ASSESSING THE ECOLOGICAL QUALITY OF SWEDISH STREAMS USING A MULTIMETRIC MACROINVERTEBRATE INDEX.

J. Dahl, L. Sandin, and R.K. Johnson. Department of Environmental Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden

AQEM is a EU-financed research project focused on developing and testing an assessment procedure for streams and rivers using benthic macroinvertebrates. Eight countries are involved in the project, with sampling sites ranging from the alpine and boreal forests of northern Europe (Sweden) to the Mediterranean regions in the south (e.g. Greece, Italy and Portugal). In Sweden, five stream types, situated in three major ecoregions, were classified by catchment area size, altitude and degree of degradation (organic pollution and acidic stress). A number of metrics were tested for assessing organic pollution effects in southern Sweden. Subsequently, two metrics were used, namely the Average Score Per Taxon (ASPT) and the Danish Stream Fauna Index (DSFI). Both metrics combined explained 48% of the variability along the degradation gradient. In developing an assessment procedure for acidified streams in northern Sweden, several of the metrics tested were shown to be useful for detecting site-specific conditions. However, for assessing general regional patterns only two metrics (the number of mayfly taxa and an acid index) were consistently correlated to the acid-stress gradient. These two metrics singly or combined with one other metric were able to explain 25% to 82% of the variance associated with acid stress.