The Use of the Benthic Community as a Water Quality Indicator in the Cubatão River Basin

A survey of the benthic macrofauna was performed along the rivers in the Cubatao region of Brazil to evaluate the aquatic environment. Twenty samples were collected in the Pereque, Cubatao, Moji, Piacaguera and Perdido rivers during Spring and Autumn, 1984. Two numerical indices, the Sequential Comparison Index (Cairns Jr. et at., 1968) and Biotic Index (Tuffery and Verneaux, 1968) were calculated using sample data. Density in each sample was determined for each taxonomic group. The index calculations showed that the environment is not in equilibrium at any of the sampling stations. Heavy organic pollution in Cubatao and Piacaguera rivers was indicated. In the Perdido river sediment was contaminated with tar. Pieces of insect larva, also present in the sediment, indicated impacts from toxic substances. At other sampling stations, the low numerical index values were related to the sediment nature (sandy in some stations) or to non-organic pollution which was evaluated using bioassays, Zagatto et al. (1986).