Diatoms as Indicators of Organic Pollution

There is given a list of 323 taxa of freshwater diatoms occurring in waters of Central Europe. Each taxon is characterized by 10 balls of saprobic valence, the indicative weight of species (I_i) and by the individual saprobic index (S_i) indicating its position on a conventional scale of saprobity. Diatoms are very common aquatic organisms, but are only medium or bad indicators of saprobity, because their saprobic valence is usually wide.