Impact of mining and industrial pollution on stream macroinvertebrates : importance of taxonomic resolution, water geochemistry and EPT indices for impact detection

This study investigated freshwater macro invertebrate communities in waterways contaminated by active and abandoned mining and industrial activities in order to ascertain any impact on freshwater ecosystems. We compared macro invertebrate communities at the species, family and order levels of taxonomic resolution. We also collected water samples to compare ionic composition and metal concentrations from waste affected and reference (non-affected) sites. In addition to assessing ecological impairment, the study also sought to determine whether the degree of sensitivity in detecting any impairment varied according to the taxonomic level of identification used. We calculated the biotic indices of EPT richness and taxonomic richness at the species, family and order levels, and performed multivariate analyses to measure differences in community structure at all three levels. We found significant differences in both biotic indices and macro invertebrate community structure at each taxonomic level, indicating ecological impairment at waste affected sites. We also concluded that the most appropriate taxonomic level for evaluating macro invertebrates depends on the information required. In this study, the family level provided the clearest assessment of ecological impairment at waterways affected by mining and/or industrial wastes, and order-level data provided only a marginally less sensitive measure of this impairment.