Using Taxon-Environment Relationships for Defining Macroinvertebrate Reference Communities in Disturbed Areas

The pervasive modification of river systems by humans has created a need for assessment methods that determine site-specific reference communities across such landscapes. Where the composition of taxa under undisturbed conditions (reference condition communities) can be determined for a site, the site may then be assessed by comparing the observed community with the expected community. Macroinvertebrate training data from south east Australia were used to develop regression models for the distribution of macroinvertebrate taxa associated with large-scale variables (robust to human activity) and mutable variables as candidate predictors. Natural values of the mutable variables were also predicted with process-based models such as those used for predicting sediment and nutrient loads. The regression models for taxa distributions then allow predictions to reconstruct reference condition communities by substituting process model estimates of natural values of mutable variables in place of the observed values. The predicted distribution of taxa based on estimated natural values of mutable variables can be used for biotic assessment of site condition or can be incorporated into other reference condition bioassessment approaches. The method has been tested initially in areas where reference sites are available and subsequently it is intended extended to areas with few, if any, reference sites.