Kranswieren tussen wad en klif, Friesland

Six species of Charophyta were recorded in the province of Friesland, the Netherlands, in the years 1980-1982, during an ecological water quality research program. These species are Chara aspera, C. delicatula, ( C. globularis, C. vulgaris, Nilellaflexilis and N. mucronala. The distribution is presented in maps. They are investigated together with the other higher (water)plants. The occurrence of Charophyta was restricted to two water types, viz. ditches and peatdiggings. The assumed high biological monitoring value was not confirmed by the physico-chemical water quality data. Especially for the shallow Dutch waters further research is necessary on the potentially usefulness of (these) Charophyta as biological indicators of water quality.