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Universidade Estadual da Paraíba (2019)

Fatores determinantes da ocorrência e abundância de cianobactérias e produção de cianotoxinas em ecossistemas do semiárido

Mendes, Camila Ferreira

Titre : Fatores determinantes da ocorrência e abundância de cianobactérias e produção de cianotoxinas em ecossistemas do semiárido

Auteur : Mendes, Camila Ferreira

Université de soutenance : Universidade Estadual da Paraíba

Grade : Doutora em Engenharia Ambiental. 2019

Résumé partiel
Cyanobacteria are prokaryotes, which perform photosynthesis, present in the most diverse types of environments, being able to survive under a range of different environmental conditions. However, some conditions such as high temperatures, high concentrations of nutrients, can favor their development in such a way that they even form blooms, bringing negative consequences for both the system and implications for public health and economic order. Trying to better understand the dynamics of cyanobacteria in semiarid ecosystems, this doctoral work is divided into two chapters. The first one is entitled : Effects of water volume reduction on cyanobacteria and cyanotoxins in semiarid reservoirs impacted by severe drought. In this chapter, the objective was to evaluate the effects of water volume reduction on the composition and abundance of cyanobacteria and the concentration of cyanotoxins in semiarid reservoirs impacted by severe drought. Seven samples were collected in three reservoirs from the Paraíba River Basin (Acauã, Boqueirão and Camalaú) between July 2015 and February 2017. In situ data were collected (transparency, water temperature, pH, electrical conductivity, turbidity, (N-NH4), Nitrite (N-NH3), total nitrogen (TN), soluble reactive phosphorus (SRP), and total dissolved solids, dissolved oxygen and salinity and total phosphorus (PT)), cyanobacteria and cyanotoxins (total microcystins, total saxitoxins and total cylindrospermopsins). The reduction of the water volume modified the physical and chemical characteristics of the reservoirs and consequently the composition and biomass of cyanobacteria. The water temperature in the reservoirs varied around 25ºC, the pH was alkaline and the nutrient concentration was high, with a low total and dissolved N/P ratio. In the regression analysis, the water volume appears as a common variable to the three reservoirs causing negative and positive effects on the biomass of cyanobacteria. For the Acauã and Camaláu reservoirs an inverse relationship is observed and for the Boqueirão reservoir a direct effect, thus, in the first two systems there was increase of the biomass and in the third one a decrease. The Boqueirão and Camalaú reservoirs presented changes in the composition of the species, but for the three systems, we highlight filamentous species such as Cylindrospermopsis raciborskii and Dolichospermum solitarium.

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