EN
A biomonitoring program was developed to assess the ecological status of streams based on the phytobenthic algal community structure. The study presented here focuses on siliceous sites of streams in the central highlands of Germany. Phytobenthic algae belonging to eight classes and 74 taxa were grouped into four categories according to their ecological distribution pattern. A formula was designed to calculate an index ranging from +100 to ?100 to assess stream health. Based on these values, the sampling sites were assigned to one of the five ecological quality classes required by the Water Framework Directive (WFD) of the European Union.