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FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / Este trabalho desenvolveu uma metodologia, com base na aplicaÃÃo da teoria fuzzy, em modelos de transporte de poluentes, para estudar o risco fuzzy de contaminaÃÃo, na concessÃo de outorga de lanÃamentos de efluentes em rios. Para isso, as equaÃÃes diferenciais do modelo de transporte sÃo transformadas em equaÃÃes diferenciais fuzzys, de modo que o campo de concentraÃÃes representado pelo modelo matemÃtico seja transformado em campos de funÃÃes de pertinÃncias de concentraÃÃes. O estudo se utiliza de parÃmetros definidos na lei para estabelecer a classe do rio e, assim, calcular, para cada tipo de lanÃamento, o risco de contaminaÃÃo e a capacidade de assimilaÃÃo do mesmo. Para a soluÃÃo do modelo matemÃtico foi usado o mÃtodo das diferenÃas finitas, com esquema implÃcito para o equacionamento das equaÃÃes das diferenÃas. Para a realizaÃÃo das simulaÃÃes foi desenvolvido um programa computacional, em linguagem FORTRAN que deu suporte na obtenÃÃo dos resultados para os mais diversos cenÃrios propostos. Os resultados mostraram que a teoria fuzzy pode se tornar uma alternativa segura no auxilio do controle de poluiÃÃo dos rios em geral, fornecendo, assim, fundamentos para a gestÃo dos recursos hÃdricos / This research developed a methodology, based on application of fuzzy theory in the pollutant transport models, to study the fuzzy risk of contamination, in awarding grants for discharge of effluents into rivers. In such way, the differential equations of the transport model are transformed into fuzzy differential equations, so that, the field of concentrations, represented by the mathematical model is transformed into fields of concentration membership functions. The study makes use of parameters defined in the law to establish the class of the river, so that, it calculates, for each type of release, the risk and its assimilative capacity of the river to receive effluents. For the solution of the mathematical model the finite difference method was used, with implicit scheme on order to get the difference equation. For the accomplishment of the simulations a computational program, in FORTRAN language, was developed, that gave support in the obtaining of the results for the most several proposed sceneries. The results have shown that the fuzzy theory can become a safe alternative to help control pollution of rivers in general, providing, in such way, subsidies for resources management

<p> A study of two shallow fringing reefs off the coast of Zanzibar Island was conducted. The study site was Grave Island, 1 km off the shore of Zanzibar town. The comparison site was Chumbe Island, 10 km upcurrent of the town, adjacent a less densely inhabitated coast. The major anthropogenic stress on these reefs could be considered nutrient loading from sewage discharge.</p> <p> Studies of the sea urchin Diadema setosum, indicated mean densities at Grave Island of 6.4 urchins/m^2 and 1.2 urchins/m^2 at Chumbe Island. Urchin densities comparable to those at Grave Island have been related to overfishing and reduced coral recruitment. Coral associate densities were also considered with a mean density of 87/m^2 at Grave Island and 31/m^2 at Chumbe Island. High coral associate densities have been linked to structurally and physiologically weakened coral.</p> <p> Transect studies were conducted and suggested there were significantly reduced coral cover and reduced amounts of live coral at Grave Island (cf Chumbe Island). As well, coral species diversity was significantly lower at Grave Island than at Chumbe Island. Lowered species diversity suggests an unstable community structure, and reduced coral cover may indicate a faltering reef.</p> <p> Stable Isotope studies were conducted on tissue samples from both sites. They showed no significant difference.</p> <p> This study reflects the poor health of Grave Island. The high abundance of urchins and filter feeders, combined with reduced coral cover and diversity, suggest high nutrient loading on these reefs. The high abundance of urchins and associates also suggest coral mortality will be high and recruitment low. If these trends continue, it is unlikely the reef at Grave Island will be able to survive.</p> / Thesis / Bachelor of Science (BSc)