Use of benthic macroinvertebrates to assess the biological status of Pampean streams in Argentina

Abstract

Macro-invertebrate communities and environmental variables were assessed seasonally for two years in sevenstreams in North-Eastern of Buenos Aires province (Argentina) in order to analyse changes in their structure andcomposition in relation with the quality of the water. The study includes pristine streams and others affectedby urban and industrial effluents with high conductivity, nitrates, nitrites, phosphates and low oxygen content.Organisms with well-known pollution tolerance were identified to assess biological water quality, using a newBiotic Index (IBPAMP:BioticIndex forPAMPean rivers and streams) in comparison with other existing bioticindices. The usefulness of principal component analysis (PCA) and correlation matrices were examined to evaluatethe efficiency of the method to assess disturbances. In general IBPAMP did well correlate with several classicalmeasures of biological water quality (taxon richness, diversity and several biotic indices). The El Gato stream wasthe most disturbed ecosystem among all studied sites. It was characterised by low dissolved oxygen levels, highturbidity in the middle course, high BOD5 (>30 mg l−1)andCOD(>40 mg l−1) values. The Buñirigo stream hasa bad quality in the industrial area, but varying according to the dry and wet periods. In general, in the mountainousareas the water quality of streams was good with the exception of the stations located downstream of cities likeAyacucho on the Tandileofú stream.