Fatores que influenciam na dominância e das variações morfológicas de populações de Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju e Planktothrix agardhii (Gomont) Anagnostidis and Komárek, em reservatórios localizados no trópico semiárido - Nordeste do Brasil

Abstract

Northeast of Brazil reservoirs have a high degree of eutrophication, due to its multiple uses, and are characterized by high concentrations of phosphorus and nitrogen, low transparency and low annual amplitude of temperature. In this scenario, blooms of cyanobacteria are constant and are characterized mainly by high densities of Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju and Planktothrix agardhii Komárek, recognized by algae produce toxic substances that can cause serious liver disorders. The objective of this study was to determine the environmental factors (hydrological and climatological) controlling the populations of these two species in reservoirs located in the northeast of Brazil, through the identification of morphological variations, morphometric and biomass of populations in annual, spatial and vertical scale. The research was based on Diel and bimonthly collection held with van Dorn bottle, at various points (littoral and limnetic region) of Carpina reservoir (Pernambuco state) and Acauã (State of Paraíba). Samples were collected at three depths in accordance with the penetration of light: 100% brightness, 50% and maximum depth, followed by the rainfall cycle of the regions, so are characterized with distinction variations of the two populations in an annual cycle . The biological variables (morphology, density, biovolume and biomass) were correlated with environmental variables (air temperature, precipitation, dissolved oxygen, water temperature, turbidity, pH and nutrients: nitrite, nitrate, total phosphorus and dissolved orthophosphate). The research resulted in the development of two articles. In the first (Manuscript I) evaluates the co-occurrence of the two species face the environmental characteristics, especially in relation to individual environmental performance, including morphological and biomass in response to environmental conditions. The second article (MS II) was made a correlation between environmental factors and biomass and the morphology of P. agardhii Acauã the reservoir (Paraiba), in order to determine the factors controlling the variations Diel species. This study is expected to contribute to the knowledge of cyanobacterial ecology occurring in the Northeast supply reservoirs and characterize the species mentioned as descriptors, able to identify the environmental quality of supply reservoirs in the semi-arid northeast.