Thesis (M.Sc.). / Written for the Dept. of Bioresource Engineering. Title from title page of PDF (viewed 2008/05/14). Includes bibliographical references.

Thesis (doctoral)--Wageningen University and the Academic Board of the UNESCO-IHE Institute for Water Education, 2006. / "Propositions" ([1] leaf) inserted. Vita. Includes bibliographical references.

Thesis (doctoral)--Wageningen University and the Academic Board of the UNESCO-IHE Institute for Water Education, 2006. / "Propositions" ([1] leaf) inserted. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1976. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 358-372).

Thesis (Ph.D.)--Baylor University, 2006. / Includes bibliographical references (p. 141-155).

In recognition of the widespread deterioration of the natural environment, and the continual emergence of sudden catastrophic environmental changes resulting from complex interactions of theretofore apparently disparate phenomena, this research presents a complex systems approach to the modelling of such environmental catastrophes. Recognizing contemporary views of complexity and evolution, this research presents a dynamic complex systems model which displays emergent characteristics which can be directly related to the modelled phenomena - linking acid rain and eutrophication - and the study region, the Rutland Water catchment. This is achieved through the definition of a catastrophe indicator which indicates both the proximity and magnitude of catastrophe arising from the non-linear and discontinuous acid-phosphorus relationship within the soil domain which lies at the heart of this Chemical Time Bomb phenomenon. This facilitates assessment of the vulnerability of the Rutland Water catchment to potential propagation of this CTB given continued acidification and phosphate accumulation. The main contributions of this research may thus be found in the following areas: Development of a dynamic complex systems model - transferable to alternative catchments due to the minimal data requirements and its generic representation - which may be used to describe non-point sources of phosphates as part of assessments of potential eutrophication, overcoming such limitations found in existing models. * Definition of a catastrophe indicator( Re)- which highlights both the proximity and magnitude of catastrophe describing a specific Chemical Time Bomb phenomenon whereby the soil suddenly changes from being a sink to a source of phosphates; long-term accumulations of phosphate in the soil being released as a consequence of soil acidification in the short-term. Presentation of a complex systems approach - hinged upon this concept of a catastrophe indicator - to the representation of non-linearities and discontinuities between heretofore apparently disparate phenomena which are 'competing for a common resource.

Made available in DSpace on 2014-06-11T19:30:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-16Bitstream added on 2014-06-13T18:40:12Z : No. of bitstreams: 1 zaganini_rl_me_botib.pdf: 5235200 bytes, checksum: 888863188c5f56542941bd95698e9ef1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho teve como objetivo estudar o regime alimentar de Oreochromis niloticus (Linnaeus, 1758) e Tilapia rendalli (Boulenger, 1897) na represa de Barra Bonita, Médio Rio Tietê, SP, utilizando-se duas abordagens: i) caracterização das dietas de O. niloticus e T. rendalli, e possíveis relações com a aceleração do processo de eutrofização e ii) variação ontogenética e padrões sazonais do regime alimentar dessas espécies. As amostragens foram realizadas mensalmente (março de 2007 a fevereiro de 2008) no município de Anhembi (SP). Os peixes foram obtidos do desembarque da pesca artesanal e paralelamente, foi realizada a pesca experimental com uso de tarrafas de malha 3 cm entrenós não adjacentes, visando amostrar exemplares de pequeno porte. Foram coletados ainda fatores abióticos da água (oxigênio dissolvido, temperatura da água, pH e condutividade elétrica, transparência da água e clorofila-a total). Outros dados como cota altimétrica da represa e pluviosidade mensal foram compilados da concessionária AES – Tietê. De todos os exemplares de peixes foram obtidos dados biométricos (comprimento padrão e peso total). Os estômagos foram transferidos para frascos etiquetados contendo solução de formaldeído 10%. O conteúdo estomacal foi analisado pelos métodos de freqüência de ocorrência e volumétrico, combinados no Índice alimentar. Para avaliar as possíveis variações ontogenéticas e sazonais, foram analisadas as dietas dos exemplares de cada espécie agrupados em classes de tamanho e por estação seca e chuvosa. Na dieta das duas espécies foram observados 26 itens alimentares agrupados em sete categorias (fragmentos vegetais, algas, detritos, peixes, microcrustáceos, macroinvertebrados e insetos aquáticos). A espécie O. niloticus, consumiu 24 itens, e foi considerada detritívora, enquanto que T. rendalli, consumiu... / The present work aimed to study the food habits of niloticus (Linnaeus, 1758) and Tilapia rendalli (Boulenger, 1897) in the Barra Bonita reservoir, São Paulo State, by using two approaches: i) characterization of O. niloticus e T. rendalli feeding habits and to find any possible relationship with the reservoir´s eutrophication process and ii) analyze seasonal and ontogenetic variation with regard to the diet of these species. Samples were collected monthly, from March 2007 to February 2008, in Anhembi, São Paulo State. The fishes were obtained of artisanal fish landing and fishing was done using casting net (3cm between-knot mesh size), to get small individuals. Some physico-chemical variables of water samples were collected (dissolved oxygen, water temperature, pH and electric conductivity, water transparency and chlorophyll a). Another data such as reservoir altimeter quota and monthly rainfall were gathered from the AES – Tietê. Biometric data (standard length and total weight) were obtained from all individuals. The stomachs were transferred to labeled bottle with formaldehyde 10%. The stomach content was analyzed by frequency of occurrence and volume, combined on the food index. To evaluate possible seasonal and ontogenetic variation, it was analyzed the diet of each species grouped in size class and by dry and wet season. In the diet of both species were observed 26 different food items grouped into seven categories: vegetables fragments, algae, detritus, fishes, micro crustaceans, macro invertebrates and aquatic insects). O. niloticus consumed 24 items, and was considered detritivorous, whereas T. rendalli consumed 23 items, and was considered omnivorous, because it used animal and vegetal resources without dominance of any no category. With regard to a possible relationship with the reservoir´s eutrophication process, this could be mitigated by species, given that the feed... (Complete abstract click electronic access below)

Hypolimnetic anoxia can result in higher internal phosphorus (P) loads from the sediments to the water column, thereby increasing nutrient availability, making preventing anoxia a major goal for lake managers to improve water quality. Side-stream saturation (SSS), a type of hypolimnetic oxygenation system, has been developed to maintain oxygenated conditions at the sediments by withdrawing oxygen-depleted water from the hypolimnion to an on-site facility and injecting it with oxygen under high pressure before returning it to the hypolimnion. While this technique has been studied in select water bodies, to date it has not been successfully deployed in a shallow lake. This study investigated the effects of an SSS system deployed at Falling Creek Reservoir, a shallow drinking water reservoir located in Vinton, Virginia, USA. Specifically, we examined the effects of the SSS system on several chemical, physical, and biological response variables to ascertain the short-term impacts of hypolimnetic oxygenation on reservoir water quality. We found that the SSS system was successful in increasing dissolved oxygen concentrations in the reservoir hypolimnion without weakening stratification, warming the sediments, or increasing turbidity; however, we were unable to detect any short-term effects of SSS operation on P concentrations, P loading, pH, chlorophyll a, or algal density. Interestingly, we also observed an increase in oxygen demand in response to SSS operation, which must be taken into account when deploying oxygenation systems in the future. Continued monitoring is necessary to more completely assess the long-term impacts of SSS operation on water quality at Falling Creek Reservoir. / Master of Science

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