The class Charetea includes vegetation of stoneworts (Charophyta), macrophytic green algae which form submerged stands attached to the bottom by rhizoids. Dominant species belong to the genera Chara, Nitella, Nitellopsis and Tolypella. Vegetation belonging to this class occurs mainly in shallow still water bodies, including periodically flooded habitats and man-made habitats such as fishponds, flooded quarries and sand pits. This vegetation type is most diverse in oligotrophic to mesotrophic water bodies. Although some species can grow in eutrophic water, eutrophication generally leads to the decline of stonewort communities, partly due to spread of competitively advantaged vascular plants. Stonewort vegetation is widespread in Eurasia and on other continents, but it is poorly studied. Available data from the Czech Republic are fragmentary, mainly owing to the difficulty of identifying stonewort species.