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Ocorrência de uma floração de cianobactérias tóxicas na margem direita do Rio Tapajós, no Município de Santarém (Pará, Brasil)

2010; Volume: 1; Issue: 1 Linguagem: Inglês

10.5123/s2176-62232010000100022

2176-6223

Lena Líllian Canto de Sá, José Maria dos Santos Vieira, Rosivaldo de Alcântara Mendes, Samara Cristina Campelo Pinheiro, Elivam Rodrigues Vale, Francisco Arimatéia dos Santos Alves, Iracina Maura de Jesus, Elisabeth Conceição de Oliveira Santos, Vanessa Bandeira da Costa,

Aquatic Ecosystems and Phytoplankton Dynamics

The presence of cyanobacterial blooms and their subproducts interferes directly in water quality and may cause negative effects, both aesthetically and to public health, due to the production of potentially toxic and carcinogenic compounds.The most common type of intoxication involving cyanobacteria is caused by microcystin-LR (hepatotoxin), which can cause severe damage to the liver.The objective of this study was to identify the genera that caused cyanobacterial blooms in the Tapajós river (Santarém, Pará, Brazil) in March 2007, as well as to execute acute toxicity bioassays in Swiss-webster mice.Sample collection was performed at five sampling points throughout the left margin of the Tapajós river, by horizontal dragging with the aid of a 20 µm plankton net.Samples of raw water (5,000 ml) were also collected in amber propylene bottles.Optical microscopy was applied to identify the organisms, and the determination of microcystin-LR was executed through ELISA and HPLC.The analyses showed that, at P01 and P02, there was an ecological imbalance in the phytoplanktonic community, characterized by an intense proliferation of the genera Anabaena and Microcystis.The concentrations of microcystin-LR reported in the raw water samples were below the maximum values permitted by Brazil's legislation for drinking water.However, it is important to note that the blooming observed in loco occupied around 10 cm of the water column surface and therefore presented cyanobacterial cells enough to cause rashes in people who swam or bathed in the rivers during this period.