Cyanobacteria in sewage treatment ponds in semi-arid northeast (Ceará, Brazil)

Abstract

The stabilization ponds are an eutrophic environment, characterized by the excessive phytoplankton growth, where the most common group is Cyanobacteria and this constitute the aim focuses in this research. The cyanobacteria Planktothrix sp. is important in blooms in the Brazilian environment due to their wide distribution, capacity to produce toxins and effects that they can cause in other organisms. The samples were collected monthly in the final of the facultative and maturation ponds of the Station of Treatment of Sewer, in Juazeiro city (7°13'08"S and 39°19'12"W), Northeast of Brazil, taking up two years, during four months of each station: August to November to 2005 at 2007 (dry station) and February to May to 2006 at 2008 (rainy station). These samples were divided in two subsamples for analysis in vivo and fixed in formol to 4% for subsequent analyses. The cyanobacteria P. isothrix was the most important species, considered dominant in both periods. Thus, indexes of specific diversity and equitability showed a distribution non uniform of the phytoplankton community. Based on the species composition with reports in the production of the metabolic toxic to the man and the environment it should be relevant to the environmental impact because the biomass release of these organisms in the water bodies promotes the eutrophycation increase as of the potential toxin of the water.