Made available in DSpace on 2014-12-17T15:03:22Z (GMT). No. of bitstreams: 1 FaranciscoRSF_restricoes.pdf: 1206510 bytes, checksum: bdf6c5d3c8390b9e1ea63d1d4080d1ed (MD5) Previous issue date: 2008-12-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Eutrophication has been listed as one of the main problems of water pollution on a global level. In the Brazilian semi-arid areas this problem takes even greater proportions due to characteristical water scarcity of the region. It is extremely important to the predictive eutrophication models development and to the reservoirs management in the semi-arid region, studies that promotes understanding of the mechanisms responsible for the expansion and control of algae blooms, essential for improving the water quality of these environments. The present study had as its main aims, evaluate the temporal pattern of trophic state, considering the influence of nutrients (N and P) and the light availability in the water column in the development of phytoplankton biomass, and perform the mathematical modelling of changes in phosphorus and chlorophyll a concentrations in the Cruzeta man-made lake located on Serid?, a typical semi-arid region of Rio Grande do Norte. To this, a fortnightly monitoring was performed in the reservoir in 05 stations over the months of March 2007 to May 2008. Were measured the concentrations of total phosphorus, total organic nitrogen, chlorophyll a, total, fixed and volatile suspended solids, as well as the measure of transparency (Secchi) and the profiles of photosynthetic active radiation (PAR), temperature, pH, dissolved oxygen and electrical conductivity in the water column. Measurements of vertical profiles have shown some periods of chemical and thermal stratification, especially in the rainy season, due to increased water column depth, however, the reservoir can be classified as warm polimitic. During the study period the reservoir was characterized as eutrophic considering the concentrations of phosphorus and most of the time as mesotrophic, based on the concentrations of chlorophyll a, according to the Thornton & Rast (1993) classification. The N:P relations suggest N limitation, conversely, significant linear relationship between the algae biomass and nutrients (N and P) were not observed in our study. However, a relevant event was the negative and significant correlation presented by Kt and chlorophyll a (r ? = 0.83) at the end of the drought of 2007 and the rainy season of 2008, and the algal biomass collapse observed at the end of the drought season (Dec/07). The equation used to simulate the change in the total phosphorus was not satisfactory, being necessary inclusion of parameters able to increase the power of the model prediction. The chlorophyll a simulation presented a good adjustment trend, however there is a need to check the calibrated model parameters and subsequent equation validation / A eutrofiza??o tem se apresentado como um dos principais problemas de polui??o aqu?tica a n?vel global. No semi-?rido brasileiro este problema toma propor??es ainda maiores devido a escassez de ?gua caracter?stica da regi?o. Torna-se extremamente relevante para o desenvolvimento do modelos preditivos de eutrofiza??o e para a gest?o dos reservat?rios da regi?o semi-?rida, a realiza??o de estudos que propiciem a compreens?o dos mecanismos respons?veis pela expans?o e controle de flora??es de algas, fundamentais para a melhoria da qualidade da ?gua desses ambientes. Diante disso, o presente estudo teve como objetivos principais, avaliar o padr?o temporal do estado tr?fico, considerando a influ?ncia dos nutrientes (N e P) e a disponibilidade de luz na coluna d ?gua no desenvolvimento da biomassa fitoplanct?nica, e realizar a modelagem matem?tica da varia??o das concentra??es de f?sforo e clorofila a no a?ude Cruzeta localizado na regi?o do Serid?, regi?o t?pica do semi-?rido do Rio Grande do Norte. Para tanto, foi realizado o monitoramento do reservat?rio com amostragens de ?gua quinzenais em 05 pontos de coleta ao longo dos meses de mar?o de 2007 a maio de 2008, sendo determinadas as concentra??es de f?sforo total, nitrog?nio org?nico total, clorofila a, e s?lidos suspensos totais, fixos e vol?teis, al?m da medida de transpar?ncia (Secchi) e dos perfis de radia??o fotossinteticamente ativa (RFA), temperatura, pH, oxig?nio dissolvido e condutividade el?trica na coluna d ?gua. As medi??es dos perfis verticais realizados evidenciaram alguns per?odos de estratifica??o t?rmica e qu?mica, notadamente no per?odo chuvoso, devido a maior profundidade da coluna d ?gua, no entanto o reservat?rio pode ser classificado como pol?mitico quente. Durante o per?odo estudado o reservat?rio caracterizou-se como eutr?fico considerando-se as concentra??es de f?sforo e mesotr?fico na maior parte do tempo, com base nas concentra??es de clorofila a, segundo a classifica??o de Thornton & Rast (1993). As raz?es N:P observadas sugerem limita??o por N, opostamente, rela??es lineares significativas entre a biomassa de algas e os nutrientes (N e P) n?o foram observadas no nosso estudo. Entretanto, chamou aten??o a rela??o negativa e significativa apresentada pelo Kt e clorofila a (r?=0.83) no final do per?odo de estiagem de 2007 e per?odo chuvoso de 2008, e do colapso da biomassa algal observado no final do per?odo de estiagem (dez/07). A equa??o utilizada para simular a varia??o do f?sforo total n?o apresentou ajuste satisfat?rio, sendo necess?rio portanto, inser??o de par?metros capazes de elevar o poder de predi??o do modelo. A simula??o para clorofila a apresentou uma boa tend?ncia de ajuste, entretanto h? necessidade de verifica??o dos par?metros calibrados no modelo e posterior valida??o da equa??o