Littoral diatom assemblages as bioindicators of lake trophic status: A case study from perialpine lakes in Austria

Abstract

Littoral diatom assemblages from different natural substrates (stones, mud, reeds) were used for estimating trophic status in seven perialpine lakes near Salzburg (Austria). Four trophic status indices were compared with the actual chemical data and the annual averages of total phosphorus concentrations. Diatom assemblages on different substrates indicated significantly different trophic status for the site. Indicators based on epiphytic diatoms from young reed stalks correlated strongly with the concentrations of total phosphorus, so that reeds were found to be the most suitable substrate for bioindication. Bioindication based on three of the four indices studied (Rott's TDIA, Schönfelder's TS, van Dam's TDW) was positively correlated with actual phosphorus concentration at each site. While other indices indicated higher trophic status than expected according to annual averages of total phosphorus, Rott's TDIA was found to be the most applicable to perialpine lakes.