BENTHIC MACROINVERTEBRATES AS BIOINDICATORS OF ENVIRONMENTAL QUALITY IN THREE STREAMS OF THE AMAMBAI RIVER BASIN, UPPER PARANÁ RIVER, BRAZIL

The objective of this study was to evaluate the environmental integrity of three streams (along 13 sampling sites) of the Upper Paraná River Basin using the benthic macroinvertebrate fauna as bioindicators and to answer the following question: Is there spatial variation, related to environmental quality, in the composition of these taxa in the streams? The invertebrates were sampled with a surber collector and for habitat analysis were determined characteristics as stream depth and width, water velocity, dissolved oxygen, pH, temperature, turbidity, and electrical conductivity. The environmental variables were analyzed by Principal Component Analysis in order to synthesize the data and identify the most important variables for ordering the collection sites. For biological analysis, the BMWP index was used. A Canonical Correlation Analysis of the environmental and biotic data was also performed in order to identify correlations between these two sets of variables. The collected macroinvertebrates belonged to four phyla (Nematoda, Annelida, Mollusca and Arthropoda), with Arthropoda being the most representative (54.93%), with the predominance of the order Diptera (30.29%). The most sensitive orders (Ephemeroptera, Plecoptera and Trichoptera) occurred in four sampling sites, corresponding to less impacted ones. Tolerant organisms, mainly chironomids, were found in all streams, including the most impacted places. These results indicate a spatial variation in the composition of the macroinvertebrates taxa in the streams, in response to variation of environmental quality.