses to the MPA technical team’s ongoing planning process so that connectivity may be considered in the implementation of a new MPA network in the bioregion. This thesis developed an approach to assess and design MPA networks that maximize inferred connectivity within habitat types for adult movement when ecological data are limited. It applied least-cost theory and circuit theory to model MPA suitability and interconnectedness, finding that these are projected to decrease for Sebastolobus alascanus but increase for Metacarcinus magister. I showcased some methods that may be used in MPA design and evaluation, with lessons for other contexts. Importantly, this thesis informed an ongoing MPA planning process, enabling ecological connectivity to be considered in the establishment of a new MPA network in the bioregion. Overall, this work provided examples for incorporating connectivity and climate change into MPA design, highlighting what is possible even when data are limited. / Graduate
328

Distribuição espaço-temporal de Olivella minuta (LNK,1807) (Mollusca, Gastropoda, Olividae) na zona entremarés da Baía do Araçá, litoral norte do Estado de São Paulo / Spatial-temporal distribution of Olivella minuta (LINK, 1807) (Mollusca, Gastropod, Olividae) in the intertidal zone of Araçá Bay, southeastern coast of São Paulo state, Brazil

Camargo, Rita Monteiro 07 February 2013 (has links)
O objetivo deste trabalho foi analisar a distribuição espaço-temporal de um representante da macrofauna de praias arenosas protegidas. As abordagens em diferentes escalas (mesoescala, microescala e escala temporal) foram empregadas. O gastrópode Olivella minuta, abundante na região entremarés da Baía do Araçá, foi utilizado para essas análises. Para o estudo em mesoescala, 16 estações foram demarcadas na região entremarés (julho/2009) e, em cada uma, foram coletadas 8 amostras biológicas e 3 de sedimento. Alguns fatores abióticos (carbonato de cálcio, matéria orgânica e coeficiente de seleção) influenciaram negativamente a abundância do gastrópode, enquanto relações entre O. minuta e as demais espécies da macrofauna não foram evidentes. Em microescala, em poças de maré (metros) e em \"ripple marks\" (centímetros) verificou-se que em escala de centímetros, o gastrópode foi mais abundante em locais com maior conteúdo de água no sedimento, enquanto em escala de metros a abundância não diferiu dentro e fora das poças. Em escala temporal, foram observadas flutuações mensais da densidade da população de O. minuta, com diminuição/ausência de indivíduos entre fevereiro e março, o que sugere a ocorrência de migrações e mortalidade. O presente trabalho mostrou que a distribuição desse gastrópode é influenciada por diferentes fatores que atuam em diferentes escalas. / The objective of this study was to analyze the temporal and spatial distribution of one of the species representative of the macrofauna of sheltered sandy beaches. Measurements using different scales (mesoscale, microscale and time scale) were utilized. The gastropod Olivella minuta, which is abundant in the intertidal region of Baía do Araçá, was used for these analyses. For the mesoscale study, 16 stations were determined within the intertidal region (July/2009) and, in each station, 8 biological samples and 3 samples of sediment were collected. Some abiotic factors (calcium carbonate, organic matter and selection coefficient) had a negative influence on the abundance of the gastropod, while relationship between the O. minuta and other species of the macrofauna were not evident. In a microscale study of tidal ponds (meters) and ripple marks (centimeters), it was observed that, in a centimeter scale, the gastropod was more abundant in places where there was more water in the sediment, whereas in a meter scale the abundance didn\'t vary in or out of the ponds. In a temporal scale, monthly fluctuations of the O. minuta population\'s density were observed, with reduction/absence of individuals between February and March, which suggests that migration and mortality occurred. This study showed that the distribution of O. minuta is influenced by different factors which act in different scales.
329

The Role Of Disturbance In The Genotypic And Morphological Diversity Of Halodule Wrightii

Unknown Date (has links)
Seagrasses are important foundation species in coastal ecosystems. Genetic diversity of seagrasses can influence a number of ecological factors including, but not limited to, disturbance resistance and resilience. Seagrasses in the Indian River Lagoon (IRL), Florida are considered to be highly disturbed due to frequent events, like algal blooms, that impair water quality, reducing available light for seagrass growth. Halodule wrightii is a dominant seagrass throughout the IRL, but its genetic diversity has only been quantified in a few Gulf of Mexico and Florida Bay populations and little is known about its potential ecological consequences. I quantified the genetic variation of H. wrightii using microsatellite markers in the southern IRL to determine: (i) how disturbance history influenced genetic diversity, (ii) if morphology of clones was, in part, genetically controlled and related to disturbance history, and (iii) if genotypes showed phenotypic plasticity in response to disturbances. In the IRL, H. wrightii populations exhibited moderate genetic diversity that varied with disturbance history. The disturbance history of a population was classified by the variance in the percent occurrence of H. wrightii over a 16-year period. Genotypic richness and clonal diversity of H. wrightii increased with increasing disturbance histories. Other genetic diversity measures (e.g., allelic richness, observed heterozygosity) did not change with disturbance history. These findings suggest that impacts to seagrass coverage over time can change the genotypic composition of populations. When different genotypes of H. wrightii were grown in a common garden, differences in leaf characteristics among genotypes provided evidence that morphological trait variation is, in part, explained by genetic variance. The disturbance history of genotypes did not directly affect morphological traits. However, significant genotype x site (within disturbance history) interactions found greater variation in shoot density and below ground traits of H. wrightii genotypes from sites of intermediate disturbance history. Traits of H. wrightii were shown to be phenotypically plastic. Significant genotype x environment interactions for shoot density and height demonstrated that genotypes responded differently by increasing, decreasing, and not changing sizes in response to light reduction. Genetic diversity of H. wrightii has strong implications for ecological function in coastal communities. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
330

Salinity Assessment, Change, and Impact on Plant Stress / Canopy Water Content (CWC) in Florida Bay using Remote Sensing and GIS

Unknown Date (has links)
Human activities in the past century have caused a variety of environmental problems in South Florida. In 2000, Congress authorized the Comprehensive Everglades Restoration Plan (CERP), a $10.5-billion mission to restore the South Florida ecosystem. Environmental projects in CERP require salinity monitoring in Florida Bay to provide measures of the effects of restoration on the Everglades ecosystem. However current salinity monitoring cannot cover large areas and is costly, time-consuming, and laborintensive. The purpose of this dissertation is to model salinity, detect salinity changes, and evaluate the impact of salinity in Florida Bay using remote sensing and geospatial information sciences (GIS) techniques. The specific objectives are to: 1) examine the capability of Landsat multispectral imagery for salinity modeling and monitoring; 2) detect salinity changes by building a series of salinity maps using archived Landsat images; and 3) assess the capability of spectroscopy techniques in characterizing plant stress / canopy water content (CWC) with varying salinity, sea level rise (SLR), and nutrient levels. Geographic weighted regression (GWR) models created using the first three imagery components with atmospheric and sun glint corrections proved to be more correlated (R^2 = 0.458) to salinity data versus ordinary least squares (OLS) regression models (R^2 = 0.158) and therefore GWR was the ideal regression model for continued Florida Bay salinity assessment. J. roemerianus was also examined to assess the coastal Everglades where salinity modeling is important to the water-land interface. Multivariate greenhouse studies determined the impact of nutrients to be inconsequential but increases in salinity and sea level rise both negatively affected J. roemerianus. Field spectroscopic data was then used to ascertain correlations between CWC and reflectance spectra using spectral indices and derivative analysis. It was determined that established spectral indices (max R^2 = 0.195) and continuum removal (max R^2= 0.331) were not significantly correlated to CWC but derivative analysis showed a higher correlation (R^2 = 0.515 using the first derivative at 948.5 nm). These models can be input into future imagery to predict the salinity of the South Florida water ecosystem. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Page generated in 0.0514 seconds