Thesis (Ph.D.)--University of Hong Kong, 2003. / Includes bibliographical references (leaves 187-201) Also available in print.

Nas últimas duas décadas, esforços têm sido direcionados para se compreender o papel ecológico de medusas de Scyphozoa, devido a aumentos populacionais e intensos blooms ao redor do mundo. Apesar de medusas de Rhizostomeae, causarem os mais intensos blooms recentemente reportados, quase nada se conhece sobre seu papel ecológico. O objetivo desta tese foi descrever as bases morfológicas e funcionais da alimentação de Lychnorhiza lucerna Haeckel, 1880 (Rhizostomeae), para se compreender seu papel predatório e suas interações tróficas. O projeto investigou (i) o desenvolvimento inicial de medusas de L. lucerna, com foco nos mecanismos locomotor-alimentar (ii) a dieta, seletividade alimentar e os potenciais impactos predatórios da espécie e (iii) a estrutura trófica de um sistema estuarino conservado, para compreender o papel ecológico e relações tróficas entre organismos gelatinosos e peixes. A abordagem metodológica envolveu: i- métodos videográficos em alta velocidade, para a quantificação de parâmetros biomecânicos em animais de diferentes estágios de desenvolvimento; ii- coletas de animais e plâncton na superfície da água para a quantificação de conteúdos estomacais no estudo de dieta, seletividade e taxas alimentares ao longo do litoral do estado São Paulo e Paraná; e iii- a análise de isótopos estáveis (&delta;13C e &delta;15N) de tecidos de consumidores (mesozooplâncton, gelatinoso, outros invertebrados e peixes) do estuário de Cananéia, São Paulo. A ontogenia inicial de éfiras de L. lucerna envolve mudanças na umbrela e o desenvolvimento dos braços orais filtradores. No ambiente fluido ao redor das éfiras (6 mm de diâmetro umbrelar) as forças de viscosidade são relativamente importantes (Re<100). Por isso, os fluxos gerados pelas pulsações umbrelares rapidamente se dissipam, antes de atingirem as superfícies distais nos braços orais. O mecanismo de transporte de presas através das pulsações da umbrela só foi observado a partir do aumento ontogenético da força da pulsação (>10 mm) proporcionando um ambiente dominado pelas forças inerciais (Re>300). Em adultos, as pulsações umbrelares produzem vórtices que escoam fluidos para os braços orais, os quais retêm partículas através de um mecanismo aderente e filtrador. Medusas de Rhizostomeae possuem as pulsações de umbrela mais robustas entre as cifomedusas, porém as velocidades máximas dos vórtices (&sim;10 cm*s&minus;1) de L. lucerna (<7 cm) são de 3 a 5 vezes menores que a velocidade de escape dos copépodes calanóides. Embora essa diferença possa sugerir sucesso aos copépodes para escapar, tanto as sequências de vídeo, quanto os conteúdos estomacais demonstraram que essas presas podem ser capturadas e ingeridas em quantidades similares às suas densidades no ambiente. Copépodes podem falhar na detecção do predador, sendo transportados contra as estruturas de captura de presas, mesmo se tiverem velocidades que permitiriam sua fuga. A interação de presas com os vórtices das pulsações é complexa e presas podem saltar em ângulos que resultam em captura pelos braços orais. Através da análise de conteúdo estomacal foram encontrados 43 taxa compondo a dieta de L. lucerna, dos quais, copépodes representaram &sim;80% da composição numérica. A medusa é um predador generalista, com a dieta predominantemente similar à disponibilidade de mesozooplâncton. A capacidade de L. lucerna capturar os evasivos copépodes calanóides (Paracalanus spp. e Acartia spp.) aumenta com seu tamanho, devido ao aumento na força de suas correntes alimentares. Taxas alimentares da medusa variaram de 110 a 102871 copépodes ingeridos medusa &minus;1 dia&minus;1. Com essas taxas, estimou-se que uma agregação de L. lucerna reportada no norte da Argentina (14 indiv. 100 m&minus;3) poderia ingerir de 6 a 12% do estoque de copépodes dia&minus;1, demonstrando o potencial impacto predatório de blooms da espécie. Aumentos populacionais de L. lucerna certamente seriam deletérios para o recrutamento de diversas espécies de peixes, que habitam águas costeiras estuarinas quando juvenis. A análise de isótopos estáveis revelou que o nicho isotópico ocupado por L. lucerna e o de outros gelatinosos zooplanctívoros, se sobrepõe aos nichos de peixes e outros consumidores de hábito alimentar semelhante. Pouco se sabe sobre dinâmicas compensatórias em ecossistemas costeiros subtropicais. No entanto, devido a sua biomassa, hábitos alimentares generalistas e seu impacto predatório, L. lucerna é um forte candidato a repor estoques de peixes em declínio, de nicho trófico similar. Atualmente não existem indícios de que populações de L. lucerna estejam aumentando. As informações aqui apresentadas representam um avanço no conhecimento da biologia alimentar da espécie e sobre suas interações, que são essenciais para se conhecer as consequências de seus blooms e de possíveis aumentos populacionais. No entanto, muitas outras informações abordando outros aspectos (e.g. reprodutivos) e em escala populacional (e.g. biomassa, sazonalidade) ainda são necessários para uma compreensão mais completa sobre o papel da espécie no ecossistema. / During the past three decades, efforts have been focused in order to understand the ecological role of scyphomedusae, due to population increases around the world. Despite Rhizostomeae medusae cause the most intense recently reported blooms, almost nothing is known about their feeding mechanisms, their trophic impacts and their ecological role. The goal of this thesis was to describe the morphological and functional bases of feeding in Lychnorhiza lucerna Haeckel, 1880 (Rhizostomeae), in order to understand its predatory role and trophic interactions. The project investigated: i- the early development of L. lucerna, focusing on swimming-feeding mechanisms; ii- the diet, prey selectivity, and the potential predatory impact of this species, and (iii) the trophic structure of a relatively pristine ecosystem, in order to understand trophic relationships between gelatinous zooplankton species and fish. The methodological approach included: i- high-speed videography for quantification of biomechanical parameters of swimming medusae at a range of developmental stages; ii- samplings of animals and plankton in surface waters for quantification of gut contents, prey selectivity and feeding rates along the coast of São Paulo and Paraná states; and ii- stable isotope analyses (&delta;13C and &delta;15N) in tissues of consumers (mesozooplankton, gelatinous, other invertebrates and fish) in the estuary of Cananéia, São Paulo. The early ontogeny of ephyrae involves changes in bell and development of filter-feeding oral arms. In the fluid environment around the ephyrae (<6mm bell diameter) the viscous forces are relatively important (Re <100). Therefore, the flows generated by bell pulsations quickly dissipate before reaching the distal surfaces of the oral arms. The transport mechanism via bell pulsations was not observed until ontogenetic increase in the strength of the pulsations (>10mm) providing an environment dominated by inertial forces (Re> 300). In adults bell pulsations produce vortices that induce flows through oral arms, which retain particles by sticking and sieving mechanisms. Rhizostomeae jellyfish have the most robust bell pulsations among scyphomedusae, but maximum velocities of the vortices (&sim;10cm s-1) of L. lucerna (<70mm) are still 3 to 5 times slower than escape velocity of calanoid copepods. Although this difference may suggest success for copepods to escape, both video sequences, and gut contents revealed that these prey can be captured and eaten at similar proportions as their field density. Copepods may fail to detect the predator, being transported against prey capture structures, even if they perform velocities that usually allow escaping. The interaction of prey with vortices is complex and prey may jump at angles that result in captures by oral arms. Through the analysis of gut contents (N=40) 43 taxa were found composing the diet of L. lucerna, of which, copepods comprised &sim;80% of numerical abundance. This medusa is a generalist predator, since its diet was mostly similar to field mesozooplankton availability. Its ability to capture evasive calanoid copepods (Paracalanus spp. and Acartia spp.) increases with medusa size, as a consequence of increasingly stronger feeding currents. Feeding rates ranged from 110 to 102871 copepods eaten medusa&minus;1 day&minus;1. At these rates, it was estimated that an aggregation of L. lucerna reported in northern Argentina (14 ind. 100 m&minus;3) could consume 6-12% of the copepods standing stock day&minus;1, demonstrating the potential predatory impact of the species\' blooms. Population increases of L. lucerna would certainly be detrimental to the recruitment of many fishes that inhabit estuarine coastal waters when juveniles. Stable isotope analyses revealed that the isotopic niche occupied by L. lucerna and by other gelatinous zooplanktivores, overlaps with niches of fishes, and other consumers of similar feeding habits. Little is known about compensatory dynamics in subtropical coastal ecosystems. However, due to its biomass, generalist feeding habits, and predatory impact, L. lucerna is a strong contender to replace depleted fish stocks of similar trophic niche. Currently there is no evidence that L. lucerna populations are increasing. The information presented here represents an advance in the knowledge of the species, its interactions, which are key in order to understand the consequences of its blooms and of possible population increases. However, many other information addressing other aspects (e.g. reproduction) and at population level (e.g. seasonality, biomass) are needed for a more complete understanding of the species role in the ecosystem.

Thesis (M.S.)--Indiana University, 2007. / Title from screen (viewed on Apr. 30, 2007) Department of Geography, Indiana University-Purdue University Indianapolis (IUPUI) Includes vita. Includes bibliographical references (leaves 122-125)

Nas últimas duas décadas, esforços têm sido direcionados para se compreender o papel ecológico de medusas de Scyphozoa, devido a aumentos populacionais e intensos blooms ao redor do mundo. Apesar de medusas de Rhizostomeae, causarem os mais intensos blooms recentemente reportados, quase nada se conhece sobre seu papel ecológico. O objetivo desta tese foi descrever as bases morfológicas e funcionais da alimentação de Lychnorhiza lucerna Haeckel, 1880 (Rhizostomeae), para se compreender seu papel predatório e suas interações tróficas. O projeto investigou (i) o desenvolvimento inicial de medusas de L. lucerna, com foco nos mecanismos locomotor-alimentar (ii) a dieta, seletividade alimentar e os potenciais impactos predatórios da espécie e (iii) a estrutura trófica de um sistema estuarino conservado, para compreender o papel ecológico e relações tróficas entre organismos gelatinosos e peixes. A abordagem metodológica envolveu: i- métodos videográficos em alta velocidade, para a quantificação de parâmetros biomecânicos em animais de diferentes estágios de desenvolvimento; ii- coletas de animais e plâncton na superfície da água para a quantificação de conteúdos estomacais no estudo de dieta, seletividade e taxas alimentares ao longo do litoral do estado São Paulo e Paraná; e iii- a análise de isótopos estáveis (&delta;13C e &delta;15N) de tecidos de consumidores (mesozooplâncton, gelatinoso, outros invertebrados e peixes) do estuário de Cananéia, São Paulo. A ontogenia inicial de éfiras de L. lucerna envolve mudanças na umbrela e o desenvolvimento dos braços orais filtradores. No ambiente fluido ao redor das éfiras (6 mm de diâmetro umbrelar) as forças de viscosidade são relativamente importantes (Re<100). Por isso, os fluxos gerados pelas pulsações umbrelares rapidamente se dissipam, antes de atingirem as superfícies distais nos braços orais. O mecanismo de transporte de presas através das pulsações da umbrela só foi observado a partir do aumento ontogenético da força da pulsação (>10 mm) proporcionando um ambiente dominado pelas forças inerciais (Re>300). Em adultos, as pulsações umbrelares produzem vórtices que escoam fluidos para os braços orais, os quais retêm partículas através de um mecanismo aderente e filtrador. Medusas de Rhizostomeae possuem as pulsações de umbrela mais robustas entre as cifomedusas, porém as velocidades máximas dos vórtices (&sim;10 cm*s&minus;1) de L. lucerna (<7 cm) são de 3 a 5 vezes menores que a velocidade de escape dos copépodes calanóides. Embora essa diferença possa sugerir sucesso aos copépodes para escapar, tanto as sequências de vídeo, quanto os conteúdos estomacais demonstraram que essas presas podem ser capturadas e ingeridas em quantidades similares às suas densidades no ambiente. Copépodes podem falhar na detecção do predador, sendo transportados contra as estruturas de captura de presas, mesmo se tiverem velocidades que permitiriam sua fuga. A interação de presas com os vórtices das pulsações é complexa e presas podem saltar em ângulos que resultam em captura pelos braços orais. Através da análise de conteúdo estomacal foram encontrados 43 taxa compondo a dieta de L. lucerna, dos quais, copépodes representaram &sim;80% da composição numérica. A medusa é um predador generalista, com a dieta predominantemente similar à disponibilidade de mesozooplâncton. A capacidade de L. lucerna capturar os evasivos copépodes calanóides (Paracalanus spp. e Acartia spp.) aumenta com seu tamanho, devido ao aumento na força de suas correntes alimentares. Taxas alimentares da medusa variaram de 110 a 102871 copépodes ingeridos medusa &minus;1 dia&minus;1. Com essas taxas, estimou-se que uma agregação de L. lucerna reportada no norte da Argentina (14 indiv. 100 m&minus;3) poderia ingerir de 6 a 12% do estoque de copépodes dia&minus;1, demonstrando o potencial impacto predatório de blooms da espécie. Aumentos populacionais de L. lucerna certamente seriam deletérios para o recrutamento de diversas espécies de peixes, que habitam águas costeiras estuarinas quando juvenis. A análise de isótopos estáveis revelou que o nicho isotópico ocupado por L. lucerna e o de outros gelatinosos zooplanctívoros, se sobrepõe aos nichos de peixes e outros consumidores de hábito alimentar semelhante. Pouco se sabe sobre dinâmicas compensatórias em ecossistemas costeiros subtropicais. No entanto, devido a sua biomassa, hábitos alimentares generalistas e seu impacto predatório, L. lucerna é um forte candidato a repor estoques de peixes em declínio, de nicho trófico similar. Atualmente não existem indícios de que populações de L. lucerna estejam aumentando. As informações aqui apresentadas representam um avanço no conhecimento da biologia alimentar da espécie e sobre suas interações, que são essenciais para se conhecer as consequências de seus blooms e de possíveis aumentos populacionais. No entanto, muitas outras informações abordando outros aspectos (e.g. reprodutivos) e em escala populacional (e.g. biomassa, sazonalidade) ainda são necessários para uma compreensão mais completa sobre o papel da espécie no ecossistema. / During the past three decades, efforts have been focused in order to understand the ecological role of scyphomedusae, due to population increases around the world. Despite Rhizostomeae medusae cause the most intense recently reported blooms, almost nothing is known about their feeding mechanisms, their trophic impacts and their ecological role. The goal of this thesis was to describe the morphological and functional bases of feeding in Lychnorhiza lucerna Haeckel, 1880 (Rhizostomeae), in order to understand its predatory role and trophic interactions. The project investigated: i- the early development of L. lucerna, focusing on swimming-feeding mechanisms; ii- the diet, prey selectivity, and the potential predatory impact of this species, and (iii) the trophic structure of a relatively pristine ecosystem, in order to understand trophic relationships between gelatinous zooplankton species and fish. The methodological approach included: i- high-speed videography for quantification of biomechanical parameters of swimming medusae at a range of developmental stages; ii- samplings of animals and plankton in surface waters for quantification of gut contents, prey selectivity and feeding rates along the coast of São Paulo and Paraná states; and ii- stable isotope analyses (&delta;13C and &delta;15N) in tissues of consumers (mesozooplankton, gelatinous, other invertebrates and fish) in the estuary of Cananéia, São Paulo. The early ontogeny of ephyrae involves changes in bell and development of filter-feeding oral arms. In the fluid environment around the ephyrae (<6mm bell diameter) the viscous forces are relatively important (Re <100). Therefore, the flows generated by bell pulsations quickly dissipate before reaching the distal surfaces of the oral arms. The transport mechanism via bell pulsations was not observed until ontogenetic increase in the strength of the pulsations (>10mm) providing an environment dominated by inertial forces (Re> 300). In adults bell pulsations produce vortices that induce flows through oral arms, which retain particles by sticking and sieving mechanisms. Rhizostomeae jellyfish have the most robust bell pulsations among scyphomedusae, but maximum velocities of the vortices (&sim;10cm s-1) of L. lucerna (<70mm) are still 3 to 5 times slower than escape velocity of calanoid copepods. Although this difference may suggest success for copepods to escape, both video sequences, and gut contents revealed that these prey can be captured and eaten at similar proportions as their field density. Copepods may fail to detect the predator, being transported against prey capture structures, even if they perform velocities that usually allow escaping. The interaction of prey with vortices is complex and prey may jump at angles that result in captures by oral arms. Through the analysis of gut contents (N=40) 43 taxa were found composing the diet of L. lucerna, of which, copepods comprised &sim;80% of numerical abundance. This medusa is a generalist predator, since its diet was mostly similar to field mesozooplankton availability. Its ability to capture evasive calanoid copepods (Paracalanus spp. and Acartia spp.) increases with medusa size, as a consequence of increasingly stronger feeding currents. Feeding rates ranged from 110 to 102871 copepods eaten medusa&minus;1 day&minus;1. At these rates, it was estimated that an aggregation of L. lucerna reported in northern Argentina (14 ind. 100 m&minus;3) could consume 6-12% of the copepods standing stock day&minus;1, demonstrating the potential predatory impact of the species\' blooms. Population increases of L. lucerna would certainly be detrimental to the recruitment of many fishes that inhabit estuarine coastal waters when juveniles. Stable isotope analyses revealed that the isotopic niche occupied by L. lucerna and by other gelatinous zooplanktivores, overlaps with niches of fishes, and other consumers of similar feeding habits. Little is known about compensatory dynamics in subtropical coastal ecosystems. However, due to its biomass, generalist feeding habits, and predatory impact, L. lucerna is a strong contender to replace depleted fish stocks of similar trophic niche. Currently there is no evidence that L. lucerna populations are increasing. The information presented here represents an advance in the knowledge of the species, its interactions, which are key in order to understand the consequences of its blooms and of possible population increases. However, many other information addressing other aspects (e.g. reproduction) and at population level (e.g. seasonality, biomass) are needed for a more complete understanding of the species role in the ecosystem.

No description available.

Abstract The transfer and teaching of programming and programming related skills has become, increasingly difficult on an undergraduate level over the past years. This is partially due to the number of programming languages available as well as access to readily available source code over the Web. Source code plagiarism is common practice amongst many undergraduate students. This practice has a detrimental effect on the presentation of specific content relating to introduction to programming courses. One of the problems identified in the research conducted is that turnaround time with relation to assessment and feedback, which are presented to the students, is a critical factor in the subsequent success rates of the subject. This paper investigates, utilizing a literature review, how plagiarism detection metrics and a framework for providing effective feedback to students and educators could be implemented to enhance the teaching and learning processes. The predominant technique used for detecting plagiarism is to evaluate how a piece of source code was constructed over time. By analyzing the students’ programming patterns, lectures can be adapted to address problem areas and react accordingly. The paper also provides an overview of current metrics used for plagiarism detection and suggests ways of improving the process by including enhanced techniques for the gathering of metrics over time as well as suggesting ways to use the metrics to aid learning on all cognitive levels. Some of the key considerations presented as part of this research include effective feedback mechanisms and real-time responses to plagiarism as well as contributing towards learning on different cognitive levels.

Thesis (degree (Master in Technology))--Cape Technikon, Cape Town,1996 / Red tides are a common feature of the southern Benguela upwelling system and are usually dominated by migratory flagellates and the ciliate Mesodinium rubrum. Seasonal blooms of dinoflagellates occur in response to seasonal upwelling and typically succeed diatom blooms. High biomass, multispecies red tides result from concentration by various physical forces and are characteristically found in warm, stratified, nutrient-depleted water overlying cold, nutrient-rich bottom water. The influence of turbulent mixing, light and the availability of nutrients on the migratory behaviour of red tide species was studied by means of both mesocosm and field studies. The mesocosm experiments were conducted in a 3m laboratory column in which a red tide community, collected from the field, was introduced above nutrient-rich bottom water. All the dominant species exhibited directed vertical migration, with ascent and descent starting before sunrise and before sunset respectively. Observations support the hypothesis that red tide organisms can sustain high concentrations in nitrogen depleted surface waters by growing at the expense of nitrate taken up during nocturnal descent. Vertical niche separation of different red tide species was evident both during the night and the day. Observations support the hypothesis that species are capable of coexisting within a red tide bloom. Division rates were determined from the frequency of paired nuclei and cells. C. furca recorded the highest growth rate (u = 0.24). The relatively low growth rates emphasise the importance of physical processes, as opposed to biological processes, in the formation of red tides within upwelling systems.

This dissertation investigate to determine the presence of biological nitrogen fixation in two reservoirs in the southwestern United States: Lake Arlington and Lake Ray Hubbard.

Thesis (M.A.)--York University, 2007. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 112-121). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38799

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 201-227).