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Data of Dissertation

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Author: Maria Isabel de Almeida Rocha.

Title: Evaluation of factors that contribute to the dominance of cyanobacteria in reservoir Funil and propose measures to improve water quality..

Year: 2012.    Full text (in Portuguese)

Abstract

The loss of environmental quality of the Funil Reservoir (Itatiaia, Rio de Janeiro) is a consequence of multiple human impacts that have occurred in the watershed of the Paraíba do Sul River, upstream of the reservoir. Cyanobacterial blooms are common and its dominance is frequent in this environment. This study aimed to evaluate, through field analyzes, which factors affect the cyanobacterial dominance in the reservoir. Also, laboratory studies were done to investigate the behavior of phytoplankton community under reduced nutrient concentrations. The past data of the Paraíba do Sul watershed showed a deficiency in livestock waste treatment and sanitation in some municipalities of Paraíba Valley as the main causative agents of water quality loss along the river and reservoir. The field analysis generated 6 samples in rainy and dry seasons between 2009 and 2010, at 11 sampling points along the river, upstream of the reservoir. In this last one there were 5 sampling points. In general, high concentrations of nutrients were found where the municipalities had little sewage treatment. From Jacareí city sampling point (PS-3), the results indicated an increase in conductivity, NID, orthophosphate and turbidity. The concentrations of dissolved oxygen and pH were quite high in the reservoir, because of cyanobacterial blooms. The analysis indicated high densities of phytoplankton in the river and the reservoir in summer months, being dominated by Cyanogranis ferruginea in the river and Dolychospermum spp. at reservoir. Sphaerocavum brasiliensis, Cylindrospermopsis raciborskii and Eucapsis sp. were more abundant in the months of higher temperature in the reservoir, when Microcystis spp. was in low density. High temperature associated with increased turbidity and rainfall promoted an increase in the density and richness of the zooplankton community. The experimental results showed that the community composition has been altered at the end of 30 days in all treatments. It is suggested that the replacement of a quarter of the water volume received by the Funil Reservoir with a better quality would be enough change to occur in the phytoplankton community, leading to a reduction in the occurrence of cyanobacterial blooms.

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