Tuesday, May 27, 2008 - 10:00 AM
129

Comparison of the a priori typology-approach and RIVPACS-type models for status assessment of river invertebrate communities

Jukka Aroviita1, Heikki Mykrä2, Timo Muotka3, and Heikki Hämäläinen1. (1) Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FIN-40014 Jyväskylä University, Jyväskylä, Finland, (2) Research Programme for Integrated River Basin Management, Finnish Environment Institute, P.O. Box 413, FIN-90014 University of Oulu, Finland, (3) Department of Biology, University of Oulu, P.O. Box 3000, FIN-90014 University of Oulu, Finland, Finland

Predictive models are increasingly used and widely approved tools in freshwater bioassessment, but many assessment schemes like the European Union Water Framework Directive are largely based on a priori grouping of similar water bodies (typologies) to control for natural variation in biota. Thus there is a need to compare the assessment performances of predictive models and a priori typologies. We used data from 96 reference riffle sites and 134 impacted riffle sites from Western and Central Finland to compare RIVPACS-type models and a priori river typology (catchment size and geology) in assessing the status (Observed to Expected number of predicted taxa, O/E) of benthic invertebrate communities. We also examined the influence of geographical extent on assessment performance. The modeling-approach was more accurate than the typology-approach (reference mean O/E closer to 1). However, both approaches showed similar increase in precision (i.e., decrease in reference SD of O/E) from the corresponding null models and, especially at smaller geographical extent, similar sensitivity in detecting sites with potential human impairment. Our results confirm the greater efficiency of predictive models for bioassessment, but they indicate that the O/E-based typology-approach can also be useful, at least if applied within a restricted and relatively homogenous area.


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