O papel dos recursos regulando a dominância de gêneros de cianobactérias em reservatórios do semiárido tropical

Abstract

Harmful cyanobacterial blooms have been long recognized as one of the most severe problems in freshwater systems. Recently, their frequency and duration have been increasing. This is the scenario for many semiarid reservoirs in Brazil that face persistent cyanobacterial blooms. The drivers regulating persistent cyanobacterial blooms are still poorly understood and comprehend them is crucial to the development of strategies to improve water quality. In light of this, we aim to elucidate the drivers of cyanobacteria dominance; evaluate the effect of drought and differ environmental preferences of Cylindrospermopsis raciborskii and Microcystis aeruginosa. We analysed chemical, physical and biological parameters from six reservoirs located in the semi-arid region from Brazil and created a “Cylinder abudance index” to access environmental preferences of the two most representatives species. Eutrophic semiarid reservoirs are more susceptible to persistent cyanobacteria bloom. Nitrogen and phosphorus favoured Cylindrospermopsis and Microcystis dominance, but light seems to be the factor regulating the switch between them. Drought negatively influenced total phosphorous and phytoplankton biomass. Our results suggest eutrophication in semiarid environments may lead to persistent dominance of cyanobacteria, still, other factors as physical could drive the temporal change of specie. Drought can potencialize persistent dominance due to interfere in the availability of resources.