MEASURING THE IMPACT OF SEWAGE EFFLUENT ON THE MACROINVERTEBRATE COMMUNITY OF AN UPLAND STREAM - THE EFFECT OF DIFFERENT LEVELS OF TAXONOMIC RESOLUTION AND QUANTIFICATION

Benthic macroinvertebrates were sampled from four sites on upland stre ams in the Wentworth Falls area of the Blue Mountains, NSW. One site r eceived effluent from a sewage treatment plant and the others were ref erence sites. Five replicate collections were taken from each site on four occasions at intervals of 3 months. Macroinvertebrate community d ata were analysed using univariate (ANOVA) and multivariate (NMDS) tec hniques and comparisons were made between analyses at different levels of taxonomic aggregation and using different methods of data transfor mation Similar patterns were observed at both species and family level s, and even the order level showed a clear community response to efflu ent input. Binary (presence/absence) data provided similar results to quantitative data for the species and family levels. However, when bin ary data were used at the order level, the distinctions between the re ference sites became blurred. We discuss the implications of these fin dings for environmental monitoring.