A practical and sensitive approach to large river periphyton monitoring : comparative performance of methods and taxonomic levels

The reliability and sensitivity of two periphyton monitoring methods were assessed in the large boreal Kymi River. First, results from 11 years of monitoring of periphyton biomass on artificial substrates, expressed as chlorophyll a, were analysed. Second, in a one-year survey, the sensitivity of periphyton biomass was compared with the analysis of epilithic diatom community structure. Finally, diatom community analysis using three practical approaches based on different taxonomic resolutions was tested. The long-term monitoring results of periphyton biomass revealed significant differences among the sites and years. Although long-term results showed significant correlation in the annual nutrient concentrations and periphyton biomass, the diatom indices demonstrated a higher sensitivity to changes in water quality. Analysis of concordance showed that diatom community analysis based on generic level alone, or specifically combined with the identification of only the abundant species, could offer a practical and reliable biomonitoring tool for large rivers.