REGIONAL REPRESENTATIVENESS OF SWEDISH REFERENCE LAKES

Recent focus has been placed on ecoregion delineations for providing a n appropriate framework for monitoring and assessment of region-specif ic attainable water/habitat quality. Using an ecoregion approach to st ratify variance, this study was conducted to determine whether earlier (subjectively) selected Swedish reference lakes may be considered as regionally representative reference sites when compared with a randoml y selected lake population. Predictive modeling by discriminant functi on analysis with lakes classified by ecoregion and lake surface area a nd six physicochemical variables showed that the greater majority of r eference lakes may be considered as regionally representative. The hig hest proportion of lake ''misclassifications'' occurred in the boreone moral ecoregion, a relatively diverse ecoregion of southern Sweden. Th is apparent bias may be in part be due to the criteria used in selecti ng regional reference lakes. In the earlier selection of reference lak es emphasis was placed on lakes not being adversely affected by land u sage or pollutant discharges, consequently forest lakes were often ove rrepresented and sites in agricultural areas underrepresented in the s elected reference sites. As a complement to predictive modeling, PCA o rdination showed the placement of reference lakes within the random la ke population and indicated where reference sites might be missing alo ng potentially important ecological gradients.