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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.
71

Invertebrate Community Composition Across Inundation Regimes and Its Potential to Reduce Plant Stress

Lawson, Inez Ilicia 08 September 2017 (has links)
Appreciation of the ecological and economic values associated with healthy salt marshes has led to a recent rise in the number of marshes that are being targeted for restoration by dike removal. The success of restoration is often measured by the return of marsh plants, though this overlooks a key component of salt marshes, that of the invertebrate community within marsh sediments. To evaluate the short-term recovery of these invertebrates, sediment cores were collected across an elevational gradient in a recent dike removal marsh, one and two years post removal, and a nearby reference marsh. Abundance, richness and diversity as well as morphospecies community composition were compared across treatment groups (Reference, Removal) and elevation zone (High Marsh, Low Marsh). Morphospecies richness, abundance and diversity were significantly higher in Low Marsh samples than in High Marsh samples, though no statistically significant differences were found across treatments of the same elevation (e.g., Reference Low Marsh versus Removal Low Marsh). Pair-wise ANOSIM results found significant differences between community compositions across treatments, specifically Reference Low Marsh and Removal Low Marsh. The marsh edge, the lowest point of vascular plant growth before transitioning to tide flats, is considered a high stress environment for emergent vegetation. Plant establishment and survival in this low elevation zone is limited by the tolerance to inundation duration and frequency and anoxic sediments. Bioturbation and burrowing by macroinvertebrates increases the surface area exposed to surface water for gas exchange, increasing the depth of the redox potential discontinuity layer. Crabs that make stable, maintained burrows have been shown to increase oxygen penetration into sediment, improving plant productivity. Such crabs are not found in salt marshes of the Pacific Northwest of North America. However, other burrowing invertebrates may have a positive impact on plant health in these areas by reducing abiotic stress due to anoxic sediments, thereby allowing plants to establish and survive lower in the intertidal zone. To assess this potential relationship, study plots of Distichlis spicata were selected at equivalent elevations at the lowest point of plant establishment at the marsh edge. Focal plant rhizomes were severed from upland ramets and assigned an invertebrate abundance treatment based on a visual burrow count surrounding each plant (9 cm diameter). Focal plants were visited monthly from July to September 2016, plant health variables of chlorophyll content and chlorophyll fluorescence (photosynthetic efficiency), and sediment ORP readings were collected. Plant survivorship was significantly higher in plots with invertebrates, 96% of plants in 'With Invertebrate' plots and 50% of plants in 'No Invertebrates' plots survived the duration of the study. Plant health (chlorophyll content and chlorophyll fluorescence) generally increased with increased invertebrate presence though, not statistically significant. There may be potential for improved plant productivity and resilience to plants at the marsh edge due to invertebrate burrowing activity. This benefit could help mitigate projected losses in plant productivity due to sea level rise, though more research is needed to investigate the mechanism by which these invertebrates confer a health benefit to plants at the marsh edge.
72

Habitats and macroinvertebrate fauna of the reef-top of Rarotonga, Cook Islands : implications for fisheries and conservation management

Drumm, Darrin Jared, n/a January 2005 (has links)
Throughout the Pacific, many species of echinoderms and molluscs have cultural value and are harvested extensively in subsistence fisheries. Many of these species are sedentary and often associated with distinct reef-top habitats. Despite the significance of reef habitats and their fauna for fisheries and biodiversity etc, little information has been available on the distribution of habitats and their influence on the reef-top fauna in the Cook Islands. This thesis developed a novel approach to assess the status of the shallow-water reef-tops of Rarotonga, Cook Islands, to provide critical information to fisheries and conservation managers. The approach used remote sensing (aerial photography with ground truthing) to map the spatial arrangement and extent of the entire reef-top habitats accurately, and historical wind data and coastline shape to determine the windward and leeward sides of the island. The benthic habitat maps and degree of wind exposure were used to design and undertake a stratified sampling programme to assess the distribution and abundance of the epibenthic macroinvertebrate fauna of the reef-top. I quantified the distribution and abundance of the epibenthic macroinvertebrates and how they varied with habitat, assessed the effectiveness of a traditional ra�ui (marine protected area) for conserving stocks of Trochus niloticus and other invertebrates, and investigated the reproductive biology and impacts of traditional gonad harvesting on Holothuria leucospilota. There were four major habitat types (rubble/rock, sand/coral matrix, algal rim and sand) identified, the most extensive being rubble/rock (45%) and sand/coral matrix (35%). The degree of exposure to winds was found to correlate with the reef development and habitat distribution. The assemblage composition of each major habitat type differed significantly from every other habitat. The rubble/rock habitat had the greatest substratum heterogeneity and structural complexity, and the highest number of species and individuals. The overall abundance of the fauna was dominated by holothurians (68%) and echinoids (30%), while Trochus niloticus and Tridacna maxima accounted for the remaining 2% of the total invertebrate assemblage. Clear habitat partitioning was also found for adult and juvenile Trochus niloticus and Tridacna maxima. In the traditional fishery for Holothuria leucospilota, the mature gonads of males are harvested by making an incision in the body-wall of the animal, removing the gonads and then returning the animal to the reef to allow regeneration. Monthly collections of H. leucospilota were used to describe the reproductive biology of this species. Gametogenesis and spawning were synchronous between the sexes and spawning occurred annually during summer, when water temperature and photoperiod were at their highest. Although the incision in the body-wall and gonad removal had no impact on the survival of H.leucospilota in experimental cages, their body weight, and general sheltering and feeding behaviors were affected. Gonads took at least 41 days to start regenerating, suggesting a considerable delay in the spawning of fished individuals. In 1998, five Rarotongan communities re-introduced the traditional ra�ui system of resource management, prohibiting all fishing and gathering from their reefs. The performance of the Nikao ra�ui, which had been put in place to allow trochus stocks to increase, was investigated. Comparisons of macroinvertebrate assemblage composition and species density were made between three fishing treatments, i.e. fished areas adjacent to the ra�ui, within the ra�ui after two years of protection, and in the ra�ui after it had been lifted for three weeks to allow a commercial trochus harvest. Analysis of variance on the count data for the twelve most abundant species, and non-metric multi-dimensional scaling indicated that there were no differences in the microhabitat or the invertebrate assemblage composition between the three fishing treatments. However, there were significant differences between the rubble/rock and sand/coral matrix habitat types. The results on the effectiveness of the Nikao ra�ui are equivocal, due to the small sample size, and the variability between samples which was highlighted by the wide confidence intervals. This study highlights the importance of habitat to the macroinvertebrate fauna of the reef-top and the need for accurate habitat maps to increase the cost-effectiveness of future resource surveys, to provide information to management, and for the design of Marine Protected Areas. The mapping and survey methods must be reliable and repeatable in terms of the limitations of time, and the availability of expertise, funding and resources. The results provide important information for fisheries and conservation managers of Rarotonga and other Pacific Islands to better design rigorous sampling programmes for monitoring the status of reef-top resources, and for evaluating and planning Marine Protected Areas.
73

Habitats and macroinvertebrate fauna of the reef-top of Rarotonga, Cook Islands : implications for fisheries and conservation management

Drumm, Darrin Jared, n/a January 2005 (has links)
Throughout the Pacific, many species of echinoderms and molluscs have cultural value and are harvested extensively in subsistence fisheries. Many of these species are sedentary and often associated with distinct reef-top habitats. Despite the significance of reef habitats and their fauna for fisheries and biodiversity etc, little information has been available on the distribution of habitats and their influence on the reef-top fauna in the Cook Islands. This thesis developed a novel approach to assess the status of the shallow-water reef-tops of Rarotonga, Cook Islands, to provide critical information to fisheries and conservation managers. The approach used remote sensing (aerial photography with ground truthing) to map the spatial arrangement and extent of the entire reef-top habitats accurately, and historical wind data and coastline shape to determine the windward and leeward sides of the island. The benthic habitat maps and degree of wind exposure were used to design and undertake a stratified sampling programme to assess the distribution and abundance of the epibenthic macroinvertebrate fauna of the reef-top. I quantified the distribution and abundance of the epibenthic macroinvertebrates and how they varied with habitat, assessed the effectiveness of a traditional ra�ui (marine protected area) for conserving stocks of Trochus niloticus and other invertebrates, and investigated the reproductive biology and impacts of traditional gonad harvesting on Holothuria leucospilota. There were four major habitat types (rubble/rock, sand/coral matrix, algal rim and sand) identified, the most extensive being rubble/rock (45%) and sand/coral matrix (35%). The degree of exposure to winds was found to correlate with the reef development and habitat distribution. The assemblage composition of each major habitat type differed significantly from every other habitat. The rubble/rock habitat had the greatest substratum heterogeneity and structural complexity, and the highest number of species and individuals. The overall abundance of the fauna was dominated by holothurians (68%) and echinoids (30%), while Trochus niloticus and Tridacna maxima accounted for the remaining 2% of the total invertebrate assemblage. Clear habitat partitioning was also found for adult and juvenile Trochus niloticus and Tridacna maxima. In the traditional fishery for Holothuria leucospilota, the mature gonads of males are harvested by making an incision in the body-wall of the animal, removing the gonads and then returning the animal to the reef to allow regeneration. Monthly collections of H. leucospilota were used to describe the reproductive biology of this species. Gametogenesis and spawning were synchronous between the sexes and spawning occurred annually during summer, when water temperature and photoperiod were at their highest. Although the incision in the body-wall and gonad removal had no impact on the survival of H.leucospilota in experimental cages, their body weight, and general sheltering and feeding behaviors were affected. Gonads took at least 41 days to start regenerating, suggesting a considerable delay in the spawning of fished individuals. In 1998, five Rarotongan communities re-introduced the traditional ra�ui system of resource management, prohibiting all fishing and gathering from their reefs. The performance of the Nikao ra�ui, which had been put in place to allow trochus stocks to increase, was investigated. Comparisons of macroinvertebrate assemblage composition and species density were made between three fishing treatments, i.e. fished areas adjacent to the ra�ui, within the ra�ui after two years of protection, and in the ra�ui after it had been lifted for three weeks to allow a commercial trochus harvest. Analysis of variance on the count data for the twelve most abundant species, and non-metric multi-dimensional scaling indicated that there were no differences in the microhabitat or the invertebrate assemblage composition between the three fishing treatments. However, there were significant differences between the rubble/rock and sand/coral matrix habitat types. The results on the effectiveness of the Nikao ra�ui are equivocal, due to the small sample size, and the variability between samples which was highlighted by the wide confidence intervals. This study highlights the importance of habitat to the macroinvertebrate fauna of the reef-top and the need for accurate habitat maps to increase the cost-effectiveness of future resource surveys, to provide information to management, and for the design of Marine Protected Areas. The mapping and survey methods must be reliable and repeatable in terms of the limitations of time, and the availability of expertise, funding and resources. The results provide important information for fisheries and conservation managers of Rarotonga and other Pacific Islands to better design rigorous sampling programmes for monitoring the status of reef-top resources, and for evaluating and planning Marine Protected Areas.
74

Confronting the challenges of tidal flat conservation spatial patterns and human impacts in a Marine Protected Area in southern NSW, Australia /

Winberg, Pia Carmen. January 2008 (has links)
Thesis (Ph.D.)--University of Wollongong, 2008. / Typescript. CD-ROM contains full thesis, appendix II database and abstract. Includes bibliographical references: p. 169-198.
75

Nearshore topographic fronts : their effect on larval settlement and dispersal at Sunset Bay, Oregon

McCulloch, Anita January 2001 (has links)
Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 57-64). Description: x, 64 leaves : ill. (some col.), maps ; 29 cm.
76

Fungos associados a invertebrados marinhos: isolamento, seleção e avaliação da produção de enzimas celulolíticas. / Fungi associated with marine invertebrates: isolation, selection and evaluation of production of cellulytic enzymes.

Carlos Henrique Domingues da Silva 13 August 2010 (has links)
A micologia marinha é uma ciência relativamente recente e pouco se conhece sobre a diversidade das suas comunidades. Assim, o isolamento, triagem e preservação de fungos derivados do mar podem levar à descoberta de novas tecnologias. O objetivo deste estudo foi conhecer a diversidade de fungos filamentosos derivados marinhos e selecionar isolados capazes de produzir enzimas celulolíticas. Para tanto, foram isolados seletivamente fungos filamentosos a partir de amostras de macro-organismos marinhos coletados em 2007 e 2008. Os resultados demonstraram uma ampla diversidade de fungos potencialmente celulolíticos, pertencentes ao filo Basidiomycota e Ascomycota. Nos experimentos de produção de celulases, 17 apresentaram resultados satisfatórios de CMCase e FPase e foram selecionados para a avaliação da Celobiase. Os experimentos de cinética enzimática apresentaram os melhores resultados de produção de celulases em meio contendo farelo de trigo. O trabalho demonstra o potencial para aplicação biotecnológica dos fungos e estimula novos estudos com as celulases. / The Marine mycology is a relatively recent and little is known about the diversity of its communities. Thus, the isolation, separation and preservation of fungi derived from the sea can lead to the discovery of new technologies. The aim of this study was the diversity of filamentous fungi isolates derived marine and select capable of producing cellulolytic enzymes. It had been selectively isolated filamentous fungi from samples of marine macro-organisms collected in 2007 and 2008. The results showed a wide range of potential cellulolytic fungi, belonging to the phylum Basidiomycota and Ascomycota. In the experiments to produce cellulases, 17 had satisfactory results of CMCase and FPase and were selected for evaluation of cellobiase. The enzyme kinetics experiments showed better results for the production of cellulases in a medium containing wheat bran. The work demonstrates the potential for biotechnological application of fungi and stimulate further research with cellulases.
77

Toxicity and availability of copper and zinc to queen conch: implications for larval recruitment in the Florida Keys

Unknown Date (has links)
by Amber L. Garr. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web. / The presence of heavy metals and other pollutants is detrimental to marine ecosystems. The queen conch, once an important fisheries species in the Florida Keys, has not sufficiently recovered after a 25-year fishery closure. Research has shown high levels of copper and zinc in the gonads and digestive glands of adult conch found in the nearshore waters. Four sites relevant to queen conch larval recruitment were tested in 2010 for the presence of copper and zinc in the water, phytoplankton, sediment, and seagrass epiphytes over seven months. Both metals were detected in all sample types and no seasonal or geographical differences were detected. Surface water concentrations from the field were used to conduct acute and chronic toxicity tests on various ages of queen conch larvae and their phytoplankton food source. When zinc concentrations (0-40 (So(Bg/L) similar to those measured in situ were used, there was no significant impact on conch larval survival although some velar lobe de velopment was impaired. However, field concentrations of copper (0-15 (So(Bg/L), which often surpassed water quality standards, negatively impacted growth, survival, and development of the larvae. Chronic exposure to copper, through the water and food, disrupted the metamorphic success of competent larvae and decreased post-metamorphosis survival. Exposure to copper at later life stages increased mortality, suggesting that heavy metals have a negative effect on larval recruitment in localized areas of the Florida Keys. Structural equation modeling revealed that copper and zinc are moving through the systems differently and are best represented by two different models.
78

Marine biological invasions : the distributional ecology and interactions between native and introduced encrusting organisms

Hewitt, Chad LeRoy January 1993 (has links)
Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 283-301). Description: xxx, 301 leaves : ill. ; 29 cm.
79

The role of oxygen and other environmental variables on survivorship, abundance, and community structure of invertebrate meroplankton of Oregon nearshore coastal waters

Eerkes-Medrano, Dafne I. 06 January 2013 (has links)
The high productivity of Eastern Boundary Upwelling Ecosystems (EBUE), some of the most productive ecosystems in the globe, is attributed to the nutrient rich waters brought up through upwelling. Climate change scenarios for coastal upwelling systems, predict an intensification of coastal upwelling winds. Associated with intensification in upwelling are biogeochemical changes such as ocean hypoxia and ocean acidification. In recent years, the California Current System (CCS) has experienced the occurrence of nearshore hypoxia and the novel rise of anoxia. This has been attributed to changes in the intensity of upwelling wind stress. The effects of some of the more severe hypoxia and anoxia events in the CCS have been mass mortality of fish and benthic invertebrates. However, the impacts on zooplankton in this system are not known. Meroplankton, those organisms which have a planktonic stage for only part of their life cycle, are an important component of zooplankton communities. The larval stage of benthic invertebrates forms an important link between benthic adult communities and planktonic communities. Larvae serve to disperse individuals to new locations and to link populations. They are also food for fish and planktonic invertebrates. This important life stage can spend long periods in the plankton (from days to months) where environmental conditions can affect larval health, subsequent settlement and recruitment success, and juvenile health. This research assesses the role of hypoxia and larval survivorship, and the relationship between individual abundance and community structure of larvae to environmental factors in the field. In laboratory experiments (Chapter 2), a suite of 10 rocky intertidal invertebrate species from four phyla were exposed to low oxygen conditions representative of the nearshore environment of the Oregon coast. Results revealed a wide range in tolerances from species with little tolerance (e.g. the shore crab Hemigrapsus oregonensis) to species with high tolerance (e.g. the California mussel Mytilus californianus). The differential responses across larvae to chronic hypoxia and anoxia potentially could affect their recruitment success and consequently, the structure and species composition of intertidal communities. Field studies (Chapter 3 & 4) explore the relationship between environmental variables and larval abundance and community structure. Chapter 3 focuses on broad taxonomic groups, while Chapter 4 focuses on larval decapods in particular. Fine focus was devoted to decapod larvae, due to laboratory findings of heightened sensitivity to hypoxia of decapod crabs. A finding that is also supported in the literature. The goal of field studies was to identify the environmental parameters that structure meroplankton and larval decapod communities and identify which of these parameters play a significant role in influencing larval abundance. A number of environmental variables contributed to meroplankton assemblage structure and larval decapod assemblage structure. These included distance from shore, depth, date, upwelling intensity, dissolved oxygen, and cumulative wind stress. Some of these factors occurred frequently in larval abundance models. In Chapter 3, individual abundance across broad taxonomic groups was most commonly explained by upwelling intensity while in Chapter 4, individual abundance of different decapod species was explained by cumulative wind stress, which is a proxy for upwelling intensity. The prominent role of upwelling related factors in explaining individual abundance is important considering climate change projections of an increased intensification of upwelling winds in EBUE. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Jan. 6, 2012 - Jan. 6, 2013
80

Valorisation de biocides d’invertébrés marins méditerranéens / Secondary metabolites from Mediterranean marine invertebrates

Sfecci, Estelle 04 June 2018 (has links)
Ces travaux de thèse portent sur l’étude chimique d’espèces marines échantillonnées en Méditerranée. Dans le cadre du projet VALBIM, co-financé par la région PACA et en étroite collaboration avec la société BioPreserv à Grasse mais également avec la Mycoteca Universitatis Taurinensis (MUT) de l’Université de Turin, nous avons isolé et caractérisé 21 molécules dont 14 se sont avérées nouvelles. L’étude de l’algue Caulerpa taxifolia a conduit à la caulerpényne et à quatre nouveaux dérivés de l’acide pyruvique sulfatés. Les travaux sur l’ascidie Polysyncraton sp. ont conduit aux bolascidines A-D, quatre nouveaux métabolites de type bolaamphiphiles dont il n’existe pas à notre connaissance d’équivalent naturel ou synthétique. La première étude chimique de l’éponge Hexadella racovitzai a conduit à deux dérivés de la bromotyrosine, la psammapline A et une nouvelle molécule, la 4-Osulfatocyclobispsammapline A. Par ailleurs, trois nouvelles crambescines C1, conjointement avec une crambescine A2 déjà répertoriée, ont été isolées de Crambe crambe. L’étude du champignon marin Stachybotrys chartarum, isolé de l’éponge Aplysina cavernicola, a conduit à la satratoxine H et à deux nouveau dérivé, la 2,3-dihydrosatratoxine H et l’épi-chartarutine G, ainsi qu’à trois dérivés stachybotrylactame déjà répertoriés dans la bibliographie. Les différents métabolites ont été évalués pour leurs propriétés antibactériennes et cytotoxiques. Ces travaux ont bénéficié de nouvelles approches analytiques (calculs des spectres de dichroïsme circulaire électroniques par TDDFT, réseaux moléculaires) permettant de renforcer l’intérêt des études liées à l’écologie chimique et à la recherche de nouvelles molécules bioactives potentiellement valorisables dans différents domaines. / This PhD work focuses on the chemical study of marine species sampled in the Mediterranean Sea. As part of the VALBIM project, cofinanced by the region PACA and in close collaboration with the SME BioPreserv in Grasse but also with the Mycoteca Universitatis Taurinensis (MUT) of the University of Turin, we have isolated and characterized 21 molecules in total.14 of them were never reported before. The study of the seaweed Caulerpa taxifolia led to caulerpenyne and four new sulphated pyruvic acid derivatives. The work on the ascidian Polysyncraton sp. led to bolascidins A-D, four new metabolites which belong to the bolaamphiphile family, which, to the best of our knowledge, have no natural or synthetic equivalent. The first chemical study of the sponge Hexadella racovitzai led to two bromotyrosine derivatives, psammapline A and a new molecule, 4-O-sulfatocyclobispsammapline A. In addition, three new C1 crambescins, together with one crambescine A2 already reported, have been isolated from Crambe crambe. For all isolated marine invertebrate metabolites, the producer(s) remain(s) to be explored. The study of the marine fungus Stachybotrys chartarum, isolated from the sponge Aplysina cavernicola, led to satratoxin H and three stachybotrylactam derivatives already reported in the literature, and to 2,3-dihydrosatratoxin H and epi-chartarutine G, two new natural products. The different metabolites were evaluated for their antibacterial and cytotoxic properties. This work benefited from new analytical approaches (calculations of electronic circular dichroïsm spectra by TDDFT, molecular networking) and reinforced the interest of studies related to chemical ecology and search for new bioactive molecules to be valorized in different areas.

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