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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.
1

Effects of algal structure on associated motile epifaunal communities

Hooper, Garnet James January 2002 (has links)
No description available.
2

Macroinvertebrate communities in alpine glacier-fed streams : the Taillon catchment in the French Pyrenees

Snook, Deborah Louise January 2000 (has links)
No description available.
3

The Benthic Invertebrate Community of Lakes Previously Impaired by MiningI-related Acidification Near Wawa, Ontario

St John, Margaretha Ann 14 July 2009 (has links)
Iron mining began in Wawa, Ontario in the late 1800s and ceased in 1998. The sintering process of iron pyrite produced sulfur dioxide which led to the acidification of nearby lakes. Benthic macroinvertebrate samples were collected from lakes along a gradient of historical impairment in Wawa to examine the extent to which the benthos of the lakes would separate along the historical impairment gradient. The results show that the lakes are not separated along a gradient of impairment, and acid-intolerant taxa were collected in previously acidified lakes. There was no ameliorative intervention to combat the historical acidification and the observed recovery of water chemistry and benthos is entirely due to natural ecosystem processes. The two sampling methods (littoral kick sampling using a D-net and Hester-Dendy substrates) used to sample the benthos in these lakes can lead to substantial differences in the taxa collected.
4

The Benthic Invertebrate Community of Lakes Previously Impaired by MiningI-related Acidification Near Wawa, Ontario

St John, Margaretha Ann 14 July 2009 (has links)
Iron mining began in Wawa, Ontario in the late 1800s and ceased in 1998. The sintering process of iron pyrite produced sulfur dioxide which led to the acidification of nearby lakes. Benthic macroinvertebrate samples were collected from lakes along a gradient of historical impairment in Wawa to examine the extent to which the benthos of the lakes would separate along the historical impairment gradient. The results show that the lakes are not separated along a gradient of impairment, and acid-intolerant taxa were collected in previously acidified lakes. There was no ameliorative intervention to combat the historical acidification and the observed recovery of water chemistry and benthos is entirely due to natural ecosystem processes. The two sampling methods (littoral kick sampling using a D-net and Hester-Dendy substrates) used to sample the benthos in these lakes can lead to substantial differences in the taxa collected.
5

The response of stream ecosystems to riparian buffer width and vegetative composition in exotic plantation forests

Eivers, Rebecca January 2006 (has links)
Riparian buffers along stream margins have been widely adopted as a management strategy to mitigate the adverse effects of plantation forestry on stream ecosystems. However, the efficacy of these riparian buffers can be jeopardised by variations in width, length, and vegetation which can range from native and exotic scrub (including bracken, gorse, broom and blackberry) to remnant beech forest. This thesis investigates the influence of riparian vegetation age and composition, on stream ecosystems within exotic pine plantations. Initially, a survey of 50 streams within pine forests of various ages and riparian composition was conducted at sites from mid-Canterbury to Hanmer Springs over the summer of 2004-2005. Additionally, terrestrial subsidies were compared between young pine, mature pine and indigenous forest streams to ascertain differences or similarities between vegetation types. A range of physico-chemical and biological characteristics were recorded, while vegetative age and composition with catchment, riparian buffer and reach scales were determined using GIS. Forestry activities were found to vary temporarily and tended to adversely impact upon streams where riparian buffers were narrow and lacked indigenous vegetation. Stream instability and sedimentation were consistently higher in catchments lacking indigenous riparian vegetation, and more markedly so in recently harvested catchments compared with more mature forests. Streams dominated by pine forests had finer substrates with higher water temperatures and levels of turbidity, while those dominated by indigenous forest had coarser substrates, higher flows and dissolved oxygen levels, and less in-stream debris. Benthic community composition was similar among sites, although taxonomic richness, EPT diversity, and invertebrate abundances were enhanced by indigenous riparian vegetation.
6

Responses of aquatic invertebrate assemblages to an iron treatment aimed at reducing internal phosphorus loading

Wilson, Lindsey R Unknown Date
No description available.
7

Spatial pattern and community assembly: does the configuration of stream networks influence their community structure?

Campbell, Rebecca Elisabeth January 2011 (has links)
Dendritic stream networks are inherently spatially and hierarchically structured, but the effects of this structure on stream communities are largely unknown. My aim was to investigate spatial patterns in stream networks using extensive spatial sampling of both adult and benthic macroinvertebrates in four stream networks on the West Coast of the South Island, New Zealand. Using spatial modelling and analyses, I answered questions about appropriate spatial measurements to capture ecological processes in stream networks, metacommunity processes at different scales in space and time, and how local and regional processes interact to structure metacommunities in stream networks. Spatial eigenfunction analyses showed that distance measures that explained most variance in stream macroinvertebrate communities were stream distance and weighted stream distance measures. They performed better than Euclidean distance to measure spatial structure that is ecologically relevant to stream network communities. The spatial pattern of benthic stream macroinvertebrates was stable over time, whereas community composition changed significantly, as shown by space-time interactions modelled by MANOVA-like redundancy analysis. Thus, spatial processes structuring stream metacommunities remained constant, in agreement with neutral model predictions. Network-scale properties, particularly flood disturbances, influenced the relative importance of spatial and environmental variation in stream network metacommunities. Additionally, quantile regression indicated that three key variables, habitat size, isolation and local habitat conditions, jointly limited community structure in stream networks, providing empirical support for both island biogeography and metacommunity theories. My study indicated that spatial structuring has an important influence on stream macroinvertebrate communities. The results contribute to broader ecological theory and understanding of community assembly by relating empirical results to theoretical predictions. In particular, they advance understanding of spatial processes in stream networks. The research also highlights a number of new methods, which were successfully applied to stream systems to elucidate complex spatial patterns.
8

The response of stream ecosystems to riparian buffer width and vegetative composition in exotic plantation forests

Eivers, Rebecca January 2006 (has links)
Riparian buffers along stream margins have been widely adopted as a management strategy to mitigate the adverse effects of plantation forestry on stream ecosystems. However, the efficacy of these riparian buffers can be jeopardised by variations in width, length, and vegetation which can range from native and exotic scrub (including bracken, gorse, broom and blackberry) to remnant beech forest. This thesis investigates the influence of riparian vegetation age and composition, on stream ecosystems within exotic pine plantations. Initially, a survey of 50 streams within pine forests of various ages and riparian composition was conducted at sites from mid-Canterbury to Hanmer Springs over the summer of 2004-2005. Additionally, terrestrial subsidies were compared between young pine, mature pine and indigenous forest streams to ascertain differences or similarities between vegetation types. A range of physico-chemical and biological characteristics were recorded, while vegetative age and composition with catchment, riparian buffer and reach scales were determined using GIS. Forestry activities were found to vary temporarily and tended to adversely impact upon streams where riparian buffers were narrow and lacked indigenous vegetation. Stream instability and sedimentation were consistently higher in catchments lacking indigenous riparian vegetation, and more markedly so in recently harvested catchments compared with more mature forests. Streams dominated by pine forests had finer substrates with higher water temperatures and levels of turbidity, while those dominated by indigenous forest had coarser substrates, higher flows and dissolved oxygen levels, and less in-stream debris. Benthic community composition was similar among sites, although taxonomic richness, EPT diversity, and invertebrate abundances were enhanced by indigenous riparian vegetation.
9

Palaeoecology of the late Permian mass extinction and subsequent recovery

Foster, William J. January 2015 (has links)
Climate warming during the latest Permian is associated with the most severe mass extinction event of the Phanerozoic, and the expansion of hypoxic and anoxic conditions into shallow shelf settings. Our understanding of the magnitude, pattern and duration of the extinction event and subsequent recovery remains equivocal. Evidence suggests that the action of waves provided an oxygenated refuge, i.e. ‘habitable zone’, above wave base that may be limited to high latitudes, in association with a faster pace of recovery. In addition, advanced recovery faunas have been documented from the Induan and there is evidence from the pelagic realm that further biotic crises may have delayed the recovery of benthic organisms coinciding with large carbon isotope perturbations at the Lower Triassic sub-stage boundaries. To test these hypotheses, novel palaeoecological data was collected from localities in Hungary, northern Italy, and Svalbard. To understand better the ecological impact of the extinction, a database of all known benthic marine invertebrates from the Permian and Triassic periods was created, with each taxon assigned to a functional group based on their inferred lifestyle. This study found that the skeletal and ichnofaunal assemblages consistent with advanced ecological recovery are limited to settings aerated by wave activity, which supports the habitable zone hypothesis. In the western Palaeotethyan sections it was found that the proximal end of the ‘habitable zone’ was limited by persistent environmental stress attributed to increased runoff that resulted in large salinity fluctuations, increased sedimentation rates and eutrophication creating an environment only favourable for opportunistic taxa. In the Tirolites carniolicus Zone, however, the ‘habitable zone’ expands into more proximal and offshore settings. This is associated with climate cooling in the late Spathian. The data also demonstrate that despite the taxonomic severity of the extinction, only one mode of life went extinct and only one subsequently evolved in the aftermath. Functional diversity was, however, reduced in particular regions and environmental settings, and recovery varied spatially and temporally. In western Palaeotethys, benthic communities record evidence for biotic crises, such as reduced tiering in the Smithian, associated with Early Triassic carbon isotope excursions, but, until the Spathian there was no significant change in the composition of the benthic faunas.
10

O fenômeno da \"decoada\" no Pantanal do rio Paraguai, Corumbá/MS: alterações dos parâmetros limnológicos e efeitos sobre os macroinvertebrados bentônicos / The \'decoada\' phenomenon in Pantanal of Paraguai river, Corumbá/MS, Brazil: changes in limnological parameters and effects on benthic macroinvertebrates

Andrade, Maria Helena da Silva 02 June 2011 (has links)
Este trabalho teve como objetivo investigar a hipótese de que a decoada (alteração dos parâmetros físicos e químicos da água) é um fenômeno natural importante na estruturação da comunidade de invertebrados bentônicos do Pantanal do rio Paraguai, bem como a caracterizar a comunidade de macroinvertebrados bentônicos quanto à composição, abundância de organismos e riqueza em função das alterações ambientais provocadas pela decoada. Além disso, pretendeu-se contribuir para o conhecimento da biota do pantanal de Mato Grosso do Sul com o intuito de subsidiar ações de prevenção e/ou mitigação de possíveis impactos ambientais. Os ambientes escolhidos foram dois corpos de água adjacentes ao rio Paraguai, sendo um com características lênticas (Baía Tuiuiú) e outro, semi-lóticas (Bracinho), Corumbá/MS, ambos sob o efeito do pulso de inundação. O capítulo um realizou uma caracterização limnológica dos dois corpos de água ao longo de um ciclo hidrológico, enfatizando as alterações provocadas pela decoada, por ocasião da subida das águas. O capítulo 2 objetivou estudar a composição e a distribuição da fauna de Chironomidae relacionando-as com as alterações limnológicas ao longo de um ciclo hidrológico (abril/2008 a fevereiro/2009), enfatizando a influência da decoada. O capítulo 3 pretendeu conhecer a composição de Oligochaeta, considerando as relações com fatores abióticos, no intuito de contribuir para o entendimento do fenômeno da decoada bem como subsidiar posteriores trabalhos e ações relacionados à gestão da planície pantaneira, objetivando sua manutenção e conservação. A decoada é um evento que potencializa a desestruturação do ambiente, agindo significativamente sobre as populações de invertebrados bentônicos. O fato de não ter sido encontrado nenhum organismo vivo durante a ocorrência do fenômeno destaca a sua importância enquanto fator ecológico essencial na dinâmica das populações biológicas dos ecossistemas pantaneiros. / This study aimed to investigate the hypothesis that the decoada(change in physical and chemical parameters of water) is an important natural phenomenon in the community structure of benthic invertebrates in the Pantanal of the Paraguay River, and to characterize the benthic macroinvertebrate community regarding the composition, richness and abundance of organisms as a function of environmental changes caused by the \'decoada\'. In addition, soughted to contribute to the knowledge of the biota of wetland of Mato Grosso do Sul in order to support programs to prevent and / or mitigate potential environmental impacts. The areas chosen were two bodies of water adjacent to the Paraguay River, one with lentic feature (Tuiuiú Bay) and another, semi-lotic (\'Bracinho\'), Corumbá / MS, both of them suffering the effect of pulse flood. The chapter 1 conducted a limnological characterization of the two water bodies along a hydrological cycle, emphasizing the changes caused by the \'decoada\', when the water level rises. Chapter 2 aimed to study the composition and distribution of Chironomidae fauna relating them to limnologicals changes over a hydrological cycle (the april/2008 to february/2009), emphasizing the influence of the decoada. Chapter 3 intended know the composition of Oligochaeta, considering the relationships with environmental factors in order to contribute to the understanding of the phenomenon of \'decoada\' and support further work and actions related to the management of the Pantanal, aiming to maintain the ecosystem and related services. The decoada is an event that enhances the disintegration of the environment, acting significantly on populations of benthic invertebrates. The fact that no organism had been found alive during the occurrence of the phenomenon underscores its importance as an essential ecological factor in the dynamics of biological populations of wetland ecosystems.

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